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Sample records for phytoplankton dose-effect relationship

  1. Chronic uranium exposure and growth toxicity for phytoplankton. Dose-effect relationship: first comparison of chemical and radiological toxicity

    International Nuclear Information System (INIS)

    Gilbin, R.; Pradines, C.; Garnier-Laplace, J.

    2004-01-01

    The bioavailability of uranium for freshwater organisms, as for other dissolved metals, is closely linked to chemical speciation in solution (U aqueous speciation undergoes tremendous changes in the presence of ligands commonly found in natural waters e.g. carbonate, phosphate, hydroxide and natural organic matter). For the studied chemical domain, short-term uranium uptake experiments have already shown that the free uranyl ion concentration [UO 2 2+ ] is a good predictor of uranium uptake by the green algae Chlamydomonas reinhardtii, as predicted by the Free Ion Activity Model. In agreement with these results, acidic pH and low ligands concentrations in water enhance uranium bioavailability and consequently its potential chronic effects on phytoplankton. Moreover, uranium is known to be both radio-toxic and chemo-toxic. The use of different isotopes of uranium allows to expose organisms to different radiological doses for the same molar concentration: e.g. for a given element concentration (chemical dose), replacing depleted U by U-233 obviously leads to an enhanced radiological delivered dose to organisms (x10 4 ). In this work we established relationships between uranium doses (depleted uranium and 233-U ) and effect on the growth rate of the green algae Chlamydomonas reinhardtii. Uranium bioaccumulation was also monitored. Growth rate was measured both in classical batch (0-72 hrs) and continuous (turbidostat) cultures, the latter protocol allowing medium renewal to diminish exudates accumulation and speciation changes in the medium. The differences in effects will be, if possible, related to the development of defence mechanisms against the formation of reactive oxygen species (forms of glutathione) and the production of phyto-chelatins (small peptides rich in cystein that play an important role in the homeostasis and the detoxication of metals in cells). (author)

  2. Plutonium dose-effect relationship

    International Nuclear Information System (INIS)

    Matsuoka, Osamu

    1976-01-01

    Dose in internal exposure to Pu was investigated, and dose-effect relationship was discussed. Dose-effect relationship in internal exposure was investigated by means of two methods, which were relationship between dose and its effect (relationship between μ Ci/Kg and its effect), and exposure dose and its effects (rad-effect), and merits and demerits of two methods were mentioned. Problems in a indication method such as mean dose were discussed with respect to the dose in skeleton, the liver and the lung. Pu-induced osteosarcoma in mice rats, and beagles was described, and differences in its induction between animals were discussed. Pulmonary neoplasma induced by 239 PuO 2 inhalation in beagles was reported, and description was made as to differences in induction of lung cancer between animals when Pu was inhaled and was taken into the lung. A theoretical and experimental study of a extrapolation of the results of the animal experiment using Pu to human cases is necessary. (Serizawa, K.)

  3. Topics on study of low dose-effect relationship

    International Nuclear Information System (INIS)

    Yamada, Takeshi; Ohyama, Harumi

    1999-01-01

    It is not exceptional but usually observed that a dose-effect relationship in biosystem is not linear. Sometimes, the low dose-effect relationship appears entirely contrary to the expectation from high dose-effect. This is called a 'hormesis' phenomena. A high dose irradiation inflicts certainly an injury on biosystem. No matter how low the dose may be, an irradiation might inflict some injury on biosystem according to Linear Non-Threshold hypothesis(LNT). On the contrary to the expectation, a low dose irradiation stimulates immune system, and promotes cell proliferation. This is called 'radiation hormesis'. The studies of the radiation hormesis are made on from four points of view as follows: (1) radiation adaptive response, (2) revitalization caused by a low dose stimulation, (3) a low dose response unexpected from the LNT hypothesis, (4) negation of the LNT hypothesis. The various empirical proofs of radiation hormesis are introduced in the report. (M . Suetake)

  4. Topics on study of low dose-effect relationship

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Takeshi [Toho Univ., School of Medicine, Tokyo (Japan); Ohyama, Harumi

    1999-09-01

    It is not exceptional but usually observed that a dose-effect relationship in biosystem is not linear. Sometimes, the low dose-effect relationship appears entirely contrary to the expectation from high dose-effect. This is called a 'hormesis' phenomena. A high dose irradiation inflicts certainly an injury on biosystem. No matter how low the dose may be, an irradiation might inflict some injury on biosystem according to Linear Non-Threshold hypothesis(LNT). On the contrary to the expectation, a low dose irradiation stimulates immune system, and promotes cell proliferation. This is called 'radiation hormesis'. The studies of the radiation hormesis are made on from four points of view as follows: (1) radiation adaptive response, (2) revitalization caused by a low dose stimulation, (3) a low dose response unexpected from the LNT hypothesis, (4) negation of the LNT hypothesis. The various empirical proofs of radiation hormesis are introduced in the report. (M . Suetake)

  5. Awortwi et al.: Mixing and stratification relationship on phytoplankton ...

    African Journals Online (AJOL)

    Awortwi et al.: Mixing and stratification relationship on phytoplankton of Lake Bosomtwe (Ghana) 43 West African Journal of Applied Ecology, vol. 23(2), 2015: 43–62. The Relationship Between Mixing and Stratification Regime on the Phytoplankton of Lake Bo.

  6. UV dose-effect relationships and current protection exposure standards

    International Nuclear Information System (INIS)

    Singh, M.S.; Campbell, G.W.

    1982-04-01

    In this paper we have attempted to quantify the health effects in man of uv-radiation exposure of wavelengths from 240 nm to 320 nm. Exposure to uv in this region could result in the formation of skin cancer or premature aging in man. The induction of cancer by uv radiation results from changes in genetic material. We have used the DNA action spectrum coupled with the uv skin cancer data available in the literature to derive the dose-effect relationships. The results are compared against the current uv protection standards

  7. The biological bases of the dose-effect relationship

    International Nuclear Information System (INIS)

    Lafuma, J.

    2001-01-01

    In radiation protection, the recent data in epidemiology, in animal experimentation and on the base researches are no more compatible with a linear dose-effect relationship without threshold and do not account for the radiological risks at low doses. The cancers should be accelerated by radiations as any pathology linked to the ageing and for which threshold exit. Relative to the genetic risk it is known today that the natural exposure that lasts for several generations has not lead excess of hereditary illness as it was to be feared in 1959 for several countries. Considering that for populations the exposure levels induced by human activities have already been, under these ones of average natural exposures the genetic risk can be negligible and it is the somatic risk alone, with its thresholds that has to be into account. (N.C.)

  8. Dose-effect relationships for the US radium dial painters

    International Nuclear Information System (INIS)

    Thomas, R.G.

    1995-01-01

    Dose-response data are presented from a large percentage of the US workers who were exposed to radium through the painting of luminous dials. The data in this paper are only from females, because very few males worked in this occupation. Log-normal analyses were done for radium-induced bone sarcomas and head carcinomas after the populations of the respective doses were first determined to be log-normally distributed. These populations included luminisers who expressed no radium-related cancerous condition. In this study of the female radium luminisers, the most important data concerning radiation protection are probably from workers who were exposed to radium but showed no cancer incidence. A total of 1391 subjects with average measured skeletal doses below 10 Gy are in this category. A primary purpose is to illustrate the strong case that 226,228 Ra is representative of those radionuclides that exemplify in humans a 'threshold' dose, a dose below which there has been no observed health effects on the exposed individual. Application of a threshold dose for radium deposited in the skeleton does not mean to imply that any other source of skeletal irradiation should be considered to follow a similar pattern. Second, a policy issue that begs for attention is the economic consequence of forcing radiation to appear as a highly toxic insult. It is time to evaluate the data objectively instead of formatting the extrapolation scheme beforehand and forcing the data to fit a preconceived pattern such as linearity through the dose-effect origin. In addition, it is time to re-evaluate (again) variations in background radiation levels throughout the world and to cease being concerned with, and regulating against, miniscule doses for which no biomedical effects on humans have ever been satisfactorily identified or quantified. (author)

  9. A review of in vitro dose-effect relationships

    International Nuclear Information System (INIS)

    Dolphin, G.W.

    1978-01-01

    One of the principal reasons for investigating the relationship between absorbed dose and the number of chromosome aberrations per cell in lymphocytes taken from samples of human peripheral blood is to obtain a calibration curve for biological dosimetry. Factors affecting the radiation-induced aberration yield in vitro of T lymphocytes are reviewed under the following heads: temperature, oxygen effect, inter-mitotic death, mitotic delay, dose rate background of aberrations in normal humans, mathematical representation. (U.K.)

  10. Empirical relationships between phytoplankton and zooplankton biomass in Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Jayalakshmy, K.V.

    and temperature, zooplankton and phytoplankton, zooplankton and PO sub(4)-P and phytoplankton and PO sub(4)-P. Linear regression model is found to be significant at 1% level of significance. Since zooplankton and phytoplankton are significantly positively...

  11. A system of dose-effects relationships for the Northern wildlife: radiation protection criteria

    International Nuclear Information System (INIS)

    Sazykina, T.G.

    2004-01-01

    The key issue in the assessment system for radiation protection of wildlife is the establishment of a set of dose-effects relationships for reference representatives of natural biota, based on scientific data from a range of doses and a range of radiation effects. Risks to natural populations in particular habitats can be evaluated from a comparison of estimated doses to biota with the scale of dose-effects relationships for different types of biota. Within the frame of the EC Project EPIC 'Environmental Protection from Ionizing Contaminants' 2000-2003), a database has been created, which include the published and unpublished data relating to dose effects relationships for flora and fauna in the Northern and Arctic areas. The EPIC database contains information based exclusively on Russian/FSU experimental and field studies; chronic/lifetime exposures were the focus of the work, owing to the fact that such exposures are the most typical in radiological assessments for biota. In total, the EPIC database radiation effects on biota contains about 1600 records from 440 publications, including datasets on terrestrial and aquatic animals, plants, soil fauna and microorganisms. The EPIC database information cover a very wide range of radiation dose rates to wild flora and fauna: from below 10 -5 Gy d -1 up to more than 1 Gy d -1 . A great variety of radiation effects are registered in the EPIC database, from stimulation at low doses up to death from acute radiation syndrome at high doses. From data, compiled in the EPIC database, the dose-effects relationships were derived for different types of northern organisms. The system of dose-effects relationships forms the scale of severity of radiation effects at increasing levels of chronic radiation exposure. With its focus on the effects of low-to-moderate chronic exposure, the system of dose effects relationships provides a useful tool for scientists and decision-makers to establish safety standards for protecting the

  12. Dose-Effect Relationship in Chemoradiotherapy for Locally Advanced Rectal Cancer

    DEFF Research Database (Denmark)

    Jakobsen, Anders; Ploen, John; Vuong, Té

    2012-01-01

    PURPOSE: Locally advanced rectal cancer represents a major therapeutic challenge. Preoperative chemoradiation therapy is considered standard, but little is known about the dose-effect relationship. The present study represents a dose-escalation phase III trial comparing 2 doses of radiation...

  13. Dose-effect relationships for individual pelvic floor muscles and anorectal complaints after prostate radiotherapy.

    NARCIS (Netherlands)

    Smeenk, R.J.; Hoffmann, A.L.; Hopman, W.P.M.; Lin, E.N.J.T. van; Kaanders, J.H.A.M.

    2012-01-01

    PURPOSE: To delineate the individual pelvic floor muscles considered to be involved in anorectal toxicity and to investigate dose-effect relationships for fecal incontinence-related complaints after prostate radiotherapy (RT). METHODS AND MATERIALS: In 48 patients treated for localized prostate

  14. On the linearity of the dose-effect relationship of DNA double strand breaks

    International Nuclear Information System (INIS)

    Chadwick, K.H.; Leenhouts, H.P.

    1994-01-01

    Most radiation biologists believe that DNA double-strand breaks are induced linearly with radiation dose for all types of radiation. Since 1985, with the advent of elution and gel electrophoresis techniques which permit the measurement of DNA double-strand breaks induced in mammalian cells at doses having radiobiological relevance, the true nature of the dose-effect relationship has been brought into some doubt. Many investigators measured curvilinear dose-effect relationships and a few found good correlations between the induction of the DNA double-strand breaks and cell survival. We approach the problem pragmatically by assuming that the induction of DNA double-strand breaks by 125 I Auger electron emitters incorporated into the DNA of the cells is a linear function of the number of 125 I decays, and by comparing the dose-effect relationship for sparsely ionizing radiation against this standard. The conclusion drawn that the curvilinear dose-effect relationships and the correlations with survival are real. (Author)

  15. Dose-Effect Relationships for Individual Pelvic Floor Muscles and Anorectal Complaints After Prostate Radiotherapy

    International Nuclear Information System (INIS)

    Smeenk, Robert Jan; Hoffmann, Aswin L.; Hopman, Wim P.M.; Lin, Emile N.J. Th. van; Kaanders, Johannes H.A.M.

    2012-01-01

    Purpose: To delineate the individual pelvic floor muscles considered to be involved in anorectal toxicity and to investigate dose-effect relationships for fecal incontinence-related complaints after prostate radiotherapy (RT). Methods and Materials: In 48 patients treated for localized prostate cancer, the internal anal sphincter (IAS) muscle, the external anal sphincter (EAS) muscle, the puborectalis muscle (PRM), and the levator ani muscles (LAM) in addition to the anal wall (Awall) and rectal wall (Rwall) were retrospectively delineated on planning computed tomography scans. Dose parameters were obtained and compared between patients with and without fecal urgency, incontinence, and frequency. Dose-effect curves were constructed. Finally, the effect of an endorectal balloon, which was applied in 28 patients, was investigated. Results: The total volume of the pelvic floor muscles together was about three times that of the Awall. The PRM was exposed to the highest RT dose, whereas the EAS received the lowest dose. Several anal and rectal dose parameters, as well as doses to all separate pelvic floor muscles, were associated with urgency, while incontinence was associated mainly with doses to the EAS and PRM. Based on the dose-effect curves, the following constraints regarding mean doses could be deduced to reduce the risk of urgency: ≤30 Gy to the IAS; ≤10 Gy to the EAS; ≤50 Gy to the PRM; and ≤40 Gy to the LAM. No dose-effect relationships for frequency were observed. Patients treated with an endorectal balloon reported significantly less urgency and incontinence, while their treatment plans showed significantly lower doses to the Awall, Rwall, and all pelvic floor muscles. Conclusions: Incontinence-related complaints show specific dose-effect relationships to individual pelvic floor muscles. Dose constraints for each muscle can be identified for RT planning. When only the Awall is delineated, substantial components of the continence apparatus are

  16. Dose-effect relationships for individual pelvic floor muscles and anorectal complaints after prostate radiotherapy.

    Science.gov (United States)

    Smeenk, Robert Jan; Hoffmann, Aswin L; Hopman, Wim P M; van Lin, Emile N J Th; Kaanders, Johannes H A M

    2012-06-01

    To delineate the individual pelvic floor muscles considered to be involved in anorectal toxicity and to investigate dose-effect relationships for fecal incontinence-related complaints after prostate radiotherapy (RT). In 48 patients treated for localized prostate cancer, the internal anal sphincter (IAS) muscle, the external anal sphincter (EAS) muscle, the puborectalis muscle (PRM), and the levator ani muscles (LAM) in addition to the anal wall (Awall) and rectal wall (Rwall) were retrospectively delineated on planning computed tomography scans. Dose parameters were obtained and compared between patients with and without fecal urgency, incontinence, and frequency. Dose-effect curves were constructed. Finally, the effect of an endorectal balloon, which was applied in 28 patients, was investigated. The total volume of the pelvic floor muscles together was about three times that of the Awall. The PRM was exposed to the highest RT dose, whereas the EAS received the lowest dose. Several anal and rectal dose parameters, as well as doses to all separate pelvic floor muscles, were associated with urgency, while incontinence was associated mainly with doses to the EAS and PRM. Based on the dose-effect curves, the following constraints regarding mean doses could be deduced to reduce the risk of urgency: ≤ 30 Gy to the IAS; ≤ 10 Gy to the EAS; ≤ 50 Gy to the PRM; and ≤ 40 Gy to the LAM. No dose-effect relationships for frequency were observed. Patients treated with an endorectal balloon reported significantly less urgency and incontinence, while their treatment plans showed significantly lower doses to the Awall, Rwall, and all pelvic floor muscles. Incontinence-related complaints show specific dose-effect relationships to individual pelvic floor muscles. Dose constraints for each muscle can be identified for RT planning. When only the Awall is delineated, substantial components of the continence apparatus are excluded. Copyright © 2012 Elsevier Inc. All rights

  17. Study of the dose-effect relationship of γ-H2AX radiation

    International Nuclear Information System (INIS)

    Cui Shuangshuang; Fan Yaguang; Gun Zhijuan; Wang Jixian; Zhao Yongcheng; Sun Yuping

    2010-01-01

    Objective: By using laser scanning confocal microscopy (LSCM) to test the dose-effects relationship between ionizing radiation intensity and quantity of the γ-H2AX in vivo and in vitro respectively, and the consistency relationship between the vivo and vitro retrial. Methods: To irradiate the peripheral blood from Wister female rats by 137 Cs at 7 with different doses (0, 0.5, 1, 2, 2.54, 4, 6, 8 Gy) extract the lymphocytes from the peripheral blood and detect the dose-effects relationship between irradiation intensity and number of γ-H2AX foci. Results: There are good dose-effects relationships between the irradiation and foci number both in vivo and in vitro, which are linear, Y vivo =0.096+0.13X; Y vitro =0.040+0.21X. And there is good consistency (R=0.98) between the γ-H2AX in vivo and in vitro. Conclusions: γ-H2AX has the possibility for clinical trial as an indicator, and we can use vitro trials in place of the vivo trails to evaluate the dose people received. (authors)

  18. Epidemiological methods for assessing dose-response and dose-effect relationships

    DEFF Research Database (Denmark)

    Kjellström, Tord; Grandjean, Philippe

    2007-01-01

    Selected Molecular Mechanisms of Metal Toxicity and Carcinogenicity General Considerations of Dose-Effect and Dose-Response Relationships Interactions in Metal Toxicology Epidemiological Methods for Assessing Dose-Response and Dose-Effect Relationships Essential Metals: Assessing Risks from Deficiency......Description Handbook of the Toxicology of Metals is the standard reference work for physicians, toxicologists and engineers in the field of environmental and occupational health. This new edition is a comprehensive review of the effects on biological systems from metallic elements...... access to a broad range of basic toxicological data and also gives a general introduction to the toxicology of metallic compounds. Audience Toxicologists, physicians, and engineers in the fields of environmental and occupational health as well as libraries in these disciplines. Will also be a useful...

  19. Size Class Dependent Relationships between Temperature and Phytoplankton Photosynthesis-Irradiance Parameters in the Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    Alex Robinson

    2018-01-01

    Full Text Available Over the past decade, a number of methods have been developed to estimate size-class primary production from either in situ phytoplankton pigment data or remotely-sensed data. In this context, the first objective of this study was to compare two methods of estimating size class specific (micro-, nano-, and pico-phytoplankton photosynthesis-irradiance (PE parameters from pigment data. The second objective was to analyse the relationship between environmental variables (temperature, nitrate and PAR and PE parameters in the different size-classes. A large dataset was used of simultaneous measurements of the PE parameters (n = 1,260 and phytoplankton pigment markers (n = 2,326, from 3 different institutes. There were no significant differences in mean PE parameters of the different size classes between the chemotaxonomic method of Uitz et al. (2008 and the pigment markers and carbon-to-Chl a ratios method of Sathyendranath et al. (2009. For both methods, mean maximum photosynthetic rates (PmB for micro-phytoplankton were significantly lower than those for pico-phytoplankton and nano-phytoplankton. The mean light limited slope (αB for nano-phytoplankton were significantly higher than for the other size taxa. For micro-phytoplankton dominated samples identified using the Sathyendranath et al. (2009 method, both PmB and αB exhibited a significant, positive linear relationship with temperature, whereas for pico-phytoplankton the correlation with temperature was negative. Nano-phytoplankton dominated samples showed a positive correlation between PmB and temperature, whereas for αB and the light saturation parameter (Ek the correlations were not significant. For the Uitz et al. (2008 method, only micro-phytoplankton PmB, pico-phytoplankton αB, nano- and pico-phytoplankton Ek exhibited significant relationships with temperature. The temperature ranges occupied by the size classes derived using these methods differed. The Uitz et al. (2008 method

  20. Relationships between Concentrations of Phytoplankton Chlorophyll a and Total Nitrogen in Ten U.S. Estuaries

    Science.gov (United States)

    This presentation focuses on the summertime response of phytoplankton chlorophyll to nitrogen concentrations in the upper water columns of ten U.S. estuaries. Using publicly available data from monitoring programs, regression relationships have been developed between summer surfa...

  1. [Electroconvulsive therapy and level of evidence: From causality to dose-effect relationship].

    Science.gov (United States)

    Micoulaud-Franchi, J-A; Quilès, C; Cermolacce, M; Belzeaux, R; Adida, M; Fakra, E; Azorin, J-M

    2016-12-01

    The first objective of this article is to summarize the history of electroconvulsive therapy (ECT) in psychiatry in order to highlight the transition from clinical level of evidence based on phenomenological descriptions to controlled trial establishing causal relationship. The second objective is to apply the criteria of causation for ECT, to focus on the dose-effect relationship criteria, and thus to analyze the conditions of application of these criteria for ECT. A literature review exploring the use of electricity, ECT and electroencephalography (EEG) in psychiatry was conducted. The publications were identified from the Pubmed and GoogleScholar electronic databases. The scientific literature search of international articles was performed in July 2016. In 1784, a Royal commission established in France by King Louis XVI tested Mesmer's claims concerning animal magnetism. By doing that, the commission, including such prominent scientists as the chemist Anton Lavoisier and the scientist and researcher on electricity and therapeutics Benjamin Franklin, played a central role in establishing the criteria needed to assess the level of evidence of electrical therapeutics in psychiatry. Surprisingly, it is possible to identify the classical Bradford Hill criteria of causation in the report of the commission, except the dose-effect relationship criteria. Since then, it has been conducted blinded randomized controlled trials that confirmed the effectiveness of ECT against ECT placebos for the treatment of psychiatric disorders. At present, the dose-effect relationship criteria can be analyzed through an EEG quality assessment of ECT-induced seizures. EEG quality assessment includes several indices: TSLOW (time to onset of seizure activity ≤5Hz, seconds), peak mid-ictal amplitude (mm), regularity (intensity or morphology of the seizure (0-6)), stereotypy (global seizure patterning, 0-3) and post-ictal suppression (0-3). A manual rating sheet is needed to score theses

  2. Risk Factors and Dose-Effect Relationship for Mandibular Osteoradionecrosis in Oral and Oropharyngeal Cancer Patients

    International Nuclear Information System (INIS)

    Lee, Ik Jae; Koom, Woong Sub; Lee, Chang Geol; Kim, Yong Bae; Yoo, Sei Whan; Keum, Ki Chang; Kim, Gwi Eon; Choi, Eun Chang; Cha, In Ho

    2009-01-01

    Purpose: To analyze risk factors and the dose-effect relationship for osteoradionecrosis (ORN) of the mandible after radiotherapy of oral and oropharyngeal cancers. Materials and Methods: One-hundred ninety-eight patients with oral (45%) and oropharyngeal cancer (55%) who had received external radiotherapy between 1990 and 2000 were retrospectively reviewed. All patients had a dental evaluation before radiotherapy. The median radiation dose was 60 Gy (range, 16-75 Gy), and the median biologically effective dose for late effects (BED late ) in bone was 114 Gy 2 (range, 30-167 Gy 2 ). Results: The frequency of ORN was 13 patients (6.6%). Among patients with mandibular surgery, eight had ORN at the surgical site. Among patients without mandibular surgery, five patients had ORN on the molar area of the mandible. The median time to ORN was 22 months (range, 1-69 months). Univariate analysis revealed that mandibular surgery and Co-60 were significant risk factors for ORN (p = 0.01 and 0.04, respectively). In multivariate analysis, mandibular surgery was the most important factor (p = 0.001). High radiation doses over BED 102.6 Gy 2 (conventional dose of 54 Gy at 1.8 Gy/fraction) were also a significant factor for ORN (p = 0.008) and showed a positive dose-effect relationship in logistic regression (p = 0.04) for patients who had undergone mandibular surgery. Conclusions: Mandibular surgery was the most significant risk factor for ORN of mandible in oral and oropharyngeal cancers patients. A BED of 102.6 Gy 2 or higher to the mandible also significantly increases the risk of ORN.

  3. The Relationship between Phytoplankton Evenness and Copepod Abundance in Lake Nansihu, China

    Directory of Open Access Journals (Sweden)

    Wang Tian

    2016-08-01

    Full Text Available The relationship between biodiversity and ecosystem functioning is a central issue in ecology. Previous studies have shown that producer diversity can impact the consumer community via predator-prey interactions. However, direct observations of this relationship remain rare, in particular for aquatic ecosystems. In this research, the relationship between phytoplankton diversity (species richness and evenness and the abundance of copepods was analyzed in Lake Nansihu, a meso-eutrophic lake in China. The results showed that copepods abundance was significantly decreased with increasing phytoplankton evenness throughout the year. However, both species richness and phytoplankton biomass showed no significant relationship with the abundance of copepods. Canonical correspondence analysis revealed that phytoplankton evenness was negatively correlated with Thermocyclops kawamurai, Cyclops vicinus, Eucyclops serrulatus, Mesocyclops leuckarti, Sinocalanus tenellus, Sinocalanus dorrii, Copepods nauplius, but positively correlated with many Cyanophyta species (Chroococcus minutus, Dactylococcopsis acicularis, Microcystis incerta, Merismopedia tenuissima, Merismopedia sinica and Lyngbya limnetica. Based on our results, phytoplankton evenness was a better predictor of copepods abundance in meso-eutrophic lakes. These results provide new insights into the relationship between diversity and ecosystem functioning in aquatic ecosystems.

  4. Tests of the linearity assumption in the dose-effect relationship for radiation-induced cancer

    International Nuclear Information System (INIS)

    Cohen, A.F.; Cohen, B.L.

    1978-01-01

    The validity of the BEIR linear extrapolation to low doses of the dose-effect relationship for radiation induced cancer is tested by use of natural radiation making use of selectivity on type of cancer, sex, age group, geographic area, and time period. For lung cancer, a linear interpolation between zero dose-zero effect and the data from radon-induced cancers in miners over-estimates the total number of observed lung cancers in many countries in the early years of this century; the discrepancy is substantially increased if the 30-44 year age range and/or if only females are considered, and by the fact that many other causes of lung cancer are shown to have been important at that time. The degree to which changes of diagnostic efficiency with time can influence the analysis is considered at some length. It is concluded that the linear relationship substantially over-estimates effects of low radiation doses. A similar analysis is applied to leukemia induced by natural radiation, applying selectivity by age, sex, natural background level, and date, and considering other causes. It is concluded that effects substantially larger than those obtained from linear extrapolation are excluded. The use of the selectivities mentioned above is justified by the fact that the incidence of cancer or leukemia is an upper limit on the rate at which it is caused by radiation effects; in determining upper limits it is justifiable to select situations which minimize it. (author)

  5. Comparison of the dose-effect relationship for UV radiation and ionizing radiation

    International Nuclear Information System (INIS)

    Leenhouts, H.P.; Sijsma, M.J.; Chadwick, K.H.

    1990-06-01

    Ionizing radiation and ultraviolet radiation (UV) are both physical agents with mutagenic and carcinogenic properties. However, there are some basic differences in the fundamental mechanism of their interaction with biological material that may have consequences for risk assessment. In this paper the dose-effect relationships for gamma radiation and UV at cellular level will be used to demonstrate the different radio-biological effectiveness of both agents. The results will be discussed in the framework of a biophysical model, based on the assumption that DNA doublestranded lesions are crucial for the cytotoxic action. After exposure to ionizing radiation, the lesions are fixed immediately following irradiation, but after UV exposure the lethal lesions are recognized only in the next DNA synthesis phase. The combination of this concept with the mechanism of lesion induction and the possibility of repair, leads to different dose and time relationships for the radiation effects of both agents. The possible consequences for risk assessment at low levels will be discussed. (author). 9 refs.; 5 figs

  6. Synoptic relationships between surface Chlorophyll-a and diagnostic pigments specific to phytoplankton functional types

    Directory of Open Access Journals (Sweden)

    M. Noguchi-Aita

    2011-02-01

    Full Text Available Error-quantified, synoptic-scale relationships between chlorophyll-a (Chl-a and phytoplankton pigment groups at the sea surface are presented. A total of ten pigment groups were considered to represent three Phytoplankton Size Classes (PSCs, micro-, nano- and picoplankton and seven Phytoplankton Functional Types (PFTs, i.e. diatoms, dinoflagellates, green algae, prymnesiophytes (haptophytes, pico-eukaryotes, prokaryotes and Prochlorococcus sp.. The observed relationships between Chl-a and PSCs/PFTs were well-defined at the global scale to show that a community shift of phytoplankton at the basin and global scales is reflected by a change in Chl-a of the total community. Thus, Chl-a of the total community can be used as an index of not only phytoplankton biomass but also of their community structure. Within these relationships, we also found non-monotonic variations with Chl-a for certain pico-sized phytoplankton (pico-eukaryotes, Prokaryotes and Prochlorococcus sp. and nano-sized phytoplankton (Green algae, prymnesiophytes. The relationships were quantified with a least-square fitting approach in order to enable an estimation of the PFTs from Chl-a where PFTs are expressed as a percentage of the total Chl-a. The estimated uncertainty of the relationships depends on both PFT and Chl-a concentration. Maximum uncertainty of 31.8% was found for diatoms at Chl-a = 0.49 mg m−3. However, the mean uncertainty of the relationships over all PFTs was 5.9% over the entire Chl-a range observed in situ (0.02 < Chl-a < 4.26 mg m−3. The relationships were applied to SeaWiFS satellite Chl-a data from 1998 to 2009 to show the global climatological fields of the surface distribution of PFTs. Results show that microplankton are present in the mid and high latitudes, constituting only ~10.9% of the entire phytoplankton community in the mean field for 1998–2009, in which diatoms explain ~7.5%. Nanoplankton are ubiquitous throughout the global surface oceans

  7. Iodine-131 treatment and chromosomal damage: in vivo dose-effect relationship.

    Science.gov (United States)

    Erselcan, Taner; Sungu, Selma; Ozdemir, Semra; Turgut, Bulent; Dogan, Derya; Ozdemir, Ozturk

    2004-05-01

    Although it is well known that radiation induces chromosomal aberrations, there is a lack of information on the in vivo dose-effect relationship in patients receiving iodine-131 treatment, and the results of previous studies are controversial. In this study, the sister chromatid exchange (SCE) method was employed to investigate acute and late chromosomal damage (CD) in the peripheral lymphocytes of 15 patients who received various doses of (131)I (259-3,700 MBq), either for thyrotoxicosis (TTX) or for ablation treatment in differentiated thyroid cancer (DTC). The SCE frequencies in cultured peripheral lymphocytes were determined before treatment (to assess basal SCE frequencies), on the 3rd day (to assess acute SCE frequencies) and 6 months later (to assess late SCE frequencies). The basal, acute and late SCE frequencies (mean+/-SD) were 3.19+/-0.93, 10.83+/-1.72 and 5.75+/-2.06, respectively, in the whole group, and these values differed significantly from each other ( Pdisappearance of damaged lymphocytes from the peripheral circulation in a dose-dependent manner following (131)I treatment. Further studies are therefore needed to clarify the effect of the negative beta value on the biological dosimetry approach in continuous internal low LET radiation, as in the case of (131)I treatment.

  8. Iodine-131 treatment and chromosomal damage: in vivo dose-effect relationship

    International Nuclear Information System (INIS)

    Erselcan, Taner; Ozdemir, Semra; Turgut, Bulent; Dogan, Derya; Sungu, Selma; Ozdemir, Ozturk

    2004-01-01

    Although it is well known that radiation induces chromosomal aberrations, there is a lack of information on the in vivo dose-effect relationship in patients receiving iodine-131 treatment, and the results of previous studies are controversial. In this study, the sister chromatid exchange (SCE) method was employed to investigate acute and late chromosomal damage (CD) in the peripheral lymphocytes of 15 patients who received various doses of 131 I (259-3,700 MBq), either for thyrotoxicosis (TTX) or for ablation treatment in differentiated thyroid cancer (DTC). The SCE frequencies in cultured peripheral lymphocytes were determined before treatment (to assess basal SCE frequencies), on the 3rd day (to assess acute SCE frequencies) and 6 months later (to assess late SCE frequencies). The basal, acute and late SCE frequencies (mean±SD) were 3.19±0.93, 10.83±1.72 and 5.75±2.06, respectively, in the whole group, and these values differed significantly from each other (P 131 I dose in the whole group, but a negative correlation was found between the 131 I dose and the RR at the 6th month (r=-0.60, P=0.04). The best fit for this relationship was obtained by a linear-quadratic model, as y=104.89x-28.4x 2 +38.1 (R 2 =0.51, P=0.04). On the other hand, comparative analysis with the results of previous studies with comparable sampling times revealed that the best fit for the relationships between the administered dose of 131 I and DR and RR were obtained with a linear-quadratic model (Y=αD+βD 2 ) rather than a linear one. However, there was an interesting difference in comparison with in vitro studies, in that we found the coefficient β to have a negative value, suggesting the disappearance of damaged lymphocytes from the peripheral circulation in a dose-dependent manner following 131 I treatment. Further studies are therefore needed to clarify the effect of the negative β value on the biological dosimetry approach in continuous internal low LET radiation, as in the case

  9. Tests of the linearity assumption in the dose-effect relationship for radiation-induced cancer

    International Nuclear Information System (INIS)

    Cohen, A.F.; Cohen, B.L.

    1980-01-01

    The validity of the BEIR linear extrapolation to low doses of the dose-effect relationship for radiation induced cancer is tested by use of natural radiation making use of selectivity on type of cancer, smoking habits, sex, age group, geographic area and/or time period. For lung cancer, a linear interpolation between zero dose-zero effect and the data from radon-induced cancers in miners implies that the majority of all lung cancers among non-smokers are due to radon; since lung cancers in miners are mostly small-cell undifferentiated (SCU), a rather rare type in general, linearity over predicts the frequency of SCU lung cancers among non smokers by a factor of 10, and among non-smoking females age 25-44 by a factor of 24. Similarly, linearity predicts that the majority of all lung cancers early in this century were due to radon even after due consideration is given to cases missed by poor diagnostic efficiency (this matter is considered in some detail). For the 30-40 age range, linearity over predicts the total lung cancer rate at that time by a factor of 3-6; for SCU lung cancer, the over-prediction is by at least a factor of 10. Other causes of lung cancer are considered which further enhance the degree to which the linearity assumption over-estimates the effects of low level radiation. A similar analysis is applied to leukemia induced by natural radiation. It is concluded that the upper limit for this is not higher than estimates from the linearity hypothesis. (author)

  10. Chromosomal damage after Iodine-131 treatment for differentiated thyroid cancer: in vivo dose-effect relationship

    International Nuclear Information System (INIS)

    Nguyen, V.K.; Nguyen, X.P.; Truong, Q.X.

    2007-01-01

    Full text: Although it is well known that radiation induces chromosomal aberrations, there is a lack of information on the in- vivo dose-effect relationship in patients receiving Iodine-131 treatment and the results of previous studies are controversial. In this study, the dicentric chromosomal aberrations (DCA) analysis method was employed to investigate acute and late chromosomal damage (CD) in the peripheral lymphocytes of 58 differentiated thyroid cancer patients who received dose 1,1 GBq of Iodine-131 (group A), and 34 patients who received dose 3,7 GBq of Iodine- 131 (group B). The mean 100 metaphase spreads were scored for each subject. The DCA frequencies in cultured peripheral lymphocytes were determined before treatment to assess basal DCA frequencies, on the 3rd day to assess acute DCA frequencies and 6 months later to assess late DCA frequencies. The basal, acute and late DCA frequencies were divided into two groups: 0,18%, 2,14% and 0,53% (group A) and 0,18%, 2,12 % and 0,89% (group B), respectively, and these values differed significantly at various time after treatment (p 2 = 0,987), and group B as Y= 32,71 + 0,189 X. (r = 0,9381, R 2 = 0,880). However, there was an interesting difference in comparison with in- vitro studies, in that we found the coefficient β to have a negative value, suggesting the disappearance of damaged lymphocytes from peripheral circulation in a dose- dependent manner following Iodine-131 treatment. Further studies are therefore needed to clarify the effect of the negative β value on biological dosimetry approach in continuous internal low LET radiation, as in the case of Iodine-131 treatment. (author)

  11. The relationship between phytoplankton distribution and water column characteristics in North West European shelf sea waters.

    Science.gov (United States)

    Fehling, Johanna; Davidson, Keith; Bolch, Christopher J S; Brand, Tim D; Narayanaswamy, Bhavani E

    2012-01-01

    Phytoplankton underpin the marine food web in shelf seas, with some species having properties that are harmful to human health and coastal aquaculture. Pressures such as climate change and anthropogenic nutrient input are hypothesized to influence phytoplankton community composition and distribution. Yet the primary environmental drivers in shelf seas are poorly understood. To begin to address this in North Western European waters, the phytoplankton community composition was assessed in light of measured physical and chemical drivers during the "Ellett Line" cruise of autumn 2001 across the Scottish Continental shelf and into adjacent open Atlantic waters. Spatial variability existed in both phytoplankton and environmental conditions, with clear differences not only between on and off shelf stations but also between different on shelf locations. Temperature/salinity plots demonstrated different water masses existed in the region. In turn, principal component analysis (PCA), of the measured environmental conditions (temperature, salinity, water density and inorganic nutrient concentrations) clearly discriminated between shelf and oceanic stations on the basis of DIN:DSi ratio that was correlated with both salinity and temperature. Discrimination between shelf stations was also related to this ratio, but also the concentration of DIN and DSi. The phytoplankton community was diatom dominated, with multidimensional scaling (MDS) demonstrating spatial variability in its composition. Redundancy analysis (RDA) was used to investigate the link between environment and the phytoplankton community. This demonstrated a significant relationship between community composition and water mass as indexed by salinity (whole community), and both salinity and DIN:DSi (diatoms alone). Diatoms of the Pseudo-nitzschia seriata group occurred at densities potentially harmful to shellfish aquaculture, with the potential for toxicity being elevated by the likelihood of DSi limitation of

  12. The relationship between phytoplankton distribution and water column characteristics in North West European shelf sea waters.

    Directory of Open Access Journals (Sweden)

    Johanna Fehling

    Full Text Available Phytoplankton underpin the marine food web in shelf seas, with some species having properties that are harmful to human health and coastal aquaculture. Pressures such as climate change and anthropogenic nutrient input are hypothesized to influence phytoplankton community composition and distribution. Yet the primary environmental drivers in shelf seas are poorly understood. To begin to address this in North Western European waters, the phytoplankton community composition was assessed in light of measured physical and chemical drivers during the "Ellett Line" cruise of autumn 2001 across the Scottish Continental shelf and into adjacent open Atlantic waters. Spatial variability existed in both phytoplankton and environmental conditions, with clear differences not only between on and off shelf stations but also between different on shelf locations. Temperature/salinity plots demonstrated different water masses existed in the region. In turn, principal component analysis (PCA, of the measured environmental conditions (temperature, salinity, water density and inorganic nutrient concentrations clearly discriminated between shelf and oceanic stations on the basis of DIN:DSi ratio that was correlated with both salinity and temperature. Discrimination between shelf stations was also related to this ratio, but also the concentration of DIN and DSi. The phytoplankton community was diatom dominated, with multidimensional scaling (MDS demonstrating spatial variability in its composition. Redundancy analysis (RDA was used to investigate the link between environment and the phytoplankton community. This demonstrated a significant relationship between community composition and water mass as indexed by salinity (whole community, and both salinity and DIN:DSi (diatoms alone. Diatoms of the Pseudo-nitzschia seriata group occurred at densities potentially harmful to shellfish aquaculture, with the potential for toxicity being elevated by the likelihood of DSi

  13. Seasonal variations of phytoplankton dynamics in Nunatsiavut fjords (Labrador, Canada) and their relationships with environmental conditions

    Science.gov (United States)

    Simo-Matchim, Armelle-Galine; Gosselin, Michel; Blais, Marjolaine; Gratton, Yves; Tremblay, Jean-Éric

    2016-04-01

    We assessed phytoplankton dynamics and its environmental control in four Labrador fjords (Nachvak, Saglek, Okak, and Anaktalak) during summer, early fall and late fall. Primary production and chlorophyll a (chl a) biomass were measured at seven optical depths, including the depth of subsurface chl a maximum (SCM). Phytoplankton abundance, size structure and taxonomy were determined at the SCM. Principal component analysis and non-metric multidimensional scaling were used to analyze relationships between production, biomass and community composition in relation to environmental variables. We observed a marked seasonal variability, with significant differences in phytoplankton structure and function between summer and fall. Surprisingly, primary production and chl a biomass were not significantly different from one fjord to another. The highest values of primary production (1730 mg C m- 2 day- 1) and chl a biomass (96 mg chl a m- 2) were measured during the summer bloom, and those high values indicate that Labrador fjords are highly productive ecosystems. The summer community showed relatively high abundance of nanophytoplankton (2-20 μm) while the fall community was characterized by low primary production and chl a biomass as well as relatively high abundance of picophytoplankton (< 2 μm). The low value of carbon potentially exported out of the euphotic zone throughout the study (≤ 31% of total primary production) suggests that phytoplankton production was mainly grazed by microzooplankton rather than being exported to greater depths. We observed a mixed assemblage of diatoms and flagellates in summer, whereas the fall community was largely dominated by flagellates. Seasonal variations in phytoplankton dynamics were mainly controlled by the strength of the vertical stratification and by the large differences in day length due to the northerly location of Labrador fjords. This study documents for the very first time phytoplankton structure and function in

  14. A recalculation of the age dependent dose-effect-relationship of the life span study of Hiroshima and Nagasaki

    International Nuclear Information System (INIS)

    Kottbauer, M.M.; Fleck, C.M.; Schoellnberger, H.

    1996-01-01

    The basis of the presented model is the multistage process of carcinogenesis as a biological effect. It provides simultaneously the age-dependent mortality of spontaneous and radiation induced solid tumors and dose-effect relationships at any age after exposure. The model has been used to describe the solid cancer mortality rates of the atomic bomb survivors of Hiroshima and Nagasaki. It has characteristics of both relative and absolute risk projections depending on the age of exposure. (author)

  15. Study on dose-effect relationship of radiation-induced DNA damage using single cell gel electrophoresis

    International Nuclear Information System (INIS)

    Liu Qiang; Jiang Enhai; Li Jin; Tang Weisheng; Wang Zhiquan; Zhao Yongcheng; Fan Feiyue

    2006-01-01

    Objective: To explore a new, simple and quick radiation biodosimeter, which can be applied to estimate biological dose in case of radiation accident. Methods: DNA double-strand break were detected using neutral single cell gel electrophoresis (SCGE), and all the indexes of comet assay including HDNA%, TDNA%, CL, TL, TM, and OTM were analyzed by CASP (Comet Assay Software Project). The curve of dose-effect was fitted using SPSS 12.0 software. Results: Statistically significant dose-effect relationships were observed in all the indexes of comet assay, OTM was superior to other indexes. Conclusions: Application of neutral comet assay combined with CASP analysis could serve as a new radiation biodosimeter. (authors)

  16. Dose-Effect Relationships for Adverse Events After Cranial Radiation Therapy in Long-term Childhood Cancer Survivors

    International Nuclear Information System (INIS)

    Dijk, Irma W.E.M. van; Cardous-Ubbink, Mathilde C.; Pal, Helena J.H. van der; Heinen, Richard C.; Leeuwen, Flora E. van; Oldenburger, Foppe; Os, Rob M. van; Ronckers, Cécile M.; Schouten–van Meeteren, Antoinette Y.N.; Caron, Huib N.; Koning, Caro C.E.; Kremer, Leontien C.M.

    2013-01-01

    Purpose: To evaluate the prevalence and severity of clinical adverse events (AEs) and treatment-related risk factors in childhood cancer survivors treated with cranial radiation therapy (CRT), with the aim of assessing dose-effect relationships. Methods and Materials: The retrospective study cohort consisted of 1362 Dutch childhood cancer survivors, of whom 285 were treated with CRT delivered as brain irradiation (BI), as part of craniospinal irradiation (CSI), and as total body irradiation (TBI). Individual CRT doses were converted into the equivalent dose in 2-Gy fractions (EQD 2 ). Survivors had received their diagnoses between 1966 and 1996 and survived at least 5 years after diagnosis. A complete inventory of Common Terminology Criteria for Adverse Events grade 3.0 AEs was available from our hospital-based late-effect follow-up program. We used multivariable logistic and Cox regression analyses to examine the EQD 2 in relation to the prevalence and severity of AEs, correcting for sex, age at diagnosis, follow-up time, and the treatment-related risk factors surgery and chemotherapy. Results: There was a high prevalence of AEs in the CRT group; over 80% of survivors had more than 1 AE, and almost half had at least 5 AEs, both representing significant increases in number of AEs compared with survivors not treated with CRT. Additionally, the proportion of severe, life-threatening, or disabling AEs was significantly higher in the CRT group. The most frequent AEs were alopecia and cognitive, endocrine, metabolic, and neurologic events. Using the EQD 2 , we found significant dose-effect relationships for these and other AEs. Conclusion: Our results confirm that CRT increases the prevalence and severity of AEs in childhood cancer survivors. Furthermore, analyzing dose-effect relationships with the cumulative EQD 2 instead of total physical dose connects the knowledge from radiation therapy and radiobiology with the clinical experience

  17. Dose-Effect Relationships for Adverse Events After Cranial Radiation Therapy in Long-term Childhood Cancer Survivors

    Energy Technology Data Exchange (ETDEWEB)

    Dijk, Irma W.E.M. van, E-mail: i.w.vandijk@amc.uva.nl [Department of Radiation Oncology, Academic Medical Center, Amsterdam (Netherlands); Cardous-Ubbink, Mathilde C. [Department of Medical Oncology, Academic Medical Center, Amsterdam (Netherlands); Pal, Helena J.H. van der [Department of Medical Oncology, Academic Medical Center, Amsterdam (Netherlands); Department of Pediatric Oncology, Emma Children' s Hospital/Academic Medical Center, Amsterdam (Netherlands); Heinen, Richard C. [Department of Pediatric Oncology, Emma Children' s Hospital/Academic Medical Center, Amsterdam (Netherlands); Leeuwen, Flora E. van [Department of Epidemiology, Netherlands Cancer Institute, Amsterdam (Netherlands); Oldenburger, Foppe; Os, Rob M. van [Department of Radiation Oncology, Academic Medical Center, Amsterdam (Netherlands); Ronckers, Cécile M. [Dutch Childhood Oncology Group, Long-term Effects after Childhood Cancer, The Hague (Netherlands); Schouten–van Meeteren, Antoinette Y.N. [Department of Pediatric Oncology, Emma Children' s Hospital/Academic Medical Center, Amsterdam (Netherlands); Caron, Huib N. [Department of Medical Oncology, Academic Medical Center, Amsterdam (Netherlands); Department of Pediatric Oncology, Emma Children' s Hospital/Academic Medical Center, Amsterdam (Netherlands); Koning, Caro C.E. [Department of Radiation Oncology, Academic Medical Center, Amsterdam (Netherlands); Kremer, Leontien C.M. [Department of Medical Oncology, Academic Medical Center, Amsterdam (Netherlands); Department of Pediatric Oncology, Emma Children' s Hospital/Academic Medical Center, Amsterdam (Netherlands)

    2013-03-01

    Purpose: To evaluate the prevalence and severity of clinical adverse events (AEs) and treatment-related risk factors in childhood cancer survivors treated with cranial radiation therapy (CRT), with the aim of assessing dose-effect relationships. Methods and Materials: The retrospective study cohort consisted of 1362 Dutch childhood cancer survivors, of whom 285 were treated with CRT delivered as brain irradiation (BI), as part of craniospinal irradiation (CSI), and as total body irradiation (TBI). Individual CRT doses were converted into the equivalent dose in 2-Gy fractions (EQD{sub 2}). Survivors had received their diagnoses between 1966 and 1996 and survived at least 5 years after diagnosis. A complete inventory of Common Terminology Criteria for Adverse Events grade 3.0 AEs was available from our hospital-based late-effect follow-up program. We used multivariable logistic and Cox regression analyses to examine the EQD{sub 2} in relation to the prevalence and severity of AEs, correcting for sex, age at diagnosis, follow-up time, and the treatment-related risk factors surgery and chemotherapy. Results: There was a high prevalence of AEs in the CRT group; over 80% of survivors had more than 1 AE, and almost half had at least 5 AEs, both representing significant increases in number of AEs compared with survivors not treated with CRT. Additionally, the proportion of severe, life-threatening, or disabling AEs was significantly higher in the CRT group. The most frequent AEs were alopecia and cognitive, endocrine, metabolic, and neurologic events. Using the EQD{sub 2}, we found significant dose-effect relationships for these and other AEs. Conclusion: Our results confirm that CRT increases the prevalence and severity of AEs in childhood cancer survivors. Furthermore, analyzing dose-effect relationships with the cumulative EQD{sub 2} instead of total physical dose connects the knowledge from radiation therapy and radiobiology with the clinical experience.

  18. [Study on relationship of dose-effect and time-effect of APA microencapsulated bovine chromaffin cells on pain treatment].

    Science.gov (United States)

    Hui, Jianfeng; Li, Tao; Du, Zhi; Song, Jichang

    2011-12-01

    This study was to investigate the relationship of dose-effect and time-effect of Alginate-Polylysine-Alginate (APA) microencapsulated bovine chromaffin cells on the treatment of pain model rats. Using a rat model of painful peripheral neuropathy, the antinociceptive effects of APA microencapsulated bovine cells transplanted into the subarachnoid space was evaluated by cold allodynia test and hot hyperalgesia test. Compared with control group, the withdrawal difference with cell number 50 thousands groups, 100 thousands groups and 200 thousands groups was reduced (P APA microencapsulated bovine chromaffin cells which were transplanted to treat pain model rats, and the effective antinociception remained longer than 12 weeks.

  19. Grain elevator workers show work-related pulmonary function changes and dose-effect relationships with dust exposure.

    Science.gov (United States)

    Corey, P; Hutcheon, M; Broder, I; Mintz, S

    1982-01-01

    The purpose of this study was to determine whether grain handlers underwent work-related changes in their pulmonary function and, if so, to examine the dose-effect relationships with dust exposure. The pulmonary function of grain handlers was measured at the beginning and end of work shifts over a period of one week, during which their exposure to dust was measured daily. The results showed changes indicative of a within-day obstructive change, in addition to a small restrictive defect occurring over the course of a week. Civic outside labourers who were examined as a control group showed a similar within-week obstructive change without any associated restriction of lung volume. The data on the grain handlers were also used to examine the dose-effect relationships of dust exposure, both on baseline pulmonary function and on within-day changes in these measurements. The baseline flow rates of workers who did not wear a mask were found to vary inversely with their average exposure to respirable dust. In addition, the flow rates underwent a within-day decrease that varied directly with their corresponding exposure to respirable dust and was unrelated to mask wearing. The median of the slopes for this relationship indicated that 50% of the subjects had a decrease of at least 923 ml/s in the value of their Vmax50%VC for each 1 mg/m3 increase in the concentration of respirable dust. Non-respirable dust did not have a measurable effect either on the baseline or the within-day changes in pulmonary function. The acute changes were unaffected by age, duration of employment, or extent of smoking. PMID:7138793

  20. Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

    International Nuclear Information System (INIS)

    Garnier-Laplace, Jacqueline; Beaugelin-Seiller, Karine; Della-Vedova, Claire; Metivier, Jean-Michel; Ritz, Christian; Mousseau, Timothy A.; Pape Moeller, Anders

    2015-01-01

    We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011-2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31 μGy h -1 ) with the dose rate reconstructed for adult birds of each species (from 0.3 to 97 μGy h -1 ), we confirmed that the overall bird abundance at Fukushima decreased with increasing total doses. This relationship was directly consistent with exposure levels found in the literature to induce physiological disturbances in birds. Among the 57 species constituting the observed bird community, we found that 90% were likely chronically exposed at a dose rate that could potentially affect their reproductive success. We quantified a loss of 22.6% of the total number of individuals per increment of one unit log10-transformed total dose (in Gy), over the four-year post-accident period in the explored area. We estimated that a total dose of 0.55 Gy reduced by 50% the total number of birds in the study area over 2011-2014. The data also suggest a significant positive relationship between total dose and species diversity. (authors)

  1. The biological bases of the dose-effect relationship; Les bases biologiques de la relation dose-effet

    Energy Technology Data Exchange (ETDEWEB)

    Lafuma, J

    2001-06-01

    In radiation protection, the recent data in epidemiology, in animal experimentation and on the base researches are no more compatible with a linear dose-effect relationship without threshold and do not account for the radiological risks at low doses. The cancers should be accelerated by radiations as any pathology linked to the ageing and for which threshold exit. Relative to the genetic risk it is known today that the natural exposure that lasts for several generations has not lead excess of hereditary illness as it was to be feared in 1959 for several countries. Considering that for populations the exposure levels induced by human activities have already been, under these ones of average natural exposures the genetic risk can be negligible and it is the somatic risk alone, with its thresholds that has to be into account. (N.C.)

  2. Dose-effect relationship of apoptosis induced by fission-neutron in murine thymocytes

    International Nuclear Information System (INIS)

    Yuan Bin; Li Liang; Xue Wencheng; Sun Jianmin; Wang Baoqin

    2000-01-01

    Objective: To investigate the effectiveness of high LET fission-neutron to induce apoptosis in murine thymocytes and to compare it with that of low LET 60 Co γ-ray. Methods: Apoptosis induction was studied qualitatively by light and transmission electron microscopy and DNA gel electrophoresis,also quantitatively by flow cytometry(FCM) and diphenylamine (DPA)methods. Results: DNA ladders of murine thymocytes were detectable, the typical apoptosis of thymocytes could be observed morphologically by means of light and electron microscopy at 6 h after fission-neutron irradiation with doses ranging from 0.5 to 5.0 Gy, meanwhile the percentages of apoptosis increased with increasing doses. After exposure to γ-rays with doses ranging from 1.0 to 30 Gy, the experimental results were similar to those from neutron radiation. The incidence of apoptosis peaked at about 20 Gy, the percentages did not increase further when doses increased. Conclusion: Apoptosis of murine thymocytes can be induced when mice are exposed to either fission-neutron (0.5-5.0 Gy) or to γ-ray (1-30 Gy). Although the relationship between apoptosis and radiation doses is similar, the percentage of apoptosis induced by neutron irradiation is higher than that induced by γ-irradiation. The RBE values of fission-neutron for inducing apoptosis murine thymocytes are 2.09 (by FCM method) and 2.37 (by DPA method), respectively. These results also suggest that fission-neutron-induced murine immune tissue is more severe than that induced by γ-rays at several hours post-irradiation and this might be the basis for heavy damage to immune tissues induced by fission-neutron-irradiation in later period

  3. Phytoplankton chlorophyll

    NARCIS (Netherlands)

    van de Poll, W.H.; Kulk, G.; Timmermans, K.R.; Brussaard, C.P.D.; van der Woerd, H.J.; Kehoe, M.J.; Mojica, K.D.A.; Visser, R.J.W.; Rozema, P.D.; Buma, A.G.J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 degrees N in the northeast

  4. Mixed Beam Murine Harderian Gland Tumorigenesis: Predicted Dose-Effect Relationships if neither Synergism nor Antagonism Occurs

    Energy Technology Data Exchange (ETDEWEB)

    Siranart, Nopphon; Blakely, Eleanor A.; Cheng, Alden; Handa, Naval; Sachs, Rainer K.

    2016-12-01

    Complex mixed radiation fields exist in interplanetary space, and not much is known about their latent effects on space travelers. In silico synergy analysis default predictions are useful when planning relevant mixed-ion-beam experiments and interpreting their results. These predictions are based on individual dose-effect relationships (IDER) for each component of the mixed-ion beam, assuming no synergy or antagonism. For example, a default hypothesis of simple effect additivity has often been used throughout the study of biology. However, for more than a century pharmacologists interested in mixtures of therapeutic drugs have analyzed conceptual, mathematical and practical questions similar to those that arise when analyzing mixed radiation fields, and have shown that simple effect additivity often gives unreasonable predictions when the IDER are curvilinear. Various alternatives to simple effect additivity proposed in radiobiology, pharmacometrics, toxicology and other fields are also known to have important limitations. In this work, we analyze upcoming murine Harderian gland (HG) tumor prevalence mixed-beam experiments, using customized open-source software and published IDER from past single-ion experiments. The upcoming experiments will use acute irradiation and the mixed beam will include components of high atomic number and energy (HZE). We introduce a new alternative to simple effect additivity, "incremental effect additivity", which is more suitable for the HG analysis and perhaps for other end points. We use incremental effect additivity to calculate default predictions for mixture dose-effect relationships, including 95% confidence intervals. We have drawn three main conclusions from this work. 1. It is important to supplement mixed-beam experiments with single-ion experiments, with matching end point(s), shielding and dose timing. 2. For HG tumorigenesis due to a mixed beam, simple effect additivity and incremental effect additivity sometimes give

  5. Reversal in the relationship between species richness and turnover in a phytoplankton community.

    Science.gov (United States)

    Matthews, Blake; Pomati, Francesco

    2012-11-01

    Negative relationships between species richness and the rate of compositional turnover are common, suggesting that diverse communities have greater stability than depauperate ones; however, the mechanistic basis for this pattern is still widely debated. Species richness and turnover can covary either because they are mechanistically linked or because they share common environmental drivers. Few empirical studies have combined long-term changes in community composition with multiple drivers of environmental change, and so little is known about how the underlying mechanisms of species coexistence interact with changes in the mean and variability of environmental conditions. Here, we use a 33 year long time series (1976-2008) of phytoplankton community composition from Lake Zurich, to examine how environmental variation influences the relationship between richness and annual turnover. We find that the relationship between richness and annual turnover reverses midway through the time series (1992-1993), leading to a hump-shaped relationship between species richness and annual turnover. Using structural equation modeling we show that annual turnover and diversity are independently associated with different drivers of environmental change. Furthermore, we find that the observed annual sequences of community assembly give rise to rates of species accumulation that are more heterogeneous through time than expected by chance, likely owing to a high proportion of species showing significant autocorrelation and to strong positive covariation in the occurrences of species.

  6. Phytoplankton diversity and its relationships to the physico-chemical environment in the Banglang Reservoir, Yala Province

    Directory of Open Access Journals (Sweden)

    Saowapa Angsupanich

    2004-09-01

    Full Text Available The diversity of phytoplankton and its relationships to the physico- chemical environment were studied in Banglang Reservoir, located on the Pattani River in Southern Thailand. Samples were collected monthly from May 2000 to April 2001 at three stations and three different depths: water surface, 10, and 30 meters. Physico-chemical parameters: temperature, pH, dissolved oxygen, alkalinity, conductivity, water transparency, and nutrients were measured simultaneously. One-hundred and thirty-five species in seven divisions of phytoplankton were found. The greatest number of species were in Division Chlorophyta (50%, followed by Cyanophyta (21%, Bacillariophyta (13%, Pyrrophyta (6%, Cryptophyta (4%, Chrysophyta (3% and Euglenophyta (3%. The most diverse genus was Staurastrum (15 species. Phytoplankton density ranged from zero to 2.1x109 cells.m-3. Microcystis aeruginosa Kutzing in January at 30 m at the lacustrine zone had the highest phytoplankton density. By applying a PCA(principal components analysis using the MVSP statistical analysis program on the abundance of species, it was found that Cyclotella meneghiniana Kutzing and Melosira varians Agardh were the most abundant in each station. Diversity index (Simpson’s diversity index was maximum at 10 m at the transition zone and lowest at the outflow zone. The factors affecting the phytoplankton species by Canonical correspondence analysis ordination (PC-ORD programwere alkalinity, water temperature, water transparency, nutrients and conductivity. When the water quality parameters were classified by the trophic level, Banglang Reservoir belonged to oligo-mesotrophic status. Furthermore, Cyclotella meneghiniana Kutzing and Melosira varians Agardh could be used as the phytoplankton indicator of oligo-mesotrophic reservoir.

  7. The Community Structure of Phytoplankton in Seagrass Ecosystem and its Relationship with Environmental Characterstics

    Directory of Open Access Journals (Sweden)

    Gede Iwan Setiabudi

    2016-12-01

    Full Text Available The aimed of this study was to determine  the plankton communities and its relationship with the chemical and physical condition in seagrass ecosystem at Pegametan Bay. The composition and abundance of plankton were observed in the sea water underneath the surface and were identified based on the guideline of Illustration of the Marine Plankton of Japan. The water quality was measured in situ using WQC HI 9829. The water sample was measured using closed reflux spectrometry for COD, TOC analyzer for DOC and APHA 2102 (4500 method for Nt and Pt. There are 27 species of plankton identified, which can be classified into three groups. Diatom group consists of 18 species with a 74.56% abundance. The non-litoral group consists of 6 species with a 23.35% abundance. Moreover, dinoflagellate group consist of 3 species with a 2.09% abundance. An abundance of plankton greater than 104 cell.L-1 was found in diatome group (Nitzschia sp., Thalassiosira sp., Chaetoceros sp., Flagillaria sp., Thalassiothrix sp., and Melosira sp. and non-litoral group (Oscillatoria sp. and Spirogyra sp.. The abundance of those species indicated the algae bloom phenomenon. Dinophysis sp. was also identified, which was harmful algal blooms.How to CiteSetiabudi, G. I., Bengen, D. G., Effendi, H., & Radjasa, O. K. (2016. The Community Structure of Phytoplankton in Seagrass Ecosystem and its Relationship with Environmental Characterstics. Biosaintifika: Journal of Biology & Biology Education, 8(3, 257-269.

  8. The study on the dose-effect relationship of radiation from α particles of plutonium on certain lung cells (in vivo and in vitro)

    International Nuclear Information System (INIS)

    Wu Dechang; Ye Changqing; Gong Yifen; Yan Xiaoshan; Xie Guoliang; Liu Guolian; Chen Winchung; Hu Lianping; Shen Zhiyuan

    1993-01-01

    It is well known that plutonium is one of the most toxic radionuclides and its carcinogenic risk has been seriously concerned. In this study, the dose effect relationship of radiation from α particles of plutonium on certain lung cells (in vivo and in vitro) were investigated. The topics of study are as following: In vivo: deposition and clearance of Pu in respiratory tract, dose-effect relationship of lung cancer induced, histopathological type of lung cancer, primary hemangiosarcoma occurred in thoracic lumph node, radiation effects on Alveolar Macrophage (AM), radiation effect on Natural Killer Cell (NK) and radiation effect on Alveolar Type II (AT-II). In vitro: radiation effect on the immunological functions of AM, radiation effect on the membrane of AM, possible relationship between cytotoxicity and membranes of AM, effects of radiation (X, α) on the transformation of Wistar rat lung fibroblast cell line (WAL-F1) and protective effect of Se 4+ against transformation

  9. Phytoplankton distribution and their relationship to environmental variables in Sanya Bay, South China Sea

    Directory of Open Access Journals (Sweden)

    Yanying Zhang

    2010-11-01

    Full Text Available Phytoplankton quantification was conducted in Sanya Bay from January 2005 to February 2006. A submersible in situ spectrofluorometer, which permits the differentiation of four algal groups (green algae, diatoms and dinoflagellates, cryptophytes and cyanobacteria was used. Seasonal variation of total chlorophyll a concentration showed that high value appeared in summer and low concentration occurred in spring. Diatoms and dinoflagellates group was the predominant phytoplankton all year in the Bay. The stable stratification of phytoplankton vertical distribution came into being in July. During the stratification event, the total chlorophyll a concentration of deep layer was much higher than the surface; cyanobacteria and cryptophyta groups decreased and almost disappeared, however, the concentration of green algae and diatoms and dinoflagellates groups increased. In deep layer, the concentration of diatoms and dinoflagellates group increased sharply, which was about eight times more than that in the surface layer. The vertical profiles character of phytoplankton showed that from inshore stations to outer bay the stratification of phytoplankton vertical distribution gradually strengthened. Dissolved inorganic nutrient especially phosphate and inorganic nitrogen and cold-water upwelling were the main regulating factor for phytoplankton distribution.

  10. A recalculation of the dose-effect-relationship of the ''life span study'' of Hiroshima and Nagasaki with the ''single-hit model''

    International Nuclear Information System (INIS)

    Kottbauer, M.M.; Fleck, C.M.; Schoellnberger, H.

    1996-01-01

    The basis of this new model is the multistage process of carcinogeneses. The Single-Hit Model is a further development of the Armitage-Doll Model [1] for the special case of a short exposure. It provides simultaneously the age-dependent mortality-rate (incidence-rate) of the spontaneous and radiation induced solid tumors and dose-effect relationships at any age after exposure. The model results in a biologically based dose-effect relationship, which is similar to the Relativ-Risk-Model suggested by the ICRP 60 [2]. The present model is able to describe the increased mortality rate of the bomb survivors more accurate than the Relativ-Risk-Model. (orig.) [de

  11. The role of neutron activation analysis and radioanalytical methods in dose-effect relationship studies for the setting of trace metal protection criteria

    International Nuclear Information System (INIS)

    Sabbioni, E.; Pietra, R.; Edel, J.; Goetz, L.

    1986-01-01

    In order to prepare a scientifically accurate health protection criteria documents for trace metals integrated multidisciplinary research is necessary. In particular, the rational for structuring the documents should be based primarily on the two major questions of exposure and response. Unfortunately, in a majority of cases there is a paucity of relevant data to the establishment of dose-effect relationships. This work intends to show the role that neutron activation analysis and radiotracers with very high specific radioactivity have in solving problems relevant for establishment dose-effect relationships for trace metals. Typical applications in the different research areas involved in the preparation of the protection criteria, from source and exposure to levels and forms of trace metals in humans, are presented. (author)

  12. [Phytoplankton's community structure and its relationships with environmental factors in the rivers of Tongling City, Anhui Province of East China in winter].

    Science.gov (United States)

    Wang, Li; Wei, Wei; Zhou, Ping; Li, Yang; Sun, Qing-Ye

    2013-01-01

    Tongling is one of the main non-ferrous metal mining areas in China, and the biodiversity in the river ecosystem of this area is seriously affected by heavy metals as a result of mining activities. In the winter in 2010, an investigation was conducted on the community structure of phytoplankton and its relationships with environmental factors in the main sections of the rivers in Tongling. A total of 203 phytoplankton species were identified, belonging to 96 genera and 8 phyla. The community structure of the phytoplankton differed obviously in different river sections, but the communities were all dominated by Bacillariophyta, Chlorophyta and Cyanophyta. The phytoplankton abundance ranged from 9.1 x 10(3) to 6.5 x 10(7) cells x L(-1), and the quantity of the phytoplankton in the river sections directly carried with mining waste water was significantly low. The Shannon index of the phytoplankton community at different sampling sites ranged from 0 to 3.45, with a significant discrepancy in different river sections. There existed significant correlations between the density and group number of phytoplankton and the COD(Cr) and cadmium, copper and zinc concentrations in the rivers, and the concentrations of river total nitrogen, NH4(+)-N, NO3(-)-N, and copper, COD(Cr) and pH were the main environmental variables affecting the phytoplankton' s community structure and its spatial distribution. Although the nutritional status of the river waters had greater effects on the community structure of phytoplankton, the effects of the heavy metals there from mining enterprises could not be neglected.

  13. Dose-effect relationship in production of dicentrics and rings in blood lymphocytes of individuals living in high background radiation area

    International Nuclear Information System (INIS)

    Jiang Tao; Hayata, I.; Wang Cunyan

    1999-01-01

    Objective: To explore the dose-effect relationship in the production of chromosome aberrations by high background radiation by using statistically appropriate individual measurements. Methods: Chromosome analysis was performed in separated blood lymphocytes of 39 family members of different ages from either high background radiation area (HBRA) or control area (CA). Individual cumulative doses ranged from 23.9-261.3 and 5.2-29.8 mGy for HBRA and CA, respectively. A total of about 100,000 cells were scored and dicentric and ring chromosome (dic + Rc) aberrations recorded. Results: In the case of HBRA, individual chromosome aberration frequencies increased with age within each family. The increasing trend was in general not significantly different among families. The increase in individual aberration was closely correlated with age and cumulative dose. Age-and dose-effect relationship fit well the linear equation: Y = 0.0448X + 0.4913 (R 2 = 0.7814) for age and Y 0.0156X + 0.5715 (R 2 = 0.7061) for cumulative dose, respectively. In the case of CA, there was no significant difference in aberration yields among individuals of different ages, and the group mean aberration frequency was 1.24 +- 0.69 x 10 -3 . Conclusions: Dic and Rc can continuously accumulate over a lifetime chronic low dose exposures, and can serve as a reliable biological indicator. However, the ultimate sensitivity is about 50 mGy

  14. Non-linearity of dose-effect relationship at low level exposure on the example of cytogenetic effects in plant cells

    International Nuclear Information System (INIS)

    Oudalova, A.A.; Geras'kin, S.A.; Dikarev, V.G.; Dikareva, N.S.; Chernonog, E.V.

    2007-01-01

    Complete text of publication follows. There has been an increasing concern in the current scientific society and among the public about the need to protect the environment in order to maintain the ecosystem sustainability and future well-being of man. The linear non-threshold (LNT) hypothesis as the most officially acknowledged concept of biological effect of radiation fails to explain many facts on effects at low level exposures (LLE) accumulated lately. Available information on the dose-effect relationship at low doses is scarce and incomplete for non-human species despite the fact that, under conditions of increased radiation exposure, some biota species occur at a risk of higher impact than humans because of differences in ecological niches occupied. Dose-effect relationships for cytogenetic damage in the range of LLE are studied in a series os experiments with plant (Hordeum vulgare L.) meristem cells. Dose-effect dependences obtained show an obvious non-linear behavior in the LLE region. A piecewise linear model (PLM) for dose-cytogenetic effect relationship that considers an existence of dose-independent part at LLE ('plateau') is developed and specified on the data obtained. An advantage of the PLM over linear model in approximating the frequency of cytogenetic disturbances is demonstrated. From an empirical probability distribution analysis, it is shown that the increase in cytogenetic damage level is tightly connected with changes in a process of absorbed energy distribution between target volumes in terms of fraction of cells experienced a radiation hit event. An appropriateness of the LNT hypothesis to the description of cytogenetic disturbances yield in plant meristem cells in the LLE region is discussed. The results support a conclusion about indirect mechanism of mutagenesis induced by low doses. New data obtained concern a perception of fundamental mechanisms governing cell response to LLE. These findings are of general biological interest, since

  15. Relationship between nitrate reductase and nitrate uptake in phytoplankton in the Peru upwelling region

    International Nuclear Information System (INIS)

    Blasco, D.; MacIsaac, J.J.; Packard, T.T.; Dugdale, R.C.

    1984-01-01

    Nitrate reductase (NR) activity and 15 NO 3 - uptake in phytoplankton were compared under different environmental conditions on two cruises in the upwelling region off Peru. The NR activity and NO 3 - uptake rates responded differently to light and nutrients and the differences led to variations in the uptake: reductase ratio. Analysis of these variations suggests that the re-equilibration time of the two processes in response to environmental perturbation is an important source of variability. The nitrate uptake system responds faster than the nitrate reductase system. Considering these differences in response time the basic differences in the two processes, and the differences in their measurement, the authors conclude that the Nr activity measures the current nitrate-reducing potential, which reflects NO 3 - assimilation before the sampling time, while 15 NO 3 - uptake measures NO 3 - assimilation in the 6-h period following sampling

  16. An explanation for the multiplicative and the additive dose-effect relationship with the single-hit model

    International Nuclear Information System (INIS)

    Kottbauer, M.M.; Fleck, C.M.; Schoellnberger, H.

    1997-01-01

    For solid tumors and for leukemia the excess cancer rate after a single radiation dose D is different. The multiplicative model describes the excess solid tumor probability rate which is proportional to the background rate of cancer and dependent on dose D. The additive model describes the excess probability rate for leukaemia which is proportional to the dose D but unrelated to the spontaneous rate of cancer. A second great difference between the two models is the duration of the increased cancer probability rate. The multiplicative mode predicts that the additional cancer risk persist the whole lifetime after exposure and the additive model predicts excess risk over a period of time. With the Single-hit model (SHM) which is a multistage cancer model both dose-response relationships can be described. It will be shown that only small differences in the derivation will lead to the different relationships. We then analyze the incidence data of leukemia (1950-1987) and of all solid tumors (1958-1987) of the atomic bomb survivors. (author)

  17. The radiological consequences of notional accidental releases of radioactivity from fast breeder reactors: sensitivity to the dose-effect relationships adopted for early biological effects

    International Nuclear Information System (INIS)

    Kelly, G.N.; Simmonds, J.R.; Smith, H.; Stather, J.W.

    1979-07-01

    This study considered the sensitivity to the dose-response relationships adopted for the estimation of early biological effects from notional accidental releases of radioactivity from fast breeder reactors. Two distinct aspects were considered: the sensitivity of the predicted consequences to variation in the dose-mortality relationships for irradiation of the bone marrow and the lung; and the influence of simple supportive medical treatment in reducing the incidence of early deaths in the exposed population. The numbers of early effects estimated in the initial study were relatively insensitive to variation in the dose-mortality relationships within the bounds proposed. The few exceptions concerned releases of particular nuclide composition, and the variation in the predicted consequences could be around an order of magnitude; the absolute numbers of effects however were in general small when the sensitivity was most pronounced. The reduction in the incidence of early deaths when using simple supportive treatment varied markedly with the nuclide composition of the release. Areas of uncertainty were identified where further research and investigation might most profitably be directed with a view to improving the reliability of the dose-effect relationships adopted and hence of the predicted consequences of the release considered. (author)

  18. Cytogenetic effect of low dose gamma-radiation in Hordeum vulgare seedlings: non-linear dose-effect relationship.

    Science.gov (United States)

    Geras'kin, Stanislav A; Oudalova, Alla A; Kim, Jin Kyu; Dikarev, Vladimir G; Dikareva, Nina S

    2007-03-01

    The induction of chromosome aberrations in Hordeum vulgare germinated seeds was studied after ionizing irradiation with doses in the range of 10-1,000 mGy. The relationship between the frequency of aberrant cells and the absorbed dose was found to be nonlinear. A dose-independent plateau in the dose range from about 50 to 500 mGy was observed, where the level of cytogenetic damage was significantly different from the spontaneous level. The comparison of the goodness of the experimental data fitting with mathematical models of different complexity, using the most common quantitative criteria, demonstrated the advantage of a piecewise linear model over linear and polynomial models in approximating the frequency of cytogenetical disturbances. The results of the study support the hypothesis of indirect mechanisms of mutagenesis induced by low doses. Fundamental and applied implications of these findings are discussed.

  19. Phytoplankton diversity in the East China Sea and Yellow Sea measured by PCR-DGGE and its relationships with environmental factors

    Science.gov (United States)

    Sun, Jing; Yu, Zhigang; Gao, Yahui; Zhou, Qianqian; Zhen, Yu; Chen, Hongtao; Zhao, Liyuan; Yao, Qingzhen; Mi, Tiezhu

    2010-03-01

    Relationships between phytoplankton community composition and environmental variables in the East China Sea (ECS) and Yellow Sea (YS) were investigated using geochemical and molecular microbiology methods. The diversity of phytoplankton was characterized using cultivation-independent PCR-based denaturing gradient gel electrophoresis (DGGE). Groups resulting from unweighted pair-group method with arithmetic averages clustering of the DGGE profiles showed good consistency with the eco-environmental characteristics of the sea area they belonged to. Additionally, the clustering results based on DGGE fingerprinting and those based on morphological compositions were practically identical. The relationship of phytoplankton diversity to environmental factors was statistically analyzed. Temperature, dissolved inorganic nitrogen (DIN), and silicate-Si were found significantly related to the phytoplankton community composition. Canonical correspondence analysis (CCA) was performed to reveal the relationship between community composition and these three environmental factors. Generally, values of the ECS are clearly separated from those of the YS in the CCA biplot, due to mainly the effect of temperature and DIN.

  20. Dose-Effect Relationships for the Submandibular Salivary Glands and Implications for Their Sparing by Intensity Modulated Radiotherapy

    International Nuclear Information System (INIS)

    Murdoch-Kinch, Carol-Anne; Kim, Hyugnjin M.; Vineberg, Karen A.; Ship, Jonathan; Eisbruch, Avraham

    2008-01-01

    Purpose: Submandibular salivary glands (SMGs) dysfunction contributes to xerostomia after radiotherapy (RT) of head-and-neck (HN) cancer. We assessed SMG dose-response relationships and their implications for sparing these glands by intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 148 HN cancer patients underwent unstimulated and stimulated SMG salivary flow rate measurements selectively from Wharton's duct orifices, before RT and periodically through 24 months after RT. Correlations of flow rates and mean SMG doses were modeled throughout all time points. IMRT replanning in 8 patients whose contralateral level I was not a target incorporated the results in a new cost function aiming to spare contralateral SMGs. Results: Stimulated SMG flow rates decreased exponentially by (1.2%) Gy as mean doses increased up to 39 Gy threshold, and then plateaued near zero. At mean doses ≤39 Gy, but not higher, flow rates recovered over time at 2.2%/month. Similarly, the unstimulated salivary flow rates decreased exponentially by (3%) Gy as mean dose increased and recovered over time if mean dose was <39 Gy. IMRT replanning reduced mean contralateral SMG dose by average 12 Gy, achieving ≤39 Gy in 5 of 8 patients, without target underdosing, increasing the mean doses to the parotid glands and swallowing structures by average 2-3 Gy. Conclusions: SMG salivary flow rates depended on mean dose with recovery over time up to a threshold of 39 Gy. Substantial SMG dose reduction to below this threshold and without target underdosing is feasible in some patients, at the expense of modestly higher doses to some other organs

  1. Relationship between nitrate reductase and nitrate uptake in phytoplankton in the Peru upwelling region

    International Nuclear Information System (INIS)

    Blasco, D.; MacIsaac, J.J.; Packard, T.T.; Dugdale, R.C.

    1984-01-01

    Nitrate reductase (NR) activity and 15 NO 3 - uptake in phytoplankton were compared under different environmental conditions on two cruises in the upwelling region off Peru. The NR activity and NO 3 - uptake rates responded differently to light and nutrients and the differences led to variations in the uptake:reductase ratio. Analysis of these variations suggests that the re-equilibration time of the two processes in response to environmental perturbation is an important source of variability. The nitrate uptake system responds faster than the nitrate reductase system. Considering these differences in response time, the basic differences in the two processes, and the differences in their measurement, the authors conclude that the NR activity measures the current nitrate-reducing potential, which relfects NO 3 - assimilation before the sampling time, while 15 NO 3 - uptake measures NO 3 - assimilation in the 6-h period following sampling. Thus, considering the sampling time as a point of reference, the former is a measure of the past and the latter is a measure of the future

  2. Variation of particulate organic carbon and its relationship with bio-optical properties during a phytoplankton bloom in the Pearl River estuary

    International Nuclear Information System (INIS)

    Wang Guifen; Zhou Wen; Cao Wenxi; Yin Jianping; Yang Yuezhong; Sun Zhaohua; Zhang Yuanzhi; Zhao Jun

    2011-01-01

    Highlights: → A study about relationship between POC and optical properties during a phytoplankton bloom. → Empirical algorithms for retrieving POC concentration from optical data were developed. → Phytoplankton carbon and it's ratio to Chl-a are estimated and discussed. → Demonstrates that marine optical buoy can be a new platform for monitoring biogeochemical cycle. - Abstract: In this study, variations in the particulate organic carbon (POC) were monitored during a phytoplankton bloom event, and the corresponding changes in bio-optical properties were tracked at one station (114.29 o E, 22.06 o N) located in the Pearl River estuary. A greater than 10-fold increase in POC (112.29-1173.36 mg m -3 ) was observed during the bloom, with the chlorophyll a concentration (Chl-a) varying from 0.984 to 25.941 mg m -3 . A power law function is used to describe the relationship between POC and Chl-a, and the POC:Chl-a ratio tends to change inversely with Chl-a. Phytoplankton carbon concentration is indirectly estimated using the conceptual model proposed by , and this carbon is found to contribute 47.21% (±10.65%) to total POC. The estimated carbon-to-chlorophyll ratio of phytoplankton in diatom-dominated waters is found to be comparable with results reported in the literature. Empirical algorithms for determining the concentrations of Chl-a and POC were developed based on the relationships of these variables with the blue-to-green reflectance ratio. With these bio-optical models, the levels of particulate organic carbon and Chl-a could be predicted from the radiometric data measured by a marine optical buoy, which showed much more detailed information about the variability in biogeochemical parameters during this bloom event.

  3. Indicators: Phytoplankton

    Science.gov (United States)

    Phytoplankton are free-floating, microscopic algae that inhabit the sunlit, upper layer of most freshwater and marine environments. They are usually responsible for the color and clarity of lakes, wetlands, rivers, streams and estuaries.

  4. Dose-effect relationship between the thorium lung burden and the hepatic function of the miners at the Bayan Obo Rare-earth Iron Mine

    International Nuclear Information System (INIS)

    Cheng, Yong-e; Chen, Xing-an

    2008-01-01

    The purpose of this paper is to present the dose effect relationship between the thorium lung burden and the hepatic function of the miners at the Bayun Obo Rare-earth Iron Mine. The methods we used is to carry out the measurement of each miner.s exhaled thoron activity and the thorium lung burden along with the four hepatic functions (thymol turbidity test, glutamic pyruvic transaminase, thymol flocculation test and alkaline phosphatase)of the dust exposed miners in Bayun Obo Rare-earth Iron Mine. We have carried out three investigations in 1983, 1984-1987 and 1994 respectively. Results showed that during the period 1983-1994, 1158 measurements of thorium lung burden estimates and 1158 measurement of every four hepatic functions(altogether 4632 measurements) were performed on 638 dust-exposed miners. No adverse effects were observed. In the same time, none of the above-mentioned 638 exposed miners had a thorium lung burden higher than 11.11 Bq. It is concluded that if any miners. thorium lung burden not higher than 11.11 Bq, his four hepatic functions should not be affected. This first possible threshold for thorium lung burden affecting the hepatic functions was put forward by the authors and confirmed by the Information Center of Chinese Academy of Medical Science in 2003 after searching 23.6 million references. (author)

  5. Anatomical changes in the pharyngeal constrictors after chemo-irradiation of head and neck cancer and their dose-effect relationships: MRI-based study

    International Nuclear Information System (INIS)

    Popovtzer, Aron; Cao Yue; Feng, Felix Y.; Eisbruch, Avraham

    2009-01-01

    Purpose: Dysfunction of pharyngeal constrictors (PCs) after chemo-irradiation of head and neck (HN) cancer has been proposed as major cause of dysphagia. We conducted prospective MRI study to evaluate anatomical changes in the PCs after chemo-irradiation, to gain insight of the mechanism of their dysfunction and their dose-effect relationships. The PCs were compared to the sternocleidomastoid muscles (SCMs), which receive high doses but do not relate to swallowing. Patients and methods: Twelve patients with stage III-IV HN cancer underwent MRI before and 3 months after completing chemo-irradiation. T1- and T2-weighted signals and muscle thickness were evaluated for PCs (superior, middle, and inferior), and SCMs. Mean muscle doses were determined after registration with the planning CT. Results: T1-weighted signals decreased in both PCs and SCMs receiving >50 Gy (p 2 = 0.34, p = 0.01). The T2 signal changes in the PCs were significantly higher than the T2 changes in the SCMs (p 50 Gy gaining significantly more thickness than PCs receiving lesser doses (p = 0.02). In contrast, the SCM thickness decreased post-therapy (p = 0.002). Conclusions: These MRI-based findings, notably the differences between PCs and SCMs, suggest that underlying causes of PC dysfunction are inflammation and edema, likely consequential to acute mucositis affecting the submucosa-lying PCs. These results support reducing mean PC doses to ≤50 Gy, as well as reducing acute mucositis, to improve long-term dysphagia.

  6. Non-Linearity of dose-effect relationship on the example of cytogenetic effects in plant cells at low level exposure to ionising radiation

    International Nuclear Information System (INIS)

    Oudalova, Alla; Geras'kin, Stanislav; Dikarev, Vladimir; Dikareva, Nina; Chernonog, Elena; Copplestone, David; Evseeva, Tatyana

    2006-01-01

    -particles [Nagasawa and Little, 1992; Mothersill et al., 1995]. Other phenomena including genomic instability, low-dose hypersensitivity, and increased radiation resistance effects are also under study [Marples et al., 1997; Kadhim et al., 2004; Bonner, 2004]. The nonlinearity of the dose-effect relationship with low level exposures has been demonstrated in a number of studies where chromosome aberrations were considered as the endpoint of interest. For example, the number of radiation-induced dicentrics in human peripheral blood lymphocytes found in [Pohl-Ruling et al., 1983; Lloyd et al., 1988, 1992] did not exceed the control level at doses below 40 mGy, with some experimental points lying significantly below control values. Essential deviations of chromosome aberrations appearance from linearity in mammals were also shown at higher doses of 100-300 mGy [Luchnik and Sevankaev, 1976; Takahashi et al., 1982]. In other species, deviations of cytogenetic effect induced by low doses from linearity have also been reported. For example, the dose response for cytogenetic effects in Chinese hamster fibroblasts and Vicia faba germs at doses from 0 to 2.5 Gy was shown to be non linear with a plateau at low doses by [Zaichkina et al., 1992]. Dose-effect curves on chromosome aberrations in root meristem cells of Pisum sativum plantlets in the dose range of 0-10 Gy also showed non-linear responses with a plateau for doses up to 1 Gy [Zaka et al., 2002]. However the available information on dose-effect relationships at low doses for non-human species is scarce despite its importance. In their natural environment, some non-human species may be at a higher risk of impact than humans because of differences in ecological niches occupied. [Geras'kin et.al., 2003]. Currently, radiation protection of the environment and maintenance of ecosystem sustainability is of a special concern. and the development of a harmonized approach to human and biota protection has been recognized as a challenge for modern

  7. Non-Linearity of dose-effect relationship on the example of cytogenetic effects in plant cells at low level exposure to ionising radiation

    Energy Technology Data Exchange (ETDEWEB)

    Oudalova, Alla; Geras' kin, Stanislav; Dikarev, Vladimir; Dikareva, Nina; Chernonog, Elena [Russian Institute of Agricultural Radiology and Agroecology, RIARAE, 249032 Obninsk (Russian Federation); Copplestone, David [Environment Agency, Millbank Tower, 25th. Floor, 21/24 Millbank, London, SW1P 4XL (United Kingdom); Evseeva, Tatyana [Institute of Biology, Kommunisticheskaya st., 28 Syktyvkar 167610, Komi Republic (Russian Federation)

    2006-07-01

    alpha-particles [Nagasawa and Little, 1992; Mothersill et al., 1995]. Other phenomena including genomic instability, low-dose hypersensitivity, and increased radiation resistance effects are also under study [Marples et al., 1997; Kadhim et al., 2004; Bonner, 2004]. The nonlinearity of the dose-effect relationship with low level exposures has been demonstrated in a number of studies where chromosome aberrations were considered as the endpoint of interest. For example, the number of radiation-induced dicentrics in human peripheral blood lymphocytes found in [Pohl-Ruling et al., 1983; Lloyd et al., 1988, 1992] did not exceed the control level at doses below 40 mGy, with some experimental points lying significantly below control values. Essential deviations of chromosome aberrations appearance from linearity in mammals were also shown at higher doses of 100-300 mGy [Luchnik and Sevankaev, 1976; Takahashi et al., 1982]. In other species, deviations of cytogenetic effect induced by low doses from linearity have also been reported. For example, the dose response for cytogenetic effects in Chinese hamster fibroblasts and Vicia faba germs at doses from 0 to 2.5 Gy was shown to be non linear with a plateau at low doses by [Zaichkina et al., 1992]. Dose-effect curves on chromosome aberrations in root meristem cells of Pisum sativum plantlets in the dose range of 0-10 Gy also showed non-linear responses with a plateau for doses up to 1 Gy [Zaka et al., 2002]. However the available information on dose-effect relationships at low doses for non-human species is scarce despite its importance. In their natural environment, some non-human species may be at a higher risk of impact than humans because of differences in ecological niches occupied. [Geras'kin et.al., 2003]. Currently, radiation protection of the environment and maintenance of ecosystem sustainability is of a special concern. and the development of a harmonized approach to human and biota protection has been recognized

  8. Optical assessment of phytoplankton nutrient depletion

    DEFF Research Database (Denmark)

    Heath, M.R.; Richardson, Katherine; Kiørboe, Thomas

    1990-01-01

    The ratio of light absorption at 480 and 665 nm by 90% acetone extracts of marine phytoplankton pigments has been examined as a potential indicator of phytoplankton nutritional status in both laboratory and field studies. The laboratory studies demonstrated a clear relationship between nutritiona......-replete and nutrient-depleted cells. The field data suggest that the absorption ratio may be a useful indicator of nutritional status of natural phytoplankton populations, and can be used to augment the interpretation of other data....

  9. Dose-effect relationship for cataract induction after single-dose total body irradiation and bone marrow transplantation for acute leukemia

    International Nuclear Information System (INIS)

    Kempen-Harteveld, M. Loes van; Belkacemi, Yazid; Kal, Henk B.; Labopin, Myriam; Frassoni, Francesco

    2002-01-01

    Purpose: To determine a dose-effect relationship for cataract induction, the tissue-specific parameter, α/β, and the rate of repair of sublethal damage, μ value, in the linear-quadratic formula have to be known. To obtain these parameters for the human eye lens, a large series of patients treated with different doses and dose rates is required. The data of patients with acute leukemia treated with single-dose total body irradiation (STBI) and bone marrow transplantation (BMT) collected by the European Group for Blood and Marrow Transplantation were analyzed. Methods and Materials: The data of 495 patients who underwent BMT for acute leukemia, who had STBI as part of their conditioning regimen, were analyzed using the linear-quadratic concept. The end point was the incidence of cataract formation after BMT. Of the analyzed patients, 175 were registered as having cataracts. Biologic effective doses (BEDs) for different sets of values for α/β and μ were calculated for each patient. With Cox regression analysis, using the overall chi-square test as the parameter evaluating the goodness of fit, α/β and μ values were found. Risk factors for cataract induction were the BED of the applied TBI regimen, allogeneic BMT, steroid therapy for >14 weeks, and heparin administration. To avoid the influence of steroid therapy and heparin on cataract induction, patients who received steroid or heparin treatment were excluded, leaving only the BED as a risk factor. Next, the most likely set of α/β and μ values was obtained. With this set, the cataract-free survival rates were calculated for specific BED intervals, according to the Kaplan-Meier method. From these calculations, cataract incidences were obtained as function of the BED at 120 months after STBI. Results: The use of BED instead of the TBI dose enabled the incidence of cataract formation to be predicted in a reasonably consistent way. With Cox regression analysis for all STBI data, a maximal chi-square value was

  10. Large Scale Variability of Phytoplankton Blooms in the Arctic and Peripheral Seas: Relationships with Sea Ice, Temperature, Clouds, and Wind

    Science.gov (United States)

    Comiso, Josefino C.; Cota, Glenn F.

    2004-01-01

    Spatially detailed satellite data of mean color, sea ice concentration, surface temperature, clouds, and wind have been analyzed to quantify and study the large scale regional and temporal variability of phytoplankton blooms in the Arctic and peripheral seas from 1998 to 2002. In the Arctic basin, phytoplankton chlorophyll displays a large symmetry with the Eastern Arctic having about fivefold higher concentrations than those of the Western Arctic. Large monthly and yearly variability is also observed in the peripheral seas with the largest blooms occurring in the Bering Sea, Sea of Okhotsk, and the Barents Sea during spring. There is large interannual and seasonal variability in biomass with average chlorophyll concentrations in 2002 and 2001 being higher than earlier years in spring and summer. The seasonality in the latitudinal distribution of blooms is also very different such that the North Atlantic is usually most expansive in spring while the North Pacific is more extensive in autumn. Environmental factors that influence phytoplankton growth were examined, and results show relatively high negative correlation with sea ice retreat and strong positive correlation with temperature in early spring. Plankton growth, as indicated by biomass accumulation, in the Arctic and subarctic increases up to a threshold surface temperature of about 276-277 degree K (3-4 degree C) beyond which the concentrations start to decrease suggesting an optimal temperature or nutrient depletion. The correlation with clouds is significant in some areas but negligible in other areas, while the correlations with wind speed and its components are generally weak. The effects of clouds and winds are less predictable with weekly climatologies because of unknown effects of averaging variable and intermittent physical forcing (e.g. over storm event scales with mixing and upwelling of nutrients) and the time scales of acclimation by the phytoplankton.

  11. Climatologic relationship of the superficial temperature of the Colombian Pacific on the marine phytoplankton, during The Boy 1991-92

    International Nuclear Information System (INIS)

    Francisco A Castillo G; David Osorio

    1994-01-01

    The analysis was carried out in the geographical area for the ERFEN understood among the 2 degrade at the 6 degrade of latitude N and 82 degrade of longitude W, specifically in the areas to the north of the Colombian Pacific (Cabo Corrientes) Profile Buenaventura-Malpelo and Profile Tumaco, being studied the superficial phytoplankton in the two characteristic times of the Pacific and taking like reference the existent historical data. The Incidence of the environmental parameter is presented, as it is the temperature on the distribution of a marine ecosystem as it is the superficial marine phytoplankton. It was observed that the identified species as the biological Indicators of the southeastern oscillation, coincided equally with the beginning of the indicative thermal anomalies of the evolution of a warm event with the obtained data it was visualized that the composition of the opposing phytoplankton during the period of study, reflective a mixture of elements with very diverse ecological width, reflecting waters of different provenience: Coastal and oceanic. Bigger information is contributed with the end to supplement the knowledge on the indicative organisms that detect in early form the environmental changes taken place by the phenomenon El Nino, and of this form, to complete the physical-chemical and fishing studies allowing to give approaches in the political orientation in the activities that could be affected, such as fishing strategy, measures on aquiculture, marketing decision, handling of hydrobiologic resources, etc

  12. Dysphagia disorders in patients with cancer of the oropharynx are significantly affected by the radiation therapy dose to the superior and middle constrictor muscle: A dose-effect relationship

    International Nuclear Information System (INIS)

    Levendag, Peter C.; Teguh, David N.; Voet, Peter; Est, Henri van der; Noever, Inge; Kruijf, Wilhelmus J.M. de; Kolkman-Deurloo, Inger-Karine; Prevost, Jean-Briac; Poll, Johan; Schmitz, Paul I.M.; Heijmen, Ben J.

    2007-01-01

    Purpose/Objective: To assess the relationship between the radiation therapy (RT) dose received by the muscular components of the swallowing (sw) apparatus and - dysphagia related - quality of life (QoL) in oropharyngeal cancer. Materials/Methods: Between 2000 and 2005, 81 patients with SCC of the oropharynx were treated by 3DCRT or IMRT, with or without concomitant chemotherapy (CHT); 43 out of these 81 patients were boosted by brachytherapy (BT). Charts of 81 patients were reviewed with regard to late dysphagia complaints; 23% experienced severe dysphagia. Seventeen patients expired. Fifty-six out of 64 (88%) responded to quality of life (QoL) questionnaires; that is, the Performance Status Scales of List, EORTC H and N35, and the M.D. Anderson Dysphagia Inventory. The superior (scm), middle (mcm), and inferior constrictor muscle (icm), the cricopharyngeus muscle and the inlet of the esophagus, are considered of paramount importance for swallowing. The mean dose was calculated in the muscular structures. Univariate analysis and multivariate analysis were performed using the proportional odds model. Results: Mean follow-up was 18 months (range 2-34) for IMRT, and 46 months for 3DCRT (range 2-72). At 3-years, a LRC of 84%, DFS of 78% and OS of 77% were observed. A significant correlation was observed between the mean dose in the scm and mcm, and severe dysphagia complaints (univariate analysis). A steep dose-effect relationship, with an increase of the probability of dysphagia of 19% with every additional 10 Gy, was established. In the multivariate analysis, BT (dose) was the only significant factor. Conclusion: A dose-effect relationship between dose and swallowing complaints was observed. One way to improve the QoL is to constrain the dose to be received by the swallowing muscles

  13. Increasing phytoplankton-available phosphorus and inhibition of macrophyte on phytoplankton bloom.

    Science.gov (United States)

    Dai, Yanran; Wu, Juan; Ma, Xiaohang; Zhong, Fei; Cui, Naxin; Cheng, Shuiping

    2017-02-01

    We assembled mesocosms to address the coherent mechanisms that an increasing phosphorus (P) concentration in water columns coupled with the phytoplankton bloom and identify the performance gap of regulating phytoplankton growth between two macrophyte species, Ceratophyllum demersum L. and Vallisneria spiralis L. Intense alkaline phosphatase activities (APA) were observed in the unplanted control, with their predominant part, phytoplankton APA (accounting for up to 44.7% of the total APA), and another large share, bacterial APA. These correspond with the large average concentration of total phosphorus (TP), total dissolved phosphorus (TDP) and soluble reactive (SRP) as well as high phytoplankton density in the water column. The consistency among P concentrations, phytoplankton density and APA, together with the positive impact of phytoplankton density on total APA revealed by the structural equation modelling (SEM), indicates that facilitated APA levels in water is an essential strategy for phytoplankton to enhance the available P. Furthermore, a positive interaction between phytoplankton APA and bacteria APA was detected, suggesting a potential collaboration between phytoplankton and bacteria to boost available P content in the water column. Both macrophyte species had a prominent performance on regulating phytoplankton proliferation. The phytoplankton density and quantum yield in C. demersum systems were all significantly lower (33.8% and 24.0%) than those in V. spiralis systems. Additionally, a greater decoupling effect of C. demersum on the relationship between P, APA, phytoplankton density, bacteria dynamic and quantum yield was revealed by SEM. These results imply that the preferred tactic of different species could lead to the performance gap. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Dose-effect relationships for fife shortening, tumorigenesis, and systemic injuries in mice irradiated with fission neutron or 60Co gamma radiation

    International Nuclear Information System (INIS)

    Ainsworth, E.J.; Fry, R.J.M.; Williamson, F.S.; Brennan, P.C.; Stearner, S.P.; Yang, V.V.; Crouse, D.A.; Rust, J.H.; Borak, T.B.

    1977-01-01

    The objective of this research is to provide additional data on life shortening, neoplastic and non-neoplastic diseases, and other systematic injuries necessary for the determination of dose-response relationships. The data are used to test existing predictive models and formulate new models which may assist with radiation risk assessment. Late somatic effects of fission neutrons from the JANUS reactor or from cobalt-60 gamma radiation are evaluated in young adult B6CF 1 mice that receive either a range of single doses or protracted doses at low dose rates; the protracted irradiation is administered over a 6-month period. After single doses of gamma radiation the relationship between radiation dose and percent life shortening appears linear whereas after single doses of fission spectrum neutrons a non-linear dose response is observed. These results suggest that estimates of radiation risk for fission spectrum neutrons should take into account the following: the curvilinearity of the neutron dose-response curve for life shortening, and the increased life shortening produced by neutron dose fractionation

  15. Intensity-Modulated Radiotherapy of Head and Neck Cancer Aiming to Reduce Dysphagia: Early Dose-Effect Relationships for the Swallowing Structures

    International Nuclear Information System (INIS)

    Feng, Felix Y.; Kim, Hyungjin M.; Lyden, Teresa H.; Haxer, Marc J.; Feng, Mary; Worden, Frank P.; Chepeha, Douglas B.; Eisbruch, Avraham

    2007-01-01

    Purpose: To present initial results of a clinical trial of intensity-modulated radiotherapy (IMRT) aiming to spare the swallowing structures whose dysfunction after chemoradiation is a likely cause of dysphagia and aspiration, without compromising target doses. Methods and Materials: This was a prospective, longitudinal study of 36 patients with Stage III-IV oropharyngeal (31) or nasopharyngeal (5) cancer. Definitive chemo-IMRT spared salivary glands and swallowing structures: pharyngeal constrictors (PC), glottic and supraglottic larynx (GSL), and esophagus. Lateral but not medial retropharyngeal nodes were considered at risk. Dysphagia endpoints included objective swallowing dysfunction (videofluoroscopy), and both patient-reported and observer-rated scores. Correlations between doses and changes in these endpoints from pre-therapy to 3 months after therapy were assessed. Results: Significant correlations were observed between videofluoroscopy-based aspirations and the mean doses to the PC and GSL, as well as the partial volumes of these structures receiving 50-65 Gy; the highest correlations were associated with doses to the superior PC (p = 0.005). All patients with aspirations received mean PC doses >60 Gy or PC V 65 >50%, and GSL V 50 >50%. Reduced laryngeal elevation and epiglottic inversion were correlated with mean PC and GSL doses (p 70 >50%. Worsening patient-reported liquid swallowing was correlated with mean PC (p = 0.05) and esophageal (p 0.02) doses. Only mean PC doses were correlated with worsening patient-reported solid swallowing (p = 0.04) and observer-rated swallowing scores (p = 0.04). Conclusions: These dose-volume-effect relationships provide initial IMRT optimization goals and motivate further efforts to reduce swallowing structures doses to reduce dysphagia and aspiration

  16. Dysphagia and trismus after concomitant chemo-Intensity-Modulated Radiation Therapy (chemo-IMRT) in advanced head and neck cancer; dose-effect relationships for swallowing and mastication structures.

    Science.gov (United States)

    van der Molen, Lisette; Heemsbergen, Wilma D; de Jong, Rianne; van Rossum, Maya A; Smeele, Ludi E; Rasch, Coen R N; Hilgers, Frans J M

    2013-03-01

    Prospective assessment of dysphagia and trismus in chemo-IMRT head and neck cancer patients in relation to dose-parameters of structures involved in swallowing and mastication. Assessment of 55 patients before, 10-weeks (N=49) and 1-year post-treatment (N=37). Calculation of dose-volume parameters for swallowing (inferior (IC), middle (MC), and superior constrictors (SC)), and mastication structures (e.g. masseter). Investigation of relationships between dose-parameters and endpoints for swallowing problems (videofluoroscopy-based laryngeal Penetration-Aspiration Scale (PAS), and study-specific structured questionnaire) and limited mouth-opening (measurements and questionnaire), taking into account baseline scores. At 10-weeks, volume of IC receiving ≥60 Gy (V60) and mean dose IC were significant predictors for PAS. One-year post-treatment, reported problems with swallowing solids were significantly related to masseter dose-parameters (mean, V20, V40 and V60) and an inverse relationship (lower dose related to a higher probability) was observed for V60 of the IC. Dose-parameters of masseter and pterygoid muscles were significant predictors of trismus at 10-weeks (mean, V20, and V40). At 1-year, dose-parameters of all mastication structures were strong predictors for subjective mouth-opening problems (mean, max, V20, V40, and V60). Dose-effect relationships exist for dysphagia and trismus. Therefore treatment plans should be optimized to avoid these side effects. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  17. Dose--effect relationships for femoral fractures after multimodality limb-sparing therapy of soft-tissue sarcomas of the proximal lower extremity.

    Science.gov (United States)

    Pak, Daniel; Vineberg, Karen A; Griffith, Kent A; Sabolch, Aaron; Chugh, Rashmi; Ben-Josef, Edgar; Biermann, Janet Sybil; Feng, Mary

    2012-07-15

    We investigated the clinical and dosimetric predictors for radiation-associated femoral fractures in patients with proximal lower extremity soft tissue sarcomas (STS). We examined 131 patients with proximal lower extremity STS who received limb-sparing surgery and external-beam radiation therapy between 1985 and 2006. Five (4%) patients sustained pathologic femoral fractures. Dosimetric analysis was limited to 4 fracture patients with full three-dimensional dose information, who were compared with 59 nonfracture patients. The mean doses and volumes of bone (V(d)) receiving specified doses (≥30 Gy, 45 Gy, 60 Gy) at the femoral body, femoral neck, intertrochanteric region, and subtrochanteric region were compared. Clinical predictive factors were also evaluated. Of 4 fracture patients in our dosimetric series, there were three femoral neck fractures with a mean dose of 57.6 ± 8.9 Gy, V30 of 14.5 ± 2.3 cc, V45 of 11.8 ± 1.1 cc, and V60 of 7.2 ± 2.2 cc at the femoral neck compared with 22.9 ± 20.8 Gy, 4.8 ± 5.6 cc, 2.5 ± 3.9 cc, and 0.8 ± 2.7 cc, respectively, for nonfracture patients (p fracture rate was higher than at the subtrochanteric region despite lower mean doses at these subregions. All fracture sites received mean doses greater than 40 Gy. Also, with our policy of prophylactic femoral intramedullary nailing for high-risk patients, there was no significant difference in fracture rates between patients with and without periosteal excision. There were no significant differences in age, sex, tumor size, timing of radiation therapy, and use of chemotherapy between fracture and nonfracture patients. These dose-volume toxicity relationships provide RT optimization goals to guide future efforts for reducing pathologic fracture rates. Prophylactic femoral intramedullary nailing may also reduce fracture risk for susceptible patients. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Dose-Effect Relationships for Femoral Fractures After Multimodality Limb-Sparing Therapy of Soft-Tissue Sarcomas of the Proximal Lower Extremity

    Energy Technology Data Exchange (ETDEWEB)

    Pak, Daniel; Vineberg, Karen A. [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Griffith, Kent A. [Biostatistics Unit, Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI (United States); Sabolch, Aaron [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Chugh, Rashmi [Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI (United States); Ben-Josef, Edgar [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Biermann, Janet Sybil [Department of Orthopedic Surgery, University of Michigan, Ann Arbor, MI (United States); Feng, Mary, E-mail: maryfeng@umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States)

    2012-07-15

    Purpose: We investigated the clinical and dosimetric predictors for radiation-associated femoral fractures in patients with proximal lower extremity soft tissue sarcomas (STS). Methods and Materials: We examined 131 patients with proximal lower extremity STS who received limb-sparing surgery and external-beam radiation therapy between 1985 and 2006. Five (4%) patients sustained pathologic femoral fractures. Dosimetric analysis was limited to 4 fracture patients with full three-dimensional dose information, who were compared with 59 nonfracture patients. The mean doses and volumes of bone (V{sub d}) receiving specified doses ({>=}30 Gy, 45 Gy, 60 Gy) at the femoral body, femoral neck, intertrochanteric region, and subtrochanteric region were compared. Clinical predictive factors were also evaluated. Results: Of 4 fracture patients in our dosimetric series, there were three femoral neck fractures with a mean dose of 57.6 {+-} 8.9 Gy, V30 of 14.5 {+-} 2.3 cc, V45 of 11.8 {+-} 1.1 cc, and V60 of 7.2 {+-} 2.2 cc at the femoral neck compared with 22.9 {+-} 20.8 Gy, 4.8 {+-} 5.6 cc, 2.5 {+-} 3.9 cc, and 0.8 {+-} 2.7 cc, respectively, for nonfracture patients (p < 0.03 for all). The femoral neck fracture rate was higher than at the subtrochanteric region despite lower mean doses at these subregions. All fracture sites received mean doses greater than 40 Gy. Also, with our policy of prophylactic femoral intramedullary nailing for high-risk patients, there was no significant difference in fracture rates between patients with and without periosteal excision. There were no significant differences in age, sex, tumor size, timing of radiation therapy, and use of chemotherapy between fracture and nonfracture patients. Conclusions: These dose-volume toxicity relationships provide RT optimization goals to guide future efforts for reducing pathologic fracture rates. Prophylactic femoral intramedullary nailing may also reduce fracture risk for susceptible patients.

  19. Phytoplankton biovolume is independent from the slope of the size spectrum in the oligotrophic atlantic ocean

    KAUST Repository

    Moreno-Ostos, Enrique; Blanco, José Marí a; Agusti, Susana; Lubiá n, Luis M.; Rodrí guez, Valeriano; Palomino, Roberto L.; Llabré s, Moira; Rodrí guez, Jaime

    2015-01-01

    high phytoplankton biovolume in productive regions with flatter spectrum slope and the opposite in oligotrophic ecosystems. Rather than this, the relationship between high biovolume phytoplankton assemblages and flatter size-abundance spectra does

  20. uv keratoconjunctivitis vs. established dose effect relationships

    International Nuclear Information System (INIS)

    Gulvady, N.U.

    1976-01-01

    A patient who received a uv dose to his eyes 11 times greater than the photokeratitic threshold of Pitts and 4 1 / 2 times the photokeratitic threshold as found by Leach. The patient had severe keratoconjunctivitis for 3 days and did not develop any keratitis

  1. Sea Soup: Phytoplankton.

    Science.gov (United States)

    Cerullo, Mary M.

    This guide, designed for students in grades 3-7, answers intriguing questions about phytoplankton, tiny drifters that have shaped our world. Invisible to the naked eye, phytoplankton are the source of our atmosphere, our climate, our ocean food chain, much of our oil supply, and more. They're also food for zooplankton. Photomicroscopy serves up…

  2. Seasonal Variability of Phytoplankton Population in the Brahmani ...

    African Journals Online (AJOL)

    Seasonal Variability of Phytoplankton Population in the Brahmani Estuary of Orissa, India. S Palleyi, RN Kar, CR Panda. Abstract. The dynamic relationship of water physico-chemical characteristics with phytoplankton has long been of great interest in both experimental ecology and environmental management. This study ...

  3. Monitoring natural phytoplankton communities

    DEFF Research Database (Denmark)

    Haraguchi, L.; Jakobsen, H. H.; Lundholm, Nina

    2017-01-01

    The phytoplankton community can vary within hours (physiology) to years (climatic and anthropogenic responses), and monitoring at different timescales is relevant for understanding community functioning and assessing changes. However, standard techniques used in monitoring programmes are time...

  4. Phytoplankton Monitoring Network (PMN)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Phytoplankton Monitoring Network (PMN) is a part of the National Centers for Coastal Ocean Science (NCCOS). The PMN was created as an outreach program to connect...

  5. Phytoplankton and Climate

    Science.gov (United States)

    Moisan, John R.

    2009-01-01

    Ocean phytoplankton supply about half of the oxygen that humans utilize to sustain life. In this lecture, we will explore how phytoplankton plays a critical role in modulating the Earth's climate. These tiny organisms are the base of the Ocean's food web. They can modulate the rate at which solar heat is absorbed by the ocean, either through direct absorption or through production of highly scattering cellular coverings. They take up and help sequester carbon dioxide, a key greenhouse gas that modulated the Earth's climate. They are the source of cloud nucleation gases that are key to cloud formation/processes. They are also able to modify the nutrient budgets of the ocean through active uptake of inert atmospheric nitrogen. Climate variations have a pronounced impact on phytoplankton dynamics. Long term variations in the climate have been studied through geological interpretations on its influence on phytoplankton populations. The presentation will focus on presenting the numerous linkages that have been observed between climate and phytoplankton and further discuss how present climate change scenarios are likely to impact phytoplankton populations as well as present findings from several studies that have tried to understand how the climate might react to the feedbacks from these numerous climate-phytop|ankton linkages.

  6. Low-dose effect on blood chromosomes

    International Nuclear Information System (INIS)

    Pohl-Rueling, J.

    1992-01-01

    Linear dose response relationships of biological effects at low doses are experimentally and theoretically disputed. Structural chromosome aberration rates at doses ranging from normal background exposures up to about 30 mGy/yr in vivo and up to 50 mGy in vitro were investigated by the author and other scientists. Results are comparable and dose effect curves reveal following shapes; within the normal burden and up to 2-10 mGy/yr in vivo rates they increase sharply to about 3-6 times the lowest values; subsequent doses either from natural, occupational or accidental exposures up to about 30 mGy/yr yield either constant aberration rates, assuming a plateau, or perhaps even a decrease. In vitro experiments show comparable results up to 50 mGy. Other biological effects seem to have similar dose dependencies. The non-linearity of low-dose effects can be explained by induction of repair enzymes at certain damage to the DNA. This hypothesis is sustained experimentally and theoretically by several papers in literature. (author). 14 refs., 5 figs

  7. Limnoperna fortunei Dunker, 1857 larvae in different environments of a Neotropical floodplain: relationships of abiotic variables and phytoplankton with different stages of development

    Directory of Open Access Journals (Sweden)

    J. Ernandes-Silva

    Full Text Available Abstract Limnoperna fortunei Dunker, 1857 is an Asian invasive freshwater bivalve. Although there need to contain their spread, studies about the biology of the larvae are scarce. We correlated the larval stages of L. fortunei with biotic factors such as phytoplankton and main abiotic variables in lotic environments of the Upper Paraná River floodplain. The four samples were taken quarterly during the year 2012. The Principal component analysis (PCA showed only spatial differences, as did a Canonical Correspondence Analysis (CCA. High densities of larvae were recorded in all samples the Paraná River and Baía River only in December, especially those in their initial stage. In the biovolume of Class of algae, Bacillarophyceae showed the highest value, but Chlorophycea who was strongly correlated with the density of D-stage larvae. The large variety of phytoplankton, especially microplankton Chlorophyceae, high values of PO4, NH4 and temperature were positively correlated with high densities of D-stage larvae. We conclude that high temperature, and food availability, indicated by phytoplankton community, favored the reproduction of L. fortunei and enhance the ability of specie dispersion due to the increase in the emission of propagules. Therefore, studies that address the biology of golden mussel larvae should be performed in order to prevent its spread.

  8. Metabolic dose-effect relationships of different Pt compounds on growing, pregnant, and lactating rats; Metabolische Dosis-Wirkungsbeziehungen verschiedener Pt-Verbindungen bei wachsenden, graviden und laktierenden Ratten (VPT 04)

    Energy Technology Data Exchange (ETDEWEB)

    Eder, K; Kirchgessner, M [Technische Univ. Muenchen, Freising (Germany). Lehrstuhl fuer Tierernaehrung

    1998-12-31

    The fact that humans can take up platinum via the food chain calls for an investigation of the effects of platinum ingestion on the organism. For this purpose a study was carried out on the dose-effect relationships of various platinum compounds using the rat as a model. To take due account of different physiological stages the study included growing, pregnant, and lactating rats. According to present knowledge platinum is primarily emitted in its elemental form by the catalytic converter, i.e. with the formal oxidation number zero, and to a lesser degree in ionic form. Beside elemental platinum the study therefore also involved exposure to PtCl{sub 2} and PtCl{sub 4}. Furthermore, to do justice to the fact that humans and animals take up platinum not only from its primary source but also from plants in the food chain, platinum was also administered as a Pt-II-phytochelatin complex previously isolated from Pt-contaminated material. Study criteria were chosen with a view to obtaining a general indication of potential toxic effects and included parameters such as the live weight curve, haematological status, and platinum accumulation in the body or in specific organs. Of particular interest in pregnant and lactating rats were platinum levels in foetuses and milk. [Deutsch] Ueber die Nahrungskette ist eine alimentaere Aufnahme von Platin durch den Menschen moeglich und erfordert, die Auswirkungen der ingestiven Platinzufuhr auf den Organismus zu untersuchen. Deshalb wurden am Modelltier Ratte Studien zur Dosis-Wirkungsbeziehung verschiedener Platinverbindungen durchgefuehrt. Um den verschiedenen physiologischen Stadien gerecht zu werden, wurden sowohl wachsende wie auch gravide und laktierende Ratten in die Studien einbezogen. Soweit bislang bekannt, wird Platin vorwiegend in der formalen Oxidationsstufe Null als elementares Platin, zu einem geringeren Anteil aber auch in ionischer Form aus der Katalysatoreinheit ausgetragen. Deshalb wurden in den vorliegenden

  9. Metabolic dose-effect relationships of different Pt compounds on growing, pregnant, and lactating rats; Metabolische Dosis-Wirkungsbeziehungen verschiedener Pt-Verbindungen bei wachsenden, graviden und laktierenden Ratten (VPT 04)

    Energy Technology Data Exchange (ETDEWEB)

    Eder, K.; Kirchgessner, M. [Technische Univ. Muenchen, Freising (Germany). Lehrstuhl fuer Tierernaehrung

    1997-12-31

    The fact that humans can take up platinum via the food chain calls for an investigation of the effects of platinum ingestion on the organism. For this purpose a study was carried out on the dose-effect relationships of various platinum compounds using the rat as a model. To take due account of different physiological stages the study included growing, pregnant, and lactating rats. According to present knowledge platinum is primarily emitted in its elemental form by the catalytic converter, i.e. with the formal oxidation number zero, and to a lesser degree in ionic form. Beside elemental platinum the study therefore also involved exposure to PtCl{sub 2} and PtCl{sub 4}. Furthermore, to do justice to the fact that humans and animals take up platinum not only from its primary source but also from plants in the food chain, platinum was also administered as a Pt-II-phytochelatin complex previously isolated from Pt-contaminated material. Study criteria were chosen with a view to obtaining a general indication of potential toxic effects and included parameters such as the live weight curve, haematological status, and platinum accumulation in the body or in specific organs. Of particular interest in pregnant and lactating rats were platinum levels in foetuses and milk. [Deutsch] Ueber die Nahrungskette ist eine alimentaere Aufnahme von Platin durch den Menschen moeglich und erfordert, die Auswirkungen der ingestiven Platinzufuhr auf den Organismus zu untersuchen. Deshalb wurden am Modelltier Ratte Studien zur Dosis-Wirkungsbeziehung verschiedener Platinverbindungen durchgefuehrt. Um den verschiedenen physiologischen Stadien gerecht zu werden, wurden sowohl wachsende wie auch gravide und laktierende Ratten in die Studien einbezogen. Soweit bislang bekannt, wird Platin vorwiegend in der formalen Oxidationsstufe Null als elementares Platin, zu einem geringeren Anteil aber auch in ionischer Form aus der Katalysatoreinheit ausgetragen. Deshalb wurden in den vorliegenden

  10. Multicellular Features of Phytoplankton

    Directory of Open Access Journals (Sweden)

    Adi Abada

    2018-04-01

    Full Text Available Microscopic marine phytoplankton drift freely in the ocean, harvesting sunlight through photosynthesis. These unicellular microorganisms account for half of the primary productivity on Earth and play pivotal roles in the biogeochemistry of our planet (Field et al., 1998. The major groups of microalgae that comprise the phytoplankton community are coccolithophores, diatoms and dinoflagellates. In present oceans, phytoplankton individuals and populations are forced to rapidly adjust, as key chemical and physical parameters defining marine habitats are changing globally. Here we propose that microalgal populations often display the characteristics of a multicellular-like community rather than a random collection of individuals. Evolution of multicellularity entails a continuum of events starting from single cells that go through aggregation or clonal divisions (Brunet and King, 2017. Phytoplankton may be an intermediate state between single cells and aggregates of physically attached cells that communicate and co-operate; perhaps an evolutionary snapshot toward multicellularity. In this opinion article, we journey through several studies conducted in two key phytoplankton groups, coccolithophores and diatoms, to demonstrate how observations in these studies could be interpreted in a multicellular context.

  11. Monitoring natural phytoplankton communities

    DEFF Research Database (Denmark)

    Haraguchi, L.; Jakobsen, H. H.; Lundholm, Nina

    2017-01-01

    -consuming and/or expensive, limiting sampling frequency. The use of faster methods, such as flow cytometry, has become more frequent in phytoplankton studies, although comparisons between this technique and traditional ones are still scarce. This study aimed to assess if natural phytoplankton communities...... carbon biomass with PFCM, applying the same conversion factors as for microscopy. Biomasses obtained with PFCM, estimated from live cells, were higher than microscopy for natural samples. We conclude that PFCM results are comparable to classical techniques, yet the data from PFCM had poor taxonomic...

  12. Studies on Antarctic phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Pant, A.

    Ice-edge data from a single polynya station at 70 degrees S 11 degrees E over a 2-month period is assessed in relation to previously published work in similar environments. The phytoplankton community seems to be composed of 2 quite different...

  13. Global Ocean Phytoplankton

    Science.gov (United States)

    Franz, B. A.; Behrenfeld, M. J.; Siegel, D. A.; Werdell, P. J.

    2014-01-01

    Marine phytoplankton are responsible for roughly half the net primary production (NPP) on Earth, fixing atmospheric CO2 into food that fuels global ocean ecosystems and drives the ocean's biogeochemical cycles. Phytoplankton growth is highly sensitive to variations in ocean physical properties, such as upper ocean stratification and light availability within this mixed layer. Satellite ocean color sensors, such as the Sea-viewing Wide Field-of-view Sensor (SeaWiFS; McClain 2009) and Moderate Resolution Imaging Spectroradiometer (MODIS; Esaias 1998), provide observations of sufficient frequency and geographic coverage to globally monitor physically-driven changes in phytoplankton distributions. In practice, ocean color sensors retrieve the spectral distribution of visible solar radiation reflected upward from beneath the ocean surface, which can then be related to changes in the photosynthetic phytoplankton pigment, chlorophyll- a (Chla; measured in mg m-3). Here, global Chla data for 2013 are evaluated within the context of the 16-year continuous record provided through the combined observations of SeaWiFS (1997-2010) and MODIS on Aqua (MODISA; 2002-present). Ocean color measurements from the recently launched Visible and Infrared Imaging Radiometer Suite (VIIRS; 2011-present) are also considered, but results suggest that the temporal calibration of the VIIRS sensor is not yet sufficiently stable for quantitative global change studies. All MODISA (version 2013.1), SeaWiFS (version 2010.0), and VIIRS (version 2013.1) data presented here were produced by NASA using consistent Chla algorithms.

  14. Photoreception in Phytoplankton.

    Science.gov (United States)

    Colley, Nansi Jo; Nilsson, Dan-Eric

    2016-11-01

    In many species of phytoplankton, simple photoreceptors monitor ambient lighting. Photoreceptors provide a number of selective advantages including the ability to assess the time of day for circadian rhythms, seasonal changes, and the detection of excessive light intensities and harmful UV light. Photoreceptors also serve as depth gauges in the water column for behaviors such as diurnal vertical migration. Photoreceptors can be organized together with screening pigment into visible eyespots. In a wide variety of motile phytoplankton, including Chlamydomonas, Volvox, Euglena, and Kryptoperidinium, eyespots are light-sensitive organelles residing within the cell. Eyespots are composed of photoreceptor proteins and typically red to orange carotenoid screening pigments. This association of photosensory pigment with screening pigment allows for detection of light directionality, needed for light-guided behaviors such as positive and negative phototaxis. In Chlamydomonas, the eyespot is located in the chloroplast and Chlamydomonas expresses a number of photosensory pigments including the microbial channelrhodopsins (ChR1 and ChR2). Dinoflagellates are unicellular protists that are ecologically important constituents of the phytoplankton. They display a great deal of diversity in morphology, nutritional modes and symbioses, and can be photosynthetic or heterotrophic, feeding on smaller phytoplankton. Dinoflagellates, such as Kryptoperidinium foliaceum, have eyespots that are used for light-mediated tasks including phototaxis. Dinoflagellates belonging to the family Warnowiaceae have a more elaborate eye. Their eye-organelle, called an ocelloid, is a large, elaborate structure consisting of a focusing lens, highly ordered retinal membranes, and a shield of dark pigment. This complex eye-organelle is similar to multicellular camera eyes, such as our own. Unraveling the molecular makeup, structure and function of dinoflagellate eyes, as well as light-guided behaviors in

  15. PHYTOPLANKTON OF CASPIAN

    Directory of Open Access Journals (Sweden)

    Aysha Sharapatinovna Gasanova

    2015-01-01

    Full Text Available Aim. The composition of the species of the phytoplankton in the Russian sector of the Caspian Sea in conditions of transgression, anthropogenic and chemical contamination has been studied.Location.The Russian sector of the Caspian SeaMethods. The phytoplankton samples were collected at the depths of 8 – 50m by the use of the Nansen bathometer and subsequently were fixed in 4% formalin. The office processing was carried out in a box of Nozhotta type, which has the volume of 0.1 ml and the triplicate surface, under the light microscope of Biolam P15. The system of domestic diamotologists was used during the classification of Bacillariaphyta, as for the classification of Dinophyta, the Dodge scheme was applied. Cyanophyta algae were classified according to the system of A.A. Elenkina with the amendments adopted by A.I. Proshkin-Lavrenko and V.V. Makarova. The classification of the Chlorophyta division has been done according to the Smith system.Results, main conclusions. Presented the taxonomic structure and the lists of species of the phytoplankton community in the sea coastal shallow waters Russian sector of the Caspian Sea have been presented. A high floristic diversity and domination of small cell forms are characteristics of the modern structure of the coastal shoal waters of the Dagestan part of the Caspian Sea. The auttaclimatizant of 1934, Pseudosolenia calcaravis, has not been discovered in the plankton of the researched water area. The phytoplankton community has been represented by 58 species of six groups: Cyanophyta, Bacillariaphyta, Dinophyta, Euglenophyta, Chlorophyta and the small flagellate. Bacillariaphyta were the basis of both the taxonomic diversity and the biomass. Cyanophita prevailed in number.

  16. Phytoplankton Diversity Effects on Community Biomass and Stability along Nutrient Gradients in a Eutrophic Lake

    Directory of Open Access Journals (Sweden)

    Wang Tian

    2017-01-01

    Full Text Available The relationship between biodiversity and ecosystem functioning is a central issue in ecology, but how this relationship is affected by nutrient stress is still unknown. In this study, we analyzed the phytoplankton diversity effects on community biomass and stability along nutrient gradients in an artificial eutrophic lake. Four nutrient gradients, varying from slightly eutrophic to highly eutrophic states, were designed by adjusting the amount of polluted water that flowed into the lake. Mean phytoplankton biomass, species richness, and Shannon diversity index all showed significant differences among the four nutrient gradients. Phytoplankton community biomass was correlated with diversity (both species richness and Shannon diversity index, varying from positive to negative along the nutrient gradients. The influence of phytoplankton species richness on resource use efficiency (RUE also changed from positive to negative along the nutrient gradients. However, the influence of phytoplankton Shannon diversity on RUE was not significant. Both phytoplankton species richness and Shannon diversity had a negative influence on community turnover (measured as community dissimilarity, i.e., a positive diversity–stability relationship. Furthermore, phytoplankton spatial stability decreased along the nutrient gradients in the lake. With increasing nutrient concentrations, the variability (standard deviation of phytoplankton community biomass increased more rapidly than the average total biomass. Results in this study will be helpful in understanding the phytoplankton diversity effects on ecosystem functioning and how these effects are influenced by nutrient conditions in aquatic ecosystems.

  17. Phytoplankton Identification Manual

    Digital Repository Service at National Institute of Oceanography (India)

    Verlecar, X.N.; Desai, S.R.

    . Bacillariophyceae (Diatoms) 6.1 Structure of the diatom cell 6.2 Gross vegetative structure 6.3 Cell division 6.4 Classification of Diatoms 7. Phyrrophyceae (Dinoflagellates) 8. Micrometry 9. Measurement of Biomass 9.1 Chlorophyll measurements 9.2 Cell... counts 9.3 Cell count by drop count method 10. Measurement of productivity 11. Bibliography 1 1. Introduction Phytoplankton (?phyto? = plant; ?planktos? = made to wander) are single celled marine algae, some of which are capable of movement through...

  18. Photosynthetic carbon metabolism in freshwater phytoplankton

    International Nuclear Information System (INIS)

    Groeger, A.W.

    1986-01-01

    Photosynthetic carbon metabolism of natural assemblages of freshwater phytoplankton was measured by following the flow of inorganic 14 C into the photosynthetic end products polysaccharide protein, lipid, and soluble metabolites. Data were collected from a wide range of physical, chemical, and trophic conditions in six southern United States reservoirs, with the primary environmental variables of interest being light intensity and nutrient supply. Polysaccharide and protein were consistently the primary products of photosynthetic carbon metabolism, comprising an average of 70% of the total carbon fixation over a wide range of light intensities. Polysaccharide was quantitatively more important at higher light intensities, and protein at lower light intensities, as light intensity varied both with depth within the water column and over diurnal cycles. Polysaccharide synthesis was more variable over the diurnal period than was protein synthesis. Phytoplankton in the downlake epilimnion of Normandy Lake, a central Tennessee reservoir, responded to summer nitrogen (N) deficiency by increasing relative rates of lipid synthesis from 10-15% to 20-25% of the total photosynthetic carbon fixation. Phytoplankton in more nitrogen-sufficient areas of the reservoir maintained lower rates of lipid synthesis throughout the summer. These results document the occurrence in nature of a relationship between N-deficiency and increased lipid synthesis previously observed only in laboratory algal culture studies

  19. Phytoplankton Monitoring Network - Phytoplankton Analysis with Associated Collection Information

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A qualitative collection of data that includes salinity, temperature, phytoplankton counts and abundance ratios obtained from surface tows in the estuarine and...

  20. UV-radiation and skin cancer dose effect curves

    International Nuclear Information System (INIS)

    Henriksen, T.; Dahlback, A.; Larsen, S.H.

    1988-08-01

    Norwegian skin cancer data were used in an attempt to arrive at the dose effect relationship for UV-carcinogenesis. The Norwegian population is relatively homogenous with regard to skin type and live in a country where the annual effective UV-dose varies by approximately 40 percent. Four different regions of the country, each with a broadness of 1 o in latitude (approximately 111 km), were selected . The annual effective UV-doses for these regions were calculated assuming normal ozone conditions throughout the year. The incidence of malignant melanoma and non-melanoma skin cancer (mainly basal cell carcinoma) in these regions were considered and compared to the annual UV-doses. For both these types of cancer a quadratic dose effect curve seems to be valid. Depletions of the ozone layer results in larger UV-doses which in turn may yield more skin cancer. The dose effect curves suggest that the incidence rate will increase by an ''amplification factor'' of approximately 2

  1. Dose-effect relationship and risk factors for vaginal stenosis after definitive radio(chemo)therapy with image-guided brachytherapy for locally advanced cervical cancer in the EMBRACE study

    DEFF Research Database (Denmark)

    Kirchheiner, Kathrin; Nout, Remi A; Lindegaard, Jacob C

    2016-01-01

    Background/purpose To identify risk factors for vaginal stenosis and to establish a dose–effect relationship for image-guided brachytherapy in locally advanced cervical cancer. Materials/Methods Patients from the ongoing EMBRACE study with prospectively assessed morbidity (CTCAEv3.0) at baseline ...

  2. Impact of wastewater on phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswar, M.J.R.

    A number of studies on phytoplankton were conducted by National Institute of Oceanography, Goa, India at Thane Creek, Maharashtra, India, Ulhas River estuary, Versova Creek and Mahim Creek under Coastal Ocean Monitoring and Prediction System (COMAPS...

  3. Mesoscale features and phytoplankton biomass at the GoodHope ...

    African Journals Online (AJOL)

    The observations provide evidence to show that the fronts act to both enhance phytoplankton biomass as well as to delimit regions of similar chlorophyll concentrations, although the front–chlorophyll relationships become obscure towards the end of the growing season due to bloom advection and 'patchy' Chl a behaviour.

  4. Spatial variation of phytoplankton community structure in Daya Bay, China.

    Science.gov (United States)

    Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Zhang, Jian-Dong; Fei, Jiao

    2015-10-01

    Daya Bay is one of the largest and most important gulfs in the southern coast of China, in the northern part of the South China Sea. The phylogenetic diversity and spatial distribution of phytoplankton from the Daya Bay surface water and the relationship with the in situ water environment were investigated by the clone library of the large subunit of ribulose-1, 5-bisphosphate carboxylase (rbcL) gene. The dominant species of phytoplankton were diatoms and eustigmatophytes, which accounted for 81.9 % of all the clones of the rbcL genes. Prymnesiophytes were widely spread and wide varieties lived in Daya Bay, whereas the quantity was limited. The community structure of phytoplankton was shaped by pH and salinity and the concentration of silicate, phosphorus and nitrite. The phytoplankton biomass was significantly positively affected by phosphorus and nitrite but negatively by salinity and pH. Therefore, the phytoplankton distribution and biomass from Daya Bay were doubly affected by anthropic activities and natural factors.

  5. Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea.

    Science.gov (United States)

    Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C; Daniels, Chris J; Inall, Mark; Davidson, Keith

    2016-01-01

    The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to

  6. Environmental flow assessments in estuaries related to preference of phytoplankton

    Science.gov (United States)

    Yang, Z. F.; Sun, T.; Zhao, R.

    2014-01-01

    We developed an approach to assess environmental flows in estuaries related to preference of phytoplankton considering the complex relationship between hydrological modification and biomass in ecosystems. As a first step, a relationship was established between biomass requirements for organisms of primary and higher nutritional levels based on the principle of nutritional energy flow of ecosystem. Then, diagnostic pigments were employed to represent phytoplankton community biomass, which indicated competition between two groups of phytoplankton in the biochemistry process. Considering empirical relationships between diagnostic pigments and critical environmental factors, responses of biomass to river discharges were established based on a convection-diffusion model by simulating distributions of critical environmental factors under action of river discharges and tide currents. Consequently, environmental flows could be recommended for different requirements of fish biomass. In the case study in the Yellow River estuary, May and October were identified as critical months for fish reproduction and growth during dry years. Artificial hydrological regulation strategies should carefully consider the temporal variations of natural flow regime, especially for a high-amplitude flood pulse, which may cause negative effects on phytoplankton groups and higher organism biomass.

  7. Physicochemical Flux and Phytoplankton diversity in Shagari ...

    African Journals Online (AJOL)

    USER

    2007-03-20

    Mar 20, 2007 ... distribution of phytoplankton species were also determined. Phytoplankton classes ... could have a significant impact on water quality. (Carpenter and Kitchell ..... Environmental Impact assessment Report on proposed Shagari ...

  8. Mapping of trophic states based on nutrients concentration and phytoplankton abundance in Jatibarang Reservoir

    Science.gov (United States)

    Rudiyanti, Siti; Anggoro, Sutrisno; Rahman, Arif

    2018-02-01

    Jatibarang Reservoir is one of the Indonesian Reservoirs, which used for human activities such as tourism and agriculture. These activities will provide input of organic matter and nutrients into the water. These materials will impact water quality and eutrophication process. Eutrophication is the water enrichment by nutrients, especially nitrogen and phosphorus which can promote the growth of phytoplankton. Some indicators of eutrophication are increasing nutrients, trophic states, and change of phytoplankton composition. The relationship between water quality and phytoplankton community can be used as an indicator of trophic states in Jatibarang Reservoir. The aim of this study was to analyze the effect of nutrients concentration and phytoplankton abundance to the trophic states and mapping trophic states based on nutrients concentration and phytoplankton in Jatibarang Reservoir. This study was conducted in June and July 2017 at 9 stations around Jatibarang Reservoir. The results showed that average concentration of nitrate, phosphate, and chlorophyll-a in Jatibarang Reservoir was 0.69 mg/L, 0.27 mg/L, and 1.66 mg/m3, respectively. The phytoplankton abundance ranged 16-62,200 cells/L, consists of 21 genera of four classes, i.e. Chlorophyceae, Cyanophyceae, Bacillariophyceae, and Dinophyceae. Cyanophyceae was a dominant phytoplankton group based on the composition of abundance (>80%). High nutrient concentrations and phytoplankton dominated by Anabaena (Cyanophyceae) which indicated that the waters in Jatibarang Reservoir were eutrophic.

  9. The time factor in dose-effect relationships

    International Nuclear Information System (INIS)

    Jones, H.B.; Grendon, A.; White, M.R.; California Univ., Berkeley

    1976-01-01

    The assumption that carcinogenic risk is proportional to dose fails to consider that probable time of actual cancer incidence. The time lag between exposure and carcinogenic effect for radiation and chemical agents varies as Dosesup(-1/n), with napproximately3. A model is offered explaining that concentration of initially altered cells depends on dose, whereas their chance for development into tumours on their proximity, which varies as Dsup(-1/3). Because of biological variability, n has a range of values. The model implies that tumours resulting from a single exposure should be closely distributed in time, producing a pulse of cases and subsequently being essentially without effect. Testing of the Dsup(-1/3) rule was extended and its model, by further refinement of methods, applied to radiogenic leukaemia risk and to the effect of urethan in inducing lung tumours in mice with and without radiation exposure as a possible cocarcinogen. Radiation did not affect the tumour yield from urethan in mice. Radiogenic leukaemia and lung tumours induced by urethan both occur in proportion to exposure, but the time of their occurrence is limited to a short interval in relation to life span. Similarly, in murine or in human radiogenic leukaemia, leukaemia risk occurs in proportion to exposure, but the time of occurrences is limited to a short interval in relation to life span. In both sets of observations, as well as in other test systems of carcinogenesis, the peak of occurrence or the mean latent period is roughly inversely related to Dsup(-1/3). Applied to lung tumours and leukaemia, the spread of cases about the peak incidence was found to be typically less than a fifth of the life span. Exposure risks do not continue to act over life span. Neoplastic disease risk from carcinogens levels too low to be tested experimentally, theoretically usually lies beyond the life span. The social and economic consequences of a theoretically calculated number of deaths due to those carcinogens depend on when they occur

  10. Dose effect relationships in cervical and thoracic radiation myelopathies

    International Nuclear Information System (INIS)

    Holdorff, B.

    1980-01-01

    The course and prognosis of radiation myelopathies are determined by 3 factors: the segmental (vertical) location of the lesion, the extent of the transverse syndrome (complete or incomplete) and the radiation dose. The median spinal dose in cervical radiation myelopathies with fatal outcome was higher than in survivals with an incomplete transverse syndrome. In thoracic radiation myelopathies a dose difference between complete and incomplete transverse syndromes could be found as well. Incomplete transverse syndromes as submaximum radiation injuries are more suitable for the determination of the spinal tolerance dose than complete transverse syndromes. The lowest threshold could be stated for cases following high-volume irradiation of the lymphatic system. (Auth.)

  11. Seasonal development of phytoplankton populations in offshore Lake Michigan in 1975

    International Nuclear Information System (INIS)

    Parker, J.I.; Conway, H.L.; Yaguchi, E.M.

    1975-01-01

    Relationships between phytoplankton bloom sequences and environmental factors that may account for seasonal variations have not been thoroughly evaluated in Lake Michigan. We investigated the seasonal periodicity of phytoplankton in the offshore water from April to December, 1975. The seasonal distributions of phytoplankton biomass, chlorophyll a, and primary productivity per unit of lake surface area were measured at station 5. These measurements demonstrated a bimodal seasonal distribution, with maxima occurring in June and October. Previous investigators have shown that the seasonal periodicity was unimodal, with a summer maximum. Our observations demonstrated year to year variations in this abundance pattern

  12. Dose-effect studies with inhaled plutonium oxide in beagles

    International Nuclear Information System (INIS)

    Park, J.F.; Buschbom, R.L.; Case, A.C.

    1976-01-01

    Beagle dogs given single exposure to 239 PuO 2 or 238 PuO 2 aerosols are being observed for life-span dose-effect relationships. The 239 Pu body burden of the nine dogs dying due to pulmonary fibrosis-induced insufficiency during the first 3 years after exposure was 1 to 12 μCi. One of these dogs had a pulmonary tumor. Three additional dogs with body burdens of 0.7 to 1.8 μCi died due to pulmonary neoplasia 4-1/2 years after exposure. None of the dogs exposed to 238 Pu have died during the first two postexposure years. After inhalation of 239 PuO 2 or 238 PuO 2 lymphocytopenia was the earliest observed effect, occuring 0.5 to 2 years after deposition of greater than or equal to 80 nCi plutonium in the lungs

  13. Dose-effect studies with inhaled plutonium oxide in beagles

    International Nuclear Information System (INIS)

    Park, J.F.; Buschbom, R.L.; Case, A.C.

    1977-01-01

    Beagle dogs given a single exposure to 239 PuO 2 or 238 PuO 2 aerosols are being observed for life-span dose-effect relationships. The 239 Pu body burden of the nine dogs that died of pulmonary fibrosis-induced respiratory insufficiency during the first 3 yr after exposure was 1 to 12 μCi. One of these dogs had a pulmonary tumor. Five additional dogs with body burdens of 0.7 to 1.8 μCi died due to pulmonary neoplasia 3 to 5 yr after exposure. None of the dogs exposed to 238 Pu have died during the first 3 postexposure yr. Lymphocytopenia was the earliest observed effect after inhalation of 239 PuO 2 or 238 PuO 2 , occurring 0.5 to 2 yr after deposition of greater than or equal to 80 nCi plutonium in the lungs

  14. Climatologic relationship of the superficial temperature of the Colombian Pacific on the marine phytoplankton, during The Boy 1991-92; Relacion climatologica de la temperatura superficial del pacifico colombiano sobre el fitoplancton marino, durante El nino 1991-92

    Energy Technology Data Exchange (ETDEWEB)

    Castillo G, Francisco A; Osorio, David

    1994-03-15

    The analysis was carried out in the geographical area for the ERFEN understood among the 2 degrade at the 6 degrade of latitude N and 82 degrade of longitude W, specifically in the areas to the north of the Colombian Pacific (Cabo Corrientes) Profile Buenaventura-Malpelo and Profile Tumaco, being studied the superficial phytoplankton in the two characteristic times of the Pacific and taking like reference the existent historical data. The Incidence of the environmental parameter is presented, as it is the temperature on the distribution of a marine ecosystem as it is the superficial marine phytoplankton. It was observed that the identified species as the biological Indicators of the southeastern oscillation, coincided equally with the beginning of the indicative thermal anomalies of the evolution of a warm event with the obtained data it was visualized that the composition of the opposing phytoplankton during the period of study, reflective a mixture of elements with very diverse ecological width, reflecting waters of different provenience: Coastal and oceanic. Bigger information is contributed with the end to supplement the knowledge on the indicative organisms that detect in early form the environmental changes taken place by the phenomenon El Nino, and of this form, to complete the physical-chemical and fishing studies allowing to give approaches in the political orientation in the activities that could be affected, such as fishing strategy, measures on aquiculture, marketing decision, handling of hydrobiologic resources, etc.

  15. Winds and the distribution of nearshore phytoplankton in a stratified lake.

    Science.gov (United States)

    Cyr, Hélène

    2017-10-01

    The distribution of phytoplankton in lakes is notoriously patchy and dynamic, but wind-driven currents and algal buoyancy/motility are thought to determine where algae accumulate. In this study, nearshore phytoplankton were sampled from different parts of a lake basin twice a day for 4-5 consecutive days, in the spring and in late summer, to test whether short-term changes in phytoplankton biomass and community composition can be predicted from wind-driven currents. On windy days, phytoplankton biomass was higher at downwind than at upwind nearshore sites, and the magnitude of this difference increased linearly with increasing wind speed. However, contrary to the generally assumed downwind phytoplankton aggregations, these differences were mostly due to upwelling activity and the dilution of phytoplankton at upwind nearshore sites. The distribution of individual taxa was also related to wind speed, but only during late stratification (except for cryptophytes), and these relationships were consistent with the buoyancy and motility of each group. On windy days, large diatoms and cyanobacteria concentrated upwind, neutrally buoyant taxa (green algae, small diatoms) were homogeneously distributed, and motile taxa (cryptophytes, chrysophytes, dinoflagellates) concentrated downwind. Predictable differences in the biomass and composition of phytoplankton communities could affect the efficiency of trophic transfers in nearshore areas. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate.

    Directory of Open Access Journals (Sweden)

    Cong Wang

    Full Text Available Glyphosate is a globally popular herbicide to kill weeds and its wide applications may lead to accumulation in coastal oceans as a source of phosphorus (P nutrient or growth inhibitor of phytoplankton. We studied the physiological effects of glyphosate on fourteen species representing five major coastal phytoplankton phyla (haptophyta, bacillariophyta, dinoflagellata, raphidophyta, and chlorophyta. Based on growth responses to different concentrations of glyphosate under contrasting dissolved inorganic phosphorus (DIP conditions, we found that phytoplankton species could be classified into five groups. Group I (Emiliania huxleyi, Skeletonema costatum, Phaeodactylum tricornutum could utilize glyphosate as sole P-source to support growth in axenic culture, but in the presence of DIP, they were inhibited by both 36-μM and 360-μM glyphosate. Group II (Karenia mikimotoi, Prorocentrum minimum, Dunaliella tertiolecta, Symbiodinium sp., Heterosigma akashiwo and Alexandrium catenella could not utilize glyphosate as sole P-source to support growth, and in the presence of DIP growth was not affected by 36-μM but inhibited by 360-μM glyphosate. Glyphosate consistently enhanced growth of Group III (Isochrysis galbana and inhibited Group IV (Thalassiosira weissflogii, Thalassiosira pseudonana and Chattonella marina regardless of DIP condition. Group V (Amphidinium carterae exhibited no measurable response to glyphosate regardless of DIP condition. This grouping is not congruent with the phylogenetic relationships of the phytoplankton species suggesting functional differentiation driven by environmental pressure. We conclude that glyphosate could be used as P-source by some species while is toxic to some other species and yet has no effects on others. The observed differential effects suggest that the continued use of glyphosate and increasing concentration of this herbicide in the coastal waters will likely exert significant impact on coastal marine

  17. Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate

    Science.gov (United States)

    Wang, Cong; Lin, Xin; Li, Ling; Lin, Senjie

    2016-01-01

    Glyphosate is a globally popular herbicide to kill weeds and its wide applications may lead to accumulation in coastal oceans as a source of phosphorus (P) nutrient or growth inhibitor of phytoplankton. We studied the physiological effects of glyphosate on fourteen species representing five major coastal phytoplankton phyla (haptophyta, bacillariophyta, dinoflagellata, raphidophyta, and chlorophyta). Based on growth responses to different concentrations of glyphosate under contrasting dissolved inorganic phosphorus (DIP) conditions, we found that phytoplankton species could be classified into five groups. Group I (Emiliania huxleyi, Skeletonema costatum, Phaeodactylum tricornutum) could utilize glyphosate as sole P-source to support growth in axenic culture, but in the presence of DIP, they were inhibited by both 36-μM and 360-μM glyphosate. Group II (Karenia mikimotoi, Prorocentrum minimum, Dunaliella tertiolecta, Symbiodinium sp., Heterosigma akashiwo and Alexandrium catenella) could not utilize glyphosate as sole P-source to support growth, and in the presence of DIP growth was not affected by 36-μM but inhibited by 360-μM glyphosate. Glyphosate consistently enhanced growth of Group III (Isochrysis galbana) and inhibited Group IV (Thalassiosira weissflogii, Thalassiosira pseudonana and Chattonella marina) regardless of DIP condition. Group V (Amphidinium carterae) exhibited no measurable response to glyphosate regardless of DIP condition. This grouping is not congruent with the phylogenetic relationships of the phytoplankton species suggesting functional differentiation driven by environmental pressure. We conclude that glyphosate could be used as P-source by some species while is toxic to some other species and yet has no effects on others. The observed differential effects suggest that the continued use of glyphosate and increasing concentration of this herbicide in the coastal waters will likely exert significant impact on coastal marine phytoplankton

  18. Phytoplankton species composition of four ecological provinces in Yellow Sea, China

    Science.gov (United States)

    Li, Xiaoqian; Feng, Yuanyuan; Leng, Xiaoyun; Liu, Haijiao; Sun, Jun

    2017-12-01

    The ecological province based on phytoplankton species composition is important to understanding the interplay between environmental parameters and phytoplankton species composition. The aim of this study was to establish phytoplankton species composition ecological pattern thus elucidate the relationship between environmental factors and the phytoplankton species composition in the ecological provinces. Phytoplankton samples were collected from 31 stations in Yellow Sea (121.00°-125.00°E, 32.00°-39.22°N) in November 2014. The samples were enumerated and identified with the Utermöhl method under an optical inverted microscope-AE2000 with magnifications of 200 × or 400 ×. In the present study, a total of 141 taxa belonging to 60 genera of 4 phyla of phytoplankton were identified, among them 101 species of 45 genera were Bacillariophyta, 36 species of 11 genera were Dinophyta, 3 species of 3 genera were Chrysophyta and 1 species of 1 genera was Chlorophyta. The study area was divided into 4 ecological provinces according to an unsupervised cluster algorithm applied to the phytoplankton biomass. A T-S (Temperature-Salinity) scatter diagram depicted with data of water temperature and salinity defined by environmental provinces matched well with the ecological provinces. The results of Canonical Correspondence Analysis (CCA) indicated that the phytoplankton species composition was mainly correlated with temperature, salinity and silicate concentration in the studied area. A method of establishing ecological provinces is useful to further understanding the environmental effects on the marine phytoplankton species composition and the consequent marine biogeochemistry.

  19. Phytoplankton community and limnochemistry of Piburger See (Tyrol, Austria 28 years after lake restoration

    Directory of Open Access Journals (Sweden)

    Hansjörg THIES

    2002-02-01

    Full Text Available Phytoplankton community and limnochemistry of Piburger See, a small soft-water, meromictic lake situated at 913 m a.s.l. in a crystalline area of the Central Eastern Alps of Tyrol (Austria, were investigated 28 years after the beginning of lake restoration. Although long-term data of the lake show a declining trend in total phosphorus concentrations and phytoplankton biovolume, the response of Piburger See to the restoration measures carried out in 1970 was delayed by about 20 years. At present the lake is approaching its former oligotrophic level. The most evident difference between the past and present phytoplankton species composition of Piburger See is the actual absence of the Cyanophycean Oscillatoria limosa C. A. Agardh, which markedly increased during the first two decades after the lake restoration (1970-1987. The phytoplankton biovolume recorded in 1998 was lower than in the 1970s and 1980s, while seasonal patterns were similar to those recorded before and later on in the lake restoration. The lowest annual phytoplankton biovolume in 1998 occurred in early winter, while the absolute maximum was observed in metalimnetic water layers in late spring. In 1998 the intra-annual patterns of phytoplankton biovolume and chlorophyll-a compare well. Phytoplankton succession started in early 1998 under ice with coccal green algae followed by flagellated Chrysophyceae during spring. The mid-summer phytoplankton community was dominated by centric Bacillariophyceae, which were later replaced by coccal Cyanophyceae. During autumn, Dinophyceae and Chrysophyceae prevailed. Epilimnetic dominance of centric diatoms during mid summer appears to be a new feature, which in 1998 was related to a strong depletion of dissolved silica and nitrate. Long-term water chemistry and phytoplankton data were checked against local weather data in order to explain the delay in the re-oligotrophication process of Piburger See. However, no clear relationship could be

  20. State of Climate 2011 - Global Ocean Phytoplankton

    Science.gov (United States)

    Siegel, D. A.; Antoine, D.; Behrenfeld, M. J.; d'Andon, O. H. Fanton; Fields, E.; Franz, B. A.; Goryl, P.; Maritorena, S.; McClain, C. R.; Wang, M.; hide

    2012-01-01

    Phytoplankton photosynthesis in the sun lit upper layer of the global ocean is the overwhelmingly dominant source of organic matter that fuels marine ecosystems. Phytoplankton contribute roughly half of the global (land and ocean) net primary production (NPP; gross photosynthesis minus plant respiration) and phytoplankton carbon fixation is the primary conduit through which atmospheric CO2 concentrations interact with the ocean s carbon cycle. Phytoplankton productivity depends on the availability of sunlight, macronutrients (e.g., nitrogen, phosphorous), and micronutrients (e.g., iron), and thus is sensitive to climate-driven changes in the delivery of these resources to the euphotic zone

  1. Single event effects and total ionizing dose effects of typical VDMOSFET devices

    International Nuclear Information System (INIS)

    Lou Jianshe; Cai Nan; Liu Jiaxin; Wu Qinzhi; Wang Jia

    2012-01-01

    In this work, single event effects and total ionizing dose effects of typical VDMOSFET irradiated by 60 Co γ-rays and 252 Cf source were studied. The single event burnout and single event gate rupture (SEB/SEGR) effects were investigated, and the relationship between drain-source breakdown voltage and ionizing dose was obtained. The results showed that the VDMOSFET devices were sensitive to SEB and SEGR, and measures to improve their resistance to SEB and SEGR should be considered seriously for their space applications. The drain-source breakdown voltage was sensitive to total ionizing dose effects as the threshold voltage. In assessing the devices' resistance to the total ionizing dose effects, both the threshold voltage and the drain-source breakdown voltage should be taken into account. (authors)

  2. Impact of oil shale mine water discharges on phytoplankton community of Purtse catchment rivers

    International Nuclear Information System (INIS)

    Raetsep, A.; Rull, E.; Liblik, V.

    2002-01-01

    The multivariate relationship between phytoplankton abundance and different factors both natural and generated by oil shale mining in the Purtse catchment rivers (Purtse, Kohtla, and Ojamaa) in Augusts 1996-2000 was studied. Impact of oil shale mine water discharges, causing the input of sulfates and chlorides into the rivers, on phytoplankton abundance in river water was characterized by significant negative linear correlation. The amount of annual precipitation influenced positively the characteristics of phytoplankton abundance in river water. The complex of linear regression formulas was derived for characterising phytoplankton abundance in the lower course of the Purtse River using meteorological, hydrological and hydrogeological as well as geochemical data of water circulation. Closing the Sompa, Tammiku and Kohtla mines in 2000-2001 decreased essentially anthropogenic stress on ecological condition of the Purtse catchment rivers. (author)

  3. Biochemical and cellular mechanisms of low-dose effects

    International Nuclear Information System (INIS)

    Feinendegen, L.E.; Booz, J.; Muehlensiepen, H.

    1988-01-01

    The question of health effects from small radiation doses remains open. Individual cells, when being hit by single elemental doses - in low-dose irradiation - react acutely and temporarily by altering control of enzyme activity, as is demonstrated for the case of thymidine kinase. This response is not constant in that it provides a temporary protection of enzyme activity against a second irradiation, by a mechanism likely to be via improved detoxification of intracellular radicals. It must be considered that in the low-dose region radiation may also exert protection against other challenges involving radicals, causing a net beneficial effect by temporarily shielding the hit cell against radicals produced by metabolism. Since molecular alterations leading to late effects are considered a consequence of the initial cellular response, late effects from small radiation doses do not necessarily adhere to a linear dose-effect relationship. The reality of the linear relationship between the risk of late effects from high doses to small doses is an assumption, for setting dose limits, but it must not be taken for predicting health detriment from low doses. (author)

  4. Photophysiological and light absorption properties of phytoplankton communities in the river-dominated margin of the northern Gulf of Mexico

    Science.gov (United States)

    Chakraborty, Sumit; Lohrenz, Steven E.; Gundersen, Kjell

    2017-06-01

    Spatial and temporal variability in photophysiological properties of phytoplankton were examined in relationship to phytoplankton community composition in the river-dominated continental margin of the northern Gulf of Mexico (NGOM). Observations made during five research cruises in the NGOM included phytoplankton photosynthetic and optical properties and associated environmental conditions and phytoplankton community structure. Distinct patterns of spatial and temporal variability in photophysiological parameters were found for waters dominated by different phytoplankton groups. Photophysiological properties for locations associated with dominance by a particular group of phytoplankton showed evidence of photoacclimation as reflected by differences in light absorption and pigment characteristics in relationship to different light environments. The maximum rate of photosynthesis normalized to chlorophyll (PmaxB) was significantly higher for communities dominated (>60% biomass) by cyanobacteria + prochlorophyte (cyano + prochl). The initial slope of the photosynthesis-irradiance (P-E) curve normalized to chlorophyll (αB) was not clearly related to phytoplankton community structure and no significant differences were found in PmaxB and αB between different geographic regions. In contrast, maximum quantum yield of carbon fixation in photosynthesis (Φcmax) differed significantly between regions and was higher for diatom-dominated communities. Multiple linear regression models, specific for the different phytoplankton communities, using a combination of environmental and bio-optical proxies as predictor variables showed considerable promise for estimation of the photophysiological parameters on a regional scale. Such an approach may be utilized to develop size class-specific or phytoplankton group-specific primary productivity models for the NGOM.Plain Language SummaryThis study examined the relationships between phytoplankton community composition and associated

  5. Occurrence and biosynthesis of carotenoids in phytoplankton.

    Science.gov (United States)

    Huang, Jim Junhui; Lin, Shaoling; Xu, Wenwen; Cheung, Peter Chi Keung

    2017-09-01

    Naturally occurring carotenoids are important sources of antioxidants, anti-cancer compounds and anti-inflammatory agents and there is thus considerable market demand for their pharmaceutical applications. Carotenoids are widely distributed in marine and freshwater organisms including microalgae, phytoplankton, crustaceans and fish, as well as in terrestrial plants and birds. Recently, phytoplankton-derived carotenoids have received much attention due to their abundance, rapid rate of biosynthesis and unique composition. The carotenoids that accumulate in particular phytoplankton phyla are synthesized by specific enzymes and play unique physiological roles. This review focuses on studies related to the occurrence of carotenoids in different phytoplankton phyla and the molecular aspects of their biosynthesis. Recent biotechnological advances in the isolation and characterization of some representative carotenoid synthases in phytoplankton are also discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Effect of flow rate on environmental variables and phytoplankton dynamics: results from field enclosures

    Science.gov (United States)

    Zhang, Haiping; Chen, Ruihong; Li, Feipeng; Chen, Ling

    2015-03-01

    To investigate the effects of flow rate on phytoplankton dynamics and related environment variables, a set of enclosure experiments with different flow rates were conducted in an artificial lake. We monitored nutrients, temperature, dissolved oxygen, pH, conductivity, turbidity, chlorophyll- a and phytoplankton levels. The lower biomass in all flowing enclosures showed that flow rate significantly inhibited the growth of phytoplankton. A critical flow rate occurred near 0.06 m/s, which was the lowest relative inhibitory rate. Changes in flow conditions affected algal competition for light, resulting in a dramatic shift in phytoplankton composition, from blue-green algae in still waters to green algae in flowing conditions. These findings indicate that critical flow rate can be useful in developing methods to reduce algal bloom occurrence. However, flow rate significantly enhanced the inter-relationships among environmental variables, in particular by inducing higher water turbidity and vegetative reproduction of periphyton ( Spirogyra). These changes were accompanied by a decrease in underwater light intensity, which consequently inhibited the photosynthetic intensity of phytoplankton. These results warn that a universal critical flow rate might not exist, because the effect of flow rate on phytoplankton is interlinked with many other environmental variables.

  7. Variation of phytoplankton functional groups modulated by hydraulic controls in Hongze Lake, China.

    Science.gov (United States)

    Tian, Chang; Pei, Haiyan; Hu, Wenrong; Hao, Daping; Doblin, Martina A; Ren, Ying; Wei, Jielin; Feng, Yawei

    2015-11-01

    Hongze Lake is a large, shallow, polymictic, eutrophic lake in the eastern China. Phytoplankton functional groups in this lake were investigated from March 2011 to February 2013, and a comparison was made between the eastern, western, and northern regions. The lake shows strong fluctuations in water level caused by monsoon rains and regular hydraulic controls. By application of the phytoplankton functional group approach, this study aims to investigate the spatial and temporal dynamics and analyze their influencing factors. Altogether, 18 functional groups of phytoplankton were identified, encompassing 187 species. In order to seek the best variable describing the phytoplankton functional group distribution, 14 of the groups were analyzed in detail using redundancy analysis. Due to the turbid condition of the lake, the dominant functional groups were those tolerant of low light. The predominant functional groups in the annual succession were D (Cyclotella spp. and Synedra acus), T (Planctonema lauterbornii), P (Fragilaria crotonensis), X1 (Chlorella vulgaris and Chlorella pyrenoidosa), C (Cyclotella meneghiniana and Cyclotella ocellata), and Y (Cryptomonas erosa). An opposite relationship between water level and the biomass of predominant groups was observed in the present study. Water level fluctuations, caused by monsoonal climate and artificial drawdown, were significant factors influencing phytoplankton succession in Hongze Lake, since they alter the hydrological conditions and influence light and nutrient availability. The clearly demonstrated factors, which significantly influence phytoplankton dynamics in Hongze Lake, will help government manage the large shallow lakes with frequent water level fluctuations.

  8. Dose-effect studies with inhaled plutonium nitrate in dogs

    International Nuclear Information System (INIS)

    Dagle, G.E.; Cannon, W.C.; Case, A.C.; Madison, R.M.; McShane, J.F.; Stevens, D.L.; Rowe, S.E.; Ragan, H.A.; Schirmer, R.E.

    1980-01-01

    Beagle dogs given a single inhalation exposure to 239 Pu(NO 3 ) 4 , and observed for life-span dose-effect relationship, died from radiation pneumonitis (four of five at the highest dosage level, in 14 to 25 mo postexposure; 1 of 20 at the medium-high dosage level, at 34 mo postexposure). There were also indications in these dogs of radiation osteosis, characterized by peritrabecular fibrosis. One dog, at 39 mo postexposure, has radiographic evidence of an osteosarcoma. Leukopenia, lymphopenia, neutropenia and decreased numbers of circulating monocytes and eosinophils occurred at the two highest dosage levels, as previously reported (Annual Report, 1978). Twelve dogs given a single inhalation exposure to 238 Pu(NO 3 ) 4 showed a more rapid translocation of 238 Pu(NO 3 ) 4 to bone and liver than was observed for 239 Pu(NO 3 ) 4 , but at 1 yr postexposure the percentage of the final body burden in bone and liver were similar for the two isotopes

  9. Dose-effect studies with inhaled plutonium oxide in beagles

    International Nuclear Information System (INIS)

    Park, J.F.; Case, A.C.; Catt, D.L.

    1978-01-01

    Beagle dogs given a single exposure to 239 PuO 2 and 238 PuO 2 aerosols are being observed for life-span dose-effect relationships. The 239 Pu body burden of the nine dogs that died of pulmonary fibrosis-induced respiratory insufficiency during the first 3 yr after exposure was 1 to 12 μCi. One of these dogs had a pulmonary tumor; nine additional dogs with body burdens of 0.6 to 1.8 μCi died due to pulmonary neoplasia 3 to 6 yr after exposure. Two of the dogs exposed to 238 Pu have died during the first 4 yr postexposure, due to bone and lung tumors, with body burdens at death of 10 μCi. Lymphocytopenia was the earliest observed effect after inhalation of 239 PuO 2 or 238 PuO 2 , occurring 0.5 to 2 yr after deposition of equal to or greater than 80 nCi plutonium in the lungs

  10. Use of nonlinear dose-effect models to predict consequences

    International Nuclear Information System (INIS)

    Seiler, F.A.; Alvarez, J.L.

    1996-01-01

    The linear dose-effect relationship was introduced as a model for the induction of cancer from exposure to nuclear radiation. Subsequently, it has been used by analogy to assess the risk of chemical carcinogens also. Recently, however, the model for radiation carcinogenesis has come increasingly under attack because its calculations contradict the epidemiological data, such as cancer in atomic bomb survivors. Even so, its proponents vigorously defend it, often using arguments that are not so much scientific as a mix of scientific, societal, and often political arguments. At least in part, the resilience of the linear model is due to two convenient properties that are exclusive to linearity: First, the risk of an event is determined solely by the event dose; second, the total risk of a population group depends only on the total population dose. In reality, the linear model has been conclusively falsified; i.e., it has been shown to make wrong predictions, and once this fact is generally realized, the scientific method calls for a new paradigm model. As all alternative models are by necessity nonlinear, all the convenient properties of the linear model are invalid, and calculational procedures have to be used that are appropriate for nonlinear models

  11. Dose-effect studies with inhaled plutonium oxide in beagles

    International Nuclear Information System (INIS)

    Park, J.F.; Case, A.C.; Catt, D.L.

    1980-01-01

    Beagle dogs given a single exposure to 239 PuO 2 and 238 PuO 2 aerosols are being observed for life-span dose-effect relationships. The 239 Pu body burden of the nine dogs that died of pulmonary-fibrosis-induced respiratory insufficiency during the first 3 yr after exposure was 1 to 12 μCi; one of these dogs had a pulmonary tumor. Seventeen additional dogs, with body burdens of 0.2 to 1.8 μCi, died due to pulmonary neoplasia 3 to 8 yr after exposure. Ten of the dogs exposed to 238 Pu have died during the first 5 1/2 yr postexposure due to bone and/or lung tumors; the body burden at death ranged from 1.5 to 10 μCi. Lymphopenia was the earliest observed effect after inhalation of 239 PuO 2 or 238 PuO 2 , occurring 0.5 to 2 yr after deposition of >80 nCi plutonium in the lungs

  12. Dose-effect studies with inhaled plutonium oxide in beagles

    International Nuclear Information System (INIS)

    Park, J.F.; Busch, R.H.; Case, A.C.

    1979-01-01

    Beagle dogs given a single exposure to 239 PuO 2 and 238 PuO 2 aerosols are being observed for life-span dose-effect relationships. The 239 Pu body burden of the nine dogs that dies of pulmonary fibrosis-induced respiratory insufficiency during the first 3 yr after exposure was 1 to 12 μCi; one of these dogs had a pulmonary tumor. Eleven additional dogs with body burdens of 0.6 to 1.8 μCi died due to pulmonary neoplasia 3 to 7 yr after exposure. Four of the dogs exposed to 238 Pu have died during the first 4 1/2 yr postexposure due to bone and/or lung tumors; the body burden at death ranged from 6 to 10 μCi. Lymphopenia was the earliest observed effect after inhalation of 239 PuO 2 or 238 PuO 2 , occurring 0.5 to 2 yr after deposition of greater than or equal to 80 nCi plutonium in the lungs

  13. Phytoplankton abundance in relation to the quality of the coastal water – Arabian Gulf, Saudi Arabia

    Directory of Open Access Journals (Sweden)

    Mostafa Abdel Mohsen El Gammal

    2017-12-01

    Full Text Available Phytoplankton abundance in relation to some physicochemical characters of the costal water of Arabian Gulf (Saudi Arabia was studied for one year. The sampling program included 15 locations in Dammam, Saihat, Al-Qatif, Al-Awamia and Safwa. Water samples were analyzed monthly for these parameters; temperature, pH, salinity, dissolved oxygen, nitrite, nitrate, ammonia, carbon dioxide, total chloride, reactive orthophosphate and total phosphorus and alkalinity, also phytoplankton communities were identified and Chlorophyll a was estimated. The results showed that, the high phytoplankton density attaining the maximum (190.3 × 104/m3 during May and June, and the minimum (10.4 × 104/m3 during November and December. Forty Five species belonging to 5 phytoplankton groups were recorded. Bacillariophyceae was the first dominant group forming 48% of the total phytoplankton communities (23 species. The dominant species of Bacillariophyceae were Pleurosigma strigosum, Pleurosigma elongatum, Lyrella clavata, Rhizosolenia shrubsolei, Cylindrotheca closterium, Nitzschia panduriform, Nitzschia longissimia, Amphora sp and Stephanopyxis. Dinophyceae was the second dominant group and formed 31% of the total phytoplankton communities (10 species; the dominant species were Ceratium fusus, Heterosigma sp, Ceratium furca, Prorocentrum triestium, Protoperidinium sp, Gyrodinium spirale, Noctiluca scintillans and Scrippsiella trochoidea. Cyanophyceae formed 13% (5 species where Nostoc sp, Oscillatoria and Merismopedia sp were the dominant species. Chlorophyceae had 8% (6 species; Scendesmus sp., Chlorella sp., Chlamydomonas sp., Dunaliella salina and Nannochloropsis sp were the dominant species. The Euglinophyceae was rare only one species (Euglina sp. The relationship was positive between the phytoplankton, chlorophyll a and carbon dioxide while negative amongst dissolved oxygen and total nitrogen. This research indicated that the relation between water quality

  14. Winter severity determines functional trait composition of phytoplankton in seasonally ice-covered lakes.

    Science.gov (United States)

    Özkundakci, Deniz; Gsell, Alena S; Hintze, Thomas; Täuscher, Helgard; Adrian, Rita

    2016-01-01

    How climate change will affect the community dynamics and functionality of lake ecosystems during winter is still little understood. This is also true for phytoplankton in seasonally ice-covered temperate lakes which are particularly vulnerable to the presence or absence of ice. We examined changes in pelagic phytoplankton winter community structure in a north temperate lake (Müggelsee, Germany), covering 18 winters between 1995 and 2013. We tested how phytoplankton taxa composition varied along a winter-severity gradient and to what extent winter severity shaped the functional trait composition of overwintering phytoplankton communities using multivariate statistical analyses and a functional trait-based approach. We hypothesized that overwintering phytoplankton communities are dominated by taxa with trait combinations corresponding to the prevailing winter water column conditions, using ice thickness measurements as a winter-severity indicator. Winter severity had little effect on univariate diversity indicators (taxon richness and evenness), but a strong relationship was found between the phytoplankton community structure and winter severity when taxon trait identity was taken into account. Species responses to winter severity were mediated by the key functional traits: motility, nutritional mode, and the ability to form resting stages. Accordingly, one or the other of two functional groups dominated the phytoplankton biomass during mild winters (i.e., thin or no ice cover; phototrophic taxa) or severe winters (i.e., thick ice cover; exclusively motile taxa). Based on predicted milder winters for temperate regions and a reduction in ice-cover durations, phytoplankton communities during winter can be expected to comprise taxa that have a relative advantage when the water column is well mixed (i.e., need not be motile) and light is less limiting (i.e., need not be mixotrophic). A potential implication of this result is that winter severity promotes different

  15. Tolerance of polar phytoplankton communities to metals

    International Nuclear Information System (INIS)

    Echeveste, P.; Tovar-Sánchez, A.; Agustí, S.

    2014-01-01

    Large amounts of pollutants reach polar regions, particularly the Arctic, impacting their communities. In this study we analyzed the toxic levels of Hg, Cd and Pb to natural phytoplankton communities of the Arctic and Southern Oceans, and compared their sensitivities with those observed on phytoplankton natural communities from temperate areas. Mercury was the most toxic metal for both Arctic and Antarctic communities, while both Cd and Pb were toxic only for the Antarctic phytoplankton. Total cell abundance of the populations forming the Arctic community increased under high Cd and Pb concentrations, probably due to a decrease of the grazing pressure or the increase of the most resistant species, although analysis of individual cells indicated that cell death was already induced at the highest levels. These results suggest that phytoplankton may have acquired adapting mechanisms to face high levels of Pb and Cd in the Arctic Ocean. Highlights: • First study analyzing the toxicity of Hg, Cd or Pb to natural polar phytoplankton. • Arctic Ocean communities highly resistant to Cd and Pb, but not to Hg. • Southern Ocean communities sensitive to Cd, Pb and Hg. • Both communities incorporated Pb at a similar level. • Arctic phytoplankton may have acquired adapting mechanisms against Cd and Pb. -- Polar phytoplankton communities are tolerant to Cd and Pb, specially the Arctic ones, suggesting the acquisition of adapting mechanisms to face metals' toxicity

  16. Spatial dynamics of a nutrient-phytoplankton system with toxic effect on phytoplankton.

    Science.gov (United States)

    Chakraborty, Subhendu; Tiwari, P K; Misra, A K; Chattopadhyay, J

    2015-06-01

    The production of toxins by some species of phytoplankton is known to have several economic, ecological, and human health impacts. However, the role of toxins on the spatial distribution of phytoplankton is not well understood. In the present study, the spatial dynamics of a nutrient-phytoplankton system with toxic effect on phytoplankton is investigated. We analyze the linear stability of the system and obtain the condition for Turing instability. In the presence of toxic effect, we find that the distribution of nutrient and phytoplankton becomes inhomogeneous in space and results in different patterns, like stripes, spots, and the mixture of them depending on the toxicity level. We also observe that the distribution of nutrient and phytoplankton shows spatiotemporal oscillation for certain toxicity level. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Phytoplankton Monitoring Network (PMN) - Sampling Sites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A qualitative collection of data that includes salinity, temperature, phytoplankton counts and abundance ratios obtained from surface tows in the estuarine and...

  18. Studies on phytoplankton with reference to dinoflagellates

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, R.K.

    Bibliography Publications Appendices Statement As required under the University ordinance 0.19.8 (vi), I state that the present thesis titled ³Studies on phytoplankton with reference to dinoflagellates´ is my original contribution...

  19. Phytoplankton Assessment in Danube Delta Biosphere Reserve

    Directory of Open Access Journals (Sweden)

    SPIRIDON Cosmin

    2016-12-01

    Full Text Available The term ”plankton” refers to those microscopic aquatic forms having little or no resistance to currents and living free-floating and suspended, in open or pelagic waters. Phytoplankton development has different consequences depending on biomass quality and quantity, the overgrowth result being eutrophication process. The eutrophication intensity can cause both a lower water transparency, by excessive algal growth, to fish death in the area. In this study, it was presented the ecological status and phytoplankton biomass dynamic, in the Danube branches from upstream to downstream. The measurements have been made in 2013, in March, June, September and November, using spectrofluorometer for algal biomass determination and a microscope for qualitative analyses of phytoplankton species. Shannon-Wiener index was calculated to compare phytoplankton species diversity. Also, the biodegradable organic matter loading the ecosystem was determined by computing the Saprobic index. The values obtained do not exceed the eutrophication limits according to the Water Framework Directive, transposed into Romanian legislation by Order 161/2006, with normal concentrations for rheophile ecosystems, as Danube's branches. In this area, water currents and high water turbidity inhibit phytoplankton growth, in contrast to lacustrine ecosystems, where light penetration to depths favors the development of different phytoplankton groups.

  20. Ecotoxicology of bromoacetic acid on estuarine phytoplankton

    International Nuclear Information System (INIS)

    Gordon, Ana R.; Richardson, Tammi L.; Pinckney, James L.

    2015-01-01

    Bromoacetic acid is formed when effluent containing chlorine residuals react with humics in natural waters containing bromide. The objective of this research was to quantify the effects of bromoacetic acid on estuarine phytoplankton as a proxy for ecosystem productivity. Bioassays were used to measure the EC 50 for growth in cultured species and natural marine communities. Growth inhibition was estimated by changes in chlorophyll a concentrations measured by fluorometry and HPLC. The EC 50 s for cultured Thalassiosira pseudonana were 194 mg L −1 , 240 mg L −1 for Dunaliella tertiolecta and 209 mg L −1 for Rhodomonas salina. Natural phytoplankton communities were more sensitive to contamination with an EC 50 of 80 mg L −1 . Discriminant analysis suggested that bromoacetic acid additions cause an alteration of phytoplankton community structure with implications for higher trophic levels. A two-fold EC 50 decrease in mixed natural phytoplankton populations affirms the importance of field confirmation for establishing water quality criteria. - Highlights: • Bromoacetic acid exposure resulted in lethal impacts to estuarine phytoplankton. • Cultured phytoplankton were less sensitive to bromoacetic acid than natural communities. • Lab results should be confirmed with field experiments whenever possible. - The toxicology of haloacetic acids has been studied in freshwater ecosystems, and urbanization of the coastal zone is making effects in marine ecosystems equally relevant.

  1. Triclosan alterations of estuarine phytoplankton community structure.

    Science.gov (United States)

    Pinckney, James L; Thompson, Laura; Hylton, Sarah

    2017-06-15

    Antimicrobial additives in pharmaceutical and personal care products are a major environmental concern due to their potential ecological impacts on aquatic ecosystems. Triclosan (TCS) has been used as an antiseptic, disinfectant, and preservative in various media. The sublethal and lethal effects of TCS on estuarine phytoplankton community composition were investigated using bioassays of natural phytoplankton communities to measure phytoplankton responses to different concentrations of TCS ranging from 1 to 200μgl -1 . The EC 50 (the concentration of an inhibitor where the growth is reduced by half) for phytoplankton groups (diatoms, chlorophytes, cryptophytes) examined in this ranged from 10.7 to 113.8μg TCS l -1 . Exposures resulted in major shifts in phytoplankton community composition at concentrations as low as 1.0μg TCS l -1 . This study demonstrates estuarine ecosystem sensitivity to TCS exposure and highlights potential alterations in phytoplankton community composition at what are typically environmental concentrations of TCS in urbanized estuaries. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Connecting pigment composition and dissolved trace elements to phytoplankton population in the southern Benguela Upwelling zone (St. Helena Bay)

    Science.gov (United States)

    Das, Supriyo Kumar; Routh, Joyanto; Roychoudhury, Alakendra N.; Veldhuis, Marcel J. W.; Ismail, Hassan E.

    2017-12-01

    Rich in upwelled nutrients, the Southern Benguela is one of the most productive ecosystems in the world ocean. However, despite its ecological significance the role of trace elements influencing phytoplankton population in the Southern Benguela Upwelling System (SBUS) has not been thoroughly investigated. Here, we report pigment composition, macronutrients (nitrate, phosphate and silicate) and concentrations of dissolved Cd, Co, Fe and Zn during late austral summer and winter seasons in 2004 to understand the relationship between the selected trace elements and phytoplankton biomass in St. Helena Bay (SHB), which falls within the southern boundary of the SBUS. Chlorophyll a concentrations indicate higher phytoplankton biomass associated with high primary production during late summer in SHB where high diatom population is inferred from the presence of fucoxanthin. Diminished phytoplankton biomass and a shift from diatoms to dinoflagellates as the dominant phytoplankton taxa are indicated by diagnostic pigments during late winter. Dissolved trace elements (Cd, Co and Zn) and macronutrients play a significant role in phytoplankton biomass, and their distribution is affected by biological uptake and export of trace elements. Continuous uptake of Zn by diatoms may cause an onset of Zn depletion leading to a period of extended diatom proliferation during late summer. Furthermore, the transition from diatom to dinoflagellate dominated phytoplankton population is most likely facilitated by depletion of trace elements (Cd and Co) in the water column.

  3. Environmental gradients regulate the spatio-temporal variability of phytoplankton assemblages in the Can Gio Mangrove Biosphere Reserve, Vietnam

    Science.gov (United States)

    Pham, Thanh-Luu

    2017-12-01

    This paper covers spatial and temporal variation in phytoplankton communities and physico-chemical variables in the Can Gio Mangrove Biosphere Reserve (CGMBR), Vietnam, based on field measurement conducted monthly at nine stations during February 2009 to January 2010. Species diversity, richness and phytoplankton abundance were calculated. Canonical Correspondence Analysis (CCA) was used to investigate the relationship between environmental factors and phytoplankton community. A total of 126 species were recorded with a clear dominance of Bacillariophyceae, which formed about 76.4% of the total phytoplankton counts with an annual average of 44.900 cells/L. Other algal classes like Dinophyceae, Cyanophyceae and Chrysophyceae sustained low counts, forming collectively about 14% of the total abundance of phytoplankton. Although Chaetoceros and Coscinodiscus were the most dominant genera, Schroederella and Skeletonema showed high abundance during the studied period. Among the nine environmental parameters tested in this study, salinity, nitrate and ammonium were found to be significantly different between two seasons. On the other hand, no significant difference was found between stations for the studied variables. Results of CCA indicated that phytoplankton assemblage in the CGMBR was influenced by salinity, nitrate and phosphate concentration. This is the first study simultaneously investigating the phytoplankton communities and their environment in this area and it is essential in order to set up the baseline of future studies.

  4. Seasonal Variability of Mesozooplankton Feeding Rates on Phytoplankton in Subtropical Coastal and Estuarine Waters

    Directory of Open Access Journals (Sweden)

    Mianrun Chen

    2017-06-01

    Full Text Available In order to understand how mesozooplankton assemblages influenced phytoplankton in coastal and estuarine waters, we carried out a monthly investigation on mesozooplankton composition at two contrasting stations of Hong Kong coastal and estuarine waters and simultaneously conducted bottle incubation feeding experiments. The assemblage of mesozooplankton was omnivorous at both stations with varying carnivory degree (the degree of feeding preference of protozoa and animal food to phytoplankton and the variations of carnivory degree were significantly associated with microzooplankton biomass (ciliates for the coastal station, both ciliates and dinoflagellates for the estuarine stations and physical environmental parameters (primarily salinity. High carnivory was primarily due to high composition of noctilucales, Corycaeus spp., Oithona spp. and Acartia spp. Results of feeding experiments showed that grazing impacts on phytoplankton ranged from −5.9 to 17.7%, while the mean impacts were just <4% at both stations. The impacts were size-dependent, by which mesozooplankton consumed around 9% of large-sized phytoplankton while indirectly caused an increase of 4% of small-sized phytoplankton. Mesozooplankton clearance rate on phytoplankton, calculated from the log response of chlorophyll a concentrations by the introduction of bulk grazers after 1-day incubation, was significantly reduced by increasing carnivory degree of the mesozooplankton assemblage. The mechanism for the reduction of mesozooplankton clearance rate with increasing carnivory degree was primarily due to less efficient of filtering feeding and stronger trophic cascades due to suppression of microzooplankton. The feeding rates of mesozooplankton on microzooplankton were not obtained in this study, but the trophic cascades indirectly induced by mesozooplankton carnivorous feeding can be observed by the negative clearance rate on small-sized phytoplankton. Overall, the main significance of

  5. Effects of nutrients and zooplankton on the phytoplankton community structure in Marudu Bay

    Science.gov (United States)

    Tan, Kar Soon; Ransangan, Julian

    2017-07-01

    Current study was carried out to provide a better understanding on spatial and temporal variations in the phytoplankton community structure in Marudu Bay, an important nursery ground for fishery resources within the Tun Mustapha Marine Park and Coral Triangle Initiative, and their relationship with environmental variables. Samplings were conducted monthly from April 2014 to April 2015 in Marudu Bay, Malaysia. Water samples were collected for nutrients analysis, zooplankton and phytoplankton counting. Moreover, the in situ environmental parameters were also examined. The field study showed a total of forty seven phytoplankton genera, representative of 33 families were identified. The nutrient concentrations in Marudu Bay was low (mesotrophic) throughout the year, where the phytoplankton community was often dominated by Chaetoceros spp. and Bacteriastrum spp. In general, increase in nitrate concentration triggered the bloom of centric diatom, Chaetoceros spp. and Bacteriastrum spp. in Marudu Bay. However, the bloom of these phytoplankton taxa did not occur in the presence of high ammonia concentration. In addition, high abundance of zooplankton also a limiting factor of the phytoplankton blooms particularly at end of southwest monsoon. High silica concentration promoted the growth of pennate diatoms, Proboscia spp. and Thallassionema spp., but the depletion of silica quickly terminated the bloom. Interestingly, our study showed that Chaetoceros spp., tolerated silica depletion condition, but the average cell size of this taxon reduced significantly. In summary, the phytoplankton community structure in mesotrophic environment is more sensitive to the changes in zooplankton abundance, nutrient concentration and its ratio than that in nutrient rich environments. This study also recommends that bivalve farming at industrial scale is not recommended in Marudu Bay because it potentially depletes the primary productivity hence jeopardizing the availability of live food for

  6. Phospholipid-derived fatty acids as chemotaxonomic markers for phytoplankton: application for inferring phytoplankton composition

    NARCIS (Netherlands)

    Dijkman, N.A.; Kromkamp, J.C.

    2006-01-01

    Phospholipid-derived fatty acids (PLFA) are widely used as chemotaxonomic markers in microbial ecology. In this paper we explore the use of PLFA as chemotaxonomic markers for phytoplankton species. The PLFA composition was determined for 23 species relevant to estuarine phytoplankton. The taxonomic

  7. Retrieval of phytoplankton cell size from chlorophyll a specific absorption and scattering spectra of phytoplankton.

    Science.gov (United States)

    Zhou, Wen; Wang, Guifen; Li, Cai; Xu, Zhantang; Cao, Wenxi; Shen, Fang

    2017-10-20

    Phytoplankton cell size is an important property that affects diverse ecological and biogeochemical processes, and analysis of the absorption and scattering spectra of phytoplankton can provide important information about phytoplankton size. In this study, an inversion method for extracting quantitative phytoplankton cell size data from these spectra was developed. This inversion method requires two inputs: chlorophyll a specific absorption and scattering spectra of phytoplankton. The average equivalent-volume spherical diameter (ESD v ) was calculated as the single size approximation for the log-normal particle size distribution (PSD) of the algal suspension. The performance of this method for retrieving cell size was assessed using the datasets from cultures of 12 phytoplankton species. The estimations of a(λ) and b(λ) for the phytoplankton population using ESD v had mean error values of 5.8%-6.9% and 7.0%-10.6%, respectively, compared to the a(λ) and b(λ) for the phytoplankton populations using the log-normal PSD. The estimated values of C i ESD v were in good agreement with the measurements, with r 2 =0.88 and relative root mean square error (NRMSE)=25.3%, and relatively good performances were also found for the retrieval of ESD v with r 2 =0.78 and NRMSE=23.9%.

  8. Lipid-rich and protein-poor carbon allocation patterns of phytoplankton in the northern Chukchi Sea, 2011

    Science.gov (United States)

    Yun, Mi Sun; Joo, Hui Tae; Park, Jung Woo; Kang, Jae Joong; Kang, Sung-Ho; Lee, Sang H.

    2018-04-01

    The carbon allocations of phytoplankton into different photosynthetic end products (lipids, LMWM, polysaccharides, and proteins) were determined to understand physiological conditions of phytoplankton in the northern Chukchi Sea during the Korean Arctic expedition, 2011, using the 13C isotope tracer technique. The carbon allocation rates of lipids, LMWM, polysaccharides, and proteins were 0.00009-0.00062 h-1, 0.00001-0.00049 h-1, 0.00001-0.00025 h-1, and 0.00001-0.00062 h-1 within the euphotic depths from surface to 1% light depths during our cruise period, respectively. Significant relationships between protein production rates and chlorophyll a concentrations (large and total) were found in this study. Moreover, we found a significant negative relationship between lipid production rates and ammonium concentrations. These relationships match well with the previous results for environmental/physiological conditions for phytoplankton growth. Overall, phytoplankton allocated more photosynthetic carbon into lipids (42.5 ± 17.7%) whereas relatively lower to proteins (20.4 ± 15.5%) in this study. The lipid-rich and protein-poor allocation patterns in this study suggest that phytoplankton in the northern Chukchi Sea were in a stationary growth phase under nutrient deficient condition based on biological and environmental conditions observed during our study period. Based on comparison with the previous studies in the northern Bering Sea and southern Chukchi Sea, we found that the photosynthetic carbon allocation patterns depending on physiological status of phytoplankton under the different growth and/or nutrient conditions could be largely vary at different regions in the Arctic Ocean. More intensive research on the physiological status of phytoplankton is further required to determine how phytoplankton response to the changing environmental conditions and consequently how they impact on higher trophic levels in marine ecosystems in the Arctic Ocean.

  9. Decomposition of lake phytoplankton. 1

    International Nuclear Information System (INIS)

    Hansen, L.; Krog, G.F.; Soendergaard, M.

    1986-01-01

    Short-time (24 h) and long-time (4-6 d) decomposition of phytoplankton cells were investigasted under in situ conditions in four Danish lakes. Carbon-14-labelled, dead algae were exposed to sterile or natural lake water and the dynamics of cell lysis and bacterial utilization of the leached products were followed. The lysis process was dominated by an initial fast water extraction. Within 2 to 4 h from 4 to 34% of the labelled carbon leached from the algal cells. After 24 h from 11 to 43% of the initial particulate carbon was found as dissolved carbon in the experiments with sterile lake water; after 4 to 6 d the leaching was from 67 to 78% of the initial 14 C. The leached compounds were utilized by bacteria. A comparison of the incubations using sterile and natural water showed that a mean of 71% of the lysis products was metabolized by microorganisms within 24 h. In two experiments the uptake rate equalled the leaching rate. (author)

  10. Decomposition of lake phytoplankton. 2

    International Nuclear Information System (INIS)

    Hansen, L.; Krog, G.F.; Soendergaard, M.

    1986-01-01

    The lysis process of phytoplankton was followed in 24 h incubations in three Danish lakes. By means of gel-chromatography it was shown that the dissolved carbon leaching from different algal groups differed in molecular weight composition. Three distinct molecular weight classes (>10,000; 700 to 10,000 and < 700 Daltons) leached from blue-green algae in almost equal proportion. The lysis products of spring-bloom diatoms included only the two smaller size classes, and the molecules between 700 and 10,000 Daltons dominated. Measurements of cell content during decomposition of the diatoms revealed polysaccharides and low molecular weight compounds to dominate the lysis products. No proteins were leached during the first 24 h after cell death. By incubating the dead algae in natural lake water, it was possible to detect a high bacterial affinity towards molecules between 700 and 10,000 Daltons, although the other size classes were also utilized. Bacterial transformation of small molecules to larger molecules could be demonstrated. (author)

  11. Does ecosystem variability explain phytoplankton diversity? Solving an ecological puzzle with long-term data sets

    Science.gov (United States)

    Sarker, Subrata; Lemke, Peter; Wiltshire, Karen H.

    2018-05-01

    Explaining species diversity as a function of ecosystem variability is a long-term discussion in community-ecology research. Here, we aimed to establish a causal relationship between ecosystem variability and phytoplankton diversity in a shallow-sea ecosystem. We used long-term data on biotic and abiotic factors from Helgoland Roads, along with climate data to assess the effect of ecosystem variability on phytoplankton diversity. A point cumulative semi-variogram method was used to estimate the long-term ecosystem variability. A Markov chain model was used to estimate dynamical processes of species i.e. occurrence, absence and outcompete probability. We identified that the 1980s was a period of high ecosystem variability while the last two decades were comparatively less variable. Ecosystem variability was found as an important predictor of phytoplankton diversity at Helgoland Roads. High diversity was related to low ecosystem variability due to non-significant relationship between probability of a species occurrence and absence, significant negative relationship between probability of a species occurrence and probability of a species to be outcompeted by others, and high species occurrence at low ecosystem variability. Using an exceptional marine long-term data set, this study established a causal relationship between ecosystem variability and phytoplankton diversity.

  12. Phytoplankton ice-edge blooms in the marginal ice zone at Princess Astrid Coast in Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Verlecar, X.N.; Dhargalkar, V.K.; Goswami, S.C.; Mhamal, N.P.

    dominated the bloom conditions and nannoplankton (5 to 20 mu m) prevail the non-bloom periods while the picoplankton (less than 5 mu m) constituted a minor fraction during most of the period. Weekly changes in phytoplankton showed inverse relationship...

  13. Elevated temperature increases carbon and nitrogen fluxes between phytoplankton and heterotrophic bacteria through physical attachment

    KAUST Repository

    Arandia-Gorostidi, Nestor

    2016-12-06

    Quantifying the contribution of marine microorganisms to carbon and nitrogen cycles and their response to predicted ocean warming is one of the main challenges of microbial oceanography. Here we present a single-cell NanoSIMS isotope analysis to quantify C and N uptake by free-living and attached phytoplankton and heterotrophic bacteria, and their response to short-term experimental warming of 4 °C. Elevated temperature increased total C fixation by over 50%, a small but significant fraction of which was transferred to heterotrophs within 12 h. Cell-to-cell attachment doubled the secondary C uptake by heterotrophic bacteria and increased secondary N incorporation by autotrophs by 68%. Warming also increased the abundance of phytoplankton with attached heterotrophs by 80%, and promoted C transfer from phytoplankton to bacteria by 17% and N transfer from bacteria to phytoplankton by 50%. Our results indicate that phytoplankton-bacteria attachment provides an ecological advantage for nutrient incorporation, suggesting a mutualistic relationship that appears to be enhanced by temperature increases.

  14. Phytoplankton biovolume is independent from the slope of the size spectrum in the oligotrophic atlantic ocean

    KAUST Repository

    Moreno-Ostos, Enrique

    2015-08-06

    Modelling the size-abundance spectrum of phytoplankton has proven to be a very useful tool for the analysis of physical-biological coupling and the vertical flux of carbon in oceanic ecosystems at different scales. A frequent observation relates high phytoplankton biovolume in productive regions with flatter spectrum slope and the opposite in oligotrophic ecosystems. Rather than this, the relationship between high biovolume phytoplankton assemblages and flatter size-abundance spectra does not correspond with measurements of the phytoplankton community in the Atlantic Ocean open waters. As part of the Malaspina Circunnavegation Expedition, sixty seven sampling stations within the Atlantic Ocean covering six oceanographic provinces, at different seasons, produced a complete set of phytoplankton size-spectra whose slope and biovolume did not show any obvious interrelation. In these oligotrophic sites, small (procaryotes) and medium-size (nanoplankton) cells are responsible for the most part of biovolume, and their response to environmental conditions does not apply to changes in the size-abundance spectrum slope as expected in richer, large-cell dominated ecosystems.

  15. Elevated temperature increases carbon and nitrogen fluxes between phytoplankton and heterotrophic bacteria through physical attachment

    KAUST Repository

    Arandia-Gorostidi, Nestor; Weber, Peter K; Alonso-Sá ez, Laura; Moran, Xose Anxelu G.; Mayali, Xavier

    2016-01-01

    Quantifying the contribution of marine microorganisms to carbon and nitrogen cycles and their response to predicted ocean warming is one of the main challenges of microbial oceanography. Here we present a single-cell NanoSIMS isotope analysis to quantify C and N uptake by free-living and attached phytoplankton and heterotrophic bacteria, and their response to short-term experimental warming of 4 °C. Elevated temperature increased total C fixation by over 50%, a small but significant fraction of which was transferred to heterotrophs within 12 h. Cell-to-cell attachment doubled the secondary C uptake by heterotrophic bacteria and increased secondary N incorporation by autotrophs by 68%. Warming also increased the abundance of phytoplankton with attached heterotrophs by 80%, and promoted C transfer from phytoplankton to bacteria by 17% and N transfer from bacteria to phytoplankton by 50%. Our results indicate that phytoplankton-bacteria attachment provides an ecological advantage for nutrient incorporation, suggesting a mutualistic relationship that appears to be enhanced by temperature increases.

  16. Mechanisms shaping size structure and functional diversity of phytoplankton communities in the ocean

    Science.gov (United States)

    Acevedo-Trejos, Esteban; Brandt, Gunnar; Bruggeman, Jorn; Merico, Agostino

    2015-01-01

    The factors regulating phytoplankton community composition play a crucial role in structuring aquatic food webs. However, consensus is still lacking about the mechanisms underlying the observed biogeographical differences in cell size composition of phytoplankton communities. Here we use a trait-based model to disentangle these mechanisms in two contrasting regions of the Atlantic Ocean. In our model, the phytoplankton community can self-assemble based on a trade-off emerging from relationships between cell size and (1) nutrient uptake, (2) zooplankton grazing, and (3) phytoplankton sinking. Grazing ‘pushes’ the community towards larger cell sizes, whereas nutrient uptake and sinking ‘pull’ the community towards smaller cell sizes. We find that the stable environmental conditions of the tropics strongly balance these forces leading to persistently small cell sizes and reduced size diversity. In contrast, the seasonality of the temperate region causes the community to regularly reorganize via shifts in species composition and to exhibit, on average, bigger cell sizes and higher size diversity than in the tropics. Our results raise the importance of environmental variability as a key structuring mechanism of plankton communities in the ocean and call for a reassessment of the current understanding of phytoplankton diversity patterns across latitudinal gradients. PMID:25747280

  17. SOME ENVIRONMENTAL FEATURES OF PHYTOPLANKTON

    Directory of Open Access Journals (Sweden)

    Taha A. Al-Tayyar

    2013-05-01

    Full Text Available Todefine the biological features of phytoplankton in Mosul  Dam  Lake, monthly samples were collectedalong a year from September 2003 to August 2004. Consisting thermalstratification and turn over periods from four locations in the main lake andanother location in the regulating lake. Total numbers of algae  reached 2300 cell/ml in the main lake and 1100cell/ml in the regulating lake.Bacillariophyta were dominant with a maximum number of 1400 cell/ml in autumn. Chlorophytawere dominant in autumn also with 550 cell/ml. Ten genus of Chlorophyta wereappeared in this water body: Cosmarium, Chlorella, Spirogyra, Scendesmus, Pediastrum, Tetraedron, Quadrigula, Ankiseradosm, Pandorina, and Straurastrum.Seven genus of Bacillariophyta were noticeable. Some genus of Cyanophyta was recorded as Aphanocapsa. In addition someEuglenophyta spp. were occurred in the main lake and the regulating lake also. On thebasis of these algae abundance, the lake is undergoing cultural Eutrophication.It has passed in mesotrophic state (the middle trophic state ofEutrophication. Some genera which were appeared are the indication ofeutrophic state.Totalplate count bacteria ranged from 400-1700 cell/ ml in the main lake and 200-950 cell/ml in the regulating lakewere also recorded. Coliform bacteria were founded with most probablenumber  reached 460 cell/100ml in themain lake and 150 cell/100ml in the regulating lake. Therefore, the lake wateris classified as moderate pure and considering a good source of raw water supplywith all treatment units and safe for swimming and recreational uses.

  18. Low doses effects and gamma radiations low dose rates

    International Nuclear Information System (INIS)

    Averbeck, D.

    1999-01-01

    This expose wishes for bringing some definitions and base facts relative to the problematics of low doses effects and low dose rates effects. It shows some already used methods and some actual experimental approaches by focusing on the effects of ionizing radiations with a low linear energy transfer. (N.C.)

  19. DMSP synthesis and exudation in phytoplankton : a modeling approach

    NARCIS (Netherlands)

    Laroche, D; Vézina, A.F; Levasseur, M; Gosselin, M; Stefels, J.; Keller, M.D; Matrai, P.A; Kwint, R.L J

    1999-01-01

    In the marine environment, phytoplankton are the fundamental producers of dimethylsulfoniopropionate (DMSP), the precursor of the climatically active gas dimethylsulfide (DMS). DMSP is released by exudation, cell autolysis, and zooplankton grazing during phytoplankton blooms. In this study, we

  20. Phytoplankton and nutrients studies in Magu bay, Speke gulf, Lake ...

    African Journals Online (AJOL)

    Phytoplankton were generally dominated by the cyanobacteria Microcystis and Anabaena species though the diatoms Nitzschia and Melosira species were more abundant in some sampling ... Phytoplankton production was possibly light limited in areas with simultaneously high nutrient concentrations and high turbidity.

  1. Biomass relations between phytoplankton and zooplankton in Goa waters

    Digital Repository Service at National Institute of Oceanography (India)

    Pant, A.; Matondkar, S.G.P.; Goswami, S.C.

    Biomass of phytoplankton and zooplankton, measured as particulate oxidizable carbon, shows that at shallowest stations (5 m) there is large excess of phytoplankton organic carbon over zooplankton carbon in all the samples There is no significant...

  2. phytoplankton diversity indices of Osse River, Edo State, Nigeria

    African Journals Online (AJOL)

    USER

    The phytoplankton diversity indices of Osse River, Edo State, Nigeria, were investigated monthly from January ... In terms of abundance, Bacillariophyceae had the highest distribution of phytoplankton (79.00%), ...... erosion beach in Lagos.

  3. Bivalve grazing can shape phytoplankton communities

    Science.gov (United States)

    Lucas, Lisa; Cloern, James E.; Thompson, Janet K.; Stacey, Mark T.; Koseff, Jeffrey K.

    2016-01-01

    The ability of bivalve filter feeders to limit phytoplankton biomass in shallow waters is well-documented, but the role of bivalves in shaping phytoplankton communities is not. The coupled effect of bivalve grazing at the sediment-water interface and sinking of phytoplankton cells to that bottom filtration zone could influence the relative biomass of sinking (diatoms) and non-sinking phytoplankton. Simulations with a pseudo-2D numerical model showed that benthic filter feeding can interact with sinking to alter diatom:non-diatom ratios. Cases with the smallest proportion of diatom biomass were those with the fastest sinking speeds and strongest bivalve grazing rates. Hydrodynamics modulated the coupled sinking-grazing influence on phytoplankton communities. For example, in simulations with persistent stratification, the non-sinking forms accumulated in the surface layer away from bottom grazers while the sinking forms dropped out of the surface layer toward bottom grazers. Tidal-scale stratification also influenced vertical gradients of the two groups in opposite ways. The model was applied to Suisun Bay, a low-salinity habitat of the San Francisco Bay system that was transformed by the introduction of the exotic clam Potamocorbula amurensis. Simulation results for this Bay were similar to (but more muted than) those for generic habitats, indicating that P. amurensis grazing could have caused a disproportionate loss of diatoms after its introduction. Our model simulations suggest bivalve grazing affects both phytoplankton biomass and community composition in shallow waters. We view these results as hypotheses to be tested with experiments and more complex modeling approaches.

  4. Spatial dynamics of a nutrient-phytoplankton system with toxic effect on phytoplankton

    DEFF Research Database (Denmark)

    Chakraborty, Subhendu; Tiwari, P. K.; Misra, A. K.

    2015-01-01

    The production of toxins by some species of phytoplankton is known to have several economic, ecological, and human health impacts. However, the role of toxins on the spatial distribution of phytoplankton is not well understood. In the present study, the spatial dynamics of a nutrient-phytoplankto...... patterns, like stripes, spots, and the mixture of them depending on the toxicity level. We also observe that the distribution of nutrient and phytoplankton shows spatiotemporal oscillation for certain toxicity level. (C) 2015 Elsevier Inc. All rights reserved....

  5. Uncertainty Analysis of Phytoplankton Dynamics in Coastal Waters

    NARCIS (Netherlands)

    Niu, L.

    2015-01-01

    There is an increasing concern about the interactions between phytoplankton and coastal ecosystems, especially on the negative effects from coastal eutrophication and phytoplankton blooms. As the key indicator of the coastal ecosystem, phytoplankton plays an important role in the whole impact-effect

  6. Spatial-temporal distribution of phytoplankton pigments in relation to nutrient status in Jiaozhou Bay, China

    Science.gov (United States)

    Yao, Peng; Yu, Zhigang; Deng, Chunmei; Liu, Shuxia; Zhen, Yu

    2010-10-01

    We conducted studies of phytoplankton and hydrological variables in a semi-enclosed bay in northern China to understand the spatial-temporal variability and relationship between these variables. Samples were collected during seven cruises in Jiaozhou Bay from November 2003 to October 2004, and were analyzed for temperature, nutrients and phytoplankton pigments. Pigments from eight possible phytoplankton classes (Diatoms, Dinoflagellates, Chlorophyceae, Prasinophyceae, Chrysophyceae, Haptophyceae, Cryptophyceae and Caynophyceae) were detected in surface water by high performance liquid chromatography (HPLC). Phytoplankton pigment and nutrient concentrations in Jiaozhou Bay were spatially and temporally variable, and most of them were highest in the northern and eastern parts of the sampling regions in spring (May) and summer (August), close to areas of shellfish culturing, river estuaries, dense population and high industrialization, reflecting human activities. Chlorophyll a was recorded in all samples, with an annual mean concentration of 1.892 μg L -1, and fucoxanthin was the most abundant accessory pigment, with a mean concentration of 0.791 μg L -1. The highest concentrations of chlorophyll a (15.299 μg L -1) and fucoxanthin (9.417 μg L -1) were observed in May 2004 at the station close to the Qingdao Xiaogang Ferry, indicating a spring bloom of Diatoms in this area. Although chlorophyll a and other biomarker pigments showed significant correlations, none of them showed strong correlations with temperature and nutrients, suggesting an apparent de-coupling between the pigments and these hydrological variables. The nutrient composition and phytoplankton community composition of Jiaozhou Bay have changed significantly in the past several decades, reflecting the increasing nutrient concentrations and decline of phytoplankton cell abundance. The unchanged total chlorophyll a levels indicated that smaller species have filled the niche vacated by the larger

  7. Connections between the growth of Arctica islandica and phytoplankton dynamics on the Faroe Shelf

    Science.gov (United States)

    Bonitz, Fabian; Andersson, Carin; Trofimova, Tamara

    2017-04-01

    In this study we use molluscan sclerochronological techniques in order to obtain closer insights into environmental and ecological dynamics of Faroe Shelf waters. The Faroe Shelf represents a special ecosystem with rich benthic and neritic communities, which also have great importance for many economically relevant fish stocks. Thus, a better understanding of seasonal and year-to-year phytoplankton and stratification dynamics would be useful because they also have implications for higher trophic levels. The water masses of the Faroe Shelf are fairly homogenous and isolated from off-shelf waters but at a certain depth, which is referred to as transition zone, seasonal stratification and horizontal exchange occur. Systematic observations and phytoplankton dynamic investigations have only been performed during the last 29 years but longer records are missing. Thus, we use the growth increment variability in long-lived Arctica islandica shells from the transition zone of the eastern Faroe Shelf to evaluate its potential to estimate on-shelf phytoplankton and stratification dynamics since previous studies have shown that the growth of A. islandica is highly dependent on food availability. We have built a shell-based master-chronology reaching back to the 17th century. Comparisons between the growth indices of our chronology and fluorescence data reveal significant positive relationships. In combination with an index that accounts for stratification even stronger correlations are obtained. This indicates that the growth of A. islandica is largely influenced by a combination of how much phytoplankton is produced and how much actually reaches the bottom, i.e. how well-mixed the water column is. Further significant positive correlations can also be found between the growth indices and other primary productivity data from the Faroe Shelf. In conclusion, our results suggest that the growth indices can be related to year-to-year changes in phytoplankton production and

  8. Phytoplankton Regulation in a Eutrophic Tidal River (San Joaquin River, California

    Directory of Open Access Journals (Sweden)

    Alan D. Jassby

    2005-03-01

    Full Text Available As in many U.S. estuaries, the tidal San Joaquin River exhibits elevated organic matter production that interferes with beneficial uses of the river, including fish spawning and migration. High phytoplankton biomass in the tidal river is consequently a focus of management strategies. An unusually long and comprehensive monitoring dataset enabled identification of the determinants of phytoplankton biomass. Phytoplankton carrying capacity may be set by nitrogen or phosphorus during extreme drought years but, in most years, growth rate is light-limited. The size of the annual phytoplankton bloom depends primarily on river discharge during late spring and early summer, which determines the cumulative light exposure in transit downstream. The biomass-discharge relationship has shifted over the years, for reasons as yet unknown. Water diversions from the tidal San Joaquin River also affect residence time during passage downstream and may have resulted in more than a doubling of peak concentration in some years. Dam construction and accompanying changes in storage-and-release patterns from upstream reservoirs have caused a long-term decrease in the frequency of large blooms since the early 1980s, but projected climate change favors a future increase. Only large decreases in nonpoint nutrient sources will limit phytoplankton biomass reliably. Growth rate and concentration could increase if nonpoint source management decreases mineral suspensoid load but does not decrease nutrient load sufficiently. Small changes in water storage and release patterns due to dam operation have a major influence on peak phytoplankton biomass, and offer a near-term approach for management of nuisance algal blooms.

  9. Phytoplankton-bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge.

    Science.gov (United States)

    Bertrand, Erin M; McCrow, John P; Moustafa, Ahmed; Zheng, Hong; McQuaid, Jeffrey B; Delmont, Tom O; Post, Anton F; Sipler, Rachel E; Spackeen, Jenna L; Xu, Kai; Bronk, Deborah A; Hutchins, David A; Allen, Andrew E

    2015-08-11

    Southern Ocean primary productivity plays a key role in global ocean biogeochemistry and climate. At the Southern Ocean sea ice edge in coastal McMurdo Sound, we observed simultaneous cobalamin and iron limitation of surface water phytoplankton communities in late Austral summer. Cobalamin is produced only by bacteria and archaea, suggesting phytoplankton-bacterial interactions must play a role in this limitation. To characterize these interactions and investigate the molecular basis of multiple nutrient limitation, we examined transitions in global gene expression over short time scales, induced by shifts in micronutrient availability. Diatoms, the dominant primary producers, exhibited transcriptional patterns indicative of co-occurring iron and cobalamin deprivation. The major contributor to cobalamin biosynthesis gene expression was a gammaproteobacterial population, Oceanospirillaceae ASP10-02a. This group also contributed significantly to metagenomic cobalamin biosynthesis gene abundance throughout Southern Ocean surface waters. Oceanospirillaceae ASP10-02a displayed elevated expression of organic matter acquisition and cell surface attachment-related genes, consistent with a mutualistic relationship in which they are dependent on phytoplankton growth to fuel cobalamin production. Separate bacterial groups, including Methylophaga, appeared to rely on phytoplankton for carbon and energy sources, but displayed gene expression patterns consistent with iron and cobalamin deprivation. This suggests they also compete with phytoplankton and are important cobalamin consumers. Expression patterns of siderophore- related genes offer evidence for bacterial influences on iron availability as well. The nature and degree of this episodic colimitation appear to be mediated by a series of phytoplankton-bacterial interactions in both positive and negative feedback loops.

  10. The development and decline of phytoplankton blooms in the southern Benguela upwelling region

    International Nuclear Information System (INIS)

    Brown, P.C.

    1986-10-01

    Productivity/chlorophyll a relationship are investigated with a view to estimating phytoplankton productivity from extensive chlorophyll a measurements in the southern Benguela region. Phytoplankton bloom dynamics in newly upwelled water off the Cape Peninsula are investigated on five different occasions during the upwelling season. A drogue was used to tag a 'parcel' of upwelled water which was monitored for between 4 and 8 days. In upwelling source water, mean chlorophyll a concentrations were typically low (0.7 mg.m -3 ) and nutrient concentrations were high (nitrates, silicates and phosphates were 20.8, 16.6 and 1.88 mmol.m -3 respectively). Along the drogue tracks nutrients decreased rapidly in the euphotic zone as chlorophyll increased to peak at concentrations of up to 26 mg.m -3 . Elemental changes in nitrates, silicates, phosphates and oxygen were used to estimate primary productivity. These 'Redfield productivity estimates' were similar to 14 C-uptake productivity but lower than estimates obtained from changes in particle volume. Daily rates of 14 C-uptake water column productivity ranged between 0.94 and 14.01 g C.m -2 .d -1 (mean 3.80 g C.m -2 .d -1 ) and were similar to or higher than productivity estimates reported for other upwelling areas. Phytoplankton biomass in the upper 50 metres ranged between 8 and 506 mg chll a. m -2 (mean 208 mg chll a.m -2 ). The temporal scale of phytoplankton bloom development was investigated in terms of changes in chlorophyll a concentrations in the euphotic zone. The build up and decline of the primary phytoplankton (diatom) bloom in newly upwelled water occurred within 6-8 days. The initiation of blooming was controlled by the stability of the water body. The decline of the bloom was associated with reduced nutrient levels and is considered to result mainly from phytoplankton cells sinking out of the surface layers

  11. Phytoplankton abundance, dominance and coexistence in an eutrophic reservoir in the state of Pernambuco, Northeast Brazil.

    Science.gov (United States)

    Lira, Giulliari A S T; Araújo, Elcida L; Bittencourt-Oliveira, Maria Do Carmo; Moura, Ariadne N

    2011-12-01

    The present study reports the phytoplankton abundance, dominance and co-existence relationships in the eutrophic Carpina reservoir, Pernambuco, Brazil. Sampling was carried out at six different depths bimonthly at a single reservoir spanning two climatic periods: dry season (January, September, and November 2006) and rainy season (March, May, and July 2006). Density, abundance, dominance, specific diversity and equitability of the community were determined, along with chlorophyll a, and physical and chemical variables of the environment. Eight species were considered abundant, and their densities corresponded to more than 90% of the total phytoplankton community quantified. Cyanobacteria represented more than 80% of this density. Cylindrospermopsis raciborskii was the only dominant taxon in the dry season, and was co-dominant in the rainy season. C. raciborskii, Planktothrix agardhii and Geitlerinema amphibium had the greatest densities and lowest vertical variation coefficients. The statistical analysis indicated relationships with vertical and seasonal variations in the phytoplankton community and the following variables: total dissolved solids, water temperature, electrical conductivity and pH. The changes in the environmental variables were discrete and regulated by the establishment of precipitation however, they were able to promote vertical and seasonal instability in the structure of the phytoplankton community.

  12. Phytoplankton of the North Sea and its dynamics: A review

    Science.gov (United States)

    Reid, P. C.; Lancelot, C.; Gieskes, W. W. C.; Hagmeier, E.; Weichart, G.

    microscopic observations has been documented by measurements of taxon-specific pigments such as chlorophyll b (green algae), alloxanthin (Cryptophyceae) and 19' - hexanolyloxyfucoxanthin (Prymnesiophyceae or Haptophyceae). Analysis of time series of satellite images is a promising way to assess in a quantitative and, more important, synoptic way the patchy distribution of phytoplankton over large regions. Growth processes of the phytoplankton respond according to variables amenable to such satellite remote sensing. Empirical and theoretical relationships that can be established between chlorophyll a, 14C uptake, turbidity, stratification, suspended sediment type, irradiance and temperature in some well-investigated areas make remote sensing a potential tool to obtain reliable estimates of primary production in the whole North Sea. The 14C method for estimates of the rate of algal growth processes appears to agree reasonably well with other methods, both involving incubation of samples and in situ measurements of temporal changes of oxygen and pH. The level of net primary production is 250 g C.m -2.a -1 in the central North Sea, 150 to 200 g C.m -2.a -1 in the northern North Sea, and 200 g in the South. The main metabolic processes involved in phytoplankton growth have been modelled mathematically in terms of the most important controlling environmental parameters. Such parameters comprise not only those of a chemical signature (micro- and macronutrients, both inorganic and organic) but also physical effects of vertical mixing and sinking, and biological effects including allelopathic interactions, antibiotic excretions, vertical migration, and mortality due to grazing and parasitism. The balance between primary production and consumption of organic matter appears to vary both geographically and seasonally. The process of regeneration of primary products both in the water column and in and near the bottom seems to be of major importance. Future research should center around a

  13. Low-dose effects of hormones and endocrine disruptors.

    Science.gov (United States)

    Vandenberg, Laura N

    2014-01-01

    Endogenous hormones have effects on tissue morphology, cell physiology, and behaviors at low doses. In fact, hormones are known to circulate in the part-per-trillion and part-per-billion concentrations, making them highly effective and potent signaling molecules. Many endocrine-disrupting chemicals (EDCs) mimic hormones, yet there is strong debate over whether these chemicals can also have effects at low doses. In the 1990s, scientists proposed the "low-dose hypothesis," which postulated that EDCs affect humans and animals at environmentally relevant doses. This chapter focuses on data that support and refute the low-dose hypothesis. A case study examining the highly controversial example of bisphenol A and its low-dose effects on the prostate is examined through the lens of endocrinology. Finally, the chapter concludes with a discussion of factors that can influence the ability of a study to detect and interpret low-dose effects appropriately. © 2014 Elsevier Inc. All rights reserved.

  14. Dose-effect studies with inhaled plutonium in beagles

    International Nuclear Information System (INIS)

    Anon.

    1982-01-01

    Data are presented for all dogs employed in current life-span dose effect studies with inhaled 239 PuO 2 , and 239 Pu nitrate. Information is presented on the estimated initial alveolar deposition, based on external thorax counts and on estimated lung weights at time of exposure. Information is also provided on the current interpretation of the most prominent clinical-pathological features associated with the death of animals

  15. Phytoplankton community characteristics of the icebound season ...

    African Journals Online (AJOL)

    The taxonomic structure and spatial variability of phytoplankton abundance in the icebound season was obtained from the Zhalong Wetland. A total of 109 taxa were identified in all samples, 92 taxa occurring in at least two samples or the percentages over 1% in at least one sample were utilized in further study. The algal ...

  16. Algae, phytoplankton and eutrophication research and management ...

    African Journals Online (AJOL)

    The role of algal and phytoplankton research and the focus shift to cyanobacteria, because of eutrophication in South African aquatic systems, are highlighted, which indicates the different modelling and management methods that have been used and tested. Recommendations are made for future research. Keywords: ...

  17. Immuno flow cytometry in marine phytoplankton research

    NARCIS (Netherlands)

    Peperzak, L; Vrieling, EG; Sandee, B; Rutten, T

    The developments in the combination of flow cytometry and immunology as a tool to identify, count and examine marine phytoplankton cells are reviewed. The concepts of immunology and now cytometry are described. A distinction is made between quantitative and qualitative immunofluorescence.

  18. Phytoplankton assemblage and environmental variables in Ogun ...

    African Journals Online (AJOL)

    It was carried out between February and July, 2014, in three distinct zones in Ogun State coastal estuary: brush park (Zone I), open water (Zone II) and wetland (Zone III). Data collected were subjected to community structure analysis using trophic state index, species richness and diversity indices. A total of 42 phytoplankton ...

  19. Earth's Most Important Producers: Meet the Phytoplankton!

    Science.gov (United States)

    Marrero, Meghan E.; Stevens, Nicole

    2011-01-01

    The ocean is home to some of Earth's most important producers. Single-celled organisms in the ocean are responsible for more than half of Earth's productivity, as well as most of its oxygen. Phytoplankton are single-celled, plantlike organisms. That is, they have chloroplasts and perform photosynthesis, but are not true plants, which are typically…

  20. Quantifying interspecific coagulation efficiency of phytoplankton

    DEFF Research Database (Denmark)

    Hansen, J.L.S.; Kiørboe, Thomas

    1997-01-01

    . nordenskjoeldii. Mutual coagulation between Skeletonema costatum and the non-sticky cel:ls of Ditylum brightwellii also proceeded with hall the efficiency of S. costatum alone. The latex beads were suitable to be used as 'standard particles' to quantify the ability of phytoplankton to prime aggregation...

  1. Scaling laws in phytoplankton nutrient uptake affinity

    DEFF Research Database (Denmark)

    Lindemann, Christian; Fiksen, Øyvind; Andersen, Ken Haste

    2016-01-01

    instantaneously. Here we provide empirical evidence that the perfect sink strategy is not common in phytoplankton. Although small cells are indeed favored by a large surface to volume ratio, we show that they are punished by higher relative investment cost in order to fully benefit from the larger surface...

  2. The dynamical landscape of marine phytoplankton diversity

    Science.gov (United States)

    Lévy, Marina; Jahn, Oliver; Dutkiewicz, Stephanie; Follows, Michael J.; d'Ovidio, Francesco

    2015-01-01

    Observations suggest that the landscape of marine phytoplankton assemblage might be strongly heterogeneous at the dynamical mesoscale and submesoscale (10–100 km, days to months), with potential consequences in terms of global diversity and carbon export. But these variations are not well documented as synoptic taxonomic data are difficult to acquire. Here, we examine how phytoplankton assemblage and diversity vary between mesoscale eddies and submesoscale fronts. We use a multi-phytoplankton numerical model embedded in a mesoscale flow representative of the North Atlantic. Our model results suggest that the mesoscale flow dynamically distorts the niches predefined by environmental contrasts at the basin scale and that the phytoplankton diversity landscape varies over temporal and spatial scales that are one order of magnitude smaller than those of the basin-scale environmental conditions. We find that any assemblage and any level of diversity can occur in eddies and fronts. However, on a statistical level, the results suggest a tendency for larger diversity and more fast-growing types at fronts, where nutrient supplies are larger and where populations of adjacent water masses are constantly brought into contact; and lower diversity in the core of eddies, where water masses are kept isolated long enough to enable competitive exclusion. PMID:26400196

  3. Ecotoxicology of bromoacetic acid on estuarine phytoplankton.

    Science.gov (United States)

    Gordon, Ana R; Richardson, Tammi L; Pinckney, James L

    2015-11-01

    Bromoacetic acid is formed when effluent containing chlorine residuals react with humics in natural waters containing bromide. The objective of this research was to quantify the effects of bromoacetic acid on estuarine phytoplankton as a proxy for ecosystem productivity. Bioassays were used to measure the EC50 for growth in cultured species and natural marine communities. Growth inhibition was estimated by changes in chlorophyll a concentrations measured by fluorometry and HPLC. The EC50s for cultured Thalassiosira pseudonana were 194 mg L(-1), 240 mg L(-1) for Dunaliella tertiolecta and 209 mg L(-1) for Rhodomonas salina. Natural phytoplankton communities were more sensitive to contamination with an EC50 of 80 mg L(-1). Discriminant analysis suggested that bromoacetic acid additions cause an alteration of phytoplankton community structure with implications for higher trophic levels. A two-fold EC50 decrease in mixed natural phytoplankton populations affirms the importance of field confirmation for establishing water quality criteria. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Distribution of nutrients, chlorophyll and phytoplankton primary ...

    African Journals Online (AJOL)

    Distribution of nutrients, chlorophyll and phytoplankton primary production in ... Two cruises were undertaken in the vicinity of the Cape Frio upwelling cell ... and concentrations of nitrate, phosphate, silicate, oxygen and chlorophyll a. ... Estimates of the annual primary production for each of the water bodies were calculated.

  5. Network of interactions between ciliates and phytoplankton during spring

    Directory of Open Access Journals (Sweden)

    Thomas ePosch

    2015-11-01

    Full Text Available The annually recurrent spring phytoplankton blooms in freshwater lakes initiate pronounced successions of planktonic ciliate species. Although there is considerable knowledge on the taxonomic diversity of these ciliates, their species-specific interactions with other microorganisms are still not well understood. Here we present the succession patterns of 20 morphotypes of ciliates during spring in Lake Zurich, Switzerland, and we relate their abundances to phytoplankton genera, flagellates, heterotrophic bacteria, and abiotic parameters. Interspecific relationships were analyzed by contemporaneous correlations and time-lagged co-occurrence and visualized as association networks. The contemporaneous network pointed to the pivotal role of distinct ciliate species (e.g., Balanion planctonicum, Rimostrombidium humile as primary consumers of cryptomonads, revealed a clear overclustering of mixotrophic / omnivorous species, and highlighted the role of Halteria / Pelagohalteria as important bacterivores. By contrast, time-lagged statistical approaches (like local similarity analyses, LSA proved to be inadequate for the evaluation of high-frequency sampling data. LSA led to a conspicuous inflation of significant associations, making it difficult to establish ecologically plausible interactions between ciliates and other microorganisms. Nevertheless, if adequate statistical procedures are selected, association networks can be powerful tools to formulate testable hypotheses about the autecology of only recently described ciliate species.

  6. Effect of Phytoplankton Richness on Phytoplankton Biomass Is Weak Where the Distribution of Herbivores is Patchy.

    Science.gov (United States)

    Weis, Jerome J

    2016-01-01

    Positive effects of competitor species richness on competitor productivity can be more pronounced at a scale that includes heterogeneity in 'bottom-up' environmental factors, such as the supply of limiting nutrients. The effect of species richness is not well understood in landscapes where variation in 'top-down' factors, such as the abundance of predators or herbivores, has a strong influence competitor communities. I asked how phytoplankton species richness directly influenced standing phytoplankton biomass in replicate microcosm regions where one patch had a population of herbivores (Daphnia pulicaria) and one patch did not have herbivores. The effect of phytoplankton richness on standing phytoplankton biomass was positive but weak and not statistically significant at this regional scale. Among no-Daphnia patches, there was a significant positive effect of phytoplankton richness that resulted from positive selection effects for two dominant and productive species in polycultures. Among with-Daphnia patches there was not a significant effect of phytoplankton richness. The same two species dominated species-rich polycultures in no- and with-Daphnia patches but both species were relatively vulnerable to consumption by Daphnia. Consistent with previous studies, this experiment shows a measurable positive influence of primary producer richness on biomass when herbivores were absent. It also shows that given the patchy distribution of herbivores at a regional scale, a regional positive effect was not detected.

  7. Nutrients, phytoplankton, zooplankton, and macrobenthos

    Science.gov (United States)

    Rudstam, Lars G.; Holeck, Kristen T.; Watkins, James M.; Hotaling, Christopher; Lantry, Jana R.; Bowen, Kelly L.; Munawar, Mohi; Weidel, Brian C.; Barbiero, Richard; Luckey, Frederick J.; Dove, Alice; Johnson, Timothy B.; Biesinger, Zy

    2017-01-01

    Lower trophic levels support the prey fish on which most sport fish depend. Therefore, understanding the production potential of lower trophic levels is integral to the management of Lake Ontario’s fishery resources. Lower trophic-level productivity differs among offshore and nearshore waters. In the offshore, there is concern about the ability of the lake to support Alewife (Table 1) production due to a perceived decline in productivity of phytoplankton and zooplankton whereas, in the nearshore, there is a concern about excessive attached algal production (e.g., Cladophora) associated with higher nutrient concentrations—the oligotrophication of the offshore and the eutrophication of the nearshore (Mills et al. 2003; Holeck et al. 2008; Dove 2009; Koops et al. 2015; Stewart et al. 2016). Even though the collapse of the Alewife population in Lake Huron in 2003 (and the associated decline in the Chinook Salmon fishery) may have been precipitated by a cold winter (Dunlop and Riley 2013), Alewife had not returned to high abundances in Lake Huron as of 2014 (Roseman et al. 2015). Failure of the Alewife population to recover from collapse has been attributed to declines in lower trophic-level production (Barbiero et al. 2011; Bunnell et al. 2014; but see He et al. 2015). In Lake Michigan, concerns of a similar Alewife collapse led to a decrease in the number of Chinook Salmon stocked. If lower trophic-level production declines in Lake Ontario, a similar management action could be considered. On the other hand, in Lake Erie, which supplies most of the water in Lake Ontario, eutrophication is increasing and so are harmful algal blooms. Thus, there is also a concern that nutrient levels and algal blooms could increase in Lake Ontario, especially in the nearshore. Solutions to the two processes of concern—eutrophication in the nearshore and oligotrophication in the offshore—may be mutually exclusive. In either circumstance, fisheries management needs information on

  8. Links between phytoplankton dynamics and shell growth of Arctica islandica on the Faroe Shelf

    Science.gov (United States)

    Bonitz, Fabian Georg Wulf; Andersson, Carin; Trofimova, Tamara; Hátún, Hjálmar

    2018-03-01

    The phytoplankton dynamics on the Faroe Shelf are strongly connected to higher trophic levels, and their inter-annual variability has great importance for many organisms, including the principal fish stocks. Hence, information on the marked phytoplankton variability is scientifically and economically valuable. We show here that the shell growth variability in Arctica islandica shells has the potential to identify periods of increased and decreased phytoplankton concentrations on the Faroe Shelf and in the wider Faroese region in previous centuries. The growth of A. islandica has often been linked to changes in phytoplankton concentrations, i.e., food availability. By cross-matching life-collected and sub-fossil A. islandica shells from two separate locations on the Faroe Shelf, we have built a master chronology, which reaches back to the 17th century. This master chronology correlates well with a Primary Production index for the Faroe Shelf (r = 0.65; p phytoplankton concentrations over the wider Faroese Channel Region, as represented in the Continuous Plankton Recorder surveys, especially for the months June-September (r = 0.39; p < 0.01). In addition, an inverse relationship is observed between the master chronology and on-shelf water temperatures from June-September (r = - 0.29; p < 0.01), which is likely associated with a previously reported inverse relationship between temperatures and the on-shelf primary production. An analysis of the δ18O in the shells shows that the main growing season of the shells presumably occurs during the spring and summer months, which concurs with the main spring bloom.

  9. An Inverse Modeling Approach to Estimating Phytoplankton Pigment Concentrations from Phytoplankton Absorption Spectra

    Science.gov (United States)

    Moisan, John R.; Moisan, Tiffany A. H.; Linkswiler, Matthew A.

    2011-01-01

    Phytoplankton absorption spectra and High-Performance Liquid Chromatography (HPLC) pigment observations from the Eastern U.S. and global observations from NASA's SeaBASS archive are used in a linear inverse calculation to extract pigment-specific absorption spectra. Using these pigment-specific absorption spectra to reconstruct the phytoplankton absorption spectra results in high correlations at all visible wavelengths (r(sup 2) from 0.83 to 0.98), and linear regressions (slopes ranging from 0.8 to 1.1). Higher correlations (r(sup 2) from 0.75 to 1.00) are obtained in the visible portion of the spectra when the total phytoplankton absorption spectra are unpackaged by multiplying the entire spectra by a factor that sets the total absorption at 675 nm to that expected from absorption spectra reconstruction using measured pigment concentrations and laboratory-derived pigment-specific absorption spectra. The derived pigment-specific absorption spectra were further used with the total phytoplankton absorption spectra in a second linear inverse calculation to estimate the various phytoplankton HPLC pigments. A comparison between the estimated and measured pigment concentrations for the 18 pigment fields showed good correlations (r(sup 2) greater than 0.5) for 7 pigments and very good correlations (r(sup 2) greater than 0.7) for chlorophyll a and fucoxanthin. Higher correlations result when the analysis is carried out at more local geographic scales. The ability to estimate phytoplankton pigments using pigment-specific absorption spectra is critical for using hyperspectral inverse models to retrieve phytoplankton pigment concentrations and other Inherent Optical Properties (IOPs) from passive remote sensing observations.

  10. Light Absorption by Suspended Particles in the Red Sea: Effect of Phytoplankton Community Size Structure and Pigment Composition

    Science.gov (United States)

    Kheireddine, Malika; Ouhssain, Mustapha; Organelli, Emanuele; Bricaud, Annick; Jones, Burton H.

    2018-02-01

    The light absorption properties of phytoplankton (aph(λ)) and nonalgal particles (anap(λ)) associated with phytoplankton pigments were analyzed across the Red Sea, in the upper 200 m depth, between October 2014 and August 2016. The contribution by nonalgal particles to the total particulate light absorption (aph(λ) + anap(λ)) was highly variable (23 ± 17% at 440 nm) and no relationship between anap(440) and chlorophyll a concentration, [TChl a], was observed. Phytoplankton-specific phytoplankton absorption coefficients at 440 and 676 nm for a given [TChl a], aph*(440), and aph∗(676) were slightly higher than those derived from average relationships for open ocean waters within the surface layer as well as along the water column. Variations in the concentration of photosynthetic and photoprotective pigments were noticeable by changes in phytoplankton community size structure as well as in aph∗(λ). This study revealed that a higher proportion of picophytoplankton and an increase in photoprotective pigments (mainly driven by zeaxanthin) tended to be responsible for the higher aph∗(λ) values found in the Red Sea as compared to other oligotrophic regions with similar [TChl a]. Understanding this variability across the Red Sea may help improve the accuracy of biogeochemical parameters, such as [TChl a], derived from in situ measurements and ocean color remote sensing at a regional scale.

  11. Light Absorption by Suspended Particles in the Red Sea: Effect of Phytoplankton Community Size Structure and Pigment Composition

    KAUST Repository

    Kheireddine, Malika

    2018-01-10

    The light absorption properties of phytoplankton (aph(λ)) and non-algal particles (anap(λ)) associated with phytoplankton pigments were analyzed across the Red Sea, in the upper 200 m depth, between October 2014 and August 2016. The contribution by non-algal particles to the total particulate light absorption (aph(λ)+ anap(λ)) was highly variable (23 ± 17% at 440 nm) and no relationship between anap(440) and chlorophyll a concentration, [TChl a], was observed. Phytoplankton specific phytoplankton absorption coefficients at 440 and 676 nm for a given [TChl a], aph*(440) and aph*(676), were slightly higher than those derived from average relationships for open ocean waters within the surface layer as well as along the water column. Variations in the concentration of photosynthetic and photoprotective pigments were noticeable by changes in phytoplankton community size structure as well as in aph*(λ). This study revealed that a higher proportion of picophytoplankton and an increase in photoprotective pigments (mainly driven by zeaxanthin) tended to be responsible for the higher aph*(λ) values found in the Red Sea as compared to other oligotrophic regions with similar [TChl a]. Understanding this variability across the Red Sea may help improve the accuracy of biogeochemical parameters, such as [TChl a], derived from in situ measurements and ocean color remote sensing at a regional scale.

  12. Light Absorption by Suspended Particles in the Red Sea: Effect of Phytoplankton Community Size Structure and Pigment Composition

    KAUST Repository

    Kheireddine, Malika; Ouhssain, Mustapha; Organelli, Emanuele; Bricaud, Annick; Jones, Burton

    2018-01-01

    The light absorption properties of phytoplankton (aph(λ)) and non-algal particles (anap(λ)) associated with phytoplankton pigments were analyzed across the Red Sea, in the upper 200 m depth, between October 2014 and August 2016. The contribution by non-algal particles to the total particulate light absorption (aph(λ)+ anap(λ)) was highly variable (23 ± 17% at 440 nm) and no relationship between anap(440) and chlorophyll a concentration, [TChl a], was observed. Phytoplankton specific phytoplankton absorption coefficients at 440 and 676 nm for a given [TChl a], aph*(440) and aph*(676), were slightly higher than those derived from average relationships for open ocean waters within the surface layer as well as along the water column. Variations in the concentration of photosynthetic and photoprotective pigments were noticeable by changes in phytoplankton community size structure as well as in aph*(λ). This study revealed that a higher proportion of picophytoplankton and an increase in photoprotective pigments (mainly driven by zeaxanthin) tended to be responsible for the higher aph*(λ) values found in the Red Sea as compared to other oligotrophic regions with similar [TChl a]. Understanding this variability across the Red Sea may help improve the accuracy of biogeochemical parameters, such as [TChl a], derived from in situ measurements and ocean color remote sensing at a regional scale.

  13. Measurement of phytoplankton photosynthesis rate using a pump-and-probe fluorometer

    Directory of Open Access Journals (Sweden)

    Taras K. Antal

    2001-09-01

    Full Text Available In this work we have studied the possibility of determining the rate of phytoplankton photosynthesis in situ using a submersible pump-and-probe fluorometer in water areas differing in their trophic level, as well as in climatic and hydrophysical characteristics. A biophysical model was used to describe the relationship between photosynthesis, underwater irradiance, and the intensity of phytoplankton fluorescence excited by an artificial light source. Fluorescence intensity was used as a measure of light absorption by phytoplankton and for assessing the efficiency of photochemical energy conversion at photosynthetic reaction centers. Parameters of the model that could not be measured experimentally were determined by calibrating fluorescence and irradiance data against the primary production measured in the Baltic Sea with the radioactive carbon method. It was shown that the standard deviation of these parameters in situ did not exceed 20%, and the use of their mean values to estimate the phytoplankton photosynthetic rate showed a good correlation between the calculated and meas

  14. Contrasting Photophysiological Characteristics of Phytoplankton Assemblages in the Northern South China Sea.

    Science.gov (United States)

    Jin, Peng; Gao, Guang; Liu, Xin; Li, Futian; Tong, Shanying; Ding, Jiancheng; Zhong, Zhihai; Liu, Nana; Gao, Kunshan

    2016-01-01

    The growth of phytoplankton and thus marine primary productivity depend on photophysiological performance of phytoplankton cells that respond to changing environmental conditions. The South China Sea (SCS) is the largest marginal sea of the western Pacific and plays important roles in modulating regional climate and carbon budget. However, little has been documented on photophysiological characteristics of phytoplankton in the SCS. For the first time, we investigated photophysiological characteristics of phytoplankton assemblages in the northern South China Sea (NSCS) using a real-time in-situ active chlorophyll a fluorometry, covering 4.0 × 105 km2. The functional absorption cross section of photosystem II (PSII) in darkness (σPSII) or under ambient light (σPSII') (A2 quanta-1) increased from the surface to deeper waters at all the stations during the survey period (29 July to 23 August 2012). While the maximum (Fv/Fm, measured in darkness) or effective (Fq'/Fm', measured under ambient light) photochemical efficiency of PSII appeared to increase with increasing depth at most stations, it showed inverse relationship with depth in river plume areas. The functional absorption cross section of PSII changes could be attributed to light-adapted genotypic feature due to niche-partition and the alteration of photochemical efficiency of PSII could be attributed to photo-acclimation. The chlorophyll a fluorometry can be taken as an analog to estimate primary productivity, since areas of higher photochemical efficiency of PSII coincided with those of higher primary productivity reported previously in the NSCS.

  15. Constraining the variability of optical properties in the Santa Barbara Channel, CA: A phytoplankton story

    Science.gov (United States)

    Barron, Rebecca Katherine

    The research presented in this dissertation evaluates the direct relationships of phytoplankton community composition and inherent optical properties (IOP); that is, the absorption and scattering of light in the ocean. Phytoplankton community composition affect IOPs in both direct and indirect ways, thus creating challenges for optical measurements of biological and biogeochemical properties in aquatic systems. Studies were performed in the Santa Barbara Channel (SBC), CA where an array of optical and biogeochemical measurements were made. Phytoplankton community structure was characterized by an empirical orthogonal functional analysis (EOF) using phytoplankton accessory pigments. The results showed that phytoplankton community significantly correlated to all IOPs, e.g. phytoplankton specific absorption, detrital absorption, CDOM absorption and particle backscattering coefficients. Furthermore, the EOF analysis was unique in splitting the microphytoplankton size class into separate diatom and dinoflagellate regimes allowing for assessment optical property differences within the same size class, a technique previously not systematically achievable. The phytoplankton functional group dinoflagellates were particularly influential to IOPs in surprising ways. Dinoflagellates showed higher backscattering efficiencies than would be predicted based on Mie theory, and significantly influenced CDOM absorption via direct association with dissolved mycosproine-like amino acid absorption (MAA) peaks in CDOM spectra. A new index was developed in this work to quantify MAA absorption peaks in CDOM spectra, and was named the MAA Index. Prior to this research dissolved MAA absorption in natural waters was never quantified, and CDOM data containing these peaks were often disregarded and discarded from analysis. CDOM dynamics in the SBC were assessed for a 15-year study period, and this work shows that significantly large MAA Index values, e.g. MAA Index > 1, were present in

  16. Southern Ocean Phytoplankton in a Changing Climate

    OpenAIRE

    Deppeler, Stacy L.; Davidson, Andrew T.

    2017-01-01

    Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced sal...

  17. Review of time-dose effects in radiation therapy

    International Nuclear Information System (INIS)

    Peschel, R.E.; Fischer, J.J.

    1980-01-01

    A historical review of conventional fractionation offers little confidence that such treatment is optimal for all tumors. Thus manipulation of time-dose schedules may provide a relatively inexpensive yet potentially useful technique for improving therapeutic results in radiation therapy. Consideration of basic radiobiological principles and animal model data illustrates the complex and heterogeneous nature of normal tissue and tumor response to time-dose effects and supports the hypothesis that better time-dose prescriptions can be found in clinical practice. The number of possible time-dose prescriptions is very large, and a review of the clinical trials using nonconventional fractionation demonstrates that the sampled portion of the total three-dimensional space of time, fraction number, and dose has been very small. Only carefully designed clinical trials can establish the therapeutic advantage of a new treatment schedule, and methods for selecting the most promising schedules are discussed. The use of simple data reduction formulas for time-dose effects should be discarded since they ignore the very complexity and heterogeneity of tissues and tumors which may form the basis of improved clinical results

  18. Spontaneous Assembly of Exopolymers from Phytoplankton

    Directory of Open Access Journals (Sweden)

    Yong-Xue Ding

    2009-01-01

    Full Text Available Phytoplankton exopolymeric substances (EPS contribute significantly to the dissolved organic car bon (DOC pool in the ocean, playing crucial roles in the surface ocean car bon cycle. Recent studies have demonstrated that ~10% of marine DOC can self-assemble as microgels through electro static Ca bonds providing hotspots of enriched microbial substrate. How ever, the question whether EPS can self-assemble and the formation mechanisms for EPS microgels have not been examined. Here were port that EPS from three representative phytoplankton species, Synechococcus, Emiliania huxleyi, and Skeletonema costatum can spontaneously self assemble in artificial sea water (ASW, forming microscopic gels of ~ 3 - 4 __m in diameter. Different from the marine DOC polymers assembly, these EPS samples can self-assemble in Ca2+-free ASW. Further experiments from fluorescence enhancement and chemical composition analysis confirmed the existence of fair amounts of hydrophobic domains in these EPS samples. These results suggest that hydrophobic interactions play a key role in the assembly of EPS from these three species of marine phytoplankton.

  19. Bioaccumulation of technetium by marine phytoplankton

    International Nuclear Information System (INIS)

    Fisher, N.S.

    1982-01-01

    /sup 95m/Tc, in the IV and VII oxidation states, was added in picomolar quantities to monocultures of seven species of marine phytoplankton, including a green algae (Dunaliella tertiolecta), a diatom (Thalassiosira pseudonana), a blue-green alga (Oscillatoria woronichinii), a prasinophyte (Testraselmis chuii), two haptophytes (Emiliania huxleyi and Cricosphaera carterae), and a dinoflagellate (Heterocapsa pygmaea). Cultures were incubated for 4 days, and uptake of Tc was periodically determined by ν spectroscopy of filtered and unfiltered samples. All the Tc remained in the water column in all flasks, but none of the species appreciably concentrated the element in either oxidation state. Mean uptake (measured as the fraction retained on filters) for all species was 0.029% for Tc(IV) and 0.023% for Tc(VII), neither of which was significantly different from the uninoculated control cultures. Wet weight concentration factors never exceeded 20 for any species, 3 orders of magnitude lower than previously reported for phytoplankton and Tc. The results indicate that phytoplankton are likely to have negligble influence on the cycling of Tc in marine systems

  20. Phytoplankton composition of Sazlidere Dam lake, Istanbul, Turkey

    Directory of Open Access Journals (Sweden)

    Nese Yilmaz

    2013-05-01

    Full Text Available The phytoplankton composition of Sazlidere Dam lake was studied at 5 sampling sites between December 2003 - November 2005. A total of 67 taxa were recorded, representing Bacillariophyta (31, Chlorophyta (18, Cyanophyta (9, Chrysophyta (1, Cryptophyta (1, Dinophyta (3 and Euglenophyta (4. Bacillariophyta members constituted the dominant phytoplankton group in terms of species number. Nygaard’s compound index value and composition of phytoplankton indicate that the trophic state of Sazlidere Dam lake was changing from oligotrophic to mesotrophic.

  1. Phytoplankton global mapping from space with a support vector machine algorithm

    Science.gov (United States)

    de Boissieu, Florian; Menkes, Christophe; Dupouy, Cécile; Rodier, Martin; Bonnet, Sophie; Mangeas, Morgan; Frouin, Robert J.

    2014-11-01

    In recent years great progress has been made in global mapping of phytoplankton from space. Two main trends have emerged, the recognition of phytoplankton functional types (PFT) based on reflectance normalized to chlorophyll-a concentration, and the recognition of phytoplankton size class (PSC) based on the relationship between cell size and chlorophyll-a concentration. However, PFTs and PSCs are not decorrelated, and one approach can complement the other in a recognition task. In this paper, we explore the recognition of several dominant PFTs by combining reflectance anomalies, chlorophyll-a concentration and other environmental parameters, such as sea surface temperature and wind speed. Remote sensing pixels are labeled thanks to coincident in-situ pigment data from GeP&CO, NOMAD and MAREDAT datasets, covering various oceanographic environments. The recognition is made with a supervised Support Vector Machine classifier trained on the labeled pixels. This algorithm enables a non-linear separation of the classes in the input space and is especially adapted for small training datasets as available here. Moreover, it provides a class probability estimate, allowing one to enhance the robustness of the classification results through the choice of a minimum probability threshold. A greedy feature selection associated to a 10-fold cross-validation procedure is applied to select the most discriminative input features and evaluate the classification performance. The best classifiers are finally applied on daily remote sensing datasets (SeaWIFS, MODISA) and the resulting dominant PFT maps are compared with other studies. Several conclusions are drawn: (1) the feature selection highlights the weight of temperature, chlorophyll-a and wind speed variables in phytoplankton recognition; (2) the classifiers show good results and dominant PFT maps in agreement with phytoplankton distribution knowledge; (3) classification on MODISA data seems to perform better than on SeaWIFS data

  2. Retention time generates short-term phytoplankton blooms in a shallow microtidal subtropical estuary

    Science.gov (United States)

    Odebrecht, Clarisse; Abreu, Paulo C.; Carstensen, Jacob

    2015-09-01

    In this study it was hypothesised that increasing water retention time promotes phytoplankton blooms in the shallow microtidal Patos Lagoon estuary (PLE). This hypothesis was tested using salinity variation as a proxy of water retention time and chlorophyll a for phytoplankton biomass. Submersible sensors fixed at 5 m depth near the mouth of PLE continuously measured water temperature, salinity and pigments fluorescence (calibrated to chlorophyll a) between March 2010 and 12th of December 2011, with some gaps. Salinity variations were used to separate alternating patterns of outflow of lagoon water (salinity 24; 35% of the time). The two transition phases represented a rapid change from lagoon water outflow to marine water inflow and a more gradually declining salinity between the dominating inflow and outflow conditions. During the latter of these, a significant chlorophyll a increase relative to that expected from a linear mixing relationship was observed at intermediate salinities (10-20). The increase in chlorophyll a was positively related to the duration of the prior coastal water inflow in the PLE. Moreover, chlorophyll a increase was significantly higher during austral spring-summer than autumn-winter, probably due to higher light and nutrient availability in the former. Moreover, the retention time process operating on time scales of days influences the long-term phytoplankton variability in this ecosystem. Comparing these results with monthly data from a nearby long-term water quality monitoring station (1993-2011) support the hypothesis that chlorophyll a accumulations occur after marine inflow events, whereas phytoplankton does not accumulate during high water outflow, when the water residence time is short. These results suggest that changing hydrological pattern is the most important mechanism underlying phytoplankton blooms in the PLE.

  3. Effects of cadmium accumulation from suspended sediments and phytoplankton on the Oyster Saccostrea glomerata

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Helena A.; Maher, William A., E-mail: bill.maher@canberra.edu.au; Taylor, Anne M.; Krikowa, Frank

    2015-03-15

    Highlights: • Saccostrea glomerata accumulated cadmium from sediments and phytoplankton. • Effects were similar for both pathways. • Antioxidant capacity, lipid peroxidation and lysosomal destabilisation were affected. • Clear exposure–dose–response relationships were demonstrated. - Abstract: Metals are accumulated by filter feeding organisms via water, ingestion of suspended sediments or food. The uptake pathway can affect metal toxicity. Saccostrea glomerata were exposed to cadmium through cadmium-spiked suspended sediments (19 and 93 μg/g dry mass) and cadmium-enriched phytoplankton (1.6–3 μg/g dry mass) and cadmium uptake and effects measured. Oysters accumulated appreciable amounts of cadmium from both low and high cadmium spiked suspended sediment treatments (5.9 ± 0.4 μg/g and 23 ± 2 μg/g respectively compared to controls 0.97 ± 0.05 μg/g dry mass). Only a small amount of cadmium was accumulated by ingestion of cadmium-enriched phytoplankton (1.9 ± 0.1 μg/g compared to controls 1.2 ± 0.1 μg/g). In the cadmium spiked suspended sediment experiments, most cadmium was desorbed from sediments and cadmium concentrations in S. glomerata were significantly related to dissolved cadmium concentrations (4–21 μg/L) in the overlying water. In the phytoplankton feeding experiment cadmium concentrations in overlying water were <0.01 μg/L. In both exposure experiments, cadmium-exposed oysters showed a significant reduction in total antioxidant capacity and significantly increased lipid peroxidation and percentage of destabilised lysosomes. Destabilised lysosomes in the suspended sediments experiments also resulted from stress of exposure to the suspended sediments. The study demonstrated that exposure to cadmium via suspended sediments and to low concentrations of cadmium through the ingestion of phytoplankton, can cause sublethal stress to S. glomerata.

  4. Linking phytoplankton community size composition with temperature, plankton food web structure and sea–air CO2 flux

    DEFF Research Database (Denmark)

    Hilligsøe, Karen Marie; Richardson, Katherine; Bendtsen, Jørgen

    2011-01-01

    Data collected at open water stations (depth>400m) in all major ocean basins in 2006–2008 are used to examine the relationship between the size structure of the phytoplankton community (determined by size fractionated chlorophyll filtration), temperature and inorganic nutrient availability...

  5. Phytoplankton chlorophyll a biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

    NARCIS (Netherlands)

    van de Poll, W.H.; Kulk, G.; Timmermans, K.R.; Brussaard, C.P.D.; van der Woerd, H.J.; Kehoe, M.J.; Mojica, K.D.A.; Visser, R.J.W.; Rozema, P.D.; Buma, A.G.J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63° N in the northeast Atlantic

  6. Phytoplankton chlorophyll a biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

    NARCIS (Netherlands)

    van de Poll, W. H.; Kulk, G.; Timmermans, K. R.; Brussaard, C. P. D.; van der Woerd, H. J.; Kehoe, M. J.; Mojica, K. D. A.; Visser, R. J. W.; Rozema, P. D.; Buma, A. G. J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 degrees N in the northeast

  7. Parameter constraints of grazing response functions. Implications for phytoplankton bloom initiation

    Directory of Open Access Journals (Sweden)

    Jordi Solé

    2016-09-01

    Full Text Available Phytoplankton blooms are events of production and accumulation of phytoplankton biomass that influence ecosystem dynamics and may also have effects on socio-economic activities. Among the biological factors that affect bloom dynamics, prey selection by zooplankton may play an important role. Here we consider the initial state of development of an algal bloom and analyse how a reduced grazing pressure can allow an algal species with a lower intrinsic growth rate than a competitor to become dominant. We use a simple model with two microalgal species and one zooplankton grazer to derive general relationships between phytoplankton growth and zooplankton grazing. These relationships are applied to two common grazing response functions in order to deduce the mathematical constraints that the parameters of these functions must obey to allow the dominance of the lower growth rate competitor. To assess the usefulness of the deduced relationships in a more general framework, the results are applied in the context of a multispecies ecosystem model (ERSEM.

  8. Negative effects of UVB-irradiated phytoplankton on life history traits and fitness of Daphnia magna

    NARCIS (Netherlands)

    Lange, de H.J.; Reeuwijk, van P.L.

    2003-01-01

    1. We tested the effect of ultraviolet-B (UVB)-irradiated phytoplankton on life history characteristics of Daphnia magna . Two phytoplankton species were used, Chlamydomonas reinhardtii and Cryptomonas pyrenoidifera . The phytoplankton species were cultured under photosynthetically active radiation

  9. The dose effect of irradiated rice pollen on double fertilization

    International Nuclear Information System (INIS)

    Wang Houcong; Chen Zhengming; Chen Ruming; Qiu Simi; Yang Juemin; Yang Huijie

    1995-01-01

    The mature panicles of rice were treated with 60 Co γ-rays in the range of 0∼0.372 kGy. The male sterile line used as the female plants were fertilized with γ-irradiated pollen manually. The dose effect of the irradiated pollen on double fertilization was investigated. It was found that double fertilization of the irradiated pollen was suppressed to different degrees as compared with the control. The effect was noticeable as that the fusion time of the male nucleolus with the female one was delayed with the increasing of γ-radiation dose. The delayed time was less than 13 hours when the dose was below 0.186 kGy and it was more than 15 hours when the dose was above 0.279 kGy. Furthermore, several types of deformed embryonic cells and endosperm nuclei were observed

  10. Relating coccolithophore calcification rates to phytoplankton community dynamics: Regional differences and implications for carbon export

    Science.gov (United States)

    Poulton, Alex J.; Adey, Tim R.; Balch, William M.; Holligan, Patrick M.

    2007-03-01

    Recent measurements of surface coccolithophore calcification from the Atlantic Ocean (50°N-50°S) are compared to similar measurements from other oceanic settings. By combining the different data sets of surface measurements, we examine general and regional patterns of calcification relative to organic carbon production (photosynthesis) and other characteristics of the phytoplankton community. Generally, surface calcification and photosynthesis are positively correlated, although the strength of the relationship differs between biogeochemical provinces. Relationships between surface calcification, chlorophyll- a and calcite concentrations are also statistically significant, although again there is considerable regional variability. Such variability appears unrelated to phytoplankton community composition or hydrographic conditions, and may instead reflect variations in coccolithophore physiology. The contribution of inorganic carbon fixation (calcification) to total carbon fixation (calcification plus photosynthesis) is ˜1-10%, and we estimate a similar contribution from coccolithophores to total organic carbon fixation. However, these contributions vary between biogeochemical provinces, and occasionally coccolithophores may account for >20% of total carbon fixation in unproductive central subtropical gyres. Combining surface calcification and photosynthetic rates with standing stocks of calcite, particulate organic carbon, and estimated phytoplankton carbon allows us to examine the fates of these three carbon pools. The relative turnover times vary between different biogeochemical provinces, with no clear relationship to the overall productivity or phytoplankton community structure found in each province. Rather, interaction between coccolithophore physiology (coccolith production and detachment rates), species diversity (cell size), and food web dynamics (grazer ecology) may control the composition and turnover times of calcite particles in the upper ocean.

  11. Why large cells dominate estuarine phytoplankton

    Science.gov (United States)

    Cloern, James E.

    2018-01-01

    Surveys across the world oceans have shown that phytoplankton biomass and production are dominated by small cells (picoplankton) where nutrient concentrations are low, but large cells (microplankton) dominate when nutrient-rich deep water is mixed to the surface. I analyzed phytoplankton size structure in samples collected over 25 yr in San Francisco Bay, a nutrient-rich estuary. Biomass was dominated by large cells because their biomass selectively grew during blooms. Large-cell dominance appears to be a characteristic of ecosystems at the land–sea interface, and these places may therefore function as analogs to oceanic upwelling systems. Simulations with a size-structured NPZ model showed that runs of positive net growth rate persisted long enough for biomass of large, but not small, cells to accumulate. Model experiments showed that small cells would dominate in the absence of grazing, at lower nutrient concentrations, and at elevated (+5°C) temperatures. Underlying these results are two fundamental scaling laws: (1) large cells are grazed more slowly than small cells, and (2) grazing rate increases with temperature faster than growth rate. The model experiments suggest testable hypotheses about phytoplankton size structure at the land–sea interface: (1) anthropogenic nutrient enrichment increases cell size; (2) this response varies with temperature and only occurs at mid-high latitudes; (3) large-cell blooms can only develop when temperature is below a critical value, around 15°C; (4) cell size diminishes along temperature gradients from high to low latitudes; and (5) large-cell blooms will diminish or disappear where planetary warming increases temperature beyond their critical threshold.

  12. Dose-effect curves for electron-beam irradiation of some collection microbial strains

    International Nuclear Information System (INIS)

    Ferdes, O.; Dumitru, E.; Catargiu, L.; Ferdes, M.; Minea, R.; Oproiu, C.; Niculescu, A.

    1994-01-01

    There were electron-beam irradiated some microbial strains of B.subtilis ICA I-60 both in germination and in sporulated forms. The irradiation were performed at the IPTRD's electron accelerator at 6 MeV, and in the dose range between 0.1-5.0 kGy, at different dose-rate varying from 50 Gy/minute to 100 Gy/minute. The dosimetry was carried out by a PTW medical dosemeter. There were established the dose-effect relationships and curves, the inactivation dose (factor) and the optimum domain for electron-beam mutagenesis. There were obtained some mutant strains with 2-3.5 higher biosynthesis potential, which are in the IFC's collection. (Author)

  13. Ecological niches of open ocean phytoplankton taxa

    DEFF Research Database (Denmark)

    Brun, Philipp Georg; Vogt, Meike; Payne, Mark

    2015-01-01

    We characterize the realized ecological niches of 133 phytoplankton taxa in the open ocean based on observations from the MAREDAT initiative and a statistical species distribution model (MaxEnt). The models find that the physical conditions (mixed layer depth, temperature, light) govern large...... conditions in the open ocean. Our estimates of the realized niches roughly match the predictions of Reynolds' C-S-R model for the global ocean, namely that taxa classified as nutrient stress tolerant have niches at lower nutrient and higher irradiance conditions than light stress tolerant taxa. Yet...

  14. Seasonal Distribution of Phytoplankton in Riwada Reservoir, Visakhapatnam, Andhra Pradesh, India

    Directory of Open Access Journals (Sweden)

    Jyothi KAPARAPU

    2013-08-01

    Full Text Available The present study deals with seasonal variations, correlation coefficient and biodiversity indices of phytoplankton during April 2011 to March 2012 in the Riwada reservoir, Visakhapatnam, Andhra Pradesh, India. Sampling was performed at five stations during pre-monsoon, monsoon and post monsoon. There were a total of 57 genera belonging to four major groups i.e., Chlorophyceae (27 genera, Bacillariophyceae (14 genera, Cyanophyceae (13 genera and Euglenophyceae (three genera. Maximum and minimum total phytoplankton population and percentages were recorded at station three in pre monsoon and at station two during monsoon. The maximum and minimum species richness (Menhinick index R2 were found to be 1.29 at station one and 1.10 at station three respectively. Maximum and minimum species diversity (H1 were found at station four (3.98 and station two (3.71. Maximum species evenness was recorded at stations one, being four and five; minimum species evenness was recorded at station two. Correlation coefficient matrix indicated significant positive relationship with water temperature, pH, transparency, biological oxygen demand and chlorides, negative relationship with electric conductivity, total solids, total dissolved solids, total hardness, dissolved oxygen, nitrates, sulphates and phosphates of water. The diversity indices showed that the reservoir have a well balanced phytoplankton community.

  15. Pigment specific in vivo light absorption of phytoplankton from estuarine, coastal and oceanic waters

    DEFF Research Database (Denmark)

    Stæhr, A.; Markager, S.; Sand-Jensen, K.

    2004-01-01

    The influence of phytoplankton photoacclimation and adaptation to natural growth conditions on the chlorophyll a-specific in vivo absorption coefficient (a* ph) was evaluated for samples collected in estuarine, coastal and oceanic waters. Despite an overall gradient in the physio......-chemical environment from estuaries, over coastal, to oceanic waters, no clear relationships were found between a* ph and the prevailing light, temperature, salinity and nutrient concentrations, indicating that short-term cellular acclimation was of minor importance for the observed variability in a* ph. The clear...... decline in a* ph from oceanic, over coastal, to estuarine waters was, however, strongly correlated with an increase in cell size and intracellular chlorophyll a (chl a) content of the phytoplankton, and a reduction of photosynthetic carotenoids relative to chl a. Variations in photoprotective carotenoids...

  16. Population dynamics of light-limited phytoplankton : Microcosm experiments

    NARCIS (Netherlands)

    Huisman, Jef

    This paper investigates the extent to which the predictions of an elementary model for light-limited growth are matched by laboratory experiments with light-limited phytoplankton. The model and experiments link the population dynamics of phytoplankton species with changes in the light gradient

  17. Phytoplankton/protozoan dynamics in the Nyara Estuary, a small ...

    African Journals Online (AJOL)

    Phytoplankton/protozoan dynamics in the Nyara Estuary, a small temporarily open system in the Eastern Cape (South Africa) ... freshwater inflow, the Nyara is best described as a predominantly low nutrient, low phytoplankton biomass, stratified system, dominated by the microbial food-web and possibly fed by detritus.

  18. Steady state of phytoplankton assemblage in tropical Lake Catemaco (Mexico)

    Czech Academy of Sciences Publication Activity Database

    Komárková, Jaroslava; Tavera, R.

    2003-01-01

    Roč. 502, - (2003), s. 187-196 ISSN 0018-8158. [Workshop of the International Association of Phytoplankton Taxonomy and Acology /13./. Castelbuono, 00.09.2002] R&D Projects: GA AV ČR KSK6005114 Keywords : lake Catemaco * phytoplankton * food web Subject RIV: EF - Botanics Impact factor: 0.720, year: 2003

  19. Water quality status and phytoplankton composition in Soetendalvlei ...

    African Journals Online (AJOL)

    Three wetlands on the Agulhas Plain, for which no limnological information was available, were investigated in order to provide baseline data on their present water quality and phytoplankton community structure. Physicochemical variables were assessed and phytoplankton biomass and community analyses were ...

  20. Spatial and temporal patterns of phytoplankton abundance and ...

    African Journals Online (AJOL)

    Bacillariophyta was the most abundant group (48.17% of total phytoplankton) and was uniformly distributed in all waters, followed by Cyanobacteria (33.33%), which decreased with distance offshore. Chlorophyta, the third highest in abundance (15.5%), increased with distance offshore. A total of 92 phytoplankton species ...

  1. Phytoplankton production and adaptation in the vicinity of Pemba ...

    African Journals Online (AJOL)

    Phytoplankton production and physiology were investigated at six selected locations during a research cruise in early October 2007 in Tanzanian coastal waters. The dataset included photosynthesis–irradiance and active fluorescence parameters, phytoplankton absorption coefficients, and pigment concentrations. Primary ...

  2. Phytoplankton responses to aluminum enrichment in the South China Sea.

    Science.gov (United States)

    Zhou, Linbin; Liu, Jiaxing; Xing, Shuai; Tan, Yehui; Huang, Liangmin

    2018-04-01

    Compared to extensive studies reporting the aluminum (Al) toxicity to terrestrial plants and freshwater organisms, very little is known about how marine phytoplankton responds to Al in the field. Here we report the marine phytoplankton responses to Al enrichment in the South China Sea (SCS) using on-deck bottle incubation experiments during eight cruises from May 2010 to November 2013. Generally, Al addition alone enhanced the growth of diatom and Trichodesmium, and nitrogen fixation, but it inhibited the growth of dinoflagellates and Synechococcus. Nevertheless, Al addition alone did not influence the chlorophyll a concentration of the entire phytoplankton assemblages. By adding nitrate and phosphate simultaneously, Al enrichment led to substantial increases in chlorophyll a concentration (especially that of the picophytoplanktonenrichment. Further, by simultaneously adding different macronutrients and/or sufficient trace metals including iron, we found that the phytoplankton responses to Al enrichment were relevant to nutrients coexisting in the environment. Al enrichment may give some phytoplankton a competitive edge over using nutrients, especially the limited ones. The possible influences of Al on the competitors and grazers (predators) of some phytoplankton might indirectly contribute to the positive responses of the phytoplankton to Al enrichment. Our results indicate that Al may influence marine carbon cycle by impacting phytoplankton growth and structure in natural seawater. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Initial growth of phytoplankton in turbid estuaries: a simple model

    NARCIS (Netherlands)

    de Swart, H.E.; Schuttelaars, H.; Talke, S.A.

    2009-01-01

    An idealised model is presented and analysed to gain more fundamental understanding about the dynamics of phytoplankton blooms in well-mixed, suspended sediment dominated estuaries. The model describes the behaviour of subtidal currents, suspended sediments, nutrients and phytoplankton in a channel

  4. Nutrients and toxin producing phytoplankton control algal blooms

    Indian Academy of Sciences (India)

    A phytoplankton-zooplankton prey-predator model has been investigated for temporal, spatial and spatio-temporal dissipative pattern formation in a deterministic and noisy environment, respectively. The overall carrying capacity for the phytoplankton population depends on the nutrient level. The role of nutrient ...

  5. Distribution of phytoplankton and chlorophyll a around little Andaman Island

    Digital Repository Service at National Institute of Oceanography (India)

    Devassy, V.P; Bhattathiri, P

    0.014 to 0.064(av.0.029). Depthwise distribution of phytoplankton chl a and phaeo-pigments showed an increasing trend up to 1% light in the 2 coral banks. Phytoplankton population ranged from 1400 to 4900 cells/litre. Dinoflagellates formed...

  6. Does biodiversity of estuarine phytoplankton depend on hydrology?

    NARCIS (Netherlands)

    Ferreira, JG; Wolff, WJ; Simas, TC; Bricker, SB

    2005-01-01

    Phytoplankton growth in estuaries is controlled by factors such as flushing, salinity tolerance, light, nutrients and grazing. Here, we show that biodiversity of estuarine phytoplankton is related to flushing, and illustrate this for some European estuaries. The implications for the definition of

  7. Growth of Phytoplankton in Different Fertilizer Media | KADIRI ...

    African Journals Online (AJOL)

    ... medium and there was no significant difference between Scenedesmus and Oscillatoria sp. whereas in the inorganic fertilizer, there was no significant difference between the growth response from all phytoplankton. All experiments lasted 14 days. Key words: Aquaculture, Phytoplankton Production, Biofertilizer, Inorganic

  8. Distributions of phytoplankton in a coastal lagoon of Mahin, Ondo ...

    African Journals Online (AJOL)

    Distributions of phytoplankton were investigated in Mahin Lagoon within Transgressive mud coast of Ondo, Western Nigeria. Collections and analyses of samples of phytoplankton and surface waters (for some physico-chemical parameters) were done at fifteen stations along the stretch of the lagoon in October 2013 and ...

  9. A prospective study of marine phytoplankton and reported ...

    Science.gov (United States)

    BACKGROUND: Blooms of marine phytoplankton may adversely affect human health. The potential public health impact of low-level exposures is not well established, and few prospective cohort studies of recreational exposures to marine phytoplankton have been conducted.OBJECTIVE: We evaluated the association between phytoplankton cell counts and subsequent illness among recreational beachgoers.METHODS:We recruited beachgoers at Boquer6n Beach, Puerto Rico, during the summer of 2009. We conducted interviews at three time points to assess baseline health, water activities, and subsequent illness. Daily water samples were quantitatively assayed for phytoplankton cell count. Logistic regression models, adjusted for age and sex, were used to assess the association between exposure to three categories of phytoplankton concentration and subsequent illness.RESULTS: During 26 study days, 15,726 individuals successfully completed all three interviews. Daily total phytoplankton cell counts ranged from 346 to 2,012 cells/ml (median, 712 cells/ml). The category with the highest (≥75th percentile) total phytoplankton cell count was associated with eye irritation [adjusted odds ratio (OR) = 1.30; 95% confidence interval (Cl): 1.01, 1.66], rash (OR = 1.27; 95% Cl: 1.02, 1.57), and earache (OR = 1.25; 95% Cl: 0.88, 1.77). In phytoplankton group-specific analyses, the category with the highest Cyanobacteria counts was associated with respiratory illness (OR = 1.37; 95% Cl: 1.12, 1

  10. Community structure characteristics of phytoplankton in zhalong wetland, china

    International Nuclear Information System (INIS)

    Zhang, N.; Zang, S.S.

    2015-01-01

    In autumn 2010, the phytoplankton samples were collected in Zhalong Wetland. A total of 347 species belonging to 78 genera,6 phyla were identified, Chlorophyta and Bacillariophyta were dominated phytoplankton communities, including 143 species of Chlorophyta, 116 species of Bacillariophyta, 45 species of Cyanophyta, 39 species of Euglenophyta, 3 species of Pyrrophyta, 1 species of Chrysophyta. In the core area 66 genera, 222 species were identified, in the buffer area 63 genera, 210 species were identified, in the experiment area 63 genera, 167 species were identified. The dominant species in Zhalong Wetland included Cyclotella meneghiniana, Chlorella vulgaris, Trachelomonas volvocina, Nitzschia sp.. The average phytoplankton density was 12.13*10/sup 6/ in Zhalong Wetland, the phytoplankton density of Bacillariophyta was highest (32.82*10/sup 6/ ind L/sup -1/), and then Chlorophyta (23.73*10/sup 6/ ind L/sup -1/) and Cyanophyta (11.43*106 ind L-1), respectively. The results of cluster analysis showed that phytoplankton community structure could be divided into three types, and within-group similarities of phytoplankton community structure was not high, but inter-group non-similarity was high. Based on the species composition, phytoplankton density, phytoplankton pollution indicator, it suggested that Zhalong Wetland was mesotrophic state. (author)

  11. Monitoring and prediction of phytoplankton dynamics in the North Sea

    NARCIS (Netherlands)

    Blauw, A.N.

    2015-01-01

    Phytoplankton forms the base of the marine food web, but when concentrations get too high, algal blooms can have adverse effects on ecosystems and aquaculture. Phytoplankton concentrations vary strongly in space and time. However, the nature and drivers of this variability are not yet well

  12. Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

    Directory of Open Access Journals (Sweden)

    M. J. Behrenfeld

    2009-05-01

    Full Text Available Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we evaluate the physiological underpinnings of global variations in satellite-based phytoplankton chlorophyll fluorescence. The three dominant factors influencing fluorescence distributions are chlorophyll concentration, pigment packaging effects on light absorption, and light-dependent energy-quenching processes. After accounting for these three factors, resultant global distributions of quenching-corrected fluorescence quantum yields reveal a striking consistency with anticipated patterns of iron availability. High fluorescence quantum yields are typically found in low iron waters, while low quantum yields dominate regions where other environmental factors are most limiting to phytoplankton growth. Specific properties of photosynthetic membranes are discussed that provide a mechanistic view linking iron stress to satellite-detected fluorescence. Our results present satellite-based fluorescence as a valuable tool for evaluating nutrient stress predictions in ocean ecosystem models and give the first synoptic observational evidence that iron plays an important role in seasonal phytoplankton dynamics of the Indian Ocean. Satellite fluorescence may also provide a path for monitoring climate-phytoplankton physiology interactions and improving descriptions of phytoplankton light use efficiencies in ocean productivity models.

  13. Phytoplankton diversity and abundance in Ndop wetland plain ...

    African Journals Online (AJOL)

    DR FONGE B

    African Journal of Environmental Science and Technology Vol. 6(6), pp. ... In the Philippines, around 67% of the mangrove has been lost over the last 60 years or so, ... Phytoplankton is an important primary producer, since ... area of 1,152 km2 and a population of about 160,000 inhabitants. It ... Phytoplankton assessment.

  14. Response of phytoplankton assemblages isolated for short periods ...

    African Journals Online (AJOL)

    The response of phytoplankton assemblages isolated in enclosures for short periods of time was examined in hyper-eutrophic Lake Chivero (Harare, Zimbabwe), to determine the factors that influenced the structure of the phytoplankton community, after noticing a marked decline in the dominance of Microcystis aeruginosa ...

  15. Function assessment of coastal ecosystem based on phytoplankton community structure

    DEFF Research Database (Denmark)

    Haraguchi, Lumi

    2018-01-01

    on phytoplankton community structure; and 3) investigating the role of planktonic communities on the cycling of dissolved organic matter. Those objectives were addressed focusing the temperate mesohaline estuary of Roskilde Fjord (Denmark). Paper I, explores the use of Pulse-shape recording flow cytometry (PFCM...... as an energy reservoir, buffering changes in the nutrient supply. Finally, the results embedded in this thesis demonstrate the importance of integrating different time scales to understand functioning of phytoplankton communities. Phytoplankton dynamics should not be regarded just in light of inorganic......This Ph.D. project aimed to improve the knowledge on phytoplankton community structure and its influence in the carbon transfer and nutrient cycling in coastal waters, by: 1) assessing the importance of phytoplankton

  16. Margalef's mandala and phytoplankton bloom strategies

    Science.gov (United States)

    Wyatt, Timothy

    2014-03-01

    Margalef's mandala maps phytoplankton species into a phase space defined by turbulence (A) and nutrient concentrations (Ni); these are the hard axes. The permutations of high and low A and high and low Ni divide the space into four domains. Soft axes indicate some ecological dynamics. A main sequence shows the normal course of phytoplankton succession; the r-K axis of MacArthur and Wilson runs parallel to it. An alternative successional sequence leads to the low A-high Ni domain into which many red tide species are mapped. Astronomical and biological time are implicit. A mathematical transformation of the mandala (rotation) links it to the classical bloom models of Sverdrup (time) and Kierstead and Slobodkin (space). Both rarity and the propensity to form red tides are considered to be species characters, meaning that maximum population abundance can be a target of natural selection. Equally, both the unpredictable appearance of bloom species and their short-lived appearances may be species characters. There may be a correlation too between these features and long-lived dormant stages in the life-cycle; then the vegetative planktonic phase is the 'weak link' in the life-cycle. Red tides are thus due to species which have evolved suites of traits which result in specific demographic strategies.

  17. Title: Freshwater phytoplankton responses to global warming.

    Science.gov (United States)

    Wagner, Heiko; Fanesi, Andrea; Wilhelm, Christian

    2016-09-20

    Global warming alters species composition and function of freshwater ecosystems. However, the impact of temperature on primary productivity is not sufficiently understood and water quality models need to be improved in order to assess the quantitative and qualitative changes of aquatic communities. On the basis of experimental data, we demonstrate that the commonly used photosynthetic and water chemistry parameters alone are not sufficient for modeling phytoplankton growth under changing temperature regimes. We present some new aspects of the acclimation process with respect to temperature and how contrasting responses may be explained by a more complete physiological knowledge of the energy flow from photons to new biomass. We further suggest including additional bio-markers/traits for algal growth such as carbon allocation patterns to increase the explanatory power of such models. Although carbon allocation patterns are promising and functional cellular traits for growth prediction under different nutrient and light conditions, their predictive power still waits to be tested with respect to temperature. A great challenge for the near future will be the prediction of primary production efficiencies under the global change scenario using a uniform model for phytoplankton assemblages. Copyright © 2016 Elsevier GmbH. All rights reserved.

  18. Toxic phytoplankton in San Francisco Bay

    Science.gov (United States)

    Rodgers, Kristine M.; Garrison, David L.; Cloern, James E.

    1996-01-01

    The Regional Monitoring Program (RMP) was conceived and designed to document the changing distribution and effects of trace substances in San Francisco Bay, with focus on toxic contaminants that have become enriched by human inputs. However, coastal ecosystems like San Francisco Bay also have potential sources of naturally-produced toxic substances that can disrupt food webs and, under extreme circumstances, become threats to public health. The most prevalent source of natural toxins is from blooms of algal species that can synthesize metabolites that are toxic to invertebrates or vertebrates. Although San Francisco Bay is nutrient-rich, it has so far apparently been immune from the epidemic of harmful algal blooms in the world’s nutrient-enriched coastal waters. This absence of acute harmful blooms does not imply that San Francisco Bay has unique features that preclude toxic blooms. No sampling program has been implemented to document the occurrence of toxin-producing algae in San Francisco Bay, so it is difficult to judge the likelihood of such events in the future. This issue is directly relevant to the goals of RMP because harmful species of phytoplankton have the potential to disrupt ecosystem processes that support animal populations, cause severe illness or death in humans, and confound the outcomes of toxicity bioassays such as those included in the RMP. Our purpose here is to utilize existing data on the phytoplankton community of San Francisco Bay to provide a provisional statement about the occurrence, distribution, and potential threats of harmful algae in this Estuary.

  19. Normal tissue dose-effect models in biological dose optimisation

    International Nuclear Information System (INIS)

    Alber, M.

    2008-01-01

    Sophisticated radiotherapy techniques like intensity modulated radiotherapy with photons and protons rely on numerical dose optimisation. The evaluation of normal tissue dose distributions that deviate significantly from the common clinical routine and also the mathematical expression of desirable properties of a dose distribution is difficult. In essence, a dose evaluation model for normal tissues has to express the tissue specific volume effect. A formalism of local dose effect measures is presented, which can be applied to serial and parallel responding tissues as well as target volumes and physical dose penalties. These models allow a transparent description of the volume effect and an efficient control over the optimum dose distribution. They can be linked to normal tissue complication probability models and the equivalent uniform dose concept. In clinical applications, they provide a means to standardize normal tissue doses in the face of inevitable anatomical differences between patients and a vastly increased freedom to shape the dose, without being overly limiting like sets of dose-volume constraints. (orig.)

  20. Phytoplankton and the Macondo oil spill: A comparison of the 2010 phytoplankton assemblage to baseline conditions on the Louisiana shelf.

    Science.gov (United States)

    Parsons, M L; Morrison, W; Rabalais, N N; Turner, R E; Tyre, K N

    2015-12-01

    The Macondo oil spill was likely the largest oil spill to ever occur in United States territorial waters. We report herein our findings comparing the available baseline phytoplankton data from coastal waters west of the Mississippi River, and samples collected monthly from the same sampling stations, during and after the oil spill (May-October, 2010). Our results indicate that overall, the phytoplankton abundance was 85% lower in 2010 versus the baseline, and that the species composition of the phytoplankton community moved towards diatoms and cyanobacteria and away from ciliates and phytoflagellates. The results of this study reaffirm the view that phytoplankton responses will vary by the seasonal timing of the oil spill and the specific composition of the spilled oil. The trophic impacts of the purported lower abundance of phytoplankton in 2010 coupled with the observed assemblage shift remain unknown. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Diversity of phytoplankton in some domestic wastewater-fed urban fish pond ecosystems of the Chota Nagpur Plateau in Bankura, India

    Science.gov (United States)

    Das, Debjyoti; Pathak, Arabinda; Pal, Sudin

    2018-06-01

    The present limnological investigation is conducted to study the relationship between phytoplankton abundance and five important physicochemical factors in urban wastewater-fed seven fish ponds of Chota Nagpur Plateau area. A total number of 43 phytoplankton taxa representing four classes, namely Cyanophyceae (7), Chlorophyceae (29), Bacillariophyceae (5) and Euglenophyceae (2), are thriving in these ponds which may suggest that different nutrient-rich wastewater supports the diversity and abundance of the phytoplankton. Different values of diversity indices, results of post hoc analysis and rarefaction curve are depicted spatial variations of phytoplankton abundance and physicochemical factors. From the Principal Component Analysis, out of 43 phytoplankton species, 23 important species are extracted. The canonical correspondence analysis presents that most of the phytoplankton species densities are associated with higher values of the physicochemical variables in these ponds. Correspondingly, in the present study, Algal Genus Pollution Index (AGPI) is employed to study the water quality of seven sites. From the AGPI score, it is revealed that Site 4 has probable high organic pollution and Site 2 and Site 3 have moderate organic pollution. Therefore, long-term intensive studies and proper management are necessary to protect these ponds toward eutrophication and degradation, because these ponds not only act as a safeguard of livelihoods but also contribute significantly at local level food and water security and economic prosperity.

  2. Phytoplankton assemblage of a small, shallow, tropical African reservoir.

    Science.gov (United States)

    Mustapha, Moshood K

    2009-12-01

    I measured physico-chemical properties and phytoplankton in the small, shallow tropical reservoir of Oyun (Offa, Nigeria) between January 2002 and December 2003. I identified 25 phytoplankton genera in three sampling stations. Bacillariophyceae dominated (75.3%), followed by Chlorophyceae (12.2%), Cyanobacteria (11.1%) and Desmidiaceae (0.73%). The high amount of nutrients (e.g. nitrate, phosphate, sulphate and silica) explain phytoplankton heterogeneity (p<0.05). Phytoplankton was abundant during the rainy season, but the transition period had the richest assemblage and abundance. Fluctuations in phytoplankton density were a result of seasonal changes in concentration of nutrients, grazing pressure and reservoir hydrology. The reservoir is eutrophic with excellent water quality and a diverse phytoplankton assemblage: fish production would be high. These conditions resulted from strategies such as watershed best management practices (BMPs) to control eutrophication and sedimentation, and priorities for water usage established through legislation. Additional measures are recommended to prevent oligotrophy, hypereutrophy, excessive phytoplankton bloom, toxic cyanobacteria, and run-off of organic waste and salts.

  3. Pigment signatures of phytoplankton communities in the Beaufort Sea

    Science.gov (United States)

    Coupel, P.; Matsuoka, A.; Ruiz-Pino, D.; Gosselin, M.; Marie, D.; Tremblay, J.-É.; Babin, M.

    2015-02-01

    Phytoplankton are expected to respond to recent environmental changes of the Arctic Ocean. In terms of bottom-up control, modifying the phytoplankton distribution will ultimately affect the entire food web and carbon export. However, detecting and quantifying changes in phytoplankton communities in the Arctic Ocean remains difficult because of the lack of data and the inconsistent identification methods used. Based on pigment and microscopy data sampled in the Beaufort Sea during summer 2009, we optimized the chemotaxonomic tool CHEMTAX (CHEMical TAXonomy) for the assessment of phytoplankton community composition in an Arctic setting. The geographical distribution of the main phytoplankton groups was determined with clustering methods. Four phytoplankton assemblages were determined and related to bathymetry, nutrients and light availability. Surface waters across the whole survey region were dominated by prasinophytes and chlorophytes, whereas the subsurface chlorophyll maximum was dominated by the centric diatoms Chaetoceros socialis on the shelf and by two populations of nanoflagellates in the deep basin. Microscopic counts showed a high contribution of the heterotrophic dinoflagellates Gymnodinium and Gyrodinium spp. to total carbon biomass, suggesting high grazing activity at this time of the year. However, CHEMTAX was unable to detect these dinoflagellates because they lack peridinin. In heterotrophic dinoflagellates, the inclusion of the pigments of their prey potentially leads to incorrect group assignments and some misinterpretation of CHEMTAX. Thanks to the high reproducibility of pigment analysis, our results can serve as a baseline to assess change and spatial or temporal variability in several phytoplankton populations that are not affected by these misinterpretations.

  4. Phytoplankton chytridiomycosis: fungal parasites of phytoplankton and their imprints on the food web dynamics

    Directory of Open Access Journals (Sweden)

    Télesphore eSIME - NGANDO

    2012-10-01

    Full Text Available Parasitism is one of the earlier and common ecological interactions in the nature, occurring in almost all environments. Microbial parasites typically are characterized by their small size, short generation time, and high rates of reproduction, with simple life cycle occurring generally within a single host. They are diverse and ubiquitous in aquatic ecosystems, comprising viruses, prokaryotes and eukaryotes. Recently, environmental 18S-rDNA surveys of microbial eukaryotes have unveiled major infecting agents in pelagic systems, consisting primarily of the fungal order of Chytridiales (chytrids. Chytrids are considered the earlier branch of the Eumycetes and produce motile, flagellated zoospores, characterized by a small size (2-6 µm and a single, posterior flagellum. The existence of these dispersal propagules includes chytrids within the so-called group of zoosporic fungi, which are particularly adapted to the plankton lifestyle where they infect a wide variety of hosts, including fishes, eggs, zooplankton, algae, and other aquatic fungi but primarily freshwater phytoplankton. Related ecological implications are huge because chytrids can killed their hosts, release substrates for microbial processes, and provide nutrient-rich particles as zoospores and short fragments of filamentous inedible hosts for the grazer food chain. Furthermore, based on the observation that phytoplankton chytridiomycosis preferentially impacts the larger size species, blooms of such species (e.g. filamentous cyanobacteria may not totally represent trophic bottlenecks. Besides, chytrid epidemics represent an important driving factor in phytoplankton seasonal successions. In this review, I summarize the knowledge on the diversity, community structure, quantitative importance, and functional roles of fungal chytrids, primarily those who are parasites of phytoplankton, and infer the ecological implications and potentials for the food web dynamics and properties.

  5. Factors driving the spatiotemporal variability in phytoplankton in the Northern South China Sea

    Science.gov (United States)

    Wei, Na; Satheeswaran, Thangaraj; Jenkinson, Ian R.; Xue, Bing; Wei, Yuqiu; Liu, Haijiao; Sun, Jun

    2018-06-01

    The influence of oceanographic processes on phytoplankton diversity and community structure was examined during a cruise conducted from July to August 2012 in the northern South China Sea (nSCS). One hundred ninety seven seawater samples were collected and analyzed from 41 stations in the nSCS. A total of 215 species were identified belonging to 67 genera, mostly dominated by diatoms (67.36%) followed by dinoflagellates (28.16%). The mean cell abundance of diatoms and dinoflagellates were 1.954 × 103 cells L-1 and 0.817 × 103 cells L-1, respectively. Diatoms mainly distributed in coastal region whereas dianoflaglletes in the open sea. Margalaf's species richness (dMa) was maximum (3.96) at SQD1 station (Depth 15 m), whereas it was minimum (0.07) at SS1 (Depth 200 m). Further, Box-Whisker plot displayed that dissolved inorganic nutrients incresed with depth. Nevertheless, redundacy analysis reveled that phytoplankton density has a negative relationship with nutrients. Overall the presesant study provides latest in-depth information about how the factors influencing the phytoplankton density and diversity in the (nSCS) during summer based on the cruise data which could serve as a reference for the similar study.

  6. Effects of acidity on primary productivity in lakes: phytoplankton. [Lakes Panther, Sagamore, and Woods

    Energy Technology Data Exchange (ETDEWEB)

    Hendrey, G R

    1979-01-01

    Relationships between phytoplankton communities and lake acidity are being studied at Woods Lake (pH ca. 4.9), Sagamore Lake (pH ca. 5.5), and Panther Lake (pH ca. 7.0). Numbers of phytoplankton species observed as of July 31, 1979 are Woods 27, Sagamore 38, and Panther 64, conforming to other observations that species numbers decrease with increasing acidity. Patterns of increasing biomass and productivity found in Woods Lake may be atypical of similar oligotrophic lakes in that they develop rather slowly instead of occuring very close to ice-out. Contributions of netplankton (net > 48 ..mu..m), nannoplankton (48 > nanno > 20 ..mu..m) and ultraplankton (20 > ultra >0.45 ..mu..m) to productivity per m/sup -2/ show that the smaller plankton are relatively more important in the more acid lakes. This pattern could be determined by nutrient availability (lake acidification leading to decreased availability of phosphorus). The amount of /sup 14/C-labelled dissolved photosynthate (/sup 14/C-DOM), as a percent of total productivity, is ordered Woods > Sagamore > Panther. This is consistent with a hypothesis that microbial heterotrophic activity is reduced with increasing acidity, but the smaller phytoplankton may be more leaky at low pH. (ERB)

  7. The Importance of Phytoplankton Biomolecule Availability for Secondary Production

    Directory of Open Access Journals (Sweden)

    Elina T. Peltomaa

    2017-10-01

    Full Text Available The growth and reproduction of animals is affected by their access to resources. In aquatic ecosystems, the availability of essential biomolecules for filter-feeding zooplankton depends greatly on phytoplankton. Here, we analyzed the biochemical composition, i.e., the fatty acid, sterol and amino acid profiles and concentrations as well as protein, carbon, nitrogen, and phosphorus content of 17 phytoplankton monocultures representing the seven most abundant phytoplankton classes in boreal and sub-arctic lakes. To examine how the differences in the biochemical composition between phytoplankton classes affect their nutritional quality for consumers, we assessed the performance of Daphnia, on these diets. Furthermore, we defined the most important biomolecules regulating the somatic growth and reproduction of Daphnia, expecting that higher concentrations of certain biomolecules are needed for reproduction than for growth. Finally, we combined these results with phytoplankton field data from over 900 boreal and sub-arctic lakes in order to estimate whether the somatic growth of Daphnia is sterol-limited when the natural phytoplankton communities are cyanobacteria-dominated. Our analysis shows that Daphnia grows best with phytoplankton rich in sterols, ω-3 fatty acids, protein, and amino acids. Their reproduction follows food sterol and ω-3 concentration as well as C:P-ratio being two times higher in Daphnia feeding on cryptophytes than any other diet. Interestingly, we found that a high dietary ω-6 fatty acid concentration decreases both somatic growth and reproduction of Daphnia. When combined with phytoplankton community composition field data, our results indicate that zooplankton is constantly limited by sterols in lakes dominated by cyanobacteria (≥40% of total phytoplankton biomass, and that the absence of cryptophytes can severely hinder zooplankton production in nature.

  8. Dynamics of phytoplankton blooms in turbulent vortex cells

    DEFF Research Database (Denmark)

    Lindemann, Christian; Visser, Andre; Mariani, Patrizio

    2017-01-01

    the effects of turbulent transport on the phytoplankton population growth and its spatial structure in a vertical two-dimensional vortex flow field. In particular, we focus on how turbulent flow velocities and sinking influence phytoplankton growth and biomass aggregation. Our results indicate that conditions...... can be maintained with increasing turbulent flow velocities, allowing the apparently counter-intuitive persistence of fast sinking phytoplankton populations in highly turbulent and deep mixed layers. These dynamics demonstrate the role of considering advective transport within a turbulent vortex...

  9. Interactions of phytoplankton, zooplankton and microorganisms

    Science.gov (United States)

    Pomeroy, L. R.; Paffenhöfer, G.-A.; Yoder, J. A.

    We present evidence that there are significant interactions between heterotrophic microorganisms, doliolids and Fritillaria within intrusions of nutrient-rich Gulf Stream water stranding on the continental shelf. During the summer of 1981 cold, nutrient-rich water from below the surface of the Gulf Stream was repeatedly intruded and stranded on the continental shelf off northeastern Florida. On August 6 old, stranded Gulf Stream water depleted of nitrate occupied the lower layer on the outer shelf. The upper water was continental shelf water, older but of undefined age. On August 6 free-living bacteria were >10 6ml -1 everywhere at all depths, an order of magnitude greater than normal bacterial numbers on the northeastern Florida continental shelf. Over 10 days the numbers of free bacteria doubled while bacteria attached to particles increased by a factor of four. The adenylate/chlorophyll ratio showed that phytoplankton dominated the lower layers of intruded water, while the surface water became increasingly dominated by heterotrophic microorganisms (bacteria and protozoa) over 10 days. There were significant, negative correlations between bacteria and doliolids and between bacteria and Fritillaria. Regions of maximum bacterial numbers did not coincide with locations of salp swarms. The increased numbers of bacteria at all depths in a highly stratified system in which most phytoplankton are in the lower layer suggests a diverse source of bacterial growth substrates, some of which involve zooplankton as intermediaries. Production of autotrophs is more than twice that of microheterotrophs on average, but because of their differential distribution, microheterotrophs are the dominant biomass in much of the surface water and may be significant in energy flux to metazoan consumers as well as competitors for mutually useable sources of nutrition.

  10. Absorption of ultraviolet radiation by antarctic phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Vernet, M.; Mitchell, B.G. (Univ. of California-San Diego, La Jolla (United States))

    1990-01-09

    Antarctic phytoplankton contain UV-absorbing compounds that may block damaging radiation. Compounds that absorb from 320-340 nm were observed in spectral absorption of both particulates and in methanol extracts of the particulates. The decrease in the total concentration of these UV compounds with respect to chlorophyll a, as measured by the ratio of in vitro absorption at 335 nm to absorption at 665 nm is variable and decreases with depth. We observed up to 5-fold decrease in this ratio for samples within the physically mixes surface layer. The absorption of UV radiation in methanol extracts, which peaks from 320 to 340 nm, may be composed of several compounds. Shifts in peak absorption with depth (for example, from 331 nm at surface to 321 nm at 75 m), may be interpreted as a change in composition. Ratios of protective yellow xanthophylls (diadinoxanthin + diatoxanthin) to photosynthetic fucoxanthin-like pigments have highest values in surface waters. As these pigments also absorb in the near UV, their function might extend to protection as well as utilization of UV radiation for photosynthesis. We document strong absorption in the UV from 320-330 nm for Antarctic marine particulates. Below this region of the solar energy spectrum, absolute energy levels of incident radiation drop off dramatically. Only wavelengths shorter than about 320 nm will be significantly enhanced due to ozone depletion. If the absorption we observed serves a protective role for phytoplankton photosynthesis, it appears the peak band is in the region where solar energy increases rapidly, and not in the region where depletion would cause significant variations in absolute flux.

  11. The influence of environmental variables on spatial and temporal phytoplankton dissimilarity in a large shallow subtropical lake (Lake Mangueira, southern Brazil

    Directory of Open Access Journals (Sweden)

    Luciane Oliveira Crossetti

    2014-06-01

    Full Text Available AIM: The uneven distribution of organisms in aquatic ecosystems is generally attributed to environmental heterogeneity in both space and time, reflecting the occurrence of appropriate environmental conditions and the availability of resources to biological communities. The aim of this study was to understand how the dissimilarity of the phytoplankton community in a large subtropical shallow lake is related to environmental dissimilarities. METHODS: Biotic and environmental data were gathered at 19 sites along the 90-km length of Lake Mangueira. Sampling was carried out quarterly during 2010 and 2011, totaling 152 sampling units. The relationship between phytoplankton dissimilarity and the dissimilarity of environmental variables was assessed by the BioEnv analysis. MAJOR RESULTS: There is a significant relationship between phytoplankton dissimilarity and environmental dissimilarity. The model that best explained the dissimilarity of phytoplankton among the sampling units included pH, turbidity and nitrate. CONCLUSIONS: The dissimilarity of phytoplankton was related to the dissimilarity, which were directly associated to the variability of conditions and resources in space and time in Lake Mangueira.

  12. Phytoplankton community as bioindicator of fertility in belawan river

    Science.gov (United States)

    Sari Yeanny, Mayang

    2018-03-01

    Belawan River is an important river for the Medan residents and its surroundings. It serves as the main raw material for the local drinking water company, as well as domestic, industrial, hotel and tourism. Many human activities had led to the declining condition of water in the river throughout the year. One way to approach the concept of bioindicator is by knowing Abundance, Relative Abundance, Frequency of Attendance, equitability, dominance, and diversity of the phytoplankton itself. Results indicated that the phytoplankton community was from 3 different classes: Chlorophyceae, Bacillariophyceae, and Cyanophyceae. Phytoplankton individual abundance was around 2612 to 17755 ind / L. The diversity index was around 2.15 to 2.58, which is considered to have low to moderate diversity with high pollution level. Equitability Index was approaching 0, with relatively high domination from Sphaeroplea and Asterionella. The water quality that influences the diversity of phytoplankton as bioindicator was dissolved oxygen.

  13. Phytoplankton dynamics and periodicity in two cascading warm ...

    African Journals Online (AJOL)

    1991-09-04

    Sep 4, 1991 ... warm-water reservoirs from 1989 to 1997 – taxonomic and ... Consideration of phytoplankton dynamics in terms of functional groups offers certain advantages over conventional ... (drinking water) in South Africa (DWA 1986).

  14. Ecology of phytoplankton from Dharmatar Creek, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Tiwari, L.R.; Nair, V.R.

    Phytoplankton pigment, cell count and species diversity wee studied at five locations in Dharamtar Creek during September 1984 to November 1985. Chemical parameters indicated a healthy system free of any environmental stress. The water...

  15. Sedimentation of phytoplankton during a diatom bloom : Rates and mechanisms

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, J.L.S.; Alldredge, A.L.

    1996-01-01

    Phytoplankton blooms are uncoupled from grazing and are normally terminated by sedimentation. There are several potential mechanisms by which phytoplankton cells may settle out of the photic zone: sinking of individual cells or chains, coagulation of cells into aggregates with high settling...... velocities, settling of cells attached to marine snow aggregates formed from discarded larvacean houses or pteropod feeding webs, and packaging of cells into rapidly falling zooplankton fecal pellets. We quantified the relative significance of these different mechanisms during a diatom bloom in a temperate...... to marine snow aggregates formed from discarded larvacean houses, whereas settling of unaggregated cells was insignificant. Formation rates of phytoplankton aggregates by physical coagulation was very low, and losses by this mechanism were much less than 0.07 d(-1); phytoplankton aggregates were neither...

  16. Phytoplankton models and life history strategies | Eilertsen | African ...

    African Journals Online (AJOL)

    Phytoplankton models and life history strategies. ... Chaetoceros bloom of the growth season usually starts in mid March, initiated by C. socialis. ... in some species, inoculation events are controlled by endogenous biological clocks.

  17. Phytoplankton Diversity in the Cross River Estuary of Nigeria ...

    African Journals Online (AJOL)

    DR. MIKE HORSFALL

    This study was carried out to provide a concise set of structural based .... further growth of diatom in this zone due to rapid uptake of ... Table 1: Taxonomic listing and spatial distribution of phytoplankton species in Cross Rivers estuary. (+ =.

  18. PHYTOPLANKTON - WET WEIGHT and Other Data (NODC Accession 9400037)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Profiles of Chlorophyll data from NASA Goddard and Phytoplankton wet weight data in this accession was submitted by Mr. Charles R. McClain of US National...

  19. Variations in the spectral values of specific absorption of phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Sathyendranath, S.; Lazzara, L.; Prieur, L.

    Absorption spectra of laboratory cultures of eight species of phytoplankton were studied. These spectra, normalized per unit of chlorophyll a concentration (specific absorption) show variability in magnitude and spectral form. Specific absorption...

  20. Early Spring Phytoplankton Dynamics in the Western Antarctic Peninsula

    Science.gov (United States)

    Arrigo, Kevin R.; van Dijken, Gert L.; Alderkamp, Anne-Carlijn; Erickson, Zachary K.; Lewis, Kate M.; Lowry, Kate E.; Joy-Warren, Hannah L.; Middag, Rob; Nash-Arrigo, Janice E.; Selz, Virginia; van de Poll, Willem

    2017-12-01

    The Palmer Long-Term Ecological Research program has sampled waters of the western Antarctic Peninsula (wAP) annually each summer since 1990. However, information about the wAP prior to the peak of the phytoplankton bloom in January is sparse. Here we present results from a spring process cruise that sampled the wAP in the early stages of phytoplankton bloom development in 2014. Sea ice concentrations were high on the shelf relative to nonshelf waters, especially toward the south. Macronutrients were high and nonlimiting to phytoplankton growth in both shelf and nonshelf waters, while dissolved iron concentrations were high only on the shelf. Phytoplankton were in good physiological condition throughout the wAP, although biomass on the shelf was uniformly low, presumably because of heavy sea ice cover. In contrast, an early stage phytoplankton bloom was observed beneath variable sea ice cover just seaward of the shelf break. Chlorophyll a concentrations in the bloom reached 2 mg m-3 within a 100-150 km band between the SBACC and SACCF. The location of the bloom appeared to be controlled by a balance between enhanced vertical mixing at the position of the two fronts and increased stratification due to melting sea ice between them. Unlike summer, when diatoms overwhelmingly dominate the phytoplankton population of the wAP, the haptophyte Phaeocystis antarctica dominated in spring, although diatoms were common. These results suggest that factors controlling phytoplankton abundance and composition change seasonally and may differentially affect phytoplankton populations as environmental conditions within the wAP region continue to change.

  1. Phytoplankton dynamic responses to oil spill in Mumbai Harbour

    Digital Repository Service at National Institute of Oceanography (India)

    JiyalalRam, M.J.; Ram, A.; Rokade, M.A.; Karangutkar, S.H.; Yengal, B.; Dalvi, S.; Acharya, D.; Sharma, S.; Gajbhiye, S.N.

    have shown that the high concen- tration of oil reduces the phytoplankton growth but when oil becomes in low concentration it, stimulates the growth of microalgae [29-31]. Aksmann and Tukaj [32], believed that the reac- tive oxygen free radicals... in phytoplankton cells increased under the stress of oil pollution and such increment of reactive oxygen free radicals promoted the content of superoxide dismutase in cells at low concentrations of oil, which enhanced the defensive reaction of algae cells...

  2. Latitudinal variation of phytoplankton communities in the western Arctic Ocean

    Science.gov (United States)

    Min Joo, Hyoung; Lee, Sang H.; Won Jung, Seung; Dahms, Hans-Uwe; Hwan Lee, Jin

    2012-12-01

    Recent studies have shown that photosynthetic eukaryotes are an active and often dominant component of Arctic phytoplankton assemblages. In order to explore this notion at a large scale, samples were collected to investigate the community structure and biovolume of phytoplankton along a transect in the western Arctic Ocean. The transect included 37 stations at the surface and subsurface chlorophyll a maximum (SCM) depths in the Bering Sea, Chukchi Sea, and Canadian Basin from July 19 to September 5, 2008. Phytoplankton (>2 μm) were identified and counted. A cluster analysis of abundance and biovolume data revealed different assemblages over the shelf, slope, and basin regions. Phytoplankton communities were composed of 71 taxa representing Dinophyceae, Cryptophyceae, Bacillariophyceae, Chrysophyceae, Dictyochophyceae, Prasinophyceae, and Prymnesiophyceae. The most abundant species were of pico- to nano-size at the surface and SCM depths at most stations. Nano- and pico-sized phytoplankton appeared to be dominant in the Bering Sea, whereas diatoms and nano-sized plankton provided the majority of taxon diversity in the Bering Strait and in the Chukchi Sea. From the western Bering Sea to the Bering Strait, the abundance, biovolume, and species diversity of phytoplankton provided a marked latitudinal gradient towards the central Arctic. Although pico- and nano-sized phytoplankton contributed most to cell abundance, their chlorophyll a contents and biovolumes were less than those of the larger micro-sized taxa. Micro-sized phytoplankton contributed most to the biovolume in the largely ice-free waters of the western Arctic Ocean during summer 2008.

  3. Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

    KAUST Repository

    Coello-Camba, A.; Llabré s, M.; Duarte, Carlos M.; Agusti, Susana

    2017-01-01

    Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

  4. Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

    KAUST Repository

    Coello-Camba, A.

    2017-04-24

    Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

  5. Amplified Arctic warming by phytoplankton under greenhouse warming.

    Science.gov (United States)

    Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

    2015-05-12

    Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.

  6. Climate Variability and Phytoplankton in the Pacific Ocean

    Science.gov (United States)

    Rousseaux, Cecile

    2012-01-01

    The effect of climate variability on phytoplankton communities was assessed for the tropical and sub-tropical Pacific Ocean between 1998 and 2005 using an established biogeochemical assimilation model. The phytoplankton communities exhibited wide range of responses to climate variability, from radical shifts in the Equatorial Pacific, to changes of only a couple of phytoplankton groups in the North Central Pacific, to no significant changes in the South Pacific. In the Equatorial Pacific, climate variability dominated the variability of phytoplankton. Here, nitrate, chlorophyll and all but one of the 4 phytoplankton types (diatoms, cyanobacteria and coccolithophores) were strongly correlated (pphytoplankton groups (chlorophytes and coccolithophores). Ocean biology in the South Pacific was not significantly correlated with MEI. During La Nina events, diatoms increased and expanded westward along the cold tongue (correlation with MEI, r=-0.81), while cyanobacteria concentrations decreased significantly (r=0.78). El Nino produced the reverse pattern, with cyanobacteria populations increasing while diatoms plummeted. The diverse response of phytoplankton in the different major basins of the Pacific suggests the different roles climate variability can play in ocean biology.

  7. Distribution of phytoplankton along an environmental gradient off Kakinada, East Coast of India.

    Digital Repository Service at National Institute of Oceanography (India)

    Ayajuddin, M.; Pandiyarajan, R.S.; Ansari, Z.A.

    (1991) 23-35 3 Buzzi F. Phytoplankton assemblages in two sub-basin of Lake Como. J. Limnol., 61 (2002) 117-128 4 Rey P A, Taylor J C, Lass A, Hensburg L & Vosloo A. Determining the possible application value of diatoms as indicators of general... in the western Bay of Bengal during the northeast monsoon, J. Geophys. Res. 101 (1996) 14011–14025. 15 Naqvi S W A, DeSouza S N & Reddy C V G. Relationship between nutrients and dissolved oxygen with special reference to water masses in western Bay of Bengal...

  8. Effects of entrainment through Oconee Nuclear Station on carbon-14 assimilation rates of phytoplankton

    International Nuclear Information System (INIS)

    Kreh, T.V.; Derwort, J.E.

    1976-01-01

    Carbon assimilation rates of phytoplankton communities entrained through Oconee Nuclear Station were measured on six dates during 1974. Thermal, mechanical, condenser, and multiple entrainment effects on uptake rates were compared by incubating samples in vitro in controlled-temperature water baths. Duplicate light and dark bottles containing water from four cooling-system locations were exposed to temperatures approximating intake and discharge temperatures. The relationships were variable, but exposure of the hypolimnetic intake water at near-discharge temperatures (thermal effect) stimulated primary productivity in four of six experiments. Multiple entrainment and mechanical effects caused no consistent change in assimilation rates

  9. Phytoplankton bloom and subpolar gyre induced dynamics in the North Atlantic

    DEFF Research Database (Denmark)

    Ferreira, Ana Sofia; Hátún, H.; Counillon, F.

    Several hypotheses have been promoted for phytoplankton bloom onset in the North Atlantic. First we show that the bloom dynamics in the northeastern corner stand out from the rest of the subpolar Atlantic, and thus warrants focused attention. We hypothesized that, for this region, late and weak...... blooms are expected in years of a strong subpolar gyre, i.e. strong atmospheric forcing, and cold and low saline conditions. We apply novel phenology algorithms to satellite ocean colour data, and analyse the outcome together with the subpolar gyre index. We find that the relationship between the bloom...

  10. Dose-Effect Relationship of Alkylating Agents on Testicular Function in Male Survivors of Childhood Lymphoma.

    Science.gov (United States)

    Servitzoglou, Marina; De Vathaire, Florent; Oberlin, Odile; Patte, Catherine; Thomas-Teinturier, Cécile

    2015-01-01

    The purpose of our study was to assess the gonadal function in male survivors of childhood lymphoma. We studied 171 male survivors of childhood lymphoma (83 with B-cell non-Hodgkin lymphoma [B-NHL], 32 with T-cell non-Hodgkin lymphoma [T-NHL], 50 with Hodgkin lymphoma [HL], and 6 with anaplastic large-cell lymphoma [ALCL]), measuring follicle-stimulating hormone [FSH] and luteinizing hormone [LH] levels at a median age of 21.1 (17-30.4) years after a median delay of 9.3 (2-22.4) years from treatment. FSH levels were above normal range (≥10 IU/L) in 42.1% and LH levels ≥8 IU/L in only 8.9% of survivors. In multivariate analysis, only the following chemotherapeutic agents were associated with higher FSH or LH levels: cyclophosphamide (P alkylating agents on childhood lymphoma survivors is dose dependent and not correlated to diagnosis, age, or pubertal status at diagnosis.

  11. A study on the relationship dose-effect in case of gamma irradiation on leptospira

    International Nuclear Information System (INIS)

    Vasilevska, M.; Yankov, N.; Grigorov, L.

    1977-01-01

    The influence of gamma rays in doses 400, 2000, 10000 and 100000 rads upon two serotypes of leptospira has been examined. The development of the leptospira after the irradiation was traced upon a dark field of vision and by counting in Petroff-chamber. The morphological and functional changes (size, agility, reproduction and degree of lysis) have been determined and proved to be dependent on the dose. Differences in the indices have been observed in the pathogenic (L.Pomona (local strain Tsalapitsa)) and sapropyte (L.Thraciae (local strain Bulgaria 4)) serotypes, the saprophytic one being more resistant. The age of the culture was significant for the degree of the observed changes. Regarding the eventual practical use of the present study for obtaining killed leptospira antigens doses of 10000 and 100000 rad which are dependent of the age and the pathogenicity of the culture might be taken into consideration. (author)

  12. Dose-effect relationships for malignancy in cells with different genetic characteristics

    International Nuclear Information System (INIS)

    Chadwick, K.H.; Leenhouts, H.P.

    1978-01-01

    By combining the proposals that malignancy behaves as a recessive genetic character, that a somatic mutation is an important step in the development of cancer, and that radiation-induced DNA double-strand breaks are the critical lesions which may lead to cell death, mutation and chromosomal aberrations, considerations can be made and equations derived for the incidence of malignancy in cells having different genotypes. Equations are derived for diploid carrier cells and tetraploid carrier cells, and are compared with data in literature on cell transformation. It is shown that some differences in experimental results could be due to the different genetic character of the cells used. The theoretical considerations are extended to the population which is considered to be constituted of 'carriers' and 'non-carriers' of the recessive malignant genotype. The possible influence of radiation on 'non-carriers' is discussed as are the implications of the presence of two groups within the population for the estimation of risk to low doses of radiation. (author)

  13. Towards uranium dose-effects relationships for bio markers of oxidative stress in fish

    International Nuclear Information System (INIS)

    Buet, A.; Camilleri, V.; Simon, O.; Garnier-Laplace, J.

    2004-01-01

    Within the Envirhom program, the bioavailability of uranium, a widely spread metal in fresh waters, has been studied in various organisms to gain understanding of metal-organisms interactions. Experiments are still in progress to establish a comprehensive basis of early and delayed involved toxicological mechanisms. Uranium is known to be both radio-toxic and chemo-toxic. The cellular damage of radiation, but also of heavy metal exposure, is mainly associated with an oxidative injury due to the formation of reactive oxygen species. Moreover, the intensity of oxidative damages is dependant on the efficiency of antioxidant defense systems of the organism. In this context, short-term experiments were performed with juvenile rainbow trout (Onchorynchus mykiss) in order to (1) assess the response of some antioxidant parameters and other potential bio-markers and (2) to better characterize the kinetics of the responses in relation with U concentrations and exposure duration. Trout were exposed by direct pathway to a range of U concentrations in water (low, medium and high: 20, 100 and 500 μg U.L -1 respectively) during 10 days. Several antioxidant parameters were measured: the rate of reduced glutathione (GSH) that plays a major role in cellular detoxification and antioxidant defense, and the activities of superoxide dismutases (SOD) and catalase that are involved in the detoxification of oxygen reactive species. The activity of glutathione reductase (GR), that restores the pool of GSH was measured, as well as the activity of acetylcholinesterase (AChE), a marker of neurotoxicity. In parallel, U analysis were performed in gill, skin, muscle, skeleton, intestine, liver, kidneys and body residues of exposed trout in order to assess the dependence of biological responses with a potential uranium bioaccumulation in fish tissues. (author)

  14. Prevention of cancer and the dose-effect relationship: the carcinogenic effects of ionizing radiations

    International Nuclear Information System (INIS)

    Tubiana, M.

    2009-01-01

    Cancer prevention has to be based on robust biological and epidemiological data, therefore its reappraisal becomes mandatory in view of recent progress in the understanding of carcinogenesis. The first phase of the carcinogenic process, that of initiation, is generally associated with mutation; however the role of extrinsic mutagens is less critical than was thought two decades ago. During intracellular oxygen metabolism, reactive oxygen species (R.O.S.) are made which are potent mutagens. Defense mechanisms against these intrinsic mutagens include scavenger and enzymatic systems which destroy them (catalase, superoxide dismutase). When the radiation dose is low, DNA repair is very effective as well as the elimination of cells with unrepaired or bad repaired DNA. Therefore a small increase in the number of R.O.S., such as that caused by a small dose of radiation has most probably no significant effect on the risk of DNA damage. These conclusions are consistent with the concept of a practical threshold. The second phase, that of promotion, appears to be the key one. During the promotion phase, initiated cells must acquire new properties (immortalization, release of angiogenic factors, resistance to hypoxia, etc.) in order to become pre-cancerous. This evolution is due to the accumulation in the genome of 6 to 10 new alteration defects. In the clone of initiated cells, the occurrence in one cell of a mutation or an epigenetic event gives birth to a sub clone. There is a Darwinian type competition between the sub clones and those with the more rapid growth because dominant (the acceleration of the growth rate can be due to shorter cell cycles or to an alleviation of cell proliferation exerted by the neighboring cells or the microenvironment). In the dominant sub clones new genomic events provoke the appearance of new sub clones growing more rapidly and having greater autonomy. The process is very slow because the specific genetic events that favour this evolution seldom occur. Promoting factors are agents that either perturb intercellular signalling or stimulate cell proliferation (e.g. hormones) or increase cell mortality: mechanical or chemical irritation (e.g. alcohol, bacteria, viruses) thereby inducing compensatory cell proliferation. Thus, gradually pre-cancerous cells become able to divide more rapidly with greater autonomy. This phase ends when a sub clone of cells has acquired the capacity of autonomous proliferation. The third phase is that of progression during which cells proliferate regularly without any stimulation. In one of the cells of one of the pre-cancerous lesions (e.g. polyps) a cell acquires the capacity of invading surrounding tissue or to metastasize. The whole carcinogenic process is very slow, extending over several decades, because the specific mutations seldom occur and the probability of an accumulation of several specific mutations in the same cell or cell lineage is very small. It can be accelerated by intense stimulation of cell proliferation or genetic instability. Ionizing radiations act firstly as a mutagen, however when the dose is high they also kill a significant proportion of cells and by a homeostatic mechanism they induce cell proliferation and clonal amplification. It has been claimed that even the smallest dose of radiation can induce a cancer. This concept is associated with the L.N.T. model and it is not based on scientific evidence. It has fuelled a fear of radiation which had detrimental consequences. Conversely the high efficacy of defense mechanisms against radio carcinogenesis, particularly when the tissue is not disorganized, can explain the lack of carcinogenic effect of contamination by small doses of radium or thorium which has been observed on radium dial painters or in patients injected with thorotrast. The study of second cancers in patients treated by radiotherapy could provide important information and should be actively pursued with two aims: reduce the incidence of second cancers; to better understand radio carcinogenesis and the relation between dose and carcinogenic effect. (authors)

  15. Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

    DEFF Research Database (Denmark)

    Garnier-Laplace, Jacqueline; Beaugelin-Seiller, Karine; Della-Vedova, Claire

    2015-01-01

    We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011-2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31 μGy h(-1)) with the dos...

  16. Dose effect relationships for radiation induced cancer: relevance of animal evidence

    International Nuclear Information System (INIS)

    Coggle, J.E.

    1982-01-01

    This article is based upon a paper which was presented at the SRP meeting on the Biological Bases of Radiation Protection Standards, October 1981. It is suggested that experimental radiation carcinogenesis data derived from animal studies will probably never provide numerical evidence of risk that is applicable to man. The uncertainties involved in any extrapolation of risk estimates from mice to men surely outweigh the uncertainties in the human epidemiological data. It is also suggested that at least in the foreseeable future animal data will not solve the perennial problem of the shape at low doses of the dose response curve for radiogenic cancer. At most the data may clarify the debate over linearity-non linearity and over the existence or otherwise of a threshold. However, the paper does suggest a very positive role for animal data in providing semi-quantitative generalisations for radiological protection concerning such variables as dose rate, radiation quality, partial body/organ exposure and in situations where the dose is received in a highly inhomogeneous fashion, e.g. the special problems of internal emitters. (author)

  17. [Strabismus surgery in Grave's disease--dose-effect relationships and functional results].

    Science.gov (United States)

    Schittkowski, M; Fichter, N; Guthoff, R

    2004-11-01

    Strabismus in thyroid ophthalmopathy is based on a loss of the contractility and distensibility of the external ocular muscles. Different therapeutic approaches are available, such as recession after pre-. or intraoperative measurement, adjustable sutures, antagonist resection, or contralateral synergist faden-operation. 26 patients with strabismus in thyroid ophthalmopathy were operated between 2000 and 2003. All patients were examined preoperatively, then 1 day and 3 - 6 months (maximum 36 months) postoperatively. Before proceeding with surgery, we waited at least 6 months after stabilization of ocular alignment and normalization of thyroid chemistry. Preoperative vertical deviation was 10-44 PD (mean 22), 3 months postoperatively it was 2-10 PD (mean 1.5). Recession of the fibrotic muscle leads to reproducible results: 3.98 +/- 0.52 PD vertical deviation/mm for the inferior rectus. In the case of a large preoperative deviation a correction should be expected, which might not be sufficient in the first few days or weeks; a second operation should not be carried out before 3 months. 7 patients were operated twice, 1 patient need three operations. 4 patients (preop. 0) achieved no double vision at all; 15 patients (preop. 1) had no double vision in the primary and reading positions; 3 patients (preop. 0) had no double vision with a maximum of 5 PD; 1 patient (preop. 7) had double vision in the primary or reading position even with prisms; and 2 patients (preop. 17) had double vision in every position. We advocate that recession of the restricted inferior or internal rectus muscle is precise, safe and effective in patients with thyroid ophthalmopathy. The recessed muscle should be fixed directly at the sclera to avoid late over-correction through a slipped muscle. The success rate in terms of binocular single vision was 76 % and 88 % with prisms added.

  18. Coupling of heterotrophic bacteria to phytoplankton bloom development at different pCO2 levels: a mesocosm study

    Directory of Open Access Journals (Sweden)

    R. Thyrhaug

    2008-07-01

    Full Text Available The predicted rise in anthropogenic CO2 emissions will increase CO2 concentrations and decrease seawater pH in the upper ocean. Recent studies have revealed effects of pCO2 induced changes in seawater chemistry on a variety of marine life forms, in particular calcifying organisms. To test whether the predicted increase in pCO2 will directly or indirectly (via changes in phytoplankton dynamics affect abundance, activities, and community composition of heterotrophic bacteria during phytoplankton bloom development, we have aerated mesocosms with CO2 to obtain triplicates with three different partial pressures of CO2 (pCO2: 350 μatm (1×CO2, 700 μatm (2×CO2 and 1050 μatm (3×CO2. The development of a phytoplankton bloom was initiated by the addition of nitrate and phosphate. In accordance to an elevated carbon to nitrogen drawdown at increasing pCO2, bacterial production (BPP of free-living and attached bacteria as well as cell-specific BPP (csBPP of attached bacteria were related to the C:N ratio of suspended matter. These relationships significantly differed among treatments. However, bacterial abundance and activities were not statistically different among treatments. Solely community structure of free-living bacteria changed with pCO2 whereas that of attached bacteria seemed to be independent of pCO2 but tightly coupled to phytoplankton bloom development. Our findings imply that changes in pCO2, although reflected by changes in community structure of free-living bacteria, do not directly affect bacterial activity. Furthermore, bacterial activity and dynamics of heterotrophic bacteria, especially of attached bacteria, were tightly correlated to phytoplankton development and, hence, may also potentially depend on changes in pCO2.

  19. Spatial and seasonal variability of fractionated phytoplankton biomass and primary production in the frontal region of the Northern Adriatic Sea

    Directory of Open Access Journals (Sweden)

    M.R. VADRUCCI

    2005-06-01

    Full Text Available Spatial and seasonal patterns of variation of fractionated phytoplankton biomass and primary production and their relationships with nutrient concentrations were analyzed along an inshore - offshore gradient and in relation to the presence of a frontal system in the Northern Adriatic Sea. Sampling was carried out in winter and summer during four oceanographic cruises (June 1996 and 1997, February 1997 and 1998 as part of the PRISMA II project. Water samples for determining nutrient concentrations, phytoplankton biomass (as Chla and primary production (as 14 C assimilation were collected at five optical depths. Sampling stations were located along 2 or 4 parallel transects arranged perpendicularly to the shoreline and the frontal system. The transects were located at such a distance from the coast that the frontal system crossed them at their halfway point. Total dissolved nitrogen (TDN and total dissolved phosphorus concentrations (TDP were 12.41 ± 3 .95 mM and 0.146 ± 0 .070 mM, respectively. The values in the two seasonal periods were similar, decreasing along the inshore-offshore gradient. Values for phytoplankton biomass and primary productionwere higher in the winter than the summer cruises, and decreased, in both seasonal periods, along the inshore / offshore gradient. Moreover, in both seasonal periods, picophytoplankton dominated both biomass and productivity, (56% and 44%, respectively at stations beyond the frontal system, while microphytoplankton was more important at stations inside it (44% and 44%, respectively. Total phytoplankton biomass and primary production were directly related to nutrient concentrations. Regarding size classes, significant patterns of variation with nutrients were observed particularly for biomass. The results indicate that the size structure and function of phytoplankton guilds seem to be mediated by nutrient inflow, as well as by competitive interaction among size fractions.

  20. Infection of phytoplankton by aerosolized marine viruses

    Science.gov (United States)

    Sharoni, Shlomit; Trainic, Miri; Schatz, Daniella; Lehahn, Yoav; Flores, Michel J.; Bidle, Kay D.; Ben-Dor, Shifra; Rudich, Yinon; Vardi, Assaf

    2015-01-01

    Marine viruses constitute a major ecological and evolutionary driving force in the marine ecosystems. However, their dispersal mechanisms remain underexplored. Here we follow the dynamics of Emiliania huxleyi viruses (EhV) that infect the ubiquitous, bloom-forming phytoplankton E. huxleyi and show that EhV are emitted to the atmosphere as primary marine aerosols. Using a laboratory-based setup, we showed that the dynamic of EhV aerial emission is strongly coupled to the host–virus dynamic in the culture media. In addition, we recovered EhV DNA from atmospheric samples collected over an E. huxleyi bloom in the North Atlantic, providing evidence for aerosolization of marine viruses in their natural environment. Decay rate analysis in the laboratory revealed that aerosolized viruses can remain infective under meteorological conditions prevailing during E. huxleyi blooms in the ocean, allowing potential dispersal and infectivity over hundreds of kilometers. Based on the combined laboratory and in situ findings, we propose that atmospheric transport of EhV is an effective transmission mechanism for spreading viral infection over large areas in the ocean. This transmission mechanism may also have an important ecological impact on the large-scale host–virus “arms race” during bloom succession and consequently the turnover of carbon in the ocean. PMID:25964340

  1. Emergent neutrality drives phytoplankton species coexistence

    Science.gov (United States)

    Segura, Angel M.; Calliari, Danilo; Kruk, Carla; Conde, Daniel; Bonilla, Sylvia; Fort, Hugo

    2011-01-01

    The mechanisms that drive species coexistence and community dynamics have long puzzled ecologists. Here, we explain species coexistence, size structure and diversity patterns in a phytoplankton community using a combination of four fundamental factors: organism traits, size-based constraints, hydrology and species competition. Using a ‘microscopic’ Lotka–Volterra competition (MLVC) model (i.e. with explicit recipes to compute its parameters), we provide a mechanistic explanation of species coexistence along a niche axis (i.e. organismic volume). We based our model on empirically measured quantities, minimal ecological assumptions and stochastic processes. In nature, we found aggregated patterns of species biovolume (i.e. clumps) along the volume axis and a peak in species richness. Both patterns were reproduced by the MLVC model. Observed clumps corresponded to niche zones (volumes) where species fitness was highest, or where fitness was equal among competing species. The latter implies the action of equalizing processes, which would suggest emergent neutrality as a plausible mechanism to explain community patterns. PMID:21177680

  2. Bioaccumulation of tritiated water in phytoplankton and trophic transfer of organically bound tritium to the blue mussel, Mytilus edulis

    International Nuclear Information System (INIS)

    Jaeschke, Benedict C.; Bradshaw, Clare

    2013-01-01

    Large releases of tritium are currently permitted in coastal areas due to assumptions that it rapidly disperses in the water and has a low toxicity due to its low energy emissions. This paper presents a laboratory experiment developed to identify previously untested scenarios where tritium may concentrate or transfer in biota relevant to Baltic coastal communities. Phytoplankton populations of Dunaliella tertiolecta and Nodularia spumigena were exposed at different growth-stages, to tritiated water (HTO; 10 MBq l −1 ). Tritiated D. tertiolecta was then fed to mussels, Mytilus edulis, regularly over a period of three weeks. Activity concentrations of phytoplankton and various tissues from the mussel were determined. Both phytoplankton species transformed HTO into organically-bound tritium (OBT) in their tissues. D. tertiolecta accumulated significantly more tritium when allowed to grow exponentially in HTO than if it had already reached the stationary growth phase; both treatments accumulated significantly more than the corresponding treatments of N. spumigena. No effect of growth phase on bioaccumulation of tritium was detectable in N. spumigena following exposure. After mussels were given 3 feeds of tritiated D. tertiolecta, significant levels of tritium were detected in the tissues. Incorporation into most mussel tissues appeared to follow a linear relationship with number of tritiated phytoplankton feeds with no equilibrium, highlighting the potential for biomagnification. Different rates of incorporation in species from a similar functional group highlight the difficulties in using a ‘representative’ species for modelling the transfer and impact of tritium. Accumulations of organic tritium into the mussel tissues from tritiated-phytoplankton demonstrate an environmentally relevant transfer pathway of tritium even when water-concentrations are reduced, adding weight to the assertion that organically bound tritium acts as a persistent organic pollutant. The

  3. Seasonal and interannual variability in the taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon

    Science.gov (United States)

    C. David, McIntire; Larson, Gary L.; Truitt, Robert E.

    2007-01-01

    Taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon, were examined during time periods between 1984 and 2000. The objectives of the study were (1) to investigate spatial and temporal patterns in species composition, chlorophyll concentration, and primary productivity relative to seasonal patterns of water circulation; (2) to explore relationships between water column chemistry and the taxonomic composition of the phytoplankton; and (3) to determine effects of primary and secondary consumers on the phytoplankton assemblage. An analysis of 690 samples obtained on 50 sampling dates from 14 depths in the water column found a total of 163 phytoplankton taxa, 134 of which were identified to genus and 101 were identified to the species or variety level of classification. Dominant species by density or biovolume included Nitzschia gracilis, Stephanodiscus hantzschii, Ankistrodesmus spiralis, Mougeotia parvula, Dinobryon sertularia, Tribonema affine, Aphanocapsa delicatissima, Synechocystis sp., Gymnodinium inversum, and Peridinium inconspicuum. When the lake was thermally stratified in late summer, some of these species exhibited a stratified vertical distribution in the water column. A cluster analysis of these data also revealed a vertical stratification of the flora from the middle of the summer through the early fall. Multivariate test statistics indicated that there was a significant relationship between the species composition of the phytoplankton and a corresponding set of chemical variables measured for samples from the water column. In this case, concentrations of total phosphorus, ammonia, total Kjeldahl nitrogen, and alkalinity were associated with interannual changes in the flora; whereas pH and concentrations of dissolved oxygen, orthophosphate, nitrate, and silicon were more closely related to spatial variation and thermal stratification. The maximum chlorophyll concentration when the lake was thermally stratified

  4. Remote sensing observations of phytoplankton increases triggered by successive typhoons

    Science.gov (United States)

    Huang, Lei; Zhao, Hui; Pan, Jiayi; Devlin, Adam

    2017-12-01

    Phytoplankton blooms in the Western North Pacific, triggered by two successive typhoons with different intensities and translation speeds under different pre-existing oceanic conditions, were observed and analyzed using remotely sensed chlorophyll-a (Chl-a), sea surface temperature (SST), and sea surface height anomaly (SSHA) data, as well as typhoon parameters and CTD (conductivity, temperature, and depth) profiles. Typhoon Sinlaku, with relatively weaker intensity and slower translation speed, induced a stronger phytoplankton bloom than Jangmi with stronger intensity and faster translation speed (Chl-a>0.18 mg·m‒3 versus Chl-aTaiwan Island. Translation speed may be one of the important mechanisms that affect phytoplankton blooms in the study area. Pre-existing cyclonic circulations provided a relatively unstable thermodynamic structure for Sinlaku, and therefore cold water with rich nutrients could be brought up easily. The mixed-layer deepening caused by Typhoon Sinlaku, which occurred first, could have triggered an unfavorable condition for the phytoplankton bloom induced by Typhoon Jangmi which followed afterwards. The sea surface temperature cooling by Jangmi was suppressed due to the presence of the thick upper-ocean mixed-layer, which prevented the deeper cold water from being entrained into the upper-ocean mixed layer, leading to a weaker phytoplankton augment. The present study suggests that both wind (including typhoon translation speed and intensity) and pre-existing conditions (e.g., mixed-layer depths, eddies, and nutrients) play important roles in the strong phytoplankton bloom, and are responsible for the stronger phytoplankton bloom after Sinlaku's passage than that after Jangmi's passage. A new typhoon-influencing parameter is introduced that combines the effects of the typhoon forcing (including the typhoon intensity and translation speed) and the oceanic pre-condition. This parameter shows that the forcing effect of Sinlaku was stronger than

  5. Dynamics of living phytoplankton: Implications for paleoenvironmental reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, A B [Centre for Marine and Environmental Research (CIMA), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)], E-mail: abarbosa@ualg.pt

    2009-01-01

    Phytoplankton is the dominant primary producer in aquatic ecosystems and is considered a gauge of ecological condition and change. Some phytoplankton groups, namely diatoms, dinoflagellates, and coccolithophores, produce morphological or chemical fossils that can be used for paleoenvironmental reconstruction. This study aims to review the processes that regulate dynamics in living phytoplankton and to highlight how this knowledge is used in paleoecological studies. The distribution patterns of phytoplankton in present-day aquatic ecosystems are shaped by the interplay between processes that regulate cell growth and cell death. Cell growth and cell death are regulated by the internal environment of phytoplankton (e.g., specific environmental tolerances, resource uptake properties, cell size, density and morphology, alternative nutritional strategies such as mixotrophy or N{sub 2} uptake, motility, intracellular storage capacities, grazing resistance properties), and by its external environment. The external environment includes variables dependent on the availability of resources (e.g., light intensity, concentration of CO{sub 2} and dissolved inorganic macronutrients and micronutrients, availability of living prey in case of mixotrophs) and variables independent of resources (e.g., temperature, salinity, turbulence, ultraviolet radiation, bioactive compounds, activity of grazers, viruses, and eukaryotic parasites). The importance of recently described loss processes, such as grazing by phagotrophic protists, viral lyses, and programmed cell death, is discussed in the context of its potential impact upon phytoplankton vertical fluxes. Examples of the use of different phytoplankton metrics (e.g. abundance, species composition, species morphology, and elemental composition) to infer contemporaneous as well as past environmental and ecological conditions are critically evaluated.

  6. Dynamics of living phytoplankton: Implications for paleoenvironmental reconstructions

    International Nuclear Information System (INIS)

    Barbosa, A B

    2009-01-01

    Phytoplankton is the dominant primary producer in aquatic ecosystems and is considered a gauge of ecological condition and change. Some phytoplankton groups, namely diatoms, dinoflagellates, and coccolithophores, produce morphological or chemical fossils that can be used for paleoenvironmental reconstruction. This study aims to review the processes that regulate dynamics in living phytoplankton and to highlight how this knowledge is used in paleoecological studies. The distribution patterns of phytoplankton in present-day aquatic ecosystems are shaped by the interplay between processes that regulate cell growth and cell death. Cell growth and cell death are regulated by the internal environment of phytoplankton (e.g., specific environmental tolerances, resource uptake properties, cell size, density and morphology, alternative nutritional strategies such as mixotrophy or N 2 uptake, motility, intracellular storage capacities, grazing resistance properties), and by its external environment. The external environment includes variables dependent on the availability of resources (e.g., light intensity, concentration of CO 2 and dissolved inorganic macronutrients and micronutrients, availability of living prey in case of mixotrophs) and variables independent of resources (e.g., temperature, salinity, turbulence, ultraviolet radiation, bioactive compounds, activity of grazers, viruses, and eukaryotic parasites). The importance of recently described loss processes, such as grazing by phagotrophic protists, viral lyses, and programmed cell death, is discussed in the context of its potential impact upon phytoplankton vertical fluxes. Examples of the use of different phytoplankton metrics (e.g. abundance, species composition, species morphology, and elemental composition) to infer contemporaneous as well as past environmental and ecological conditions are critically evaluated.

  7. Phytoplankton Assemblage Patterns in the Southern Mid-Atlantic Bight

    Science.gov (United States)

    Makinen, Carla; Moisan, Tiffany A. (Editor)

    2012-01-01

    As part of the Wallops Coastal Oceans Observing Laboratory (Wa-COOL) Project, we sampled a time-series transect in the southern Mid-Atlantic Bight (MAB) biweekly. Our 2-year time-series data included physical parameters, nutrient concentrations, and chlorophyll a concentrations. A detailed phytoplankton assemblage structure was examined in the second year. During the 2-year study, chlorophyll a concentration (and ocean color satellite imagery) indicated that phytoplankton blooms occurred in January/February during mixing conditions and in early autumn under stratified conditions. The chlorophyll a concentrations ranged from 0.25 microgram 1(exp -1) to 15.49 microgram 1(exp -1) during the 2-year period. We were able to discriminate approximately 116 different species under phase contrast microscopy. Dominant phytoplankton included Skeletonema costatum, Rhizosolenia spp., and Pseudo-nitzschia pungens. In an attempt to determine phytoplankton species competition/succession within the assemblage, we calculated a Shannon Weaver diversity index for our diatom microscopy data. Diatom diversity was greatest during the winter and minimal during the spring. Diatom diversity was also greater at nearshore stations than at offshore stations. Individual genera appeared patchy, with surface and subsurface patches appearing abruptly and persisting for only 1-2 months at a time. The distribution of individual species differed significantly from bulk variables of the assemblage (chlorophyll a ) and total phytoplankton assemblage (cells), which indicates that phytoplankton species may be limited in growth in ways that differ from those of the total assemblage. Our study demonstrated a highly diverse phytoplankton assemblage throughout the year, with opportunistic species dominating during spring and fall in response to seasonal changes in temperature and nutrients in the southern MAB.

  8. Phosphorus physiological ecology and molecular mechanisms in marine phytoplankton.

    Science.gov (United States)

    Lin, Senjie; Litaker, Richard Wayne; Sunda, William G

    2016-02-01

    Phosphorus (P) is an essential nutrient for marine phytoplankton and indeed all life forms. Current data show that P availability is growth-limiting in certain marine systems and can impact algal species composition. Available P occurs in marine waters as dissolved inorganic phosphate (primarily orthophosphate [Pi]) or as a myriad of dissolved organic phosphorus (DOP) compounds. Despite numerous studies on P physiology and ecology and increasing research on genomics in marine phytoplankton, there have been few attempts to synthesize information from these different disciplines. This paper is aimed to integrate the physiological and molecular information on the acquisition, utilization, and storage of P in marine phytoplankton and the strategies used by these organisms to acclimate and adapt to variations in P availability. Where applicable, we attempt to identify gaps in our current knowledge that warrant further research and examine possible metabolic pathways that might occur in phytoplankton from well-studied bacterial models. Physical and chemical limitations governing cellular P uptake are explored along with physiological and molecular mechanisms to adapt and acclimate to temporally and spatially varying P nutrient regimes. Topics covered include cellular Pi uptake and feedback regulation of uptake systems, enzymatic utilization of DOP, P acquisition by phagotrophy, P-limitation of phytoplankton growth in oceanic and coastal waters, and the role of P-limitation in regulating cell size and toxin levels in phytoplankton. Finally, we examine the role of P and other nutrients in the transition of phytoplankton communities from early succession species (diatoms) to late succession ones (e.g., dinoflagellates and haptophytes). © 2015 Phycological Society of America.

  9. Competition between a nonallelopathic phytoplankton and an allelopathic phytoplankton species under predation.

    Science.gov (United States)

    Kengwoung-Keumo, Jean-Jacques

    2016-08-01

    We propose a model of two-species competition in the chemostat for a single growth-limiting, nonreproducing resource that extends that of Roy [38]. The response functions are specified to be Michaelis-Menten, and there is no predation in Roy's work. Our model generalizes Roy's model to general uptake functions. The competition is exploitative so that species compete by decreasing the common pool of resources. The model also allows allelopathic effects of one toxin-producing species, both on itself (autotoxicity) and on its nontoxic competitor (phytotoxicity). We show that a stable coexistence equilibrium exists as long as (a) there are allelopathic effects and (b) the input nutrient concentration is above a critical value. The model is reconsidered under instantaneous nutrient recycling. We further extend this work to include a zooplankton species as a fourth interacting component to study the impact of predation on the ecosystem. The zooplankton species is allowed to feed only on the two phytoplankton species which are its perfectly substitutable resources. Each of the models is analyzed for boundedness, equilibria, stability, and uniform persistence (or permanence). Each model structure fits very well with some harmful algal bloom observations where the phytoplankton assemblage can be envisioned in two compartments, toxin producing and non-toxic. The Prymnesium parvum literature, where the suppressing effects of allelochemicals are quite pronounced, is a classic example. This work advances knowledge in an area of research becoming ever more important, which is understanding the functioning of allelopathy in food webs.

  10. Interacting Effects of Light and Iron Availability on the Coupling of Photosynthetic Electron Transport and CO2-Assimilation in Marine Phytoplankton.

    Science.gov (United States)

    Schuback, Nina; Schallenberg, Christina; Duckham, Carolyn; Maldonado, Maria T; Tortell, Philippe D

    2015-01-01

    Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. These bio-optical approaches require a conversion factor to derive ecologically-relevant rates of CO2-assimilation from estimates of electron transport in photosystem II. The required conversion factor varies significantly across phytoplankton taxa and environmental conditions, but little information is available on its response to iron limitation. In this study, we examine the role of iron limitation, and the interacting effects of iron and light availability, on the coupling of photosynthetic electron transport and CO2-assimilation in marine phytoplankton. Our results show that excess irradiance causes increased decoupling of carbon fixation and electron transport, particularly under iron limiting conditions. We observed that reaction center II specific rates of electron transport (ETR(RCII), mol e- mol RCII(-1) s(-1)) increased under iron limitation, and we propose a simple conceptual model for this observation. We also observed a strong correlation between the derived conversion factor and the expression of non-photochemical quenching. Utilizing a dataset from in situ phytoplankton assemblages across a coastal--oceanic transect in the Northeast subarctic Pacific, this relationship was used to predict ETR(RCII): CO2-assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements.

  11. Emergence of Algal Blooms: The Effects of Short-Term Variability in Water Quality on Phytoplankton Abundance, Diversity, and Community Composition in a Tidal Estuary

    Directory of Open Access Journals (Sweden)

    Todd A. Egerton

    2014-01-01

    Full Text Available Algal blooms are dynamic phenomena, often attributed to environmental parameters that vary on short timescales (e.g., hours to days. Phytoplankton monitoring programs are largely designed to examine long-term trends and interannual variability. In order to better understand and evaluate the relationships between water quality variables and the genesis of algal blooms, daily samples were collected over a 34 day period in the eutrophic Lafayette River, a tidal tributary within Chesapeake Bay’s estuarine complex, during spring 2006. During this period two distinct algal blooms occurred; the first was a cryptomonad bloom and this was followed by a bloom of the mixotrophic dinoflagellate, Gymnodinium instriatum. Chlorophyll a, nutrient concentrations, and physical and chemical parameters were measured daily along with phytoplankton abundance and community composition. While 65 phytoplankton species from eight major taxonomic groups were identified in samples and total micro- and nano-phytoplankton cell densities ranged from 5.8 × 106 to 7.8 × 107 cells L−1, during blooms, cryptomonads and G. instriatum were 91.6% and 99.0%, respectively, of the total phytoplankton biomass during blooms. The cryptomonad bloom developed following a period of rainfall and concomitant increases in inorganic nitrogen concentrations. Nitrate, nitrite and ammonium concentrations 0 to 5 days prior were positively lag-correlated with cryptomonad abundance. In contrast, the G. insriatum bloom developed during periods of low dissolved nitrogen concentrations and their abundance was negatively correlated with inorganic nitrogen concentrations.

  12. Interacting Effects of Light and Iron Availability on the Coupling of Photosynthetic Electron Transport and CO2-Assimilation in Marine Phytoplankton.

    Directory of Open Access Journals (Sweden)

    Nina Schuback

    Full Text Available Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. These bio-optical approaches require a conversion factor to derive ecologically-relevant rates of CO2-assimilation from estimates of electron transport in photosystem II. The required conversion factor varies significantly across phytoplankton taxa and environmental conditions, but little information is available on its response to iron limitation. In this study, we examine the role of iron limitation, and the interacting effects of iron and light availability, on the coupling of photosynthetic electron transport and CO2-assimilation in marine phytoplankton. Our results show that excess irradiance causes increased decoupling of carbon fixation and electron transport, particularly under iron limiting conditions. We observed that reaction center II specific rates of electron transport (ETR(RCII, mol e- mol RCII(-1 s(-1 increased under iron limitation, and we propose a simple conceptual model for this observation. We also observed a strong correlation between the derived conversion factor and the expression of non-photochemical quenching. Utilizing a dataset from in situ phytoplankton assemblages across a coastal--oceanic transect in the Northeast subarctic Pacific, this relationship was used to predict ETR(RCII: CO2-assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements.

  13. Interacting Effects of Light and Iron Availability on the Coupling of Photosynthetic Electron Transport and CO2-Assimilation in Marine Phytoplankton

    Science.gov (United States)

    Schuback, Nina; Schallenberg, Christina; Duckham, Carolyn; Maldonado, Maria T.; Tortell, Philippe D.

    2015-01-01

    Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. These bio-optical approaches require a conversion factor to derive ecologically-relevant rates of CO2-assimilation from estimates of electron transport in photosystem II. The required conversion factor varies significantly across phytoplankton taxa and environmental conditions, but little information is available on its response to iron limitation. In this study, we examine the role of iron limitation, and the interacting effects of iron and light availability, on the coupling of photosynthetic electron transport and CO2-assimilation in marine phytoplankton. Our results show that excess irradiance causes increased decoupling of carbon fixation and electron transport, particularly under iron limiting conditions. We observed that reaction center II specific rates of electron transport (ETRRCII, mol e- mol RCII-1 s-1) increased under iron limitation, and we propose a simple conceptual model for this observation. We also observed a strong correlation between the derived conversion factor and the expression of non-photochemical quenching. Utilizing a dataset from in situ phytoplankton assemblages across a coastal – oceanic transect in the Northeast subarctic Pacific, this relationship was used to predict ETRRCII: CO2-assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements. PMID:26171963

  14. Methanol Production by a Broad Phylogenetic Array of Marine Phytoplankton.

    Directory of Open Access Journals (Sweden)

    Tracy J Mincer

    Full Text Available Methanol is a major volatile organic compound on Earth and serves as an important carbon and energy substrate for abundant methylotrophic microbes. Previous geochemical surveys coupled with predictive models suggest that the marine contributions are exceedingly large, rivaling terrestrial sources. Although well studied in terrestrial ecosystems, methanol sources are poorly understood in the marine environment and warrant further investigation. To this end, we adapted a Purge and Trap Gas Chromatography/Mass Spectrometry (P&T-GC/MS method which allowed reliable measurements of methanol in seawater and marine phytoplankton cultures with a method detection limit of 120 nanomolar. All phytoplankton tested (cyanobacteria: Synechococcus spp. 8102 and 8103, Trichodesmium erythraeum, and Prochlorococcus marinus, and Eukarya (heterokont diatom: Phaeodactylum tricornutum, coccolithophore: Emiliania huxleyi, cryptophyte: Rhodomonas salina, and non-diatom heterokont: Nannochloropsis oculata produced methanol, ranging from 0.8-13.7 micromolar in culture and methanol per total cellular carbon were measured in the ranges of 0.09-0.3%. Phytoplankton culture time-course measurements displayed a punctuated production pattern with maxima near early stationary phase. Stabile isotope labeled bicarbonate incorporation experiments confirmed that methanol was produced from phytoplankton biomass. Overall, our findings suggest that phytoplankton are a major source of methanol in the upper water column of the world's oceans.

  15. Phytoplankton growth and microzooplankton grazing in the subtropical Northeast Atlantic.

    Directory of Open Access Journals (Sweden)

    Carlos Cáceres

    Full Text Available Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E. Our design included two phytoplankton size fractions (0.2-5 µm and >5 µm and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11-1.60 d(-1, especially in the case of the large fraction. Grazing rates were also high (0.15-1.29 d(-1, suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O2 supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres.

  16. Methanol Production by a Broad Phylogenetic Array of Marine Phytoplankton.

    Science.gov (United States)

    Mincer, Tracy J; Aicher, Athena C

    2016-01-01

    Methanol is a major volatile organic compound on Earth and serves as an important carbon and energy substrate for abundant methylotrophic microbes. Previous geochemical surveys coupled with predictive models suggest that the marine contributions are exceedingly large, rivaling terrestrial sources. Although well studied in terrestrial ecosystems, methanol sources are poorly understood in the marine environment and warrant further investigation. To this end, we adapted a Purge and Trap Gas Chromatography/Mass Spectrometry (P&T-GC/MS) method which allowed reliable measurements of methanol in seawater and marine phytoplankton cultures with a method detection limit of 120 nanomolar. All phytoplankton tested (cyanobacteria: Synechococcus spp. 8102 and 8103, Trichodesmium erythraeum, and Prochlorococcus marinus), and Eukarya (heterokont diatom: Phaeodactylum tricornutum, coccolithophore: Emiliania huxleyi, cryptophyte: Rhodomonas salina, and non-diatom heterokont: Nannochloropsis oculata) produced methanol, ranging from 0.8-13.7 micromolar in culture and methanol per total cellular carbon were measured in the ranges of 0.09-0.3%. Phytoplankton culture time-course measurements displayed a punctuated production pattern with maxima near early stationary phase. Stabile isotope labeled bicarbonate incorporation experiments confirmed that methanol was produced from phytoplankton biomass. Overall, our findings suggest that phytoplankton are a major source of methanol in the upper water column of the world's oceans.

  17. Spatio-temporal organization of phytoplankton in Peipsi Lake

    Directory of Open Access Journals (Sweden)

    Sharov Andrey

    2016-12-01

    Full Text Available In the article, the results of the study of phytoplankton received at 16 stations of the Lake Peipsi in the spring (May, summer (August and autumn (October within the period of 2012–2015 were analyzed. 186 phytoplankton species were found. The list of mass taxa is given. It was noted that phytoplankton biomass had wide amplitude of annual average values in different lakes: Lake Peipsi/Chudskoe 2.1 ± 0.2 (0.3–23.0 mg / L; Lake Pihkva/Pskovskoe 5.4 ± 1.4 (0.4–34.0 mg / L and Lake Lämmijärv/Teploe 6.1 ± 1.2 (3.4–25.1 mg / l. According to species composition, structure and biomass of phytoplankton the lake belongs to the mesotrophic reservoirs with eutrophic features, as it was in previous years of observation. The water quality in the different parts of Lake Peipsi corresponded to conditionally pure water (1st quality class and slightly polluted one(2nd quality class. Correlation between characteristics of phytoplankton and the environmental factors (temperature, water level, transparency, N and P concentration in water was detected.

  18. [Phytoplankton community in a recreational fishing lake, Brazil].

    Science.gov (United States)

    Matsuzaki, Mayla; Mucci, José Luiz Negrão; Rocha, Aristides Almeida

    2004-10-01

    The assessment of water quality and phytoplankton community in recreational environments allows to setting management programs aiming at preventing potential harm to human health. The purpose of the present study was to describe phytoplankton seasonal changes in a freshwater system and their relation to water quality. The recreational fishing lake is located in the southern area of the city of São Paulo, Brazil. Water samples were collected in three previously selected sites in the lake throughout a year and analyzed regarding floristic composition and physical and chemical parameters. The phytoplankton qualitative analysis revealed 91 taxa distributed among eight classes: Chlorophyceae, Cyanophyceae, Euglenophyceae, Zygnemaphyceae, Bacillariophyceae, Xantophyceae, Dinophyceae, and Chrysophyceae. Some physical and chemical parameters seemed to influence phytoplankton community behavior. Chlorophyceae development was favored by local conditions. Among the species of cyanobacteria identified, Microcystis paniformis, Cylindrospermopsis raciborskii, and Anabaena species were the most important due to their ability to produce toxins, posing a high risk to public health. Some physical and chemical parameters had an impact on the structure of phytoplankton community. The presence of Microcystis paniformis, Cylindrospermopsis raciborskii and Anabaena species indicates toxic potential and likelihood of public health problems unless there is constant monitoring. Further studies are recommended to prevent hazardous effects to the environment and public health.

  19. Application of a laser fluorometer for discriminating phytoplankton species

    Science.gov (United States)

    Chen, Peng; Pan, Delu; Mao, Zhihua

    2015-04-01

    A portable laser-induced fluorescence system for discriminating phytoplankton species has been developed. It consists of a high pulsed repetition frequency (10-kHz) microchip laser at 405 nm, a reflective fluorescent probe and a broadband micro spectrometer. The measured fluorescent spectra were overlapped by various fluorescent components, and were then decomposed by a bi-Gaussian mixture model. A spectral shape description index was designed to characterize fluorescent spectral shapes for descriminating the phytoplankton species cultured in our laboratory. Using clustering analysis, the samples of eight phytoplankton species belonging to two divisions of Bacillariophyta and Dinophyta were divided into six categories: 1) Chaetoceros debilis, Thalassiosira rotula; 2) Prorocentrum donghaiense, Prorocentrum dentatum; 3) Gymnodinium simplex; 4) Alexandrium tamarense; 5) Karenia mikimotoi; and 6) Akashiwo sanguinea. The phytoplankton species belonging to Bacillariophyta were well separated from those belonging to Dinophyta. In addition, the phytoplankton species belonging to Dinophyta were successfully distinguished from each other at genus level. The portable system is expected to be used both in vivo and in the field.

  20. Methanol Production by a Broad Phylogenetic Array of Marine Phytoplankton

    Science.gov (United States)

    Mincer, Tracy J.; Aicher, Athena C.

    2016-01-01

    Methanol is a major volatile organic compound on Earth and serves as an important carbon and energy substrate for abundant methylotrophic microbes. Previous geochemical surveys coupled with predictive models suggest that the marine contributions are exceedingly large, rivaling terrestrial sources. Although well studied in terrestrial ecosystems, methanol sources are poorly understood in the marine environment and warrant further investigation. To this end, we adapted a Purge and Trap Gas Chromatography/Mass Spectrometry (P&T-GC/MS) method which allowed reliable measurements of methanol in seawater and marine phytoplankton cultures with a method detection limit of 120 nanomolar. All phytoplankton tested (cyanobacteria: Synechococcus spp. 8102 and 8103, Trichodesmium erythraeum, and Prochlorococcus marinus), and Eukarya (heterokont diatom: Phaeodactylum tricornutum, coccolithophore: Emiliania huxleyi, cryptophyte: Rhodomonas salina, and non-diatom heterokont: Nannochloropsis oculata) produced methanol, ranging from 0.8–13.7 micromolar in culture and methanol per total cellular carbon were measured in the ranges of 0.09–0.3%. Phytoplankton culture time-course measurements displayed a punctuated production pattern with maxima near early stationary phase. Stabile isotope labeled bicarbonate incorporation experiments confirmed that methanol was produced from phytoplankton biomass. Overall, our findings suggest that phytoplankton are a major source of methanol in the upper water column of the world’s oceans. PMID:26963515

  1. Phytoplankton Growth and Microzooplankton Grazing in the Subtropical Northeast Atlantic

    Science.gov (United States)

    Cáceres, Carlos; Taboada, Fernando González; Höfer, Juan; Anadón, Ricardo

    2013-01-01

    Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E). Our design included two phytoplankton size fractions (0.2–5 µm and >5 µm) and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11–1.60 d−1), especially in the case of the large fraction. Grazing rates were also high (0.15–1.29 d−1), suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O2 supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres. PMID:23935946

  2. Estimating phytoplankton photosynthesis by active fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Falkowski, P.G.; Kolber, Z.

    1992-01-01

    Photosynthesis can be described by target theory, At low photon flux densities, photosynthesis is a linear function of irradiance (I), The number of reaction centers (n), their effective absorption capture cross section {sigma}, and a quantum yield {phi}. As photosynthesis becomes increasingly light saturated, an increased fraction of reaction centers close. At light saturation the maximum photosynthetic rate is given as the product of the number of reaction centers (n) and their maximum electron transport rate (I/{tau}). Using active fluorometry it is possible to measure non-destructively and in real time the fraction of open or closed reaction centers under ambient irradiance conditions in situ, as well as {sigma} and {phi} {tau} can be readily, calculated from knowledge of the light saturation parameter, I{sub k} (which can be deduced by in situ by active fluorescence measurements) and {sigma}. We built a pump and probe fluorometer, which is interfaced with a CTD. The instrument measures the fluorescence yield of a weak probe flash preceding (f{sub 0}) and succeeding (f{sub 0}) a saturating pump flash. Profiles of the these fluorescence yields are used to derive the instantaneous rate of gross photosynthesis in natural phytoplankton communities without any incubation. Correlations with short-term simulated in situ radiocarbon measurements are extremely high. The average slope between photosynthesis derived from fluorescence and that measured by radiocarbon is 1.15 and corresponds to the average photosynthetic quotient. The intercept is about 15% of the maximum radiocarbon uptake and corresponds to the average net community respiration. Profiles of photosynthesis and sections showing the variability in its composite parameters reveal a significant effect of nutrient availability on biomass specific rates of photosynthesis in the ocean.

  3. Estimating phytoplankton photosynthesis by active fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Falkowski, P.G.; Kolber, Z.

    1992-10-01

    Photosynthesis can be described by target theory, At low photon flux densities, photosynthesis is a linear function of irradiance (I), The number of reaction centers (n), their effective absorption capture cross section {sigma}, and a quantum yield {phi}. As photosynthesis becomes increasingly light saturated, an increased fraction of reaction centers close. At light saturation the maximum photosynthetic rate is given as the product of the number of reaction centers (n) and their maximum electron transport rate (I/{tau}). Using active fluorometry it is possible to measure non-destructively and in real time the fraction of open or closed reaction centers under ambient irradiance conditions in situ, as well as {sigma} and {phi} {tau} can be readily, calculated from knowledge of the light saturation parameter, I{sub k} (which can be deduced by in situ by active fluorescence measurements) and {sigma}. We built a pump and probe fluorometer, which is interfaced with a CTD. The instrument measures the fluorescence yield of a weak probe flash preceding (f{sub 0}) and succeeding (f{sub 0}) a saturating pump flash. Profiles of the these fluorescence yields are used to derive the instantaneous rate of gross photosynthesis in natural phytoplankton communities without any incubation. Correlations with short-term simulated in situ radiocarbon measurements are extremely high. The average slope between photosynthesis derived from fluorescence and that measured by radiocarbon is 1.15 and corresponds to the average photosynthetic quotient. The intercept is about 15% of the maximum radiocarbon uptake and corresponds to the average net community respiration. Profiles of photosynthesis and sections showing the variability in its composite parameters reveal a significant effect of nutrient availability on biomass specific rates of photosynthesis in the ocean.

  4. Low dose effects detected by micronucleus assay in lymphocytes

    International Nuclear Information System (INIS)

    Koeteles, G.J.; Bojtor, I.; Kubasova, T.; Horvath, G.

    1997-01-01

    The effects of low doses of X-rays between 0.01 and 1 Gy were studied on whole blood samples of various individuals using the cytokinesis-blocked lymphocyte micronucleus assay as an endpoint. The adaptive response could be induced in G 0 cells by 0.01 Gy followed by 1 Gy challenging dose within a time period of 8 hours, in vitro. The probability distribution of micronucleus increments in those samples which had received very low doses in the range 0.01-0.05 Gy proved to be of asymmetrical type (i.e. lognormal) -very likely to the same shape which has been verified for unirradiated (control) population - while the variable turned to be normally distributed at or above 1 Gy. Profound changes have been experienced in the main characteristics of the linear dose - response relationship and in regression parameters, as well, when successively lessened dose ranges were studied toward 0.01 Gy. In the range below ∼ 0.2 Gy the response were found to be unrelated to the absorbed dose. These findings suggest that in (very) low dose range a higher attention should be needed to biological parameters like repair, protective mechanisms and antioxidant capacities, rather than to the absorbed radiation energy only. (author)

  5. Marine phytoplankton stoichiometry mediates nonlinear interactions between nutrient supply, temperature, and atmospheric CO2

    Science.gov (United States)

    Moreno, Allison R.; Hagstrom, George I.; Primeau, Francois W.; Levin, Simon A.; Martiny, Adam C.

    2018-05-01

    Marine phytoplankton stoichiometry links nutrient supply to marine carbon export. Deviations of phytoplankton stoichiometry from Redfield proportions (106C : 1P) could therefore have a significant impact on carbon cycling, and understanding which environmental factors drive these deviations may reveal new mechanisms regulating the carbon cycle. To explore the links between environmental conditions, stoichiometry, and carbon cycling, we compared four different models of phytoplankton C : P: a fixed Redfield model, a model with C : P given as a function of surface phosphorus concentration (P), a model with C P given as a function of temperature, and a new multi-environmental model that predicts C : P as a function of light, temperature, and P. These stoichiometric models were embedded into a five-box ocean circulation model, which resolves the three major ocean biomes (high-latitude, subtropical gyres, and tropical upwelling regions). Contrary to the expectation of a monotonic relationship between surface nutrient drawdown and carbon export, we found that lateral nutrient transport from lower C : P tropical waters to high C : P subtropical waters could cause carbon export to decrease with increased tropical nutrient utilization. It has been hypothesized that a positive feedback between temperature and pCO2, atm will play an important role in anthropogenic climate change, with changes in the biological pump playing at most a secondary role. Here we show that environmentally driven shifts in stoichiometry make the biological pump more influential, and may reverse the expected positive relationship between temperature and pCO2, atm. In the temperature-only model, changes in tropical temperature have more impact on the Δ pCO2, atm (˜ 41 ppm) compared to subtropical temperature changes (˜ 4.5 ppm). Our multi-environmental model predicted a decline in pCO2, atm of ˜ 46 ppm when temperature spanned a change of 10 °C. Thus, we find that variation in marine phytoplankton

  6. Nutrient regimes and their effect on distribution of phytoplankton in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Paul, J.T.; Ramaiah, N.; Sardessai, S.

    of Plankton Research 27, 545– 556. Smayda, T.J., 1980. Phytoplankton species succession. In: Morris, I. (Ed.), The Physiological Ecology of Phytoplankton. University of California Press, Berkeley, pp. 493–570. Sournia, A., 1970. Les cyanophycees dans le...

  7. Climate warming and interannual variability of phytoplankton phenology in the Northern Red Sea

    KAUST Repository

    Gittings, John

    2016-01-01

    of phytoplankton biomass), we investigate the potential impacts of climate warming on phytoplankton abundance and phenology in the Northern Red Sea by exploring the mechanistic links with the regional physical environment. The results of the analysis reveal that

  8. Measured and numerically partitioned phytoplankton spectral absorption coefficients in inland waters

    NARCIS (Netherlands)

    Zhang, Y.; Liu, M.; Van Dijk, M.A.; Zhu, G.; Gong, Z.; Li, Y.M.; Qin, B.

    2009-01-01

    Total particulate, tripton and phytoplankton absorption coefficients were measured for eutrophic (Lake Taihu), meso-eutrophic (Lake Tianmuhu) and mesotrophic waters (the Three Gorges Reservoir) in China using the quantitative filter technique. Meanwhile, tripton and phytoplankton absorption

  9. Impact of the antifouling agent Irgarol 1051 on marine phytoplankton species

    NARCIS (Netherlands)

    Buma, Anita G. J.; Sjollema, Sascha B.; van de Poll, Willem H.; Klamer, Hans J. C.; Bakker, Joop F.

    In the present study we tested the hypothesis that environmental concentrations of the antifouling agent Irgarol 1051, as measured in coastal Western European waters, affect marine phytoplankton performance. The impact of Irgarol was investigated in the phytoplankton species Thalassiosira

  10. Specific features of phytoplankton consolidation in techno-ecosystems of nuclear and thermal power plants

    International Nuclear Information System (INIS)

    Novoselova, T.N.

    2013-01-01

    The features of forming of phytoplankton species composition and quantitative indexes in the cooling ponds of NPP TPP were considered. Causative agents of water 'flowering' registered in the phytoplankton of cooling ponds of Zaporozhskaya NPP and Khmelnitski NPP were indicated.

  11. Subsurface phytoplankton blooms fuel pelagic production in the North Sea

    DEFF Research Database (Denmark)

    Richardson, Kathrine; Visser, Andre; Pedersen, Flemming

    2000-01-01

    The seasonal phytoplankton biomass distribution pattern in stratified temperate marine waters is traditionally depicted as consisting of spring and autumn blooms. The energy source supporting pelagic summer production is believed to be the spring bloom. However, the spring bloom disappears...... relatively quickly from the water column and a large proportion of the material sedimenting to the bottom following the spring bloom is often comprised of intact phytoplankton cells. Thus, it is easy to argue that the spring bloom is fueling the energy demands of the benthos, but more difficult to argue...... convincingly that energy fixed during the spring bloom is fueling the pelagic production occurring during summer months. We argue here that periodic phytoplankton blooms are occurring during the summer in the North Sea at depths of >25 m and that the accumulated new production [sensu (Dugdale and Goering...

  12. Coagulation efficiency and aggregate formation in marine phytoplankton

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Andersen, K.P.; Dam, H.G.

    1990-01-01

    , and even nutrient replete cells are significantly sticky. Stickiness is highest (> 10-1) for S. costatum cells in the transition between the exponential and the stationary growth phase. The implications for phytoplankton aggregate formation and subsequent sedimentation in the sea of these two different......Flocculation of phytoplankters into large, rapidly sinking aggregates has been implicated as a mechanism of vertical transport of phytoplankton to the sea floor which could have global significance. The formation rate of phytoplankton aggregates depends on the rate at which single cells collide...... and demonstrate that three species of diatoms grown in the laboratory (Phaeodactylum tricornutum, Thalassiosira pseudonana, Skeletonema costatum) are indeed significantly sticky and form aggregates upon collison. The dependency of stickiness on nutrient limitation and growth was studied in the two latter species...

  13. Phytoplankton distribution in three thermally distinct reactor cooling reservoirs

    International Nuclear Information System (INIS)

    Wilde, E.W.

    1983-01-01

    Phytoplankton community structure was studied in relation to physicochemical characteristics of three South Carolina reservoirs in close proximity and of similar age and bottom type. Thermal alteration, resulting from the input of cooling water from a nuclear reactor, was substantially different in each reservoir. This provided an opportunity to compare water temperature effects separated from season. Water temperature (when examined independently in statistical models) appeared to be less important than other environmental variables in determining phytoplankton community structure. Pond C, a reservoir receiving intensely heated effluent (> 20 0 C ΔT), displayed low species diversity (Shannon-Weaver H 0 C in summer. Par Pond, having a maximum ΔT of 5 0 C, displayed no temperature-induced alteration of phytoplankton community structure

  14. A seasonal diary of phytoplankton in the North Atlantic

    DEFF Research Database (Denmark)

    Lindemann, Christian; St. John, Michael

    2014-01-01

    In recent years new biological and physical controls have been suggested to drive phytoplankton bloom dynamics in the North Atlantic. A better understanding of the mechanisms driving primary production has potentially important implications for the understanding of the biological carbon pump...... are not mutually exclusive, but rather complementary. Thus, moving beyond the “single mechanism” point of view, here we present an integrated conceptual model of the physical and biological controls on phytoplankton dynamics in the North Atlantic. Further we believe that the acclimation of physiological rates can...... play an important role in mediating phytoplankton dynamics. Thus, this view emphasizes the occurrence of multiple controls and relates their variations in impact to climate change...

  15. Global patterns of phytoplankton dynamics in coastal ecosystems

    Science.gov (United States)

    Paerl, H.; Yin, Kedong; Cloern, J.

    2011-01-01

    Scientific Committee on Ocean Research Working Group 137 Meeting; Hangzhou, China, 17-21 October 2010; Phytoplankton biomass and community structure have undergone dramatic changes in coastal ecosystems over the past several decades in response to climate variability and human disturbance. These changes have short- and long-term impacts on global carbon and nutrient cycling, food web structure and productivity, and coastal ecosystem services. There is a need to identify the underlying processes and measure the rates at which they alter coastal ecosystems on a global scale. Hence, the Scientific Committee on Ocean Research (SCOR) formed Working Group 137 (WG 137), "Global Patterns of Phytoplankton Dynamics in Coastal Ecosystems: A Comparative Analysis of Time Series Observations" (http://wg137.net/). This group evolved from a 2007 AGU-sponsored Chapman Conference entitled "Long Time-Series Observations in Coastal Ecosystems: Comparative Analyses of Phytoplankton Dynamics on Regional to Global Scales.".

  16. Eddy-driven stratification initiates North Atlantic spring phytoplankton blooms.

    Science.gov (United States)

    Mahadevan, Amala; D'Asaro, Eric; Lee, Craig; Perry, Mary Jane

    2012-07-06

    Springtime phytoplankton blooms photosynthetically fix carbon and export it from the surface ocean at globally important rates. These blooms are triggered by increased light exposure of the phytoplankton due to both seasonal light increase and the development of a near-surface vertical density gradient (stratification) that inhibits vertical mixing of the phytoplankton. Classically and in current climate models, that stratification is ascribed to a springtime warming of the sea surface. Here, using observations from the subpolar North Atlantic and a three-dimensional biophysical model, we show that the initial stratification and resulting bloom are instead caused by eddy-driven slumping of the basin-scale north-south density gradient, resulting in a patchy bloom beginning 20 to 30 days earlier than would occur by warming.

  17. Ammonium uptake by phytoplankton regulates nitrification in the sunlit ocean.

    Directory of Open Access Journals (Sweden)

    Jason M Smith

    Full Text Available Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA, are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1 to those in well-lit layers (<1 nmol L-1 d-1. During another set of experiments, nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean.

  18. PHYTOPLANKTON COMPOSITION IN FISH FARMS ALONG THE EASTERN ADRIATIC COAST

    Directory of Open Access Journals (Sweden)

    Marija Tomec

    2006-10-01

    Full Text Available Investigations of net phytoplankton composition were performed at three fish farms situated at the northern, middle and southern part of the eastern Adriatic Sea coast, respectively. In the northern part investigations were conducted in the Limski kanal, in the middle part at the Ugljan island and in the southern part in the place Drače on the Pelješac peninsula (Figure 1. At all three localities fish culture included mostly two species: gilthead sea bream (Sparus aurata and sea bass (Dicentrarchus labrax. Beside some physico–chemical parameters (sea water temperature, salinity special attention was placed on the examination of qualitative net phytoplankton composition, which was conducted in the period of May and November 2004 and May and October 2005. Samples were collected at the depths of 0. 5 and 4 meters. According to the physico–chemical parameters, sea water temperature was influenced by the temperature of the environment. Qualitative net phytoplankton composition consisted of 153 microphytic species belonging to the systematic compartments of Cyanobacteria, Chrysophyta and Dinophyta (Table 1. The most numerous algal group were diatoms or Bacillarophyceae (84 species or 55% with relative frequencies of species from 1 to 7. Taxonomic composition of diatoms showed the community Chaetoceros–Rhizosolenia (Proboscia as the dominant one. The second numerically most dominant compartment were Dinophyta (62 species or 401% with dominant the species of the genera Ceratium and Protoperidinium. Relative frequencies of species was ranging from 1 to 7 (mass presence of specimens in the water column. From Cyanobacteria (4 species or 3%, only filamentous algae were determined, with individual presence in net phytoplankton composition. Qualitative net phytoplankton composition suggests the similarity of species composition in the water column at all investigated fish farms. From the obtained characteristics of net phytoplankton composition

  19. Mercury methylation and bacterial activity associated to tropical phytoplankton

    International Nuclear Information System (INIS)

    Coelho-Souza, Sergio A.; Guimaraes, Jean R.D.; Mauro, Jane B.N.; Miranda, Marcio R.; Azevedo, Sandra M.F.O.

    2006-01-01

    The methylated form of mercury (Hg), methylmercury (MeHg), is one of the most toxic pollutants. Biotic and/or abiotic methylation, often associated to sulfate-reducing bacteria metabolism, occurs in aquatic environments and in many tropical areas, mostly in the periphyton associated to floating macrophyte roots. Data about mercury methylation by phytoplankton are scarce and the aim of this study was to verify the biotic influence in the methylation process in Microcystis aeruginosa and Sineccocystis sp. laboratory strains and in natural populations of phytoplankton from two different aquatic systems, the mesotrophic Ribeirao das Lajes reservoir and hypereutrophic oligohaline Jacarepagua lagoon, Rio de Janeiro state, Brazil. Adapted radiochemical techniques were used to measure sulfate-reduction, mercury methylation and bacterial activity in phytoplankton samples. Methyl- 203 Hg formation from added inorganic 203 Hg and 3 H-Leucine uptake were measured by liquid scintillation as well as sulfate-reduction, estimated as H 2 35 S produced from added Na 2 35 SO 4 . There was no significant difference in low methylation potentials (0.37%) among the two cyanobacterium species studied in laboratory conditions. At Ribeirao das Lajes reservoir, there was no significant difference in methylation, bacterial activity and sulfate-reduction of surface sediment between the sampling points. Methylation in sediments (3-4%) was higher than in phytoplankton (1.5%), the opposite being true for bacterial activity (sediment mean 6.6 against 150.3 nmol gdw -1 h -1 for phytoplankton samples). At Jacarepagua lagoon, an expressive bacterial activity (477.1 x 10 3 nmol gdw -1 h -1 at a concentration of 1000 nM leucine) and sulfate-reduction (∼21% H 2 35 S trapped) associated to phytoplankton (mostly cyanobacteria M. aeruginosa) was observed, but mercury methylation was not detected

  20. Mercury methylation and bacterial activity associated to tropical phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Coelho-Souza, Sergio A. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil); Guimaraes, Jean R.D. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil)]. E-mail: jeanrdg@biof.ufrj.br; Mauro, Jane B.N. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil); Miranda, Marcio R. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil); Azevedo, Sandra M.F.O. [Laboratorio de Ecofisiologia e Toxicologia de Cianobacterias, IBCCF/UFRJ, RJ (Brazil)

    2006-07-01

    The methylated form of mercury (Hg), methylmercury (MeHg), is one of the most toxic pollutants. Biotic and/or abiotic methylation, often associated to sulfate-reducing bacteria metabolism, occurs in aquatic environments and in many tropical areas, mostly in the periphyton associated to floating macrophyte roots. Data about mercury methylation by phytoplankton are scarce and the aim of this study was to verify the biotic influence in the methylation process in Microcystis aeruginosa and Sineccocystis sp. laboratory strains and in natural populations of phytoplankton from two different aquatic systems, the mesotrophic Ribeirao das Lajes reservoir and hypereutrophic oligohaline Jacarepagua lagoon, Rio de Janeiro state, Brazil. Adapted radiochemical techniques were used to measure sulfate-reduction, mercury methylation and bacterial activity in phytoplankton samples. Methyl-{sup 203}Hg formation from added inorganic {sup 203}Hg and {sup 3}H-Leucine uptake were measured by liquid scintillation as well as sulfate-reduction, estimated as H{sub 2} {sup 35}S produced from added Na{sub 2} {sup 35}SO{sub 4}. There was no significant difference in low methylation potentials (0.37%) among the two cyanobacterium species studied in laboratory conditions. At Ribeirao das Lajes reservoir, there was no significant difference in methylation, bacterial activity and sulfate-reduction of surface sediment between the sampling points. Methylation in sediments (3-4%) was higher than in phytoplankton (1.5%), the opposite being true for bacterial activity (sediment mean 6.6 against 150.3 nmol gdw{sup -1} h{sup -1} for phytoplankton samples). At Jacarepagua lagoon, an expressive bacterial activity (477.1 x 10{sup 3} nmol gdw{sup -1} h{sup -1} at a concentration of 1000 nM leucine) and sulfate-reduction ({approx}21% H{sub 2} {sup 35}S trapped) associated to phytoplankton (mostly cyanobacteria M. aeruginosa) was observed, but mercury methylation was not detected.

  1. Latitudinal phytoplankton distribution and the neutral theory of biodiversity

    KAUST Repository

    Chust, Guillem

    2012-11-16

    Recent studies have suggested that global diatom distributions are not limited by dispersal, in the case of both extant species and fossil species, but rather that environmental filtering explains their spatial patterns. Hubbell\\'s neutral theory of biodiversity provides a framework in which to test these alternatives. Our aim is to test whether the structure of marine phytoplankton (diatoms, dinoflagellates and coccolithophores) assemblages across the Atlantic agrees with neutral theory predictions. We asked: (1) whether intersite variance in phytoplankton diversity is explained predominantly by dispersal limitation or by environmental conditions; and (2) whether species abundance distributions are consistent with those expected by the neutral model. Location: Meridional transect of the Atlantic (50° N-50° S). Methods: We estimated the relative contributions of environmental factors and geographic distance to phytoplankton composition using similarity matrices, Mantel tests and variation partitioning of the species composition based upon canonical ordination methods. We compared the species abundance distribution of phytoplankton with the neutral model using Etienne\\'s maximum-likelihood inference method. Results: Phytoplankton communities are slightly more determined by niche segregation (24%), than by dispersal limitation and ecological drift (17%). In 60% of communities, the assumption of neutrality in species\\' abundance distributions could not be rejected. In tropical zones, where oceanic gyres enclose large stable water masses, most communities showed low species immigration rates; in contrast, we infer that communities in temperate areas, out of oligotrophic gyres, have higher rates of species immigration. Conclusions: Phytoplankton community structure is consistent with partial niche assembly and partial dispersal and drift assembly (neutral processes). The role of dispersal limitation is almost as important as habitat filtering, a fact that has been

  2. Influence of the Yellow Sea Warm Current on phytoplankton community in the central Yellow Sea

    Science.gov (United States)

    Liu, Xin; Chiang, Kuo-Ping; Liu, Su-Mei; Wei, Hao; Zhao, Yuan; Huang, Bang-Qin

    2015-12-01

    In early spring, a hydrological front emerges in the central Yellow Sea, resulting from the intrusion of the high temperature and salinity Yellow Sea Warm Current (YSWC). The present study, applying phytoplankton pigments and flow cytometry measurements in March of 2007 and 2009, focuses on the biogeochemical effects of the YSWC. The nutrients fronts were coincident with the hydrological front, and a positive linear relationship between nitrate and salinity was found in the frontal area. This contrast with the common situation of coastal waters where high salinity values usually correlate with poor nutrients. We suggested nutrient concentrations of the YSWC waters might have been enhanced by mixing with the local nutrient-rich waters when it invaded the Yellow Sea from the north of the Changjiang estuary. In addition, our results indicate that the relative abundance of diatoms ranged from 26% to 90%, showing a higher value in the YSCC than in YSWC waters. Similar distributions were found between diatoms and dinoflagellates, however the cyanobacteria and prasinophytes showed an opposite distribution pattern. Good correlations were found between the pigments and flow cytometry observations on the picophytoplankton groups. Prasinophytes might be the major contributor to pico-eukaryotes in the central Yellow Sea as similar distributional patterns and significant correlations between them. It seems that the front separates the YSWC from the coastal water, and different phytoplankton groups are transported in these water masses and follow their movement. These results imply that the YSWC plays important roles in the distribution of nutrients, phytoplankton biomass and also in the community structure of the central Yellow Sea.

  3. Variability in global ocean phytoplankton distribution over 1979-2007

    Science.gov (United States)

    Masotti, I.; Alvain, S.; Moulin, C.; Antoine, D.

    2009-04-01

    Recently, reanalysis of long-term ocean color data (CZCS and SeaWiFS; Antoine et al., 2005) has shown that world ocean average phytoplankton chlorophyll levels show an increase of 20% over the last two decades. It is however unknown whether this increase is associated with a change in the distribution of phytoplankton groups or if it simply corresponds to an increase of the productivity. Within the framework of the GLOBPHY project, the distribution of the phytoplankton groups was monitored by applying the PHYSAT method (Alvain et al., 2005) to the historical ocean color data series from CZCS, OCTS and SeaWiFS sensors. The PHYSAT algorithm allows identification of several phytoplankton, like nanoeucaryotes, prochlorococcus, synechococcus and diatoms. Because both sensors (OCTS-SeaWiFS) are very similar, OCTS data were processed with the standard PHYSAT algorithm to cover the 1996-1997 period during which a large El Niño event occurred, just before the SeaWiFS era. Our analysis of this dataset (1996-2006) evidences a strong variability in the distribution of phytoplankton groups at both regional and global scales. In the equatorial region (0°-5°S), a three-fold increase of nanoeucaryotes frequency was detected in opposition to a two-fold decrease of synechococcus during the early stages of El Niño conditions (May-June 1997, OCTS). The impact of this El Niño is however not confined to the Equatorial Pacific and has affected the global ocean. The processing of CZCS data with PHYSAT has required several adaptations of this algorithm due to the lower performances and the reduced number of spectral bands of the sensor. Despites higher uncertainties, the phytoplankton groups distribution obtained with CZCS is globally consistent with that of SeaWiFS. A comparison of variability in global phytoplankton distribution between 1979-1982 (CZCS) and 1999-2002 (SeaWiFS) suggests an increase in nanoeucaryotes at high latitudes (>40°) and in the equatorial region (10°S-10

  4. Dynamical Analysis of a Nitrogen-Phosphorus-Phytoplankton Model

    Directory of Open Access Journals (Sweden)

    Yunli Deng

    2015-01-01

    Full Text Available This paper presents a nitrogen-phosphorus-phytoplankton model in a water ecosystem. The main aim of this research is to analyze the global system dynamics and to study the existence and stability of equilibria. It is shown that the phytoplankton-eradication equilibrium is globally asymptotically stable if the input nitrogen concentration is less than a certain threshold. However, the coexistence equilibrium is globally asymptotically stable as long as it exists. The system is uniformly persistent within threshold values of certain key parameters. Finally, to verify the results, numerical simulations are provided.

  5. Heterotrophic bacterial responses to the winter–spring phytoplankton bloom in open waters of the NW Mediterranean

    KAUST Repository

    Gomes, Ana

    2014-12-03

    The response of planktonic heterotrophic prokaryotes to the NW Mediterranean winter–spring offshore phytoplankton bloom was assessed in 3 cruises conducted in March, April–May and September 2009. Bulk measurements of phytoplankton and bacterioplankton biomass and production were complemented with an insight into bacterial physiological structure by single-cell analysis of nucleic acid content [low (LNA) vs. high (HNA)] and membrane integrity (“Live” vs. “Dead” cells). Bacterial production empirical conversion factors (0.82±0.25 SE kg C mol leucine−1) were almost always well below the theoretical value. Major differences in most microbial variables were found among the 3 periods, which varied from extremely high phytoplankton biomass and production during the bloom in March (>1 g C m−2 d−1 primary production) to typically oligotrophic conditions during September stratification (<200 mg C m−2 d−1). In both these periods bacterial production was ~30 mg C m−2 d−1 while very large bacterial production (mean 228, with some stations exceeding 500 mg C m−2 d−1) but low biomass was observed during the April–May post-bloom phase. The contribution of HNA (30–67%) and “Live” cells (47–97%) were temporally opposite in the study periods, with maxima in March and September, respectively. Different relationships were found between physiological structure and bottom-up variables, with HNA bacteria apparently more responsive to phytoplankton only during the bloom, coinciding with larger average cell sizes of LNA bacteria. Moderate phytoplankton–bacterioplankton coupling of biomass and activity was only observed in the bloom and post-bloom phases, while relationships between both compartments were not significant under stratification. With all data pooled, bacteria were only weakly bottom-up controlled. Our analyses show that the biomass and production of planktonic algae and bacteria followed opposite paths in the transition from bloom to

  6. A multiomics approach to study the microbiome response to phytoplankton blooms.

    Science.gov (United States)

    Song, Liyan

    2017-06-01

    Phytoplankton blooms are predictable features of marine and freshwater habitats. Despite a good knowledge base of the environmental factors controlling blooms, complex interactions between the bacterial and archaeal communities and phytoplankton bloom taxa are only now emerging. Here, the current research on bacterial community's structural and functional response to phytoplankton blooms is reviewed and discussed and further research is proposed. More attention should be paid on structure and function of autotrophic bacteria and archaea during phytoplankton blooms. A multiomics integration approach is needed to investigate bacterial and archaeal communities' diversity, metabolic diversity, and biogeochemical functions of microbial interactions during phytoplankton blooms.

  7. Induced growth of phytoplankton using two fertilizers (NPK and ...

    African Journals Online (AJOL)

    African Journal of Biotechnology ... A total of 1244 phytoplankton made up of 20 species, belonging to three families: Bacillariophyceae (diatoms), Cyanophyceae (blue-green algae) and Euglenophyceae (euglenophytes) were observed. Out of these algae, tanks C had 51.7%, B 33.2%, A 10.6% and D 4.5% phytoplankters.

  8. Seasonal and interannual variability in phytoplankton biomass on ...

    African Journals Online (AJOL)

    The most probable causative mechanism is suggested to be anomalous advective fluxes of warm surface water into areas typically of high biomass deriving from the Agulhas Current retroflection in the south. Studying variability in phytoplankton biomass on the continental shelf in the context of large-scale oceanic ...

  9. Spatial-temporal changes in phytoplankton biomass and primary ...

    African Journals Online (AJOL)

    Spatial-temporal variations in phytoplankton primary production (PP) and biomass (B) were studied for a period of about one year, from July 1999 to July 2000. In addition, changes in corresponding environmental variables were examined. Sampling took place at two stations in Chwaka Bay, one located in mangrove areas, ...

  10. Influence of Water quality on the biodiversity of phytoplankton in ...

    African Journals Online (AJOL)

    Dhamra estuarine ecosystem is a hotspot of rich biological diversity which supports a patch of mangrove along with unique flora and fauna. In this study, the diversity of phytoplankton population and other factors that control their growth and biodiversity were investigated. The samples were collected monthly from Dhamra ...

  11. Saccharides enhance iron bioavailability to Southern Ocean phytoplankton

    NARCIS (Netherlands)

    Hassler, C.S.; Schoemann, V.; Nichols, C.M.; Butler, E.C.V.; Boyd, P.W.; Nichols, C.M.

    2011-01-01

    Iron limits primary productivity in vast regions of the ocean. Given that marine phytoplankton contribute up to 40% of global biological carbon fixation, it is important to understand what parameters control the availability of iron (iron bioavailability) to these organisms. Most studies on iron

  12. Nutrients and toxin producing phytoplankton control algal blooms ...

    Indian Academy of Sciences (India)

    Unknown

    capacity for the phytoplankton population depends on the nutrient level. The role of nutrient ..... irregular oscillations with time, gives rise to rich class of models ..... the Indian river lagoon, Florida, USA; J. Plankton Res. 26. 1229– ... Sea Res. 18 82–96. Graneli E et al 1989 From anoxia to fish poisoning: The last ten years of ...

  13. The decline in phytoplankton biomass and prawn catches in the ...

    African Journals Online (AJOL)

    The world's oceans have seen significant declines in phytoplankton-the primary food source in the marine environment. This decline in primary producers is likely to impact the food chain and functions of most coastal and marine ecosystems. Despite being one of the most productive marine fishing grounds in the Western ...

  14. Environmental variables, algal pigments and phytoplankton in the ...

    African Journals Online (AJOL)

    The phytoplankton diversity, environmental variables and algal pigments of the Atlantic Ocean off the coast of Badagry, Lagos were investigated for twelve months between May 2015 and April 2016. The water chemistry characteristics reflected sea water conditions. At the two stations, the range of values recorded for some ...

  15. Phytoplankton growth inhibited by the toxic and bacterivorous ciliate

    NARCIS (Netherlands)

    Schaafsma, F.L.; Peperzak, L.

    2013-01-01

    The ubiquitous marine ciliate Uronema marinum is mainly bacterivorous. It was therefore surprising that in a ciliate-contaminated experiment the growth rate of the phytoplankton species Emiliania huxleyi was significantly reduced. As U. marinum does not ingest E. huxleyi cells, their growth

  16. A turbulence-induced switch in phytoplankton swimming behavior

    Science.gov (United States)

    Carrara, Francesco; Sengupta, Anupam; Stocker, Roman

    2015-11-01

    Phytoplankton, unicellular photosynthetic organisms that form the basis of life in aquatic environments, are frequently exposed to turbulence, which has long been known to affect phytoplankton fitness and species succession. Yet, mechanisms by which phytoplankton may adapt to turbulence have remained unknown. Here we present a striking behavioral response of a motile species - the red-tide-producing raphidophyte Heterosigma akashiwo - to hydrodynamic cues mimicking those experienced in ocean turbulence. In the absence of turbulence, H. akashiwo exhibits preferential upwards swimming (`negative gravitaxis'), observable as a strong accumulation of cells at the top of an experimental container. When cells were exposed to overturning in an automated chamber - representing a minimum experimental model of rotation by Kolmogorov-scale turbulent eddies - the population robustly split in two nearly equi-abundant subpopulations, one swimming upward and one swimming downward. Microscopic observations at the single-cell level showed that the behavioral switch was accompanied by a rapid morphological change. A mechanistic model that takes into account cell shape confirms that modulation of morphology can alter the hydrodynamic stress distribution over the cell body, which, in turn, triggers the observed switch in phytoplankton migration direction. This active response to fluid flow, whereby microscale morphological changes influence ocean-scale migration dynamics, could be part of a bet-hedging strategy to maximize the chances of at least a fraction of the population evading high-turbulence microzones.

  17. Ammonium uptake by phytoplankton regulates nitrification in the sunlit ocean.

    Science.gov (United States)

    Smith, Jason M; Chavez, Francisco P; Francis, Christopher A

    2014-01-01

    Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA), are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1) to those in well-lit layers (ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean.

  18. A Satellite-Based Lagrangian View on Phytoplankton Dynamics

    Science.gov (United States)

    Lehahn, Yoav; d'Ovidio, Francesco; Koren, Ilan

    2018-01-01

    The well-lit upper layer of the open ocean is a dynamical environment that hosts approximately half of global primary production. In the remote parts of this environment, distant from the coast and from the seabed, there is no obvious spatially fixed reference frame for describing the dynamics of the microscopic drifting organisms responsible for this immense production of organic matter—the phytoplankton. Thus, a natural perspective for studying phytoplankton dynamics is to follow the trajectories of water parcels in which the organisms are embedded. With the advent of satellite oceanography, this Lagrangian perspective has provided valuable information on different aspects of phytoplankton dynamics, including bloom initiation and termination, spatial distribution patterns, biodiversity, export of carbon to the deep ocean, and, more recently, bottom-up mechanisms that affect the distribution and behavior of higher-trophic-level organisms. Upcoming submesoscale-resolving satellite observations and swarms of autonomous platforms open the way to the integration of vertical dynamics into the Lagrangian view of phytoplankton dynamics.

  19. Phytoplankton diversity in the Cross River Estuary of Nigeria | Ekwu ...

    African Journals Online (AJOL)

    Bacillariophyceae (Diatom) was the most abundant phytoplankton family, constituting 71.58% of total Algal density, followed by Chlorophyceae (Green algae) with 13.84%, Cyanobacteria (Blue-green algae) with 12.69%, while Euglenophyceae (Green flagellates) and Dinophyceae (Dinoflagellates) recorded 0.88% and ...

  20. Phytoplankton defence mechanisms: traits and trade-offs

    DEFF Research Database (Denmark)

    Pančić, Marina; Kiørboe, Thomas

    2018-01-01

    mechanisms in phytoplankton are diverse and include physiological (e.g. toxicity, bioluminescence), morphological (e.g. silica shell, colony formation), and behavioural (e.g. escape response) traits. However, the function of many of the proposed defence mechanisms remains elusive, and the costs and benefits...

  1. 36 Dry Season Phytoplankton Composition Of Ibiekuma Dam ...

    African Journals Online (AJOL)

    `123456789jkl''''#

    freshwater algae of Edo State. To benefit from ... Algae. (phytoplankton) are the source of oxygen in aquatic systems and are the main ... be used in determining water pollution level. A dam is a ... taken in situ, using a mercury in bulb glass.

  2. Phytoplankton responses to changes in macrophyte density in a ...

    African Journals Online (AJOL)

    The response of phytoplankton population dynamics to changes in densities of Nymphaea lotus L. and Polygonum limbatum Meisn. was studied in an artificial pond in Zaria, Nigeria, from June to November 2007. Antagonistic effects of these macrophytes on Netrium sp., Staurastrum sp., Ulothrix sp., Marssionella sp. and ...

  3. Composition of phytoplankton algae in Gubi Reservoir, Bauchi ...

    African Journals Online (AJOL)

    Studies on the distribution, abundance and taxonomic composition of phytoplankton algae in Gubi reservoir were carried out for 12 months (from January to December 1995). Of the 26 algal taxa identified, 14 taxa belonged to the diatoms, 8 taxa were green algae while 4 taxa belonged to the blue-green algae. Higher cell ...

  4. Physicochemical conditions in affecting the distribution of spring phytoplankton community

    Science.gov (United States)

    Wei, Yuqiu; Liu, Haijiao; Zhang, Xiaodong; Xue, Bing; Munir, Sonia; Sun, Jun

    2017-11-01

    To better understand the physicochemical conditions in affecting regional distribution of phytoplankton community, one research cruise was carried out in the Bohai Sea and Yellow Sea during 3rd and 23th May, 2010. The phytoplankton community, including Bacillariophyta (105 taxa), Pyrrophyta (54 taxa), Chrysophyta (1 taxon) and Chlorophyta (2 taxa), had been identified and clearly described from six ecological provinces. And, the six ecological provinces were partitioned based on the top twenty dominant species related with notable physicochemical parameters. In general, the regional distributions of phytoplankton ecological provinces were predominantly influenced by the physicochemical properties induced by the variable water masses and circulations. The predominant diatoms in most of water samples showed well adaptability in turbulent and eutrophic conditions. However, several species of dinoflagellates e.g., Protoperidinium conicum, Protoperidinium triestinum, Protoperidinium sp. and Gymnodinium lohmanni preferred warmer, saltier and nutrient-poor environment. Moreover, the dinoflagellates with high frequency in the Yellow Sea might be transported from the Yellow Sea Warm Current. The horizontal distribution of phytoplankton was depicted by diatoms and controlled by phosphate concentration, while the vertical distribution was mainly supported by light and nutrients availability in the subsurface and bottom layers, respectively.

  5. The phytoplankton of Great Bitter Lake, Egypt, including the impacts ...

    African Journals Online (AJOL)

    The phytoplankton community comprised mostly diatoms and blue-green algae, although dinoflagellates and green algae were important at times. Local effects of effluent from a drain coming from the city of Ismailia were evident, although the effect of tourist hotels at Palma Beach was not detectable. The discharge of ...

  6. Phytoplankton diversity and abundance in Ndop wetland plain ...

    African Journals Online (AJOL)

    Eight divisions of phytoplankton were recorded: Chlorophyta (26.42%), Bacillariophyta (20.76%), Pyrrhophyta (20.76%), Cyanophyta (15.09%), Chrysophyta (1.87%), Xanthophyta (3.77%), Rhodophyta (1.87%), and Euglenophyta (7.55%). The most abundant species included Microcystis aeruginosa, Anacystis sp., ...

  7. Increase of atmospheric CO2 promotes phytoplankton productivity

    NARCIS (Netherlands)

    Schippers, P.; Lürling, M.F.L.L.W.; Scheffer, M.

    2004-01-01

    It is usually thought that unlike terrestrial plants, phytoplankton will not show a significant response to an increase of atmospheric CO2. Here we suggest that this view may be biased by a neglect of the effects of carbon (C) assimilation on the pH and the dissociation of the C species. We show

  8. Does ultraviolet radiation affect the xanthophyll cycle in marine phytoplankton?

    NARCIS (Netherlands)

    van de Poll, W.H.; Buma, A.G.J.

    2009-01-01

    This Perspective summarizes the state of knowledge of the impact of ultraviolet radiation on the photoprotective xanthophyll cycle in marine phytoplankton. Excess photosynthetically active radiation (PAR; 400-700 nm) and ultraviolet radiation (UVR; 280-400 nm) affect various cellular processes and

  9. An automated platform for phytoplankton ecology and aquatic ecosystem monitoring

    NARCIS (Netherlands)

    Pomati, F.; Jokela, J.; Simona, M.; Veronesi, M.; Ibelings, B.W.

    2011-01-01

    High quality monitoring data are vital for tracking and understanding the causes of ecosystem change. We present a potentially powerful approach for phytoplankton and aquatic ecosystem monitoring, based on integration of scanning flow-cytometry for the characterization and counting of algal cells

  10. Phytoplankton dynamics and periodicity in two cascading warm ...

    African Journals Online (AJOL)

    In addition to annual patterns, changes in chlorophyll content implied progressive long-term changes in trophic status, especially in Albert Falls, with the emergence of various 'new' taxa (and/or higher peak densities of others). Consideration of phytoplankton dynamics in terms of functional groups offers certain advantages ...

  11. Resource limitation and the biochemical composition of marine phytoplankton

    NARCIS (Netherlands)

    Grosse, J.

    2016-01-01

    The aim of the work presented in this thesis was to determine the effects of nutrient availability on the biomolecule composition and synthesis in North Sea phytoplankton. Nutrient availability in coastal seas has changed substantially over the past decades due to anthropogenic activities. Riverine

  12. The role of viruses in marine phytoplankton mortality

    NARCIS (Netherlands)

    Baudoux, Anne-Claire

    2007-01-01

    Unicellular algae (phytoplankton) form the basis of the marine foodchain and thus play a critical role in the ocean’s geochemical processes. It is thus somewhat surprising that the mechanisms driving their mortality are still not fully understood. Traditionally, grazing by microzooplankton and

  13. Observations and Models of Highly Intermittent Phytoplankton Distributions

    Science.gov (United States)

    Mandal, Sandip; Locke, Christopher; Tanaka, Mamoru; Yamazaki, Hidekatsu

    2014-01-01

    The measurement of phytoplankton distributions in ocean ecosystems provides the basis for elucidating the influences of physical processes on plankton dynamics. Technological advances allow for measurement of phytoplankton data to greater resolution, displaying high spatial variability. In conventional mathematical models, the mean value of the measured variable is approximated to compare with the model output, which may misinterpret the reality of planktonic ecosystems, especially at the microscale level. To consider intermittency of variables, in this work, a new modelling approach to the planktonic ecosystem is applied, called the closure approach. Using this approach for a simple nutrient-phytoplankton model, we have shown how consideration of the fluctuating parts of model variables can affect system dynamics. Also, we have found a critical value of variance of overall fluctuating terms below which the conventional non-closure model and the mean value from the closure model exhibit the same result. This analysis gives an idea about the importance of the fluctuating parts of model variables and about when to use the closure approach. Comparisons of plot of mean versus standard deviation of phytoplankton at different depths, obtained using this new approach with real observations, give this approach good conformity. PMID:24787740

  14. Phytoplankton Abundance and Distribution of Fish Earthen Ponds in ...

    African Journals Online (AJOL)

    ADOWIE PERE

    2017-12-15

    Dec 15, 2017 ... ... to determine the effect of some physicochemical parameters on the community structure of three on- research ... The spatial distribution of ... important for growth and density of phytoplankton on ... response to changes in the surrounding environment ... Lagos, Nigeria were concentrated on the taxonomic.

  15. Chemical warfare in freshwater, allelopathic effects of macrophytes on phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field

  16. Chemical warfare in freshwater. Allelpathic effects of macrophytes on phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field

  17. SHORT-TERM EFFECT OF DIESEL OIL ON PHYTOPLANKTON

    African Journals Online (AJOL)

    PROF. EKWEME

    Short-term effect of Nigerian diesel oil was tested on the phytoplankton species in Great Kwa River ... aquatic environment. Plant life is the basis of all food web in nature and hence constitutes the makes this fundamental contribution by photosynthesis, utilizing radiant energy to .... (2 cells/ml) re-colonized the area. The three ...

  18. Phytoplankton Virus Production Negatively Affected by Iron Limitation

    NARCIS (Netherlands)

    Slagter, H.A.; Gerringa, L.J.A.; Brussaard, C.P.D.

    2016-01-01

    Fe-limited monocultures of the ubiquitous algae Micromonas pusilla and Phaeocystis globosa were infected with their respective viruses (MpV and PgV) to ascertain the effect of Fe-limitation on phytoplankton host-virus dynamics. The effect of the viral shunt on Fe concentrations and bioavailability

  19. Light utilization and photoinhibition of photosynthesis in marine phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Falkowski, P.G., Greene, R., Kolber, Z.

    1993-12-31

    Introduction to Phytoplankton. Based on the record of the oldest identifiable fossils, the first oxygenic photosynthetic organisms appeared about 2 {times} l0{sup 9} years ago in the form of marine single celled, planktonic procaryotes (Riding, 1992; Sarmiento and Bender, 1993). In the intervening eons, phytoplankton have evolved and diversified; presently they represent at least 11 classes of procaryotic and euacaryotic photoautotrophs. While the carbon of these organisms cumulatively amounts to only 1 to 2% of the global plant biomass, they fix between 35 and 50 gigatonnes ({times} 10{sup 9} metric tons) of carbon annually, about 40% of the global total (Falkowski and Woodhead, 1992). On average, each gram of phytoplankton chlorophyll converts about 6% of the photosynthetically active radiation (440 to 700 nm) incident on the sea surface to photochemical energy (Morel, 1978). Despite a great deal of variability in ocean environments, this photosynthetic conversion efficiency is relatively constant for integrated water column production (Morel, 1978; Falkowski, 1981; Platt, 1986; Morel, 1991). Here we review the factors determining light utilization efficiency of phytoplankton in the oceans, and the physiological acclimations which have evolved to optimize light utilization efficiency.

  20. A Satellite-Based Lagrangian View on Phytoplankton Dynamics.

    Science.gov (United States)

    Lehahn, Yoav; d'Ovidio, Francesco; Koren, Ilan

    2018-01-03

    The well-lit upper layer of the open ocean is a dynamical environment that hosts approximately half of global primary production. In the remote parts of this environment, distant from the coast and from the seabed, there is no obvious spatially fixed reference frame for describing the dynamics of the microscopic drifting organisms responsible for this immense production of organic matter-the phytoplankton. Thus, a natural perspective for studying phytoplankton dynamics is to follow the trajectories of water parcels in which the organisms are embedded. With the advent of satellite oceanography, this Lagrangian perspective has provided valuable information on different aspects of phytoplankton dynamics, including bloom initiation and termination, spatial distribution patterns, biodiversity, export of carbon to the deep ocean, and, more recently, bottom-up mechanisms that affect the distribution and behavior of higher-trophic-level organisms. Upcoming submesoscale-resolving satellite observations and swarms of autonomous platforms open the way to the integration of vertical dynamics into the Lagrangian view of phytoplankton dynamics.

  1. A morphological classification capturing functional variation in phytoplankton

    NARCIS (Netherlands)

    Kruk, C.; Huszar, V.M.; Peeters, E.T.H.M.; Bonilla, S.; Costa, L.; Lürling, M.F.L.L.W.; Reynolds, C.S.; Scheffer, M.

    2010-01-01

    1. A logical way of distinguishing functional groups of phytoplankton is to cluster species according to their functional traits, such as growth rate and nutrient assimilation constants. However, data for such an approach are lacking for the vast majority of the species. 2. In this study, we show

  2. A glimpse into the future composition of marine phytoplankton communities

    Directory of Open Access Journals (Sweden)

    Esteban eAcevedo-Trejos

    2014-07-01

    Full Text Available It is expected that climate change will have significant impacts on ecosystems. Most model projections agree that the ocean will experience stronger stratification and less nutrient supply from deep waters. These changes will likely affect marine phytoplankton communities and will thus impact on the higher trophic levels of the oceanic food web. The potential consequences of future climate change on marine microbial communities can be investigated and predicted only with the help of mathematical models. Here we present the application of a model that describes aggregate properties of marine phytoplankton communities and captures the effects of a changing environment on their composition and adaptive capacity. Specifically, the model describes the phytoplankton community in terms of total biomass, mean cell size, and functional diversity. The model is applied to two contrasting regions of the Atlantic Ocean (tropical and temperate and is tested under two emission scenarios: SRES A2 or ``business as usual'' and SRES B1 or ``local utopia''. We find that all three macroecological properties will decline during the next century in both regions, although this effect will be more pronounced in the temperate region. Being consistent with previous model predictions, our results show that a simple trait-based modelling framework represents a valuable tool for investigating how phytoplankton communities may reorganize under a changing climate.

  3. Seasonal effects of the low-grade heat on a phytoplankton community

    International Nuclear Information System (INIS)

    McMahon, J.W.; Docherty, A.E.

    1980-06-01

    Field studies, carried out over the period 1976 March to December, examined the effects of heat-enriched cooling waters on a natural phytoplankton community. Algal concentrations, composition, species succession and carbon fixation rates were determined twice-weekly in heated and unheated (control) polyethylene enclosures located in a northern oligotrophic lake. Results were compared with data collected from the open lake. Of 31 species quantitatively studied, eleven dominant species were examined in detail. A marked response to heat enrichment by the phytoplankton occurred in the spring and was attributed to a single species of Bacillariophyceae - Synedra ulna. Species composition and seasonal succession patterns were similar in the experimental column, the control column and the lake. The relationship between production biomass quotients (P/B) and water temperature in the lake and experimental enclosure is discussed. It is suggested that thermal enrichment might be used beneficially in cold waters for enhancing biomass production of unicellular aquatic organisms. This increased availability of food, in conjuction with increased water temperatures, might then accelerate productivity of filter-feeding zooplankton and other herbivores. (auth)

  4. Interannual Variation in Phytoplankton Concentration and Community in the Pacific Ocean

    Science.gov (United States)

    Rousseaux, C. S.; Gregg, W. W.

    2011-01-01

    Climate events such as El Nino have been shown to have an effect on the biology of our ocean. Because of the lack of data, we still have very little knowledge about the spatial and temporal effect these climate events may have on biological marine systems. In this study, we used the NASA Ocean Biogeochemical Model (NOBM) to assess the interannual variability in phytoplankton community in the Pacific Ocean between 1998 and 2005. In the North Central and Equatorial Pacific Ocean, changes in the Multivariate El Nino Index were associated with changes in phytoplankton composition. The model identified an increase in diatoms of approx.33 % in the equatorial Pacific in 1999 during a La Nina event. This increase in diatoms coincided with a decrease of approx.11 % in cyanobacteria concentration. The inverse relationship between cyanobacteria and diatoms concentration was significant (pphytoplankton groups known to lead to contrasting food chain at a spatial and temporal resolution unachievable when relying solely on in-situ observations.

  5. Effects of UV radiation on phytoplankton

    Science.gov (United States)

    Smith, Raymond C.; Cullen, John J.

    1995-07-01

    et al., 1986; Worrest, 1986; NOAA, 1987; Smith, 1989; Smith and Baker, 1989; Voytek, 1990; Häder, 1993; Acevedo and Nolan, 1993; Holm-Hansen et al., 1993; Vincent and Roy, 1993; Biggs and Joyner, 1994; Williamson and Zagarese, 1994; Karentz, 1994; Cullen and Neale, 1993; Cullen and Neale, 1994]. As Hader et al. have summarized [UNEP, 1989; UNEP, 1991], "UV-B radiation in aquatic systems: 1) affects adaptive strategies (e.g., motility, orientation); 2) impairs important physiological functions (e.g., photosynthesis and enzymatic reactions); and 3) threatens marine organisms during their developmental stages (e.g., the young of finfish, shrimp larvae, crab larvae)". Possible consequences to aquatic systems include: reduced biomass production; changes in species composition and biodiversity; and alterations of aquatic ecosystems and biogeochemical cycles associated with the above changes. Within the past four years, our knowledge with respect to the environmental effects of ozone-related increased levels of UV-B has increased significantly, and numerous efforts have been directed toward process-oriented studies of UV responses in plants and animals. Consensus is building toward the view that current levels of UV play a major role as an ecological determinant, influencing both survival and distribution, and are thus deserving of increased study independent of ozone-related UV-B increases. This review outlines U.S. research subsequent to 1991 and emphasizes studies concerned with phytoplankton.

  6. The dynamics of temperature and light on the growth of phytoplankton.

    Science.gov (United States)

    Chen, Ming; Fan, Meng; Liu, Rui; Wang, Xiaoyu; Yuan, Xing; Zhu, Huaiping

    2015-11-21

    Motivated by some lab and field observations of the hump shaped effects of water temperature and light on the growth of phytoplankton, a bottom-up nutrient phytoplankton model, which incorporates the combined effects of temperature and light, is proposed and analyzed to explore the dynamics of phytoplankton bloom. The population growth model reasonably captures such observed dynamics qualitatively. An ecological reproductive index is defined to characterize the growth of the phytoplankton which also allows a comprehensive analysis of the role of temperature and light on the growth and reproductive characteristics of phytoplankton in general. The model provides a framework to study the mechanisms of phytoplankton dynamics in shallow lake and may even be employed to study the controlled phytoplankton bloom. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Simulated ocean acidification reveals winners and losers in coastal phytoplankton.

    Directory of Open Access Journals (Sweden)

    Lennart T Bach

    Full Text Available The oceans absorb ~25% of the annual anthropogenic CO2 emissions. This causes a shift in the marine carbonate chemistry termed ocean acidification (OA. OA is expected to influence metabolic processes in phytoplankton species but it is unclear how the combination of individual physiological changes alters the structure of entire phytoplankton communities. To investigate this, we deployed ten pelagic mesocosms (volume ~50 m3 for 113 days at the west coast of Sweden and simulated OA (pCO2 = 760 μatm in five of them while the other five served as controls (380 μatm. We found: (1 Bulk chlorophyll a concentration and 10 out of 16 investigated phytoplankton groups were significantly and mostly positively affected by elevated CO2 concentrations. However, CO2 effects on abundance or biomass were generally subtle and present only during certain succession stages. (2 Some of the CO2-affected phytoplankton groups seemed to respond directly to altered carbonate chemistry (e.g. diatoms while others (e.g. Synechococcus were more likely to be indirectly affected through CO2 sensitive competitors or grazers. (3 Picoeukaryotic phytoplankton (0.2-2 μm showed the clearest and relatively strong positive CO2 responses during several succession stages. We attribute this not only to a CO2 fertilization of their photosynthetic apparatus but also to an increased nutrient competitiveness under acidified (i.e. low pH conditions. The stimulating influence of high CO2/low pH on picoeukaryote abundance observed in this experiment is strikingly consistent with results from previous studies, suggesting that picoeukaryotes are among the winners in a future ocean.

  8. Simulated ocean acidification reveals winners and losers in coastal phytoplankton.

    Science.gov (United States)

    Bach, Lennart T; Alvarez-Fernandez, Santiago; Hornick, Thomas; Stuhr, Annegret; Riebesell, Ulf

    2017-01-01

    The oceans absorb ~25% of the annual anthropogenic CO2 emissions. This causes a shift in the marine carbonate chemistry termed ocean acidification (OA). OA is expected to influence metabolic processes in phytoplankton species but it is unclear how the combination of individual physiological changes alters the structure of entire phytoplankton communities. To investigate this, we deployed ten pelagic mesocosms (volume ~50 m3) for 113 days at the west coast of Sweden and simulated OA (pCO2 = 760 μatm) in five of them while the other five served as controls (380 μatm). We found: (1) Bulk chlorophyll a concentration and 10 out of 16 investigated phytoplankton groups were significantly and mostly positively affected by elevated CO2 concentrations. However, CO2 effects on abundance or biomass were generally subtle and present only during certain succession stages. (2) Some of the CO2-affected phytoplankton groups seemed to respond directly to altered carbonate chemistry (e.g. diatoms) while others (e.g. Synechococcus) were more likely to be indirectly affected through CO2 sensitive competitors or grazers. (3) Picoeukaryotic phytoplankton (0.2-2 μm) showed the clearest and relatively strong positive CO2 responses during several succession stages. We attribute this not only to a CO2 fertilization of their photosynthetic apparatus but also to an increased nutrient competitiveness under acidified (i.e. low pH) conditions. The stimulating influence of high CO2/low pH on picoeukaryote abundance observed in this experiment is strikingly consistent with results from previous studies, suggesting that picoeukaryotes are among the winners in a future ocean.

  9. Simulated ocean acidification reveals winners and losers in coastal phytoplankton

    Science.gov (United States)

    Alvarez-Fernandez, Santiago; Hornick, Thomas; Stuhr, Annegret; Riebesell, Ulf

    2017-01-01

    The oceans absorb ~25% of the annual anthropogenic CO2 emissions. This causes a shift in the marine carbonate chemistry termed ocean acidification (OA). OA is expected to influence metabolic processes in phytoplankton species but it is unclear how the combination of individual physiological changes alters the structure of entire phytoplankton communities. To investigate this, we deployed ten pelagic mesocosms (volume ~50 m3) for 113 days at the west coast of Sweden and simulated OA (pCO2 = 760 μatm) in five of them while the other five served as controls (380 μatm). We found: (1) Bulk chlorophyll a concentration and 10 out of 16 investigated phytoplankton groups were significantly and mostly positively affected by elevated CO2 concentrations. However, CO2 effects on abundance or biomass were generally subtle and present only during certain succession stages. (2) Some of the CO2-affected phytoplankton groups seemed to respond directly to altered carbonate chemistry (e.g. diatoms) while others (e.g. Synechococcus) were more likely to be indirectly affected through CO2 sensitive competitors or grazers. (3) Picoeukaryotic phytoplankton (0.2–2 μm) showed the clearest and relatively strong positive CO2 responses during several succession stages. We attribute this not only to a CO2 fertilization of their photosynthetic apparatus but also to an increased nutrient competitiveness under acidified (i.e. low pH) conditions. The stimulating influence of high CO2/low pH on picoeukaryote abundance observed in this experiment is strikingly consistent with results from previous studies, suggesting that picoeukaryotes are among the winners in a future ocean. PMID:29190760

  10. Modelling the production of dimethylsulfide during a phytoplankton bloom

    Science.gov (United States)

    Gabric, Albert; Murray, Nicholas; Stone, Lewi; Kohl, Manfred

    1993-12-01

    Dimethylsulfide (DMS) is an important sulfur-containing atmospheric trace gas of marine biogenic origin. DMS emitted from the oceans may be a precursor of tropospheric aerosols and cloud condensation nuclei (CCN), thereby affecting the Earth's radiative balance and possibly constituting a negative feedback to global warming, although this hypothesis is still somewhat controversial. The revised conceptual model of the marine pelagic food web gives a central role to planktonic bacteria. Recent experiments have shown that consumption of dissolved DMS by microbial metabolism may be more important than atmospheric exchange in controlling its concentration in surface waters and hence its ventilation to the atmosphere. In this paper we investigate the effect of the marine food web on cycling of dissolved DMS in surface waters during a phytoplankton bloom episode. A nitrogen-based flow network simulation model has been used to analyze the relative importance of the various biological and chemical processes involved. The model predictions suggest that the concentration of DMS in marine surface waters is indeed governed by bacterial metabolism. Environmental factors that affect the bacterial compartment are thus likely to have a relatively large influence on dissolved DMS concentrations. The ecological succession is particularly sensitive to the ratio of phytoplankton to bacterial nutrient uptake rates as well the interaction between herbivore food chain and the microbial loop. Importantly for the design of field studies, the model predicts that peak DMS concentrations are achieved during the decline of the phytoplankton bloom with a typical time lag between peak DMS and peak phytoplankton biomass of 1 to 2 days. Significantly, the model predicts a relatively high DMS concentration persisting after the phytoplankton bloom due to excretion from large protozoa and zooplankton, which may be an additional explanation for the lack of correlation between DMS and chlorophyll a

  11. Dose-effect Curve for X-radiation in Lymphocytes in Goats

    International Nuclear Information System (INIS)

    Hasanbasic, D.; Saracevic, L.; Sacirbegovic, A.

    1998-01-01

    Dose-effect curve for X-radiation was made based on the analysis of chromosome aberrations in lympocytes of goats. Blood samples from seven goats were irradiated using MOORHEAD method, slightly modified and adapted to our conditions. Linear-square model was used, and the dose-effect curves were fitted by the smallest squares method. Dose-effect curve (collective) for goats is displayed as the following expression: y(D)= 8,6639·10 -3 D + 2,9748·10 -2 D 2 +2,9475·10 -3 . Comparison with some domestic animals such as sheep and pigs showed differences not only with respect to linear-square model, but to other mathematical presentations as well. (author)

  12. Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

    NARCIS (Netherlands)

    Alderkamp, A.C.; Mills, M.M.; van Dijken, G.L.; Laan, P.; Thuróczy, C.-E.; Gerringa, L.J.A.; de Baar, H.J.W.; Payne, C.D.; Visser, R.J.W.; Buma, A.G.J.; Arrigo, K.R.

    2012-01-01

    The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted

  13. Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu

    Directory of Open Access Journals (Sweden)

    Liangliang Shi

    2017-05-01

    Full Text Available Light absorption by phytoplankton, non-algal particles (NAP and chromophoric dissolved organic matter (CDOM was investigated at 90 sites of a clear, deep artificial lake (Lake Qiandaohu to study natural variability of absorption coefficients. Our study shows that CDOM absorption is a major contributor to the total absorption signal in Lake Qiandaohu during all seasons, except autumn when it has an equivalent contribution as total particle absorption. The exponential slope of CDOM absorption varies within a narrow range around a mean value of 0.0164 nm−1 ( s d = 0.00176 nm−1. Our study finds some evidence for thIS autochthonous production of CDOM in winter and spring. Absorption by phytoplankton, and therefore its contribution to total absorption, is generally greatest in spring, suggesting that phytoplankton growth in Lake Qiandaohu occurs predominantly in the spring. Phytoplankton absorption in freshwater lakes generally has a direct relationship with chlorophyll-a concentration, similar to the one established for open ocean waters. The NAP absorption, whose relative contribution to total absorption is highest in summer, has a spectral shape that can be well fitted by an exponential function with an average slope of 0.0065 nm−1 ( s d = 0.00076 nm−1. There is significant spatial variability present in the summer of Lake Qiandaohu, especially in the northwestern and southwestern extremes where the optical properties of the water column are strongly affected by the presence of allochthonous matter. Variations in the properties of the particle absorption spectra with depths provides evidence that the water column was vertically inhomogeneous and can be monitored with an optical measurement program. Moreover, the optical inhomogeneity in winter is less obvious. Our study will support the parameterization of the Bio-optical model for Lake Qiandaohu from in situ or remotely sensing aquatic color signals.

  14. An experimental study on total dose effects in SRAM-based FPGAs

    International Nuclear Information System (INIS)

    Yao Zhibin; He Baoping; Zhang Fengqi; Guo Hongxia; Luo Yinhong; Wang Yuanming; Zhang Keying

    2009-01-01

    In order to study testing methods and find sensitive parameters in total dose effects on SRAM-based FPGA, XC2S100 chips were irradiated by 60 Co γ-rays and tested with two test circuit designs. By analyzing the experimental results, the test flow of configuration RAM and bock RAM was given, and the most sensitive parameter was obtained. The results will be a solid foundation for establishing test specification and evaluation methods of total dose effects on SRAM-based FPGAs. (authors)

  15. COMPARING BEHAVIORAL DOSE-EFFECT CURVES FOR HUMANS AND LABORATORY ANIMALS ACUTELY EXPOSED TO TOLUENE.

    Science.gov (United States)

    The utility of laboratory animal data in toxicology depends upon the ability to generalize the results quantitatively to humans. To compare the acute behavioral effects of inhaled toluene in humans to those in animals, dose-effect curves were fitted by meta-analysis of published...

  16. Patient-reported urinary incontinence after radiotherapy for prostate cancer: Quantifying the dose-effect.

    Science.gov (United States)

    Cozzarini, Cesare; Rancati, Tiziana; Palorini, Federica; Avuzzi, Barbara; Garibaldi, Elisabetta; Balestrini, Damiano; Cante, Domenico; Munoz, Fernando; Franco, Pierfrancesco; Girelli, Giuseppe; Sini, Carla; Vavassori, Vittorio; Valdagni, Riccardo; Fiorino, Claudio

    2017-10-01

    Urinary incontinence following radiotherapy (RT) for prostate cancer (PCa) has a relevant impact on patient's quality of life. The aim of the study was to assess the unknown dose-effect relationship for late patient-reported urinary incontinence (LPRUI). Patients were enrolled within the multi-centric study DUE01. Clinical and dosimetry data including the prescribed 2Gy equivalent dose (EQD2) were prospectively collected. LPRUI was evaluated through the ICIQ-SF questionnaire filled in by the patients at RT start/end and therefore every 6months. Patients were treated with conventional (74-80Gy, 1.8-2Gy/fr) or moderately hypo-fractionated RT (65-75.2Gy, 2.2-2.7Gy/fr) in 5 fractions/week with intensity-modulated radiotherapy. Six different end-points of 3-year LPRUI, including or not patient's perception (respectively, subjective and objective end-points), were considered. Multivariable logistic models were developed for each end-point. Data of 298 patients were analyzed. The incidence of the most severe end-point (ICIQ-SF>12) was 5.1%. EQD2 calculated with alpha-beta=0.8Gy showed the best performance in fitting data: the risk of LPRUI markedly increased for EQD2>80Gy. Previous abdominal/pelvic surgery and previous TURP were the clinical factors more significantly predictive of LPRUI. Models showed excellent performances in terms of goodness-of-fit and calibration, confirmed by bootstrap-based internal validation. When included in the analyses, baseline symptoms were a major predictor for 5 out of six end-points. LPRUI after RT for PCa dramatically depends on EQD2 and few clinical factors. Results are consistent with a larger than expected impact of moderate hypo-fractionation on the risk of LPRUI. As expected, baseline symptoms, as captured by ICIQ-SF, are associated to an increased risk of LPRUI. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Estrutura e dinâmica da comunidade fitoplanctônica e sua relação com as variáveis ambientais na lagoa Mãe-Bá, Estado do Espírito Santo, Brasil - DOI: 10.4025/actascibiolsci.v31i3.1266 Structure and dynamics of the phytoplankton community and its relationship with environmental variables at the Mãe-Bá lagoon, Espírito Santo State, Brazil - DOI: 10.4025/actascibiolsci.v31i3.1266

    Directory of Open Access Journals (Sweden)

    Valéria Oliveira Fernandes

    2009-07-01

    Full Text Available O presente estudo objetivou avaliar a estrutura e dinâmica da comunidade fitoplanctônica e sua relação com as variáveis ambientais na lagoa Mãe-Bá. Foram realizadas quatro amostragens com periodicidade quinzenal, abrangendo as estações seca e chuvosa, na região limnética de dois pontos de amostragem submetidos a diferentes condições ambientais. O fitoplâncton foi analisado quanto à riqueza, densidade total, abundância, dominância, diversidade e equitabilidade. Foram determinados: temperatura (ar/água, transparência, zona eufótica, profundidade, pH, oxigênio dissolvido, turbidez, condutividade elétrica, sólidos totais dissolvidos e suspensos, concentrações de nutrientes. Foram registrados 138 táxons, sendo a Classe Cyanophyceae mais representativa em termos qualitativos e quantitativos. A densidade total do fitoplâncton foi elevada, apresentando maiores valores na estação seca e no Ponto 1, considerado mais impactado. A ausência de dominância e a abundância de poucas espécies explicaram os valores de diversidade e equitabilidade. A lagoa Mãe-Bá se caracterizou como um ambiente raso, com águas levemente ácidas a alcalinas, elevados valores de temperatura, oxigênio dissolvido, zona eufótica e transparência e baixas concentrações de nutrientes. A estrutura da comunidade fitoplanctônica foi influenciada principalmente pela precipitação, transparência e temperatura da água, sendo possivelmente limitada por nitrato e nitrogênio amoniacal no ambiente estudado.The present study aimed to evaluate the structure and dynamics of the phytoplankton community and its relationship with environmental variables at the Mãe-Bá lagoon. Four samples were taken fortnightly during the rainy and dry seasons, in the limnetic zone of two sampling sites, subjected to different environmental conditions. Richness, total density, abundance, dominance, diversity and equitability of phytoplankton were analyzed. The environmental

  18. Thermal ecology of phytoplankton in a desert reservoir

    International Nuclear Information System (INIS)

    Olsen, R.D.; Sommerfeld, M.R.

    1976-01-01

    The physical--chemical limnology and phytoplankton dynamics of Canyon Lake, Arizona, were investigated from February 1971 to July 1973. The reservoir is a warm monomictic lake with pronounced thermal stratification during the summer months. Chemically the lake is hard water of moderate to high alkalinity and salinity. Annual peaks in the phytoplankton standing crop were recorded during early spring and mid- to late summer, and significant depressions occurred during April--May and November to January. The spring peak was composed primarily of centric diatoms, whereas the summer peak was dominated by filamentous Cyanophyceae. The seasonal appearance and variation in population size of individual species were correlated in varying degrees with one or more physical--chemical parameters. Indications are that physical factors (particularly light and water temperature), rather than water chemistry, were the primary parameters regulating seasonal succession

  19. Macroecological patterns in the distribution of marine phytoplankton

    DEFF Research Database (Denmark)

    Mousing, Erik Askov

    stratification limiting the flux of nutrients from the deep ocean). This affect has important implications for the global carbon cycle and should be included in future climate models. In manuscript II, changes in the mean cyst size of dinoflagellates are investigated in relation to temperature changes during...... production, biochemical cycling and have a direct impact on the global carbon cycle through the biological pump. Understanding the processes controlling phytoplankton primary production and community composition at the global scale and how these interact with climate change are, therefore, imperative...... to in situ abiotic conditions (primarily temperature, salinity, mixed layer dynamics and ambient nutrient concentrations) in order to elucidate the primary bottom-up processes that control phytoplankton communities. In order to do this, I investigate and present several data sets that have been assembled...

  20. Acid rain stimulation of Lake Michigan phytoplankton growth

    Science.gov (United States)

    Manny, Bruce A.; Fahnenstiel, G.L.; Gardner, W.S.

    1987-01-01

    Three laboratory experiments demonstrated that additions of rainwater to epilimnetic lake water collected in southeastern Lake Michigan stimulated chlorophyll a production more than did additions of reagent-grade water during incubations of 12 to 20 d. Chlorophyll a production did not begin until 3–5 d after the rain and lake water were mixed. The stimulation caused by additions of rain acidified to pH 3.0 was greater than that caused by additions of untreated rain (pH 4.0–4.5). Our results support the following hypotheses: (1) Acid rain stimulates the growth of phytoplankton in lake water; (2) phosphorus in rain appears to be the factor causing this stimulation. We conclude that acid rain may accelerate the growth of epilimnetic phytoplankton in Lake Michigan (and other similar lakes) during stratification when other sources of bioavailable phosphorus to the epilimnion are limited

  1. PHYTOPLANKTON AND BIOMASS DISTRIBUTION AT POTENTIAL OTEC SITES

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, P.W.; Horne, A.J.

    1979-06-01

    Net or large phytoplankton species composition and most phytoplankton abundance was measured at three OTEC sites. In the Gulf of Mexico and Hawaii, diatoms dominated while the blue-green algae Trichodesmium was most common at Puerto Rico. The species ratio of diatoms to dinoflagellates was approximately 1:1. The species diversity varied from site to site, Hawaii > Puerto Rico > Gulf of Mexico. Chlorophyll a, which is a measure of the pigment of all algae size ranges, showed a subsurface peak of 0.14-0.4 g per liter at 75 to 125 m. Occasional surface peaks up to 0.4 pg per liter occurred. Further refinement of collection techniques is needed to delineate the subtle environmental effects expected by OTEC plant discharges.

  2. Phytoplankton growth, dissipation, and succession in estuarine environments. [Chesapeake Bay

    Energy Technology Data Exchange (ETDEWEB)

    Seliger, H H

    1976-01-01

    Two major advances in a study of phytoplankton ecology in the Chesapeake Bay are reported. The annual subsurface transport of a dinoflagellate species (Prorocentrum mariae labouriae) from the mouth of the bay a distance northward of 120 nautical miles to the region of the Bay Bridge was followed. Prorocentrum is a major seasonal dinoflagellate in the Chespeake Bay and annually has been reported to form mahogany tides, dense reddish-brown patches, in the northern bay beginning in late spring and continuing through the summer. Subsequent to this annual appearance the Prorocentrum spread southward and into the western tributary estuaries. The physiological behavioral characteristics of the Prorocentrum were correlated with the physical water movements in the bay. A phytoplankton cage technique for the measurement in situ of the growth rates of natural mixed populations is described. (CH)

  3. Phytoplankton and biomass distribution at potential OTEC sites

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, P.W.; Horne, A.J.

    1979-06-01

    Net or large phytoplankton species composition and most phytoplankton abundance was measured at three OTEC sites. In the Gulf of Mexico and'Hawaii, diatoms dominated while the blue-green algae Trichodesmium was most common at Puerto Rico. The species ratio of diatoms to dinoflagellates was approximately 1:1. The species diversity varied from site to site, Hawaii > Puerto Rico > Gulf of Mexico. Chlorophyll a, which is a measure of the pigment of all algae size ranges, showed a subsurface peak of 0.14 to 0.4 g per liter at 75 to 125 m. Occasional surface peaks upto 0.4 ..mu..g per liter occurred. Further refinement of collection techniques is needed to delineate the subtle environmental effects expected by OTEC plant discharges.

  4. Reduced river discharge intensifies phytoplankton bloom in Godavari estuary, India

    Digital Repository Service at National Institute of Oceanography (India)

    Acharyya, T.; Sarma, V.V.S.S.; Sridevi, B.; Venkataramana, V.; Bharathi, M.D.; Naidu, S.A.; Kumar, B.S.K.; Prasad, V.R.; Bandyopadhyay, D.; Reddy, N.P.C.; DileepKumar, M.

    et al., 2009; Sarma et al., 2011), behaviour of different 3 elements (Sarma et al., 1993) and heavy metals (Somayajulu et al., 1993).Virtually no systematic studies have been undertaken so far in these estuaries focussing on spatial and... their class specific marker pigment fucoxanthin (Jeffry et al., 1997; Mantoura and Llewellyn, 1983; Wright et al., 1991). To confirm the influence of SPM and flushing time on phytoplankton bloom a laboratory- based incubation experiment was conducted...

  5. Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency

    OpenAIRE

    Taipale, Sami J.; Galloway, Aaron W. E.; Aalto, Sanni L.; Kahilainen, Kimmo K.; Strandberg, Ursula; Kankaala, Paula

    2016-01-01

    Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terr...

  6. Under Sea Ice phytoplankton bloom detection and contamination in Antarctica

    Science.gov (United States)

    Zeng, C.; Zeng, T.; Xu, H.

    2017-12-01

    Previous researches reported compelling sea ice phytoplankton bloom in Arctic, while seldom reports studied about Antarctic. Here, lab experiment showed sea ice increased the visible light albedo of the water leaving radiance. Even a new formed sea ice of 10cm thickness increased water leaving radiance up to 4 times of its original bare water. Given that phytoplankton preferred growing and accumulating under the sea ice with thickness of 10cm-1m, our results showed that the changing rate of OC4 estimated [Chl-a] varied from 0.01-0.5mg/m3 to 0.2-0.3mg/m3, if the water covered by 10cm sea ice. Going further, varying thickness of sea ice modulated the changing rate of estimating [Chl-a] non-linearly, thus current routine OC4 model cannot estimate under sea ice [Chl-a] appropriately. Besides, marginal sea ice zone has a large amount of mixture regions containing sea ice, water and snow, where is favorable for phytoplankton. We applied 6S model to estimate the sea ice/snow contamination on sub-pixel water leaving radiance of 4.25km spatial resolution ocean color products. Results showed that sea ice/snow scale effectiveness overestimated [Chl-a] concentration based on routine band ratio OC4 model, which contamination increased with the rising fraction of sea ice/snow within one pixel. Finally, we analyzed the under sea ice bloom in Antarctica based on the [Chl-a] concentration trends during 21 days after sea ice retreating. Regardless of those overestimation caused by sea ice/snow sub scale contamination, we still did not see significant under sea ice blooms in Antarctica in 2012-2017 compared with Arctic. This research found that Southern Ocean is not favorable for under sea ice blooms and the phytoplankton bloom preferred to occur in at least 3 weeks after sea ice retreating.

  7. Comparison of Machine Learning Techniques in Inferring Phytoplankton Size Classes

    Directory of Open Access Journals (Sweden)

    Shuibo Hu

    2018-03-01

    Full Text Available The size of phytoplankton not only influences its physiology, metabolic rates and marine food web, but also serves as an indicator of phytoplankton functional roles in ecological and biogeochemical processes. Therefore, some algorithms have been developed to infer the synoptic distribution of phytoplankton cell size, denoted as phytoplankton size classes (PSCs, in surface ocean waters, by the means of remotely sensed variables. This study, using the NASA bio-Optical Marine Algorithm Data set (NOMAD high performance liquid chromatography (HPLC database, and satellite match-ups, aimed to compare the effectiveness of modeling techniques, including partial least square (PLS, artificial neural networks (ANN, support vector machine (SVM and random forests (RF, and feature selection techniques, including genetic algorithm (GA, successive projection algorithm (SPA and recursive feature elimination based on support vector machine (SVM-RFE, for inferring PSCs from remote sensing data. Results showed that: (1 SVM-RFE worked better in selecting sensitive features; (2 RF performed better than PLS, ANN and SVM in calibrating PSCs retrieval models; (3 machine learning techniques produced better performance than the chlorophyll-a based three-component method; (4 sea surface temperature, wind stress, and spectral curvature derived from the remote sensing reflectance at 490, 510, and 555 nm were among the most sensitive features to PSCs; and (5 the combination of SVM-RFE feature selection techniques and random forests regression was recommended for inferring PSCs. This study demonstrated the effectiveness of machine learning techniques in selecting sensitive features and calibrating models for PSCs estimations with remote sensing.

  8. Hydro-environmental factors and phytoplankton of the Atlantic ...

    African Journals Online (AJOL)

    Hydro-environmental factors and phytoplankton of the Atlantic Ocean, off the Light House Beach, Lagos, Nigeria. ... (28.37±1.88), pH (7.85±0.17), conductivity (44738.75±6262.76 μS/cm), total dissolved solids (29236.71±4273.30 mg/L), salinity (27.11±3.91 ‰), alkalinity (126.99±42.81 mg/L) and chloride (15056.

  9. A stochastic analysis for a phytoplankton-zooplankton model

    International Nuclear Information System (INIS)

    Ge, G; Wang, H-L; Xu, J

    2008-01-01

    A simple phytoplankton-zooplankton nonlinear dynamical model was proposed to study the coexistence of all the species and a Hopf bifurcation was observed. In order to study the effect of environmental robustness on this system, we have stochastically perturbed the system with respect to white noise around its positive interior equilibrium. We have observed that the system remains stochastically stable around the positive equilibrium for same parametric values in the deterministic situation

  10. QUALITATIVE COMPOSITION OF PHYTOPLANKTONS IN DIFFERENTLY MANURED CARP PONDS

    Directory of Open Access Journals (Sweden)

    Ljubica Debeljak

    1997-04-01

    Full Text Available Researches on qualitative composition of phytoplanktons in differently manured fish-ponds "Jelas" were carried out in 1996. The carp fingerling from larve to its second month was nurtured in three fish-ponds (A,B,C with the plantation of larves of 1,000,000 ind.ha-1. Larves and carp fry were nurtured by trouvit and wheat flour. The fish-pond A was controlled but not manured; the fish-pond B was fertilized by the total of 200 kg.ha-1 NPK (15:15:15 and the fish-pond C was fertilized by the total of 75 l.ha-1 of UAN and 75 kg.l-1 of NP (12:52. All fish-ponds had similar water chemism. In the qualitative composition of phytoplanktons there were stated 93 kinds, members of systematic groups Cyanophyta (10%, Euglenophyta (16.2%, Pyrrophyta (2%, Chrysophyta (39.4% and Chlorophyta (32%. All fish-ponds had similar qualitative composition of phytoplanktons with the flora similarity quotient from 65.5% to 72%.

  11. Bacterial and protist community changes during a phytoplankton bloom

    KAUST Repository

    Pearman, John K.

    2015-10-01

    The present study aims to characterize the change in the composition and structure of the bacterial and microzooplankton planktonic communities in relation to the phytoplankton community composition during a bloom. High-throughput amplicon sequencing of regions of the 16S and 18S rRNA gene was undertaken on samples collected during a 20 day (d) mesocosm experiment incorporating two different nutrient addition treatments [Nitrate and Phosphate (NPc) and Nitrate, Phosphate and Silicate (NPSc)] as well as a control. This approach allowed us to discriminate the changes in species composition across a broad range of phylogenetic groups using a common taxonomic level. Diatoms dominated the bloom in the NPSc treatment while dinoflagellates were the dominant phytoplankton in the control and NPc treatment. Network correlations highlighted significant interactions between OTUs within each treatment including changes in the composition of Paraphysomonas OTUs when the dominant Chaetoceros OTU switched. The microzooplankton community composition responded to changes in the phytoplankton composition while the prokaryotic community responded more to changes in ammonia concentration.

  12. Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency.

    Science.gov (United States)

    Taipale, Sami J; Galloway, Aaron W E; Aalto, Sanni L; Kahilainen, Kimmo K; Strandberg, Ursula; Kankaala, Paula

    2016-08-11

    Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terrestrial-origin carbohydrates for energy and sparing essential fatty acids and amino acids for somatic growth and reproduction. Assimilated terrestrial-origin fatty acids from shoreline reed particles exceeded available diet, indicating that Daphnia may convert a part of their dietary carbohydrates to saturated fatty acids. This conversion was not observed with birch leaf diets, which had lower carbohydrate content. Subsequent analysis of 21 boreal and subarctic lakes showed that diet of herbivorous zooplankton is mainly based on high-quality phytoplankton rich in essential polyunsaturated fatty acids. The proportion of low-quality diets (bacteria and terrestrial particulate organic matter) was <28% of the assimilated carbon. Taken collectively, the incorporation of terrestrial carbon into zooplankton was not directly related to the concentration of terrestrial organic matter in experiments or lakes, but rather to the low availability of phytoplankton.

  13. Distribution of phytoplankton groups within the deep chlorophyll maximum

    KAUST Repository

    Latasa, Mikel

    2016-11-01

    The fine vertical distribution of phytoplankton groups within the deep chlorophyll maximum (DCM) was studied in the NE Atlantic during summer stratification. A simple but unconventional sampling strategy allowed examining the vertical structure with ca. 2 m resolution. The distribution of Prochlorococcus, Synechococcus, chlorophytes, pelagophytes, small prymnesiophytes, coccolithophores, diatoms, and dinoflagellates was investigated with a combination of pigment-markers, flow cytometry and optical and FISH microscopy. All groups presented minimum abundances at the surface and a maximum in the DCM layer. The cell distribution was not vertically symmetrical around the DCM peak and cells tended to accumulate in the upper part of the DCM layer. The more symmetrical distribution of chlorophyll than cells around the DCM peak was due to the increase of pigment per cell with depth. We found a vertical alignment of phytoplankton groups within the DCM layer indicating preferences for different ecological niches in a layer with strong gradients of light and nutrients. Prochlorococcus occupied the shallowest and diatoms the deepest layers. Dinoflagellates, Synechococcus and small prymnesiophytes preferred shallow DCM layers, and coccolithophores, chlorophytes and pelagophytes showed a preference for deep layers. Cell size within groups changed with depth in a pattern related to their mean size: the cell volume of the smallest group increased the most with depth while the cell volume of the largest group decreased the most. The vertical alignment of phytoplankton groups confirms that the DCM is not a homogeneous entity and indicates groups’ preferences for different ecological niches within this layer.

  14. FLOW CYTOMETRIC APPLICABILITY OF FLUORESCENT VITALITY PROBES ON PHYTOPLANKTON1.

    Science.gov (United States)

    Peperzak, Louis; Brussaard, Corina P D

    2011-06-01

    The applicability of six fluorescent probes (four esterase probes: acetoxymethyl ester of Calcein [Calcein-AM], 5-chloromethylfluorescein diacetate [CMFDA], fluorescein diacetate [FDA], and 2',7'-dichlorofluorescein diacetate [H 2 DCFDA]; and two membrane probes: bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC 4 (3)] and SYTOX-Green) as vitality stains was tested on live and killed cells of 40 phytoplankton strains in exponential and stationary growth phases, belonging to 12 classes and consisting of four cold-water, 26 temperate, and four warm-water species. The combined live/dead ratios of all six probes indicated significant differences between the 12 plankton classes (P live/dead ratios of FDA and CMFDA were not significantly different from each other, and both performed better than Calcein-AM and H 2 DCFDA (P live/dead ratios) among all six probes belonged to nine genera from six classes of phytoplankton. In conclusion, FDA, CMFDA, DIBAC 4 (3), and SYTOX-Green represent a wide choice of vitality probes in the study of phytoplankton ecology, applicable in many species from different algal classes, originating from different regions and at different stages of growth. © 2011 Phycological Society of America.

  15. Bacterial community transcription patterns during a marine phytoplankton bloom.

    Science.gov (United States)

    Rinta-Kanto, Johanna M; Sun, Shulei; Sharma, Shalabh; Kiene, Ronald P; Moran, Mary Ann

    2012-01-01

    Bacterioplankton consume a large proportion of photosynthetically fixed carbon in the ocean and control its biogeochemical fate. We used an experimental metatranscriptomics approach to compare bacterial activities that route energy and nutrients during a phytoplankton bloom compared with non-bloom conditions. mRNAs were sequenced from duplicate bloom and control microcosms 1 day after a phytoplankton biomass peak, and transcript copies per litre of seawater were calculated using an internal mRNA standard. Transcriptome analysis revealed a potential novel mechanism for enhanced efficiency during carbon-limited growth, mediated through membrane-bound pyrophosphatases [V-type H(+)-translocating; hppA]; bloom bacterioplankton participated less in this metabolic energy scavenging than non-bloom bacterioplankton, with possible implications for differences in growth yields on organic substrates. Bloom bacterioplankton transcribed more copies of genes predicted to increase cell surface adhesiveness, mediated by changes in bacterial signalling molecules related to biofilm formation and motility; these may be important in microbial aggregate formation. Bloom bacterioplankton also transcribed more copies of genes for organic acid utilization, suggesting an increased importance of this compound class in the bioreactive organic matter released during phytoplankton blooms. Transcription patterns were surprisingly faithful within a taxon regardless of treatment, suggesting that phylogeny broadly predicts the ecological roles of bacterial groups across 'boom' and 'bust' environmental backgrounds. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  16. Benthic algae compensate for phytoplankton losses in large aquatic ecosystems.

    Science.gov (United States)

    Brothers, Soren; Vadeboncoeur, Yvonne; Sibley, Paul

    2016-12-01

    Anthropogenic activities can induce major trophic shifts in aquatic systems, yet we have an incomplete understanding of the implication of such shifts on ecosystem function and on primary production (PP) in particular. In recent decades, phytoplankton biomass and production in the Laurentian Great Lakes have declined in response to reduced nutrient concentrations and invasive mussels. However, the increases in water clarity associated with declines in phytoplankton may have positive effects on benthic PP at the ecosystem scale. Have these lakes experienced oligotrophication (a reduction of algal production), or simply a shift in autotrophic structure with no net decline in PP? Benthic contributions to ecosystem PP are rarely measured in large aquatic systems, but our calculations based on productivity rates from the Great Lakes indicate that a significant proportion (up to one half, in Lake Huron) of their whole-lake production may be benthic. The large declines (5-45%) in phytoplankton production in the Great Lakes from the 1970s to 2000s may be substantially compensated by benthic PP, which increased by up to 190%. Thus, the autotrophic productive capacity of large aquatic ecosystems may be relatively resilient to shifts in trophic status, due to a redirection of production to the near-shore benthic zone, and large lakes may exhibit shifts in autotrophic structure analogous to the regime shifts seen in shallow lakes. © 2016 John Wiley & Sons Ltd.

  17. Phytoplankton-Associated Bacterial Community Composition and Succession during Toxic Diatom Bloom and Non-Bloom Events.

    Science.gov (United States)

    Sison-Mangus, Marilou P; Jiang, Sunny; Kudela, Raphael M; Mehic, Sanjin

    2016-01-01

    Pseudo-nitzschia blooms often occur in coastal and open ocean environments, sometimes leading to the production of the neurotoxin domoic acid that can cause severe negative impacts to higher trophic levels. Increasing evidence suggests a close relationship between phytoplankton bloom and bacterial assemblages, however, the microbial composition and succession during a bloom process is unknown. Here, we investigate the bacterial assemblages before, during and after toxic and non-toxic Pseudo-nitzschia blooms to determine the patterns of bacterial succession in a natural bloom setting. Opportunistic sampling of bacterial community profiles were determined weekly at Santa Cruz Municipal Wharf by 454 pyrosequencing and analyzed together with domoic acid levels, phytoplankton community and biomass, nutrients and temperature. We asked if the bacterial communities are similar between bloom and non-bloom events and if domoic acid or the presence of toxic algal species acts as a driving force that can significantly structure phytoplankton-associated bacterial communities. We found that bacterial diversity generally increases when Pseudo-nitzschia numbers decline. Furthermore, bacterial diversity is higher when the low-DA producing P. fraudulenta dominates the algal bloom while bacterial diversity is lower when high-DA producing P. australis dominates the algal bloom, suggesting that the presence of algal toxin can structure bacterial community. We also found bloom-related succession patterns among associated bacterial groups; Gamma-proteobacteria, were dominant during low toxic P. fraudulenta blooms comprising mostly of Vibrio spp., which increased in relative abundance (6-65%) as the bloom progresses. On the other hand, Firmicutes bacteria comprising mostly of Planococcus spp. (12-86%) dominate during high toxic P. australis blooms, with the bacterial assemblage showing the same bloom-related successional patterns in three independent bloom events. Other environmental

  18. Phytoplankton-associated bacterial community composition and succession during toxic diatom bloom and non-bloom events

    Directory of Open Access Journals (Sweden)

    Marilou P. Sison-Mangus

    2016-09-01

    Full Text Available Pseudo-nitzschia blooms often occur in coastal and open ocean environments, sometimes leading to the production of the neurotoxin domoic acid that can cause severe negative impacts to higher trophic levels. Increasing evidence suggests a close relationship between phytoplankton bloom and bacterial assemblages, however, the microbial composition and succession during a bloom process is unknown. Here, we investigate the bacterial assemblages before, during and after toxic and non-toxic Pseudo-nitzschia blooms to determine the patterns of bacterial succession in a natural bloom setting. Opportunistic sampling of bacterial community profiles were determined weekly at Santa Cruz Municipal Wharf by 454 pyrosequencing and analyzed together with domoic acid levels, phytoplankton community and biomass, nutrients and temperature. We asked if the bacterial communities are similar between bloom and non-bloom events and if domoic acid or the presence of toxic algal species acts as a driving force that can significantly structure phytoplankton-associated bacterial communities. We found that bacterial diversity generally increases when Pseudo-nitzschia numbers decline. Furthermore, bacterial diversity is higher when the low-DA producing P. fraudulenta dominates the algal bloom while bacterial diversity is lower when high-DA producing P. australis dominates the algal bloom, suggesting that the presence of algal toxin can structure bacterial community. We also found bloom-related succession patterns among associated bacterial groups; Gamma-proteobacteria, were dominant during low toxic P. fraudulenta blooms comprising mostly of Vibrio spp., which increased in relative abundance (6%-65% as the bloom progresses. On the other hand, Firmicutes bacteria comprising mostly of Planococcus spp. (12%- 86% dominate during high toxic P. australis blooms, with the bacterial assemblage showing the same bloom-related successional patterns in 3 independent bloom events. Other

  19. Effects of CO2 on particle size distribution and phytoplankton abundance during a mesocosm bloom experiment (PeECE II

    Directory of Open Access Journals (Sweden)

    M. Schartau

    2008-04-01

    Full Text Available The influence of seawater carbon dioxide (CO2 concentration on the size distribution of suspended particles (2–60 μm and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS in Bergen, Norway, in the frame of the Pelagic Ecosystem CO2 Enrichment study (PeECE II. In nine outdoor enclosures the partial pressure of CO2 in seawater was modified by an aeration system to simulate past (~190 μatm CO2, present (~370 μatm CO2 and future (~700 μatm CO2 CO2 conditions in triplicates. Due to the initial addition of inorganic nutrients, phytoplankton blooms developed in all mesocosms and were monitored over a period of 19 days. Seawater samples were collected daily for analysing the abundance of suspended particles and phytoplankton with the Coulter Counter and with Flow Cytometry, respectively. During the bloom period, the abundance of small particles (2 levels. At that time, a direct relationship between the total-surface-to-total-volume ratio of suspended particles and DIC concentration was determined for all mesocosms. Significant changes with respect to the CO2 treatment were also observed in the phytoplankton community structure. While some populations such as diatoms seemed to be insensitive to the CO2 treatment, others like Micromonas spp. increased with CO2, or showed maximum abundance at present day CO2 (i.e. Emiliania huxleyi. The strongest response to CO2 was observed in the abundance of small autotrophic nano-plankton that strongly increased during the bloom in the past CO2 mesocosms. Together, changes in particle size distribution and phytoplankton community indicate a complex interplay between the ability of the cells to physiologically respond to changes in CO2 and size selection. Size of cells is of general importance for a variety of processes in marine systems such as diffusion-limited uptake of substrates, resource allocation, predator-prey interaction, and gravitational settling

  20. Bioaccumulation of tritiated water in phytoplankton and trophic transfer of organically bound tritium to the blue mussel, Mytilus edulis.

    Science.gov (United States)

    Jaeschke, Benedict C; Bradshaw, Clare

    2013-01-01

    Large releases of tritium are currently permitted in coastal areas due to assumptions that it rapidly disperses in the water and has a low toxicity due to its low energy emissions. This paper presents a laboratory experiment developed to identify previously untested scenarios where tritium may concentrate or transfer in biota relevant to Baltic coastal communities. Phytoplankton populations of Dunaliella tertiolecta and Nodularia spumigena were exposed at different growth-stages, to tritiated water (HTO; 10 MBq l(-1)). Tritiated D. tertiolecta was then fed to mussels, Mytilus edulis, regularly over a period of three weeks. Activity concentrations of phytoplankton and various tissues from the mussel were determined. Both phytoplankton species transformed HTO into organically-bound tritium (OBT) in their tissues. D. tertiolecta accumulated significantly more tritium when allowed to grow exponentially in HTO than if it had already reached the stationary growth phase; both treatments accumulated significantly more than the corresponding treatments of N. spumigena. No effect of growth phase on bioaccumulation of tritium was detectable in N. spumigena following exposure. After mussels were given 3 feeds of tritiated D. tertiolecta, significant levels of tritium were detected in the tissues. Incorporation into most mussel tissues appeared to follow a linear relationship with number of tritiated phytoplankton feeds with no equilibrium, highlighting the potential for biomagnification. Different rates of incorporation in species from a similar functional group highlight the difficulties in using a 'representative' species for modelling the transfer and impact of tritium. Accumulations of organic tritium into the mussel tissues from tritiated-phytoplankton demonstrate an environmentally relevant transfer pathway of tritium even when water-concentrations are reduced, adding weight to the assertion that organically bound tritium acts as a persistent organic pollutant. The

  1. Study of the lacustrine phytoplankton productivity dependence on solar radiation, on the basis of direct high-frequency measurements

    Science.gov (United States)

    Provenzale, Maria; Ojala, Anne; Heiskanen, Jouni; Erkkilä, Kukka-Maaria; Mammarella, Ivan; Hari, Pertti; Vesala, Timo

    2016-04-01

    One of the main components of the carbon cycle in lakes is phytoplankton. Its in situ photosynthesis and respiration are usually studied with traditional methods (dark and light bottle method, 14C labelling technique). These methods, relying on sampling and incubation, may lead to unrealistic results. They also have a poor temporal resolution, which does not allow the non-linear relationship between photosynthetically active solar radiation (PAR) and photosynthesis to be properly investigated. As a consequence, the phytoplankton net primary productivity (NPP) cannot be parameterised as a function of ambient variables. In 2008 an innovative free-water approach was proposed. It is based on non-dispersive infrared air CO2 probes that, by building an appropriate system, can be used to measure the CO2 concentration in the water at a high-frequency. At that time, the method was tested only on 3 days of data. Here, we deployed it on a boreal lake in Finland for four summers, in order to calculate the NPP and verify its dependence on PAR. The set-up was completed by an eddy-covariance system and water PAR and temperature sensors. In analogy with the procedure typically used in terrestrial ecology, we obtained the phytoplankton NPP computing the mass balance of CO2 in the mixed layer of the lake, i.e. the superficial layer where the conditions are homogeneous and most of the photosynthetic activity takes place. After calculating the NPP , we verified its dependence on PAR. The theoretical model we used was a saturating Michaelis-Menten curve, in which the variables are water temperature and PAR. The equation also contains parameters typical of the phytoplankton communities, which represent their maximum potential photosynthetic rate, their half-saturation constant and their basal respiration. These parameters allow the NPP to be parameterised as a function of T and PAR. For all the analysed year, we found a very good agreement between theory and data (R2 ranged from 0.80 to

  2. Hydrodynamic control of phytoplankton loss to the benthos in an estuarine environment

    Science.gov (United States)

    Jones, Nicole L.; Thompson, Janet K.; Arrigo, Kevin R.; Monismith, Stephen G.

    2009-01-01

    Field experiments were undertaken to measure the influence of hydrodynamics on the removal of phytoplankton by benthic grazers in Suisun Slough, North San Francisco Bay. Chlorophyll a concentration boundary layers were found over beds inhabited by the active suspension feeders Corbula amurensis and Corophium alienense and the passive suspension feeders Marenzellaria viridis and Laonome sp. Benthic losses of phytoplankton were estimated via both the control volume and the vertical flux approach, in which chlorophyll a concentration was used as a proxy for phytoplankton biomass. The rate of phytoplankton loss to the bed was positively correlated to the bed shear stress. The maximum rate of phytoplankton loss to the bed was five times larger than estimated by laboratory-derived pumping rates for the active suspension feeders. Reasons for this discrepancy are explored including a physical mechanism whereby phytoplankton is entrained in a near-bed fluff layer where aggregation is mediated by the presence of mucus produced by the infaunal community.

  3. Phytoplankton response to winter warming modified by large-bodied zooplankton: an experimental microcosm study

    Directory of Open Access Journals (Sweden)

    Hu He

    2015-03-01

    Full Text Available While several field investigations have demonstrated significant effects of cool season (winter or spring warming on phytoplankton development, the role played by large-bodied zooplankton grazers for the responses of phytoplankton to winter warming is ambiguous. We conducted an outdoor experiment to compare the effect of winter warming (heating by 3°C in combination with presence and absence of Daphnia grazing (D. similis on phytoplankton standing crops and community structure under eutrophic conditions. When Daphnia were absent, warming was associated with significant increases in phytoplankton biomass and cyanobacterial dominance. In contrast, when Daphnia were present, warming effects on phytoplankton dynamics were offset by warming-enhanced grazing, resulting in no significant change in biomass or taxonomic dominance. These results emphasize that large-bodied zooplankton like Daphnia spp. may play an important role in modulating the interactions between climate warming and phytoplankton dynamics in nutrient rich lake ecosystems.

  4. Development of phytoplankton communities: Implications of nutrient injections on phytoplankton composition, pH and ecosystem production

    DEFF Research Database (Denmark)

    Jakobsen, Hans; Blanda, Elisa; Stæhr, Peter Anton

    2015-01-01

    The development of a marine phytoplankton community was studied in a series of mesocosm tanks exposed to different levels of nutrient inputs. Key ecosystem variables such as phytoplankton species development, ecosystem net production (NEP), pH and bacteria production were measured. The overall aim...... was to mimic the consequences of extreme weather events by applying nutrients in either repeated (pulse treatment) versus a single inputs (full treatment). Regardless of treatment type, pH increased steadily, until nutrients became exhausted. During the experiment, potentially nuisance dinoflagellates...... developed and became dominant whereas diatoms became rare as compared to the parallel controls. At pH > 9, a shift from the presence of the potential nuisance Alexandrium pseudogonyaulax towards high pH tolerant Prorocentrum species was observed. Diatoms disappeared when A. pseudogonyaulax became dominant...

  5. Net phytoplankton of the Admiralty Bay (King George Island, South Shetland Islands) in 1983

    OpenAIRE

    Ligowski, Ryszard

    1986-01-01

    Paper received 13 July 1985. Phytoplankton sampling from 13 stations situated in Admiralty Bay was carried out in March. April, May, October and November 1983. Wet settling volume of seston, its dry weight, number of cells under 1 m², and qualitative composition of phytoplankton were determined. It was found that amount of phytoplankton was decreasing in April and increasing again in November after the winter season. The share of benthic and periphyton species in the qualita...

  6. Interannual Variation in Phytoplankton Primary Production at a Global Scale

    Science.gov (United States)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2013-01-01

    We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of four phytoplankton groups to the total primary production. First, we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998-2011. Globally, diatoms contributed the most to the total phytoplankton production ((is)approximately 50%, the equivalent of 20 PgC·y1). Coccolithophores and chlorophytes each contributed approximately 20% ((is) approximately 7 PgC·y1) of the total primary production and cyanobacteria represented about 10% ((is) approximately 4 PgC·y1) of the total primary production. Primary production by diatoms was highest in the high latitudes ((is) greater than 40 deg) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998-2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4% (1-2 PgC·y1). We assessed the effects of climate variability on group-specific primary production using global (i.e., Multivariate El Niño Index, MEI) and "regional" climate indices (e.g., Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p (is) less than 0.05) between the MEI and the group-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatoms/cyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect

  7. Scattering of phytoplankton cells from cytometry during a microcosm experiment

    Science.gov (United States)

    Moutier, W.; Duforêt-Gaurier, L.; Loisel, H.; Thyssen, M.; Mériaux, X.; Desailly, D.; Courcot, L.; Dugenne, M.

    2016-02-01

    This study presents an application of the CytoSense flow cytometer (CytoBuoy b.v., NL) as a powerful tool to analyze optical properties of phytoplankton cells. Recently, Duforêt et al., (2015) developed a methodology to derive the forward, sideward and backward cross section (σFWS, σSWS and σbb, respectively) of individual particles from the CytoSense. For the first time, this methodology was applied to phytoplankton cultures. A 20 day microcosm experiment was conducted on two phytoplankton species (Chlamydomonas concordia and Thalassiosira pseudonana). We realized daily sampling for biogeochemical and flow cytometer analysis and carried out optical measurements. Scanning electron migrographs (SEM) were performed at different life stages to investigate the cells morphology.First, CytoSense estimates were tested against radiative transfer computations. The comparison exercise, is based on radiative transfer simulations because for phytoplankton cultures, in situ measurements of σFWS and σSWS, particle by particle, are not available in literature. For that purpose, we build a database of 590,000 simulations, considering homogeneous and multi-layered spheres, to represent the optical properties of a large diversity of phytoplankton cells. Comparison showed that the CytoSense estimates for the cultures are consistent with values predicted by the theory. Second, the flow cytometer was used to analyze the temporal course of the forward and the sideward efficiency during the entire life-cycle. Results showed differences between the two species. From an ACP analysis, the variation of the optical properties were associated with the chlorophyll-a concentration by living cell, the thickness of the frustule and the aggregate formation. To finish, the bulk backscattering coefficient was rebuilt from σbb of individual cells and compare with the bb measured by a WET Labs ECO-BB9. Relative errors (RE) were between 0.3 and 0.47 and the mean RE was of 0.36. A such work shows

  8. Positive and negative feedback loops in nutrient phytoplankton interactions related to climate dynamics factors in a shallow temperate estuary (Vistula Lagoon, southern Baltic)

    Science.gov (United States)

    Kruk, Marek; Kobos, Justyna; Nawrocka, Lidia; Parszuto, Katarzyna

    2018-04-01

    This study aims to demonstrate that factors associated with climate dynamics, such as temperature and wind, affect the ecosystem of the shallow Vistula Lagoon in the southern Baltic and cause nutrient forms phytoplankton interactions: the growth of biomass and constraints of it. This occurs through a network of direct and indirect relationships between environmental and phytoplankton factors, including interactions of positive and negative feedback loops. Path analysis supported by structural equation modeling (SEM) was used to test hypotheses regarding the impact of climate factors on algal assemblages. Increased phytoplankton biomass was affected directly by water temperature and salinity, while the wind speed effect was indirect as it resulted in increased concentrations of suspended solids (SS) in the water column. Simultaneously, the concentration of SS in the water was positively correlated with particulate organic carbon (POC), particulate nitrogen (PN), and particulate phosphorus (PP), and was negatively correlated with the total nitrogen to phosphorus (N:P) ratio. Particulate forms of C, N, and phosphorus (P), concentrations of soluble reactive phosphorus (SRP) and nitrate and nitrite nitrogen (NO3-N + NO2-N), and ratios of the total N:P and DIN:SRP, all indirectly effected Cyanobacteria C concentrations. These processes influence other phytoplankton groups (Chlorophyta, Bacillariophyceae and the picophytoplankton fraction). Increased levels of SRP associated with organic matter (POC), which stemmed from reduced DIN:SRP ratios, contributed to increased Cyanoprokaryota and picophytoplankton C concentrations, which created a positive feedback loop. However, a simultaneous reduction in the total N:P ratio could have inhibited increases in the biomass of these assemblages by limiting N, which likely formed a negative feedback loop. The study indicates that the nutrients-phytoplankton feedback loop phenomenon can intensify eutrophication in a temperate lagoon

  9. [Ecological characteristics of phytoplankton in Suining tributary under bio-remediation].

    Science.gov (United States)

    Liu, Dongyan; Zhao, Jianfu; Zhang, Yalei; Ma, Limin

    2005-04-01

    Based on the analyses of phytoplankton community in the treated and untreated reaches of Suining tributary of Suzhou River, this paper studied the effects of bio-remediation on phytoplankton. As the result of the remediation, the density and Chl-a content of phytoplankton in treated reach were greatly declined, while the species number and Shannon-Wiener diversity index ascended obviously. The percentage of Chlorophyta and Baeillariophyta ascended, and some species indicating medium-and oligo-pollution were found. All of these illustrated that bio-remediation engineering might significantly benefit to the improvement of phytoplankton community structure and water quality.

  10. UV absorption reveals mycosporine-like amino acids (MAAs in Tatra mountain lake phytoplankton

    Directory of Open Access Journals (Sweden)

    Jerzy Dera

    2013-08-01

    Full Text Available Enhanced absorption of UV radiation, an effect characteristic of mycosporine-like amino acids (MAAs, is reported in samples of phytoplankton from six lakes in the Tatra Mountains National Park (Poland. It was demonstrated that the mass-specific UV absorption coefficients for the phytoplankton in these lakes increased with altitude above sea level. Based on a comparison with the phytoplankton of Alpine lakes, investigated earlier by other authors (cited in this paper, it may be inferred that the phytoplankton of Tatra mountain lakes produce MAAs, which protect plant cells from UV light, the intensity of which increases with altitude.

  11. Phytoplankton community and limnology of Chatla floodplain wetland of Barak valley, Assam, North-East India

    Directory of Open Access Journals (Sweden)

    Sultana Laskar H.

    2013-09-01

    Full Text Available Phytoplankton diversity was investigated over a period of two years (2006 to 2008 in Chatla floodplain wetland in Barak valley, Assam, North-East India. Site 1 and site 2 are two inlets and site 3 is a lentic system associated with vegetation cover of Calamus tenuis and Baringtonia acutangula. The floodplain has a unique hydrology because of the presence of different types of habitats (inlets, fisheries, beels and outlets which maintains a network among the floodplains, rivers and streams. Phytoplankton community composition, density and diversity were studied in relation to environmental variables. All the variables were estimated by following standard methods. Phytoplankton was collected by plankton net and quantitative estimation was made by using Sedgwick Rafter counting cell. Phytoplankton community comprised 53 taxa represented by Chlorophyceae (31, Cyanophyceae (11, Bacillariophyceae (7, Euglenophyceae (1 and Dinophyceae (3. Phytoplankton taxa was dominated by Volvox sp., Nostoc sp., Eunotia sp., Navicula sp., Euglena spp. and density was found highest in site 3 and lowest in site 1. Shannon diversity index (H′ for phytoplankton community varied between 2.4 to 2.65 indicating fairly high species diversity. The varying magnitude of correlationship among environmental variables and phytoplankton species density as shown by Canonical correspondence analysis (CCA indicated that some of the environmental variables (water temperature, transparency, rainfall, nitrate and ammonia are the driving factors for governing the phytoplankton species assemblages in Chatla floodplain wetland. Fluctuation of phytoplankton density and community composition in different habitats indicated various niche apportionment as well as anthropogenic influences.

  12. Realized niches explain spatial gradients in seasonal abundance of phytoplankton groups in the South China Sea

    Science.gov (United States)

    Xiao, Wupeng; Wang, Lei; Laws, Edward; Xie, Yuyuan; Chen, Jixin; Liu, Xin; Chen, Bingzhang; Huang, Bangqin

    2018-03-01

    A basic albeit elusive goal of ocean science is to predict the structure of biological communities from the multitude of environmental conditions they experience. Estimates of the realized niche-based traits (realized traits) of phytoplankton species or functional groups in temperate seas have shown that response traits can help reveal the mechanisms responsible for structuring phytoplankton communities, but such approaches have not been tested in tropical and subtropical marginal seas. Here, we used decadal-scale studies of pigment-based phytoplankton groups and environmental conditions in the South China Sea to test whether realized traits could explain the biogeographic patterns of phytoplankton variability. We estimated the mean and breadth of the phytoplankton realized niches based on responses of the group-specific phytoplankton composition to key environmental factors, and we showed that variations of major phytoplankton groups in this system can be explained by different adaptive trade-offs to constraints imposed by temperature, irradiance, and nutrient concentrations. Differences in the patterns of trade-offs clearly separated the dominant groups from one another and generated four sets of realized traits that mirrored the observed biogeographic distribution patterns. The phytoplankton realized niches and their associated traits that we characterized in the present study could help to predict responses of phytoplankton to changes in environmental conditions in the South China Sea and could be incorporated into global biogeochemical models to anticipate shifts in community structure under future climate scenarios.

  13. Phytoplanktons and zooplanktons diversity in karachi coastal seawater under high and low tide during winter monsoon

    International Nuclear Information System (INIS)

    Yaqoob, N.; Mashiatullah, A.; Sher, N.; Javed, T.; Ghaffar, A.

    2013-01-01

    This paper represents the population density of phytoplanktons and zooplanktons recorded during the marine environmental studies at Karachi coast in the month of February 2011. Samples were collected by towing net, preserved and quantification and identification was carried out under light microscope. Twenty-three phytoplanktons species and nine zooplankton groups were recorded in the seawater from the sampling area of 10 square kilometers. Coscinodiscus and Copepods were dominant in the population of phytoplankton and zooplankton, respectively. Phytoplankton population density increased while zooplankton abundance decreased offshore from the coastline in the open sea. (author)

  14. High Variability in Cellular Stoichiometry of Carbon, Nitrogen, and Phosphorus Within Classes of Marine Eukaryotic Phytoplankton Under Sufficient Nutrient Conditions.

    Science.gov (United States)

    Garcia, Nathan S; Sexton, Julie; Riggins, Tracey; Brown, Jeff; Lomas, Michael W; Martiny, Adam C

    2018-01-01

    Current hypotheses suggest that cellular elemental stoichiometry of marine eukaryotic phytoplankton such as the ratios of cellular carbon:nitrogen:phosphorus (C:N:P) vary between phylogenetic groups. To investigate how phylogenetic structure, cell volume, growth rate, and temperature interact to affect the cellular elemental stoichiometry of marine eukaryotic phytoplankton, we examined the C:N:P composition in 30 isolates across 7 classes of marine phytoplankton that were grown with a sufficient supply of nutrients and nitrate as the nitrogen source. The isolates covered a wide range in cell volume (5 orders of magnitude), growth rate (temperature (2-24°C). Our analysis indicates that C:N:P is highly variable, with statistical model residuals accounting for over half of the total variance and no relationship between phylogeny and elemental stoichiometry. Furthermore, our data indicated that variability in C:P, N:P, and C:N within Bacillariophyceae (diatoms) was as high as that among all of the isolates that we examined. In addition, a linear statistical model identified a positive relationship between diatom cell volume and C:P and N:P. Among all of the isolates that we examined, the statistical model identified temperature as a significant factor, consistent with the temperature-dependent translation efficiency model, but temperature only explained 5% of the total statistical model variance. While some of our results support data from previous field studies, the high variability of elemental ratios within Bacillariophyceae contradicts previous work that suggests that this cosmopolitan group of microalgae has consistently low C:P and N:P ratios in comparison with other groups.

  15. The shape of dose-effect curves for diploid yeast cells irradiated with ionizing particles

    International Nuclear Information System (INIS)

    Pohlit, W.

    1975-01-01

    In a cybernetic model for the radiation reactions in eukaryotic cells, after irradiation they are assumed to be in one of three states: (a) viable cells; (b) with repairable damage; and (c) with irreparable damage. Two biological counter reactions with certain time constants can be observed: (i) recovery from sublethal damage; and (ii) repair of potential lethal damage. The shape of the dose-effect curve is influenced in a characteristic way by the different occupation of these states of the cells and by the time constants of the biological counter reactions. The biochemical analysis of the biological counter reactions, recovery and repair, has shown that both are linked together by the energy pool in the cell. In this way changes in the slope of the dose-effect curve due to different metabolic states of the cells can be understood quantitatively. Also the complicated dependence of survival cells on the absorbed dose rate over a wide range can be explained quantitatively. (author)

  16. Test methods of total dose effects in very large scale integrated circuits

    International Nuclear Information System (INIS)

    He Chaohui; Geng Bin; He Baoping; Yao Yujuan; Li Yonghong; Peng Honglun; Lin Dongsheng; Zhou Hui; Chen Yusheng

    2004-01-01

    A kind of test method of total dose effects (TDE) is presented for very large scale integrated circuits (VLSI). The consumption current of devices is measured while function parameters of devices (or circuits) are measured. Then the relation between data errors and consumption current can be analyzed and mechanism of TDE in VLSI can be proposed. Experimental results of 60 Co γ TDEs are given for SRAMs, EEPROMs, FLASH ROMs and a kind of CPU

  17. Phytoplankton abundance, dominance and coexistence in an eutrophic reservoir in the state of Pernambuco, Northeast Brazil

    Directory of Open Access Journals (Sweden)

    Giulliari A. S. T. Lira

    2011-12-01

    Full Text Available The present study reports the phytoplankton abundance, dominance and co-existence relationships in the eutrophic Carpina reservoir, Pernambuco, Brazil. Sampling was carried out at six different depths bimonthly at a single reservoir spanning two climatic periods: dry season (January, September, and November 2006 and rainy season (March, May, and July 2006. Density, abundance, dominance, specific diversity and equitability of the community were determined, along with chlorophyll a, and physical and chemical variables of the environment. Eight species were considered abundant, and their densities corresponded to more than 90% of the total phytoplankton community quantified. Cyanobacteria represented more than 80% of this density. Cylindrospermopsis raciborskii was the only dominant taxon in the dry season, and was co-dominant in the rainy season. C. raciborskii, Planktothrix agardhii and Geitlerinema amphibium had the greatest densities and lowest vertical variation coefficients. The statistical analysis indicated relationships with vertical and seasonal variations in the phytoplankton community and the following variables: total dissolved solids, water temperature, electrical conductivity and pH. The changes in the environmental variables were discrete and regulated by the establishment of precipitation however, they were able to promote vertical and seasonal instability in the structure of the phytoplankton community.O presente estudo remete às relações de abundância, dominância e co-existência fitoplanctônica no reservatório eutrófico de Carpina, Pernambuco, Brasil. Foram realizadas amostragens bimensalmente, em seis profundidades, em um único ponto do reservatório, contemplando dois períodos sazonais: seco (janeiro, setembro e novembro/2006 e chuvoso (março, maio e julho/2006. A densidade, abundância, dominância, diversidade específica e equitabilidade foram determinadas, além da clorofila a e algumas variáveis físicas e qu

  18. Can results from animal studies be used to estimate dose or low dose effects in humans

    International Nuclear Information System (INIS)

    Thomas, J.M.; Eberhardt, L.L.

    1981-01-01

    A method has been devised to extrapolate biological equilibrium levels between animal species and subsequently to humans. Our initial premise was based on the observation that radionuclide retention is normally a function of metabolism so that direct or indirect measures could be described by a power law based on body weights of test animal species. However, we found that such interspecies comparisons ought to be based on the coefficient of the power equation rather than on the exponential parameter. The method is illustrated using retention data obtained from five non-ruminant species (including humans) that were fed radionuclides with different properties. It appears that biological equilibrium level for radionuclides in man can be estimated using data from mice, rats, and dogs. The need to extrapolate low-dose effects data obtained from small animals (usually rodents) to humans is not unique to radiation dosimetry or radiation protection problems. Therefore, some quantitative problems connected with estimating low-dose effects from other disciplines have been reviewed, both because of the concern about effects induced by the radionuclide moiety of a radiopharmaceutical and those of the nonradioactive component. The possibility of extrapolating low-dose effects calculated from animal studies to human is discussed

  19. Can results from animal studies be used to estimate dose or low dose effects in humans

    International Nuclear Information System (INIS)

    Thomas, J.M.; Eberhardt, L.L.

    1981-01-01

    We have devised a method to extrapolate biological equilibrium levels between animal species and subsequently to humans. Our initial premise was based on the observation that radionuclide retention is normally a function of metabolism so that direct or indirect measures could be described by a power law based on body weights of test animal species. However, we found that such interspecies comparisons ought to be based on the coefficient of the power equation rather than on the exponential parameter. The method is illustrated using retention data obtained from five non-ruminant species (including humans) that were fed radionuclides with different properties. It appears that biological equilibrium level for radionuclides in man can be estimated using data from mice, rats and dogs. The need to extrapolate low-dose effects data obtained from small animals (usually rodents) to humans is not unique to radiation dosimetry or radiation protection problems. Therefore, researchers have reviewed some quantitative problems connected with estimating low-dose effects from other disciplines, both because of the concern about effects induced by the radionuclide moiety of a radiopharmaceutical and those of the nonradioactive component. The possibility of extrapolating low-dose effects calculated from animal studies to humans is discussed

  20. Small phytoplankton contribution to the standing stocks and the total primary production in the Amundsen Sea

    Directory of Open Access Journals (Sweden)

    S. H. Lee

    2017-08-01

    Full Text Available Small phytoplankton are anticipated to be more important in a recently warming and freshening ocean condition. However, little information on the contribution of small phytoplankton to overall phytoplankton production is currently available in the Amundsen Sea. To determine the contributions of small phytoplankton to total biomass and primary production, carbon and nitrogen uptake rates of total and small phytoplankton were obtained from 12 productivity stations in the Amundsen Sea. The daily carbon uptake rates of total phytoplankton averaged in this study were 0.42 g C m−2 d−1 (SD  =  ± 0.30 g C m−2 d−1 and 0.84 g C m−2 d−1 (SD  =  ± 0.18 g C m−2 d−1 for non-polynya and polynya regions, respectively, whereas the daily total nitrogen (nitrate and ammonium uptake rates were 0.12 g N m−2 d−1 (SD  =  ± 0.09 g N m−2 d−1 and 0.21 g N m−2 d−1 (SD  =  ± 0.11 g N m−2 d−1, respectively, for non-polynya and polynya regions, all of which were within the ranges reported previously. Small phytoplankton contributed 26.9 and 27.7 % to the total carbon and nitrogen uptake rates of phytoplankton in this study, respectively, which were relatively higher than the chlorophyll a contribution (19.4 % of small phytoplankton. For a comparison of different regions, the contributions for chlorophyll a concentration and primary production of small phytoplankton averaged from all the non-polynya stations were 42.4 and 50.8 %, which were significantly higher than those (7.9 and 14.9 %, respectively in the polynya region. A strong negative correlation (r2 = 0. 790, p<0. 05 was found between the contributions of small phytoplankton and the total daily primary production of phytoplankton in this study. This finding implies that daily primary production decreases as small phytoplankton contribution increases, which is

  1. Effect of intensive epilimnetic withdrawal on phytoplankton community in a (subtropical deep reservoir

    Directory of Open Access Journals (Sweden)

    Man Zhang

    2013-10-01

    Full Text Available Withdrawal is an important process in reservoir hydrodynamics, removing phytoplankton with flushed water. Zooplankton,the grazers of phytoplankton, having longer generation times, are even more susceptible than phytoplankton to flushing loss. Therefore phytoplankton are affected not only by abiotic conditions linked to hydrodynamics but also by zooplankton due to weakened grazing pressure. During the Asian Games (November 12-27, 2010 in Guangzhou, China, two intensive epilimnetic withdrawals were conducted in Liuxihe, a deep canyon-shaped reservoir. To examine the influence of the intensive epilimnetic withdrawals on the phytoplankton community, a seven-week field observation and a hydrodynamic simulation were carried out. The observation was divided in two stages: stage 1 represented partial surface vertical mixing period, and stage 2 represented intensive epilimnetic withdrawal period. It was found that phytoplankton abundance and biomass declined with water temperature and partial surface vertical mixing in stage 1. However, the intensive epilimnetic withdrawal reversed this decreasing trend and increased phytoplankton biomass and abundance in stage 2. Phytoplankton showed a higher rate of composition change in stage 2. A numerical model (DYRESM-CAEDYM simulated scenarios with and without epilimnetic withdrawal to test their effects on abiotic factors (water temperature, suspended sediment and soluble reactive phosphorus for phytoplankton. The results showed no obvious difference in the abiotic factors between the two scenarios during stage 2. We therefore suggested that the abiotic factors in the water column were probably driven by a seasonal pattern, not by epilimnetic withdrawal. It is likely that the intensive epilimnetic withdrawal could remove large crustaceans. The reduced grazing pressure probably explained the increase of phytoplankton biomass and abundance after the withdrawal. Thus, we suggest that reservoir operation should pay

  2. MODEL OF PHYTOPLANKTON COMPETITION FOR LIMITING AND NONLIMITING NUTRIENTS: IMPLICATIONS FOR DEVELOPMENT OF ESTUARINE AND NEARSHORE MANAGEMENT SCHEMES

    Science.gov (United States)

    The global increase of noxious bloom occurrences has increased the need for phytoplankton management schemes. Such schemes require the ability to predict phytoplankton succession. Equilibrium Resources Competition theory, which is popular for predicting succession in lake systems...

  3. Studies on the phytoplankton of the deep subalpine Lake Iseo

    Directory of Open Access Journals (Sweden)

    Rosario MOSELLO

    2003-08-01

    Full Text Available This paper reports the results of investigations carried out on the chemical characteristics and phytoplankton community of Lake Iseo. Samplings were performed on a monthly basis from 1998 to 2000. At least three main algal groups dominated the community throughout the study period. The large Bacillariophyceae were dominant mainly during late winter and early spring (Aulacoseira spp., Melosira varians, Asterionella formosa, with few species able to maintain occasional positive growth also during mid summer and/or autumn (Fragilaria crotonensis and Diatoma elongatum. The thermal stability of the water column and silica depletion were the main factors responsible for the decline of the large spring diatoms. The subsequent growth of Mougeotia sp. (Conjugatophyceae was favoured by its lower sinking rate and resistance to increasing grazing pressure by the dominant copepods (Copidodiaptomus steueri and cladocerans (Daphnia hyalina × galeata. Among the cyanobacteria, the greater development of Planktothrix rubescens in the autumn months, with conditions of vertical homogenisation and decreasing Zeu/Zmix ratios, was favoured by its ability to survive at low light irradiances. The temporal replacement of these three groups constitutes the main sequence of the annual phytoplankton succession in Lake Iseo. A large development of other algal groups was recorded only in one or two of the three study years (e.g. Dinophyceae and Chlorococcales. The changes observed in the annual phytoplankton development are discussed in the light of differences in the spring fertilisation of the waters, caused by differences in the depth of the layer involved in the late winter and spring vertical mixing.

  4. Remote sensing the phytoplankton seasonal succession of the Red Sea.

    Science.gov (United States)

    Raitsos, Dionysios E; Pradhan, Yaswant; Brewin, Robert J W; Stenchikov, Georgiy; Hoteit, Ibrahim

    2013-01-01

    The Red Sea holds one of the most diverse marine ecosystems, primarily due to coral reefs. However, knowledge on large-scale phytoplankton dynamics is limited. Analysis of a 10-year high resolution Chlorophyll-a (Chl-a) dataset, along with remotely-sensed sea surface temperature and wind, provided a detailed description of the spatiotemporal seasonal succession of phytoplankton biomass in the Red Sea. Based on MODIS (Moderate-resolution Imaging Spectroradiometer) data, four distinct Red Sea provinces and seasons are suggested, covering the major patterns of surface phytoplankton production. The Red Sea Chl-a depicts a distinct seasonality with maximum concentrations seen during the winter time (attributed to vertical mixing in the north and wind-induced horizontal intrusion of nutrient-rich water in the south), and minimum concentrations during the summer (associated with strong seasonal stratification). The initiation of the seasonal succession occurs in autumn and lasts until early spring. However, weekly Chl-a seasonal succession data revealed that during the month of June, consistent anti-cyclonic eddies transfer nutrients and/or Chl-a to the open waters of the central Red Sea. This phenomenon occurs during the stratified nutrient depleted season, and thus could provide an important source of nutrients to the open waters. Remotely-sensed synoptic observations highlight that Chl-a does not increase regularly from north to south as previously thought. The Northern part of the Central Red Sea province appears to be the most oligotrophic area (opposed to southern and northern domains). This is likely due to the absence of strong mixing, which is apparent at the northern end of the Red Sea, and low nutrient intrusion in comparison with the southern end. Although the Red Sea is considered an oligotrophic sea, sporadic blooms occur that reach mesotrophic levels. The water temperature and the prevailing winds control the nutrient concentrations within the euphotic zone

  5. Cadmium toxicity to two marine phytoplankton under different nutrient conditions

    International Nuclear Information System (INIS)

    Miao, A.-J.; Wang, W.-X.

    2006-01-01

    Cd accumulation and toxicity in two marine phytoplankton (diatom Thalassiosira weissflogii and dinoflagellate Prorocentrum minimum) under different nutrient conditions (nutrient-enriched, N- and P-starved conditions) were examined in this study. Strong interactions between the nutrients and Cd uptake by the two algal species were found. Cd accumulation as well as N and P starvation themselves inhibited the assimilation of N, P, and Si by the phytoplankton. Conversely, N starvation strongly inhibited Cd accumulation but no influence was observed under P starvation. However, the Cd accumulation difference between nutrient-enriched and N-starved cells was smaller when [Cd 2+ ] was increased in the medium, indicating that net Cd accumulation was less dependent on the N-containing ligands at high-Cd levels. As for the subcellular distribution of the accumulated Cd, most was distributed in the insoluble fraction of T. weissflogii while it was evenly distributed in the soluble and insoluble fractions of P. minimum at low-Cd levels. A small percentage of cellular Cd ( 2+ ], which increased when the [Cd 2+ ] increased. Cd toxicity in phytoplankton was quantified as depression of growth and maximal photosynthetic system II quantum yield, and was correlated with the [Cd 2+ ], intracellular Cd concentration, and Cd concentrations in the cell-surface-adsorbed, soluble, and insoluble fractions. According to the estimated median inhibition concentration (IC50) based on the different types of Cd concentration, the toxicity difference among the different nutrient-conditioned cells was the smallest when the Cd concentration in the soluble fraction was used, suggesting that it may be the best predictor of Cd toxicity under different nutrient conditions

  6. Remote Sensing the Phytoplankton Seasonal Succession of the Red Sea

    KAUST Repository

    Raitsos, Dionysios E.

    2013-06-05

    The Red Sea holds one of the most diverse marine ecosystems, primarily due to coral reefs. However, knowledge on large-scale phytoplankton dynamics is limited. Analysis of a 10-year high resolution Chlorophyll-a (Chl-a) dataset, along with remotely-sensed sea surface temperature and wind, provided a detailed description of the spatiotemporal seasonal succession of phytoplankton biomass in the Red Sea. Based on MODIS (Moderate-resolution Imaging Spectroradiometer) data, four distinct Red Sea provinces and seasons are suggested, covering the major patterns of surface phytoplankton production. The Red Sea Chl-a depicts a distinct seasonality with maximum concentrations seen during the winter time (attributed to vertical mixing in the north and wind-induced horizontal intrusion of nutrient-rich water in the south), and minimum concentrations during the summer (associated with strong seasonal stratification). The initiation of the seasonal succession occurs in autumn and lasts until early spring. However, weekly Chl-a seasonal succession data revealed that during the month of June, consistent anti-cyclonic eddies transfer nutrients and/or Chl-a to the open waters of the central Red Sea. This phenomenon occurs during the stratified nutrient depleted season, and thus could provide an important source of nutrients to the open waters. Remotely-sensed synoptic observations highlight that Chl-a does not increase regularly from north to south as previously thought. The Northern part of the Central Red Sea province appears to be the most oligotrophic area (opposed to southern and northern domains). This is likely due to the absence of strong mixing, which is apparent at the northern end of the Red Sea, and low nutrient intrusion in comparison with the southern end. Although the Red Sea is considered an oligotrophic sea, sporadic blooms occur that reach mesotrophic levels. The water temperature and the prevailing winds control the nutrient concentrations within the euphotic zone

  7. Nutrient and Phytoplankton Analysis of a Mediterranean Coastal Area

    Science.gov (United States)

    Sebastiá, M. T.; Rodilla, M.

    2013-01-01

    Identifying and quantifying the key anthropogenic nutrient input sources are essential to adopting management measures that can target input for maximum effect in controlling the phytoplankton biomass. In this study, three systems characterized by distinctive main nutrient sources were sampled along a Mediterranean coast transect. These sources were groundwater discharge in the Ahuir area, the Serpis river discharge in the Venecia area, and a submarine wastewater outfall 1,900 m from the coast. The study area includes factors considered important in determining a coastal area as a sensitive area: it has significant nutrient sources, tourism is a major source of income in the region, and it includes an area of high water residence time (Venecia area) which is affected by the harbor facilities and by wastewater discharges. We found that in the Ahuir and the submarine wastewater outfall areas, the effects of freshwater inputs were reduced because of a greater water exchange with the oligotrophic Mediterranean waters. On the other hand, in the Venecia area, the highest levels of nutrient concentration and phytoplankton biomass were attributed to the greatest water residence time. In this enclosed area, harmful dinoflagellates were detected ( Alexandrium sp. and Dinophysis caudata). If the planned enlargement of the Gandia Harbor proceeds, it may increase the vulnerability of this system and provide the proper conditions of confinement for the dinoflagellate blooms' development. Management measures should first target phosphorus inputs as this is the most potential-limiting nutrient in the Venecia area and comes from a point source that is easier to control. Finally, we recommend that harbor environmental management plans include regular monitoring of water quality in adjacent waters to identify adverse phytoplankton community changes.

  8. Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere

    Directory of Open Access Journals (Sweden)

    Antonietta Quigg

    2012-05-01

    Full Text Available The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna.

  9. Nutrient and phytoplankton analysis of a Mediterranean coastal area.

    Science.gov (United States)

    Sebastiá, M T; Rodilla, M

    2013-01-01

    Identifying and quantifying the key anthropogenic nutrient input sources are essential to adopting management measures that can target input for maximum effect in controlling the phytoplankton biomass. In this study, three systems characterized by distinctive main nutrient sources were sampled along a Mediterranean coast transect. These sources were groundwater discharge in the Ahuir area, the Serpis river discharge in the Venecia area, and a submarine wastewater outfall 1,900 m from the coast. The study area includes factors considered important in determining a coastal area as a sensitive area: it has significant nutrient sources, tourism is a major source of income in the region, and it includes an area of high water residence time (Venecia area) which is affected by the harbor facilities and by wastewater discharges. We found that in the Ahuir and the submarine wastewater outfall areas, the effects of freshwater inputs were reduced because of a greater water exchange with the oligotrophic Mediterranean waters. On the other hand, in the Venecia area, the highest levels of nutrient concentration and phytoplankton biomass were attributed to the greatest water residence time. In this enclosed area, harmful dinoflagellates were detected (Alexandrium sp. and Dinophysis caudata). If the planned enlargement of the Gandia Harbor proceeds, it may increase the vulnerability of this system and provide the proper conditions of confinement for the dinoflagellate blooms' development. Management measures should first target phosphorus inputs as this is the most potential-limiting nutrient in the Venecia area and comes from a point source that is easier to control. Finally, we recommend that harbor environmental management plans include regular monitoring of water quality in adjacent waters to identify adverse phytoplankton community changes.

  10. Chlorophyll-a specific volume scattering function of phytoplankton.

    Science.gov (United States)

    Tan, Hiroyuki; Oishi, Tomohiko; Tanaka, Akihiko; Doerffer, Roland; Tan, Yasuhiro

    2017-06-12

    Chlorophyll-a specific light volume scattering functions (VSFs) by cultured phytoplankton in visible spectrum range is presented. Chlorophyll-a specific VSFs were determined based on the linear least squares method using a measured VSFs with different chlorophyll-a concentrations. We found obvious variability of it in terms of spectral and angular shapes of VSF between cultures. It was also presented that chlorophyll-a specific scattering significantly affected on spectral variation of the remote sensing reflectance, depending on spectral shape of b. This result is useful for developing an advance algorithm of ocean color remote sensing and for deep understanding of light in the sea.

  11. Phytoplankton virus production negatively affected by iron limitation

    Directory of Open Access Journals (Sweden)

    Hans A Slagter

    2016-08-01

    Full Text Available Fe-limited monocultures of the ubiquitous algae Micromonas pusilla and Phaeocystis globosa were infected with their respective viruses (MpV and PgV to ascertain the effect of Fe-limitation on phytoplankton host-virus dynamics. The effect of the viral shunt on Fe concentrations and bioavailability is starting to gain attention, since not only is Fe released through lysis, but also its solubility is increased by the simultaneous release of Fe-binding dissolved organic ligands. However, the effect of Fe-limitation on the process of viral lysis itself is poorly understood. In this study fine adjustment of a seawater-based culture medium including the use of ultra-clean trace metal conditions and protocols allowed for Fe-limited growth at nanomolar amounts as opposed to micromolar amounts typically employed in culturing. Viral lysates derived from Fe-limited and Fe-replete (for comparison hosts were cross-inoculated in hosts of both Fe treatments, to judge the quality of the resulting lysate as well as the effect of Fe introduction after initial infection. For both phytoplankton host-virus systems, the virus burst size reduced strongly under Fe stress, i.e. on average 28 ±1% of replete. Moreover, the MpV virus progeny showed highly reduced infectivity of 30±7%, whereas PgV infectivity was not affected. A small addition of Fe to Fe-limited cultures coming from the Fe-replete lysate counteracted the negative effect of Fe-limitation on phytoplankton virus production to some extent (but still half of replete, implying that the physiological history of the host at the moment of infection was an important underlying factor. These results indicate that Fe-limitation has the strong potential to reduce the loss of phytoplankton due to virus infection, thereby affecting the extent of Fe-cycling through the viral shunt. To what extent this affects the contribution of viral lysis-induced organic ligand release needs further study.

  12. Variation of phytoplankton community structure from the Pearl River estuary to South China Sea.

    Science.gov (United States)

    Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Sun, Cui-Ci; Wu, Mei-Lin

    2015-10-01

    The Pearl River is located in the northern part of South China Sea. The environment of the Pearl River estuary (PRE) is significantly impacted by nutrients from anthropogenic activities. Along the anthropogenic pollution gradient from the PRE to South China Sea, the phylogenetic diversity and biomass of phytoplankton was examined in relation to physic-chemical variables. The richness of rbcL gene was higher in the open sea than the estuary, while the concentration of chlorophyll a (Chl a) was higher in the estuary than in the open sea. The cluster analysis of the sequences data resulted in seven phytoplankton community types and the dominant species of phytoplankton changed from Cryptophytes and Diatoms to Prymnesiophytes and Diatoms along the gradient. The community structure of phytoplankton was shaped by nutrients and salinity. The phytoplankton biomass was significantly positively affected by phosphorus, nitrite and ammonium (P < 0.01) but negatively by salinity (P < 0.05); the phytoplankton diversity was highly positively affected by salinity (P < 0.05) but negatively by silicate and nitrate (P < 0.01; P < 0.05, respectively). Anthropogenic activities played a critical role in the phytoplankton distribution and biomass of the study area. Further research is necessary to reveal the influence mechanism of environmental factors on the phytoplankton.

  13. Spatio-temporal patterns and predictions of phytoplankton assemblages in a subtropical river delta system

    DEFF Research Database (Denmark)

    Wang, Chao; Li, Xinhui; Wang, Xiangxiu

    2016-01-01

    Spatial and seasonal sampling within a subtropical river delta system, the Pearl River Delta (China), provided data to determine seasonal phytoplankton patterns and develop prediction models. The high nutrient levels and frequent water exchanges resulted in a phytoplankton community with greatest...

  14. Phytoplankton in the cooling pond of a nuclear fuel plant. II. Spectral analysis

    International Nuclear Information System (INIS)

    Tokarskaya, Z.B.; Smagin, A.I.; Ryzhkov, E.G.; Nikitina, L.V.

    1995-01-01

    This study continues investigations into the development dynamics of phytoplankton and hydrochemical and meteorological factors over a periods of 26 years in the cooling pond of the Mayak Production Association in the Kyzyl-Trash Lake. The aim is to evaluate the long-term oscillations in phytoplankton owing to changes in hydrochemical and meteorological factors. 6 refs., 2 figs., 1 tab

  15. Phytoplankton diversity in the bioremediation pool in PTAPB-BATAN Yogyakarta

    International Nuclear Information System (INIS)

    Wijiyono; Artiningsih, Sri

    2013-01-01

    Research has been done on Phytoplankton Diversity in Bioremediation Pool in PTAPB-BATAN Yogyakarta. This study aims to determine the diversity of phytoplankton and phytoplankton species are numerous in the bioremediation pool in PTAPB BATAN. This study is an observational study conducted from September to November 2012. The population in this study is all kinds of phytoplankton that live in the bioremediation pool. The sample was filtered with all phytoplankton plankton net at each sampling point. This study was conducted to determine the point of sampling as much as 3 points, namely at the inlet, the center of the pond, and exit channel, with each point done 3 times repetition. Sampling was done by taking as much as 50 liters of water at each sample point, the water sample is filtered directly into the plankton net. Filtered water put into flakon bottles. Observation and identification of plankton were done in the laboratory. The research found as many as 21 species of phytoplankton consisting of Scenedesmus acuminatus, Scenedesmus quadricauda, Closterium moniiferum, Pleurosigma sp., Rivularia bullata, Chroococcus sp., Cocconeis sp., Pinnularia viridis, Navicula sp., Spirogyra sp., Thiopedia rosea, Cyclotella sp., Minidiscus sp., Achnantes sp., ChIorella sp., Oscillatoria sp., Hemiaulus sp., Surirella sp., Chattonella sp., Thalasiossira mala, Leuvenia sp. Phytoplankton density value of 5.330 ind / I. Phytoplankton diversity index value was 2.6062, included in the medium category. (author)

  16. The method of multispectral image processing of phytoplankton processing for environmental control of water pollution

    Science.gov (United States)

    Petruk, Vasil; Kvaternyuk, Sergii; Yasynska, Victoria; Kozachuk, Anastasia; Kotyra, Andrzej; Romaniuk, Ryszard S.; Askarova, Nursanat

    2015-12-01

    The paper presents improvement of the method of environmental monitoring of water bodies based on bioindication by phytoplankton, which identify phytoplankton particles carried out on the basis of comparison array multispectral images using Bayesian classifier of solving function based on Mahalanobis distance. It allows to evaluate objectively complex anthropogenic and technological impacts on aquatic ecosystems.

  17. Pronounced daily succession of phytoplankton, archaea and bacteria following a spring bloom.

    Science.gov (United States)

    Needham, David M; Fuhrman, Jed A

    2016-02-29

    Marine phytoplankton perform approximately half of global carbon fixation, with their blooms contributing disproportionately to carbon sequestration(1), and most phytoplankton production is ultimately consumed by heterotrophic prokaryotes(2). Therefore, phytoplankton and heterotrophic community dynamics are important in modelling carbon cycling and the impacts of global change(3). In a typical bloom, diatoms dominate initially, transitioning over several weeks to smaller and motile phytoplankton(4). Here, we show unexpected, rapid community variation from daily rRNA analysis of phytoplankton and prokaryotic community members following a bloom off southern California. Analysis of phytoplankton chloroplast 16S rRNA demonstrated ten different dominant phytoplankton over 18 days alone, including four taxa with animal toxin-producing strains. The dominant diatoms, flagellates and picophytoplankton varied dramatically in carbon export potential. Dominant prokaryotes also varied rapidly. Euryarchaea briefly became the most abundant organism, peaking over a few days to account for about 40% of prokaryotes. Phytoplankton and prokaryotic communities correlated better with each other than with environmental parameters. Extending beyond the traditional view of blooms being controlled primarily by physics and inorganic nutrients, these dynamics imply highly heterogeneous, continually changing conditions over time and/or space and suggest that interactions among microorganisms are critical in controlling plankton diversity, dynamics and fates.

  18. The influence of plant-associated filter feeders on phytoplankton biomass: a mesocosm study

    NARCIS (Netherlands)

    Vanderstukken, M.; Declerck, S.A.J.; Pals, A.; De Meester, L.; Muylaert, K.

    2010-01-01

    Low phytoplankton biomass usually occurs in the presence of submerged macrophytes, possibly because submerged macrophytes enhance top-down control of phytoplankton by offering a refuge for efficient grazers like Daphnia against fish predation. However, other field studies also suggest that submerged

  19. Allelopathic effect of the aquatic macrophyte, Stratiotes aloides, on natural phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.; Mau, B.; Smolders, A.J.P.; Van Donk, E.

    2006-01-01

    A survey of different Dutch Stratiotes stands showed that the density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between the rosettes of S. aloides. Analyses of water samples revealed that nutrient limitation was unlikely to have caused the lower phytoplankton

  20. Phytoplankton dynamics in the Gulf of Aqaba (Eilat, Red Sea): A simulation study of mariculture effects

    International Nuclear Information System (INIS)

    Laiolo, Leonardo; Barausse, Alberto; Dubinsky, Zvy; Palmeri, Luca; Goffredo, Stefano; Kamenir, Yury; Al-Najjar, Tariq; Iluz, David

    2014-01-01

    Highlights: • Fish farms in the Gulf of Aqaba strongly affect phytoplankton levels. • Integrating statistics and ecological models help understand phytoplankton dynamics. • Phytoplankton dynamics are driven by mariculture activity and natural forces. • Mariculture can alter typical phytoplankton dynamics and seasonal succession. - Abstract: The northern Gulf of Aqaba is an oligotrophic water body hosting valuable coral reefs. In the Gulf, phytoplankton dynamics are driven by an annual cycle of stratification and mixing. Superimposed on that fairly regular pattern was the establishment of a shallow-water fish-farm initiative that increased gradually until its activity was terminated in June 2008. Nutrient, water temperature, irradiation, phytoplankton data gathered in the area during the years 2007–2009, covering the peak of the fish-farm activity and its cessation, were analyzed by means of statistical analyses and ecological models of phytoplankton dynamics. Two datasets, one from an open water station and one next to the fish farms, were used. Results show that nutrient concentrations and, consequently, phytoplankton abundance and seasonal succession were radically altered by the pollution originating from the fish-farm in the sampling station closer to it, and also that the fish-farm might even have influenced the open water station

  1. A prospective study of marine phytoplankton and reported illness among recreational beachgoers in Puerto Rico, 2009

    Science.gov (United States)

    BACKGROUND: Blooms of marine phytoplankton may adversely affect human health. The potential public health impact of low-level exposures is not well established, and few prospective cohort studies of recreational exposures to marine phytoplankton have been conducted.OBJECTIVE: We ...

  2. Phytoplankton absorption and pigment adaptation of a red tide in the ...

    African Journals Online (AJOL)

    Phytoplankton absorption and pigment characteristics of a red tide were investigated in coastal waters of the southern Benguela. Diagnostic indices indicated that dinoflagellates were the dominant phytoplankton group, with diatoms and small flagellates being of secondary importance. Very high biomass was observed ...

  3. Response of phytoplankton to nutrient enrichment with high growth rates in a tropical monsoonal estuary - Zuari estuary, India

    Digital Repository Service at National Institute of Oceanography (India)

    Mochemadkar, S.; Gauns, M.; Pratihary, A.K.; Thorat, B.R.; Roy, R.; Pai, I.K.; Naqvi, S.W.A.

    nitzschioides exhibited the ability to withstand hypoxic condition. [Keywords: Zuari estuary, Premonsoon, Nutrient uptake, Phytoplankton, Hypoxic] Introduction Phytoplanktons are responsible for nearly half of global primary production1. Diatoms... and fresh water inputs. Light and nutrients are the primary factors regulating phytoplankton growth4,5 followed by temperature and salinity6 . Major (macro) nutrients essential for plant growth are nitrogen, phosphorous and silicon7. Phytoplankton...

  4. Seasonal patterns in phytoplankton photosynthetic parameters and primary production at a coastal NW Mediterranean site

    Directory of Open Access Journals (Sweden)

    Josep M. Gasol

    2016-09-01

    Full Text Available We carried out monthly photosynthesis-irradiance (P-E experiments with the 14C-method for 12 years (2003–2014 to determine the photosynthetic parameters and primary production of surface phytoplankton in the Blanes Bay Microbial Observatory, a coastal sampling station in the NW Mediterranean Sea. Our goal was to obtain seasonal trends and to establish the basis for detecting future changes of primary production in this oligotrophic area. The maximal photosynthetic rate PBmax ranged 30-fold (0.5-15 mg C mg Chl a–1 h–1, averaged 3.7 mg C mg Chl a–1 h–1 (±0.25 SE and was highest in August and lowest in April and December. We only observed photoinhibition twice. The initial or light-limited slope of the P-E relationship, αB, was low, averaging 0.007 mg C mg Chl a–1 h–1 (μmol photons m–2 s–1–1 (±0.001 SE, range 0.001-0.045 and showed the lowest values in spring (April-June. The light saturation parameter or saturation irradiance, EK, averaged 711 μmol photons m–2 s–1 (± 58.4 SE and tended to be higher in spring and lower in winter. Phytoplankton assemblages were typically dominated by picoeukaryotes in early winter, diatoms in late autumn and late winter, dinoflagellates in spring and cyanobacteria in summer. Total particulate primary production averaged 1.45 mg C m-3 h–1 (±0.13 SE with highest values in winter (up to 8.50 mg C m-3 h–1 and lowest values in summer (summer average, 0.30 mg C m-3 h–1, while chlorophyll-specific primary production averaged 2.49 mg C mg Chl a–1 h–1 (±0.19, SE and peaked in summer (up to 12.0 mg C mg Chl a–1 h–1 in August. 14C-determined phytoplankton growth rates varied between ca. 0.3 d–1 in winter and 0.5 d–1 in summer and were within 60-80% of the maximal rates of growth, based on PBmax. Chlorophyll a was a good predictor of primary production only in the winter and autumn. Seasonality appeared to explain most of the variability in the studied variables, while

  5. Seasonal patterns in phytoplankton photosynthetic parameters and primary production at a coastal NW Mediterranean site

    KAUST Repository

    Gasol, Josep M.

    2016-10-11

    We carried out monthly photosynthesis-irradiance (P-E) experiments with the 14C-method for 12 years (2003–2014) to determine the photosynthetic parameters and primary production of surface phytoplankton in the Blanes Bay Microbial Observatory, a coastal sampling station in the NW Mediterranean Sea. Our goal was to obtain seasonal trends and to establish the basis for detecting future changes of primary production in this oligotrophic area. The maximal photosynthetic rate PBmax ranged 30-fold (0.5-15 mg C mg Chl a–1 h–1), averaged 3.7 mg C mg Chl a–1 h–1 (±0.25 SE) and was highest in August and lowest in April and December. We only observed photoinhibition twice. The initial or light-limited slope of the P-E relationship, αB, was low, averaging 0.007 mg C mg Chl a–1 h–1 (μmol photons m–2 s–1)–1 (±0.001 SE, range 0.001-0.045) and showed the lowest values in spring (April-June). The light saturation parameter or saturation irradiance, EK, averaged 711 μmol photons m–2 s–1 (±58.4 SE) and tended to be higher in spring and lower in winter. Phytoplankton assemblages were typically dominated by picoeukaryotes in early winter, diatoms in late autumn and late winter, dinoflagellates in spring and cyanobacteria in summer. Total particulate primary production averaged 1.45 mg C m–3 h–1 (±0.13 SE) with highest values in winter (up to 8.50 mg C m–3 h–1) and lowest values in summer (summer average, 0.30 mg C m–3 h–1), while chlorophyll-specific primary production averaged 2.49 mg C mg Chl a–1 h–1 (±0.19, SE) and peaked in summer (up to 12.0 mg C mg Chl a–1 h–1 in August). 14C-determined phytoplankton growth rates varied between ca. 0.3 d–1 in winter and 0.5 d–1 in summer and were within 60-80% of the maximal rates of growth, based on PBmax. Chlorophyll a was a good predictor of primary production only in the winter and autumn. Seasonality appeared to explain most of the variability in the studied variables, while

  6. Spatial and temporal variation of Peridinium umbonatum F. Stein, 1883 (Dinophyceae and its relationship with total phytoplankton of a shallow, oligotrophic lake in central Brazil (Lagoon Bonita, Distrito Federal Variação especial e temporal de Peridinium umbonatum F. Stein, 1883 (Dinophyceae e sua relação com o fitoplâncton total de uma lagoa rasa e oligotrófica no Brasil Central (Lagoa Bonita, Distrito Federal

    Directory of Open Access Journals (Sweden)

    Patrícia Pereira Gomes

    2010-09-01

    Full Text Available AIM: The main goal of this study was to investigate the temporal and spatial distribution of Peridinium umbonatum and its relationship with the physical and chemical water variables of the pelagic and littoral zones of Lagoon Bonita, located in Brasília, Distrito Federal; METHODS: Samples were collected at three stations: two in the littoral zone and one in the pelagic zone, every 15 days from April 2005 through March 2006; RESULTS: P. umbonatum was the only member of class Dinophyceae recorded during the entire seasonal cycle, with few exceptions, in both the littoral and pelagic zones of Lagoon Bonita. The highest biovolume (7.5 mm³.L-1 of this alga occurred near shore at the beginning of the rainy season, in November 2005. Smaller values of P. umbonatum biovolume were recorded in May and June 2005, typical dry months; CONCLUSIONS: P. umbonatum and the phytoplankton community as a whole had higher biovolumes in the two littoral zone sites, at the end of the dry season and the beginning of the rains. Both, the temporal and spatial scales were relevant in the presence of P. umbonatum, and the spatial heterogeneity was the dominant factor along the study period. The plant community structure, mainly submersed macrophytes, has affected the P. umbonatum population dynamics that took place at shallow, nutrient-poor conditions, small-size lake, which matches with habitat template described to Lo functional classification established by Reynolds et al. (2002.OBJETIVOS: O principal objetivo deste estudo foi investigar a distribuição temporal e espacial de Peridinium umbonatum e sua relação com as variáveis físicas e químicas da água das zonas pelágica e litorânea da Lagoa Bonita, localizada em Brasília, Distrito Federal; MÉTODOS: As amostras foram coletadas em três estações: duas na zona litorânea e uma na zona pelágica, a cada 15 dias, de abril de 2005 a março de 2006; RESULTADOS: P. umbonatum foi o único membro da classe

  7. A biogeochemical model of Lake Pusiano (North Italy and its use in the predictability of phytoplankton blooms: first preliminary results

    Directory of Open Access Journals (Sweden)

    Alessandro OGGIONI

    2006-02-01

    Full Text Available This study reports the first preliminary results of the DYRESM-CAEDYM model application to a mid size sub-alpine lake (Lake Pusiano North Italy. The in-lake modelling is a part of a more general project called Pusiano Integrated Lake/Catchment project (PILE whose final goal is to understand the hydrological and trophic relationship between lake and catchment, supporting the restoration plan of the lake through field data analysis and numerical models. DYRESM is a 1D-3D hydrodynamics model for predicting the vertical profile of temperature, salinity and density. CAEDYM is multi-component ecological model, used here as a phytoplankton-zooplankton processes based model, which includes algorithms to simulate the nutrient cycles within the water column as well as the air-water gas exchanges and the water-sediments fluxes. The first results of the hydrodynamics simulations underline the capability of the model to accurately simulate the surface temperature seasonal trend and the thermal gradient whereas, during summer stratification, the model underestimates the bottom temperature of around 2 °C. The ecological model describes the epilimnetic reactive phosphorus (PO4 depletion (due to the phytoplankton uptake and the increase in PO4 concentrations in the deepest layers of the lake (due to the mineralization processes and the sediments release. In terms of phytoplankton dynamics the model accounts for the Planktothrix rubescens dominance during the whole season, whereas it seems to underestimate the peak in primary production related to both the simulated algal groups (P. rubescens and the rest of the other species aggregated in a single class. The future aims of the project are to complete the model parameterization and to connect the in-lake and the catchment modelling in order to gain an integrated view of the lake-catchment ecosystem as well as to develop a three dimensional model of the lake.

  8. Diversity of Phytoplankton of a sub-tropical reservoir of Mizoram, northeast India

    Directory of Open Access Journals (Sweden)

    Bhushan Kumar Sharma

    2016-12-01

    Full Text Available Phytoplankton of Khawiva reservoir of Mizoram, northeast India (NEI revealed a total of 55 species; nearly concurrent mean monthly richness and high community similarities (vide Sørensen index during two years affirmed homogeneity in its species composition. Phytoplankton comprised dominant component (61.1±14.3% of net plankton and recorded wider density variations. Chlorophyta influenced phytoplankton abundance with quantitative importance of Staurastrum spp. >Xanthidium spp. >Cosmarium spp. in particular. Bacillariophyta formed subdominant group; Cryptophyta and Cyanophyta showed limited importance; and Euglenophyta and Dinophyta recorded poor densities. Phytoplankton is characterized by moderate species diversity, high evenness and low dominance but with wide variations. Richness, abundance and species diversity followed no definite patterns of monthly variations during two years. Insignificant influence of individual abiotic factors on phytoplankton assemblages coupled with low cumulative influence of fifteen abiotic parameters (vide CCA yielded little insight on overall role of abiotic parameters.

  9. Longtime variation of phytoplankton in the South China Sea from the perspective of carbon fixation

    Science.gov (United States)

    Li, Teng; Bai, Yan; Chen, Xiaoyan; Zhu, Qiankun; Gong, Fang; Wang, Difeng

    2017-10-01

    The ocean is a huge carbon pool in the earth, and about half of the anthropogenic emissions of carbon dioxide are absorbed by the ocean each year. By converting inorganic carbon into organic carbon, the photosynthesis process of phytoplankton affords an important way for carbon sequestration in the ocean. According to previous researches, primary production (NPP) and the structure of phytoplankton community are important in regulate the efficiency of biological carbon pump. This study examined the spatiotemporal variability of satellite remote sensing derived chlorophyll a concentration (Chla), phytoplankton carbon biomass (Carbon), composition ratio of micro-, nano- and pico- phytoplankton, NPP and integrated particulate organic carbon (IPOC) during 1998-2007 in the South China Sea (SCS). Micro-, nano-phytoplankton and NPP showed similar seasonal variation with highest values in winter (January) (especially in the western ocean of Luzon Strait) and lowest values in summer (July) in SCS. Chla, phytoplankton carbon biomass, and IPOC showed different seasonal trends with one peak values occurred in winter and lowest in spring. Two sampling areas (A, N:17-21°, E:117.5-120° and B, N:12.5-15°, E:112-119°) in SCS were selected based on spatial distribution of the standard deviation of research parameters mentioned above. Compared to Chla, phytoplankton carbon biomass, NPP and IPOC, the interannual changes of phytoplankton community structure were remarkable in the two areas. The fraction of micro- and nano- phytoplankton in SCS tend to rise when La Nina events occur. Our results contribute to an understanding of the response of phytoplankton to climate change in the marginal sea. To quantify the efficiency of biological carbon pump in this area, more attention should be paid to the development of remote sensing algorithms of export NPP (or POC export flux) as well as the regulate mechanism of export NPP.

  10. Decadal phytoplankton dynamics in response to episodic climatic disturbances in a subtropical deep freshwater ecosystem.

    Science.gov (United States)

    Ko, Chia-Ying; Lai, Chao-Chen; Hsu, Huang-Hsiung; Shiah, Fuh-Kwo

    2017-02-01

    Information of the decadal timescale effects of episodic climatic disturbances (i.e., typhoons) on phytoplankton in freshwater ecosystems have received less attention and fewer seasonal evaluations partly due to the lack of long-term time-series monitoring data in typhoon prevailing areas. Through field observations of a total 36 typhoon cases in a subtropical deep freshwater ecosystem in the period of 2005-2014, we quantified phytoplankton biomass, production and growth rate in response to meteorological and hydrological changes in the weeks before, during and after typhoons between summer and autumn, and also investigated the effects of typhoon characteristics on the aforementioned phytoplankton responses. The results showed that phytoplankton exposed to typhoon disturbances generally exhibited an increasing trend over the weeks before, during and after typhoons in summer but varied in autumn. The correlations and multivariate regressions showed different contributions of meteorological and hydrological variables to individual phytoplankton responses before, during and after typhoons between seasons. The post-typhoon weeks (i.e., within two weeks after a typhoon had passed) were especially important for the timeline of phytoplankton increases and with a detectable seasonal variation that the chlorophyll a concentration significantly increased in autumn whereas both primary production and growth rate were associated with significant changes in summer. Additionally, phytoplankton responses during the post-typhoon weeks were significantly different between discrete or continuous types of typhoon events. Our work illustrated the fact that typhoons did influence phytoplankton responses in the subtropical deep freshwater ecosystem and typhoon passages in summer and autumn affected the phytoplankton dynamics differently. Nevertheless, sustained and systematic monitoring in order to advance our understanding of the role of typhoons between seasons in the modulation of

  11. Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

    Science.gov (United States)

    Galloway, Aaron W. E.; Winder, Monika

    2015-01-01

    Essential fatty acids (EFA), which are primarily generated by phytoplankton, limit growth and reproduction in diverse heterotrophs. The biochemical composition of phytoplankton is well-known to be governed both by phylogeny and environmental conditions. Nutrients, light, salinity, and temperature all affect both phytoplankton growth and fatty acid composition. However, the relative importance of taxonomy and environment on algal fatty acid content has yet to be comparatively quantified, thus inhibiting predictions of changes to phytoplankton food quality in response to global environmental change. We compiled 1145 published marine and freshwater phytoplankton fatty acid profiles, consisting of 208 species from six major taxonomic groups, cultured in a wide range of environmental conditions, and used a multivariate distance-based linear model to quantify the total variation explained by each variable. Our results show that taxonomic group accounts for 3-4 times more variation in phytoplankton fatty acids than the most important growth condition variables. The results underscore that environmental conditions clearly affect phytoplankton fatty acid profiles, but also show that conditions account for relatively low variation compared to phylogeny. This suggests that the underlying mechanism determining basal food quality in aquatic habitats is primarily phytoplankton community composition, and allows for prediction of environmental-scale EFA dynamics based on phytoplankton community data. We used the compiled dataset to calculate seasonal dynamics of long-chain EFA (LCEFA; ≥C20 ɷ-3 and ɷ-6 polyunsaturated fatty acid) concentrations and ɷ-3:ɷ-6 EFA ratios in Lake Washington using a multi-decadal phytoplankton community time series. These analyses quantify temporal dynamics of algal-derived LCEFA and food quality in a freshwater ecosystem that has undergone large community changes as a result of shifting resource management practices, highlighting diatoms

  12. The regrowth of phytoplankton cultures after UV disinfection

    International Nuclear Information System (INIS)

    Martínez, Lucía F.; Mahamud, Manuel M.; Lavín, Antonio G.; Bueno, Julio L.

    2013-01-01

    Highlights: ► Phytoplankton cultures were placed in a rich medium after UV-C irradiation. ► Flow cytometry and PAM were used for determining cell viability. ► The behavior differs from that of cultures kept in their original environment. ► Chlorella autotrophica recovers between 5 and 10 days after the treatment. ► Phaeocystis globosa shows only a slight recovery for low-dose UV-radiation exposure. - Abstract: This study addresses how cultures of three phytoplankton species –Chaetoceros calcitrans, Chlorella autotrophica and Phaeocystis globosa – can recover from the effects of UV-C exposure if the cells are placed in a rich medium. Flow cytometry and pulse amplitude modulation (PAM) were used to determine cell recovery after UV treatment. The recovery of C. calcitrans was complete 9 days after treatment. For C. autotrophica, the recovery was noticeable 5 days after treatment. P. globosa only recovered if the UV dose did not exceed 7.3 × 10 5 μWs/cm 2 . The recovery of the UV-treated cultures introduced to a regrowth medium, compared with the recovery of the irradiated cultures kept in their original environment, had two main characteristics: cell recovery was slower but was more efficient. This pattern of recovery has very important implications for real ballast water management systems because such systems discharge treated water into the environment

  13. Toxicity of lead and cadmium to tropical marine phytoplankton

    DEFF Research Database (Denmark)

    Jensen, Susanne Dal; Panutrakul, Suwanna; Nyholm, Niels

    2000-01-01

    Toxicity of Pb and Cd to three tropical, marine phytoplankton species isolated from the Andaman Sea off Phuket Thailand were determined. The phytoplankton species included one diatom, Chaetoceros calcitrans, one green alga, Chlorella sp., and one chrysophyte, Dunaliella tertiolecta. The test method...... white fluorescent light of a 10 to 12 klux intensity, and a 48 h test duration. Concentrations resulting in 50 percent reduced growth rate (EC50) were for C. calcitrans, Chlorella sp. and D. tertiolecta, respectively: Cd in artificial seawater: 3.28, 0.74, and 25.6 mg /L, and in natural seawater: 3.......02, 0.32, and 34.6 mg /L . EC50 values for Pb in artificial seawater were 1.4, 0.12, and 5.25 mg/L d and in natural seawater 0.18, 0.4 and 6.77 mg/L. Pb was consistently more toxic to the algae than Cd, and Chlorella sp was generally most sensitive followed by C. calcitrans while D. teriolecta...

  14. Southern Ocean phytoplankton physiology in a changing climate.

    Science.gov (United States)

    Petrou, Katherina; Kranz, Sven A; Trimborn, Scarlett; Hassler, Christel S; Ameijeiras, Sonia Blanco; Sackett, Olivia; Ralph, Peter J; Davidson, Andrew T

    2016-09-20

    The Southern Ocean (SO) is a major sink for anthropogenic atmospheric carbon dioxide (CO 2 ), potentially harbouring even greater potential for additional sequestration of CO 2 through enhanced phytoplankton productivity. In the SO, primary productivity is primarily driven by bottom up processes (physical and chemical conditions) which are spatially and temporally heterogeneous. Due to a paucity of trace metals (such as iron) and high variability in light, much of the SO is characterised by an ecological paradox of high macronutrient concentrations yet uncharacteristically low chlorophyll concentrations. It is expected that with increased anthropogenic CO 2 emissions and the coincident warming, the major physical and chemical process that govern the SO will alter, influencing the biological capacity and functioning of the ecosystem. This review focuses on the SO primary producers and the bottom up processes that underpin their health and productivity. It looks at the major physico-chemical drivers of change in the SO, and based on current physiological knowledge, explores how these changes will likely manifest in phytoplankton, specifically, what are the physiological changes and floristic shifts that are likely to ensue and how this may translate into changes in the carbon sink capacity, net primary productivity and functionality of the SO. Copyright © 2016 Elsevier GmbH. All rights reserved.

  15. Sustaining diversity in trait-based models of phytoplankton communities

    Directory of Open Access Journals (Sweden)

    Agostino eMerico

    2014-10-01

    Full Text Available It is well-established that when equilibrium is attained for two species competing for the same limiting resource in a stable, uniform environment, one species will eliminate the other due to competitive exclusion. While competitive exclusion is observed in laboratory experiments and ecological models, the phenomenon seems less common in nature, where static equilibrium is prevented by the fluctuating physical environment and by other factors that constantly change species abundances and the nature of competitive interactions. Trait-based models of phytoplankton communities appear to be useful tools for describing the evolution of large assemblages of species with aggregate group properties such as total biomass, mean trait, and trait variance, the latter representing the functional diversity of the community. Such an approach, however, is limited by the tendency of the trait variance to unrealistically decline to zero over time. This tendency to lose diversity, and therefore adaptive capacity, is typically solved by fixing the variance or by considering exogenous processes such as immigration. Exogenous processes, however, cannot explain the maintenance of adaptive capacity often observed in the closed environment of chemostat experiments. Here we present a new method to sustain diversity in adaptive trait-based models of phytoplankton communities based on a mechanism of trait diffusion through subsequent generations. Our modeling approach can therefore account for endogenous processes such as rapid evolution or transgenerational trait plasticity.

  16. Phytoplankton and nutrient dynamics in Winyah Bay, SC.

    Science.gov (United States)

    Boneillo, G. E.; Brooks, S. S.; Brown, S. L.; Woodford, K. M.; Wright, C. R.

    2016-02-01

    Winyah Bay is a coastal plain estuary located in South Carolina that has been classified for a moderate risk of Eutrophication by NOAA. Winyah Bay receives freshwater input from four rivers, the Waccamaw, Sampit, Black, and Pee Dee Rivers. The Waccamaw, Sampit and Black River are blackwater systems that discharge elevated amounts of colored dissolved organic matter. During the summer and fall of 2015, bioassay experiments were performed to simultaneously examine both light and nutrient (nitrogen & phosphate) limitation throughout Winyah Bay. Sampling stations near the mouth of the Waccamaw and Sampit Rivers showed that phytoplankton were light limited in the late summer instead of nutrient limited. These stations were located in the industrialized area of the bay and typically had the highest nutrient concentrations and highest turbidity, with Secchi depths typically less than 0.5 meters. Results indicated that phytoplankton may be nitrogen limited near the mouth of Winyah Bay, where nutrient concentrations and turbidity were observed to be lower than locations further upstream. There was also an observed dissolved oxygen and pH gradient during the summer of 2015. Dissolved oxygen levels less than 4.0 mg/L were routinely observed near the industrialized head of the estuary and corresponded with lower pH values.

  17. Paleolatitudinal Gradients in Marine Phytoplankton Composition and Cell Size

    Science.gov (United States)

    Henderiks, J.; Bordiga, M.; Bartol, M.; Šupraha, L.

    2014-12-01

    Coccolithophores, a prominent group of marine calcifying unicellular algae, are widely studied in context of current and past climate change. We know that marine phytoplankton are sensitive to climatic changes, but the complex interplay of several processes such as warming, changes in nutrient content, and ocean acidification, makes future scenarios difficult to predict. Some taxa may be more susceptible to environmental perturbations than others, as evidenced by significantly different species-specific sensitivities observed in laboratory experiments. However, short-term plastic responses may not translate into longer-term climatic adaptation, nor should we readily extrapolate the behavior of single strains in the laboratory to natural, multi-species assemblages and their interactions in the ocean. The extensive fossil record of coccolithophores (in the form of coccoliths) reveals high morphological and taxonomic diversity and allows reconstructing the cell size of individual taxonomic groups. In a suite of deep-sea drilling sites from the Atlantic Ocean, we document distinct latitudinal gradients in phytoplankton composition and cell size across major climate transitions of the late Eocene - earliest Oligocene, and the middle - late Miocene. With these data we test hypotheses of species migration, phenotypic evolution, as well as the rates of species extinction and speciation in relation to concurrent paleoenvironmental changes during the Cenozoic.

  18. In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics

    Directory of Open Access Journals (Sweden)

    Dana L. Wright

    2013-06-01

    Full Text Available Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger.

  19. Biological radiation dose estimation by chromosomal aberrations analysis in human peripheral blood (dose- effect curve)

    International Nuclear Information System (INIS)

    Al Achkar, W.

    2002-01-01

    In order to draw a dose-effect curve, blood from eight healthy people were studied. Samples were irradiated in tubes with 0.15-2.5 gray of gamma ray.Irradiated and control samples were incubated for cell cultures. Chromosomal aberrations from 67888 metaphases were scored. Curves from the total number of dicentrics, dicentrics+ rings and total numbers of breaks were drawn. The yield of chromosome aberrations is related to the dose used. These curves give a quick useful estimation of the accidentally radiation exposure. (author)

  20. Establishment and validation of a dose-effect curve for γ-rays by cytogenetic analysis

    International Nuclear Information System (INIS)

    Barquinero, Joan F.; Caballin, Maria Rosa; Barrios, Leonardo; Ribas, Montserrat; Miro, Rosa; Egozcue, Josep

    1995-01-01

    A dose-effect curve obtained by analysis of dicentric chromosomes after irradiation of peripheral blood samples, from one donor, at 11 different doses of γ-rays is presented. For the elaboration of this curve, more than 18,000 first division metaphases have been analyzed. The results fit very well to the linear-quadratic model. To validate the curve, samples from six individuals (three controls and three occupationally exposed persons) were irradiated at 2 Gy. The results obtained, when compared with the curve, showed that in all cases the 95% confidence interval included the 2 Gy dose, with estimated dose ranges from 1.82 to 2.19 Gy

  1. Phytoplankton community of Reis lake in the Brazilian Amazon

    Directory of Open Access Journals (Sweden)

    ISE G. SILVA

    2013-06-01

    Full Text Available Reis Lake is located in the municipality of Caracaraí, state of Roraima (Brazil and is subject to fluctuations in water level. The aim of this study was to analyze the structure of the phytoplankton community on the nictemeral and seasonal scales and determined the influence of limnological variables. Sampling was performed in the rainy season (June/2006 and dry season (November/2006, considering two nictemeral cycles. The phytoplankton community was assessed with regard to composition and density, abiotic variables were analyzed simultaneously. The lake had low concentrations of oxygen, clinograde profile and water stratified during the day and homogenous at night, with low concentrations of nutrients and waters ranging from slightly acidic to alkaline. The phytoplankton was represented by 43 taxa, 35 species in the dry season and 29 species in the rainy season. Low densities of phytoplankton occurred in both nictemeral cycles, with accentuated vertical gradient. The highest densities were recorded in the dry season. Reis Lake exhibits characteristics that classify it as a polymythic and oligotrophic environment. The variability in the data was more important seasonally than on the nictemeral scale, supporting the hypothesis of the influence of the hydrological cycle on the dynamics of phytoplankton communities in floodplain lakes.O lago dos Reis está localizado no município de Caracaraí, no estado de Roraima (Brasil e está sujeito a flutuações no nível da água. O objetivo do estudo foi analisar a estrutura da comunidade fitoplanctônica nas escalas nictemeral e sazonal e determinar a influência de variáveis limnológicas nesta comunidade. As amostragens foram realizadas nos periodos chuvoso e seco, considerando dois ciclos nictemeral. A comunidade fitoplanctônica foi avaliada no que diz respeito à composição e densidade, simultaneamente, variáveis abióticas foram analisadas. O lago apresentou baixas concentrações de oxig

  2. The effect of an asynchronous population of cells on the initial slope of dose-effect curves

    International Nuclear Information System (INIS)

    Chadwick, K.H.; Leenhouts, H.P.

    1975-01-01

    The molecular theory of cell survival gives an equation S = exp [ -p(αD + β D 2 )] which can be used to analyse dose-effect curves for synchronized cells. The variation in the coefficients α and β through the cell cycle has been found to be consistent for the different radiation types and is compatible with the induction of DNA double-strand breaks which is assumed in the theory to be the mechanism which is responsible for the biological effect. The theory predicts that low-LET radiation will have an initial slope, given by the coefficient α, and the consistency of the analysis of synchronized cell survival substantiates this prediction. In the molecular theory the induction of mutations has also been proposed to arise from DNA double-strand breaks and to be represented by the equation M = 1 - exp [-q(αD + β D 2 )]. This implies that at low doses of low-LET radiation the radiobiological effect will be linear with dose and that high-dose results may be analysed to provide estimates of the radiosensitivity of cells to low doses of radiation for radiological protection purposes. In an asynchronous population of cells it is possible that a small proportion of very radiosensitive cells can lead to significant deviations from this straightforward analysis. This 'Oftedal effect' is applied using the molecular theory to give a general theoretical relationship between the induction of mutations and cell survival. The theoretical relationship is compared with experimental data available from the literature. It is concluded that the initial slope of a mutation or cancer induction curve may be more relevant to the determination of the radiation sensitivity at low doses than the initial slope of a survival curve. (author)

  3. The light absorption by suspended particles, phytoplankton and dissolved organic matter in deep-and coastal waiters of the Black Sea impact on algorithms for remote sensing of chlorophyll -a-.

    Science.gov (United States)

    Churilova, T.; Suslin, V.; Berseneva, G.; Georgieva, L.

    At present time for the analysis and prediction of marine ecosystem state Chlorophyll and Primary production models based on optical satellite data are widely used. However, the SeaWiFS algorithms providing the transformation of color images to chlorophyll maps give inaccurate estimation of chlorophyll "a" (Chl "a") concentration in the Black Sea - an overestimation approximately two times in summer and an underestimation - ~1,5 times during the large diatom bloom in winter-spring. A development of the regional Chl "a" algorithm requires an estimation of spectral characteristics of all light absorbing components and their relationships with Chl "a" concentration. With this aim bio-optical monitoring was organized in two fixed stations in deep-water central western part of the Black Sea and in shelf waters near the Crimea. The weekly monitoring in deep-waters region allowed to determine phytoplankton community succession: seasonal dynamics of size and taxonomic structure, development of large diatoms blooming in March and coccolithophores - in June. The significant variability in pigment concentration and species content of phytoplankton is accompanied by high variability in shape of the phytoplankton absorption spectra and in values of chl a-specific absorption coefficients. This variability had seasonal character depending mostly on the optical status of phytoplankton cells and partly on taxonomic structure of phytoplankton. The pigment packaging parameter fluctuated from 0.64-0.68 (October-December) to 0.95-0.97 (April-May). The package effect depended on intracellular pigment concentration and the size and geometry of cells, which change significantly over the year, because of extremely different environmental conditions. The relationships between phytoplankton specific absorption coefficients (at 412, 443, 490, 510, 555, 678 nm) and Chl "a" concentration have been described by power functions. The contribution of detritus to total particulate absorption

  4. Radiation Dose Effects into LCO in Technical Specification by Iodine in Hanul units 1,2

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hye Min; Lee, Seung Chan [KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    This study estimates the impact of the 1-th coolant system in NPP to the LCO (Limiting Condition of Operation) limits which is in the site boundary. Dose limit is merged into the effective dose from whole body and thyroid dose limits, that is possible to combine the two LCOs to a unified LCO. To estimate the limits, the radiation dose of one of the designed accidents should be chosen to check the radiation dose response. The selected accident is based on Seung Chan Lee's study at KHNP in 2011. Using the selected accident, Iodine dose effect is reviewed depending on the LCO limiting responsibility and the specific behavior. In order to evaluate the radiation dose effect in Technical Specification of Hanul 1,2, SGTR is selected for some sensitivity analysis. From the results, in Hanul site, the case of LOOP plus ADV plus GIS is the most severe case and the dose limit margin is about 110% in LCO.

  5. Impacts of warming on phytoplankton abundance and phenology in a typical tropical marine ecosystem

    KAUST Repository

    Gittings, John; Raitsos, Dionysios E.; Krokos, George; Hoteit, Ibrahim

    2018-01-01

    In the tropics, thermal stratification (during warm conditions) may contribute to a shallowing of the mixed layer above the nutricline and a reduction in the transfer of nutrients to the surface lit-layer, ultimately limiting phytoplankton growth. Using remotely sensed observations and modelled datasets, we study such linkages in the northern Red Sea (NRS) - a typical tropical marine ecosystem. We assess the interannual variability (1998-2015) of both phytoplankton biomass and phenological indices (timing of bloom initiation, duration and termination) in relation to regional warming. We demonstrate that warmer conditions in the NRS are associated with substantially weaker winter phytoplankton blooms, which initiate later, terminate earlier and are shorter in their overall duration (~ 4 weeks). These alterations are directly linked with the strength of atmospheric forcing (air-sea heat fluxes) and vertical stratification (mixed layer depth [MLD]). The interannual variability of sea surface temperature (SST) is found to be a good indicator of phytoplankton abundance, but appears to be less important for predicting bloom timing. These findings suggest that future climate warming scenarios may have a two-fold impact on phytoplankton growth in tropical marine ecosystems: 1) a reduction in phytoplankton abundance and 2) alterations in the timing of seasonal phytoplankton blooms.

  6. Effects of Water Level Increase on Phytoplankton Assemblages in a Drinking Water Reservoir

    Directory of Open Access Journals (Sweden)

    Yangdong Pan

    2018-03-01

    Full Text Available Excessive water level fluctuation may affect physico-chemical characteristics, and consequently ecosystem function, in lakes and reservoirs. In this study, we assessed the changes of phytoplankton assemblages in response to water level increase in Danjiangkou Reservoir, one of the largest drinking water reservoirs in Asia. The water level increased from a low of 137 m to 161 m in 2014 as a part of the South–North Water Diversion Project. Phytoplankton assemblages were sampled four times per year before, during and after the water level increase, at 10 sites. Environmental variables such as total nitrogen as well as phytoplankton biomass decreased after the water level increase. Non-metric multi-dimensional scaling analysis indicated that before the water level increase, phytoplankton assemblages showed distinct seasonal variation with diatom dominance in both early and late seasons while such seasonal variation was much less evident after the water level increase. Month and year (before and after explained 13% and 6% of variance in phytoplankton assemblages (PERMANOVA, p < 0.001 respectively, and phytoplankton assemblages were significantly different before and after the water level increase. Both chlorophytes and cyanobacteria became more abundant in 2015. Phytoplankton compositional change may largely reflect the environmental changes, such as hydrodynamics mediated by the water level increase.

  7. Impacts of warming on phytoplankton abundance and phenology in a typical tropical marine ecosystem

    KAUST Repository

    Gittings, John

    2018-01-29

    In the tropics, thermal stratification (during warm conditions) may contribute to a shallowing of the mixed layer above the nutricline and a reduction in the transfer of nutrients to the surface lit-layer, ultimately limiting phytoplankton growth. Using remotely sensed observations and modelled datasets, we study such linkages in the northern Red Sea (NRS) - a typical tropical marine ecosystem. We assess the interannual variability (1998-2015) of both phytoplankton biomass and phenological indices (timing of bloom initiation, duration and termination) in relation to regional warming. We demonstrate that warmer conditions in the NRS are associated with substantially weaker winter phytoplankton blooms, which initiate later, terminate earlier and are shorter in their overall duration (~ 4 weeks). These alterations are directly linked with the strength of atmospheric forcing (air-sea heat fluxes) and vertical stratification (mixed layer depth [MLD]). The interannual variability of sea surface temperature (SST) is found to be a good indicator of phytoplankton abundance, but appears to be less important for predicting bloom timing. These findings suggest that future climate warming scenarios may have a two-fold impact on phytoplankton growth in tropical marine ecosystems: 1) a reduction in phytoplankton abundance and 2) alterations in the timing of seasonal phytoplankton blooms.

  8. Carbon budget of a marine phytoplankton-herbivore system with carbon-14 as a tracer

    International Nuclear Information System (INIS)

    Copping, A.E.; Lorenzen, C.J.

    1980-01-01

    Adult female and stage V Calanus pacificus were fed 14 C-labeled phytoplankton in the laboratory in the form of monospecific cultures and natural populations. A carbon budget was constructed by following the 14 C activity and the specific activity, over 48 h, in the phytoplankton, copepod, dissolved organic, dissolved inorganic, and fecal carbon compartments. The average incorporation of carbon into the copepod's body was 45% of the phytoplankton carbon available. Of the phytoplankton carbon, 27% appeared as dissolved organic carbon, 24% as dissolved inorganic carbon, and 3 to 4% in the form of fecal pellets. All of the tracer was recovered at the end of the experiments. The specific activity of the phytoplankton compartment was constant throughout each experiment. The other compartments had initial specific activities of zero, or close to zero, and increased throughout the experiment. In most experiments, the copepod specific activity equalled that of the phytoplankton at the end of 48 h, while the dissolved organic carbon, dissolved inorganic carbon, and fecal specific activities remained well below that of the phytoplankton

  9. Resource Supply Overrides Temperature as a Controlling Factor of Marine Phytoplankton Growth

    Science.gov (United States)

    Marañón, Emilio; Cermeño, Pedro; Huete-Ortega, María; López-Sandoval, Daffne C.; Mouriño-Carballido, Beatriz; Rodríguez-Ramos, Tamara

    2014-01-01

    The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting. Here we use concurrent measurements of phytoplankton biomass and carbon fixation rates in polar, temperate and tropical regions to determine the role of temperature and resource supply in controlling the large-scale variability of in situ metabolic rates. We identify a biogeographic pattern in phytoplankton metabolic rates, which increase from the oligotrophic subtropical gyres to temperate regions and then coastal waters. Variability in phytoplankton growth is driven by changes in resource supply and appears to be independent of seawater temperature. The lack of temperature sensitivity of realized phytoplankton growth is consistent with the limited applicability of Arrhenius enzymatic kinetics when substrate concentrations are low. Our results suggest that, due to widespread resource limitation in the ocean, the direct effect of sea surface warming upon phytoplankton growth and productivity may be smaller than anticipated. PMID:24921945

  10. Using photopigment biomarkers to quantify sub-lethal effects of petroleum pollution on natural phytoplankton assemblages

    International Nuclear Information System (INIS)

    Swistak, J.; Pinckney, J.; Piehler, M.; Paerl, H.

    1995-01-01

    Although much work has been undertaken to determine the toxicity of petroleum pollutants to phytoplankton, most studies have used pure cultures to monitor growth of selected phytoplankton species. Fewer have considered the net effect on entire microalgal communities. Using high performance liquid chromatography (HPLC) to characterize diagnostic microalgal pigments, the authors were able to simultaneously assess sub-lethal pollutant effects on entire communities as well as on individual phytoplankton functional groups. Incubations of natural water samples with diesel fuel, an important contributor to coastal petroleum pollution, revealed significant changes in photopigments and relative abundance of taxonomic groups at sub-lethal concentrations. Differential rates of change of indicator pigment concentrations suggest a range of sensitivity among phytoplankton groups. In preliminary experiments, cyanobacteria exhibited the greatest overall tolerance to the diesel fuel concentrations tested, while cryptomonads displayed the most sensitivity. The authors are currently evaluating the responses of seasonal phytoplankton populations from 3 sites exposed to varied levels of petroleum pollution. HPLC will be used to characterize phytoplankton populations and to determine if the most abundant groups are also the most tolerant of diesel fuel. Preliminary experiments indicate that diesel fuel pollution may modify the structure and function of phytoplankton communities and subsequently alter the trophodynamics of impacted systems

  11. Response of phytoplankton to an experimental fish culture in net cages in a subtropical reservoir.

    Science.gov (United States)

    Bartozek, E C R; Bueno, N C; Feiden, A; Rodrigues, L C

    2016-01-01

    This study aimed to evaluate nutrients concentration and spatial-temporal changes in phytoplankton biovolume during an experimental fish culture in net cages in a lateral arm of Salto Caxias reservoir, Brazil. Two sampling stations were placed in the affected lateral arm and other two in a cageless lateral arm. Neither abiotic variables nor phytoplankton biovolume presented significant differences between the treatments. Only temporal changes were confirmed by the analysis performed. Both lateral arms were classified as oligotrophic, reflecting low influence of the net cages. Phytoplankton growth seems to be limited by nitrogen. Biovolume values were, in general, low and five major functional groups were recognized (E, F, G, K and P). In summer higher biovolume values were observed and representatives of Chlorophyceae and Cyanobacteria belonging to the functional groups F and K, respectively, were the most important. In winter phytoplankton was mainly composed by Bacillariophyceae taxa from P group. G group was also restricted to winter and E group occurred in winter and summer. The variations recorded in phytoplankton structure appear to have been mainly influenced by seasonal changes in temperature, precipitation and nutrients availability. The effects of net cages on the abiotic variables and phytoplankton biovolume appear to have been small, probably due to the small number of net cages employed and the system dilution capacity. However, a permanent monitoring of phytoplankton is recommended, since this environment has a carrying capacity, from which the trophic state may increase.

  12. Enhanced crude oil biodegradative potential of natural phytoplankton-associated hydrocarbonoclastic bacteria.

    Science.gov (United States)

    Thompson, Haydn; Angelova, Angelina; Bowler, Bernard; Jones, Martin; Gutierrez, Tony

    2017-07-01

    Phytoplankton have been shown to harbour a diversity of hydrocarbonoclastic bacteria (HCB), yet it is not understood how these phytoplankton-associated HCB would respond in the event of an oil spill at sea. Here, we assess the diversity and dynamics of the bacterial community associated with a natural population of marine phytoplankton under oil spill-simulated conditions, and compare it to that of the free-living (non phytoplankton-associated) bacterial community. While the crude oil severely impacted the phytoplankton population and was likely conducive to marine oil snow formation, analysis of the MiSeq-derived 16S rRNA data revealed dramatic and differential shifts in the oil-amended communities that included blooms of recognized HCB (e.g., Thalassospira, Cycloclasticus), including putative novel phyla, as well as other groups with previously unqualified oil-degrading potential (Olleya, Winogradskyella, and members of the inconspicuous BD7-3 phylum). Notably, the oil biodegradation potential of the phytoplankton-associated community exceeded that of the free-living community, and it showed a preference to degrade substituted and non-substituted polycyclic aromatic hydrocarbons. Our study provides evidence of compartmentalization of hydrocarbon-degrading capacity in the marine water column, wherein HCB associated with phytoplankton are better tuned to degrading crude oil hydrocarbons than that by the community of planktonic free-living bacteria. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  13. Effects of nutrients, temperature and their interactions on spring phytoplankton community succession in Lake Taihu, China.

    Directory of Open Access Journals (Sweden)

    Jianming Deng

    Full Text Available We examined the potential effects of environmental variables, and their interaction, on phytoplankton community succession in spring using long-term data from 1992 to 2012 in Lake Taihu, China. Laboratory experiments were additionally performed to test the sensitivity of the phytoplankton community to nutrient concentrations and temperature. A phytoplankton community structure analysis from 1992 to 2012 showed that Cryptomonas (Cryptophyta was the dominant genus in spring during the early 1990s. Dominance then shifted to Ulothrix (Chlorophyta in 1996 and 1997. However, Cryptomonas again dominated in 1999, 2000, and 2002, with Ulothrix regaining dominance from 2003 to 2006. The bloom-forming cyanobacterial genus Microcystis dominated in 1995, 2001 and 2007-2012. The results of ordinations indicated that the nutrient concentration (as indicated by the trophic state index was the most important factor affecting phytoplankton community succession during the past two decades. In the laboratory experiments, shifts in dominance among phytoplankton taxa occurred in all nutrient addition treatments. Results of both long term monitoring and experiment indicated that nutrients exert a stronger control than water temperature on phytoplankton communities during spring. Interactive effect of nutrients and water temperature was the next principal factor. Overall, phytoplankton community composition was mediated by nutrients concentrations, but this effect was strongly enhanced by elevated water temperatures.

  14. Phytoplankton and water quality in a Mediterranean drinking-water reservoir (Marathonas Reservoir, Greece).

    Science.gov (United States)

    Katsiapi, Matina; Moustaka-Gouni, Maria; Michaloudi, Evangelia; Kormas, Konstantinos Ar

    2011-10-01

    Phytoplankton and water quality of Marathonas drinking-water Reservoir were examined for the first time. During the study period (July-September 2007), phytoplankton composition was indicative of eutrophic conditions although phytoplankton biovolume was low (max. 2.7 mm³ l⁻¹). Phytoplankton was dominated by cyanobacteria and diatoms, whereas desmids and dinoflagellates contributed with lower biovolume values. Changing flushing rate in the reservoir (up to 0.7% of reservoir's water volume per day) driven by water withdrawal and occurring in pulses for a period of 15-25 days was associated with phytoplankton dynamics. Under flushing pulses: (1) biovolume was low and (2) both 'good' quality species and the tolerant to flushing 'nuisance' cyanobacterium Microcystis aeruginosa dominated. According to the Water Framework Directive, the metrics of phytoplankton biovolume and cyanobacterial percentage (%) contribution indicated a moderate ecological water quality. In addition, the total biovolume of cyanobacteria as well as the dominance of the known toxin-producing M. aeruginosa in the reservoir's phytoplankton indicated a potential hazard for human health according to the World Health Organization.

  15. Phytoplankton assemblage of a small, shallow, tropical African reservoir

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    Moshood K Mustapha

    2009-12-01

    Full Text Available I measured physico-chemical properties and phytoplankton in the small, shallow tropical reservoir of Oyun (Offa, Nigeria between January 2002 and December 2003. I identified 25 phytoplankton genera in three sampling stations. Bacillariophyceae dominated (75.3%, followed by Chlorophyceae (12.2%, Cyanobacteria (11.1% and Desmidiaceae (0.73%. The high amount of nutrients (e.g. nitrate, phosphate, sulphate and silica explain phytoplankton heterogeneity (pInvestigué las propiedades físico-químicas y el fitoplancton del pequeño embalse tropical Oyun (Offa, Nigeria entre enero de 2002 y diciembre de 2003, para determinar el efecto de las propiedades físico-químicas en el fitoplancton y la producción de peces. En las tres estaciones estudiadas identifiqué 25 géneros de fitoplancton pertenecientes a cuatro clases. Bacillariophyceae dominó (75.3%, seguida de Chlorophyceae (12.2%, Desmidiaceae (11.1% y Cianobacteria (0.73%. La gran cantidad de nutrientes (e.g. nitrato, fosfato, sulfato y sílice explica la heterogeneidad del fitoplancton (p<0.05, el cual fue abundante durante la época de lluvias. La zona de transición de la reserva tuvo el conjunto más rico y abundante. Las fluctuaciones en la densidad del fitoplancton fueron resultado de la concentración estacional de los nutrientes, la presión del forrajeo y la hidrología. El embalse es eutrófico con agua excelente y fitoplancton diverso, y por tanto su producción pesquera sería alta. Estas condiciones son consecuencia de estrategias como mejores prácticas de gestión de cuencas (BPM para controlar la eutroficación y la sedimentación, y el establecimiento de prioridades legales para un buen uso del agua. Recomiendo medidas adicionales contra la oligotrofía, la hipereutrofia, el exceso de fitoplancton, las cianobacterias tóxicas, las escorrentías de residuos orgánicos y el exceso de sales disueltas.

  16. Phytoplankton variability in Lake Fraijanes, Costa Rica, in response to local weather variation

    Directory of Open Access Journals (Sweden)

    Gerardo Umaña-Villalobos

    2014-08-01

    Full Text Available Phytoplankton species show a variety in morphology which is the result of adaptations to pelagic life including responses to fluctuations in water column dynamics driven by weather conditions. This has been reported in the oceans and in Northern temperate lakes. In order to observe whether tropical freshwater phytoplankton responds to seasonal variation in weather, the weekly variation in temperature of the water column and phytoplankton composition was studied in Lake Fraijanes, Costa Rica, a shallow (6.2m lake at 1 640m above sea level. A chain of data loggers for temperature was placed in the deepest point in the lake to register temperature every hour at four different depths, and phytoplankton samples were retrieved every week for a year. Additional monthly samples for nutrients were taken at two depths. Notwithstanding its shallowness, the lake developed a thermal gradient which kept the water column stratified for several months during dry season. Whole lake overturns occurred during cold spells with intense precipitation. Phytoplankton changed throughout the year mainly through a shift in dominant taxa. From September to February the lake was frequently mixed by rain storms and windy weather. At this time, phytoplankton was dominated by Chlorococcal green algae. From March to June, the lake was stratified and warmer. Phytoplankton became dominated by Cyanobateria, mainly colonial Chroococcales. The rainy season started again in May 2009. During June and July the lake started to mix intermittently during rain events and phytoplankton showed a brief increase in the contribution of Chlorococcales. These changes fitted well to a general model of phytoplankton succession based on functional groups identified according to their morphology and adaptations.

  17. Recognition of key regions for restoration of phytoplankton communities in the Huai River basin, China

    Science.gov (United States)

    Zhao, Changsen; Liu, Changming; Xia, Jun; Zhang, Yongyong; Yu, Qiang; Eamus, Derek

    2012-02-01

    SummaryHealthy phytoplankton communities are the basis of healthy water ecosystems, and form the foundation of many freshwater food webs. Globally many freshwater ecosystems are degraded because of intensive human activities, so water ecosystem restoration is a burning issue worldwide. Selection of key regions for phytoplankton-related restoration is crucial for an effective aquatic eco-restoration. This paper presents a practical method for identification of key regions for phytoplankton-related restoration, using random forests (RFs) method to cluster sites based on dominance, biodiversity, water chemistry and ecological niche. We sampled phytoplankton for species richness and relative abundance and water quality in the Huai River basin (HRB), China to determine the phytoplankton communities' composition and structure and characterize of their ecological niches. A wider mean niche breadth of a species usually leads to a greater overlap with the niche of other species. Using these data and water quality indices, we identified the key regions for phytoplankton-related river restoration activities. Results indicate that our method for recognition of key regions is effective and practical and its application to the HRB identified the Northern Plain area as the key region for restoration. This area is severely polluted and contributes significantly to the HRB phytoplankton communities. Phytoplankton in this region is highly adaptable to environmental change and therefore will be relatively unharmed by environmental instability induced by restoration measures. During restoration, indices of water temperature, total phosphorus and chemical oxygen demand can be altered with little negative influence on phytoplankton communities, but measures that increase ammonia-nitrogen concentration would be highly detrimental. These results will provide valuable information for policy makers and stakeholders in water ecosystem restoration and sustainable basin management in the HRB.

  18. Phytoplankton blooms: an overlooked marine source of natural endocrine disrupting chemicals.

    Science.gov (United States)

    Gong, Yinhan; Wang, Xiaochong; Indran, Inthrani Raja; Zhang, Shi-Jun; Lv, Zhengbing; Li, Jun; Holmes, Michael; Tang, Ying Zhong; Yong, E L

    2014-09-01

    We had previously reported high androgenic and estrogenic activities in seawaters in confined clusters close to Singapore. Further investigations revealed a hitherto unsuspected link between estrogenic/androgenic activity and net phytoplankton count. The primary objective of this study was to investigate the cause of a correlation between net phytoplankton and endocrine activity, and corroborate this observation, and rule out other possible confounding factors. Our secondary objective was to study if these estrogenic secretions can impact human health. Five species of phytoplankton, Gymnodinium catenatum, Prorocentrum minimum, Alexandrium leei, Chattonella marina, and Fibrocapsa japonica, were isolated from Singapore waters and mass cultured and the cells and culture media screened for estrogenic and androgenic activity using human cell-based bioassays. The raphidophytes C. marina and F. japonica displayed significant estrogenic activity whilst the dinoflagellates G. catenatum and P. minimum displayed significant androgenic activity in both the cell extracts and the cell culture media extract. Our data shows that selected phytoplankton isolates are potent secretors of estrogenic and androgenic substances, which are potential endocrine disrupting chemicals (EDCs). As the harmful nature of EDCs is largely due to their bioaccumulation in the aquatic food chain our findings imply that the impact of these phytoplankton secretions needs to be investigated especially for seafoods, which are only a single trophic level away from phytoplankton. Alternatively, should these phytoplankton-origin EDCs not accumulate through marine food chains to significantly impact humans or marine mammals, our results indicate that functional assays could greatly over-estimate the risk from naturally occurring EDCs produced by marine phytoplankton. It remains to be determined if these EDCs affect zooplankton and other organisms that directly feed on marine phytoplankton, or if the secreted

  19. Dysphagia After Chemoradiotherapy for Head-and-Neck Squamous Cell Carcinoma: Dose-Effect Relationships for the Swallowing Structures

    International Nuclear Information System (INIS)

    Dirix, Piet; Abbeel, Sarah; Vanstraelen, Bianca; Hermans, Robert; Nuyts, Sandra

    2009-01-01

    Purpose: To evaluate late dysphagia after chemoradiotherapy for locally advanced head-and-neck squamous cell carcinoma, and to examine its correlation with clinical and dosimetric parameters. Methods and Materials: Consecutive patients, treated with radiotherapy (70-72 Gy) and concomitant chemotherapy (cisplatinum 100 mg/m 2 every 3 weeks) between 2004 and 2007, were examined. Swallowing was evaluated by four quality-of-life questionnaires: EORTC C30 and H and N35, the Performance Status Scale of List, and the MD Anderson Dysphagia Inventory. Clinical and dosimetric parameters were correlated with late dysphagia. Results: A total of 53 disease-free patients were evaluated; mean follow-up was 20.4 months (range, 6-45 months). The volume of the middle pharyngeal constrictor muscle receiving ≥50 Gy (p = 0.04), the mean dose to this structure (p = 0.02) and to the supraglottic larynx (p = 0.04) were significantly associated with late swallowing problems at univariate analysis, along with tumor localization (p = 0.008), T-classification (p = 0.02), and pretreatment swallowing problems (p = 0.01). Only this last factor significantly correlated with late dysphagia at multivariate analysis. Conclusion: These findings motivate further efforts to reduce the dose to the swallowing structures, especially to the pharyngeal constrictor muscles and the larynx. However, clinical parameters are also important and should be included in future prospective trials.

  20. Study of dose effect relationship at low doses for non quantitative reactions of skin intestinal mucosa and lung

    International Nuclear Information System (INIS)

    Dutreix, J.; Wambersie, A.

    1977-01-01

    Most of the biological reactions observed in animal experiments or in clinical studies are non quantitative and they only allow assessing an inequality between the effects produced by different irradiations. The method used in non quantitative studies is actually based on the relative contribution of irreparable events and reparable to the cell killing. It provides for the cell population involved in non quantitative biological effects some data which can be expressed in term of a cell survival curve. Such data can be useful in Radiation therapy particularly for maximizing the difference between biological effects by a proper choice of the fraction size. The initial part of the cell survival curve, within the range of doses actually used appears to be a straight exponential. This should allow the extrapolation to very low doses in the range of interest to Radiation Protection

  1. Evaluation of the Cerebral State Index in Cats under Isoflurane Anaesthesia: Dose-Effect Relationship and Prediction of Clinical Signs

    Directory of Open Access Journals (Sweden)

    Joana R. Sousa

    2014-01-01

    Full Text Available The performance of the cerebral state index (CSI in reflecting different levels of isoflurane anaesthesia was evaluated in ten cats subjected to four end-tidal isoflurane concentrations (EtIso, each maintained for 15 minutes (0.8%, 1.2%, 1.6%, or 2.0% EtIso. The CSI, hemodynamic data, ocular reflexes, and eye position were recorded for each EtIso concentration. Pharmacodynamic analysis of CSI with EtIso was performed, as well as prediction probability analysis with a clinical scale based on the eye reflexes. The CSI values showed great variability. Between all parameters, burst suppression ratio showed the better fitting with the sigmoidal concentration-effect model (R2=0.93 followed by CSI (R2=0.82 and electromyographic activity (R2=0.79. EtIso was the variable with better prediction of the clinical scale of anaesthesia (prediction probability value of 0.94. Although the CSI values decrease with increasing isoflurane concentrations, the huge variability in CSI values may be a strong limitation for its use in cats and it seems to be no better than EtIso as a predictor of clinical signs.

  2. Individual Cell Based Traits Obtained by Scanning Flow-Cytometry Show Selection by Biotic and Abiotic Environmental Factors during a Phytoplankton Spring Bloom

    Science.gov (United States)

    Pomati, Francesco; Kraft, Nathan J. B.; Posch, Thomas; Eugster, Bettina; Jokela, Jukka; Ibelings, Bas W.

    2013-01-01

    In ecology and evolution, the primary challenge in understanding the processes that shape biodiversity is to assess the relationship between the phenotypic traits of organisms and the environment. Here we tested for selection on physio-morphological traits measured by scanning flow-cytometry at the individual level in phytoplankton communities under a temporally changing biotic and abiotic environment. Our aim was to study how high-frequency temporal changes in the environment influence biodiversity dynamics in a natural community. We focused on a spring bloom in Lake Zurich (Switzerland), characterized by rapid changes in phytoplankton, water conditions, nutrients and grazing (mainly mediated by herbivore ciliates). We described bloom dynamics in terms of taxonomic and trait-based diversity and found that diversity dynamics of trait-based groups were more pronounced than those of identified phytoplankton taxa. We characterized the linkage between measured phytoplankton traits, abiotic environmental factors and abundance of the main grazers and observed weak but significant correlations between changing abiotic and biotic conditions and measured size-related and fluorescence-related traits. We tested for deviations in observed community-wide distributions of focal traits from random patterns and found evidence for both clustering and even spacing of traits, occurring sporadically over the time series. Patterns were consistent with environmental filtering and phenotypic divergence under herbivore pressure, respectively. Size-related traits showed significant even spacing during the peak of herbivore abundance, suggesting that morphology-related traits were under selection from grazing. Pigment distribution within cells and colonies appeared instead to be associated with acclimation to temperature and water chemistry. We found support for trade-offs among grazing resistance and environmental tolerance traits, as well as for substantial periods of dynamics in which

  3. Phytoplankton diversity of the Gharni Reservoir in Latur district, Maharashtra, India

    Directory of Open Access Journals (Sweden)

    Vishwas Balasaheb Sakhare

    2015-08-01

    Full Text Available The phytoplanktonic samples were collected from the Gharni Reservoir of Latur district of Maharashtra for a period of one year, from June 2013 to May 2014. Totally 18 species of phytoplankton belonging to different taxonomic groups were identified. Among these 7 species belong to Chlorophyceae, 5 species to Cyanophyceae, 3 species to Bacillariophyceae and 3 species to Euglenophyceae. The phytoplankton productivity fluctuated seasonally and the maximum number of 560 units/liter was recorded during month of February and March and minimum number of 95 units/liter during the month of September.

  4. A major seasonal phytoplankton bloom in the Madagascar Basin

    Science.gov (United States)

    Longhurst, Alan

    2001-11-01

    A hitherto-unnoticed phytoplankton bloom, of dimension 3000×1500 km, occupies the Madagascar Basin in late austral summer, being a prominent feature in SeaWiFS images. A first-order interpretation of the bloom mechanism invokes the seasonal deepening of the mixed layer within a strong mesoscale eddy-field and the consequent entrainment of nutrients into the photic zone. Features of the bloom correspond closely and appropriately with features of the eddy-field as observed by TOPEX-POSEIDON sea level anomalies. The bloom failed to develop in 1998, the second year of a two-year ENSO episode, when anomalously weak Southeast Trades will have failed to deepen the mixed layer as in other years.

  5. Hierarchical clusters of phytoplankton variables in dammed water bodies

    Science.gov (United States)

    Silva, Eliana Costa e.; Lopes, Isabel Cristina; Correia, Aldina; Gonçalves, A. Manuela

    2017-06-01

    In this paper a dataset containing biological variables of the water column of several Portuguese reservoirs is analyzed. Hierarchical cluster analysis is used to obtain clusters of phytoplankton variables of the phylum Cyanophyta, with the objective of validating the classification of Portuguese reservoirs previewly presented in [1] which were divided into three clusters: (1) Interior Tagus and Aguieira; (2) Douro; and (3) Other rivers. Now three new clusters of Cyanophyta variables were found. Kruskal-Wallis and Mann-Whitney tests are used to compare the now obtained Cyanophyta clusters and the previous Reservoirs clusters, in order to validate the classification of the water quality of reservoirs. The amount of Cyanophyta algae present in the reservoirs from the three clusters is significantly different, which validates the previous classification.

  6. Increased exposure of Southern Ocean phytoplankton to ultraviolet radiation

    Science.gov (United States)

    Lubin, Dan; Arrigo, Kevin R.; van Dijken, Gert L.

    2004-05-01

    Satellite remote sensing of both surface solar ultraviolet radiation (UVR) and chlorophyll over two decades shows that biologically significant ultraviolet radiation increases began to occur over the Southern Ocean three years before the ozone ``hole'' was discovered. Beginning in October 1983, the most frequent occurrences of enhanced UVR over phytoplankton-rich waters occurred in the Weddell Sea and Indian Ocean sectors of the Southern Ocean, impacting 60% of the surface biomass by the late 1990s. These results suggest two reasons why more serious impacts to the base of the marine food web may not have been detected by field experiments: (1) the onset of UVR increases several years before dedicated field work began may have impacted the most sensitive organisms long before such damage could be detected, and (2) most biological field work has so far not taken place in Antarctic waters most extensively subjected to enhanced UVR.

  7. Evolution of phytoplankton cultures after ultraviolet light treatment

    International Nuclear Information System (INIS)

    Martínez, L.F.; Mahamud, M.M.; Lavín, A.G.; Bueno, J.L.

    2012-01-01

    Introducing invasive species in new environments through ballast water is a specific problem of contamination and has recently become one of the main concerns of Maritime Organizations. Ultraviolet-C radiation (UV-C) is a technological alternative to prevent this maritime pollution. This study addresses the effect of UV-C on different phytoplankton cultures and also the ability to recover following exposure to damage. A UV-C low-pressure lamp irradiates the cultures. The distance from the source and the thickness of the layer prevent part of the energy from reaching the culture and the disinfective process is diminished. Some cultures such as Chlorella autotrophica and Chaetoceros calcitrans can easily recover from UV-C damage. However, Phaeocystis globosa does not have this ability. C. calcitrans forms cysts and exhibits two different behaviours depending on the dose applied.

  8. Climate effects on phytoplankton floral composition in Chesapeake Bay

    Science.gov (United States)

    Harding, L. W.; Adolf, J. E.; Mallonee, M. E.; Miller, W. D.; Gallegos, C. L.; Perry, E. S.; Johnson, J. M.; Sellner, K. G.; Paerl, H. W.

    2015-09-01

    Long-term data on floral composition of phytoplankton are presented to document seasonal and inter-annual variability in Chesapeake Bay related to climate effects on hydrology. Source data consist of the abundances of major taxonomic groups of phytoplankton derived from algal photopigments (1995-2004) and cell counts (1985-2007). Algal photopigments were measured by high-performance liquid chromatography (HPLC) and analyzed using the software CHEMTAX to determine the proportions of chlorophyll-a (chl-a) in major taxonomic groups. Cell counts determined microscopically provided species identifications, enumeration, and dimensions used to obtain proportions of cell volume (CV), plasma volume (PV), and carbon (C) in the same taxonomic groups. We drew upon these two independent data sets to take advantage of the unique strengths of each method, using comparable quantitative measures to express floral composition for the main stem bay. Spatial and temporal variability of floral composition was quantified using data aggregated by season, year, and salinity zone. Both time-series were sufficiently long to encompass the drought-flood cycle with commensurate effects on inputs of freshwater and solutes. Diatoms emerged as the predominant taxonomic group, with significant contributions by dinoflagellates, cryptophytes, and cyanobacteria, depending on salinity zone and season. Our analyses revealed increased abundance of diatoms in wet years compared to long-term average (LTA) or dry years. Results are presented in the context of long-term nutrient over-enrichment of the bay, punctuated by inter-annual variability of freshwater flow that strongly affects nutrient loading, chl-a, and floral composition. Statistical analyses generated flow-adjusted diatom abundance and showed significant trends late in the time series, suggesting current and future decreases of nutrient inputs may lead to a reduction of the proportion of biomass comprised by diatoms in an increasingly diverse

  9. Taxonomic composition of phytoplankton in the Vakh River (Western Siberia)

    Science.gov (United States)

    Skorobogatova, O. N.

    2018-03-01

    This paper provides data on the hydrological and hydrochemical parameters of the Vakh River in the Middle Ob region. In 2005-2008 we have identified 404 taxonomic units represented by 463 species, types and forms of algae, belonging to 140 genera, 52 families, 13 classes and 7 divisions. 386 species were identified for the first time, 141 taxa were identified as rare and 22 taxa as new for Western Siberia. Leading divisions, Bacillariophyta and Chlorophyta, make up for 78.9% of total phytoplankton diversity. Cyanobacteria, Chrysophyta and Euglenophyta form a community of 88 taxonomic units having a rank lower than genus level, and represent 19.0% of the total number. The floral role of Xanthophyta and Dinophyta is insignificant (2.1%). The main structure-forming species are 14: vegetating throughout the year (Aulacoseira italica, Asterionella formosa), summer taxa (Microcystis aeruginosa, Melosira varians, Aulacoseira granulata, Pandorina morum, Pediastrum boryanum, P. duplex, Lacunastrum gracillimum, Scenedesmus quadricauda) and summer-autumn (Microcystis pulverea, Tabellaria fenestrata, T. flocculosa, Mucidosphaerium pulchellum). The Vakh River demonstrates specific characteristics of boreal flowing waterways. The northern composition is represented in a big rate of families (44.2%) and genera (109 77.9) with one to three species. The richest genera Closterium (31 taxa), Eunotia (27 taxa), Pinnularia (22 taxa), Desmidium (11 taxa) and the family Desmidiaceae (45 taxa) ensure diversity of phytoplankton. Ecological and geographical analysis demonstrates predominance of cosmopolitan algae (56.6%). Plankton represents 44.7% of all algae, oligogalobs - 78.8% and indifferent algae – 36.7%. Water meets the requirements for β-mezosaprobian pollution zone, class of satisfactory purity (III class).

  10. Phytoplankton from Lake Magelungen, Central Sweden 1960-1963

    Energy Technology Data Exchange (ETDEWEB)

    Willen, Torbjoern [Inst. of Limnology, Univ of Uppsala, Uppsala (Sweden)

    1966-03-15

    The investigation of the qualitative and quantitative composition of phytoplankton in Lake Magelungen, Central Sweden, was carried out over a period of three years to illustrate the conditions before the release of waste water from the Aagesta Heat and Power Station began. Vertical sampling series were taken about once a month and samples from three different stations (named MA, MOB and MH) in the lake were analysed and compared. Most importance was laid on the quantitative composition and the differences in total volumes between the different stations. Highest volume values were always recorded in late spring and in summer. Two algal groups predominated every year, viz. chlorophytes and cyanophytes. After a moderate spring outburst caused by diatoms (Stephanodiscus, Synedra and Asterionella) peak volume values of chlorophytes were recorded in June and July. Predominating genera were Scenedesmus, Coelastrum and Pediastrum. The chlorophyte maximum was always followed by an immense development of cyanophytes (Anabaena, Aphanizomenon and Microcystis). The diatoms were well developed only during short periods, the chrysophyceans were of little significance as were all other algal groups. A marked difference existed between the Station MOB compared with the two other stations. The water at Station MOB was more polluted and several algal genera indicating the pollution were recorded. Both chlorophytes and cyanophytes were often developed in very great quantities at this station. The total volumes of phytoplankton in Lake Magelungen already are very high and the lake is to be considered as highly eutrophic. It is very possible that changes as to further additions of nutritional elements or/and changes in the thermal balance will increase the algal populations and accelerate the normal development of the lake.

  11. Phytoplankton from Lake Magelungen, Central Sweden 1960-1963

    International Nuclear Information System (INIS)

    Willen, Torbjoern

    1966-03-01

    The investigation of the qualitative and quantitative composition of phytoplankton in Lake Magelungen, Central Sweden, was carried out over a period of three years to illustrate the conditions before the release of waste water from the Aagesta Heat and Power Station began. Vertical sampling series were taken about once a month and samples from three different stations (named MA, MOB and MH) in the lake were analysed and compared. Most importance was laid on the quantitative composition and the differences in total volumes between the different stations. Highest volume values were always recorded in late spring and in summer. Two algal groups predominated every year, viz. chlorophytes and cyanophytes. After a moderate spring outburst caused by diatoms (Stephanodiscus, Synedra and Asterionella) peak volume values of chlorophytes were recorded in June and July. Predominating genera were Scenedesmus, Coelastrum and Pediastrum. The chlorophyte maximum was always followed by an immense development of cyanophytes (Anabaena, Aphanizomenon and Microcystis). The diatoms were well developed only during short periods, the chrysophyceans were of little significance as were all other algal groups. A marked difference existed between the Station MOB compared with the two other stations. The water at Station MOB was more polluted and several algal genera indicating the pollution were recorded. Both chlorophytes and cyanophytes were often developed in very great quantities at this station. The total volumes of phytoplankton in Lake Magelungen already are very high and the lake is to be considered as highly eutrophic. It is very possible that changes as to further additions of nutritional elements or/and changes in the thermal balance will increase the algal populations and accelerate the normal development of the lake

  12. Enhancement of Transistor-to-Transistor Variability Due to Total Dose Effects in 65-nm MOSFETs

    CERN Document Server

    Gerardin, S; Cornale, D; Ding, L; Mattiazzo, S; Paccagnella, A; Faccio, F; Michelis, S

    2015-01-01

    We studied device-to-device variations as a function of total dose in MOSFETs, using specially designed test structures and procedures aimed at maximizing matching between transistors. Degradation in nMOSFETs is less severe than in pMOSFETs and does not show any clear increase in sample-to-sample variability due to the exposure. At doses smaller than 1 Mrad( SiO2) variability in pMOSFETs is also practically unaffected, whereas at very high doses-in excess of tens of Mrad( SiO2)-variability in the on-current is enhanced in a way not correlated to pre-rad variability. The phenomenon is likely due to the impact of random dopant fluctuations on total ionizing dose effects.

  13. The total dose effects on the 1/f noise of deep submicron CMOS transistors

    International Nuclear Information System (INIS)

    Hu Rongbin; Wang Yuxin; Lu Wu

    2014-01-01

    Using 0.18 μm CMOS transistors, the total dose effects on the 1/f noise of deep-submicron CMOS transistors are studied for the first time in mainland China. From the experimental results and the theoretic analysis, we realize that total dose radiation causes a lot of trapped positive charges in STI (shallow trench isolation) SiO 2 layers, which induces a current leakage passage, increasing the 1/f noise power of CMOS transistors. In addition, we design some radiation-hardness structures on the CMOS transistors and the experimental results show that, until the total dose achieves 750 krad, the 1/f noise power of the radiation-hardness CMOS transistors remains unchanged, which proves our conclusion. (semiconductor devices)

  14. Total dose effects on the matching properties of deep submicron MOS transistors

    International Nuclear Information System (INIS)

    Wang Yuxin; Hu Rongbin; Li Ruzhang; Chen Guangbing; Fu Dongbing; Lu Wu

    2014-01-01

    Based on 0.18 μm MOS transistors, for the first time, the total dose effects on the matching properties of deep submicron MOS transistors are studied. The experimental results show that the total dose radiation magnifies the mismatch among identically designed MOS transistors. In our experiments, as the radiation total dose rises to 200 krad, the threshold voltage and drain current mismatch percentages of NMOS transistors increase from 0.55% and 1.4% before radiation to 17.4% and 13.5% after radiation, respectively. PMOS transistors seem to be resistant to radiation damage. For all the range of radiation total dose, the threshold voltage and drain current mismatch percentages of PMOS transistors keep under 0.5% and 2.72%, respectively. (semiconductor devices)

  15. Phytoplankton pigments and functional community structure in relation to environmental factors in the Pearl River Estuary

    Directory of Open Access Journals (Sweden)

    Chao Chai

    2016-07-01

    Full Text Available Two cruises were undertaken in the Pearl River Estuary in November 2011 and March 2012 to analyze the distribution of phytoplankton pigments and to define the relationships of pigment indices and functional community structure with environmental factors. Among 22 pigments, 17 were detected by high-performance liquid chromatography. Chlorophyll a was found in all samples, with a maximum of 7.712 μg L−1 in spring. Fucoxanthin was the most abundant accessory pigment, with mean concentrations of 2.914 μg L−1 and 0.207 μg L−1 in spring and autumn, respectively. Chlorophyll a, chlorophyll c2, fucoxanthin, diadinoxanthin, and diatoxanthin were high in the northern or northwest estuary in spring and in the middle-eastern and northeast estuary in autumn. Chlorophyll b, chlorophyll c3, prasinoxanthin, and peridinin were similarly distributed during the two cruises. Chlorophyll a and fucoxanthin positively correlated with nutrients in spring, whereas 19′-hex-fucoxanthin and 19′-but-fucoxanthin negatively correlated. The biomass proportion of microphytoplankton (BPm was higher in spring, whereas that of picophytoplankton (BPp was higher in autumn. BPm in spring was high in areas with salinity 30. BPm increased but BPn reduced with the increase in nutrient contents. By comparison, BPp reduced with the increase in nutrient contents in spring, but no relationship was found between BPp and nutrient contents in autumn. The ratios of photosynthetic carotenoids to photoprotective carotenoids in the southern estuary approached unity linear relationship in spring and were under the unity line in autumn.

  16. Contribution of benthic microalgae to the temporal variation in phytoplankton assemblages in a macrotidal system.

    Science.gov (United States)

    Hernández Fariñas, Tania; Ribeiro, Lourenço; Soudant, Dominique; Belin, Catherine; Bacher, Cédric; Lampert, Luis; Barillé, Laurent

    2017-10-01

    Suspended marine benthic microalgae in the water column reflect the close relationship between the benthic and pelagic components of coastal ecosystems. In this study, a 12-year phytoplankton time-series was used to investigate the contribution of benthic microalgae to the pelagic system at a site along the French-Atlantic coast. Furthermore, all taxa identified were allocated into different growth forms in order to study their seasonal patterns. The highest contribution of benthic microalgae was observed during the winter period, reaching up to 60% of the carbon biomass in the water column. The haptobenthic growth form showed the highest contribution in terms of biomass, dominant in the fall-winter period when the turbidity and the river flow were high. The epipelic growth form did not follow any seasonal pattern. The epiphytic diatom Licmophora was most commonly found during summer. As benthic microalgae were found in the water column throughout the year, the temporal variation detected in the structure of pelagic assemblages in a macrotidal ecosystem was partly derived from the differentiated contribution of several benthic growth forms. © 2017 Phycological Society of America.

  17. Aragonite saturation state in a tropical coastal embayment dominated by phytoplankton blooms (Guanabara Bay - Brazil).

    Science.gov (United States)

    Cotovicz, Luiz C; Knoppers, Bastiaan A; Brandini, Nilva; Poirier, Dominique; Costa Santos, Suzan J; Abril, Gwenaël

    2018-04-01

    The dynamics of the aragonite saturation state (Ω arag ) were investigated in the eutrophic coastal waters of Guanabara Bay (RJ-Brazil). Large phytoplankton blooms stimulated by a high nutrient enrichment promoted the production of organic matter with strong uptake of dissolved inorganic carbon (DIC) in surface waters, lowering the concentrations of dissolved carbon dioxide (CO 2aq ), and increasing the pH, Ω arag and carbonate ion (CO 3 2- ), especially during summer. The increase of Ω arag related to biological activity was also evident comparing the negative relationship between the Ω arag and the apparent utilization of oxygen (AOU), with a very close behavior between the slopes of the linear regression and the Redfield ratio. The lowest values of Ω arag were found at low-buffered waters in regions that receive direct discharges from domestic effluents and polluted rivers, with episodic evidences of corrosive waters (Ω arag <1). This study showed that the eutrophication controlled the variations of Ω arag in Guanabara Bay. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Modeling the influence from ocean transport, mixing and grazing on phytoplankton diversity

    DEFF Research Database (Denmark)

    Adjou, Mohamed; Bendtsen, Jørgen; Richardson, Katherine

    2012-01-01

    Phytoplankton diversity, whether defined on the basis of functional groups or on the basis of numbers of individual species, is known to be heterogeneous throughout the global ocean. The factors regulating this diversity are generally poorly understood, although access to limiting nutrients...... in generating and maintaining diversity, we apply the model to quantify the potential role of zooplankton grazing and ocean transport for the coexistence of competing species and phytoplankton diversity. We analyze the sensitivity of phytoplankton biomass distributions to different types of grazing functional...... responses and show that preferential grazing on abundant species, for example as formulated by the Holling type III grazing function, is a key factor for maintaining species’ coexistence. Mixing and large-scale advection are shown to potentially have a significant impact on the distribution of phytoplankton...

  19. Warming accelerates termination of a phytoplankton spring bloom by fungal parasites

    NARCIS (Netherlands)

    Frenken, Thijs; Velthuis, M.; De Senerpont Domis, Lisette; Stephan, Susanne; Aben, Ralf Cornelis; Kosten, S.; van Donk, E.; Van de Waal, D.B.

    2016-01-01

    Climate change is expected to favour infectious diseases across ecosystems worldwide. In freshwater and marine environments, parasites play a crucial role in controlling plankton population dynamics. Infection of phytoplankton populations will cause a transfer of carbon and nutrients into parasites,

  20. Photochemical Production and Behavior of Hydroperoxyacids in Heterotrophic Bacteria Attached to Senescent Phytoplanktonic Cells

    Directory of Open Access Journals (Sweden)

    Frédéric Vaultier

    2013-06-01

    Full Text Available The photooxidation of cellular monounsaturated fatty acids was investigated in senescent phytoplanktonic cells (Emiliania huxleyi and in their attached bacteria under laboratory controlled conditions. Our results indicated that UV-visible irradiation of phytodetritus induced the photooxidation of oleic (produced by phytoplankton and bacteria and cis-vaccenic (specifically produced by bacteria acids. These experiments confirmed the involvement of a substantial singlet oxygen transfer from senescent phytoplanktonic cells to attached bacteria, and revealed a significant correlation between the concentration of chlorophyll, a photosensitizer, in the phytodetritus and the photodegradation state of bacteria. Hydroperoxyacids (fatty acid photoproducts appeared to be quickly degraded to ketoacids and hydroxyacids in bacteria and in phytoplanktonic cells. This degradation involves homolytic cleavage (most likely induced by UV and/or transition metal ions and peroxygenase activity (yielding epoxy acids.