Fish abundance and distribution near three heated effluents to Lake Michigan

International Nuclear Information System (INIS)

Spigarelli, S.A.; Goldstein, R.M.; Prepejchal, W.; Thommes, M.M.

1982-01-01

A combined echo location-temperature mapping technique was used to determine the abundance and distribution of fish with depth and temperature in locally heated and unheated areas of Lake Michigan. Surveys were conducted between April and October at two adjacent power plants in the southern basin and at one plant in the northern basin of the lake. Fish densities in plume and reference areas differed seasonally. Densities typically differed by a factor of 2-4 although on one occasion plume area density was 90 times greater. Highest plume densities occurred during late spring when alewife (Alosa pseudoharengus) were spawning inshore. Consistently dense congregations of fish were found downstream of the interfaces between ambient shore-parallel currents and discharge flows. The general distribution of fish with depth was similar in all areas. Differences between plume and reference areas were related to the discharge type: at canal discharges fish tended to congregate inshore while at the offshore discharge they congregated in deeper zones. Fish also tended to occupy shallower depth strata in all plume areas. Positive correlation between fish density and increasing temperature was common at both plume and reference areas during all three seasons, but more frequent at plume areas. Temperatures selected by fish in plume areas were 1-3 0 C higher than maximum ambient temperatures

Abundance of Dreissena polymorpha and Dreissena bugensis in a warmwater plume: effects of depth and temperature

Energy Technology Data Exchange (ETDEWEB)

Mitchell, J.S.; Bailey, R.C.; Knapton, R.W. [Simon Fraser University, Burnaby, BC (Canada). Department of Biological Sciences

1996-08-01

The abundance of mussel populations in areas affected by waste water discharges is examined. Measurements were made of the variation with depth in the abundance of zebra and of quagga mussels both inside and outside the area affected by the warm water plume from the Ontario Hydro Nanticoke coal-fired generating station on Lake Erie. The pattern of the residual variation relative to the warm water plume was then examined. The study allows a partial decoupling of depth and temperature effects. The results are discussed. 27 refs., 2 figs., 2 tabs.

Quantifying quagga mussel veliger abundance and distribution in Copper Basin Reservoir (California) using acoustic backscatter.

Science.gov (United States)

Anderson, Michael A; Taylor, William D

2011-11-01

Quagga mussels (Dreissena bugensis) have been linked to oligotrophication of lakes, alteration of aquatic food webs, and fouling of infrastructure associated with water supply and power generation, causing potentially billions of dollars in direct and indirect damages. Understanding their abundance and distribution is key in slowing their advance, assessing their potential impacts, and evaluating effectiveness of control strategies. Volume backscatter strength (Sv) measurements at 201- and 430-kHz were compared with quagga mussel veliger and zooplankton abundances determined from samples collected using a Wisconsin closing net from the Copper Basin Reservoir on the Colorado River Aqueduct. The plankton within the lower portion of the water column (>18 m depth) was strongly dominated by D-shaped quagga mussel veligers, comprising up to 95-99% of the community, and allowed direct empirical measurement of their mean backscattering cross-section. The upper 0-18 m of the water column contained a smaller relative proportion of veligers based upon net sampling. The difference in mean volume backscatter strength at these two frequencies was found to decrease with decreasing zooplankton abundance (r(2) = 0.94), allowing for correction of Sv due to the contribution of zooplankton and the determination of veliger abundance in the reservoir. Hydroacoustic measurements revealed veligers were often present at high abundances (up to 100-200 ind L(-1)) in a thin 1-2 m layer at the thermocline, with considerable patchiness in their distribution observed along a 700 m transect on the reservoir. Under suitable conditions, hydroacoustic measurements can rapidly provide detailed information on the abundance and distribution of quagga mussel veligers over large areas with high horizontal and vertical resolution. Copyright © 2011 Elsevier Ltd. All rights reserved.

Depth and substrate as determinants of distribution of juvenile flathead sole (Hippoglossoides elassodon) and rock sole (Pleuronectes bilineatus), in Kachemak Bay, Alaska

Science.gov (United States)

Abookire, Alisa A.; Norcross, Brenda L.

1998-01-01

Three transects in Kachemak Bay, Alaska, were sampled in September 1994, May and August 1995, and February, May, and August 1996. Juvenile flathead sole, Hippoglossoides elassodon, and rock sole, Pleuronectes bilineatus, were the most abundant flatfishes, comprising 65-85% of all fiatfishes captured at any period. Collections of fish and sediments were made at regular depth contour intervals of l0 m. Habitat distribution was described by depth at 10 m increments and sediment percent weights of gravel, sand, and mud. Year-round habitat of flathead sole age-0 was primarily from 40 to 60 m, and age-1 habitat was primarily from 40 to 80 m. Summer habitat of rock sole age-0 and -1 was from 10 to 30 m, and in winter they moved offshore to depths of up to 150 m. Both age classes of flathead sole were most abundant on mixed mud sediments, while age-1 were also in high abundance on muddy sand sediments. Rock sole age-0 and -1 were most abundant on sand, though age-1 were also found on a variety of sediments both finer and coarser grained than sand. Flathead sole and rock sole had distinctive depth and sediment habitats. When habitat overlap occurred between the species, it was most often due to rock sole moving offshore in the winter. Abundances were not significantly different among seasons for age-1 flatfishes.

A method to measure depth distributions of implanted ions

International Nuclear Information System (INIS)

Arnesen, A.; Noreland, T.

1977-04-01

A new variant of the radiotracer method for depth distribution determinations has been tested. Depth distributions of radioactive implanted ions are determined by dissolving thin, uniform layers of evaporated material from the surface of a backing and by measuring the activity before and after the layer removal. The method has been used to determine depth distributions for 25 keV and 50 keV 57 Co ions in aluminium and gold. (Auth.)

[Association of the abundance and vertical distribution of tuna and beakfish in the southeast of the Caribbean sea].

Science.gov (United States)

Eslava, Nora; González, Leo W; Gaertner, Daniel

2003-03-01

The longline hooks suspension depth was estimated using the Mechanic Imitation of Flexible Systems method. The vertical distribution of tunas and billfish was determined by the relative abundance index, obtained from the catch by 11 to 25 m -long longline vessels, -based at Cumaná, Venezuela, South-eastern Caribbean Sea in depths of 65 to 142 m. The CPUE was evaluated per species, according to depth. High values were found for most of the captured species in the layer from 105 to 125 m. Yellowfin tuna (Thunnus albacares) showed the highest yield (3.37 fish/100 hooks) and blue marlin (Makaira nigricans) the lowest (0.04 fish/100 hooks). However, the statistical comparison did not allow to reject the hypothesis of lack of depth efect (Kruskal-Wallis p > .05), and demonstrated a homogeneous distribution of yellowfin tuna (Thunnus albacares), albacore (Thunnus alalunga), bigeye tuna (Thunnus obesus), sailfish (Istiophorus albicans), white marlin (Tetrapturus albidus) and blue marlin (Makaira nigricans) in the water column. The conclusion is that fish concentration in the Southern border of the Caribbean Sea is possibly due to several hydroclimatic factors--which affect tuna and billfish catching--such as water temperature and dissolved oxygen concentration which limit the distribution according to depth.

Reproduction, distribution and abundance of Bothus constellatus (Pisces: Bothidae, in the Gulf of Tehuantepec, Mexico

Directory of Open Access Journals (Sweden)

M. Tapia-García

2000-03-01

Full Text Available A total of 3 593 individuals of Bothus constellatus was captured during five oceanographic cruises carried out in the Gulf of Tehuantepec, Mexico. Its distribution, abundance, and reproduction patterns were stated by means of the analysis of the population parameters (i.e. density, biomass, weight and size average, visceral and gonadosomatic index, and maturity stages. B. constellatus is a typical demersal marine species, because it does not occur in estuaries, but occurs near to them on the continental shelf. It is distributed in the Gulf of Tehuantepec in depths lesser than 60 m, with high abundance around the 40 m isobath, and in front of Mar Muerto Lagoon. During January and May the biomass and density were high. The size at first maturity of females is 101 mm total length, and maturation occurs first in zones influenced by estuarine processes. Reproduction and recruitment were detected in all the collections.

Estimating the relationship between abundance and distribution

DEFF Research Database (Denmark)

Rindorf, Anna; Lewy, Peter

2012-01-01

based on Euclidean distance to the centre of gravity of the spatial distribution. Only the proportion of structurally empty areas, Lloyds index, and indices of the distance to the centre of gravity of the spatial distribution are unbiased at all levels of abundance. The remaining indices generate...

Book review: A new view on the species abundance distribution

Science.gov (United States)

DeAngelis, Donald L.

2018-01-01

The sampled relative abundances of species of a taxonomic group, whether birds, trees, or moths, in a natural community at a particular place vary in a way that suggests a consistent underlying pattern, referred to as the species abundance distribution (SAD). Preston [1] conjectured that the numbers of species, plotted as a histogram of logarithmic abundance classes called octaves, seemed to fit a lognormal distribution; that is, the histograms look like normal distributions, although truncated on the left-hand, or low-species-abundance, end. Although other specific curves for the SAD have been proposed in the literature, Preston’s lognormal distribution is widely cited in textbooks and has stimulated attempts at explanation. An important aspect of Preston’s lognormal distribution is the ‘veil line’, a vertical line drawn exactly at the point of the left-hand truncation in the distribution, to the left of which would be species missing from the sample. Dewdney rejects the lognormal conjecture. Instead, starting with the long-recognized fact that the number of species sampled from a community, when plotted as histograms against population abundance, resembles an inverted J, he presents a mathematical description of an alternative that he calls the ‘J distribution’, a hyperbolic density function truncated at both ends. When multiplied by species richness, R, it becomes the SAD of the sample.

Compensating for geographic variation in detection probability with water depth improves abundance estimates of coastal marine megafauna.

Science.gov (United States)

Hagihara, Rie; Jones, Rhondda E; Sobtzick, Susan; Cleguer, Christophe; Garrigue, Claire; Marsh, Helene

2018-01-01

The probability of an aquatic animal being available for detection is typically probability of detection is important for obtaining robust estimates of the population abundance and determining its status and trends. The dugong (Dugong dugon) is a bottom-feeding marine mammal and a seagrass community specialist. We hypothesized that the probability of a dugong being available for detection is dependent on water depth and that dugongs spend more time underwater in deep-water seagrass habitats than in shallow-water seagrass habitats. We tested this hypothesis by quantifying the depth use of 28 wild dugongs fitted with GPS satellite transmitters and time-depth recorders (TDRs) at three sites with distinct seagrass depth distributions: 1) open waters supporting extensive seagrass meadows to 40 m deep (Torres Strait, 6 dugongs, 2015); 2) a protected bay (average water depth 6.8 m) with extensive shallow seagrass beds (Moreton Bay, 13 dugongs, 2011 and 2012); and 3) a mixture of lagoon, coral and seagrass habitats to 60 m deep (New Caledonia, 9 dugongs, 2013). The fitted instruments were used to measure the times the dugongs spent in the experimentally determined detection zones under various environmental conditions. The estimated probability of detection was applied to aerial survey data previously collected at each location. In general, dugongs were least available for detection in Torres Strait, and the population estimates increased 6-7 fold using depth-specific availability correction factors compared with earlier estimates that assumed homogeneous detection probability across water depth and location. Detection probabilities were higher in Moreton Bay and New Caledonia than Torres Strait because the water transparency in these two locations was much greater than in Torres Strait and the effect of correcting for depth-specific detection probability much less. The methodology has application to visual survey of coastal megafauna including surveys using Unmanned

Distribution and abundance of Eledone cirrhosa (Lamarck, 1798 and Eledone moschata (Lamarck, 1798 (Cephalopoda: Octopoda in the Mediterranean Sea

Directory of Open Access Journals (Sweden)

Paola Belcari

2002-06-01

Full Text Available Information on distribution, abundance and size composition of the two octopods Eledone cirrhosa and E. moschata was obtained from the MEDITS trawl surveys, carried out in a wide area of the Mediterranean basin from 1994 to 1999. Both species showed a wide geographic distribution, as they were collected in all the major areas investigated. E. cirrhosa showed a wide depth distribution, down to the 800 m isobath, while E. moschata was mostly restricted to within 200 m. Further analysis on spatio-temporal basis with a Generalised Linear Model, evidenced that differences among major areas, depth strata and their interaction were always significant. In the case of E. cirrhosa, differences among years and year-major area interaction were also significant. Two cohorts can be singled out in the size frequency distributions of E. cirrhosa, whereas only one mode can be clearly distinguished in most of the length distributions of E. moschata.

Water Table Depth Reconstruction in Ombrotrophic Peatlands Using Biomarker Abundance Ratios and Compound-Specific Hydrogen Isotope Composition

Science.gov (United States)

Nichols, J. E.; Jackson, S. T.; Booth, R. K.; Pendall, E. G.; Huang, Y.

2005-12-01

Sediment cores from ombrotrophic peat bogs provide sensitive records of changes in precipitation/evaporation (P/E) balance. Various proxies have been developed to reconstruct surface moisture conditions in peat bogs, including testate amoebae, plant macrofossils, and peat humification. Studying species composition of testate amoeba assemblages is time consuming and requires specialized training. Humification index can be influenced by environmental factors other than moisture balance. The plant macrofossil proxy is less quantitative and cannot be performed on highly decomposed samples. We demonstrate that the ratio of C23 alkane to C29 alkane abundance may provide a simple alternative or complementary means of tracking peatland water-table depth. Data for this proxy can be collected quickly using a small sample (100 mg dry). Water-table depth decreases during drought, and abundance of Sphagnum, the dominant peat-forming genus, decreases as vascular plants increase. Sphagnum moss produces mainly medium chain-length alkanes (C21-C25) while vascular plants (grasses and shrubs) produce primarily longer chain-length alkanes (C27-C31). Therefore, C23:C29 n-alkane ratios quantitatively track the water table depth fluctuations in peat bogs. We compared C23:C29 n-alkane ratios in a core from Minden Bog (southeastern Michigan) with water table depth reconstructions based on testate-amoeba assemblages and humification. The 184-cm core spans the past ~3kyr of continuous peat deposition in the bog. Our results indicate that the alkane ratios closely track the water table depth variations, with C29 most abundant during droughts. We also explored the use of D/H ratios in Sphagnum biomarkers as a water-table depth proxy. Compound-specific hydrogen isotope ratio analyses were performed on Sphagnum biomarkers: C23 and C25 alkane and C24 acid. Dry periods are represented in these records by an enrichment of deuterium in these Sphagnum-specific compounds. These events also correlate

Species Composition, Relative Abundance and Distribution of the ...

African Journals Online (AJOL)

Species Composition, Relative Abundance and Distribution of the Avian Fauna of Entoto Natural Park and Escarpment, Addis Ababa. ... Eucalyptus plantation, soil erosion, deforestation, habitat fragmentation, settlement and land degradation were the main threats for the distribution of birds in the present study area.

Ecological interactions and the distribution, abundance, and diversity of sponges.

Science.gov (United States)

Wulff, Janie

2012-01-01

Although abiotic factors may be important first-order filters dictating which sponge species can thrive at a particular site, ecological interactions can play substantial roles influencing distribution and abundance, and thus diversity. Ecological interactions can modify the influences of abiotic factors both by further constraining distribution and abundance due to competitive or predatory interactions and by expanding habitat distribution or abundance due to beneficial interactions that ameliorate otherwise limiting circumstances. It is likely that the importance of ecological interactions has been greatly underestimated because they tend to only be revealed by experiments and time-series observations in the field. Experiments have revealed opportunistic predation to be a primary enforcer of sponge distribution boundaries that coincide with habitat boundaries in several systems. Within habitats, by contrast, dramatic effects of predators on sponge populations seem to occur primarily in cases of unusually high recruitment rates or unusually low mortality rates for the predators, which are often specialists on the sponge species affected. Competitive interactions have been demonstrated to diminish populations or exclude sponge species from a habitat in only a few cases. Cases in which competitive interactions have appeared obvious have often turned out to be neutral or even beneficial interactions when observed over time. Especially striking in this regard are sponge-sponge interactions in dense sponge-dominated communities, which may promote the continued coexistence of all participating species. Mutualistic symbioses of sponges with other animals, plants, or macroalgae have been demonstrated to increase abundance, habitat distribution, and diversity of all participants. Symbiotic microbes can enhance sponge distribution and abundance but also render their hosts more vulnerable to environmental changes. And while photosynthetic symbionts can boost growth and

The Beryllium 7 Depth Distribution Study

International Nuclear Information System (INIS)

Jalal Sharib; Zainudin Othman; Dainee Nor Fardzila Ahmad Tugi

2014-01-01

The aim of this paper is to study the evolution of 7Be depth distribution in a soil profile. The soil samples have been collected by using plastic core in bare area in Bangi, Malaysia. Each of the soil core samples has been sectioned into 2 mm increments to a depth of 4 cm and the samples are subsequently oven dried at 45°C and gently disaggregated. The sample is passed through a < 2 mm sieve and packed into plastic pot for 7Be analysis using gamma spectrometry with a 24 hour count time. From the findings, show the 7Be depth penetration from this study decreases exponentially with depth and is confined within the top few centimeters and similar with other works been reported. The further discussion for this findings will be presented in full paper. (author)

Floral abundance, richness, and spatial distribution drive urban garden bee communities.

Science.gov (United States)

Plascencia, M; Philpott, S M

2017-10-01

In urban landscapes, gardens provide refuges for bee diversity, but conservation potential may depend on local and landscape features. Foraging and population persistence of bee species, as well as overall pollinator community structure, may be supported by the abundance, richness, and spatial distribution of floral resources. Floral resources strongly differ in urban gardens. Using hand netting and pan traps to survey bees, we examined whether abundance, richness, and spatial distribution of floral resources, as well as ground cover and garden landscape surroundings influence bee abundance, species richness, and diversity on the central coast of California. Differences in floral abundance and spatial distribution, as well as urban cover in the landscape, predicted different bee community variables. Abundance of all bees and of honeybees (Apis mellifera) was lower in sites with more urban land cover surrounding the gardens. Honeybee abundance was higher in sites with patchy floral resources, whereas bee species richness and bee diversity was higher in sites with more clustered floral resources. Surprisingly, bee species richness and bee diversity was lower in sites with very high floral abundance, possibly due to interactions with honeybees. Other studies have documented the importance of floral abundance and landscape surroundings for bees in urban gardens, but this study is the first to document that the spatial arrangement of flowers strongly predicts bee abundance and richness. Based on these findings, it is likely that garden managers may promote bee conservation by managing for floral connectivity and abundance within these ubiquitous urban habitats.

Species identification, distribution and abundance of Gerreidae ...

African Journals Online (AJOL)

the distribution and abundance of Gerres in estuaries wa'S collected from July 1978 to ..... the channel area between the W.L.R. and the mouth (not the tidal basin) during ..... overwhelming importance in the kelp beds of Britain. Recently Blaber ...

Distribution, abundance and morphometry of Atlantoraja cyclophora (Regan, 1903 (Elasmobranchii: Rajidae in southern Brazil, Southwestern Atlantic

Directory of Open Access Journals (Sweden)

María Cristina Oddone

Full Text Available A total of 459 individuals of Atlantoraja cyclophora were captured along the Rio Grande do Sul coast between latitudes 30º40'S and 34º30'S. Two surveys were performed, in the winter 2001 and in the summer/autumn 2002, using bottom-trawl between the depths of 100 and 600 m. This species occurred between 100 and 300 m deep, without significant differences in the frequency of occurrence and abundance (CPUE; kg/hour between latitudes, depth and seasons. The sex ratio was not significantly different from 1:1 in all depths. In the study area, temperature ranged between 10.0 ºC and 17.6 ºC and salinity between 35.2 e 36.0 ppm. There was no correlation between CPUE and depth, temperature and salinity. Mean total length of females (53.2 cm was significantly larger than males (50.9 cm. No differences were detected in mean total length between seasons, but mean total length was significantly larger in depths of 100 m and 200 m. The distribution of the frequencies of total length was asymmetric, indicating rareness or lack of juveniles in the samples.

Distribution and covering percentage of sponge (Porifera in different coral reef condition and depth in Barranglompo Island, South Sulawesi

Directory of Open Access Journals (Sweden)

SUHARYANTO

2008-07-01

Full Text Available In 1996, four specieses of sponge namely Auletta sp., Callyspongia pseudoreticulata, Callyspongia sp., and Halichondria sp. have been potentially identified as bacteriside for fishery commodities. Nevertheless, information on sponge distribution, its covering percentage, and its habitate are still very little. Observation on distribution and abundance of sponge was conducted in the Southeastern and the Northwestern part of Barranglompo Island, South Sulawesi, using scuba diving set and under water writting tools. At first, coral reef condition in 3 and 10 m depths up to 100 m length of shore line were observed in both stations, using “lifeform method”. Then distribution and covering percentage of sponge, biotic and abiotic factor in 3, 6, 9, and 12 m depths in both stations were examined using “square transect method”. The result showed that different coral reef condition qualitatively causes different of sponge species distribution, but quantitatively not significantly different (P>0,05 on its covering percentage. It was also found that generally sponge grows better at the dead coral where no other biotic organism around.

WATER DEPTH and Other Data (NODC Accession 9400096)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Conductivity, Temperature and Depth (CTD); and bathythermograph (XBT) data were collected as part of Distribution/Abundance of Marine Mammals in Gulf of Mexico...

The implicit assumption of symmetry and the species abundance distribution

NARCIS (Netherlands)

Alonso, D.; Ostling, A.; Etienne, R.S.

2008-01-01

Species abundance distributions (SADs) have played a historical role in the development of community ecology. They summarize information about the number and the relative abundance of the species encountered in a sample from a given community. For years ecologists have developed theory to

The implicit assumption of symmetry and the species abundance distribution

NARCIS (Netherlands)

Alonso, David; Ostling, Annette; Etienne, Rampal S.

Species abundance distributions (SADs) have played a historical role in the development of community ecology. They summarize information about the number and the relative abundance of the species encountered in a sample from a given community. For years ecologists have developed theory to

Distribution, abundance and ecology of the sponge Spheciospongia ...

African Journals Online (AJOL)

Western Indian Ocean Journal of Marine Science ... Journal Home > Vol 12, No 1 (2013) > ... Distribution, abundance and ecology of the sponge Spheciospongia vagabunda (Phylum: Porifera, Class: Demospongiae) in a shallow lagoon of ...

Relating species abundance distributions to species-area curves in two Mediterranean-type shrublands

Science.gov (United States)

Keeley, Jon E.

2003-01-01

Based on both theoretical and empirical studies there is evidence that different species abundance distributions underlie different species-area relationships. Here I show that Australian and Californian shrubland communities (at the scale from 1 to 1000 m2) exhibit different species-area relationships and different species abundance patterns. The species-area relationship in Australian heathlands best fits an exponential model and species abundance (based on both density and cover) follows a narrow log normal distribution. In contrast, the species-area relationship in Californian shrublands is best fit with the power model and, although species abundance appears to fit a log normal distribution, the distribution is much broader than in Australian heathlands. I hypothesize that the primary driver of these differences is the abundance of small-stature annual species in California and the lack of annuals in Australian heathlands. Species-area is best fit by an exponential model in Australian heathlands because the bulk of the species are common and thus the species-area curves initially rise rapidly between 1 and 100 m2. Annuals in Californian shrublands generate very broad species abundance distributions with many uncommon or rare species. The power function is a better model in these communities because richness increases slowly from 1 to 100 m2 but more rapidly between 100 and 1000 m2due to the abundance of rare or uncommon species that are more likely to be encountered at coarser spatial scales. The implications of this study are that both the exponential and power function models are legitimate representations of species-area relationships in different plant communities. Also, structural differences in community organization, arising from different species abundance distributions, may lead to different species-area curves, and this may be tied to patterns of life form distribution.

Host trait combinations drive abundance and canopy distribution of atmospheric bromeliad assemblages.

Science.gov (United States)

Chaves, Cleber Juliano Neves; Dyonisio, Júlio César; Rossatto, Davi Rodrigo

2016-01-01

Epiphytes are strongly dependent on the conditions created by their host's traits and a certain degree of specificity is expected between them, even if these species are largely abundant in a series of tree hosts of a given environment, as in the case of atmospheric bromeliads. Despite their considerable abundance in these environments, we hypothesize that stochasticity alone cannot explain the presence and abundance of atmospheric bromeliads on host trees, since host traits could have a greater influence on the establishment of these bromeliads. We used secondary and reforested seasonal forests and three distinct silvicultures to test whether species richness, phylogenetic diversity and functional diversity of trees can predict the differential presence, abundance and distribution of atmospheric bromeliads on hosts. We compared the observed parameters of their assemblage with null models and performed successive variance hierarchic partitions of abundance and distribution of the assemblage to detect the influence of multiple traits of the tree hosts. Our results do not indicate direct relationships between the abundance of atmospheric bromeliads and phylogenetic or functional diversity of trees, but instead indicate that bromeliads occurred on fewer tree species than expected by chance. We distinguished functional tree patterns that can improve or reduce the abundance of atmospheric bromeliads, and change their distribution on branches and trunk. While individual tree traits are related to increased abundance, species traits are related to the canopy distribution of atmospheric bromeliad assemblages. A balance among these tree functional patterns drives the atmospheric bromeliad assemblage of the forest patches. Published by Oxford University Press on behalf of the Annals of Botany Company.

Distribution in depth of quasars

International Nuclear Information System (INIS)

Schmidt, M.; Green, R.F.

1980-01-01

The authors discuss the distribution in depth of different kinds of quasars: quasi-stellar radio sources with steep radio spectrum, those with flat radio spectrum, and optically selected quasars. All exhibit an increase of space density with distance to a different degree. The optically selected quasars, in particular, show a steep increase of surface density with magnitude. The steepness of the increase is inconsistent with a uniform distribution of quasars in the local hypothesis. In the cosmological hypothesis the co-moving space density of optically selected quasars increases by a factor of 100,000 to a redshift of 2, and by factors of 1000 and 10 for steep-spectrum and flat-spectrum radio quasars, respectively. (Auth.)

Distribution And Seasonal Abundance Of Anopheline Mosquito ...

African Journals Online (AJOL)

The essence of this study was to identify Anopheles mosquito species in Nguru, Yobe State and to determine their distribution and relative abundance in the months of the year. Insecticide and aspirator were used to collect mosqutoes in human dwellngs and preserved in 2% formalin for identcation using dissectng ...

Composition, distribution and abundance of ichthyoplankton in the ...

African Journals Online (AJOL)

1989-06-29

Jun 29, 1989 ... The species composition, distribution and seasonal abundance of ichthyoplankton in the Sundays River estuary was ... The importance of southern African estuaries as nursery areas for juvenile ... 1990,25(3) the mid-channel.

Deuterium depth profiles in metals using imaging field desorption

International Nuclear Information System (INIS)

Panitz, J.A.

1976-01-01

Depth profiles of 80 eV deuterium ions implanted in-situ into (110) tungsten have been measured by Imaging, Field-Desorption Mass Spectrometry. The relative abundance of deuterium was measured from the surface to a depth of 300A with less than 3A depth resolution by controlled field-evaporation of the specimen, and time-of-flight mass spectroscopy. The position of the depth distribution maximum (57 +- 3A from the surface) is shown to be in close agreement with that predicted theoretically for low energy deuterium implants using an amorphous-solid model. Structure in the distribution is attributed to surface morphology and channeling phenomena in the near surface region. Implanted impurity species from the ion source and tungsten surface have also been observed. For C + , C 2+ and 0 + , penetration is limited to less than 30A, with abundance decreasing exponentially from the surface. These results are interpreted in the context of the CTR first-wall impurity problem, and are used to suggest a novel method for in-situ characterization of low energy plasma species in operating CTR devices

Rooting depth and root depth distribution of Trifolium repens × T. uniflorum interspecific hybrids.

Science.gov (United States)

Nichols, S N; Hofmann, R W; Williams, W M; van Koten, C

2016-05-20

Traits related to root depth distribution were examined in Trifolium repens × T. uniflorum backcross 1 (BC 1 ) hybrids to determine whether root characteristics of white clover could be improved by interspecific hybridization. Two white clover cultivars, two T. uniflorum accessions and two BC 1 populations were grown in 1 -m deep tubes of sand culture. Maximum rooting depth and root mass distribution were measured at four harvests over time, and root distribution data were fitted with a regression model to provide measures of root system shape. Morphological traits were measured at two depths at harvest 3. Root system shape of the hybrids was more similar to T. uniflorum than to white clover. The hybrids and T. uniflorum had a higher rate of decrease in root mass with depth than white clover, which would result in higher proportions of root mass in the upper profile. Percentage total root mass at 100-200 mm depth was higher for T. uniflorum than white clover, and for Crusader BC 1 than 'Crusader'. Roots of the hybrids and T. uniflorum also penetrated deeper than those of white clover. T. uniflorum had thicker roots at 50-100 mm deep than the other entries, and more of its fine root mass at 400-500 mm. The hybrids and white clover had more of their fine root mass higher in the profile. Consequently, T. uniflorum had a higher root length density at 400-500 mm than most entries, and a smaller decrease in root length density with depth. These results demonstrate that rooting characteristics of white clover can be altered by hybridization with T. uniflorum, potentially improving water and nutrient acquisition and drought resistance. Root traits of T. uniflorum are likely to be adaptations to soil moisture and fertility in its natural environment. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Depth distribution of nitrogen in silicon from plasma ion implantation

International Nuclear Information System (INIS)

Vajo, J.J.; Williams, J.D.; Wei, R.; Wilson, R.G.; Matossian, J.N.

1994-01-01

Plasma Ion Implantation (PII) is an ion implantation technique that eliminates the line-of-sight restriction of conventional ion-beam implantation and therefore allows for cost effective surface modification of large-scale objects or large-number of small-scale objects. In PII, a part to be implanted is immersed in a low-pressure (10 -4 --10 -5 Torr), partially-ionized plasma that surrounds the part with a plasma sheath. The part is negatively pulse biased up to 100 keV using a repetitive train (100--1,000 Hz) of short-duration (10--40 μsec) voltage pulses. The applied voltage develops across the sheath and accelerates plasma ions into the surface, implanting them omnidirectionally and simultaneously over the entire surface of the part. The depth distribution of the implanted ions influences the extent and type of surface modification achieved and depends upon many factors. These include three rise and fall time of the voltage-pulse waveform, the voltage-pulse amplitude, the ion specie, the ion density, and the temperature of the target. Understanding the contributions to the depth distribution from each of these factors will enable prediction of conditions that will be useful for implantation of large complex parts. To investigate the contributions to the measured depth distributions from these factors nitrogen, predominantly as N + 2 , has been implanted into silicon using PII at 50 and 100 keV (25 and 50 keV per N atom). The implanted depth distributions have been determined using secondary ion mass spectroscopy and Auger electron spectroscopy depth profiling. The distributions differ from the typical, approximately Gaussian, profiles that result from conventional mass selected monoenergetic ion beam implantation. In comparison with ion beam implants and numerical simulations the profiles appear ''filled-in'' with an approximately constant nitrogen concentration for depths less than the expected average ion range

Forms and genesis of species abundance distributions

Directory of Open Access Journals (Sweden)

Evans O. Ochiaga

2015-12-01

Full Text Available Species abundance distribution (SAD is one of the most important metrics in community ecology. SAD curves take a hollow or hyperbolic shape in a histogram plot with many rare species and only a few common species. In general, the shape of SAD is largely log-normally distributed, although the mechanism behind this particular SAD shape still remains elusive. Here, we aim to review four major parametric forms of SAD and three contending mechanisms that could potentially explain this highly skewed form of SAD. The parametric forms reviewed here include log series, negative binomial, lognormal and geometric distributions. The mechanisms reviewed here include the maximum entropy theory of ecology, neutral theory and the theory of proportionate effect.

Does interference competition with wolves limit the distribution and abundance of coyotes?

Science.gov (United States)

Berger, Kim Murray; Gese, Eric M

2007-11-01

Interference competition with wolves Canis lupus is hypothesized to limit the distribution and abundance of coyotes Canis latrans, and the extirpation of wolves is often invoked to explain the expansion in coyote range throughout much of North America. We used spatial, seasonal and temporal heterogeneity in wolf distribution and abundance to test the hypothesis that interference competition with wolves limits the distribution and abundance of coyotes. From August 2001 to August 2004, we gathered data on cause-specific mortality and survival rates of coyotes captured at wolf-free and wolf-abundant sites in Grand Teton National Park (GTNP), Wyoming, USA, to determine whether mortality due to wolves is sufficient to reduce coyote densities. We examined whether spatial segregation limits the local distribution of coyotes by evaluating home-range overlap between resident coyotes and wolves, and by contrasting dispersal rates of transient coyotes captured in wolf-free and wolf-abundant areas. Finally, we analysed data on population densities of both species at three study areas across the Greater Yellowstone Ecosystem (GYE) to determine whether an inverse relationship exists between coyote and wolf densities. Although coyotes were the numerically dominant predator, across the GYE, densities varied spatially and temporally in accordance with wolf abundance. Mean coyote densities were 33% lower at wolf-abundant sites in GTNP, and densities declined 39% in Yellowstone National Park following wolf reintroduction. A strong negative relationship between coyote and wolf densities (beta = -3.988, P wolves limits coyote populations. Overall mortality of coyotes resulting from wolf predation was low, but wolves were responsible for 56% of transient coyote deaths (n = 5). In addition, dispersal rates of transient coyotes captured at wolf-abundant sites were 117% higher than for transients captured in wolf-free areas. Our results support the hypothesis that coyote abundance is

The distribution and abundance of the endangered Knysna ...

African Journals Online (AJOL)

The occurrence, distribution and abundance of the endangered Knysna seahorse Hippocampus capensis in 10 estuaries on South Africa's warm temperate south coast, were investigated. Seahorses were found only in the Knysna, Swartvlei and Keurbooms estuaries. Sex ratios were even and, in most cases, more adults ...

The population abundance, distribution pattern and culture studies ...

African Journals Online (AJOL)

STORAGESEVER

2009-08-18

Aug 18, 2009 ... The population abundance, distribution pattern and culture studies of ... plankton species belong mainly to the nanoplankton and microplankton ... Algal samples were collected from the shore using microalgal net cone shaped of .... species diversity of Porto Novo, Tamil Nadu and De et al. (1994) in the ...

Attenuation of species abundance distributions by sampling

Science.gov (United States)

Shimadzu, Hideyasu; Darnell, Ross

2015-01-01

Quantifying biodiversity aspects such as species presence/ absence, richness and abundance is an important challenge to answer scientific and resource management questions. In practice, biodiversity can only be assessed from biological material taken by surveys, a difficult task given limited time and resources. A type of random sampling, or often called sub-sampling, is a commonly used technique to reduce the amount of time and effort for investigating large quantities of biological samples. However, it is not immediately clear how (sub-)sampling affects the estimate of biodiversity aspects from a quantitative perspective. This paper specifies the effect of (sub-)sampling as attenuation of the species abundance distribution (SAD), and articulates how the sampling bias is induced to the SAD by random sampling. The framework presented also reveals some confusion in previous theoretical studies. PMID:26064626

Texture side information generation for distributed coding of video-plus-depth

DEFF Research Database (Denmark)

Salmistraro, Matteo; Raket, Lars Lau; Zamarin, Marco

2013-01-01

We consider distributed video coding in a monoview video-plus-depth scenario, aiming at coding textures jointly with their corresponding depth stream. Distributed Video Coding (DVC) is a video coding paradigm in which the complexity is shifted from the encoder to the decoder. The Side Information...... components) is strongly correlated, so the additional depth information may be used to generate more accurate SI for the texture stream, increasing the efficiency of the system. In this paper we propose various methods for accurate texture SI generation, comparing them with other state-of-the-art solutions...

The taxonomic composition, distribution and abundance of the ...

African Journals Online (AJOL)

The study determined the abundance and distribution of phytoplankton flora of an impoundment in the Agricultural Teaching and Research Farm of ObafemiAwolowo University (O.A.U), Ile-Ife, Osun State, Nigeria. The study was carried out over an annual cycle from September 2006- August 2007, Phytoplankton and water ...

Linking mesopelagic prey abundance and distribution to the foraging behavior of a deep-diving predator, the northern elephant seal

Science.gov (United States)

Saijo, Daisuke; Mitani, Yoko; Abe, Takuzo; Sasaki, Hiroko; Goetsch, Chandra; Costa, Daniel P.; Miyashita, Kazushi

2017-06-01

The Transition Zone in the eastern North Pacific is important foraging habitat for many marine predators. Further, the mesopelagic depths (200-1000 m) host an abundant prey resource known as the deep scattering layer that supports deep diving predators, such as northern elephant seals, beaked whales, and sperm whales. Female northern elephant seals (Mirounga angustirostris) undertake biannual foraging migrations to this region where they feed on mesopelagic fish and squid; however, in situ measurements of prey distribution and abundance, as well as the subsurface oceanographic features in the mesopelagic Transition Zone are limited. While concurrently tracking female elephant seals during their post-molt migration, we conducted a ship-based oceanographic and hydroacoustic survey and used mesopelagic mid-water trawls to sample the deep scattering layer. We found that the abundance of mesopelagic fish at 400-600 m depth zone was the highest in the 43 °N zone, the primary foraging area of female seals. We identified twenty-nine families of fishes from the mid-water trawls, with energy-rich myctophid fishes dominating by species number, individual number, and wet weight. Biomass of mesopelagic fishes is positively correlated to annual net primary productivity; however, at the temporal and spatial scale of our study, we found no relationship between satellite derived surface primary production and prey density. Instead, we found that the subsurface chlorophyll maximum correlated with the primary elephant seal foraging regions, indicating a stronger linkage between mesopelagic ecosystem dynamics and subsurface features rather than the surface features measured with satellites. Our study not only provides insights on prey distribution in a little-studied deep ocean ecosystem, but shows that northern elephant seals are targeting the dense, species-diverse mesopelagic ecosystem at the gyre-gyre boundary that was previously inferred from their diving behavior.

Effects of prey abundance, distribution, visual contrast and morphology on selection by a pelagic piscivore

Science.gov (United States)

Hansen, Adam G.; Beauchamp, David A.

2014-01-01

Most predators eat only a subset of possible prey. However, studies evaluating diet selection rarely measure prey availability in a manner that accounts for temporal–spatial overlap with predators, the sensory mechanisms employed to detect prey, and constraints on prey capture.We evaluated the diet selection of cutthroat trout (Oncorhynchus clarkii) feeding on a diverse planktivore assemblage in Lake Washington to test the hypothesis that the diet selection of piscivores would reflect random (opportunistic) as opposed to non-random (targeted) feeding, after accounting for predator–prey overlap, visual detection and capture constraints.Diets of cutthroat trout were sampled in autumn 2005, when the abundance of transparent, age-0 longfin smelt (Spirinchus thaleichthys) was low, and 2006, when the abundance of smelt was nearly seven times higher. Diet selection was evaluated separately using depth-integrated and depth-specific (accounted for predator–prey overlap) prey abundance. The abundance of different prey was then adjusted for differences in detectability and vulnerability to predation to see whether these factors could explain diet selection.In 2005, cutthroat trout fed non-randomly by selecting against the smaller, transparent age-0 longfin smelt, but for the larger age-1 longfin smelt. After adjusting prey abundance for visual detection and capture, cutthroat trout fed randomly. In 2006, depth-integrated and depth-specific abundance explained the diets of cutthroat trout well, indicating random feeding. Feeding became non-random after adjusting for visual detection and capture. Cutthroat trout selected strongly for age-0 longfin smelt, but against similar sized threespine stickleback (Gasterosteus aculeatus) and larger age-1 longfin smelt in 2006. Overlap with juvenile sockeye salmon (O. nerka) was minimal in both years, and sockeye salmon were rare in the diets of cutthroat trout.The direction of the shift between random and non-random selection

Distribution and abundance of saltcedar and Russian olive in the western United States

Science.gov (United States)

Nagler, Pamela L.; Glenn, Edward P.; Jarnevich, Catherine S.; Shafroth, Patrick B.

2011-01-01

Over the past century, two introduced Eurasian trees, saltcedar (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) have become wide spread on western United States of American (U.S.) rivers. This paper reviews the literature on the following five key areas related to their distribution and abundance in the western United States: (1) the history of introduction, planting, and spread of saltcedar and Russian olive; (2) their current distribution; (3) their current abundance; (4) factors controlling their current distribution and abundance; and (5) models that have been developed to predict their future distribution and abundance. Saltcedar and Russian olive are now the third and fourth most frequently occurring woody riparian plants and the second and fifth most abundant species (out of 42 native and non-native species) along rivers in the western United States. Currently there is not a precise estimate of the areas that these species occupy in the entire West. Climatic variables are important determinants of their distribution and abundance. For example, saltcedar is limited by its sensitivity to hard freezes, whereas Russian olive appears to have a chilling requirement for bud break and seed germination, and can presumably survive colder winter temperatures. Either species can be dominant, co-dominant or sub-dominant relative to native species on a given river system. A number of environmental factors such as water availability, soil salinity, degree of stream flow regulation, and fire frequency can influence the abundance of these species relative to native species. Numerous studies suggest that both species have spread on western rivers primarily through a replacement process, whereby stress-tolerant species have moved into expanded niches that are no longer suitable for mesic native pioneer species. Better maps of current distribution and rigorous monitoring of distributional changes though time can help to resolve differences in predictions of potential

An improved in situ method for determining depth distributions of gamma-ray emitting radionuclides

International Nuclear Information System (INIS)

Benke, R.R.; Kearfott, K.J.

2001-01-01

In situ gamma-ray spectrometry determines the quantities of radionuclides in some medium with a portable detector. The main limitation of in situ gamma-ray spectrometry lies in determining the depth distribution of radionuclides. This limitation is addressed by developing an improved in situ method for determining the depth distributions of gamma-ray emitting radionuclides in large area sources. This paper implements a unique collimator design with conventional radiation detection equipment. Cylindrically symmetric collimators were fabricated to allow only those gamma-rays emitted from a selected range of polar angles (measured off the detector axis) to be detected. Positioned with its axis normal to surface of the media, each collimator enables the detection of gamma-rays emitted from a different range of polar angles and preferential depths. Previous in situ methods require a priori knowledge of the depth distribution shape. However, the absolute method presented in this paper determines the depth distribution as a histogram and does not rely on such assumptions. Other advantages over previous in situ methods are that this method only requires a single gamma-ray emission, provides more detailed depth information, and offers a superior ability for characterizing complex depth distributions. Collimated spectrometer measurements of buried area sources demonstrated the ability of the method to yield accurate depth information. Based on the results of actual measurements, this method increases the potential of in situ gamma-ray spectrometry as an independent characterization tool in situations with unknown radionuclide depth distributions

Abundance, distribution and species composition of fish larvae in ...

African Journals Online (AJOL)

improving our knowledge of the abundance, distribution and species diversity ... banks as well as in the mid-channel, thus eliminating any bias that might have .... cond method (Table 2) may bias the importance of a single species due to one, ...

Abundance and distribution of benthic macroinvertebrates in offshore soft sediments in Western Lake Huron, 2001-2007

Science.gov (United States)

French, J. R. P.; Schaeffer, J.S.; Roseman, E.F.; Kiley, C.S.; Fouilleroux, A.

2009-01-01

Invasive species have had major impacts on the Great Lakes. This is especially true of exotic dreissenid mussels which are associated with decreased abundance of native macroinvertebrates and changes in food availability for fish. Beginning in 2001, we added a benthic macroinvertebrate survey to the USGS-Great Lakes Science Center's annual fall prey fish assessment of Lake Huron to monitor abundance of macrobenthos. Mean abundance of Diporeia, the most abundant benthic taxon in Lake Huron reported by previous investigators, declined greatly between 2001 and 2007. Diporeia was virtually absent at 27-m sites by 2001, decreased and was lost completely from 46-m depths by 2006, but remained present at reduced densities at 73-m sites. Dreissenids in our samples were almost entirely quagga mussels Dreissena bugensis. Zebra mussels Dreissena polymorpha were virtually absent from our samples, suggesting that they were confined to nearshore areas shallower than we sampled. Loss of Diporeia at individual sites was associated with arrival of quagga mussels, even when mussel densities were low. Quagga mussel density peaked during 2002, then decreased thereafter. During the study quagga mussels became established at most 46-m sites, but remained rare at 73-m sites. Length frequency distributions suggest that initial widespread recruitment may have occurred during 2001-2002. Like other Great Lakes, Lake Huron quagga mussels were associated with decreased abundance of native taxa, but negative effects occurred even though dreissenid densities were much lower. Dreissenid effects may extend well into deep oligotrophic habitats of Lake Huron.

Distribution and abundance of the Southern Fulmar Fulmarus glacialoides

NARCIS (Netherlands)

Creuwels, J.C.S.; Poncet, S.; Hodum, P.J.; Franeker, van J.A.

2007-01-01

We reviewed published and unpublished literature to establish the status of the breeding distribution and abundance of Southern Fulmars Fulmarus glacialoides. The species breeds widely throughout the Antarctic and on peri-Antarctic islands. From breeding population data collated from 73 of these

Distribution and abundance of the Southern Fulmar Fulmarus glacialoides

NARCIS (Netherlands)

Creuwels, Jeroen C. S.; Poncet, Sally; Hodum, Peter J.; van Franeker, Jan A.

We reviewed published and unpublished literature to establish the status of the breeding distribution and abundance of Southern Fulmars Fulmarus glacialoides. The species breeds widely throughout the Antarctic and on peri-Antarctic islands. From breeding population data collated from 73 of these

Depth-Dose and LET Distributions of Antiproton Beams in Various Target Materials

DEFF Research Database (Denmark)

Herrmann, Rochus; Olsen, Sune; Petersen, Jørgen B.B.

the annihilation process. Materials We have investigated the impact of substituting the target material on  the depth-dose distribution of pristine and  spread out antiproton beams using the FLUKA Monte Carlo transport program. Classical ICRP targets are compared to water phantoms. In addition, track average...... unrestricted LET is calculated for all configurations. Finally, we investigate which concentrations of gadolinium and boron are needed in a water target in order to observe a significant change in the antiproton depth-dose distribution.  Results Results indicate, that there is no significant change...... in the depth-dose distribution and average LET when substituting the materials. Adding boron and gadolinium up to concentrations of 1 per 1000 atoms to a water phantom, did not change the depth-dose profile nor the average LET. Conclusions  According to our FLUKA calculations, antiproton neutron capture...

A biogeographical perspective on species abundance distributions

DEFF Research Database (Denmark)

Matthews, Thomas J.; Borges, Paulo A. V.; de Azevedo, Eduardo Brito

2017-01-01

It has become increasingly recognized that multiple processes can generate similar shapes of species abundance distributions (SADs), with the result that the fit of a given SAD model cannot unambiguously provide evidence in support of a given theory or model. An alternative approach to comparing...... the fit of different SAD models to data from a single site is to collect abundance data from a variety of sites, and then build models to analyse how different SAD properties (e.g. form, skewness) vary with different predictor variables. Such a biogeographical approach to SAD research is potentially very...... revealing, yet there has been a general lack of interest in SADs in the biogeographical literature. In this Perspective, we address this issue by highlighting findings of recent analyses of SADs that we consider to be of intrinsic biogeographical interest. We use arthropod data drawn from the Azorean...

Density distributions and depth in flocks

Science.gov (United States)

Lewis, J. M.; Turner, M. S.

2017-12-01

Recent experimental evidence suggests that interactions in flocks of birds do not involve a characteristic length scale. Bird flocks have also been revealed to have an inhomogeneous density distribution, with the density of birds near the border greater than near the centre. We introduce a strictly metric-free model for collective behaviour that incorporates a distributed motional bias, providing control of the density distribution. A simple version of this model is then able to provide a good fit to published data for the density variation across flocks of Starlings. We find that it is necessary for individuals on the edge of the flock to have an inward motional bias but that birds in the interior of the flock instead must have an outward bias. We discuss the ability of individuals to determine their depth within a flock and show how this might be achieved by relatively simple analysis of their visual environment.

Depth distribution of multiple order X-ray scatter

International Nuclear Information System (INIS)

Yao Weiguang; Leszczynski, Konrad

2008-01-01

Scatter can significantly affect quality of projectional X-ray radiographs and tomographic reconstructions. With this in mind, we examined some of the physical properties of multiple orders of scatter of X-ray photons traversing through a layer of scattering media such as water. Using Monte Carlo techniques, we investigated depth distributions of interactions between incident X-ray photons and water before the resulting scattered photons reach the detector plane. Effects of factors such as radiation field size, air gap, thickness of the layer of scattering medium and X-ray energy, on the scatter were included in the scope of this study. The following scatter characteristics were observed: (1) for a layer of scattering material corresponding to the typical subject thickness in medical imaging, frequency distribution of locations of the last scattering interaction increases approximately exponentially with depth, and the higher the order of scatter or the energy of the incident photon, the narrower is the distribution; (2) for the second order scatter, the distribution of locations of the first interaction is more uniform than that of the last interaction and is dependent on the energy of the primary photons. Theoretical proofs for some of these properties are given. These properties are important to better understanding of effects of scatter on the radiographic and tomographic imaging process and to developing effective methods for scatter correction

Distribution and abundance of juvenile demersal fishes in relation to summer hypoxia and other environmental variables in coastal Oregon, USA

Science.gov (United States)

Sobocinski, Kathryn L.; Ciannelli, Lorenzo; Wakefield, W. Waldo; Yergey, Matthew E.; Johnson-Colegrove, Angela

2018-05-01

The juvenile demersal fish assemblage along the Pacific Northwest coast has received little attention relative to adult life history stages since pioneering work in the 1970s. Increasing severity of hypoxia along the Oregon coast in recent years has prompted investigations into the response of biota in this region. We used summer data (2008-2013) from a beam trawl survey targeting juvenile demersal fishes in soft-bottom habitats along the Oregon coast to describe patterns of distribution and abundance at fixed sampling stations (from 30 m to 100 m depth). We relate the assemblage and abundance of the common species to environmental variables and analyze condition of recently settled fish (improve our understanding of this community, especially in light of changing environmental drivers such as decreasing pH, warming water, and episodic periods of low dissolved oxygen coinciding with settlement for many species.

Modeled distribution and abundance of a pelagic seabird reveal trends in relation to fisheries

Science.gov (United States)

Renner, Martin; Parrish, Julia K.; Piatt, John F.; Kuletz, Kathy J.; Edwards, Ann E.; Hunt, George L.

2013-01-01

The northern fulmar Fulmarus glacialis is one of the most visible and widespread seabirds in the eastern Bering Sea and Aleutian Islands. However, relatively little is known about its abundance, trends, or the factors that shape its distribution. We used a long-term pelagic dataset to model changes in fulmar at-sea distribution and abundance since the mid-1970s. We used an ensemble model, based on a weighted average of generalized additive model (GAM), multivariate adaptive regression splines (MARS), and random forest models to estimate the pelagic distribution and density of fulmars in the waters of the Aleutian Archipelago and Bering Sea. The most important predictor variables were colony effect, sea surface temperature, distribution of fisheries, location, and primary productivity. We calculated a time series from the ratio of observed to predicted values and found that fulmar at-sea abundance declined from the 1970s to the 2000s at a rate of 0.83% (± 0.39% SE) per annum. Interpolating fulmar densities on a spatial grid through time, we found that the center of fulmar distribution in the Bering Sea has shifted north, coinciding with a northward shift in fish catches and a warming ocean. Our study shows that fisheries are an important, but not the only factor, shaping fulmar distribution and abundance trends in the eastern Bering Sea and Aleutian Islands.

A technique for determining the depth distribution of cavities in He+-irradiated nickel

International Nuclear Information System (INIS)

Fenske, G.; Das, S.K.; Kaminsky, M.

1979-01-01

The authors describe a technique for examining the depth distribution of the damage (i.e., dislocations, bubbles and voids) in 4 He + ion-irradiated nickel. One existing technique is to section the sample parallel to the direction of the incident beam and prepare thin foils suitable for TEM. This technique has been used only in a few instances because of the difficulty in sample preparation, but it has the advantage that the entire depth distribution of damage can be obtained from a single sample. The technique described by the present authors is a modification of this type of technique and allows one to observe the depth distribution of bubbles and of damage in very near surface regions (<0.2μm) with excellent depth resolution and a small (approximately 50 A) uncertainty in locating the irradiated surface. (Auth.)

The Pearson IV distribution and its application to ion implanted depth profiles

International Nuclear Information System (INIS)

Wilson, R.G.

1980-01-01

The Pearson IV distribution system is analyzed to determine the regions of validity for the values of the moments that produce convex, concave, more pointed than Gaussian, and more flat-topped than Gaussian distributions; the limits beyond which no significant change in distribution is produced; and excluded regions. These regions are illustrated in a figure that can be used to facilitate the determination of the Pearson IV moments for experimental ion implanted depth distributions. Examples are given of Pearson IV distributions to illustrate the effects of the ranges of skewness, kurtosis, and standard deviation, for both more pointed and more flat-topped than Gaussian distributions. A procedure is described for matching experimental ion implanted depth distributions to computer plotted Pearson IV modified Gaussian distributions. A few experimental curves are given to illustrate the different types of Pearson IV curves, and accuracies of moments are discussed. (author)

Depth distribution of martensite in xenon implanted stainless steels

International Nuclear Information System (INIS)

Johansen, A.; Johnson, E.; Sarholt-Kristensen, L.; Steenstrup, S.; Hayashi, N.; Sakamoto, I.

1989-01-01

The amount of stress-induced martensite and its distribution in depth in xenon implanted austenitic stainless steel poly- and single crystals have been measured by Rutherford backscattering and channeling analysis, depth selective conversion electron Moessbauer spectroscopy, cross-sectional transmission electron microscopy and x-ray diffraction analysis. In low nickel 17/7, 304 and 316 commercial stainless steels and in 17:13 single crystals the martensitic transformation starts at the surface and develops towards greater depth with increasing xenon fluence. The implanted layer is nearly completely transformed, and the interface between martensite and austenite is rather sharp and well defined. In high nickel 310 commercial stainless steel and 15:19 and 20:19 single crystals, on the other hand, only insignificant amounts of martensite are observed. (orig.)

Impact of water depth on the distribution of iGDGTs in the surface sediments from the northern South China Sea: applicability of TEX86 in marginal seas

Science.gov (United States)

Chen, Jiali; Hu, Pengju; Li, Xing; Yang, Yang; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Lü, Xiaoxia

2018-03-01

The TEX 86 H paleothermometer on the base of isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) has been widely applied to various marine settings to reconstruct past sea surface temperatures (SSTs). However, it remains uncertain how well this proxy reconstructs SSTs in marginal seas. In this study, we analyze the environmental factors governing distribution of iGDGTs in surface sediments to assess the applicability of TEX 86 H paleothermometer in the South China Sea (SCS). Individual iGDGT concentrations increase gradually eastwards. Redundancy analysis based on the relative abundance of an individual iGDGT compound and environmental parameters suggests that water depth is the most influential factor to the distribution of iGDGTs, because thaumarchaeota communities are water-depth dependent. Interestingly, the SST difference (Δ T) between TEX 86 H derived temperature and remote-sensing SST is less than 1°C in sediments with water depth>200 m, indicating that TEX 86 H was the robust proxy to trace the paleo-SST in the region if water depth is greater than 200 m.

Dispersal ability determines the scaling properties of species abundance distributions

DEFF Research Database (Denmark)

Borda-De-Água, Luís; Whittaker, Robert James; Cardoso, Pedro

2017-01-01

with computer simulations, low dispersal ability species generate a hump for intermediate abundance classes earlier than the distributions of high dispersal ability species. Importantly, when plotted as function of sample size, the raw moments of the SADs of arthropods have a power law pattern similar...

Estimating species occurrence, abundance, and detection probability using zero-inflated distributions.

Science.gov (United States)

Wenger, Seth J; Freeman, Mary C

2008-10-01

Researchers have developed methods to account for imperfect detection of species with either occupancy (presence absence) or count data using replicated sampling. We show how these approaches can be combined to simultaneously estimate occurrence, abundance, and detection probability by specifying a zero-inflated distribution for abundance. This approach may be particularly appropriate when patterns of occurrence and abundance arise from distinct processes operating at differing spatial or temporal scales. We apply the model to two data sets: (1) previously published data for a species of duck, Anas platyrhynchos, and (2) data for a stream fish species, Etheostoma scotti. We show that in these cases, an incomplete-detection zero-inflated modeling approach yields a superior fit to the data than other models. We propose that zero-inflated abundance models accounting for incomplete detection be considered when replicate count data are available.

Measurement of light-atom distributions in solids

International Nuclear Information System (INIS)

Blewer, R.S.

1977-01-01

We have developed a sensitive technique that is capable of nondestructively measuring the abundance and depth-distribution of isotopes of hydrogen or helium imbedded in a solid. The measurement is a form of ion-backscattering spectrometry which uses protons to probe within approximately 10μm of the surface of a solid. By analyzing the energy of the backscattered protons we can determine the number of atoms of a given mass present at various depths in the target material. This method permits detection of the lightest elements (i.e., those most difficult to detect by conventional ion-backscattering spectrometry) without sacrificing the capability of revealing the abundance and depth-distribution of heavier elements. For example, we have measured the initial distribution of helium implanted in a metal, then in subsequent measurements kept track of the helium migration

Rare earth element abundances and distribution patterns in plant materials

International Nuclear Information System (INIS)

Aidid, S.B.

1994-01-01

Eight out of the fourteen rare earth elements were estimated from the leaves of Pelthophorum pterocarpum, the leaves and roots of Impatiens balsamina, and the soils from four sampling sites by instrumental neutron activation analysis. The chondrite normalized rare earth element abundances and distribution patterns in the plant materials were found to be significantly correlated to the abundances of the rare earth elements occurring in the soils. The extent of accumulation of the rare earth elements in some plant materials was also governed by the age of the plants and the plant organs. (author) 16 refs.; 4 figs.; 3 tabs

Species Abundance in a Forest Community in South China: A Case of Poisson Lognormal Distribution

Institute of Scientific and Technical Information of China (English)

Zuo-Yun YIN; Hai REN; Qian-Mei ZHANG; Shao-Lin PENG; Qin-Feng GUO; Guo-Yi ZHOU

2005-01-01

Case studies on Poisson lognormal distribution of species abundance have been rare, especially in forest communities. We propose a numerical method to fit the Poisson lognormal to the species abundance data at an evergreen mixed forest in the Dinghushan Biosphere Reserve, South China. Plants in the tree, shrub and herb layers in 25 quadrats of 20 m×20 m, 5 m×5 m, and 1 m×1 m were surveyed. Results indicated that: (i) for each layer, the observed species abundance with a similarly small median, mode, and a variance larger than the mean was reverse J-shaped and followed well the zero-truncated Poisson lognormal;(ii) the coefficient of variation, skewness and kurtosis of abundance, and two Poisson lognormal parameters (σ andμ) for shrub layer were closer to those for the herb layer than those for the tree layer; and (iii) from the tree to the shrub to the herb layer, the σ and the coefficient of variation decreased, whereas diversity increased. We suggest that: (i) the species abundance distributions in the three layers reflects the overall community characteristics; (ii) the Poisson lognormal can describe the species abundance distribution in diverse communities with a few abundant species but many rare species; and (iii) 1/σ should be an alternative measure of diversity.

Depth distribution of chemical phase concentration determined by grazing incidence X-ray diffraction

International Nuclear Information System (INIS)

Novak, P.; Ballo, P.; Dobrocka, E.; Vallo, M.; Lalinsky, T.

2013-01-01

Grazing incidence geometry is widely used in X-ray diffraction analysis of thin films. Penetration depth of radiation can be easily changed by an appropriate selection of the angle of incidence α that enables obtaining information from different depths of the sample. This depth can be decreased up to a nanometer scale by approaching the critical angle α_c for total external reflection. This method therefore provides an efficient tool for the analysis of depth distribution of various structural properties, such as the crystallite size, the amorphous fraction, stress or the concentration of chemical phase. However, absorption of the radiation can be characterized by an average attenuation coefficient μ a special care has to be paid to the last property. Variation of chemical phase concentration with depth usually results in depth dependence on the attenuation coefficient. In this contribution a method for determination of depth distribution of a chemical phase is outlined. The method correctly takes into account the depth variation of the attenuation coefficient. The method is tested on thin oxidized Ir layers. The aim of this paper is a comparison two simple model cases with the experimental results. (authors)

Distribution of base rock depth estimated from Rayleigh wave measurement by forced vibration tests

International Nuclear Information System (INIS)

Hiroshi Hibino; Toshiro Maeda; Chiaki Yoshimura; Yasuo Uchiyama

2005-01-01

This paper shows an application of Rayleigh wave methods to a real site, which was performed to determine spatial distribution of base rock depth from the ground surface. At a certain site in Sagami Plain in Japan, the base rock depth from surface is assumed to be distributed up to 10 m according to boring investigation. Possible accuracy of the base rock depth distribution has been needed for the pile design and construction. In order to measure Rayleigh wave phase velocity, forced vibration tests were conducted with a 500 N vertical shaker and linear arrays of three vertical sensors situated at several points in two zones around the edges of the site. Then, inversion analysis was carried out for soil profile by genetic algorithm, simulating measured Rayleigh wave phase velocity with the computed counterpart. Distribution of the base rock depth inverted from the analysis was consistent with the roughly estimated inclination of the base rock obtained from the boring tests, that is, the base rock is shallow around edge of the site and gradually inclines towards the center of the site. By the inversion analysis, the depth of base rock was determined as from 5 m to 6 m in the edge of the site, 10 m in the center of the site. The determined distribution of the base rock depth by this method showed good agreement on most of the points where boring investigation were performed. As a result, it was confirmed that the forced vibration tests on the ground by Rayleigh wave methods can be useful as the practical technique for estimating surface soil profiles to a depth of up to 10 m. (authors)

Using species abundance distribution models and diversity indices for biogeographical analyses

Science.gov (United States)

Fattorini, Simone; Rigal, François; Cardoso, Pedro; Borges, Paulo A. V.

2016-01-01

We examine whether Species Abundance Distribution models (SADs) and diversity indices can describe how species colonization status influences species community assembly on oceanic islands. Our hypothesis is that, because of the lack of source-sink dynamics at the archipelago scale, Single Island Endemics (SIEs), i.e. endemic species restricted to only one island, should be represented by few rare species and consequently have abundance patterns that differ from those of more widespread species. To test our hypothesis, we used arthropod data from the Azorean archipelago (North Atlantic). We divided the species into three colonization categories: SIEs, archipelagic endemics (AZEs, present in at least two islands) and native non-endemics (NATs). For each category, we modelled rank-abundance plots using both the geometric series and the Gambin model, a measure of distributional amplitude. We also calculated Shannon entropy and Buzas and Gibson's evenness. We show that the slopes of the regression lines modelling SADs were significantly higher for SIEs, which indicates a relative predominance of a few highly abundant species and a lack of rare species, which also depresses diversity indices. This may be a consequence of two factors: (i) some forest specialist SIEs may be at advantage over other, less adapted species; (ii) the entire populations of SIEs are by definition concentrated on a single island, without possibility for inter-island source-sink dynamics; hence all populations must have a minimum number of individuals to survive natural, often unpredictable, fluctuations. These findings are supported by higher values of the α parameter of the Gambin mode for SIEs. In contrast, AZEs and NATs had lower regression slopes, lower α but higher diversity indices, resulting from their widespread distribution over several islands. We conclude that these differences in the SAD models and diversity indices demonstrate that the study of these metrics is useful for

Measurement of californium-252 gamma photons depth dose distribution in tissue equivalent material. Vol. 4

Energy Technology Data Exchange (ETDEWEB)

Fadel, M A; El-Fiki, M A; Eissa, H M; Abdel-Hafez, A; Naguib, S H [National Institute of Standards, Cairo (Egypt)

1996-03-01

Phantom of tissue equivalent material with and without bone was used measuring depth dose distribution of gamma-rays from californium-252 source. The source was positioned at center of perspex walled phantom. Depth dose measurements were recorded for X, Y and Z planes at different distances from source. TLD 700 was used for measuring the dose distribution. Results indicate that implantation of bone in tissue equivalent medium cause changes in the gamma depth dose distribution which varies according to variation in bone geometry. 9 figs.

On the statistical mechanics of species abundance distributions.

Science.gov (United States)

Bowler, Michael G; Kelly, Colleen K

2012-09-01

A central issue in ecology is that of the factors determining the relative abundance of species within a natural community. The proper application of the principles of statistical physics to species abundance distributions (SADs) shows that simple ecological properties could account for the near universal features observed. These properties are (i) a limit on the number of individuals in an ecological guild and (ii) per capita birth and death rates. They underpin the neutral theory of Hubbell (2001), the master equation approach of Volkov et al. (2003, 2005) and the idiosyncratic (extreme niche) theory of Pueyo et al. (2007); they result in an underlying log series SAD, regardless of neutral or niche dynamics. The success of statistical mechanics in this application implies that communities are in dynamic equilibrium and hence that niches must be flexible and that temporal fluctuations on all sorts of scales are likely to be important in community structure. Copyright © 2012 Elsevier Inc. All rights reserved.

Phase pupil functions for focal-depth enhancement derived from a Wigner distribution function.

Science.gov (United States)

Zalvidea, D; Sicre, E E

1998-06-10

A method for obtaining phase-retardation functions, which give rise to an increase of the image focal depth, is proposed. To this end, the Wigner distribution function corresponding to a specific aperture that has an associated small depth of focus in image space is conveniently sheared in the phase-space domain to generate a new Wigner distribution function. From this new function a more uniform on-axis image irradiance can be accomplished. This approach is illustrated by comparison of the imaging performance of both the derived phase function and a previously reported logarithmic phase distribution.

Distribution and abundance of phytobenthic communities: Implications for connectivity and ecosystem functioning in a Black Sea Marine Protected Area

Science.gov (United States)

Berov, Dimitar; Todorova, Valentina; Dimitrov, Lubomir; Rinde, Eli; Karamfilov, Ventzislav

2018-01-01

The distribution and abundance of macroalgal communities in a Marine Protected Area (MPA) along the Bulgarian Black Sea coast were mapped and quantified, with particular focus on the previously unstudied P. crispa lower-infralittoral communities on Ostrea edulis biogenic reefs. Data from high resolution geophysical substrate mapping were combined with benthic community observations from georeferenced benthic photographic surveys and sampling. Multivariate analysis identified four distinct assemblages of lower-infralittoral macroalgal communities at depths between 10 and 17 m, dominated by Phyllophora crispa, Apoglossum ruscifoluim, Zanardinia typus and Gelidium spp. Maxent software analysis showed distinct preferences of the identified communities to areas with specific ranges of depth, inclination and curvature, with P. crispa more frequently occurring on vertical oyster biogenic reef structures. By combining production rates from literature, biomass measurements and the produced habitat maps, the highest proportion of primary production and DOC release was shown for the upper infralittoral Cystoseira barbata and Cystoseira bosphorica, followed by the production of the lower-infralittoral macroalgae. The observed distribution of P. crispa within the studied MPA was related to the network of Natura 2000 maritime MPAs along the Bulgarian Black Sea coast, which indicated that the connectivity of the populations of the species within the established network is insufficient within this cell of ecosystem functioning.

Resource abundance and distribution drive bee visitation within developing tropical urban landscapes

Directory of Open Access Journals (Sweden)

Wojcik, Victoria

2011-06-01

Full Text Available Urban landscapes include a mix of biotic and anthropogenic elements that can interact with and influence species occurrence and behaviour. In order to outline the drivers of bee (Hymenoptera: Apoidea occurrence in tropical urban landscapes, foraging patterns and community characteristics were examined at a common and broadly attractive food resource, Tecoma stans (Bignoniaceae. Bee visitation was monitored at 120 individual resources in three cities from June 2007 to March 2009. Resource characteristics, spatial distribution, and other local and regional landscape variables were assessed and then used to develop descriptive regression models of forager visitation. The results indicated that increased bee abundance and taxon richness consistently correlated with increased floral abundance. Resource distribution was also influential, with more spatially aggregated resources receiving more foragers. Individual bee guilds had differential responses to the variables tested, but the significant impact of increased floral abundance was generally conserved. Smaller bodied bee species responded to floral abundance, resource structure, and proximity to natural habitats, suggesting that size-related dispersal abilities structure occurrence patterns in this guild. Larger bees favoured spatially aggregated resources in addition to increased floral abundance, suggesting an optimization of foraging energetics. The impact of the urban matrix was minimal and was only seen in generalist feeders (African honey bees. The strongly resource-driven foraging dynamics described in this study can be used to inform conservation and management practices in urban landscapes.

Measurement of moisture depth distribution in composite materials using positron lifetime technique

International Nuclear Information System (INIS)

Singh, J.J.; Holt, W.H.; Mock, W. Jr.; Mall, G.H.

1980-01-01

Fiber-reinforced resin matrix composites reportedly suffer significant degradation in their mechanical properties when exposed to hot, moist, environments for extended periods. Moisture weakens the fiber matrix bond as well as the matrix shear strength. An important factor in determining the extent of degradation is the depth distribution of moisture in the resin matrix. Despite the importance of measuring moisture distribution and its effects on composite material properties, not enough data are available on suitable nondestructive techniques for detecting and measuring moisture diffusion in organic composite materials. This paper addresses itself to the problem of measuring the moisture content of such materials, with special emphasis on its depth distribution, using positron lifetime technique

Reconstruction of original indium distribution in InGaAs quantum wells from experimental SIMS depth profiles

Energy Technology Data Exchange (ETDEWEB)

Kudriavtsev, Yu., E-mail: yuriyk@cinvestav.mx [Departamento Ingeniería Eléctrica – SEES, CINVESTAV-IPN, Av. IPN #2508, D.F., México (Mexico); Asomoza, R. [Departamento Ingeniería Eléctrica – SEES, CINVESTAV-IPN, Av. IPN #2508, D.F., México (Mexico); Gallardo-Hernandez, S.; Ramirez-Lopez, M.; Lopez-Lopez, M. [Departamento de Física, CINVESTAV-IPN, México (Mexico); Nevedomsky, V.; Moiseev, K. [Ioffe Physical Technical Institute, S-Petersburg (Russian Federation)

2014-11-15

Depth profiling analysis of InGaAs/GaAs hetero-structures grown by MBE on GaAs (0 0 1) substrates is reported. A novel two-step procedure for de-convolving experimental SIMS depth distribution is employed and the original In distribution in InGaAs quantum wells (QW) is estimated. The QW thickness calculated from the de-convolved profiles is shown to be in good agreement with the cross-sectional TEM images. The experimental In depth profile is shifted from the original In distribution due to the ion mixing process during depth profiling analysis. It is shown that the de-convolution procedure is suitable for reconstruction of the original QW width and depth by SIMS even for relatively high primary ion energies.

Drivers of abundance and spatial distribution of reef-associated sharks in an isolated atoll reef system.

Directory of Open Access Journals (Sweden)

David M Tickler

Full Text Available We investigated drivers of reef shark demography across a large and isolated marine protected area, the British Indian Ocean Territory Marine Reserve, using stereo baited remote underwater video systems. We modelled shark abundance against biotic and abiotic variables at 35 sites across the reserve and found that the biomass of low trophic order fish (specifically planktivores had the greatest effect on shark abundance, although models also included habitat variables (depth, coral cover and site type. There was significant variation in the composition of the shark assemblage at different atolls within the reserve. In particular, the deepest habitat sampled (a seamount at 70-80m visited for the first time in this study recorded large numbers of scalloped hammerhead sharks (Sphyrna lewini not observed elsewhere. Size structure of the most abundant and common species, grey reef sharks (Carcharhinus amblyrhynchos, varied with location. Individuals at an isolated bank were 30% smaller than those at the main atolls, with size structure significantly biased towards the size range for young of year (YOY. The 18 individuals judged to be YOY represented the offspring of between four and six females, so, whilst inconclusive, these data suggest the possible use of a common pupping site by grey reef sharks. The importance of low trophic order fish biomass (i.e. potential prey in predicting spatial variation in shark abundance is consistent with other studies both in marine and terrestrial systems which suggest that prey availability may be a more important predictor of predator distribution than habitat suitability. This result supports the need for ecosystem level rather than species-specific conservation measures to support shark recovery. The observed spatial partitioning amongst sites for species and life-stages also implies the need to include a diversity of habitats and reef types within a protected area for adequate protection of reef-associated shark

Comparison of the depth distribution processes for 137Cs and 210Pbex in cultivated soils

International Nuclear Information System (INIS)

Zhang Yunqi; Zhang Xinbao; Long Yi; He Xiubin; Yu Xingxiu

2012-01-01

This paper focuses on the different processes of 137 Cs and 210 Pb ex depth distribution in cultivated soils. In view of their different fallout deposition processes, considering radionuclide will diffuse from the plough layer to the plough pan layer duo to the concentration gradient between the two layers, the 137 Cs and 210 Pb ex depth distribution processes were theoretically derived. Additionally, the theoretical derivation was verified by the measured 137 Cs and 210 Pb ex values in the soil core collected from wheat field in Fujianzhuang, Shanxi Province, China, and the 137 Cs and 210 Pb ex concentrations variation with depth in soils of the wheat field was explained rationally. The 137 Cs depth distribution state in cultivated soils will consistently vary with time due to 137 Cs continual decay and diffusion as an artificial radionuclide without sustainable fallout input since 1960s. In contrast, the 210 Pb ex depth distribution in cultivated soils will achieve steady state because of sustainable deposition of the naturally occurring 210 Pb ex fallout, and it can be concluded that the differences between the theoretical and the measured values, especially for 210 Pb ex , might be associated with the history of plough depth variation or LUCC. (authors)

Distribution, abundance, and diversity of stream fishes under variable environmental conditions

Science.gov (United States)

Christopher M. Taylor; Thomas L. Holder; Richard A. Fiorillo; Lance R. Williams; R. Brent Thomas; Melvin L. Warren

2006-01-01

The effects of stream size and flow regime on spatial and temporal variability of stream fish distribution, abundance, and diversity patterns were investigated. Assemblage variability and species richness were each significantly associated with a complex environmental gradient contrasting smaller, hydrologically variable stream localities with larger localities...

Abundance and distribution of northern squawfish, walleyes, and smallmouth bass in John Day Reservoir, Columbia river

International Nuclear Information System (INIS)

Beamesderfer, R.C.; Rieman, B.E.

1991-01-01

The authors used mark-recapture and catch-per-unit effort data to estimate abundances and distributions of three potential predators on juvenile salmonids migrating through John Day Reservoir in 1984-1986. The northern squawfish Ptychocheilus oregonensis was the most abundant predator (estimated population: 85, 316), followed by smallmouth bass Micropterus dolomieu (34,954) and walleye Stizostedion vitreum (15,168). Because of uncertainty in sampling and assumption of the mark-recapture estimator, the combined abundance of these three predators could lie between 50,000 and 500,000. They believe, however, that bias is probably negative, and that any errors should result in conservative estimates. Northern squawfish were common reservoir-wide, but large concentrations occurred immediately below McNary Dam near the head of John Day Reservoir. Walleyes were largely restricted to the upper third of the reservoir, whereas the number of smallmouth bass increased progressively downriver. As judged by abundance and distribution, northern squawfish have by far the greatest potential for predation on juvenile salmonids. They also expect predation to be unevenly distributed in time and space as a result of variations in the number and distribution of predators

Environmental distribution and abundance of the facultative methanotroph Methylocella

OpenAIRE

Rahman, Md Tanvir; Crombie, Andrew; Chen, Yin; Stralis-Pavese, Nancy; Bodrossy, Levente; Meir, Patrick; McNamara, Niall P; Murrell, J Colin

2010-01-01

Methylocella spp. are facultative methanotrophs, which are able to grow not only on methane but also on multicarbon substrates such as acetate, pyruvate or malate. Methylocella spp. were previously thought to be restricted to acidic soils such as peatlands, in which they may have a key role in methane oxidation. There is little information on the abundance and distribution of Methylocella spp. in the environment. New primers were designed, and a real-time quantitative PCR method was developed...

Momentum distribution at great depths when electron axial channeling

International Nuclear Information System (INIS)

Khokonov, M.Kh.; Tuguz, F.K.

1989-01-01

The electron distribution in momenta during axial channeling in thick monocrystals in great depths is estimated. The estimate was carried out with respect to the fact that due to diffusion the angular momentum of the electron can change only in a limited region of phase space and that multiple scattering only takes place on thermal oscillations of nuclei of the crystal lattice. It is shown that in thick monocrystals the distribution in momenta can be considered uniform on the greater part of the way of channeled electrons which can simplity the qualitative consideration of spectral-angular characteristics forming during this radiation

Correlation between hypocenter depth, antecedent precipitation and earthquake-induced landslide spatial distribution

Science.gov (United States)

Fukuoka, Hiroshi; Watanabe, Eisuke

2017-04-01

Since Keefer published the paper on earthquake magnitude and affected area, maximum epicentral/fault distance of induced landslide distribution in 1984, showing the envelope of plots, a lot of studies on this topic have been conducted. It has been generally supposed that landslides have been triggered by shallow quakes and more landslides are likely to occur with heavy rainfalls immediately before the quake. In order to confirm this, we have collected 22 case records of earthquake-induced landslide distribution in Japan and examined the effect of hypocenter depth and antecedent precipitation. Earthquake magnitude by JMA (Japan Meteorological Agency) of the cases are from 4.5 to 9.0. Analysis on hycpocenter depth showed the deeper quake cause wider distribution. Antecedent precipitation was evaluated using the Soil Water Index (SWI), which was developed by JMA for issuing landslide alert. We could not find meaningful correlation between SWI and the earthquake-induced landslide distribution. Additionally, we found that smaller minimum size of collected landslides results in wider distribution especially between 1,000 to 100,000 m2.

Hierarchical spatial models for predicting pygmy rabbit distribution and relative abundance

Science.gov (United States)

Wilson, T.L.; Odei, J.B.; Hooten, M.B.; Edwards, T.C.

2010-01-01

Conservationists routinely use species distribution models to plan conservation, restoration and development actions, while ecologists use them to infer process from pattern. These models tend to work well for common or easily observable species, but are of limited utility for rare and cryptic species. This may be because honest accounting of known observation bias and spatial autocorrelation are rarely included, thereby limiting statistical inference of resulting distribution maps. We specified and implemented a spatially explicit Bayesian hierarchical model for a cryptic mammal species (pygmy rabbit Brachylagus idahoensis). Our approach used two levels of indirect sign that are naturally hierarchical (burrows and faecal pellets) to build a model that allows for inference on regression coefficients as well as spatially explicit model parameters. We also produced maps of rabbit distribution (occupied burrows) and relative abundance (number of burrows expected to be occupied by pygmy rabbits). The model demonstrated statistically rigorous spatial prediction by including spatial autocorrelation and measurement uncertainty. We demonstrated flexibility of our modelling framework by depicting probabilistic distribution predictions using different assumptions of pygmy rabbit habitat requirements. Spatial representations of the variance of posterior predictive distributions were obtained to evaluate heterogeneity in model fit across the spatial domain. Leave-one-out cross-validation was conducted to evaluate the overall model fit. Synthesis and applications. Our method draws on the strengths of previous work, thereby bridging and extending two active areas of ecological research: species distribution models and multi-state occupancy modelling. Our framework can be extended to encompass both larger extents and other species for which direct estimation of abundance is difficult. ?? 2010 The Authors. Journal compilation ?? 2010 British Ecological Society.

The Spatial Variability of Beryllium-7 Depth Distribution Study

International Nuclear Information System (INIS)

Jalal Sharib; Zainudin Othman; Dainee Nor Fardzila Ahmad Tugi; Noor Fadzilah Yusof; Mohd Tarmizi Ishak

2015-01-01

The objective of this paper is to study the spatial variability of 7 Be depth evolution in soil profile at two different sampling sites. The soil samples have been collected by using metal core in bare area in Bangi, Selangor and Timah Tasoh, Perlis , Malaysia. Two composite core samples for each sampling sites has been sectioned into 2 mm increments to a depth of 4 cm and oven dried at 45- 60 degree Celsius and gently desegregated. These two composite spatial samples are passed through a < 2 mm sieve and packed into proper geometry plastic container for 7 Be analysis by using gamma spectrometry with a 24-hour count time. From the findings, the 7 Be content in the soil samples from Bangi, Selangor study area is distributed lower depth penetration into the soil profile than Timah Tasoh, Perlis catchment due to many factors such as precipitation (fallout) and others. However, the spatial variability from both samples study area is also decreases exponentially with depth and is confined within the top few centimeters and similar with other works been reported (Blake et al., (2000) and Walling et al.,(2008). Furthermore, a detailed discussion from this study findings will be in full papers. (author)

Modelling chemical abundance distributions for dwarf galaxies in the Local Group: the impact of turbulent metal diffusion

Science.gov (United States)

Escala, Ivanna; Wetzel, Andrew; Kirby, Evan N.; Hopkins, Philip F.; Ma, Xiangcheng; Wheeler, Coral; Kereš, Dušan; Faucher-Giguère, Claude-André; Quataert, Eliot

2018-02-01

We investigate stellar metallicity distribution functions (MDFs), including Fe and α-element abundances, in dwarf galaxies from the Feedback in Realistic Environment (FIRE) project. We examine both isolated dwarf galaxies and those that are satellites of a Milky Way-mass galaxy. In particular, we study the effects of including a sub-grid turbulent model for the diffusion of metals in gas. Simulations that include diffusion have narrower MDFs and abundance ratio distributions, because diffusion drives individual gas and star particles towards the average metallicity. This effect provides significantly better agreement with observed abundance distributions in dwarf galaxies in the Local Group, including small intrinsic scatter in [α/Fe] versus [Fe/H] of ≲0.1 dex. This small intrinsic scatter arises in our simulations because the interstellar medium in dwarf galaxies is well mixed at nearly all cosmic times, such that stars that form at a given time have similar abundances to ≲0.1 dex. Thus, most of the scatter in abundances at z = 0 arises from redshift evolution and not from instantaneous scatter in the ISM. We find similar MDF widths and intrinsic scatter for satellite and isolated dwarf galaxies, which suggests that environmental effects play a minor role compared with internal chemical evolution in our simulations. Overall, with the inclusion of metal diffusion, our simulations reproduce abundance distribution widths of observed low-mass galaxies, enabling detailed studies of chemical evolution in galaxy formation.

Abundance and distribution of the highly iterated palindrome 1 (HIP1) among prokaryotes

OpenAIRE

Delaye, Luis; Moya, Andrés

2011-01-01

We have studied the abundance and phylogenetic distribution of the Highly Iterated Palindrome 1 (HIP1) among sequenced prokaryotic genomes. We show that an overrepresentation of HIP1 is exclusive of some lineages of cyanobacteria, and that this abundance was gained only once during evolution and was subsequently lost in the lineage leading to marine pico-cyanobacteria. We show that among cyanobacterial protein sequences with annotated Pfam domains, only OpcA (glucose 6-phosphate dehydrogenase...

Distribution and abundance of skipjack (Katsuwonus pelamis larvae in eastern Brazilian waters

Directory of Open Access Journals (Sweden)

Yasunobu Matsuura

1982-01-01

Full Text Available Based on data from two ichthyoplankton surveys carried out off the eastern Brazilian coast in June and November-December 1978, the larval distribution of skipjack is discussed. Skipjack larvae were more abundant in the November-December cruise (southern hemisphere spring. They occurred mainly at stations near the margin of the continental shelf or over seamounts. Out of 240 specimens of scombrid larvae collected in this area, skipjack larvae comprised only 10.4% (25 specimens, whereas the most abundant larvae were Thunnus spp. with 68.8% (165 specimens.

Environmental distribution and abundance of the facultative methanotroph Methylocella.

Science.gov (United States)

Rahman, Md Tanvir; Crombie, Andrew; Chen, Yin; Stralis-Pavese, Nancy; Bodrossy, Levente; Meir, Patrick; McNamara, Niall P; Murrell, J Colin

2011-06-01

Methylocella spp. are facultative methanotrophs, which are able to grow not only on methane but also on multicarbon substrates such as acetate, pyruvate or malate. Methylocella spp. were previously thought to be restricted to acidic soils such as peatlands, in which they may have a key role in methane oxidation. There is little information on the abundance and distribution of Methylocella spp. in the environment. New primers were designed, and a real-time quantitative PCR method was developed and validated targeting Methylocella mmoX (encoding the α-subunit of the soluble methane monooxygenase) that allowed the quantification of Methylocella spp. in environmental samples. We also developed and validated specific PCR assays, which target 16S rRNA genes of known Methylocella spp. These were used to investigate the distribution of Methylocella spp. in a variety of environmental samples. It was revealed that Methylocella species are widely distributed in nature and not restricted to acidic environments.

Seeding method influences warm-season grass abundance and distribution but not local diversity in grassland restoration

Science.gov (United States)

Yurkonis, Kathryn A.; Wilsey, Brian J.; Moloney, Kirk A.; Drobney, Pauline; Larson, Diane L.

2010-01-01

Ecological theory predicts that the arrangement of seedlings in newly restored communities may influence future species diversity and composition. We test the prediction that smaller distances between neighboring seeds in drill seeded grassland plantings would result in lower species diversity, greater weed abundance, and larger conspecific patch sizes than otherwise similar broadcast seeded plantings. A diverse grassland seed mix was either drill seeded, which places seeds in equally spaced rows, or broadcast seeded, which spreads seeds across the ground surface, into 24 plots in each of three sites in 2005. In summer 2007, we measured species abundance in a 1 m2 quadrat in each plot and mapped common species within the quadrat by recording the most abundant species in each of 64 cells. Quadrat-scale diversity and weed abundance were similar between drilled and broadcast plots, suggesting that processes that limited establishment and controlled invasion were not affected by such fine-scale seed distribution. However, native warm-season (C4) grasses were more abundant and occurred in less compact patches in drilled plots. This difference in C4 grass abundance and distribution may result from increased germination or vegetative propagation of C4 grasses in drilled plots. Our findings suggest that local plant density may control fine-scale heterogeneity and species composition in restored grasslands, processes that need to be further investigated to determine whether seed distributions can be manipulated to increase diversity in restored grasslands.

Do abundance distributions and species aggregation correctly predict macroecological biodiversity patterns in tropical forests?

Science.gov (United States)

Wiegand, Thorsten; Lehmann, Sebastian; Huth, Andreas; Fortin, Marie‐Josée

2016-01-01

Abstract Aim It has been recently suggested that different ‘unified theories of biodiversity and biogeography’ can be characterized by three common ‘minimal sufficient rules’: (1) species abundance distributions follow a hollow curve, (2) species show intraspecific aggregation, and (3) species are independently placed with respect to other species. Here, we translate these qualitative rules into a quantitative framework and assess if these minimal rules are indeed sufficient to predict multiple macroecological biodiversity patterns simultaneously. Location Tropical forest plots in Barro Colorado Island (BCI), Panama, and in Sinharaja, Sri Lanka. Methods We assess the predictive power of the three rules using dynamic and spatial simulation models in combination with census data from the two forest plots. We use two different versions of the model: (1) a neutral model and (2) an extended model that allowed for species differences in dispersal distances. In a first step we derive model parameterizations that correctly represent the three minimal rules (i.e. the model quantitatively matches the observed species abundance distribution and the distribution of intraspecific aggregation). In a second step we applied the parameterized models to predict four additional spatial biodiversity patterns. Results Species‐specific dispersal was needed to quantitatively fulfil the three minimal rules. The model with species‐specific dispersal correctly predicted the species–area relationship, but failed to predict the distance decay, the relationship between species abundances and aggregations, and the distribution of a spatial co‐occurrence index of all abundant species pairs. These results were consistent over the two forest plots. Main conclusions The three ‘minimal sufficient’ rules only provide an incomplete approximation of the stochastic spatial geometry of biodiversity in tropical forests. The assumption of independent interspecific placements is most

Determination of hydrogen abundance in selected lunar soils

Science.gov (United States)

Bustin, Roberta

1987-01-01

Hydrogen was implanted in lunar soil through solar wind activity. In order to determine the feasibility of utilizing this solar wind hydrogen, it is necessary to know not only hydrogen abundances in bulk soils from a variety of locations but also the distribution of hydrogen within a given soil. Hydrogen distribution in bulk soils, grain size separates, mineral types, and core samples was investigated. Hydrogen was found in all samples studied. The amount varied considerably, depending on soil maturity, mineral types present, grain size distribution, and depth. Hydrogen implantation is definitely a surface phenomenon. However, as constructional particles are formed, previously exposed surfaces become embedded within particles, causing an enrichment of hydrogen in these species. In view of possibly extracting the hydrogen for use on the lunar surface, it is encouraging to know that hydrogen is present to a considerable depth and not only in the upper few millimeters. Based on these preliminary studies, extraction of solar wind hydrogen from lunar soil appears feasible, particulary if some kind of grain size separation is possible.

Survey on depth distribution of underground structures for consideration of human intrusion into TRU waste repository

International Nuclear Information System (INIS)

Sakamoto, Yoshiaki; Senoo, Muneaki; Sugimoto, Junichiro; Ohishi, Kiyotaka; Okishio, Masanori; Shimizu, Haruo.

1996-01-01

Depth distributions of some kinds of underground structure in Japan have been investigated to get an information about suitable depth of underground repository for TRU waste that is arising from reprocessing and MOX fuel fabrication plants. The underground structures investigated in this work were foundation pile of multistoried building, that of elevated expressway, that of JR shinkansen railway, tunnel of subway and wells. The major depth distribution of the underground structures except for the wells was in range from 30 to 50m, and their maximum depth was less than 100m. On the other hand, the 99% of wells was less than 300m in depth. Maximum depth of the other underground structures has been also investigated for a survey of the utilization of underground by artificial structures in Japan. (author)

Distribution and abundance of diatom species from coastal waters of Karachi, Pakistan

International Nuclear Information System (INIS)

Khokhar, F. N.; Burhan, Z.; Iqbal, P.; Abbasi, J.; Siddiqui, P.

2016-01-01

This is the first comprehensive study on the distribution and abundance of diatom species from the coastal and nearshore waters of Karachi, Pakistan, bordering northern Arabian Sea. A total of 20 genera are recorded in high abundance (Cerataulina, Chaetoceros, Coscinodiscus, Cylindrotheca, Eucampia, Guinardia, Haslea, Hemiaulus, Lauderia, Lennoxia, Leptocylindrus, Navicula, Nitzschia, Trieres, Planktoniella, Pleurosigma, Pseudo-nitzschia, Rhizosolenia, Thalassionema and Thalassiosira). The most abundant genera were observed Guinardia, Chaetoceros, Leptocylindrus, Nitzschia and Lennoxia at all stations. Manora coastal station (MI-1) had high abundance corresponding with high Chlorophyll a (130 meu gL- l) values. Minimum abundance and low chlorophyll a value (0.05μgL-l) were observed at Mubarak Village coastal station (MV-1). Diatom abundance showed significant correlation with Chlorophyll a. In present study 12 centric and 8 pennate forms were recorded and similarly high diversity of centric taxa was observed compared to pennate forms. A total of 134 species are recorded of which 40 species were observed at four stations, 31species at three stations, 23 at two stations and 40 species only at one station. The total phytoplankton and diatom peak abundance was observed during NE monsoon (winter season) associated with nutrient loading through up-sloping of nutrient rich water upwelled off of Oman during South West monsoon. Overall higher diversity was observed at Manora coastal and nearshore stations (MI-1, MI-2) indicating the influence of organic pollution loading from Layari and Malir rivers. (author)

Distribution of penaeid prawn larvae in the coastal waters of Goa

Digital Repository Service at National Institute of Oceanography (India)

Achuthankutty, C.T.; Parulekar, A.H.

distributed within the 20 m depth zone whereas those of Penaeus merguiensis and Parapenaeopsis stylifera, between 20 and 30m depth zone. Larval abundance also showed species specific seasonal variation.Statistical analysis indicated that larval and postlarval...

Nuclear method for determination of nitrogen depth distributions in single seeds. [/sup 14/N tracer technique

Energy Technology Data Exchange (ETDEWEB)

Sundqvist, B; Gonczi, L; Koersner, I; Bergman, R; Lindh, U

1974-01-01

(d,p) reactions in /sup 14/N were used for probing single kernels of seed for nitrogen content and nitrogen depth distributions. Comparison with the Kjeldahl method was made on individual peas and beans. The results were found to be strongly correlated. The technique to obtain depth distributions of nitrogen was also used on high- and low-lysine varieties of barley for which large differences in nitrogen distributions were found.

Microbiome variation in corals with distinct depth distribution ranges across a shallow-mesophotic gradient (15-85 m)

Science.gov (United States)

Glasl, Bettina; Bongaerts, Pim; Elisabeth, Nathalie H.; Hoegh-Guldberg, Ove; Herndl, Gerhard J.; Frade, Pedro R.

2017-06-01

Mesophotic coral ecosystems (MCEs) are generally poorly studied, and our knowledge of lower MCEs (below 60 m depth) is largely limited to visual surveys. Here, we provide a first detailed assessment of the prokaryotic community associated with scleractinian corals over a depth gradient to the lower mesophotic realm (15-85 m). Specimens of three Caribbean coral species exhibiting differences in their depth distribution ranges ( Agaricia grahamae, Madracis pharensis and Stephanocoenia intersepta) were collected with a manned submersible on the island of Curaçao, and their prokaryotic communities assessed using 16S rRNA gene sequencing analysis. Corals with narrower depth distribution ranges (depth-specialists) were associated with a stable prokaryotic community, whereas corals with a broader niche range (depth-generalists) revealed a higher variability in their prokaryotic community. The observed depth effects match previously described patterns in Symbiodinium depth zonation. This highlights the contribution of structured microbial communities over depth to the coral's ability to colonize a broader depth range.

Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

Directory of Open Access Journals (Sweden)

B. Ausín

2018-01-01

Full Text Available A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions. However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past

Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

Science.gov (United States)

Ausín, Blanca; Zúñiga, Diana; Flores, Jose A.; Cavaleiro, Catarina; Froján, María; Villacieros-Robineau, Nicolás; Alonso-Pérez, Fernando; Arbones, Belén; Santos, Celia; de la Granda, Francisco; Castro, Carmen G.; Abrantes, Fátima; Eglinton, Timothy I.; Salgueiro, Emilia

2018-01-01

A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions). However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past environmental conditions, of

Measurement of depth-dose distributions by means of the LiF-fluoroplastic thermoluminescent detectors

International Nuclear Information System (INIS)

Shaks, A.I.; Uryaev, I.A.; Trifonov, V.A.; Reshetnikova, L.V.

1977-01-01

Depth-dose distributions have been studied by means of thin-layer thermoluminescent detectors LiF-fluoroplast (8 mg/cm 2 ). Dosimetric characteristics of the detectors are described. They are: tissue-equivalence, dependence of sensitivity on the dose, dose rate and angle of incidence of radiation, and time-dependent storage, of the total light absorbed. Comparison of the results obtained with the measurements taken with an extrapolation chamber has demonstrated the possibility of measuring the depth-dose distributions by means of LiF-fluoroplast detectors

Distribution and abundance by larval developmental stages of Symphurus williamsi (Pleuronectiformes: Cynoglossidae in the Gulf of California

Directory of Open Access Journals (Sweden)

Gerardo Aceves-Medina

2006-06-01

Full Text Available Distribution and abundance of tonguefish larvae (Symphurus williamsi were analyzed from collections made during ten oceanographic surveys in the Gulf of California between 1984 and 1988. Larvae were found mainly during the summer months and the highest abundances were located in the warmer southern and central regions of the Gulf, but they were scarce in the northern portion. High abundance of preflexion larvae occurred in areas where the sea surface temperature was between 29 and 32°C. Distribution patterns according to developmental stage suggest spatial ontogenic segregation with the early larvae in the ocean area of the central and southern regions of the Gulf. Based on abundance of preflexion larvae as well as on signs of a short egg period of this species, spawns may occur between early and mid summer.

Community structure and function of planktonic Crenarchaeota: changes with depth in the South China Sea.

Science.gov (United States)

Hu, Anyi; Jiao, Nianzhi; Zhang, Chuanlun L

2011-10-01

Marine Crenarchaeota represent a widespread and abundant microbial group in marine ecosystems. Here, we investigated the abundance, diversity, and distribution of planktonic Crenarchaeota in the epi-, meso-, and bathypelagic zones at three stations in the South China Sea (SCS) by analysis of crenarchaeal 16S rRNA gene, ammonia monooxygenase gene amoA involved in ammonia oxidation, and biotin carboxylase gene accA putatively involved in archaeal CO(2) fixation. Quantitative PCR analyses indicated that crenarchaeal amoA and accA gene abundances varied similarly with archaeal and crenarchaeal 16S rRNA gene abundances at all stations, except that crenarchaeal accA genes were almost absent in the epipelagic zone. Ratios of the crenarchaeal amoA gene to 16S rRNA gene abundances decreased ~2.6 times from the epi- to bathypelagic zones, whereas the ratios of crenarchaeal accA gene to marine group I crenarchaeal 16S rRNA gene or to crenarchaeal amoA gene abundances increased with depth, suggesting that the metabolism of Crenarchaeota may change from the epi- to meso- or bathypelagic zones. Denaturing gradient gel electrophoresis profiling of the 16S rRNA genes revealed depth partitioning in archaeal community structures. Clone libraries of crenarchaeal amoA and accA genes showed two clusters: the "shallow" cluster was exclusively derived from epipelagic water and the "deep" cluster was from meso- and/or bathypelagic waters, suggesting that niche partitioning may take place between the shallow and deep marine Crenarchaeota. Overall, our results show strong depth partitioning of crenarchaeal populations in the SCS and suggest a shift in their community structure and ecological function with increasing depth.

Bacteriophage Distributions and Temporal Variability in the Ocean’s Interior

Directory of Open Access Journals (Sweden)

Elaine Luo

2017-11-01

Full Text Available Bacteriophages are numerically the most abundant DNA-containing entities in the oligotrophic ocean, yet how specific phage populations vary over time and space remains to be fully explored. Here, we conducted a metagenomic time-series survey of double-stranded DNA phages throughout the water column in the North Pacific Subtropical Gyre, encompassing 1.5 years from depths of 25 to 1,000 m. Viral gene sequences were identified in assembled metagenomic samples, yielding an estimated 172,385 different viral gene families. Viral marker gene distributions suggested that lysogeny was more prevalent at mesopelagic depths than in surface waters, consistent with prior prophage induction studies using mitomycin C. A total of 129 ALOHA viral genomes and genome fragments from 20 to 108 kbp were selected for further study, which represented the most abundant phages in the water column. Phage genotypes displayed discrete population structures. Most phages persisted throughout the time-series and displayed a strong depth structure that mirrored the stratified depth distributions of co-occurring bacterial taxa in the water column. Mesopelagic phages were distinct from surface water phages with respect to diversity, gene content, putative life histories, and temporal persistence, reflecting depth-dependent differences in host genomic architectures and phage reproductive strategies. The spatiotemporal distributions of the most abundant open-ocean bacteriophages that we report here provide new insight into viral temporal persistence, life history, and virus-host-environment interactions throughout the open-ocean water column.

Prickly business: abundance of sea urchins on breakwaters and coral reefs in Dubai.

Science.gov (United States)

Bauman, Andrew G; Dunshea, Glenn; Feary, David A; Hoey, Andrew S

2016-04-30

Echinometra mathaei is a common echinoid on tropical reefs and where abundant plays an important role in the control of algal communities. Despite high prevalence of E. mathaei on southern Persian/Arabian Gulf reefs, their abundance and distribution is poorly known. Spatial and temporal patterns in population abundance were examined at 12 sites between breakwater and natural reef habitats in Dubai (UAE) every 3 months from 2008 to 2010. Within the breakwater habitat, densities were greatest at shallow wave-exposed sites, and reduced with both decreasing wave-exposure and increasing depth. Interestingly, E. mathaei were significantly more abundant on exposed breakwaters than natural reef sites, presumably due to differences in habitat structure and benthic cover. Population abundances differed seasonally, with peak abundances during summer (July-September) and lower abundances in winter (December-February). Seasonal fluctuations are likely the result of peak annual recruitment pulses coupled with increased fish predation from summer to winter. Copyright © 2015 Elsevier Ltd. All rights reserved.

Depth distribution of damage obtained by Rutherford backscattering combined with channeling

International Nuclear Information System (INIS)

Behrisch, R.; Roth, J.

1976-01-01

The different approaches to determine depth distributions of damage in solids by Rutherford backscattering combined with channeling are reviewed. These methods are best applicable for damage introduced by ion bombardment. Most investigations up to now have been done at semiconductors where the ion damage seems to be more suited for analysis by this method than the ion damage in metals. The quantity used for getting depth profiles is mostly the increase in minimum yields in single alignment Rutherford backscattering, while only few measurements have been done at double alignment and at slight misalignment, i.e., the sides of the channeling dips

The calculation of electron depth-dose distributions in multilayer medium

International Nuclear Information System (INIS)

Wang Chuanshan; Xu Mengjie; Li Zhiliang; Feng Yongxiang; Li Panlin

1989-01-01

Energy deposition in multilayer medium and the depth dose distribution in the layers are studied. Based on semi-empirical calculation of electron energy absorption in matter with EDMULT program of Tabata and Ito, further work has been carried out to extend the computation to multilayer composite material. New program developed in this paper makes IBM-PC compatible with complicated electron dose calculations

Changing distribution and abundance of the malaria vector Anopheles merus in Mpumalanga Province, South Africa.

Science.gov (United States)

Mbokazi, F; Coetzee, M; Brooke, B; Govere, J; Reid, A; Owiti, P; Kosgei, R; Zhou, S; Magagula, R; Kok, G; Namboze, J; Tweya, H; Mabuza, A

2018-04-25

Background: The malaria vector Anopheles merus occurs in the Mpumalanga Province of South Africa. As its contribution to malaria transmission in South Africa has yet to be ascertained, an intensification of surveillance is necessary to provide baseline information on this species. The aim of this study was therefore to map An. merus breeding sites in the Ehlanzeni District of Mpumalanga Province and to assess qualitative trends in the distribution and relative abundance of this species over a 9-year period. Methods: The study was carried out during the period 2005-2014 in the four high-risk municipalities of Ehlanzeni District. Fifty-two breeding sites were chosen from all water bodies that produced anopheline mosquitoes. The study data were extracted from historical entomological records that are captured monthly. Results: Of the 15 058 Anopheles mosquitoes collected, 64% were An. merus. The abundance and distribution of An. merus increased throughout the four municipalities in Ehlanzeni District during the study period. Conclusion: The expanded distribution and increased abundance of An. merus in the Ehlanzeni District may contribute significantly to locally acquired malaria in Mpumalanga Province, likely necessitating the incorporation of additional vector control methods specifically directed against populations of this species.

Land use determinants of small mammal abundance and distribution in a plague endemic area of Lushoto District, Tanzania.

Science.gov (United States)

Hieronimo, Proches; Kimaro, Didas N; Kihupi, Nganga I; Gulinck, Hubert; Mulungu, Loth S; Msanya, Balthazar M; Leirs, Herwig; Deckers, Jozef A

2014-07-01

Small mammals are considered to be involved in the transmission cycle of bubonic plague, still occurring in different parts of the world, including the Lushoto District in Tanzania. The objective of this study was to determine the relationship between land use types and practices and small mammal abundance and distribution. A field survey was used to collect data in three landscapes differing in plague incidences. Data collection was done both in the wet season (April-June 2012) and dry season (August-October 2012). Analysis of variance and Boosted Regression Trees (BRT) modelling technique were used to establish the relationship between land use and small mammal abundance and distribution. Significant variations (p ≤ 0.05) of small mammal abundance among land use types were identified. Plantation forest with farming, natural forest and fallow had higher populations of small mammals than the other aggregated land use types. The influence of individual land use types on small mammal abundance level showed that, in both dry and wet seasons, miraba and fallow tended to favour small mammals' habitation whereas land tillage practices had the opposite effect. In addition, during the wet season crop types such as potato and maize appeared to positively influence the distribution and abundance of small mammals which was attributed to both shelter and food availability. Based on the findings from this study it is recommended that future efforts to predict and map spatial and temporal human plague infection risk at fine scale should consider the role played by land use and associated human activities on small mammal abundance and distribution.

Modeling Distribution and Abundance of Antarctic Baleen Whales Using Ships of Opportunity

Directory of Open Access Journals (Sweden)

Rob Williams

2006-06-01

Full Text Available Information on animal abundance and distribution is at the cornerstone of many wildlife and conservation strategies. However, these data can be difficult and costly to obtain for cetacean species. The expense of sufficient ship time to conduct design-unbiased line transect surveys may be simply out of reach for researchers in many countries, which nonetheless grapple with problems of conservation of endangered species, by-catch of small cetaceans in commercial fisheries, and progression toward ecosystem-based fisheries management. Recently developed spatial modeling techniques show promise for estimating wildlife abundance using non-randomized surveys, but have yet to receive much field-testing in areas where designed surveys have also been conducted. Effort and sightings data were collected along 9 650 km of transects aboard ships of opportunity in the Southern Ocean during the austral summers of 2000-2001 and 2001-2002. Generalized additive models with generalized cross-validation were used to express heterogeneity of cetacean sightings as functions of spatial covariates. Models were used to map predicted densities and to estimate abundance of humpback, minke, and fin whales in the Drake Passage and along the Antarctic Peninsula. All species' distribution maps showed strong density gradients, which were robust to jackknife resampling when each of 14 trips was removed sequentially with replacement. Looped animations of model predictions of whale density illustrate uncertainty in distribution estimates in a way that is informative to non-scientists. The best abundance estimate for humpback whales was 1 829 (95% CI: 978-3 422. Abundance of fin whales was 4 487 (95% CI: 1 326-15 179 and minke whales was 1,544 (95% CI: 1,221-1,953. These estimates agreed roughly with those reported from a designed survey conducted in the region during the previous austral summer. These estimates assumed that all animals on the trackline were detected, but

Microplastic Distribution at Different Sediment Depths in an Urban Estuary

Directory of Open Access Journals (Sweden)

Kathryn A. Willis

2017-12-01

Full Text Available As plastic production increases, so to do the threats from plastic pollution. Microplastics (defined as plastics <5 mm are a subset of marine debris about which we know less than we do of larger debris items, though they are potentially ubiquitous in the marine environment. To quantify the distribution and change in microplastic densities through time, we sampled sediment cores from an estuary in Tasmania, Australia. We hypothesized that the type, distribution and abundance of microplastics observed would be associated with increasing plastic production, coastal population growth, and proximity to urban water outflows and local hydrodynamics. Sediments ranging from the year 1744 to 2004 were sub-sampled from each core. We observed microplastics in every sample, with greater plastic frequencies found in the upper (more recent sediments. This time trend of microplastic accumulation matched that of global plastic production and coastal population growth. We observed that fibers were the most abundant type of microplastic in our samples. These fibers were present in sediments that settled prior to the presence of plastics in the environment. We propose a simple statistical model to estimate the level of contamination in our samples. We suggest that the current trend in the literature suggesting very high loads of fibers, particularly in remote locations such as the deep seafloor, may be largely due to contamination.

Species composition, abundance and distribution of hydromedusae from Dharamtar estuarine system, adjoining Bombay Harbour

Digital Repository Service at National Institute of Oceanography (India)

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

Species composition, abundance and distribution of hydromedusae from Dharamtar estuarine system, adjoining Bombay Harbour, Maharashtra, India were investigated during 1984-1985. Twenty six species belonging to 19 genera were obtained from this area...

Spatio-temporal distribution of Diaphanosoma brachyurum (Cladocera: Sididae in freshwater reservoir ecosystems: importance of maximum water depth and macrophyte beds for avoidance of fish predation

Directory of Open Access Journals (Sweden)

Jong-Yun Choi

2014-10-01

Full Text Available In empirical studies, Cladocera is commonly utilized as a primary food source for predators such as fish, thus, predator avoidance are important strategies to sustain their population in freshwater ecosystems. In this study, we tested the hypothesis that water depth is an important factor in determining the spatial distribution of Diaphanosoma brachyurum Liévin, 1848 in response to fish predation. Quarterly monitoring was implemented at three water layers (i.e., water surface and middle and bottom layers in 21 reservoirs located in the southeastern part of South Korea. D. brachyurum individuals were frequently observed at the study sites and exhibited different spatial patterns of distribution in accordance with the maximum depth of the reservoirs. In the reservoirs with a maximum depth of more than 6 m, high densities of D. brachyurum were observed in the bottom layers; however, in the shallower reservoirs (maximum depth <6 m, D. brachyurum were concentrated in the surface layer. Moreover, during additional surveys, we observed a trend in which D. brachyurum densities increased as the maximum depth or macrophyte biomass increased. Gut contents analysis revealed that predatory fishes in each reservoir frequently consumed D. brachyurum; however, the consumption rate abruptly decreased in reservoirs where the maximum depth was more than 11 m or in the shallow reservoirs supporting a macrophyte bed. Interestingly, the reservoirs more than 11-m depth supported high densities of D. brachyurum in the bottom layer and in the surface macrophyte bed. Based on these results, reservoirs with a maximum depth of more than 11 m or those with a macrophyte bed may provide a refuge for D. brachyurum to avoid fish predation. Compared with other cladoceran species, D. brachyurum readily exploits various types of refugia (in this study, the deep layer or surface macrophyte bed, which may help explain why this species is abundant in various types of reservoirs.

Seasonal distribution and abundance of cetaceans within French waters- Part II: The Bay of Biscay and the English Channel

Science.gov (United States)

Laran, Sophie; Authier, Matthieu; Blanck, Aurélie; Doremus, Ghislain; Falchetto, Hélène; Monestiez, Pascal; Pettex, Emeline; Stephan, Eric; Van Canneyt, Olivier; Ridoux, Vincent

2017-07-01

From the Habitat Directive to the recent Marine Strategy Framework Directive, the conservation status of cetaceans in European water has been of concern for over two decades. In this study, a seasonal comparison of the abundance and distribution of cetaceans was carried out in two contrasted regions of the Eastern North Atlantic, the Bay of Biscay and the English Channel. Estimates were obtained in the two sub-regions (375,000 km²) from large aerial surveys conducted in the winter (November 2011 to February 2012) and in the summer (May to August 2012). The most abundant species encountered in the Channel, the harbour porpoise, displayed strong seasonal variations in its distribution but a stable abundance (18,000 individuals, CV=30%). In the Bay of Biscay, abundance and distribution patterns of common / striped dolphins varied from 285,000 individuals (95% CI: 174,000-481,000) in the winter, preferentially distributed close to the shelf break, to 494,000 individuals (95% CI: 342,000-719,000) distributed beyond the shelf break in summer. Baleen whales also exhibited an increase of their density in summer. Seasonal abundances of bottlenose dolphins were quite stable, with a large number of 'pelagic' encounters offshore in winter. No significant seasonal difference was estimated for pilot whales and sperm whale. These surveys provided baseline estimates to inform policies to be developed, or for existing conservation instruments such as the Habitats Directive. In addition, our results supported the hypothesis of a shift in the summer distributions of some species such as harbour porpoise and minke whale in European waters.

Distribution and relative abundance of the marine catfish (Siluriformes, Ariidae) in Sepetiba Bay, Rio de Janeiro

OpenAIRE

Azevedo, Márcia Cristina Costa de; Araújo, Francisco Gerson; Cruz Filho, Antônio Gomes da; Santos, Alexandre Clístenes de Alcântara

1998-01-01

Marine catfish (Ariidae) are abundant resources in otter trawl fisheries carried out at Sepetiba Bay, Rio de Janeiro (Lat. 22º54, 23º04'S; Long. 43º34 44º10'W). Relative abundance and distribution were assessed, based in 158 fishing sampling at seven sites in the Bay, between July-1993 e June-1996. Five species were recorded in the following abundance rank order: Genidens genidens (Valenciennes, 1839), Caihorops spixii (Agassiz,1829), Sciadeichthys lunisculis (Valenciennes, 1840), Nelunia bar...

Demonstration of a collimated in situ method for determining depth distributions using gamma-ray spectrometry

CERN Document Server

Benke, R R

2002-01-01

In situ gamma-ray spectrometry uses a portable detector to quantify radionuclides in materials. The main shortcoming of in situ gamma-ray spectrometry has been its inability to determine radionuclide depth distributions. Novel collimator designs were paired with a commercial in situ gamma-ray spectrometry system to overcome this limitation for large area sources. Positioned with their axes normal to the material surface, the cylindrically symmetric collimators limited the detection of un attenuated gamma-rays from a selected range of polar angles (measured off the detector axis). Although this approach does not alleviate the need for some knowledge of the gamma-ray attenuation characteristics of the materials being measured, the collimation method presented in this paper represents an absolute method that determines the depth distribution as a histogram, while other in situ methods require a priori knowledge of the depth distribution shape. Other advantages over previous in situ methods are that this method d...

Lutzomyia longipalpis Presence and Abundance Distribution at Different Micro-spatial Scales in an Urban Scenario.

Science.gov (United States)

Santini, María Soledad; Utgés, María Eugenia; Berrozpe, Pablo; Manteca Acosta, Mariana; Casas, Natalia; Heuer, Paola; Salomón, O Daniel

2015-01-01

The principal objective of this study was to assess a modeling approach to Lu. longipalpis distribution in an urban scenario, discriminating micro-scale landscape variables at microhabitat and macrohabitat scales and the presence from the abundance of the vector. For this objective, we studied vectors and domestic reservoirs and evaluated different environmental variables simultaneously, so we constructed a set of 13 models to account for micro-habitats, macro-habitats and mixed-habitats. We captured a total of 853 sandflies, of which 98.35% were Lu. longipalpis. We sampled a total of 197 dogs; 177 of which were associated with households where insects were sampled. Positive rK39 dogs represented 16.75% of the total, of which 47% were asymptomatic. Distance to the border of the city and high to medium density vegetation cover ended to be the explanatory variables, all positive, for the presence of sandflies in the city. All variables in the abundance model ended to be explanatory, trees around the trap, distance to the stream and its quadratic, being the last one the only one with negative coefficient indicating that the maximum abundance was associated with medium values of distance to the stream. The spatial distribution of dogs infected with L. infantum showed a heterogeneous pattern throughout the city; however, we could not confirm an association of the distribution with the variables assessed. In relation to Lu. longipalpis distribution, the strategy to discriminate the micro-spatial scales at which the environmental variables were recorded allowed us to associate presence with macrohabitat variables and abundance with microhabitat and macrohabitat variables. Based on the variables associated with Lu. longipalpis, the model will be validated in other cities and environmental surveillance, and control interventions will be proposed and evaluated in the microscale level and integrated with socio-cultural approaches and programmatic and village (mesoscale

Quantitative analysis of oxygen depth distribution by means of deuteron reaction

International Nuclear Information System (INIS)

Dyumin, A.N.; Eremin, V.K.; Konnikov, S.G.

1993-01-01

Experimentally are investigated and realized possibilities for using the reaction for quantitative determination of the depth profiles of the oxygen distribution in HTSC structures in layers up to 10 4 A. It is concluded that in the near-surface layers when profiling the oxygen content is achieved the spatial resolution of 150 A

An investigation into the population abundance distribution of mRNAs, proteins, and metabolites in biological systems.

Science.gov (United States)

Lu, Chuan; King, Ross D

2009-08-15

Distribution analysis is one of the most basic forms of statistical analysis. Thanks to improved analytical methods, accurate and extensive quantitative measurements can now be made of the mRNA, protein and metabolite from biological systems. Here, we report a large-scale analysis of the population abundance distributions of the transcriptomes, proteomes and metabolomes from varied biological systems. We compared the observed empirical distributions with a number of distributions: power law, lognormal, loglogistic, loggamma, right Pareto-lognormal (PLN) and double PLN (dPLN). The best-fit for mRNA, protein and metabolite population abundance distributions was found to be the dPLN. This distribution behaves like a lognormal distribution around the centre, and like a power law distribution in the tails. To better understand the cause of this observed distribution, we explored a simple stochastic model based on geometric Brownian motion. The distribution indicates that multiplicative effects are causally dominant in biological systems. We speculate that these effects arise from chemical reactions: the central-limit theorem then explains the central lognormal, and a number of possible mechanisms could explain the long tails: positive feedback, network topology, etc. Many of the components in the central lognormal parts of the empirical distributions are unidentified and/or have unknown function. This indicates that much more biology awaits discovery.

Significant biases affecting abundance determinations

Science.gov (United States)

Wesson, Roger

2015-08-01

I have developed two highly efficient codes to automate analyses of emission line nebulae. The tools place particular emphasis on the propagation of uncertainties. The first tool, ALFA, uses a genetic algorithm to rapidly optimise the parameters of gaussian fits to line profiles. It can fit emission line spectra of arbitrary resolution, wavelength range and depth, with no user input at all. It is well suited to highly multiplexed spectroscopy such as that now being carried out with instruments such as MUSE at the VLT. The second tool, NEAT, carries out a full analysis of emission line fluxes, robustly propagating uncertainties using a Monte Carlo technique.Using these tools, I have found that considerable biases can be introduced into abundance determinations if the uncertainty distribution of emission lines is not well characterised. For weak lines, normally distributed uncertainties are generally assumed, though it is incorrect to do so, and significant biases can result. I discuss observational evidence of these biases. The two new codes contain routines to correctly characterise the probability distributions, giving more reliable results in analyses of emission line nebulae.

Species abundance distributions in neutral models with immigration or mutation and general lifetimes.

Science.gov (United States)

Lambert, Amaury

2011-07-01

We consider a general, neutral, dynamical model of biodiversity. Individuals have i.i.d. lifetime durations, which are not necessarily exponentially distributed, and each individual gives birth independently at constant rate λ. Thus, the population size is a homogeneous, binary Crump-Mode-Jagers process (which is not necessarily a Markov process). We assume that types are clonally inherited. We consider two classes of speciation models in this setting. In the immigration model, new individuals of an entirely new species singly enter the population at constant rate μ (e.g., from the mainland into the island). In the mutation model, each individual independently experiences point mutations in its germ line, at constant rate θ. We are interested in the species abundance distribution, i.e., in the numbers, denoted I(n)(k) in the immigration model and A(n)(k) in the mutation model, of species represented by k individuals, k = 1, 2, . . . , n, when there are n individuals in the total population. In the immigration model, we prove that the numbers (I(t)(k); k ≥ 1) of species represented by k individuals at time t, are independent Poisson variables with parameters as in Fisher's log-series. When conditioning on the total size of the population to equal n, this results in species abundance distributions given by Ewens' sampling formula. In particular, I(n)(k) converges as n → ∞ to a Poisson r.v. with mean γ/k, where γ : = μ/λ. In the mutation model, as n → ∞, we obtain the almost sure convergence of n (-1) A(n)(k) to a nonrandom explicit constant. In the case of a critical, linear birth-death process, this constant is given by Fisher's log-series, namely n(-1) A(n)(k) converges to α(k)/k, where α : = λ/(λ + θ). In both models, the abundances of the most abundant species are briefly discussed.

Post- and interseismic deformation due to both localized and distributed creep at depth (Invited)

Science.gov (United States)

Hetland, E. A.; Zhang, G.; Hines, T.

2013-12-01

There are two end-member representations of the ductile lithosphere (i.e., the lower crust and uppermost mantle) commonly used in models of post- and interseismic deformation around strike-slip faults: either (1) laterally homogeneous ductile layers, with sharp contrasts in rheological properties between the layers, in which creep is distributed; or (2) discrete extensions of the fault at depth in which creep is fully localized. The most realistic representation of the ductile lithosphere on earthquake cycle time scales likely falls between these two end-members. Researchers have considered both distributed and localized creep when interpreting post- and interseismic deformation, although the two mechanisms are most commonly treated separately, with the localized creep often approximated by kinematic slip on planar faults. There are a few noteworthy models that considered the feedback between both distributed and localized creep, although those models were largely constrained to 2D geometries of infinite length faults. The thickness of shear zones in the ductile lithosphere may be comparable to the locking depth of the fault, and the existence of a deep shear zone does not preclude the possibility that some distributed creep occurs in the surrounding lithosphere. Furthermore, variations in rheology, including both rheological models and their parameters, may be more subtle than the discrete contrasts typically assumed. In this presentation, we consider models of postseismic deformation following a finite length, strike-slip fault, as well as models of interseismic deformation around an infinite length strike-slip fault. Both sets of models are capable of localized and distributed creep at depth, and use Maxwell viscoelasticity. We show that the horizontal surface velocities during the early postseismic period are most sensitive to the viscosity of the shear zone; however during much of the interseismic period the shear zone is not apparent from the surface

Species composition, distribution and abundance of chaetodontidae along reef transects in the Flores Sea

Science.gov (United States)

Adrim, Mohammad; Hutomo, Malikusworo

Observations on chaetodontid fishes were made by applying a visual census technique at 13 coral reef locations in the Flores Sea region in October and November 1984. These observations were made along 50 m transect lines, parallel to the shore or the reef edge at depths between 3 to 12 m. Twenty-three species of Chaetodontidae were observed, representing three genera: Chaetodon (20 species), Heniochus (2 species) and Forcipiger (1 species). Chaetodon kleini, C. trifasciatus, C. melannotus and C. baronessa proved to be the most abundant species, and among them C. kleini and C. trifasciatus were the most widely distributed ones. Chaetodon semeion and C. mertensi were the rarest species. The greatest number of individuals (77) was counted at station 4.268 near Tanjung Burung, Sumbawa, while the greatest number of species (14) was observed at station 4.257, north of Komodo. The lowest number of individuals (17) was counted at station 4.175 near P. Bahuluang, Salayer, while station 4.251 near Teluk Slawi, Komodo, was inhabited by the smallest numbver of species (2). Numerical classification by using the Bray Curtis dissimilarity index resulted in three groups of entities. The first group was characterized by predomination of C. kleini and the second by predomination of C. melannotus. The third one was a loose group not characterized by any predominant species. The analyses indicated that the similarities of the chaetodontid communities between locations are not related to the distance between them, but rather to habitat conditions. For example predomination of C. melannotus is strongly related to the predomination of soft coral. Compared to other areas of Indonesia, e.g. Bali, Seribu Islands, Batam, Sunda Strait, and Ambon Bay, the Flores Sea reefs have a more abundant and more diverse chaetodontid fauna.

Estimates of zooplankton abundance and size distribution with the Optical Plankton Counter (OPC)

DEFF Research Database (Denmark)

Wieland, Kai; Petersen, D.; Schnack, D.

1997-01-01

The capability of the Optical Plankton Count er (OPC) to examine the abundance and size distribution of zooplankton was tested in Storfjorden, Norway, in June 1993. Selected material obtained from net sampling was measured with a laboratory version of the OPC and compared with microscope analysis...

Probability distribution of pitting corrosion depth and rate in underground pipelines: A Monte Carlo study

International Nuclear Information System (INIS)

Caleyo, F.; Velazquez, J.C.; Valor, A.; Hallen, J.M.

2009-01-01

The probability distributions of external-corrosion pit depth and pit growth rate were investigated in underground pipelines using Monte Carlo simulations. The study combines a predictive pit growth model developed by the authors with the observed distributions of the model variables in a range of soils. Depending on the pipeline age, any of the three maximal extreme value distributions, i.e. Weibull, Frechet or Gumbel, can arise as the best fit to the pitting depth and rate data. The Frechet distribution best fits the corrosion data for long exposure periods. This can be explained by considering the long-term stabilization of the diffusion-controlled pit growth. The findings of the study provide reliability analysts with accurate information regarding the stochastic characteristics of the pitting damage in underground pipelines.

Probability distribution of pitting corrosion depth and rate in underground pipelines: A Monte Carlo study

Energy Technology Data Exchange (ETDEWEB)

Caleyo, F. [Departamento de Ingenieria Metalurgica, ESIQIE, IPN, UPALM Edif. 7, Zacatenco, 07738 Mexico, D.F. (Mexico)], E-mail: fcaleyo@gmail.com; Velazquez, J.C. [Departamento de Ingenieria Metalurgica, ESIQIE, IPN, UPALM Edif. 7, Zacatenco, 07738 Mexico, D.F. (Mexico); Valor, A. [Facultad de Fisica, Universidad de La Habana, San Lazaro y L, Vedado, 10400, La Habana (Cuba); Hallen, J.M. [Departamento de Ingenieria Metalurgica, ESIQIE, IPN, UPALM Edif. 7, Zacatenco, 07738 Mexico, D.F. (Mexico)

2009-09-15

The probability distributions of external-corrosion pit depth and pit growth rate were investigated in underground pipelines using Monte Carlo simulations. The study combines a predictive pit growth model developed by the authors with the observed distributions of the model variables in a range of soils. Depending on the pipeline age, any of the three maximal extreme value distributions, i.e. Weibull, Frechet or Gumbel, can arise as the best fit to the pitting depth and rate data. The Frechet distribution best fits the corrosion data for long exposure periods. This can be explained by considering the long-term stabilization of the diffusion-controlled pit growth. The findings of the study provide reliability analysts with accurate information regarding the stochastic characteristics of the pitting damage in underground pipelines.

Depth distribution of 2-keV helium-ion irradiation-induced cavities in nickel

International Nuclear Information System (INIS)

Fenske, G.; Das, S.K.; Kaminsky, M.

1981-01-01

Transmission electron microscopy has been used to study the effect of total dose on the depth distribution of cavities (voids or bubbles) in nickel irradiated at 500 0 C with 20-keV 4 He + ions. A transverse sectioning technique allowed us to obtain the entire depth distribution of cavities from a single specimen. The diameter, number density and volume fraction of cavities were measured as a function of depth from micrographs taken from samples sectioned parallel to the direction of the incident beam. Results for the doses at 2.9 x 10 15 and 2.9 x 10 16 ions/cm 2 show an increase in the average cavity diameter, number density and volume fraction with increasing dose. A further increase in dose from 2.9 x 10 16 to 2.9 x 10 17 ions/cm 2 also shows an increase in the average cavity diameter but a decrease in the number density. This observation is interpreted as evidence for the coalescence of cavities. 3 figures, 1 table

Feeding guild composition of a macrobenthic subtidal community along a depth gradient

Directory of Open Access Journals (Sweden)

Marina Dolbeth

2009-06-01

Full Text Available The feeding guild composition of a macrobenthic community from southern Portugal was studied along a depth gradient (1.3 to 32 m. This gradient comprised shallow areas with severe physical stress and deeper areas with no significant hydrodynamic impact at the seafloor. The main goal was to determine the influence of the spatial and temporal differences of the hydrodynamic impact at the seafloor on the feeding guild composition of the macrobenthic community. The feeding guild composition changed gradually with depth, which reflects the differences in the hydrodynamics impact at the seafloor. Herbivores and sand-lickers dominated at the shallowest depths with fine sands, which correlated with higher levels of primary production. Scavengers were also distributed in the shallow areas, which was associated with the lower predation impact. Suspension feeders, in accordance with their physiological requirements, were distributed in coarser sands subjected to a physical impact. Carnivores, surface deposit feeders and sub-surface deposit feeders were distributed mainly below 8 m depth, where there was no significant impact from the wave climate. Carnivores were associated with coarser sands and were mainly small polychaetes and nemerteans. Sub-surface and surface deposit feeders were more abundant in the deepest areas of the depth gradient with fine sands and mud deposits with higher organic content. However, surface deposit feeders also occurred at shallower depths. Some seasonal differences related to disturbance impacts were found in the numerical dominance of the feeding guilds.

Distribution and depth of bottom-simulating reflectors in the Nankai subduction margin

Science.gov (United States)

Ohde, Akihiro; Otsuka, Hironori; Kioka, Arata; Ashi, Juichiro

2018-04-01

Surface heat flow has been observed to be highly variable in the Nankai subduction margin. This study presents an investigation of local anomalies in surface heat flows on the undulating seafloor in the Nankai subduction margin. We estimate the heat flows from bottom-simulating reflectors (BSRs) marking the lower boundaries of the methane hydrate stability zone and evaluate topographic effects on heat flow via two-dimensional thermal modeling. BSRs have been used to estimate heat flows based on the known stability characteristics of methane hydrates under low-temperature and high-pressure conditions. First, we generate an extensive map of the distribution and subseafloor depths of the BSRs in the Nankai subduction margin. We confirm that BSRs exist at the toe of the accretionary prism and the trough floor of the offshore Tokai region, where BSRs had previously been thought to be absent. Second, we calculate the BSR-derived heat flow and evaluate the associated errors. We conclude that the total uncertainty of the BSR-derived heat flow should be within 25%, considering allowable ranges in the P-wave velocity, which influences the time-to-depth conversion of the BSR position in seismic images, the resultant geothermal gradient, and thermal resistance. Finally, we model a two-dimensional thermal structure by comparing the temperatures at the observed BSR depths with the calculated temperatures at the same depths. The thermal modeling reveals that most local variations in BSR depth over the undulating seafloor can be explained by topographic effects. Those areas that cannot be explained by topographic effects can be mainly attributed to advective fluid flow, regional rapid sedimentation, or erosion. Our spatial distribution of heat flow data provides indispensable basic data for numerical studies of subduction zone modeling to evaluate margin parallel age dependencies of subducting plates.[Figure not available: see fulltext.

[Composition, distribution and abundance of gastropod larvae in the South of Quintana Roo,Mexico and north of Belice].

Science.gov (United States)

Oliva Rivera, J; de Jesús Navarrete, A

2000-12-01

To know the composition, abundance and distribution of gastropod larvae, monthly samplings were carried out in the south of Quintana Roo, Mexico and north of Belize, from April to December, 1996. Collections were made in six sites at Chinchorro Bank, four in the South Coast and six at Hol-Chan, Belize, between the 10 and 20 hrs. At each station 2.5 m3 of seawater were pumped through a 202 microns mesh; 27 species were identified. The most abundant species were: South Coast, Rissoina sp. 1., Limacina sp. 1 and Natica sp. 1, Chinchorro Bank, Limacina sp. 1, Creseis acicula, Cerithiopsis hero and Rissoina sp. 1 and Hol-Chan, Limacina sp. 2, Alaba incerta and Rissoina sp. 1. The highest abundance was in rainy season. Apparently the presence of winds, coastal currents and food availability, control the distribution and abundance of larvae.

Composition, Abundance and Distribution of Brachyuran Larvae in ...

African Journals Online (AJOL)

... Ocypodidae, Grapsidae and Xanthidae. Abundance of brachyuran larvae was significantly positively correlated with total zooplankton abundance (r2 = 0.8) and salinity (r2 = 0.71). Keywords: Brachyuran larvae, abundance, composition, Mida creek, Kenya West Indian Ocean Journal of Marine Science Vol. 3 (2) 2004: pp.

Modeling the relationship between water level, wild rice abundance, and waterfowl abundance at a central North American wetland

Science.gov (United States)

Aagaard, Kevin; Eash, Josh D.; Ford, Walt; Heglund, Patricia J.; McDowell, Michelle; Thogmartin, Wayne E.

2018-01-01

Recent evidence suggests wild rice (Zizania palustris), an important resource for migrating waterfowl, is declining in parts of central North America, providing motivation to rigorously quantify the relationship between waterfowl and wild rice. A hierarchical mixed-effects model was applied to data on waterfowl abundance for 16 species, wild rice stem density, and two measures of water depth (true water depth at vegetation sampling locations and water surface elevation). Results provide evidence for an effect of true water depth (TWD) on wild rice abundance (posterior mean estimate for TWD coefficient, β TWD = 0.92, 95% confidence interval = 0.11—1.74), but not for an effect of wild rice stem density or water surface elevation on local waterfowl abundance (posterior mean values for relevant parameters overlapped 0). Refined protocols for sampling design and more consistent sampling frequency to increase data quality should be pursued to overcome issues that may have obfuscated relationships evaluated here.

Methane and nitrous oxide cycling microbial communities in soils above septic leach fields: Abundances with depth and correlations with net surface emissions.

Science.gov (United States)

Fernández-Baca, Cristina P; Truhlar, Allison M; Omar, Amir-Eldin H; Rahm, Brian G; Walter, M Todd; Richardson, Ruth E

2018-05-31

Onsite septic systems use soil microbial communities to treat wastewater, in the process creating potent greenhouse gases (GHGs): methane (CH 4 ) and nitrous oxide (N 2 O). Subsurface soil dispersal systems of septic tank overflow, known as leach fields, are an important part of wastewater treatment and have the potential to contribute significantly to GHG cycling. This study aimed to characterize soil microbial communities associated with leach field systems and quantify the abundance and distribution of microbial populations involved in CH 4 and N 2 O cycling. Functional genes were used to target populations producing and consuming GHGs, specifically methyl coenzyme M reductase (mcrA) and particulate methane monooxygenase (pmoA) for CH 4 and nitric oxide reductase (cnorB) and nitrous oxide reductase (nosZ) for N 2 O. All biomarker genes were found in all soil samples regardless of treatment (leach field, sand filter, or control) or depth (surface or subsurface). In general, biomarker genes were more abundant in surface soils than subsurface soils suggesting the majority of GHG cycling is occurring in near-surface soils. Ratios of production to consumption gene abundances showed a positive relationship with CH 4 emissions (mcrA:pmoA, p  0.05). Of the three measured soil parameters (volumetric water content (VWC), temperature, and conductivity), only VWC was significantly correlated to a biomarker gene, mcrA (p = 0.0398) but not pmoA or either of the N 2 O cycling genes (p > 0.05 for cnorB and nosZ). 16S rRNA amplicon library sequencing results revealed soil VWC, CH 4 flux and N 2 O flux together explained 64% of the microbial community diversity between samples. Sequencing of mcrA and pmoA amplicon libraries revealed treatment had little effect on diversity of CH 4 cycling organisms. Overall, these results suggest GHG cycling occurs in all soils regardless of whether or not they are associated with a leach field system. Copyright © 2018 Elsevier B

Measurement system for depth dose distribution in cancer therapy

International Nuclear Information System (INIS)

Nishizawa, Hiroshi; Fujiwara, Hirotsugu; Tsutaka, Yoshikazu; Ikeda, Ikuo

1999-01-01

An accurate estimation of an absorbed dose distribution in human tissue is indispensable to efficiently perform radiotherapy in humans. Previously, various methods for such estimation have been developed, however, there is some problem in those methods, it takes too long times (3-4 hours) to determine the absorbed dose distribution through scanning by ionization chamber in water phantom. So, a determination system of depth dose was developed with an aim to determine the absorbed dose of X-ray or electron beam in materials similar to human body. This system was composed of a detector including scintillation fibers which allows emission due to radio-interaction, CCD camera for determination of light distribution of the emission and personal computer for data processing. Though the accuracy of this system was ±2% similar to that of the conventional measuring method, measuring time was reduced to almost 5 min, markedly shorter than that of the conventional water phantom (3-4 hours). The efficacy of works including the adjustment of irradiation system, planning, etc. would be improved by application of this system. (M.N.)

Generalized additive models used to predict species abundance in the Gulf of Mexico: an ecosystem modeling tool.

Directory of Open Access Journals (Sweden)

Michael Drexler

Full Text Available Spatially explicit ecosystem models of all types require an initial allocation of biomass, often in areas where fisheries independent abundance estimates do not exist. A generalized additive modelling (GAM approach is used to describe the abundance of 40 species groups (i.e. functional groups across the Gulf of Mexico (GoM using a large fisheries independent data set (SEAMAP and climate scale oceanographic conditions. Predictor variables included in the model are chlorophyll a, sediment type, dissolved oxygen, temperature, and depth. Despite the presence of a large number of zeros in the data, a single GAM using a negative binomial distribution was suitable to make predictions of abundance for multiple functional groups. We present an example case study using pink shrimp (Farfantepenaeus duroarum and compare the results to known distributions. The model successfully predicts the known areas of high abundance in the GoM, including those areas where no data was inputted into the model fitting. Overall, the model reliably captures areas of high and low abundance for the large majority of functional groups observed in SEAMAP. The result of this method allows for the objective setting of spatial distributions for numerous functional groups across a modeling domain, even where abundance data may not exist.

In situ analysis of elemental depth distributions in thin films by combined evaluation of synchrotron x-ray fluorescence and diffraction

International Nuclear Information System (INIS)

Mainz, R.; Klenk, R.

2011-01-01

In this work we present a method for the in situ analysis of elemental depth distributions in thin films using a combined evaluation of synchrotron x-ray fluorescence and energy-dispersive x-ray diffraction signals. We recorded diffraction and fluorescence signals simultaneously during the reactive annealing of thin films. By means of the observed diffraction signals, the time evolution of phases in the thin films during the annealing processes can be determined. We utilized this phase information to parameterize the depth distributions of the elements in the films. The time-dependent fluorescence signals were then taken to determine the parameters representing the parameterized depth distributions. For this latter step, we numerically calculated the fluorescence intensities for a given set of depth distributions. These calculations handle polychromatic excitation and arbitrary functions of depth distributions and take into account primary and secondary fluorescence. Influences of lateral non-uniformities of the films, as well as the accuracy limits of the method, are investigated. We apply the introduced method to analyze the evolution of elemental depth distributions and to quantify the kinetic parameters during a synthesis process of CuInS 2 thin films via the reactive annealing of Cu-In precursors in a sulfur atmosphere.

Determinants of distribution, abundance and reproductive success ...

African Journals Online (AJOL)

... while local vegetation structure determines the abundance of locally established populations. The abundance of trees affects nest site availability and breeding success, based on observations at two oases. Blackbird nests were usually situated on pomegranate trees and olive trees. The Common Blackbird is a successful ...

Depth-variable settlement patterns and predation influence on newly settled reef fishes (Haemulon spp., Haemulidae.

Directory of Open Access Journals (Sweden)

Lance K B Jordan

Full Text Available During early demersal ontogeny, many marine fishes display complex habitat-use patterns. Grunts of the speciose genus Haemulon are among the most abundant fishes on western North Atlantic coral reefs, with most species settling to shallow habitats (≤12 m. To gain understanding into cross-shelf distributional patterns exhibited by newly settled stages of grunts (<2 cm total length, we examined: 1 depth-specific distributions of congeners at settlement among sites at 8 m, 12 m, and 21 m, and 2 depth-variable predation pressure on newly settled individuals (species pooled. Of the six species identified from collections of newly settled specimens (n = 2125, Haemulon aurolineatum (tomtate, H. flavolineatum (French grunt, and H. striatum (striped grunt comprised 98% of the total abundance; with the first two species present at all sites. Prevalence of H. aurolineatum and H. flavolineatum decreased substantially from the 8-m site to the two deeper sites. In contrast, H. striatum was absent from the 8-m site and exhibited its highest frequency at the 21-m site. Comparison of newly settled grunt delta density for all species on caged (predator exclusion and control artificial reefs at the shallowest site (8-m revealed no difference, while the 12-m and 21-m sites exhibited significantly greater delta densities on the caged treatment. This result, along with significantly higher abundances of co-occurring piscivorous fishes at the deeper sites, indicated lower predation pressure at the 8-m site. This study suggests habitat-use patterns of newly settled stages of some coral reef fishes that undergo ontogenetic shifts are a function of depth-variable predation pressure while, for at least one deeper-water species, proximity to adult habitat appears to be an important factor affecting settlement distribution.

The determination of gold depth distribution in semiconductor silicon-potential interferences inherent in NAA by radiation damages

International Nuclear Information System (INIS)

Rudolph, P.; Lange, A.; Flachowsky, J.

1986-01-01

Gold is used quite extensively to control the charge storage time of high speed diodes and transistors. Therefore, the diffusion of gold into silicon wafers of finite thickness is important in the design and fabrication of these devices. Therefore it is necessary to estimate exactly concentration and depth distribution of gold formed by gold doping. Usually, gold content and depth distribution has been estimate by neutron activation analysis with step by step etching techniques. But during the irradiation in a nuclear fuel reactor the silicon wafers undergo minute or pronounced radiation damages which may affect the depth profiles of gold concentration. (author)

Taxonomic richness and abundance of cryptic peracarid crustaceans in the Puerto Morelos Reef National Park, Mexico

Directory of Open Access Journals (Sweden)

Luz Veronica Monroy-Velázquez

2017-06-01

Full Text Available Background and Aims Cryptic peracarids are an important component of the coral reef fauna in terms of diversity and abundance, yet they have been poorly studied. The aim of this study was to evaluate the taxonomic richness and abundance of cryptic peracarids in coral rubble in the Puerto Morelos Reef National Park, Mexico (PMRNP, and their relationship with depth. Methods Three reef sites were selected: (1 Bonanza, (2 Bocana, and (3 Jardines. At each site six kilograms of coral rubble were collected over four sampling periods at three depths: 3 m (back-reef, 6–8 m (fore-reef, and 10–12 m (fore-reef. Results A total of 8,887 peracarid crustaceans belonging to 200 taxa distributed over five orders and 63 families was obtained; 70% of the taxa were identified to species and 25% to genus level. Fifty species of those collected represent new records for the Mexican Caribbean Sea. Isopoda was the most speciose order while Tanaidacea was the most abundant. Discussion Cryptic peracarid taxonomic richness and abundance were related to depth with higher values of both parameters being found in the shallow (3 m back-reef, possibly due to a higher reef development and a greater accumulation of coral rubble produced during hurricanes. Peracarid data obtained in the present study can be used as a baseline for future monitoring programs in the PMRNP.

Depth distributions of light action spectra for skin chromophores

Science.gov (United States)

Barun, V. V.; Ivanov, A. P.

2010-03-01

Light action spectra over wavelengths of 300-1000 nm are calculated for components of the human cutaneous covering: melanin, basal (bloodless) tissue, and blood oxy- and deoxyhemoglobin. The transformation of the spectra with depth in biological tissue results from two factors. The first is the wavelength dependence of the absorption coefficient corresponding to a particular skin chromophore and the second is the spectral selectivity of the radiation flux in biological tissue. This factor is related to the optical properties of all chromophores. A significant change is found to take place in the spectral distribution of absorbed radiant power with increasing depth. The action spectrum of light for the molecular oxygen contained in all components of biological tissue is also studied in the 625-645 nm range. The spectra are found to change with both the volume fraction of blood vessels and the degree of oxygenation of the blood. These results are useful for analyzing processes associated with optical absorption that are possible mechanisms for the interaction of light with biological tissues: photodissociation of oxyhemoglobin and the light-oxygen effect.

The distribution and abundance of archaeal tetraether lipids in U.S. Great Basin hot springs

Directory of Open Access Journals (Sweden)

Julienne J. eParaiso

2013-08-01

Full Text Available Isoprenoidal glycerol dialkyl glycerol tetraethers (iGDGTs are core membrane lipids of many archaea that enhance the integrity of cytoplasmic membranes in extreme environments. We examined the iGDGT profiles and corresponding aqueous geochemistry in 40 hot spring sediment and microbial mat samples from the U.S. Great Basin with temperatures ranging from 31 to 95°C and pH ranging from 6.8 to 10.7. The absolute abundance of iGDGTs correlated negatively with pH and positively with temperature. High lipid concentrations, distinct lipid profiles, and a strong relationship between polar and core lipids in hot spring samples suggested in situ production of most iGDGTs rather than contamination from local soils. Two-way cluster analysis and non-metric multidimensional scaling (NMS of polar iGDGTs indicated that the relative abundance of individual lipids was most strongly related to temperature (r2 = 0.546, with moderate correlations with pH (r2 = 0.359, nitrite (r2 = 0.286, oxygen (r2 = 0.259, and nitrate (r2 = 0.215. Relative abundance profiles of individual polar iGDGTs indicated potential temperature optima for iGDGT-0 (≤70°C, iGDGT-3 (≥55°C, and iGDGT -4 (≥60°C. These relationships likely reflect both physiological adaptations and community-level population shifts in response to temperature differences, such as a shift from cooler samples with more abundant methanogens to higher-temperature samples with more abundant Crenarchaeota. Crenarchaeol was widely distributed across the temperature gradient, which is consistent with other reports of abundant crenarchaeol in Great Basin hot springs and suggests a wide distribution for thermophilic ammonia-oxidizing archaea (AOA.

The distribution and abundance of reef-associated predatory fishes on the Great Barrier Reef

Science.gov (United States)

Emslie, Michael J.; Cheal, Alistair J.; Logan, Murray

2017-09-01

Predatory fishes are important components of coral-reef ecosystems of the Great Barrier Reef (GBR) through both the ecological functions they perform and their high value to recreational and commercial fisheries, estimated at 30 million in 2014. However, management of GBR predatory fish populations is hampered by a lack of knowledge of their distribution and abundance, aside from that of the highly targeted coral trout ( Plectropomus spp. and Variola spp.). Furthermore, there is little information on how these fishes respond to environmental stressors such as coral bleaching, outbreaks of coral-feeding starfishes ( Acanthaster planci) and storms, which limits adaptive management of their populations as the frequency or severity of such natural disturbances increases under climate change. Here, we document the distribution and abundance of 48 species of reef-associated predatory fishes and assess their vulnerability to a range of natural disturbances. There were clear differences in predatory fish assemblages across the continental shelf, but many species were widespread, with few species restricted to either inshore or offshore waters. There was weak latitudinal structure with only a few species restricted to either the northern or southern GBR. On the whole, predatory fishes were surprisingly resistant to the effects of disturbance, with few clear changes in abundance or species richness following 66 documented disturbances of varying magnitudes.

Species abundance distributions : moving beyond single prediction theories to integration within an ecological framework

NARCIS (Netherlands)

McGill, Brian J.; Etienne, Rampal S.; Gray, John S.; Alonso, David; Anderson, Marti J.; Benecha, Habtamu Kassa; Dornelas, Maria; Enquist, Brian J.; Green, Jessica L.; He, Fangliang; Hurlbert, Allen H.; Magurran, Anne E.; Marquet, Pablo A.; Maurer, Brian A.; Ostling, Annette; Soykan, Candan U.; Ugland, Karl I.; White, Ethan P.

2007-01-01

Species abundance distributions (SADs) follow one of ecology's oldest and most universal laws - every community shows a hollow curve or hyperbolic shape on a histogram with many rare species and just a few common species. Here, we review theoretical, empirical and statistical developments in the

The depth distribution of bubbles and fracture in He+ and D+ irradiated copper

International Nuclear Information System (INIS)

Johnson, P.B.; Mazey, D.J.

1982-01-01

Transmission electron microscopy is used to investigate the spatial arrangement and distribution with depth of gas bubbles produced in Cu by irradiation at 320 K to a level approx. equal to 4 x 10 21 30 keV He + m -2 . At the depth of maximum bubble size the bubbles are random and large (up to approx. equal to 10 nm across). At both shallower and greater depths the gas bubbles are smaller (approx. equal to 2 nm diam), much more uniform in size and ordered on an fcc superlattice with a lattice constant of a 1 approx. equal to 7.7 nm which (in contrast to the average bubble size) is independent of depth. It is suggested that blistering results from fracture, at a depth near the mean projected range, between large randomly-ordered bubbles which have evolved from smaller bubbles of uniform size arranged on a superlattice. For the particular case of D + irradiation of Cu at 120 K evidence is found to suggest that the fracture mechanisms involved in blistering and flaking are quite different. (orig.)

NEW RARE EARTH ELEMENT ABUNDANCE DISTRIBUTIONS FOR THE SUN AND FIVE r-PROCESS-RICH VERY METAL-POOR STARS

International Nuclear Information System (INIS)

Sneden, Christopher; Lawler, James E.; Den Hartog, Elizabeth A.; Cowan, John J.; Ivans, Inese I.

2009-01-01

We have derived new abundances of the rare earth elements Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five elements are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other elements in individual stars, to produce internally consistent Ba, rare earth, and Hf (56 ≤ Z ≤ 72) element distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.

Lionfish abundance, size structure and spatial distribution along the Venezuelan coast (Pterois volitans, Pteroinae: Scorpaenidae

Directory of Open Access Journals (Sweden)

Esteban A. Agudo

2014-09-01

Full Text Available The recent invasion of lionfish (Pterois volitans in the Atlantic is considered a new threat to benthic and fish communities in the Caribbean region. This species was first reported in Venezuela in 2009 at various sites. Increasing reports in the past five years suggest lionfish has expanded its range of distribution and habitats. Nevertheless, this information is mostly anecdotal and extensive surveys aimed to determine its abundance, size structure and other ecological aspects encompassing wider spatial scales are necessary to understand the actual role of this species on sub-tidal marine communities in Venezuela. We determined its density and population size structure through visual census along the Venezuelan coast. Visual censuses were made following strip transects at a depth between 5 and 20m and in daylight time, at 19 sites in five localities. Average density ranged between 7 to 55 individuals per hectare among sites. Most individuals were adults and most were found in caves, coexisting with other lionfish or with different species, while others were actively preying. The fish Pterois volitans seems to be well-established along the Venezuelan coast in densities that in some sites appear to be higher than in their Pacific native range but lower than in some invaded localities of the Atlantic.

Species abundance distributions: moving beyond single prediction theories to integration within an ecological framework

NARCIS (Netherlands)

McGill, B.J.; Etienne, R.S.; Gray, J.S.; Alonso, D.; Anderson, M.J.; Benecha, H.K.

2007-01-01

Species abundance distributions (SADs) follow one of ecology's oldest and most universal laws ¿ every community shows a hollow curve or hyperbolic shape on a histogram with many rare species and just a few common species. Here, we review theoretical, empirical and statistical developments in the

The abundance and distribution of uranium in some oceanic, continental ultramafic inclusions and host basalts

International Nuclear Information System (INIS)

Hamilton, E.I.

1975-01-01

The abundance and distribution of uranium in various continental and oceanic ultramafic inclusions and host basalts are reported. Uranium was determined by neutron activation (fission products, fission tracks and delayed-neutron methods) and alpha-particle autoradiography; data is also reported for the uranium content of various USGS standard rock powders. The concentration of uranium in both oceanic and continental samples is similar, levels are controlled by mineral compositions and their relative abundance in different rock types. Highest levels are found in feldspathic and lowest in olivine-rich inclusions. Uranium is enriched in mylonitised samples and along some inter-crystal boundaries. With the exception of some apatites, highest levels of uranium are in clinopyroxenes (chrome) and lowest in olivines; no enrichment of uranium in orthopyroxenes was observed. Attention is drawn to the problem of obtaining representative samples from the sea floor which have not been altered by saline solutions and the identification of uranium and daughter products present along inter-crystal boundaries. Differences in observed heat flow between continental and oceanic areas may reflect inadequate sampling of representative rock types present below the sea floor and lack of information for the true abundance and distribution of uranium in such rocks

Abundance and Distribution Patterns of Thunnus albacares in Isla del Coco National Park through Predictive Habitat Suitability Models.

Directory of Open Access Journals (Sweden)

Cristina Gonzáles-Andrés

Full Text Available Information on the distribution and habitat preferences of ecologically and commercially important species is essential for their management and protection. This is especially important as climate change, pollution, and overfishing change the structure and functioning of pelagic ecosystems. In this study, we used Bayesian hierarchical spatial-temporal models to map the Essential Fish Habitats of the Yellowfin tuna (Thunnus albacares in the waters around Isla del Coco National Park, Pacific Costa Rica, based on independent underwater observations from 1993 to 2013. We assessed if observed changes in the distribution and abundance of this species are related with habitat characteristics, fishing intensity or more extreme climatic events, including the El Niño Southern Oscillation, and changes on the average sea surface temperature. Yellowfin tuna showed a decreasing abundance trend in the sampled period, whereas higher abundances were found in shallow and warmer waters, with high concentration of chlorophyll-a, and in surrounding seamounts. In addition, El Niño Southern Oscillation events did not seem to affect Yellowfin tuna distribution and abundance. Understanding the habitat preferences of this species, using approaches as the one developed here, may help design integrated programs for more efficient management of vulnerable species.

Effects of depth and crayfish size on predation risk and foraging profitability of a lotic crayfish

Science.gov (United States)

Flinders, C.A.; Magoulick, D.D.

2007-01-01

We conducted field surveys and experiments to determine whether observed distributions of crayfish among habitats were influenced by differential resource availability, foraging profitability, and predation rates and whether these factors differed with crayfish size and habitat depth. We sampled available food resources (detritus and invertebrates) and shelter as rock substrate in deep (>50 cm) and shallow (<30 cm) habitats. We used an enclosure-exclosure experiment to examine the effects of water depth and crayfish size on crayfish biomass and survival, and to determine whether these factors affected silt accrual, algal abundance (chlorophyll a [chl a]), and detritus and invertebrate biomass (g ash-free dry mass) differently from enclosures without crayfish. We conducted tethering experiments to assess predation on small (13-17 mm carapace length [CL]) and large (23-30 mm CL) Orconectes marchandi and to determine whether predation rates differed with water depth. Invertebrate biomass was significantly greater in shallow water than in deep water, whereas detritus biomass did not differ significantly between depths. Cobble was significantly more abundant in shallow than in deep water. Depth and crayfish size had a significant interactive effect on change in size of enclosed crayfish when CL was used as a measure of size but not when biomass was used as a measure of size. CL of small crayfish increased significantly more in enclosures in shallow than in deep water, but CL of large crayfish changed very little at either depth. Silt, chl a, and detritus biomass were significantly lower on tiles in large- than in small- and no-crayfish enclosures, and invertebrate biomass was significantly lower in large- than in no-crayfish enclosures. Significantly more crayfish were consumed in deep than in shallow water regardless of crayfish size. Our results suggest that predation and resource availability might influence the depth distribution of small and large crayfish. Small

Rapid change with depth in megabenthic structure-forming communities of the Makapu'u deep-sea coral bed

Science.gov (United States)

Long, Dustin J.; Baco, Amy R.

2014-01-01

Seamounts are largely unexplored undersea mountains rising abruptly from the ocean floor, which can support an increased abundance and diversity of organisms. Deep-sea corals are important benthic structure-formers on current-swept hard substrates in these habitats. While depth is emerging as a factor structuring the fauna of seamounts on a large spatial scale, most work addressing deep-sea coral and seamount community structure has not considered the role of small-scale variation in species distributions. Video from six ROV dives over a depth range of ~320-530 m were analyzed to assess the diversity and density of benthic megafaunal invertebrates across the Makapu'u deep-sea coral bed, offshore of Oahu, Hawaii. At the same time, the physical environment along the dive track was surveyed to relate biotic patterns with abiotic variables including depth, aspect, rugosity, substrate, slope and relief to test the factors structuring community assemblages. Despite the narrow range examined, depth was found to be the strongest structuring gradient, and six unique macrobenthic communities were found, with a 93% faunal dissimilarity over the depth surveyed. Relief, rugosity and slope were also factors in the final model. Alcyonacean octocorals were the dominant macrofaunal invertebrates at all but the deepest depth zone. The commercially harvested precious coral C. secundum was the dominant species at depths 370-470 m, with a distribution that is on average deeper than similar areas. This may be artificial due to the past harvesting of this species on the shallower portion of its range. Primnoid octocorals were the most abundant octocoral family overall. This work yields new insight on the spatial ecology of seamounts, pointing out that community changes can occur over narrow depth ranges and that communities can be structured by small-scale physiography.

Distribution of microbial populations and their relationship with environmental variables in the North Yellow Sea, China

Science.gov (United States)

Bai, Xiaoge; Wang, Min; Liang, Yantao; Zhang, Zhifeng; Wang, Fang; Jiang, Xuejiao

2012-03-01

In order to understand the large-scale spatial distribution characteristics of picoplankton, nanophytoplankton and virioplankton and their relationship with environmental variables in coastal and offshore waters, flow cytometry (FCM) was used to analyze microbial abundance of samples collected in summer from four depths at 36 stations in the North Yellow Sea (NYS). The data revealed spatial heterogeneity in microbial populations in the offshore and near-shore waters of the NYS during the summer. For the surface layer, picoeukaryotes were abundant in the near-shore waters, Synechococcus was abundant in the offshore areas, and bacterial and viral abundances were high in the near-shore waters around the Liaodong peninsula. In the near-shore waters, no significant vertical variation of picophytoplankton (0.2-2μm) abundance was found. However, the nanophytoplankton abundance was higher in the upper layers (from the surface to 10 m depth) than in the bottom layer. For the offshore waters, both pico- and nanophytoplankton (2-20μm) abundance decreased sharply with depth in the North Yellow Sea Cold Water Mass (NYSCWM). But, for the vertical distribution of virus and bacteria abundance, no significant variation was observed in both near-shore and offshore waters. Autotrophic microbes were more sensitive to environmental change than heterotrophic microbes and viruses. Viruses showed a positive correlation with bacterial abundance, suggesting that the bacteriophage might be prominent for virioplankton (about 0.45μm) in summer in the NYS and that viral abundance might play an important role in microbial loop functions.

Species composition and bathymetric distribution of gorgonians (Anthozoa: Octocorallia on the Southern Mexican Pacific coast

Directory of Open Access Journals (Sweden)

Rosalinda Abeytia

2013-09-01

Full Text Available Gorgonians are important components of coastal ecosystems, as they provide niches, natural compounds with medical applications and are used as bioindicators. Species composition and assemblage structure of gorgonians (Anthozoa: Octocorallia were studied along a bathymetric profile in the Southern Mexican Pacific coast. Species composition was based on specimens collected within a depth range of 0-70m in 15 sites. The relative abundance of species was determined in six sites at four depths (5, 10, 20 and 25m using three 10m2 transects at each depth level. Twenty-seven species of gorgonians belonging to six genera and three families were registered. The species composition varied with depth: 11 species were distributed between 0-25m depth, while 17 species were found between 40-70m depth interval. The shallow zone is characterized by a relatively large abundance of gorgonians, dominated by colonies of Leptogorgia cuspidata and L. ena. In contrast, the deepest zone was characterized by relatively low abundance of gorgonians, dominated by L. alba, the only species observed in both depth intervals. The similarity analysis showed differences in the composition and abundance of species by depth and site, suggesting that the main factor in determining the assemblage structure is depth. Results of this study suggest that the highest richness of gorgonian species in the study area may be located at depths of 40-70m, whereas the highest abundances are found between 5 and 10m depth. This study represents a contribution to the poorly known eastern Pacific gorgonian biota.

Calculated depth-dose distributions for H+ and He+ beams in liquid water

International Nuclear Information System (INIS)

Garcia-Molina, Rafael; Abril, Isabel; Denton, Cristian D.; Heredia-Avalos, Santiago; Kyriakou, Ioanna; Emfietzoglou, Dimitris

2009-01-01

We have calculated the dose distribution delivered by proton and helium beams in liquid water as a function of the target-depth, for incident energies in the range 0.5-10 MeV/u. The motion of the projectiles through the stopping medium is simulated by a code that combines Monte Carlo and a finite differences algorithm to consider the electronic stopping power, evaluated in the dielectric framework, and the multiple nuclear scattering with the target nuclei. Changes in projectile charge-state are taken into account dynamically as it moves through the target. We use the MELF-GOS model to describe the energy loss function of liquid water, obtaining a value of 79.4 eV for its mean excitation energy. Our calculated stopping powers and depth-dose distributions are compared with those obtained using other methods to describe the energy loss function of liquid water, such as the extended Drude and the Penn models, as well as with the prediction of the SRIM code and the tables of ICRU.

Distribution, abundance and ecological relevance of pelagic fishes in the Lazarev Sea, Southern Ocean

NARCIS (Netherlands)

Flores, Hauke; de Putte, Anton P. Van; Siegel, Volker; Pakhomov, Evgeny A.; Van Franeker, Jan A.; Meesters, Hugo W. G.; Volckaert, Filip A. M.

2008-01-01

The distribution and abundance of larval and postlarval fishes was investigated in the Lazarev Sea, Southern Ocean, in March and April 2004. The upper 200 m of the water column were sampled with an 8 m(2) rectangular midwater trawl at 93 stations. The larval species community clustered in a diverse

Distribution, abundance and ecological relevance of pelagic fishes in the Lazarev Sea, Southern Ocean

NARCIS (Netherlands)

Florentino De Souza Silva, A.P.; Putte, van de A.P.; Siegel, V.; Pakhomov, E.A.; Franeker, van J.A.; Meesters, H.W.G.; Colckaert, F.A.M.

2008-01-01

The distribution and abundance of larval and postlarval fishes was investigated in the Lazarev Sea, Southern Ocean, in March and April 2004. The upper 200 m of the water column were sampled with an 8 m2 rectangular midwater trawl at 93 stations. The larval species community clustered in a diverse

Phantom experiment of depth-dose distributions for gadolinium neutron capture therapy

International Nuclear Information System (INIS)

Matsumoto, T.; Kato, K.; Sakuma, Y.; Tsuruno, A.; Matsubayashi, M.

1993-01-01

Depth-dose distributions in a tumor simulated phantom were measured for thermal neutron flux, capture gamma-ray and internal conversion electron dose rates for gadolinium neutron capture therapy. The results show that (i) a significant dose enhancement can be achieved in the tumor by capture gamma-rays and internal conversion electrons but the dose is mainly due to capture gamma-rays from the Gd(n, γ) reactions, therefore, is not selective at the cellular level, (ii) the dose distribution was a function of strongly interrelated parameters such as gadolinium concentrations, tumor site and neutron beam size (collimator aperture size), and (iii) the Gd-NCT by thermal neutrons appears to be a potential for treatment of superficial tumor. (author)

Depth gradients in food-web processes linking habitats in large lakes: Lake Superior as an exemplar ecosystem

Science.gov (United States)

Sierszen, Michael E.; Hrabik, Thomas R.; Stockwell, Jason D.; Cotter, Anne M; Hoffman, Joel C.; Yule, Daniel L.

2014-01-01

In large lakes around the world, depth-based changes in the abundance and distribution of invertebrate and fish species suggest that there may be concomitant changes in patterns of resource allocation. Using Lake Superior of the Laurentian Great Lakes as an example, we explored this idea through stable isotope analyses of 13 major fish taxa.

Montane-breeding bird distribution and abundance across national parks of southwestern Alaska

Science.gov (United States)

Amundson, Courtney L.; Handel, Colleen M.; Ruthrauff, Daniel R.; Tibbitts, T. Lee; Gill, Robert E.

2018-01-01

relative abundance and models of abundance and species richness relative to land cover that can be used to assess future changes in avian distribution. Additionally, these subarctic montane parks may serve as signals of landscape change and barometers for the assessment of population and distributional changes as a result of warming temperatures and changing precipitation patterns.

Abundance, distribution and population trends of Nile crocodile (Crocodylus niloticus) in Gonarezhou National Park, Zimbabwe

NARCIS (Netherlands)

Zisadza-Gandiwa, P.; Gandiwa, E.; Jakarasi, J.; Westhuizen, van der H.; Muvengwi, J.

2013-01-01

The Nile crocodile (Crocodylus niloticus) is an iconic or keystone species in many aquatic ecosystems. In order to understand the abundance, distribution, and population trends of Nile crocodiles in Gonarezhou National Park (GNP), southeastern Zimbabwe, we carried out 4 annual aerial surveys, using

Abundance and distribution of feral pigs at Hakalau Forest National Wildlife Refuge, 2010-2013

Science.gov (United States)

Hess, Steven C.; Leopold, Christina R.; Kendall, Steven J.

2013-01-01

The Hakalau Forest Unit of the Big Island National Wildlife Refuge Complex has intensively managed feral pigs (Sus scrofa) and monitored feral pig presence with surveys of all managed areas since 1988. Results of all available data regarding pig management activities through 2004 were compiled and analyzed, but no further analyses had been conducted since then. The objective of this report was to analyze recent feral ungulate surveys at the Hakalau Forest Unit to determine current pig abundance and distribution. Activity indices for feral pigs, consisting of the presence of fresh or intermediate sign at 422 stations, each with approximately 20 sample plots, were compiled for years 2010–2013. A calibrated model based on the number of pigs removed from one management unit and concurrent activity surveys was applied to estimate pig abundance in other management units. Although point estimates appeared to decrease from 489.1 (±105.6) in 2010 to 407.6 (±88.0) in 2013, 95% confidence intervals overlapped, indicating no significant change in pig abundance within all management units. Nonetheless, there were significant declines in pig abundance over the four-year period within management units 1, 6, and 7. Areas where pig abundance remained high include the southern portion of Unit 2. Results of these surveys will be useful for directing management actions towards specific management units.

Macrobenthos composition, distribution and abundance within Sungai Pulai estuary, Johor, Malaysia

Science.gov (United States)

Shi, Guan Wan; Min, Lee Di; Ghaffar, Mazlan Abd; Ali, Masni Md; Cob, Zaidi Che

2014-09-01

Macrobenthos are very useful organisms for monitoring marine environmental and widely use in marine ecology research. They are able to monitor the difference phase in the recovery stage of disturbed sites by appear different species macrobenthos after the cessation of the impact. Univariate and multivariate methods were use to study the macrobenthos community within Sungai Pulai estuary, Johor, Malaysia. Five sub-samples were taken at each sampling sites by using 10 cm diameter corer. Crustaceans were the most abundant at Tanjung Adang (St. 1) and the station of non-seagrass area (St. 2) while polychaetes were the most abundant at Merambong Shoal (St. 3). Higher density of macrobenthos was found at St.3 followed by St. 1 and St. 2. The commonly used population indices such as diversity, richness, evenness and dominance were employed to determine the differences in diversity and abundance of macrobenthos. The diversity, richness and evenness index values showed slight increment from Station 1 to Station 3, while the dominance index decreasing trend from Station 1 to Station 3. A total 21 polychaete families were collected in Sungai Pulai estuary, which was dominated by the Spionidae, Capitellidae and Glyceridae. Cluster (Bray-Curtis similarities) analyses revealed that the Tanjung Adang and Merambong Shoal population were clearly separated from the station non-seagrass. For the time being factors that influence the pattern of distribution of the macrobenthos cannot be determined and subjected to further studies.

[Effects of submarine topography and water depth on distribution of pelagic fish community in minnan-taiwan bank fishing ground].

Science.gov (United States)

Fang, Shuimei; Yang, Shengyun; Zhang, Chengmao; Zhu, Jinfu

2002-11-01

According to the fishing record of the light-seine information vessel in Minnan-Taiwan bank ground during 1989 to 1999, the effects of submarine topography and water depth on distribution of pelagic fish community in Minnan-Taiwan bank fishing ground was studied. The results showed that the pelagic fish distributed concentratively, while the submarine topography and water depth varied widely, but in different fishing regions, the distribution of pelagic fishes was uneven. The distribution of fishing yield increased from north to south, and closed up from sides of the bank to south or north in the regions. Pelagic fish distributed mainly in mixed water in the southern Taiwan Strait, and in warm water in the Taiwan Strait. The central fishing grounds were at high salt regions. Close gathering regions of pelagic fish or central fishing ground would be varied with the seasonal variation of mixed water in the southern Taiwan Strait and warm water in the Taiwan Strait. Central fishing ground was not only related to submarine topography and water depth, but also related to wind direction, wind-power and various water systems. In the fishing ground, the gathering depth of pelagic fish was 30-60 m in spring and summer, and 40-80 m in autumn and winter.

NEW STRONG-LINE ABUNDANCE DIAGNOSTICS FOR H II REGIONS: EFFECTS OF κ-DISTRIBUTED ELECTRON ENERGIES AND NEW ATOMIC DATA

Energy Technology Data Exchange (ETDEWEB)

Dopita, Michael A.; Sutherland, Ralph S.; Nicholls, David C.; Kewley, Lisa J.; Vogt, Frédéric P. A., E-mail: Michael.Dopita@anu.edu.au [Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd., Weston ACT 2611 (Australia)

2013-09-01

Recently, Nicholls et al., inspired by in situ observations of solar system astrophysical plasmas, suggested that the electrons in H II regions are characterized by a κ-distribution of energies rather than a simple Maxwell-Boltzmann distribution. Here, we have collected together new atomic data within a modified photoionization code to explore the effects of both the new atomic data and the κ-distribution on the strong-line techniques used to determine chemical abundances in H II regions. By comparing the recombination temperatures (T {sub rec}) with the forbidden line temperatures (T {sub FL}), we conclude that κ ∼ 20. While representing only a mild deviation from equilibrium, this result is sufficient to strongly influence abundances determined using methods that depend on measurements of the electron temperature from forbidden lines. We present a number of new emission line ratio diagnostics that cleanly separate the two parameters determining the optical spectrum of H II regions—the ionization parameter q or U and the chemical abundance, 12+log(O/H). An automated code to extract these parameters is presented. Using the homogeneous data set from van Zee et al., we find self-consistent results between all of these different diagnostics. The systematic errors between different line ratio diagnostics are much smaller than those found in the earlier strong-line work. Overall, the effect of the κ-distribution on the strong-line abundances derived solely on the basis of theoretical models is rather small.

Analyzing fractal property of species abundance distribution and diversity indexes.

Science.gov (United States)

Su, Qiang

2016-03-07

Community diversity is usually characterized by numerical indexes; however it indeed depends on the species abundance distribution (SAD). Diversity indexes and SAD are based on the same information but treating as separate themes. Ranking species abundance from largest to smallest, the decreasing pattern can give the information about the SAD. Frontier proposed such SAD might be a fractal structure, and first applied the Zipf-Mandelbrot model to the SAD study. However, this model fails to include the Zipf model, and also fails to ensure an integer rank. In this study, a fractal model of SAD was reconstructed, and tested with 104 community samples from 8 taxonomic groups. The results show that there was a good fit of the presented model. Fractal parameter (p) determines the SAD of a community. The ecological significance of p relates to the "dominance" of a community. The correlation between p and classical diversity indexes show that Shannon index decreases and Simpson index increases as p increases. The main purpose of this paper is not to compare with other SADs models; it simply provides a new interpretation of SAD model construction, and preliminarily integrates diversity indexes and SAD model into a broader perspective of community diversity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Simulation of depth distribution of geological strata. HQSW program

International Nuclear Information System (INIS)

Czubek, J.A.; Kolakowski, L.

1987-01-01

The method of simulation of the layered geological formation for a given geological parameter is presented. The geological formation contains at least two types of layers and is given with the depth resolution Δh corresponding to the thickness of the hypothetical elementary layer. Two types of geostatistical distributions of the rock parameters are considered: modified normal and modified lognormal for which the input data are expected value and the variance. The HQSW simulation program given in the paper generates in a random way (but in a given repeatable sequence) the thicknesses of a given type of strata, their average specific radioactivity and the variance of specific radioactivity within a given layer. 8 refs., 14 figs., 1 tab. (author)

Bathymetric and longitudinal distribution analyysis of the rockfish Helicolenus Dactylopterus (Delaroche, 1809 in the southern Tyrrhenian Sea (central Mediterranean

Directory of Open Access Journals (Sweden)

T. ROMEO

2009-06-01

Full Text Available This study provides information on bathymetric and longitudinal distribution heterogeneity of the rockfish Helicolenus dactylopterus in the southern Tyrrhenian Sea. Data were drawn from experimental bottom trawl (1996-2002 plus bottom trap (2001-02 surveys. The frequency of occurrence and mean relative density (N/km2 and biomass (kg/km2 indexes were calculated for two survey seasons (spring and autumn, four geographic sectors and three depth strata. MANOVA was used to test fish abundance among years, sectors and strata. Analysis of the length-frequency distributions was carried out by two-way (gears and depths ANOVA, post hoc multiple comparisons for testing differences among depths and Student’s t test for testing differences between gears. Length-weight relationship was also estimated and the allometric coefficient was tested with the Student’s t test. The results showed a significant positive bathymetric gradient of sizes both for trawl and trap surveys; at same depths, fish caught by traps were significantly longer than those caught by trawl. In spring surveys, significant differences were found among strata for both abundance indexes; in autumn surveys, significant differences between depth strata were found only for density indices. The distribution and abundance patterns of H. dactylopterus along the southern Tyrrhenian Sea was homogeneous among sectors. Length-weight relationship showed a significant positive allometric growth.

A hierarchical model for estimating the spatial distribution and abundance of animals detected by continuous-time recorders.

Directory of Open Access Journals (Sweden)

Robert M Dorazio

Full Text Available Several spatial capture-recapture (SCR models have been developed to estimate animal abundance by analyzing the detections of individuals in a spatial array of traps. Most of these models do not use the actual dates and times of detection, even though this information is readily available when using continuous-time recorders, such as microphones or motion-activated cameras. Instead most SCR models either partition the period of trap operation into a set of subjectively chosen discrete intervals and ignore multiple detections of the same individual within each interval, or they simply use the frequency of detections during the period of trap operation and ignore the observed times of detection. Both practices make inefficient use of potentially important information in the data.We developed a hierarchical SCR model to estimate the spatial distribution and abundance of animals detected with continuous-time recorders. Our model includes two kinds of point processes: a spatial process to specify the distribution of latent activity centers of individuals within the region of sampling and a temporal process to specify temporal patterns in the detections of individuals. We illustrated this SCR model by analyzing spatial and temporal patterns evident in the camera-trap detections of tigers living in and around the Nagarahole Tiger Reserve in India. We also conducted a simulation study to examine the performance of our model when analyzing data sets of greater complexity than the tiger data.Our approach provides three important benefits: First, it exploits all of the information in SCR data obtained using continuous-time recorders. Second, it is sufficiently versatile to allow the effects of both space use and behavior of animals to be specified as functions of covariates that vary over space and time. Third, it allows both the spatial distribution and abundance of individuals to be estimated, effectively providing a species distribution model, even in

Measuring impact crater depth throughout the solar system

Science.gov (United States)

Robbins, Stuart J.; Watters, Wesley A.; Chappelow, John E.; Bray, Veronica J.; Daubar, Ingrid J.; Craddock, Robert A.; Beyer, Ross A.; Landis, Margaret E.; Ostrach, Lillian; Tornabene, Livio L.; Riggs, Jamie D.; Weaver, Brian P.

2018-01-01

One important, almost ubiquitous, tool for understanding the surfaces of solid bodies throughout the solar system is the study of impact craters. While measuring a distribution of crater diameters and locations is an important tool for a wide variety of studies, so too is measuring a crater's “depth.” Depth can inform numerous studies including the strength of a surface and modification rates in the local environment. There is, however, no standard data set, definition, or technique to perform this data‐gathering task, and the abundance of different definitions of “depth” and methods for estimating that quantity can lead to misunderstandings in and of the literature. In this review, we describe a wide variety of data sets and methods to analyze those data sets that have been, are currently, or could be used to derive different types of crater depth measurements. We also recommend certain nomenclature in doing so to help standardize practice in the field. We present a review section of all crater depths that have been published on different solar system bodies which shows how the field has evolved through time and how some common assumptions might not be wholly accurate. We conclude with several recommendations for researchers which could help different data sets to be more easily understood and compared.

Distribution and life strategies of two bacterial populations in a eutrophic lake

Science.gov (United States)

Weinbauer; Hofle

1998-10-01

Monoclonal antibodies and epifluorescence microscopy were used to determine the depth distribution of two indigenous bacterial populations in the stratified Lake Plusssee and characterize their life strategies. Populations of Comamonas acidovorans PX54 showed a depth distribution with maximum abundances in the oxic epilimnion, whereas Aeromonas hydrophila PU7718 showed a depth distribution with maximum abundances in the anoxic thermocline layer (metalimnion), i. e., in the water layer with the highest microbial activity. Resistance of PX54 to protist grazing and high metabolic versatility and growth rate of PU7718 were the most important life strategy traits for explaining the depth distribution of the two bacterial populations. Maximum abundance of PX54 was 16,000 cells per ml, and maximum abundance of PU7718 was 20,000 cells per ml. Determination of bacterial productivity in dilution cultures with different-size fractions of dissolved organic matter (DOM) from lake water indicates that low-molecular-weight (LMW) DOM is less bioreactive than total DOM (TDOM). The abundance and growth rate of PU7718 were highest in the TDOM fractions, whereas those of PX54 were highest in the LMW DOM fraction, demonstrating that PX54 can grow well on the less bioreactive DOM fraction. We estimated that 13 to 24% of the entire bacterial community and 14% of PU7718 were removed by viral lysis, whereas no significant effect of viral lysis on PX54 could be detected. Growth rates of PX54 (0.11 to 0.13 h-1) were higher than those of the entire bacterial community (0.04 to 0.08 h-1) but lower than those of PU7718 (0.26 to 0.31 h-1). In undiluted cultures, the growth rates were significantly lower, pointing to density effects such as resource limitation or antibiosis, and the effects were stronger for PU7718 and the entire bacterial community than for PX54. Life strategy characterizations based on data from literature and this study revealed that the fast-growing and metabolically

Alone in the dark: Distribution, population structure and reproductive mode of the dominant isopod Eurycope spinifrons Gurjanova, 1933 (Isopoda: Asellota: Munnopsidae) from bathyal and abyssal depths of the Sea of Japan

Science.gov (United States)

Elsner, Nikolaus O.; Golovan, Olga A.; Malyutina, Marina V.; Brandt, Angelika

2013-02-01

Due to isolation and a period of severe anoxic conditions in geologically recent times, biodiversity is low in the deep Sea of Japan. Among a small group of species inhabiting depths below 2500, only one isopod species, Eurycope spinifrons, was found during the SoJaBio expedition in 2010, but it was the most abundant species of all benthic taxa. E. spinifrons was found with remarkably high numbers of individuals at the sampled stations below 2500 m, providing a rare opportunity to investigate aspects of population structure and reproduction of a deep-sea isopod. The distribution, population structure, fecundity and depth dependent density of E. spinifrons were studied. Brooding females were the longest in body size and least abundant, while mancae were the shortest and most abundant. The mean length of individuals showed little deviation among the stations below 2500 m, ranging from 4.21±0.29 mm in brooding females to 1.20±0.26 mm in free-living mancae. Iteroparity is demonstrated for E. spinifrons. It is argued that females have continuous reproduction which increases in the summer. The length of the brooding females is positively correlated with the number of eggs in the marsupium in our sample (r=0.291; p<0.05). Comparing the mean length of E. spinifrons between different stations revealed that specimens sampled at the upper slope (460 m) were significantly smaller in every developmental stage than those from stations below 2500 m. This finding confirms the existence of a threshold depth below which E. spinifrons was the only isopod species found. Thus, we argue that individuals at deeper stations grow bigger due to reduced competition in the deep Sea of Japan.

Fire, grazing history, lichen abundance, and winter distribution of caribou in Alaska's taiga

Science.gov (United States)

Collins, William B.; Dale, Bruce W.; Adams, Layne G.; McElwain, Darien E.; Joly, Kyle

2011-01-01

In the early 1990s the Nelchina Caribou (Rangifer tarandus) Herd (NCH) began a dramatic shift to its current winter range, migrating at least an additional 100 km beyond its historic range. We evaluated the impacts of fire and grazing history on lichen abundance and subsequent use and distribution by the NCH. Historic (prior to 1990) and current (2002) winter ranges of the NCH had similar vascular vegetation, lichen cover (P = 0.491), and fire histories (P = 0.535), but the former range had significantly less forage lichen biomass as a result of grazing by caribou. Biomass of forage lichens was twice as great overall (P = 0.031) and 4 times greater in caribou selected sites on the current range than in the historic range, greatly increasing availability to caribou. Caribou on the current range selected for stands with >20% lichen cover (P lichen biomass and stands older than 80 yr postfire (P lichen cover and biomass seldom recovered sufficiently to attract caribou grazing until after ≥60 yr, and, as a group, primary forage lichen species did not reach maximum abundance until 180 yr postfire. Recovery following overgrazing can occur much more quickly because lichen cover, albeit mostly fragments, and organic substrates remain present. Our results provide benchmarks for wildlife managers assessing condition of caribou winter range and predicting effects of fires on lichen abundance and caribou distribution. Of our measurements of cover and biomass by species, densities and heights of trees, elevation, slope and aspect, only percentage cover by Cladonia amaurocraea, Cladina rangiferina, Flavocetraria cuculata, and lowbush cranberry (Vaccinium vitis‐idaea) were necessary for predicting caribou use of winter range.

Projecting the impacts of climate change on skipjack tuna abundance and spatial distribution.

Science.gov (United States)

Dueri, Sibylle; Bopp, Laurent; Maury, Olivier

2014-03-01

Climate-induced changes in the physical, chemical, and biological environment are expected to increasingly stress marine ecosystems, with important consequences for fisheries exploitation. Here, we use the APECOSM-E numerical model (Apex Predator ECOSystem Model - Estimation) to evaluate the future impacts of climate change on the physiology, spatial distribution, and abundance of skipjack tuna, the worldwide most fished species of tropical tuna. The main novelties of our approach lie in the mechanistic link between environmental factors, metabolic rates, and behavioral responses and in the fully three dimensional representation of habitat and population abundance. Physical and biogeochemical fields used to force the model are provided by the last generation of the IPSL-CM5 Earth System Model run from 1990 to 2100 under a 'business-as-usual' scenario (RCP8.5). Our simulations show significant changes in the spatial distribution of skipjack tuna suitable habitat, as well as in their population abundance. The model projects deterioration of skipjack habitat in most tropical waters and an improvement of habitat at higher latitudes. The primary driver of habitat changes is ocean warming, followed by food density changes. Our projections show an increase of global skipjack biomass between 2010 and 2050 followed by a marked decrease between 2050 and 2095. Spawning rates are consistent with population trends, showing that spawning depends primarily on the adult biomass. On the other hand, growth rates display very smooth temporal changes, suggesting that the ability of skipjack to keep high metabolic rates in the changing environment is generally effective. Uncertainties related to our model spatial resolution, to the lack or simplification of key processes and to the climate forcings are discussed. © 2013 John Wiley & Sons Ltd.

A short review of the distribution of short-beaked common dolphins (Delphinus delphis in the central and eastern North Atlantic with an abundance estimate for part of this area

Directory of Open Access Journals (Sweden)

Ana Cañadas

2009-09-01

Full Text Available This paper uses data from 3 programmes: (1 the North Atlantic Sightings Surveys (NASS surveys undertaken throughout much of the central and eastern North Atlantic north of about 40° N in 1987, 1989, 1995 and 2001; (2 the MICA-93 programme; and (3 the north eastern Atlantic segment of the Small Cetacean Abundance in the North Sea (SCANS survey in 1994. The data from all surveys were used to examine the distribution of common dolphins in the NE Atlantic. No sightings were made north of 57° N. An initial attempt to examine distribution against 4 potential non biological explanatory variables was made. A simple interpretation of the preliminary analyses presented here is that the primary areas for groups of common dolphins were in waters over 15° C and depths of 400-1,000 m (there does appear a link with shelf features, between around 49°-55° N especially between 20°-30°W. An illustrative example of spatial modelling is presented. Only for 1 year (and part of the total survey area were there sufficient data to attempt to estimate abundance: 1995. The estimated abundance in the W Block of the NASS-95 Faroese survey was 273,159 (cv=0.26; 95% CI=153,392-435,104 short-beaked common dolphins. This estimate is corrected for animals missed on the trackline (g(0 and for responsive movement.

Abundance and distribution of sylvatic dengue virus vectors in three different land cover types in Sarawak, Malaysian Borneo.

Science.gov (United States)

Young, Katherine I; Mundis, Stephanie; Widen, Steven G; Wood, Thomas G; Tesh, Robert B; Cardosa, Jane; Vasilakis, Nikos; Perera, David; Hanley, Kathryn A

2017-08-31

Mosquito-borne dengue virus (DENV) is maintained in a sylvatic, enzootic cycle of transmission between canopy-dwelling non-human primates and Aedes mosquitoes in Borneo. Sylvatic DENV can spill over into humans living in proximity to forest foci of transmission, in some cases resulting in severe dengue disease. The most likely vectors of such spillover (bridge vectors) in Borneo are Ae. albopictus and Ae. niveus. Borneo is currently experiencing extensive forest clearance. To gauge the effect of this change in forest cover on the likelihood of sylvatic DENV spillover, it is first necessary to characterize the distribution of bridge vectors in different land cover types. In the current study, we hypothesized that Ae. niveus and Ae. albopictus would show significantly different distributions in different land cover types; specifically, we predicted that Ae. niveus would be most abundant in forests whereas Ae. albopictus would have a more even distribution in the landscape. Mosquitoes were collected from a total of 15 sites using gravid traps and a backpack aspirator around Kampong Puruh Karu, Sarawak, Malaysian Borneo, where sylvatic DENV spillover has been documented. A total of 2447 mosquitoes comprising 10 genera and 4 species of Aedes, were collected over the three years, 2013, 2014 and 2016, in the three major land cover types in the area, homestead, agriculture and forest. Mosquitoes were identified morphologically, pooled by species and gender, homogenized, and subject to DNA barcoding of each Aedes species and to arbovirus screening. As predicted, Ae. niveus was found almost exclusively in forests whereas Ae. albopictus was collected in all land cover types. Aedes albopictus was significantly (P = 0.04) more abundant in agricultural fields than forests. Sylvatic DENV was not detected in any Aedes mosquito pools, however genomes of 14 viruses were detected using next generation sequencing. Land cover type affects the abundance and distribution of the most

Ichthyoplankton distribution and abundance off southeastern and southern Brazil

Directory of Open Access Journals (Sweden)

Débora Martins de Freitas

2004-08-01

Full Text Available This study describes the distribution of fish eggs and larvae along the southeastern and southern Brazilian coast. Plankton samples were collected at 85 stations using a Bongo net, and water salinity and temperature were profiled with a CTD. Results showed that fish eggs and larvae, and zooplankton biovolume were distributed in coastal waters with mean temperature of 23ºC and salinity between 33 and 34. The largest egg abundance occurred along Iguape (24º'S with a partial overlap with zooplankton biovolume and fish larvae were most abundant near shore close to Santos (24ºS. These protected coastal waters presented a surface layer with lower salinity and higher temperatures, while the bottom layer had cooler water. Ichthyoplankton abundance was low off Cabo Frio (22º'S, while a maximum in fish eggs occurred around Cabo Santa Marta Grande (28ºS.A abundância de ovos e larvas de peixes serve como um indicador do tamanho do estoque desovante, e a variabilidade nestes parâmetros está associada a flutuações no recrutamento de recursos pesqueiros. No sul e sudeste do Brasil a distribuição do ictioplâncton é influenciada pela dinâmica da Confluência Subtropical, pelo aporte de água doce e pela ação do vento na camada superficial do oceano. Este trabalho tem como objetivo descrever a distribuição de ovos e larvas de peixes ao longo da área compreendida entre Cabo Frio (22º'S e o Cabo de Santa Marta Grande (28ºS, entre 15/11 e 05/12/95. Em 85 estações foram coletadas amostras de plâncton com uma rede Bongo de 60cm de diâmetro e 330m m de malha, dotada de fluxômetro e arrastada obliquamente. Salinidade e temperatura foram obtidas em cada estação com um CTD. O maior número de ovos e larvas de peixes e biovolume de zooplâncton foram encontrados em áreas distintas na região costeira, em temperaturas entre 23 e 24ºC e salinidades entre 33 e 34. As larvas foram mais abundantes na costa de Santos; os

IMPROVING INTERFEROMETRIC NULL DEPTH MEASUREMENTS USING STATISTICAL DISTRIBUTIONS: THEORY AND FIRST RESULTS WITH THE PALOMAR FIBER NULLER

International Nuclear Information System (INIS)

Hanot, C.; Riaud, P.; Absil, O.; Mennesson, B.; Martin, S.; Liewer, K.; Loya, F.; Mawet, D.; Serabyn, E.

2011-01-01

A new 'self-calibrated' statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and beam intensities to retrieve the astrophysical null depth (or equivalently the object's visibility) in the presence of fast atmospheric fluctuations. The approach yields an accuracy much better (about an order of magnitude) than is presently possible with standard data reduction methods, because the astrophysical null depth accuracy is no longer limited by the magnitude of the instrumental phase and intensity errors but by uncertainties on their probability distributions. This approach was tested on the sky with the two-aperture fiber nulling instrument mounted on the Palomar Hale telescope. Using our new data analysis approach alone-and no observations of calibrators-we find that error bars on the astrophysical null depth as low as a few 10 -4 can be obtained in the near-infrared, which means that null depths lower than 10 -3 can be reliably measured. This statistical analysis is not specific to our instrument and may be applicable to other interferometers.

Quantifying spatial distribution of snow depth errors from LiDAR using Random Forests

Science.gov (United States)

Tinkham, W.; Smith, A. M.; Marshall, H.; Link, T. E.; Falkowski, M. J.; Winstral, A. H.

2013-12-01

There is increasing need to characterize the distribution of snow in complex terrain using remote sensing approaches, especially in isolated mountainous regions that are often water-limited, the principal source of terrestrial freshwater, and sensitive to climatic shifts and variations. We apply intensive topographic surveys, multi-temporal LiDAR, and Random Forest modeling to quantify snow volume and characterize associated errors across seven land cover types in a semi-arid mountainous catchment at a 1 and 4 m spatial resolution. The LiDAR-based estimates of both snow-off surface topology and snow depths were validated against ground-based measurements across the catchment. Comparison of LiDAR-derived snow depths to manual snow depth surveys revealed that LiDAR based estimates were more accurate in areas of low lying vegetation such as shrubs (RMSE = 0.14 m) as compared to areas consisting of tree cover (RMSE = 0.20-0.35 m). The highest errors were found along the edge of conifer forests (RMSE = 0.35 m), however a second conifer transect outside the catchment had much lower errors (RMSE = 0.21 m). This difference is attributed to the wind exposure of the first site that led to highly variable snow depths at short spatial distances. The Random Forest modeled errors deviated from the field measured errors with a RMSE of 0.09-0.34 m across the different cover types. Results show that snow drifts, which are important for maintaining spring and summer stream flows and establishing and sustaining water-limited plant species, contained 30 × 5-6% of the snow volume while only occupying 10% of the catchment area similar to findings by prior physically-based modeling approaches. This study demonstrates the potential utility of combining multi-temporal LiDAR with Random Forest modeling to quantify the distribution of snow depth with a reasonable degree of accuracy. Future work could explore the utility of Terrestrial LiDAR Scanners to produce validation of snow-on surface

Small scale temporal distribution of radiocesium in undisturbed coniferous forest soil: Radiocesium depth distribution profiles.

Science.gov (United States)

Teramage, Mengistu T; Onda, Yuichi; Kato, Hiroaki

2016-04-01

The depth distribution of pre-Fukushima and Fukushima-derived (137)Cs in undisturbed coniferous forest soil was investigated at four sampling dates from nine months to 18 months after the Fukushima nuclear power plant accident. The migration rate and short-term temporal variability among the sampling profiles were evaluated. Taking the time elapsed since the peak deposition of pre-Fukushima (137)Cs and the median depth of the peaks, its downward displacement rates ranged from 0.15 to 0.67 mm yr(-1) with a mean of 0.46 ± 0.25 mm yr(-1). On the other hand, in each examined profile considerable amount of the Fukushima-derived (137)Cs was found in the organic layer (51%-92%). At this moment, the effect of time-distance on the downward distribution of Fukushima-derived (137)Cs seems invisible as its large portion is still found in layers where organic matter is maximal. This indicates that organic matter seems the primary and preferential sorbent of radiocesium that could be associated with the physical blockage of the exchanging sites by organic-rich dusts that act as a buffer against downward propagation of radiocesium, implying radiocesium to be remained in the root zone for considerable time period. As a result, this soil section can be a potential source of radiation dose largely due to high radiocesium concentration coupled with its low density. Generally, such kind of information will be useful to establish a dynamic safety-focused decision support system to ease and assist management actions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Measurement of relative depth-dose distribution in radiochromic film dosimeters irradiated with 43-70 keV electron beam for industrial application

Science.gov (United States)

Matsui, Shinjiro; Hattori, Takeaki; Nonaka, Takashi; Watanabe, Yuki; Morita, Ippei; Kondo, Junichi; Ishikawa, Masayoshi; Mori, Yoshitaka

2018-05-01

The relative dose in a layer, which is thinner than the thickness of the dosimeter is evaluated using simulated depth-dose distributions, and the measured responses of dosimeters with acceleration voltages from 43 to 70 kV, via ultra-low-energy electron beam (ULEB) irradiation. By stacking thin film dosimeters, we confirmed that the simulated depth-dose distributions coincided with the measured depth-dose curve within the measurement uncertainty (k = 2). Using the measurement dose of the 47 μm dosimeter and the simulated depth-dose distribution, the dose of 11 μm dosimeters in the surface was evaluated within the measurement uncertainty (k = 2). We also verified the effectiveness of this method for a thinner layer by changing the acceleration voltage of the irradiation source. We evaluated the relative dose for an adjusted depth of energy deposition from 4.4 μm to 22.8 μm. As a result, this method was found to be effective for a thickness, which is less than the thickness of the dosimeter. When irradiation conditions are well known with accuracy, using the confirmed relative depth-dose distributions across any dosimeter thickness range, a dose evaluation, in several μm steps will possibly improve the design of industrial ULEB processes.

Cumulative history recorded in the depth distribution of radiocesium in sediments deposited on a sandbar

International Nuclear Information System (INIS)

Tanaka, Kazuya; Kondo, Hiroaki; Sakaguchi, Aya; Takahashi, Yoshio

2015-01-01

We collected sediments deposited on a sandbar from the surface to 20 cm in depth in the Abukuma River to clarify the history of radiocesium derived from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. We analyzed the "1"3"7Cs concentration in the sediments from size-fractioned samples as well as bulk samples. The depth distribution of "1"3"7Cs showed the highest concentration in the deepest sediment layer (18–20 cm) studied, which indicates that sediments with a lower "1"3"7Cs concentration were transported and deposited on sediments having a higher "1"3"7Cs concentration. At the same time, the depth distribution suggests a decrease in radioactivity in provenance areas of the sediments. Analysis of the size-fractioned sediments indicated that the three sediment layers at 4–6 cm, 16–18 cm and 18–20 cm intervals had similar size distribution of "1"3"7Cs and grain size composition although the concentration levels of "1"3"7Cs were different according to their bulk concentrations. The size distribution of "1"3"7Cs also supported the possibility that the decrease in "1"3"7Cs concentration in bulk sediments above 18 cm is due to a decrease in the level of radioactivity in the catchment area. A comparison of the size distribution of "1"3"7Cs between the sediment layers above and below 18 cm suggested that the "1"3"7Cs concentration in the transported fine sediment particles decreased more with time than the "1"3"7Cs concentration in the coarse particles, reflecting the selective transport of the finer particles. The results of this study demonstrated that sediment layers deposited on a sandbar retained the cumulative history of the fluvial transport of radiocesium after the FDNPP accident. - Highlights: • We investigated the history of "1"3"7Cs recorded in sediments in the Abukuma River. • "1"3"7Cs concentration was the highest in the deepest sediment layer studied. • The depth distribution suggests a decrease in radioactivity in

Distribution and abundance of Artemia salina in the Salt Lake Basin (Central Anatolia, Turkey

Directory of Open Access Journals (Sweden)

Alaş Ali

2017-06-01

Full Text Available In this study, the distribution and abundance of Artemia salina in 10 different stations of the Salt Lake basin were investigated. In addition, its relationship to pH, dissolved oxygen, temperature, electrical conductivity and water levels were analyzed. Field studies were carried out from July to August of 2010. Artemia salina was observed in five of these stations. Artemia salina was not seen in some stations that have high electrical conductivity. It is determined that, in the station named Tersakan Lake where electrical conductivity was 154 mS/cm, Artemia salina is more abundant when compared to the other stations. But as underground water pumps that are built for the irrigation of agricultural lands decrease water levels, Artemia salina’s life is under threat.

Distribution, abundance, and habitat use of territorial male Boreal Owls (Aegolius funereus) in northeast Minnesota

Science.gov (United States)

William H. Lane; David E. Andersen; Thomas H. Nicholls

1997-01-01

We conducted nocturnal auditory surveys from 1987-1992 to determine the distribution, abundance, and habitat use of Boreal Owls (Aegolius funereus) in northeast Minnesota. We concentrated our efforts in areas where documented nesting attempts by the owls had occurred, along roadways maintained for winter-time access by motor vehicles, and by...

Topographic, meteorologic, and canopy controls on the scaling characteristics of the spatial distribution of snow depth fields

Science.gov (United States)

Ernesto Trujillo; Jorge A. Ramirez; Kelly J. Elder

2007-01-01

In this study, LIDAR snow depths, bare ground elevations (topography), and elevations filtered to the top of vegetation (topography + vegetation) in five 1-km2 areas are used to determine whether the spatial distribution of snow depth exhibits scale invariance, and the control that vegetation, topography, and winds exert on such behavior. The one-dimensional and mean...

Depth distribution analysis of martensitic transformations in Xe implanted austenitic stainless steel

International Nuclear Information System (INIS)

Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Chechenin, N.G.; Grabaek, L.; Bohr, J.

1988-01-01

In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by 'in situ' RBS/channeling analysis, X-ray diffraction and cross-section transmission electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1x10 20 m -2 . The thickness of the transformed layer increases with fluence to ≅ 150 nm at 1x10 21 m -2 , which far exceeds the range plus straggling of the implanted Xe as calculated by the TRIM computer simulation code. Simulations using the MARLOWE code indicate that the thickness of the transformed layer coincides with the range of the small fraction of ions channeled under random implantation conditions. Using cross sectional TEM on the Xe implanted crystals, the depth distribution of gas inclusions and defects can be directly observed. Using X-ray diffraction on implanted single crystals, the solid epitaxial nature of the Xe inclusions, induced prior to the martensitic transformation, was established. The lattice constant obtained from the broad diffraction peak indicates that the pressure in the inclusions is ≅ 5 GPa. (orig./BHO)

Long-Term Trends in Abundance and Distribution of Manatees (Trichechus Manatus) in the Northern Banana River, Brevard County, Florida

Science.gov (United States)

Provancha, J. A.; Provancha, M. J.

1988-01-01

Four aerial survey projects were conducted between 1977 and 1986 to determine the abundance, density and distribution of West Indian manatees (Trichechus manatus), in the northern Banana River, Kennedy Space Center, Florida. Manatee density and distribution within selected portions of the 78.5 sq km study area were determined. Peak numbers of manatees occurred in spring of each year. The maximum counts increased from 56 in 1978 to 297 in 1986. Manatee abundance was lowest in the winter of each year. Mean density per flight increased from 0.52 manatees/sq km in 1977-78 to 2.73/sq km in 1984-86. This increase may reflect increases in the east coast population or shifts in the population distribution. Distributional changes were observed in the study area through time, with a lower percentage of manatees occurring in industrial areas and a correspondingly higher percentage of manatees in nonindustrial areas by 1985.

Depth distribution of Frank loop defects formed in ion-irradiated stainless steel and its dependence on Si addition

Energy Technology Data Exchange (ETDEWEB)

Chen, Dongyue, E-mail: dychen@safety.n.t.u-tokyo.ac.jp [The University of Tokyo, Department of Nuclear Engineering and Management, School of Engineering, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8656 (Japan); Murakami, Kenta [The University of Tokyo, Nuclear Professional School, School of Engineering, 2-22 Shirakata-Shirane, Tokai-mura, Ibaraki 319-1188 (Japan); Dohi, Kenji; Nishida, Kenji; Soneda, Naoki [Central Research Institute of Electric Power Industry, 2-11-1 Iwado-kita, Komae, Tokyo 201-8511 (Japan); Li, Zhengcao, E-mail: zcli@tsinghua.edu.cn [Tsinghua University, School of Materials Science and Engineering, Beijing 100084 (China); Liu, Li; Sekimura, Naoto [The University of Tokyo, Department of Nuclear Engineering and Management, School of Engineering, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8656 (Japan)

2015-12-15

Although heavy ion irradiation is a good tool to simulate neutron irradiation-induced damages in light water reactor, it produces inhomogeneous defect distribution. Such difference in defect distribution brings difficulty in comparing the microstructure evolution and mechanical degradation between neutron and heavy ion irradiation, and thus needs to be understood. Stainless steel is the typical structural material used in reactor core, and could be taken as an example to study the inhomogeneous defect depth distribution in heavy ion irradiation and its influence on the tested irradiation hardening by nano-indentation. In this work, solution annealed stainless steel model alloys are irradiated by 3 MeV Fe{sup 2+} ions at 400 °C to 3 dpa to produce Frank loops that are mainly interstitial in nature. The silicon content of the model alloys is also tuned to change point defect diffusion, so that the loop depth distribution influenced by diffusion along the irradiation beam direction could be discussed. Results show that in low Si (0% Si) and base Si (0.42% Si) samples the depth distribution of Frank loop density quite well matches the dpa profile calculated by the SRIM code, but in high Si sample (0.95% Si), the loop number density in the near-surface region is very low. One possible explanation could be Si’s role in enhancing the effective vacancy diffusivity, promoting recombination and thus suppressing interstitial Frank loops, especially in the near-surface region, where vacancies concentrate. By considering the loop depth distribution, the tested irradiation hardening is successfully explained by the Orowan model. A hardening coefficient of around 0.30 is obtained for all the three samples. This attempt in interpreting hardening results may make it easier to compare the mechanical degradation between different irradiation experiments.

Distribution of living radiolarians and its response on the environments in spring from the section South China Sea

Science.gov (United States)

Zhang, L.; Hu, W.; Chen, M.; Zeng, L.; Xiang, R.; Zhou, W.

2013-12-01

The composition and spatial (horizontal and vertical) distribution of living radiolarians in spring was firstly studied in the section (18°N and 113°E) South China Sea. Vertical plankton tows were collected at depth-intervals from 0 to 300 m in spring using a closing-type net with 62 um mesh size. And we distinguished the living specimens by staining with Rose Bengal. It dominated by tropical-subtropical warm species in spring from the studied areas. The abundance of nassellarians was the almost same as that of spumellarians in the upper-surface waters (0-25m). In the below-surface waters (25-50m), nassellarian abundance was the almost twice that of spumellarians. And the abundances generally decreased with depth (more than 50m), but nasselarian abundance reduced more quickly. The results showed that the horizontal and vertical distribution patterns of living radiolarians were closely related to the mesoscale eddies. The horizontal distributions of radiolarian abundance were uneven and pachy, which may be related to the complicated mecoscale eddies during the sampling period. That is, there were comparatively high abundances in the upper-surface waters where had the cold eddies development. But in the cold eddies of Meigong River mouth, radiolarian abundance was low due to the large input of fresh water, suggesting that low salinity had more important influence than the nutrient on the radiolarian development and reproduction. Vertically, the highest abundances occurred at the mixed layer in the cold eddies, and gradually decreased with depth. However, in the warm eddies, the maximum abundances were in the thermocline layers, where had an abundant supply of nutrients for radiolarians. This study showed that Didymocyrtis tetrathalamus tetrathalamus mostly occurred at the mixed layer, which should be closely related to the cold eddies and rich nutrition and be limited by the fresh water. Based on the distribution of Didymocyrtis tetrathalamus tetrathalamus, we

Distribution and abundance of fungi in the soils of Taylor Valley, Antarctica

Science.gov (United States)

Connell, L.; Redman, R.; Craig, S.; Rodriguez, R.

2006-01-01

The occurrence and distribution of culturable fungi in Taylor Valley, Antarctica was assessed in terms of soil habitat. Soil transects throughout the valley revealed differential habitat utilization between filamentous and non-filamentous (yeast and yeast-like) fungi. In addition, there were significant differences in species distribution patterns with respect to soil pH, moisture, distance from marine coastline, carbon, chlorophyll a, salinity, elevation and solar inputs. Filamentous fungal abundance is most closely associated with habitats having higher pH, and soil moistures. These close associations were not found with yeast and yeast-like fungi demonstrating that yeast and yeast-like fungi utilize a broader range of habitat. An intensive survey of the Victoria Land is necessary to gain a better understanding of their role in soil functioning and nutrient cycling processes. ?? 2006 Elsevier Ltd. All rights reserved.

Weighted halfspace depth

Czech Academy of Sciences Publication Activity Database

Kotík, Lukáš; Hlubinka, D.; Vencálek, O.

Vol. 46, č. 1 (2010), s. 125-148 ISSN 0023-5954 Institutional research plan: CEZ:AV0Z10750506 Keywords : data depth * nonparametric multivariate analysis * strong consistency of depth * mixture of distributions Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.461, year: 2010 http://library.utia.cas.cz/separaty/2010/SI/kotik-weighted halfspace depth.pdf

Predictive modeling of deep-sea fish distribution in the Azores

Science.gov (United States)

Parra, Hugo E.; Pham, Christopher K.; Menezes, Gui M.; Rosa, Alexandra; Tempera, Fernando; Morato, Telmo

2017-11-01

Understanding the link between fish and their habitat is essential for an ecosystem approach to fisheries management. However, determining such relationship is challenging, especially for deep-sea species. In this study, we applied generalized additive models (GAMs) to relate presence-absence and relative abundance data of eight economically-important fish species to environmental variables (depth, slope, aspect, substrate type, bottom temperature, salinity and oxygen saturation). We combined 13 years of catch data collected from systematic longline surveys performed across the region. Overall, presence-absence GAMs performed better than abundance models and predictions made for the observed data successfully predicted the occurrence of the eight deep-sea fish species. Depth was the most influential predictor of all fish species occurrence and abundance distributions, whereas other factors were found to be significant for some species but did not show such a clear influence. Our results predicted that despite the extensive Azores EEZ, the habitats available for the studied deep-sea fish species are highly limited and patchy, restricted to seamounts slopes and summits, offshore banks and island slopes. Despite some identified limitations, our GAMs provide an improved knowledge of the spatial distribution of these commercially important fish species in the region.

Vertical distribution of archaeal communities associated with anaerobic degradation of pentabromodiphenyl ether (BDE-99) in river-based groundwater recharge with reclaimed water.

Science.gov (United States)

Yan, Yulin; Ma, Mengsi; Liu, Xiang; Ma, Weifang; Li, Yangyao

2018-02-01

When groundwater is recharged with reclaimed water, the presence of trace amounts of biorefractory pentabromodiphenyl ether (PBDE, specifically BDE-99) might cause potential groundwater pollution. A laboratory-scale column was designed to investigate the distribution of the community of archaea in this scenario and the associated anaerobic degradation of BDE-99. The concentration of BDE-99 decreased significantly as soil depth increased, and fluorescence in situ hybridization (FISH) analysis suggested that archaea exerted significant effects on the biodegradation of PBDE. Through 454 pyrosequencing of 16s rRNA genes, we found that the distribution and structure of the archaeal community associated with anaerobic degradation of BDE-99 in the river-based aquifer media changed significantly between different soil depths. The primary debrominated metabolites varied with changes in the vertically distributed archaeal community. The archaea in the surface layer were dominated by Methanomethylovorans, and the middle layer was mainly composed of Nitrososphaera. Nitrosopumilus and Nitrososphaera were equally abundant in the bottom layer. In addition, Methanomethylovorans abundance depended on the depth of soil, and the relative abundance of Nitrosopumilus increased with increasing depth, which was associated with the oxidation-reduction potential and the content of intermediate metabolites. We propose that Nitrososphaera and Nitrosopumilus might be the key archaeal taxa mediating the biodegradation of BDE-99.

Vertical and horizontal larval distribution of an offshore brachyuran crab, Monodaeus couchii, off the south coast of Portugal

Directory of Open Access Journals (Sweden)

Patricia N. Pochelon

2014-06-01

Full Text Available A strong understanding of larval distribution and abundance is of major value in delineating the location and size of a breeding population of deep-sea species such as Monodaeus couchii. In this study, vertical distribution of the larvae of a brachyuran crab, M. couchii, was assessed during two week-long cruises conducted at the end of January 2006 and 2007 off the South Coast of Portugal. Larvae were collected by oblique plankton hauls with a Longhurst-Hardy Plankton Recorder from the surface to 300 m. Abundance and distribution of zoeae I and II were correlated during both years. For all stages, abundance decreased with depth during the day while it increased with depth at night; the larvae thus displayed reverse diel vertical migration. Abundance of zoeae I and II was correlated with chlorophyll a levels, whereas those of later stages were correlated with neither physical parameters (chlorophyll a, temperature or salinity nor each other. An ontogenic shift in vertical distribution explained the results; earlier zoeal stages remain in the food-rich upper water column while later stages were not correlated with any physical parameters (i.e. chlorophyll a, salinity or temperature and migrated to the bottom for settlement.

Mixed poloidal-toroidal magnetic configuration and surface abundance distributions of the Bp star 36 Lyn

Science.gov (United States)

Oksala, M. E.; Silvester, J.; Kochukhov, O.; Neiner, C.; Wade, G. A.; the MiMeS Collaboration

2018-01-01

Previous studies of the chemically peculiar Bp star 36 Lyn revealed a moderately strong magnetic field, circumstellar material and inhomogeneous surface abundance distributions of certain elements. We present in this paper an analysis of 33 high signal-to-noise ratio, high-resolution Stokes IV observations of 36 Lyn obtained with the Narval spectropolarimeter at the Bernard Lyot Telescope at Pic du Midi Observatory. From these data, we compute new measurements of the mean longitudinal magnetic field, Bℓ, using the multiline least-squares deconvolution (LSD) technique. A rotationally phased Bℓ curve reveals a strong magnetic field, with indications for deviation from a pure dipole field. We derive magnetic maps and chemical abundance distributions from the LSD profiles, produced using the Zeeman-Doppler imaging code INVERSLSD. Using a spherical harmonic expansion to characterize the magnetic field, we find that the harmonic energy is concentrated predominantly in the dipole mode (ℓ = 1), with significant contribution from both the poloidal and toroidal components. This toroidal field component is predicted theoretically, but not typically observed for Ap/Bp stars. Chemical abundance maps reveal a helium enhancement in a distinct region where the radial magnetic field is strong. Silicon enhancements are located in two regions, also where the radial field is stronger. Titanium and iron enhancements are slightly offset from the helium enhancements, and are located in areas where the radial field is weak, close to the magnetic equator.

Soft coral abundance on the central Great Barrier Reef: effects of Acanthaster planci, space availability, and aspects of the physical environment

Science.gov (United States)

Fabricius, K. E.

1997-07-01

The distribution and abundance of soft coral genera on reefs of the central Great Barrier Reef was investigated in relation to reef position, recent history of disturbance, wave exposure, substratum slope and depth. Eighty-five 25 m long transects were surveyed at 10 m depth on windward sides of 14 mid- and outer-shelf reefs. A further 75 transects in different zones on one mid-shelf reef (Davies Reef) between 5 and 30 m depth were investigated. The crown-of-thorns starfish Acanthaster planci had caused large-scale mortality of scleractinians on eight of these reefs five to ten years prior to the study, and as a result, scleractinian cover was only 35-55% of that on the six unimpacted reefs. On the impacted reefs, stony corals with massive and encrusting growths form had smaller average colony diameters but similar or slightly lower numerical abundance. In contrast, mean colony size, cover and abundance of branching stony corals showed no difference between impacted and unimpacted reefs. Twenty-four genera of soft corals (in eight families) were recorded, and none showed different abundance or cover in areas of former A. planci impact, compared to unaffected sites. Similarly, no difference was detected among locations in the numbers or area cover of sponges, tunicates, zoanthids, Halimeda or other macro-algae. Mean soft coral cover was 2 to 5% at 10 m on sheltered mid-shelf reefs, and 12 to 17% on more current-exposed reefs. Highest cover and abundances generally occurred on platforms of outer-shelf reefs exposed to relatively strong currents but low wave energy. On Davies Reef, cover and colony numbers of the families Nephtheidae and Xeniidae were low within the zone of wave impact, in flow-protected bays and lagoons, on shaded steep slopes, and at depths above 10 and below 25 m. In contrast, distributions of genera of the family Alcyoniidae were not related to these physical parameters. The physical conditions of a large proportion of habitats appear "sub

Microanalysis of Fluorine Contamination and its Depth Distribution in Zircaloy by the Use of a Charged Particle Nuclear Reaction

Energy Technology Data Exchange (ETDEWEB)

Moeller, E; Starfelt, N

1966-07-15

Fluorine contamination on and below the surface of zircaloy has been studied by means of proton irradiation using a Van de Graaff accelerator and the detection of prompt gamma radiation from the {sup 19}F (p, {alpha}{gamma}) {sup 16}O reaction. Formulae for deriving depth distributions of impurities from the measured counting rates have been derived. The influence of energy straggling on the depth resolution has been studied. Both the total amount and the depth distribution have been measured in samples, which have undergone different treatments. Because of the high yield from the reaction used, a quantity of fluorine less than 0. 01 {mu}g/cm{sup 2} can be detected by this method.

Distributed multi-hypothesis coding of depth maps using texture motion information and optical flow

DEFF Research Database (Denmark)

Salmistraro, Matteo; Zamarin, Marco; Rakêt, Lars Lau

2013-01-01

Distributed Video Coding (DVC) is a video coding paradigm allowing a shift of complexity from the encoder to the decoder. Depth maps are images enabling the calculation of the distance of an object from the camera, which can be used in multiview coding in order to generate virtual views, but also...

Diversity, Distribution, and Abundance of Plants in Lewoh-Lebang in the Lebialem Highlands of Southwestern Cameroon

Directory of Open Access Journals (Sweden)

B. A. Fonge

2013-01-01

Full Text Available A survey was conducted between October 2010 and June 2011 to determine the diversity, distribution, and abundance of plants in 4 sites of the Lebialem highlands and to relate species diversity and abundance to altitude and soil types. Twelve (12 plots, each of 1 ha (250 × 40 m, were surveyed at the submontane and montane altitudes of the sites. One hundred (100 species belonging to 82 genera were identified with the genera Cola and Psychotria being the most represented. Vulnerable species included Guarea thompsonii, Schefflera hierniana, Allanblackia gabonensis, Cyclomorpha solmsii, Vepris trifoliolata, and Xylopia africana. Species such as Xymalos monospora, Tricalysia atherura, and Piptostigma oyemense present in the study area were endemic to Cameroon. Diversity and distribution of plants were affected by parameters such as the altitude and the soil type. Soil analysis revealed that diversity in the study area was affected by the organic carbon, nitrogen, calcium, and the cation exchange capacity of the soil.

Marine litter in the upper São Vicente submarine canyon (SW Portugal): Abundance, distribution, composition and fauna interactions.

Science.gov (United States)

Oliveira, Frederico; Monteiro, Pedro; Bentes, Luis; Henriques, Nuno Sales; Aguilar, Ricardo; Gonçalves, Jorge M S

2015-08-15

Marine litter has become a worldwide environmental problem, tainting all ocean habitats. The abundance, distribution and composition of litter and its interactions with fauna were evaluated in the upper S. Vicente canyon using video images from 3 remote operated vehicle exploratory dives. Litter was present in all dives and the abundance was as high as 3.31 items100m(-1). Mean abundance of litter over rock bottom was higher than on soft substrate. Mean litter abundance was slightly higher than reported for other canyons on the Portuguese margin, but lower in comparison to more urbanized coastal areas of the world. Lost fishing gear was the prevalent type of litter, indicating that the majority of litter originates from maritime sources, mainly fishing activity. Physical contact with sessile fauna and entanglement of specimens were the major impacts of lost fishing gear. Based on the importance of this region for the local fishermen, litter abundance is expected to increase. Copyright © 2015 Elsevier Ltd. All rights reserved.

Abundance, horizontal and vertical distribution of the invasive ctenophore Mnemiopsis leidyi in the central Balitc Sea, November 2007

DEFF Research Database (Denmark)

Huwer, Bastian; Storr-Paulsen, Marie; Riisgaard, Hans Ulrik

2008-01-01

The distribution and abundance of the invasive ctenophore Mnemiopsis leidyi in the Bornholm Basin, an important spawning ground of several fish stocks, and in adjacent areas in the central Baltic Sea was studied in November 2007. The study showed that M. leidyi were relatively small (body length 18...... the halocline. Horizontally, the highest abundances were found north and west of Bornholm, but relatively high densities were also observed in the Slupsk Furrow. The mean abundance was 1.58 ± 2.12 ind. m-2, the peak abundance was 8.92 ind. m-2, and the average and peak population density were 0.03 ± 0.05 and 0.......28 ind. m-3, respectively. The abundances are low compared to densities recently observed in other areas of the Baltic region (e. g. Limfjorden, Åland Sea) and the estimated predation impact on zooplankton by M. leidyi was negligible in November 2007. However, because of the ctenophore’s wide...

Global abundance of planktonic heterotrophic protists in the deep ocean

Science.gov (United States)

Pernice, Massimo C; Forn, Irene; Gomes, Ana; Lara, Elena; Alonso-Sáez, Laura; Arrieta, Jesus M; del Carmen Garcia, Francisca; Hernando-Morales, Victor; MacKenzie, Roy; Mestre, Mireia; Sintes, Eva; Teira, Eva; Valencia, Joaquin; Varela, Marta M; Vaqué, Dolors; Duarte, Carlos M; Gasol, Josep M; Massana, Ramon

2015-01-01

The dark ocean is one of the largest biomes on Earth, with critical roles in organic matter remineralization and global carbon sequestration. Despite its recognized importance, little is known about some key microbial players, such as the community of heterotrophic protists (HP), which are likely the main consumers of prokaryotic biomass. To investigate this microbial component at a global scale, we determined their abundance and biomass in deepwater column samples from the Malaspina 2010 circumnavigation using a combination of epifluorescence microscopy and flow cytometry. HP were ubiquitously found at all depths investigated down to 4000 m. HP abundances decreased with depth, from an average of 72±19 cells ml−1 in mesopelagic waters down to 11±1 cells ml−1 in bathypelagic waters, whereas their total biomass decreased from 280±46 to 50±14 pg C ml−1. The parameters that better explained the variance of HP abundance were depth and prokaryote abundance, and to lesser extent oxygen concentration. The generally good correlation with prokaryotic abundance suggested active grazing of HP on prokaryotes. On a finer scale, the prokaryote:HP abundance ratio varied at a regional scale, and sites with the highest ratios exhibited a larger contribution of fungi molecular signal. Our study is a step forward towards determining the relationship between HP and their environment, unveiling their importance as players in the dark ocean's microbial food web. PMID:25290506

A method for determining the analytical form of a radionuclide depth distribution using multiple gamma spectrometry measurements

Energy Technology Data Exchange (ETDEWEB)

Dewey, Steven Clifford, E-mail: sdewey001@gmail.com [United States Air Force School of Aerospace Medicine, Occupational Environmental Health Division, Health Physics Branch, Radiation Analysis Laboratories, 2350 Gillingham Drive, Brooks City-Base, TX 78235 (United States); Whetstone, Zachary David, E-mail: zacwhets@umich.edu [Radiological Health Engineering Laboratory, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, 1906 Cooley Building, Ann Arbor, MI 48109-2104 (United States); Kearfott, Kimberlee Jane, E-mail: kearfott@umich.edu [Radiological Health Engineering Laboratory, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, 1906 Cooley Building, Ann Arbor, MI 48109-2104 (United States)

2011-06-15

When characterizing environmental radioactivity, whether in the soil or within concrete building structures undergoing remediation or decommissioning, it is highly desirable to know the radionuclide depth distribution. This is typically modeled using continuous analytical expressions, whose forms are believed to best represent the true source distributions. In situ gamma ray spectroscopic measurements are combined with these models to fully describe the source. Currently, the choice of analytical expressions is based upon prior experimental core sampling results at similar locations, any known site history, or radionuclide transport models. This paper presents a method, employing multiple in situ measurements at a single site, for determining the analytical form that best represents the true depth distribution present. The measurements can be made using a variety of geometries, each of which has a different sensitivity variation with source spatial distribution. Using non-linear least squares numerical optimization methods, the results can be fit to a collection of analytical models and the parameters of each model determined. The analytical expression that results in the fit with the lowest residual is selected as the most accurate representation. A cursory examination is made of the effects of measurement errors on the method. - Highlights: > A new method for determining radionuclide distribution as a function of depth is presented. > Multiple measurements are used, with enough measurements to determine the unknowns in analytical functions that might describe the distribution. > The measurements must be as independent as possible, which is achieved through special collimation of the detector. > Although the effects of measurements errors may be significant on the results, an improvement over other methods is anticipated.

Species Distribution Modelling: Contrasting presence-only models with plot abundance data.

Science.gov (United States)

Gomes, Vitor H F; IJff, Stéphanie D; Raes, Niels; Amaral, Iêda Leão; Salomão, Rafael P; de Souza Coelho, Luiz; de Almeida Matos, Francisca Dionízia; Castilho, Carolina V; de Andrade Lima Filho, Diogenes; López, Dairon Cárdenas; Guevara, Juan Ernesto; Magnusson, William E; Phillips, Oliver L; Wittmann, Florian; de Jesus Veiga Carim, Marcelo; Martins, Maria Pires; Irume, Mariana Victória; Sabatier, Daniel; Molino, Jean-François; Bánki, Olaf S; da Silva Guimarães, José Renan; Pitman, Nigel C A; Piedade, Maria Teresa Fernandez; Mendoza, Abel Monteagudo; Luize, Bruno Garcia; Venticinque, Eduardo Martins; de Leão Novo, Evlyn Márcia Moraes; Vargas, Percy Núñez; Silva, Thiago Sanna Freire; Manzatto, Angelo Gilberto; Terborgh, John; Reis, Neidiane Farias Costa; Montero, Juan Carlos; Casula, Katia Regina; Marimon, Beatriz S; Marimon, Ben-Hur; Coronado, Euridice N Honorio; Feldpausch, Ted R; Duque, Alvaro; Zartman, Charles Eugene; Arboleda, Nicolás Castaño; Killeen, Timothy J; Mostacedo, Bonifacio; Vasquez, Rodolfo; Schöngart, Jochen; Assis, Rafael L; Medeiros, Marcelo Brilhante; Simon, Marcelo Fragomeni; Andrade, Ana; Laurance, William F; Camargo, José Luís; Demarchi, Layon O; Laurance, Susan G W; de Sousa Farias, Emanuelle; Nascimento, Henrique Eduardo Mendonça; Revilla, Juan David Cardenas; Quaresma, Adriano; Costa, Flavia R C; Vieira, Ima Célia Guimarães; Cintra, Bruno Barçante Ladvocat; Castellanos, Hernán; Brienen, Roel; Stevenson, Pablo R; Feitosa, Yuri; Duivenvoorden, Joost F; Aymard C, Gerardo A; Mogollón, Hugo F; Targhetta, Natalia; Comiskey, James A; Vicentini, Alberto; Lopes, Aline; Damasco, Gabriel; Dávila, Nállarett; García-Villacorta, Roosevelt; Levis, Carolina; Schietti, Juliana; Souza, Priscila; Emilio, Thaise; Alonso, Alfonso; Neill, David; Dallmeier, Francisco; Ferreira, Leandro Valle; Araujo-Murakami, Alejandro; Praia, Daniel; do Amaral, Dário Dantas; Carvalho, Fernanda Antunes; de Souza, Fernanda Coelho; Feeley, Kenneth; Arroyo, Luzmila; Pansonato, Marcelo Petratti; Gribel, Rogerio; Villa, Boris; Licona, Juan Carlos; Fine, Paul V A; Cerón, Carlos; Baraloto, Chris; Jimenez, Eliana M; Stropp, Juliana; Engel, Julien; Silveira, Marcos; Mora, Maria Cristina Peñuela; Petronelli, Pascal; Maas, Paul; Thomas-Caesar, Raquel; Henkel, Terry W; Daly, Doug; Paredes, Marcos Ríos; Baker, Tim R; Fuentes, Alfredo; Peres, Carlos A; Chave, Jerome; Pena, Jose Luis Marcelo; Dexter, Kyle G; Silman, Miles R; Jørgensen, Peter Møller; Pennington, Toby; Di Fiore, Anthony; Valverde, Fernando Cornejo; Phillips, Juan Fernando; Rivas-Torres, Gonzalo; von Hildebrand, Patricio; van Andel, Tinde R; Ruschel, Ademir R; Prieto, Adriana; Rudas, Agustín; Hoffman, Bruce; Vela, César I A; Barbosa, Edelcilio Marques; Zent, Egleé L; Gonzales, George Pepe Gallardo; Doza, Hilda Paulette Dávila; de Andrade Miranda, Ires Paula; Guillaumet, Jean-Louis; Pinto, Linder Felipe Mozombite; de Matos Bonates, Luiz Carlos; Silva, Natalino; Gómez, Ricardo Zárate; Zent, Stanford; Gonzales, Therany; Vos, Vincent A; Malhi, Yadvinder; Oliveira, Alexandre A; Cano, Angela; Albuquerque, Bianca Weiss; Vriesendorp, Corine; Correa, Diego Felipe; Torre, Emilio Vilanova; van der Heijden, Geertje; Ramirez-Angulo, Hirma; Ramos, José Ferreira; Young, Kenneth R; Rocha, Maira; Nascimento, Marcelo Trindade; Medina, Maria Natalia Umaña; Tirado, Milton; Wang, Ophelia; Sierra, Rodrigo; Torres-Lezama, Armando; Mendoza, Casimiro; Ferreira, Cid; Baider, Cláudia; Villarroel, Daniel; Balslev, Henrik; Mesones, Italo; Giraldo, Ligia Estela Urrego; Casas, Luisa Fernanda; Reategui, Manuel Augusto Ahuite; Linares-Palomino, Reynaldo; Zagt, Roderick; Cárdenas, Sasha; Farfan-Rios, William; Sampaio, Adeilza Felipe; Pauletto, Daniela; Sandoval, Elvis H Valderrama; Arevalo, Freddy Ramirez; Huamantupa-Chuquimaco, Isau; Garcia-Cabrera, Karina; Hernandez, Lionel; Gamarra, Luis Valenzuela; Alexiades, Miguel N; Pansini, Susamar; Cuenca, Walter Palacios; Milliken, William; Ricardo, Joana; Lopez-Gonzalez, Gabriela; Pos, Edwin; Ter Steege, Hans

2018-01-17

Species distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are often spatially biased which may generate inaccuracies in SDMs. Here, we test how the distribution of NHCs and MaxEnt predictions relates to a spatial abundance model, based on a large plot dataset for Amazonian tree species, using inverse distance weighting (IDW). We also propose a new pipeline to deal with inconsistencies in NHCs and to limit the area of occupancy of the species. We found a significant but weak positive relationship between the distribution of NHCs and IDW for 66% of the species. The relationship between SDMs and IDW was also significant but weakly positive for 95% of the species, and sensitivity for both analyses was high. Furthermore, the pipeline removed half of the NHCs records. Presence-only SDM applications should consider this limitation, especially for large biodiversity assessments projects, when they are automatically generated without subsequent checking. Our pipeline provides a conservative estimate of a species' area of occupancy, within an area slightly larger than its extent of occurrence, compatible to e.g. IUCN red list assessments.

Influences of oceanographic features on the distribution and abundance of yellowfin tuna, Thunnus albacares, larvae in the Gulf of Mexico

Science.gov (United States)

Cornic, M.; Rooker, J. R.

2016-02-01

Summer ichthyoplankton surveys were conducted in the northern Gulf of Mexico (NGoM) from 2007-2010 to characterize patterns of distribution and abundance of yellowfin tuna (Thunnus albacares) larvae in this region. Yellowfin tuna larvae were moderately abundant representing 9% of the overall Thunnus larvae collected (18765) and had a percent occurrence ranging from 13 to 57% among surveys. Interannual variations were detected with highest mean densities observed in 2009 (2.2 larvae per 1000m3) and the lowest mean densities observed in 2008 (0.7 larvae per 1000 m3). Generalized additive models were used to investigate the influence of oceanographic conditions on abundance of yellowfin tuna larvae. Increased densities were associated with high sea surface temperatures, positive sea surface heights, and intermediate salinities, revealing that these physicochemical conditions may be favorable for yellowfin tuna larvae. These results indicate that the NGoM is an important spawning and/or nursery habitat for yellowfin tuna and suggest that mesoscale features and physicochemical characteristics of water masses may impact distribution and abundance of yellowfin tuna larvae in the NGoM.

Abundance and population structure of Plesionika narval (Fabricius, 1787 in the Northeastern Atlantic

Directory of Open Access Journals (Sweden)

R. Sousa

2018-04-01

Full Text Available Abstract Analysis of abundance and population structure of Plesionika narval was performed on data concerning 5,255 specimens obtained from 62 fishing sets carried out off the Madeira archipelago (Northeastern Atlantic between 2004 and 2008 in a depth range from 101 to 350 m. Abundance ranged from 0.01 to 19.74 specimens-per-trap and significant differences were found between seasons, probably as a result of an increment of population in the spring during the recruitment season. The analysis of size distribution revealed that the carapace length (CL ranged from 2.45 to 28.61 mm and that mean female size consistently exceeded that of males. Differences in mean CL were statistically significant between depth strata and seasons. Of the specimens sampled, 57.00% were males, 41.88% females and 1.42% undetermined. Sex ratio also differed significantly between seasons according to depth strata, consolidating the hypothesis of the existence of seasonal migrations related with the reproductive cycle of this species. Ovigerous females showed larger sizes and occurred all year around and remain in shallow waters in winter, summer and autumn and move to deeper waters in spring. The highest frequency of ovigerous females was recorded in summer, between 151 and 200 m deep supporting the hypothesis that spawning of this species occurs in shallow waters, especially in late summer.

Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

Science.gov (United States)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2016-01-01

Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

KAUST Repository

Kalaroni, S.

2016-04-12

A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the Singular Evolutive Interpolated Kalman (SEIK) filter, the ensemble variant of the Singular Evolutive Extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in-situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

KAUST Repository

Kalaroni, S.; Tsiaras, K.; Petihakis, G.; Hoteit, Ibrahim; Economou-Amilli, A.; G.Triantafyllou

2016-01-01

A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the Singular Evolutive Interpolated Kalman (SEIK) filter, the ensemble variant of the Singular Evolutive Extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in-situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

Deep-sea scleractinian coral age and depth distributions in the northwest Atlantic for the last 225,000 years

Science.gov (United States)

Robinson, L.F.; Adkins, J.F.; Scheirer, D.S.; Fernandez, D.P.; Gagnon, A.; Waller, R.G.

2007-01-01

Deep-sea corals have grown for over 200,000 yrs on the New England Seamounts in the northwest Atlantic, and this paper describes their distribution both with respect to depth and time. Many thousands of fossil scleractinian corals were collected on a series of cruises from 2003-2005; by contrast, live ones were scarce. On these seamounts, the depth distribution of fossil Desmophyllum dianthus (Esper, 1794) is markedly different to that of the colonial scleractinian corals, extending 750 m deeper in the water column to a distinct cut-off at 2500 m. This cut-off is likely to be controlled by the maximum depth of a notch-shaped feature in the seamount morphology. The ages of D. dianthus corals as determined by U-series measurements range from modern to older than 200,000 yrs. The age distribution is not constant over time, and most corals have ages from the last glacial period. Within the glacial period, increases in coral population density at Muir and Manning Seamounts coincided with times at which large-scale ocean circulation changes have been documented in the deep North Atlantic. Ocean circulation changes have an effect on coral distributions, but the cause of the link is not known. ?? 2007 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.

Abiotic and biotic factors influencing nanoflagellate abundance and distribution in three different seasons in PRE, South China Sea

Science.gov (United States)

Zhang, Xia; Shi, Zhen; Huang, Xiaoping; Li, Xiangfu

2017-07-01

Spatial distribution characteristics of two nanoflagellate groups, together with physico-chemical and biological factors, were studied in three seasons in the Pearl River Estuary (PRE), South China Sea. Nanoflagellates were more abundant in warm periods than that in winter. The average abundance in the three observations (spring, summer and winter) was as follow: 1.28 ± 1.17, 0.88 ± 1.02 and 0.28 ± 0.23 × 103 cells ml-1 of heterotrophic nanoflagellate (HNF), and 1.26 ± 0.85, 0.89 ± 0.77 and 0.65 ± 0.52 × 103 cells ml-1 of pigmented nanoflagellate (PNF). In our three studied seasons, NF density was generally higher in the inner estuary and decreasing to the lowest in the outer estuary. Our results suggested that PNF classes were more sensitive than HNF groups to freshwater discharge. The proportion of PNF gradually increased from spring (49.7%) to winter (67.7%), with the river flow was accordingly decreasing. Moreover, spatial distribution pattern in three seasons showed the response of PNF populations to freshwater input was similar to phytoplankton assemblages in the PRE. Total bacterial and live bacterial abundance (measured by LIVE/DEAD kit) were associated with both two NF components, which implied that NF was a potential predator controlling the bulk abundance of bacteria and proportion of active cells. These results revealed the seasonal and spatial variations of NF abundance in diverse conditions in the PRE and how their response to different ecological processes.

Seasonal Distribution and Historic Trends in Abundance of White Sharks, Carcharodon carcharias, in the Western North Atlantic Ocean

Science.gov (United States)

Curtis, Tobey H.; McCandless, Camilla T.; Carlson, John K.; Skomal, Gregory B.; Kohler, Nancy E.; Natanson, Lisa J.; Burgess, George H.; Hoey, John J.; Pratt, Harold L.

2014-01-01

Despite recent advances in field research on white sharks (Carcharodon carcharias) in several regions around the world, opportunistic capture and sighting records remain the primary source of information on this species in the northwest Atlantic Ocean (NWA). Previous studies using limited datasets have suggested a precipitous decline in the abundance of white sharks from this region, but considerable uncertainty in these studies warrants additional investigation. This study builds upon previously published data combined with recent unpublished records and presents a synthesis of 649 confirmed white shark records from the NWA compiled over a 210-year period (1800-2010), resulting in the largest white shark dataset yet compiled from this region. These comprehensive records were used to update our understanding of their seasonal distribution, relative abundance trends, habitat use, and fisheries interactions. All life stages were present in continental shelf waters year-round, but median latitude of white shark occurrence varied seasonally. White sharks primarily occurred between Massachusetts and New Jersey during summer and off Florida during winter, with broad distribution along the coast during spring and fall. The majority of fishing gear interactions occurred with rod and reel, longline, and gillnet gears. Historic abundance trends from multiple sources support a significant decline in white shark abundance in the 1970s and 1980s, but there have been apparent increases in abundance since the 1990s when a variety of conservation measures were implemented. Though the white shark's inherent vulnerability to exploitation warrants continued protections, our results suggest a more optimistic outlook for the recovery of this iconic predator in the Atlantic. PMID:24918579

Socioeconomic and Ecological Factors Influencing Aedes aegypti Prevalence, Abundance, and Distribution in Dhaka, Bangladesh

Science.gov (United States)

Dhar-Chowdhury, Parnali; Haque, C. Emdad; Lindsay, Robbin; Hossain, Shakhawat

2016-01-01

This study examined household risk factors and prevalence, abundance, and distribution of immature Aedes aegypti and Aedes albopictus, and their association with socioeconomic and ecological factors at urban zonal and household levels in the city of Dhaka, Bangladesh. During the 2011 monsoon, 826 households in 12 randomly selected administrative wards were surveyed for vector mosquitoes. Results revealed that the abundance and distribution of immature Ae. aegypti and Ae. albopictus, and pupae-per-person indices did not vary significantly among the zones with varied socioeconomic status. Of 35 different types of identified wet containers, 30 were infested, and among the 23 pupae-positive container types, nine were defined as the “most productive” for pupae including: disposable plastic containers (12.2% of 550), sealable plastic barrels (12.0%), tires (10.4%), abandoned plastic buckets (9.6%), flower tub and trays (8.5%), refrigerator trays (6.5%), plastic bottles (6.4%), clay pots (4.9%), and water tanks (1.6%). When the function of the containers was assessed, ornamental, discarded, and household repairing and reconstruction-related container categories were found significantly associated with the number of pupae in the households. The purpose of storing water and income variables were significant predictors of possession of containers that were infested by vector mosquitoes. PMID:27022149

Distribution and relative abundance of anchovies (Clupeiformes-engraulididae in the Sepetiba Bay, Rio de Janeiro, Brazil

Directory of Open Access Journals (Sweden)

Márcio de Araújo Silva

2000-01-01

Full Text Available Distribution and relative abundance of juvenile fish of the family Engraulididae in the Sepetiba Bay, Rio de Janeiro, Brazil was assessed to detect patterns of use of the shallows during their early life cycle. Two yearly cycle (March-1996 to February-1997 and March-1997 to February-1998 were studied by a total of 120 beach net samples at five sites, two of them located in the inner Bay and three in the outer Bay near to the sea limit. Six Engraulididae species were identified in two genera: Anchoa januaria, Anchoa marinii, Anchoa tricolor, Anchoa lyolepis, Anchoviella lepidentostole and Anchoviella brevirostris, mainly juveniles in their early life cycle. A. januaria, A. brevirostris, A. lepidentostole and A. tricolor, in decreasing order, were the top numerical abundant species, while A. tricolor and A. januaria showed the highest weight contribution, amounting approximately to 90% of the total number of fish. Spatially, A. tricolor, A. lyolepis and A. marinii distributed mainly in the outer Bay. A. januaria show higher abundance in the inner Bay, while the species of genera Anchoviella show an ample distribution, without a particular zone of higher occurrence. Seasonally, only A. januaria, A. lepidentostole and A. brevirostris presented a clear pattern of occurrence, peaking in the Autumn.A abundância relativa e distribuição espacial de juvenis de peixes da familia Engraulididae ocorrentes na Baía de Sepetiba, Rio de Janeiro, Brasil, foram estudadas visando determinar os padrões de uso da margem continental durante a fase inicial de vida. Dois ciclos anuais (Março-1996 a Fevereiro-1997 e Março-1997 a Fevereiro-1998 foram investigados através de um total de 120 amostragens de arrastos de praia, distribuídas em 5 locais de coleta na margem continental da Baía, duas delas situadas na zona mais interna e três na zona mais externa e próxima do limite com o mar. Foram identificados 6 espécies de Engraulididae, compreendendo dois g

Distribution and sequence homogeneity of an abundant satellite DNA in the beetle, Tenebrio molitor.

Science.gov (United States)

Davis, C A; Wyatt, G R

1989-01-01

The mealworm beetle, Tenebrio molitor, contains an unusually abundant and homogeneous satellite DNA which constitutes up to 60% of its genome. The satellite DNA is shown to be present in all of the chromosomes by in situ hybridization. 18 dimers of the repeat unit were cloned and sequenced. The consensus sequence is 142 nt long and lacks any internal repeat structure. Monomers of the sequence are very similar, showing on average a 2% divergence from the calculated consensus. Variant nucleotides are scattered randomly throughout the sequence although some variants are more common than others. Neighboring repeat units are no more alike than randomly chosen ones. The results suggest that some mechanism, perhaps gene conversion, is acting to maintain the homogeneity of the satellite DNA despite its abundance and distribution on all of the chromosomes. Images PMID:2762148

Community-Weighted Mean Plant Traits Predict Small Scale Distribution of Insect Root Herbivore Abundance.

Directory of Open Access Journals (Sweden)

Ilja Sonnemann

Full Text Available Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae larvae (43% in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height, and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio. Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of

Distribution and abundance of carangidae (Teleostei, Perciformes associated with oceanographic factors along the northeast brazilian exclusive economic zone

Directory of Open Access Journals (Sweden)

Christiane Sampaio de Souza

2008-12-01

Full Text Available This work had as objective to study the distribution and abundance of the Carangidae larvae and to analyze the influence of the hydrological (temperature and salinity and biological factors (phytoplanktonic biomass and zooplanktonic biomass, on the space and temporal distribution of the larvae. Ichthyoplankton was collected during four expeditions from the Northeast Exclusive Economic Zone. Six species (Trachurus lathami, Decapterus punctatus, Chloroscombrus chrysurus, Selene setapinnis, Selene vomer and Elagatis bipinnulata and Caranx- Carangoides complex were identified. D. punctatus was the species most abundant (52% of the total, with higher abundance during the Period 3, while the Period 2 was the period of low abundance. C. chrysurus was the second species in abundance representing 30% of the total of carangid. This species had higher abundance during the Period 2 and the Period 1. However, in Period 3 abundance were lesser. The third species in abundance was T. lathami that corresponded 8% of the total of carangid larvae. S. setapinnis, S. vomer and E. bipinnulata were the species less abundant, representing together 2% of the total identified larvae. The larvae of Caranx- Carangoides complex represented 9% of the carangid total.Este trabalho teve como objetivo estudar a distribuição e abundância das larvas de Carangidae, foi analisada também a influência de fatores hidrológicos (temperatura e salinidade e biológicos (biomassa fitoplanctônica e biomassa zooplanctônica, sobre a distribuição espacial e temporal dessas larvas. O ictioplâncton foi coletado durante quatro expedições: Período 1 (Agosto Outubro 1995, Período 2 (Janeiro Abril 1997, Período 3 (Abril Julho 1998 e Período 4 (Setembro Dezembro 2000, realizadas na Zona Econômica Exclusiva do nordeste. Em um total de 313 larvas foram identificadas 6 espécies (Trachurus lathami, Decapterus punctatus, Chloroscombrus chrysurus, Selene setapinnis, Selene vomer e

Distribution and abundance of Antarctic krill (Euphausia superba) along the Antarctic Peninsula

Science.gov (United States)

Siegel, Volker; Reiss, Christian S.; Dietrich, Kimberly S.; Haraldsson, Matilda; Rohardt, Gerhard

2013-07-01

Net-based data on the abundance, distribution, and demographic patterns of Antarctic krill are quantified from a contemporaneous two ship survey of the Antarctic Peninsula during austral summer 2011. Two survey areas were sampled focussed on Marguerite Bay in the south, and the tip of the Antarctic Peninsula in the north. Data from 177 stations showed that the highest concentrations of krill were found in the southern sampling area. Differences between areas were associated with a few large catches of one year old krill found in anomalously warm and productive waters in Marguerite Bay, and small krill catches in the less-productive, offshore waters in the north. Estimated krill density across the survey area was 3.4 krill m-2, and was low compared to the long-term average of 45 krill m-2 for the Elephant Island area. Overall recruitment between the two survey regions was similar, but per capita recruitment was about 60% lower than historical mean recruitment levels measured at Elephant Island since the late 1970s. Demographic patterns showed small krill concentrated near the coast, and large krill concentrated offshore on the shelf and slope all along the survey area. The offshore distribution of adult krill was delineated by the warm (˜1 °C), low salinity (33.8) water at 30 m, suggesting that most krill were present shoreward of the southern boundary of Antarctic Circumpolar Current Front. Distributions of larvae indicated that three hotspot areas were important for the production of krill: slope areas outside Marguerite Bay and north of the South Shetland Islands, and near the coast around Antarctic Sound. Successful spawning, as inferred from larval abundance, was roughly coincident with the shelf break and not with inshore waters. Given the rapid changes in climate along the Antarctic Peninsula and the lower per capita recruitment observed in recent years, studies comparing and contrasting production, growth, and recruitment across the Peninsula will be

Spatial statistics for modeling of abundance and distribution of wildlife species in the Masai Mara ecosystem, Kenya

NARCIS (Netherlands)

Khaemba, W.M.; Stein, A.

2001-01-01

This study illustrates the use of modern statistical procedures for better wildlife management by addressing three key issues: determination of abundance, modeling of animal distributions and variability of diversity in space and time. Prior information in Markov Chain Monte Carlo (MCMC) methods is

MINERAL ABUNDANCE AND PARTICLE SIZE DISTRIBUTION DERIVED FROM IN-SITU SPECTRA MEASUREMENTS OF YUTU ROVER OF CHANG’E-3

Directory of Open Access Journals (Sweden)

H. Lin

2017-07-01

Full Text Available From geologic perspective, understanding the types, abundance, and size distributions of minerals allows us to address what geologic processes have been active on the lunar and planetary surface. The imaging spectrometer which was carried by the Yutu Rover of Chinese Chang’E-3 mission collected the reflectance at four different sites at the height of ~ 1 m, providing a new insight to understand the lunar surface. The mineral composition and Particle Size Distribution (PSD of these four sites were derived in this study using a Radiative Transfer Model (RTM and Sparse Unmixing (SU algorithm. The endmembers used were clinopyroxene, orthopyroxene, olivine, plagioclase and agglutinate collected from the lunar sample spectral dataset in RELAB. The results show that the agglutinate, clinopyroxene and olivine are the dominant minerals around the landing site. In location Node E, the abundance of agglutinate can reach up to 70 %, and the abundances of clinopyroxene and olivine are around 10 %. The mean particle sizes and the deviations of these endmembers were retrieved. PSDs of all these endmembers are close to normal distribution, and differences exist in the mean particle sizes, indicating the difference of space weathering rate of these endmembers.

Depth distribution of damage in copper irradiated with MeV, Ni and He ions

International Nuclear Information System (INIS)

Narayan, J.; Noggle, T.S.; Oen, O.S.

1975-01-01

Transmission electron microscopy was used to study radiation damage as a function of depth caused by 58 and 4-MeV 58 Ni and 1-MeV He ions in copper single crystals at ambient temperature. The experimental damage density vs penetration depth distributions were compared with calculations based on the atomic collision theory of Lindhard et al. (LSS). For 58-MeV Ni ions, the calculated damage profile using the theoretical LSS value of the electronic stopping parameter (k = 0.167) agrees well with experiment. However, for 4-MeV Ni ions it is necessary to use k = 0.12 to get agreement with the experimental data. In the case of 1-MeV He, the depth location of the calculated damage peak is in good agreement with experiment when the electronic stopping determined by Chu and Powers is used whereas it is about 15 percent too close to the surface using the tables of Northcliffe and Schilling. (auth)

[Potential Carbon Fixation Capability of Non-photosynthetic Microbial Community at Different Depth of the South China Sea and Its Response to Different Electron Donors].

Science.gov (United States)

Fang, Feng; Wang, Lei; Xi, Xue-fei; Hu, Jia-jun; Fu, Xiao-hua; Lu, Bing; Xu, Dian-sheng

2015-05-01

The seawater samples collected from many different areas with different depth in the South China Sea were cultivated using different electron donors respectively. And the variation in the potential carbon fixation capability ( PCFC ) of non-photosynthetic microbial community (NPMC) in seawater with different depth was determined after a cycle of cultivation through the statistic analysis. In addition, the cause for the variation was clarified through analyzing key gene abundance regarding CO2 fixation and characteristics of seawater with different depth. The result showed that the PCFCs of NPMC in seawater with different depth were generally low and had no significant difference when using NaNO2 as the electron donor. The PCFC of NPMC in surface seawater was higher than that in deep seawater when using H2 as the electron donor, on the contrary, the PCFC of NPMC in deep seawater was higher than that in surface seawater when using Na2S2O3 as the electron donor. The abundance of the main CO2 fixation gene cbbL in surface seawater was higher than that in deep seawater while the cbbM gene abundance in deep seawater was higher than that in surface seawater. Most hydrogen-oxidizing bacteria had the cbbL gene, and most sulfur bacteria had the cbbM gene. The tendency of seawater cbbL/cbbM gene abundance with the change of depth revealed that there were different kinds of bacteria accounting for the majority in NPMC fixing CO2 at different depth of ocean, which led to different response of PCFC of NPMC at different depth of the sea to different electron donors. The distributions of dissolved oxygen and inorganic carbon concentration with the change of the depth of the sea might be an important reason leading to the difference of NPMC structure and even the difference of PCFC at different depth of the sea.

Potential damages, seasonal abundance and distribution of Empoasca terminalis Distant (Homoptera: Cicadellidae on soybean in South Sulawesi

Directory of Open Access Journals (Sweden)

Andi Nasruddin

2015-09-01

Full Text Available Plant damages caused by leafhopper, Empoasca terminalis Distant (Homoptera: Cicadellidae on soybean were first encountered in 2007 in Makassar, South Sulawesi. The insect has been constantly associated with soybean crops in the province ever since. The purposes of the present study were to (i evaluate potential yield loss attributable to the leafhopper in an experimental set up, (ii seasonal abundance of E. terminalis, and (iii distribution of E. terminalis in all major soybean-producing areas in the province. Potential yield loss due to the leafhopper was assessed in a field experiment using two large plots. One of the plots was kept leafhopper-free by weekly insecticide sprays; and the other plot was left unsprayed to allow leafhopper infestation to occur. Adult abundance was weekly monitored using a sweep net throughout the season. Nymph abundance was determined by direct count on the plant leaves. Leafhopper distribution was assessed through surveys conducted in all major soybean-producing areas in South Sulawesi, from 2009–2013. The results of the study showed that E. terminalis caused an average yield loss of 26% on susceptible crops without insecticide use. First leafhopper infestation in all planting seasons occurred two weeks after the plant emergence. Rainfall negatively correlated with the leafhopper abundance. The leafhopper existed in all major soybean production areas in the province. Therefore, our results confirmed the status of E. terminalis as an important soybean pest in the region. In addition, crops planted early in the dry season could escape from heavy leafhopper infestation.

Influence of depth on sex-specific energy allocation patterns in a tropical reef fish

Science.gov (United States)

Hoey, J.; McCormick, M. I.; Hoey, A. S.

2007-09-01

The effect of depth on the distribution and sex-specific energy allocation patterns of a common coral reef fish, Chrysiptera rollandi (Pomacentridae), was investigated using depth-stratified collections over a broad depth range (5-39 m) and a translocation experiment. C. rollandi consistently selected rubble habitats at each depth, however abundance patterns did not reflect the availability of the preferred microhabitat suggesting a preference for depth as well as microhabitat. Reproductive investment (gonado-somatic index), energy stores (liver cell density and hepatocyte vacuolation), and overall body condition (hepato-somatic index and Fulton’s K) of female fish varied significantly among depths and among the three reefs sampled. Male conspecifics displayed no variation between depth or reef. Depth influenced growth dynamics, with faster initial growth rates and smaller mean asymptotic lengths with decreasing depth. In female fish, relative gonad weight and overall body condition (Fulton’s K and hepato-somatic index) were generally higher in shallower depths (≤10 m). Hepatic lipid storage was highest at the deepest sites sampled on each reef, whereas hepatic glycogen stores tended to decrease with depth. Depth was found to influence energy allocation dynamics in C. rollandi. While it is unclear what processes directly influenced the depth-related patterns in energy allocation, this study shows that individuals across a broad depth gradient are not all in the same physiological state and may contribute differentially to the population reproductive output.

A note on the distribution and abundance of blue whales (Balaenoptera musculus in the Central and Northeast North Atlantic

Directory of Open Access Journals (Sweden)

Daniel G Pike

2009-09-01

Full Text Available The distribution and abundance of blue whales (Balaenoptera musculus was assessed from ship surveys conducted in the Central and Northeast Atlantic in 1987, 1989, 1995 and 2001. Blue whales were most commonly sighted off western Iceland, and to a lesser extent northeast of Iceland. They were very rare or absent in the Northeast Atlantic. Sightings were combined over all surveys to estimate the detection function using standard line transect methodology, with the addition of a covariate to account for differences between surveys. Total abundance was highest in 1995 (979, 95% CI 137-2,542 and lowest in 1987 (222, 95% CI 115-440. Uncertainty in species identity had little effect on estimates of abundance. There was a significant positive trend in abundance northeast of Iceland and in the total survey area.

How marine upwelling influences the distribution of Artemesia longinaris (Decapoda: Penaeoidea?

Directory of Open Access Journals (Sweden)

Gustavo S Sancinetti

2014-05-01

Full Text Available Upwelling events can occur in most of the oceans altering the water physical, chemical and sediment conditions and consequently the species communities dwelling the areas. For better understanding the behavior of populations inhabiting upwelling regions, the spatial and temporal distribution of a Penaeoidea shrimp was studied correlating it with the abiotic factors that vary during upwelling and non-upwelling periods in an area under influence of Cabo Frio upwelling. Bottom salinity and temperature, organic matter and sediment type from each station were sampled from March 2008 to February 2010, in six stations located between 5 and 45 m depth. The lowest temperatures were recorded during spring and summer for both years with temperature values lower than 19ºC. A total of 26,466 Artemesia longinaris shrimps were captured mainly in 10-35 m depth. Upwelling periods showed significant differences in abundance in relation to non-upwelling periods. The spatial distribution among stations varied according to the temperature with higher abundance in stations with values between 19 and 21ºC. The highest abundance of A. longinaris was recorded in spring and summer when intrusions of the cold waters of South Atlantic Central Waters (SACW were frequent. Thus, the effect of cold water of SACW boosted by the upwelling was a determinant factor in the spatial and temporal distribution of A. longinaris in the studied region.

Seasonal distribution and historic trends in abundance of white sharks, Carcharodon carcharias, in the western North Atlantic Ocean.

Directory of Open Access Journals (Sweden)

Tobey H Curtis

Full Text Available Despite recent advances in field research on white sharks (Carcharodon carcharias in several regions around the world, opportunistic capture and sighting records remain the primary source of information on this species in the northwest Atlantic Ocean (NWA. Previous studies using limited datasets have suggested a precipitous decline in the abundance of white sharks from this region, but considerable uncertainty in these studies warrants additional investigation. This study builds upon previously published data combined with recent unpublished records and presents a synthesis of 649 confirmed white shark records from the NWA compiled over a 210-year period (1800-2010, resulting in the largest white shark dataset yet compiled from this region. These comprehensive records were used to update our understanding of their seasonal distribution, relative abundance trends, habitat use, and fisheries interactions. All life stages were present in continental shelf waters year-round, but median latitude of white shark occurrence varied seasonally. White sharks primarily occurred between Massachusetts and New Jersey during summer and off Florida during winter, with broad distribution along the coast during spring and fall. The majority of fishing gear interactions occurred with rod and reel, longline, and gillnet gears. Historic abundance trends from multiple sources support a significant decline in white shark abundance in the 1970s and 1980s, but there have been apparent increases in abundance since the 1990s when a variety of conservation measures were implemented. Though the white shark's inherent vulnerability to exploitation warrants continued protections, our results suggest a more optimistic outlook for the recovery of this iconic predator in the Atlantic.

Abundance and breeding distribution of seabirds in the northern part of the Danco Coast, Antarctic Peninsula

Directory of Open Access Journals (Sweden)

Mariana A. Juáres

2013-02-01

Full Text Available Seabird abundances and breeding distribution have the potential to serve as ecological indicators. The western Antarctic Peninsula is one of the three sites in the world with the greatest increases in local temperature during the last 50 years. The aim of this study was to monitor the distribution and abundance of breeding populations of seabirds in the northern sector of the Danco Coast, north-west of the Antarctic Peninsula, during the breeding season 2010/11. The birds were the Wilson′s storm petrel (Oceanites oceanicus, South Polar skua (Stercorarius maccormicki, kelp gull (Larus dominicanus, Antarctic tern (Sterna vittata, snowy sheathbill (Chionis alba, chinstrap penguin (Pygoscelis antarctica, southern giant petrel (Macronectes giganteus, gentoo penguin (Pygoscelis papua, Cape petrel (Daption capense and Antarctic shag (Phalacrocorax bransfieldensis. Annual breeding population growth increased in pygoscelids, southern giant petrel and sheathbill, and for the remaining species, breeding population trends were stable. Given that seabird populations can provide valuable information on the conditions of their feeding and nesting environments, this study highlights the need to maintain basics monitoring studies.

Assessment of distribution and abundance estimates for Mariana swiftlets (Aerodramus bartschi) via examination of survey methods

Science.gov (United States)

Johnson, Nathan C.; Haig, Susan M.; Mosher, Stephen M.

2018-01-01

We described past and present distribution and abundance data to evaluate the status of the endangered Mariana Swiftlet (Aerodramus bartschi), a little-known echolocating cave swiftlet that currently inhabits 3 of 5 formerly occupied islands in the Mariana archipelago. We then evaluated the survey methods used to attain these estimates via fieldwork carried out on an introduced population of Mariana Swiftlets on the island of O'ahu, Hawaiian Islands, to derive better methods for future surveys. We estimate the range-wide population of Mariana Swiftlets to be 5,704 individuals occurring in 15 caves on Saipan, Aguiguan, and Guam in the Marianas; and 142 individuals occupying one tunnel on O'ahu. We further confirm that swiftlets have been extirpated from Rota and Tinian and have declined on Aguiguan. Swiftlets have remained relatively stable on Guam and Saipan in recent years. Our assessment of survey methods used for Mariana Swiftlets suggests overestimates depending on the technique used. We suggest the use of night vision technology and other changes to more accurately reflect their distribution, abundance, and status.

Distribution and abundance of fish populations in the Middle Wabash River

International Nuclear Information System (INIS)

Teppen, T.C.; Gammon, J.R.

1976-01-01

A field investigation was made of the distribution and abundance of fish within a 161-km portion of the Wabash River to determine effects of heated effluents as well as changes in water quality on ichthyofaunal communities within the river. Twenty-six sampling stations were electrofished, sequentially, four times in 1974 with extended sampling efforts made in the vicinity of two power-generating stations studied since 1967 and 1968. During August an overall rise in river temperature of 4 0 C was observed from upstream to downstream, with several chemical factors also showing slight increases. Although the majority of species populations were influenced either negatively or positively by the gradient of river conditions available to them, the only statistically significant parameters found in the analysis of community structure involved a lower diversity by weight below Terre Haute and a greater abundance of fish above the Cayuga generating station. Decreases occurred downstream in populations of redhorse (Moxostoma sp.), sauger (Stizostedion canadense), longear sunfish (Lepomis megalotis), and gizzard shad (Dorosoma cepedianum), with increases downstream observed in flathead catfish (Pylodictis olivaris), shortnose gar (Lepisosteus platostomus), longnose gar (E. osseus), and bowfin (Amia calva) populations. Carp (Cyprinus carpio) were present in large numbers throughout the study area with a tremendous population increase evident in recent years. Although species associations were variable among the segments, overall community parameters remained relatively unaffected

Factors affecting the distribution and abundance of exotic earthworms in the Huron Mountain Club, Upper Peninsula, Michigan

Science.gov (United States)

Lindsey M. Shartell; Erik A. Lilleskov; Andrew J. Storer; Lynette R. Potvin; Karl J. Romanowicz

2011-01-01

Exotic earthworms are becoming established in previously earthworm-free areas of the Great Lakes region with the potential to alter forest ecosystems. Understanding the factors controlling their distribution and abundance across the landscape will aid in efforts to determine their consequences and potential forest management solutions.

Testing methods for using high-resolution satellite imagery to monitor polar bear abundance and distribution

Science.gov (United States)

LaRue, Michelle A.; Stapleton, Seth P.; Porter, Claire; Atkinson, Stephen N.; Atwood, Todd C.; Dyck, Markus; Lecomte, Nicolas

2015-01-01

High-resolution satellite imagery is a promising tool for providing coarse information about polar species abundance and distribution, but current applications are limited. With polar bears (Ursus maritimus), the technique has only proven effective on landscapes with little topographic relief that are devoid of snow and ice, and time-consuming manual review of imagery is required to identify bears. Here, we evaluated mechanisms to further develop methods for satellite imagery by examining data from Rowley Island, Canada. We attempted to automate and expedite detection via a supervised spectral classification and image differencing to expedite image review. We also assessed what proportion of a region should be sampled to obtain reliable estimates of density and abundance. Although the spectral signature of polar bears differed from nontarget objects, these differences were insufficient to yield useful results via a supervised classification process. Conversely, automated image differencing—or subtracting one image from another—correctly identified nearly 90% of polar bear locations. This technique, however, also yielded false positives, suggesting that manual review will still be required to confirm polar bear locations. On Rowley Island, bear distribution approximated a Poisson distribution across a range of plot sizes, and resampling suggests that sampling >50% of the site facilitates reliable estimation of density (CV large-scale applications remain limited because of the challenges in automation and the limited environments in which the method can be effectively applied. Improvements in resolution may expand opportunities for its future uses.

Testing methods for using high-resolution satellite imagery to monitor polar bear abundance and distribution

Science.gov (United States)

LaRue, Michelle A.; Stapleton, Seth P.; Porter, Claire; Atkinson, Stephen N.; Atwood, Todd C.; Dyck, Markus; Lecomte, Nicolas

2015-01-01

High-resolution satellite imagery is a promising tool for providing coarse information about polar species abundance and distribution, but current applications are limited. With polar bears (Ursus maritimus), the technique has only proven effective on landscapes with little topographic relief that are devoid of snow and ice, and time-consuming manual review of imagery is required to identify bears. Here, we evaluated mechanisms to further develop methods for satellite imagery by examining data from Rowley Island, Canada. We attempted to automate and expedite detection via a supervised spectral classification and image differencing to expedite image review. We also assessed what proportion of a region should be sampled to obtain reliable estimates of density and abundance. Although the spectral signature of polar bears differed from nontarget objects, these differences were insufficient to yield useful results via a supervised classification process. Conversely, automated image differencing—or subtracting one image from another—correctly identified nearly 90% of polar bear locations. This technique, however, also yielded false positives, suggesting that manual review will still be required to confirm polar bear locations. On Rowley Island, bear distribution approximated a Poisson distribution across a range of plot sizes, and resampling suggests that sampling >50% of the site facilitates reliable estimation of density (CV in certain areas, but large-scale applications remain limited because of the challenges in automation and the limited environments in which the method can be effectively applied. Improvements in resolution may expand opportunities for its future uses.

Measurements of nitrogen depth distribution in the surface of steel with the 14N(d,p0)15N reaction

International Nuclear Information System (INIS)

Didriksson, R.; Goenczi, L.; Sundqvist, B.

1980-01-01

The 14 N(d,p 0 ) 15 N nuclear reaction has been used to measure the nitrogen depth distribution in the surface of steel samples. With a beam energy of 2.5 MeV a depth of 15μm could be analyzed. The depth resolution was 0.7 μm (FWHM) and nitrogen contents down to 0.02 percent could be determined. (author)

Abundance, distribution, diversity and zoogeography of epipelagic copepods off the Egyptian Coast (Mediterranean Sea

Directory of Open Access Journals (Sweden)

Howaida Y. Zakaria

2016-12-01

Full Text Available The abundance, distribution and diversity of epipelagic copepods were studied along the Egyptian Mediterranean Coast during April, August, 2008, February, 2009 and 2010. The geographical distribution and ecological affinities of the recorded species are presented in order to follow up the migrant species that recently entered in the study area. Copepoda was the most dominant zooplankton group, representing 74.14% of the total zooplankton counts. The annual averages of copepod abundance in the coastal, shelf and offshore zones were 699.3, 609.7 and 555.7 ind.m−3, respectively. Spring was the most productive and diversified season. 118 copepod species were identified in the study area; among them twelve species are recorded in the Mediterranean Sea for the first time and 41 species are new records in the Egyptian Mediterranean waters. The community was dominated by Oithona nana, Calocalanus pavo, Nannocalanus minor, Clausocalanus arcuicornis and Paracalanus parvus. The study area could be considered as a crossroad for migration process from Atlantic Ocean in the west and Indian Ocean via Red Sea and Suez Canal from the south. In addition, the maritime activities in the Mediterranean Sea may have contributed into the change of copepod diversity in the study area where some species could have come to the Egyptian Coast from other water systems via ballast water.

Representing distributed cognition in complex systems: how a submarine returns to periscope depth.

Science.gov (United States)

Stanton, Neville A

2014-01-01

This paper presents the Event Analysis of Systemic Teamwork (EAST) method as a means of modelling distributed cognition in systems. The method comprises three network models (i.e. task, social and information) and their combination. This method was applied to the interactions between the sound room and control room in a submarine, following the activities of returning the submarine to periscope depth. This paper demonstrates three main developments in EAST. First, building the network models directly, without reference to the intervening methods. Second, the application of analysis metrics to all three networks. Third, the combination of the aforementioned networks in different ways to gain a broader understanding of the distributed cognition. Analyses have shown that EAST can be used to gain both qualitative and quantitative insights into distributed cognition. Future research should focus on the analyses of network resilience and modelling alternative versions of a system.

Abundance, composition and distribution of simple sequence ...

Indian Academy of Sciences (India)

δ∗(W-29, W-70) = 1.25; δ∗(W-93, W-70 = 0.75)) even though they originate from different geographical regions. We can, therefore, infer that the WSSV sequences are closely related by ancestry. Table 3. Dinucleotide relative abundance in the ...

Study of time variation of terrestrial gamma radiation due to depth distribution of soil moisture content

International Nuclear Information System (INIS)

Yoshioka, Katsuhiro

1994-01-01

An empirical equation was deduced from studies of time variations of terrestrial gamma exposure rate and soil moisture content with depth distribution in the surface layer. It was definitely suggested that the variation of terrestrial gamma exposure rate is most strongly influenced by the change of soil moisture content at 5 cm depth. The seasonal variation with a relative maximum in early autumn and a relative minimum in early spring was clearly obtained in the consequence of long time measurements of terrestrial gamma exposure rate and degree of soil dryness. The diurnal change and phase difference due to the effect of depth were also obtained in the dynamic characteristics of soil moisture content at 3 different depths. From the comparison between measured terrestrial gamma exposure rate and that evaluated from soil moisture content using the empirical equation, it was seen that seasonal variations of the both agreed fairly well as a whole. (author)

Temporal Variations in the Abundance and Composition of Biofilm Communities Colonizing Drinking Water Distribution Pipes

Science.gov (United States)

Kelly, John J.; Minalt, Nicole; Culotti, Alessandro; Pryor, Marsha; Packman, Aaron

2014-01-01

Pipes that transport drinking water through municipal drinking water distribution systems (DWDS) are challenging habitats for microorganisms. Distribution networks are dark, oligotrophic and contain disinfectants; yet microbes frequently form biofilms attached to interior surfaces of DWDS pipes. Relatively little is known about the species composition and ecology of these biofilms due to challenges associated with sample acquisition from actual DWDS. We report the analysis of biofilms from five pipe samples collected from the same region of a DWDS in Florida, USA, over an 18 month period between February 2011 and August 2012. The bacterial abundance and composition of biofilm communities within the pipes were analyzed by heterotrophic plate counts and tag pyrosequencing of 16S rRNA genes, respectively. Bacterial numbers varied significantly based on sampling date and were positively correlated with water temperature and the concentration of nitrate. However, there was no significant relationship between the concentration of disinfectant in the drinking water (monochloramine) and the abundance of bacteria within the biofilms. Pyrosequencing analysis identified a total of 677 operational taxonomic units (OTUs) (3% distance) within the biofilms but indicated that community diversity was low and varied between sampling dates. Biofilms were dominated by a few taxa, specifically Methylomonas, Acinetobacter, Mycobacterium, and Xanthomonadaceae, and the dominant taxa within the biofilms varied dramatically between sampling times. The drinking water characteristics most strongly correlated with bacterial community composition were concentrations of nitrate, ammonium, total chlorine and monochloramine, as well as alkalinity and hardness. Biofilms from the sampling date with the highest nitrate concentration were the most abundant and diverse and were dominated by Acinetobacter. PMID:24858562

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

Satellite-derived NDVI, LST, and climatic factors driving the distribution and abundance of Anopheles mosquitoes in a former malarious area in northwest Argentina.

Science.gov (United States)

Dantur Juri, María Julia; Estallo, Elizabet; Almirón, Walter; Santana, Mirta; Sartor, Paolo; Lamfri, Mario; Zaidenberg, Mario

2015-06-01

Distribution and abundance of disease vectors are directly related to climatic conditions and environmental changes. Remote sensing data have been used for monitoring environmental conditions influencing spatial patterns of vector-borne diseases. The aim of this study was to analyze the effect of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and climatic factors (temperature, humidity, wind velocity, and accumulated rainfall) on the distribution and abundance of Anopheles species in northwestern Argentina using Poisson regression analyses. Samples were collected from December, 2001 to December, 2005 at three localities, Aguas Blancas, El Oculto and San Ramón de la Nueva Orán. We collected 11,206 adult Anopheles species, with the major abundance observed at El Oculto (59.11%), followed by Aguas Blancas (22.10%) and San Ramón de la Nueva Orán (18.79%). Anopheles pseudopunctipennis was the most abundant species at El Oculto, Anopheles argyritarsis predominated in Aguas Blancas, and Anopheles strodei in San Ramón de la Nueva Orán. Samples were collected throughout the sampling period, with the highest peaks during the spring seasons. LST and mean temperature appear to be the most important variables determining the distribution patterns and major abundance of An. pseudopunctipennis and An. argyritarsis within malarious areas. © 2015 The Society for Vector Ecology.

Depth-related distribution of a key gene of the tetraether lipid biosynthetic pathway in marine Thaumarchaeota

NARCIS (Netherlands)

Villanueva, Laura; Schouten, Stefan; Sinninghe Damsté, Jaap S.

2015-01-01

The distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGT) lipids synthesized by Thaumarchaeota has been shown to be temperature-dependent in world oceans. Depth-related differences in the ammonia monooxygenase (amoA) of Thaumarchaeota have led to the classification of 'shallow' and

Effect of land cover, habitat fragmentation and ant colonies on the distribution and abundance of shrews in southern California

Science.gov (United States)

Laakkonen, Juha; Fisher, Robert N.; Case, Ted J.

2001-01-01

Because effects of habitat fragmentation and anthropogenic disturbance on native animals have been relatively little studied in arid areas and in insectivores, we investigated the roles of different land covers, habitat fragmentation and ant colonies on the distribution and abundance of shrews, Notiosorex crawfordi and Sorex ornatus, in southern California.Notiosorex crawfordi was the numerically dominant species (trap-success rate 0·52) occurring in 21 of the 22 study sites in 85% of the 286 pitfall arrays used in this study.Sorex ornatus was captured in 14 of the sites, in 52% of the arrays with a total trap-success rate of 0·2. Neither of the species was found in one of the sites.The population dynamics of the two shrew species were relatively synchronous during the 4–5-year study; the peak densities usually occurred during the spring. Precipitation had a significant positive effect, and maximum temperature a significant negative effect on the trap-success rate of S. ornatus.Occurrence and abundance of shrews varied significantly between sites and years but the size of the landscape or the study site had no effect on the abundance of shrews. The amount of urban edge had no significant effect on the captures of shrews but increased edge allows invasion of the Argentine ants, which had a highly significant negative impact on the abundance of N. crawfordi.At the trap array level, the percentage of coastal sage scrub flora had a significant positive, and the percentage of other flora had a significant negative effect on the abundance of N. crawfordi. The mean canopy height and the abundance of N. crawfordi had a significant positive effect on the occurrence of S. ornatus.Our study suggests that the loss of native coastal sage scrub flora and increasing presence of Argentine ant colonies may significantly effect the distribution and abundance of N. crawfordi. The very low overall population densities of both shrew species in most study sites make both species

The Distribution and Abundance of an Island Population of Koalas (Phascolarctos cinereus) in the Far North of Their Geographic Range

Science.gov (United States)

McGregor, Denise C.; Kerr, Sarah E.; Krockenberger, Andrew K.

2013-01-01

Koalas are an iconic species of charismatic megafauna, of substantial social and conservation significance. They are widely distributed, often at low densities, and individuals can be difficult to detect, making population surveys challenging and costly. Consequently, koala population estimates have been limited and the results inconsistent. The aims of this study were to estimate the distribution, relative abundance and population size of the koalas on Magnetic Island, far north Queensland. Population densities were estimated in 18 different vegetation types present on the island using a Fecal Standing Crop Method. Koala density ranged from 0.404 ha−1, recorded in forest red gum and bloodwood woodland, to absence from eight of the vegetation types surveyed. The second highest density of 0.297 koalas ha−1 was recorded in mixed eucalypt woodland, which covers 45% of the island. The total abundance of koalas on Magnetic Island, not including those present in urban areas, was estimated at 825±175 (SEM). The large variation in koala density across vegetation types reinforces the need for sampling stratification when calculating abundance over large areas, as uniformity of habitat quality cannot be assumed. In this context, koala populations also occur in low densities in areas generally regarded as poor quality koala habitat. These results highlight the importance of protecting vegetation communities not traditionally considered to have high conservation value to koalas, as these habitats may be essential for maintaining viable, widespread, low-density populations. The results from this study provide a baseline to assess future trends in koala distribution, density and abundance on Magnetic Island. PMID:23527258

The distribution and abundance of an island population of Koalas (Phascolarctos cinereus in the far north of their geographic range.

Directory of Open Access Journals (Sweden)

Denise C McGregor

Full Text Available Koalas are an iconic species of charismatic megafauna, of substantial social and conservation significance. They are widely distributed, often at low densities, and individuals can be difficult to detect, making population surveys challenging and costly. Consequently, koala population estimates have been limited and the results inconsistent. The aims of this study were to estimate the distribution, relative abundance and population size of the koalas on Magnetic Island, far north Queensland. Population densities were estimated in 18 different vegetation types present on the island using a Fecal Standing Crop Method. Koala density ranged from 0.404 ha(-1, recorded in forest red gum and bloodwood woodland, to absence from eight of the vegetation types surveyed. The second highest density of 0.297 koalas ha(-1 was recorded in mixed eucalypt woodland, which covers 45% of the island. The total abundance of koalas on Magnetic Island, not including those present in urban areas, was estimated at 825±175 (SEM. The large variation in koala density across vegetation types reinforces the need for sampling stratification when calculating abundance over large areas, as uniformity of habitat quality cannot be assumed. In this context, koala populations also occur in low densities in areas generally regarded as poor quality koala habitat. These results highlight the importance of protecting vegetation communities not traditionally considered to have high conservation value to koalas, as these habitats may be essential for maintaining viable, widespread, low-density populations. The results from this study provide a baseline to assess future trends in koala distribution, density and abundance on Magnetic Island.

Combined evaluation of grazing incidence X-ray fluorescence and X-ray reflectivity data for improved profiling of ultra-shallow depth distributions

Energy Technology Data Exchange (ETDEWEB)

Ingerle, D., E-mail: dingerle@ati.ac.at [Atominstitut, Vienna University of Technology, Stadionallee 2, A-1020 Vienna (Austria); Meirer, F. [Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (Netherlands); Pepponi, G.; Demenev, E.; Giubertoni, D. [MiNALab, CMM-irst, Fondazione Bruno Kessler, Via Sommarive 18, I-38050 Povo (Italy); Wobrauschek, P.; Streli, C. [Atominstitut, Vienna University of Technology, Stadionallee 2, A-1020 Vienna (Austria)

2014-09-01

The continuous downscaling of the process size for semiconductor devices pushes the junction depths and consequentially the implantation depths to the top few nanometers of the Si substrate. This motivates the need for sensitive methods capable of analyzing dopant distribution, total dose and possible impurities. X-ray techniques utilizing the external reflection of X-rays are very surface sensitive, hence providing a non-destructive tool for process analysis and control. X-ray reflectometry (XRR) is an established technique for the characterization of single- and multi-layered thin film structures with layer thicknesses in the nanometer range. XRR spectra are acquired by varying the incident angle in the grazing incidence regime while measuring the specular reflected X-ray beam. The shape of the resulting angle-dependent curve is correlated to changes of the electron density in the sample, but does not provide direct information on the presence or distribution of chemical elements in the sample. Grazing Incidence XRF (GIXRF) measures the X-ray fluorescence induced by an X-ray beam incident under grazing angles. The resulting angle dependent intensity curves are correlated to the depth distribution and mass density of the elements in the sample. GIXRF provides information on contaminations, total implanted dose and to some extent on the depth of the dopant distribution, but is ambiguous with regard to the exact distribution function. Both techniques use similar measurement procedures and data evaluation strategies, i.e. optimization of a sample model by fitting measured and calculated angle curves. Moreover, the applied sample models can be derived from the same physical properties, like atomic scattering/form factors and elemental concentrations; a simultaneous analysis is therefore a straightforward approach. This combined analysis in turn reduces the uncertainties of the individual techniques, allowing a determination of dose and depth profile of the implanted

Dechanneling measurements of defect depth profiles and effective cross-channel distribution of misaligned atoms in ion irradiated gold

International Nuclear Information System (INIS)

Pronko, P.P.

1975-01-01

Defect depth profiles for self ion and He + irradiated gold are obtained from single and multiple scatter dechanneling analysis in single crystal gold films. Quantitative defect densities are obtained through use of atomic scattering cross sections. Integral damage profiles are extracted from the dechanneling spectra and subsequently differentiated to yield the volume concentration of defects as a function of depth. Results from the self ion irradiations suggest that incident ions produce defect distributions across depths much greater than predicted by random stopping theory. This is in agreement with TEM observations of others. Comparison of the experimental profiles is made with theoretical vacancy distributions predicted by defect diffusion in a radiation environment. Similarities are observed for the low fluence irradiations suggesting that profile characteristics may be controlled by rapid migration and loss of interstitials to the film surfaces during irradiation. Information on the across-channel distribution of misaligned atoms in the damaged films is obtained with the steady increase of transverse energy model applied to the dechanneling spectra. A predominance of slight misalignment is observed with no contribution to dechanneling coming from atoms displaced significantly close to the center of the channels. This is in keeping with what is expected for crystal distortions caused by the strain fields associated with vacancy cluster defects

Dechanneling measurements of defect depth profiles and effective cross-channel distribution of misaligned atoms in ion-irradiated gold

International Nuclear Information System (INIS)

Pronko, P.P.

1976-01-01

Defect depth profiles for self-ion and He + irradiated gold are obtained from single and multiple scatter dechanneling analysis in single-crystal gold films. Quantitative defect densities are obtained through use of atomic-scattering cross sections. Integral damage profiles are extracted from the dechanneling spectra and subsequently differentiated to yield the volume concentration of defects as a function of depth. Results from the self-ion irradiations suggest that incident ions produce defect distributions across depths much greater than predicted by random stopping theory. This is in agreement with TEM observations of others. Comparison of the experimental profiles is made with theoretical vacancy distributions predicted by defect diffusion in a radiation environment. Similarities are observed for the low-fluence irradiations, suggesting that profile characteristics may be controlled by rapid migration and loss of interstitials to the film surfaces during irradiation. Information on the across-channel distribution of misaligned atoms in the damaged films is obtained with the steady increase of transverse energy model. A predominance of slight misalignment is observed with no contribution to dechanneling coming from atoms displaced significantly close to the center of the channels. This is in keeping with what is expected for crystal distortions caused by the strain fields associated with vacancy cluster defects. (Auth.)

Diversity, abundance and niche differentiation of ammonia-oxidizing prokaryotes in mud deposits of the eastern China marginal seas

Directory of Open Access Journals (Sweden)

Shaolan eYu

2016-02-01

Full Text Available The eastern China marginal seas are prominent examples of river-dominated ocean margins, whose most characteristic feature is the existence of isolated mud patches on sandy sediments. Ammonia-oxidizing prokaryotes play a crucial role in the nitrogen cycles of many marine environments, including marginal seas. However, few studies have attempted to address the distribution patterns of ammonia-oxidizing prokaryotes in mud deposits of these seas. The horizontal and vertical community composition and abundance of ammonia-oxidizing archaea (AOA and bacteria (AOB were investigated in mud deposits of the South Yellow Sea (SYS and the East China Sea (ECS by using amoA clone libraries and quantitative PCR. The diversity of AOB was comparable or higher in the mud zone of SYS and lower in ECS when compared with AOA. Vertically, surface sediments had generally higher diversity of AOA and AOB than middle and bottom layers. Diversity of AOA and AOB showed significant correlation with latitude. Nitrosopumilus and Nitrosospira lineages dominated AOA and AOB communities, respectively. Both AOA and AOB assemblages exhibited greater variations across different sites than those among various depths at one site. The abundance of bacterial amoA was generally higher than that of archaeal amoA, and both of them decreased with depth. Niche differentiation, which was affected by dissolved oxygen, salinity, ammonia and silicate (SiO32-, was observed between AOA and AOB and among different groups of them. The spatial distribution of AOA and AOB was significantly correlated with δ15NTN and SiO32-, and nitrate and δ13C, respectively. Both archaeal and bacterial amoA abundance correlated strongly with SiO32-. This study improves our understanding of spatial distribution of AOA and AOB in ecosystems featuring oceanic mud deposits.

Diversity, Abundance, and Niche Differentiation of Ammonia-Oxidizing Prokaryotes in Mud Deposits of the Eastern China Marginal Seas.

Science.gov (United States)

Yu, Shaolan; Yao, Peng; Liu, Jiwen; Zhao, Bin; Zhang, Guiling; Zhao, Meixun; Yu, Zhigang; Zhang, Xiao-Hua

2016-01-01

The eastern China marginal seas (ECMS) are prominent examples of river-dominated ocean margins, whose most characteristic feature is the existence of isolated mud patches on sandy sediments. Ammonia-oxidizing prokaryotes play a crucial role in the nitrogen cycles of many marine environments, including marginal seas. However, few studies have attempted to address the distribution patterns of ammonia-oxidizing prokaryotes in mud deposits of these seas. The horizontal and vertical community composition and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were investigated in mud deposits of the South Yellow Sea (SYS) and the East China Sea (ECS) by using amoA clone libraries and quantitative PCR. The diversity of AOB was comparable or higher in the mud zone of SYS and lower in ECS when compared with AOA. Vertically, surface sediments had generally higher diversity of AOA and AOB than middle and bottom layers. Diversity of AOA and AOB showed significant correlation with latitude. Nitrosopumilus and Nitrosospira lineages dominated AOA and AOB communities, respectively. Both AOA and AOB assemblages exhibited greater variations across different sites than those among various depths at one site. The abundance of bacterial amoA was generally higher than that of archaeal amoA, and both of them decreased with depth. Niche differentiation, which was affected by dissolved oxygen, salinity, ammonia, and silicate (SiO[Formula: see text]), was observed between AOA and AOB and among different groups of them. The spatial distribution of AOA and AOB was significantly correlated with δ(15)NTN and SiO[Formula: see text], and nitrate and δ(13)C, respectively. Both archaeal and bacterial amoA abundance correlated strongly with SiO[Formula: see text]. This study improves our understanding of spatial distribution of AOA and AOB in ecosystems featuring oceanic mud deposits.

Mars atmospheric water vapor abundance: 1996-1997

Science.gov (United States)

Sprague, A. L.; Hunten, D. M.; Doose, L. R.; Hill, R. E.

2003-05-01

Measurements of martian atmospheric water vapor made throughout Ls = 18.0°-146.4° (October 3, 1996-July 12, 1997) show changes in Mars humidity on hourly, daily, and seasonal time scales. Because our observing program during the 1996-1997 Mars apparition did not include concomitant measurement of nearby CO 2 bands, high northern latitude data were corrected for dust and aerosol extinction assuming an optical depth of 0.8, consistent with ground-based and HST imaging of northern dust storms. All other measurements with airmass greater than 3.5 were corrected using a total optical depth of 0.5. Three dominant results from this data set are as follows: (1) pre- and post-opposition measurements made with the slit crossing many hours of local time on Mars' Earth-facing disk show a distinct diurnal pattern with highest abundances around and slightly after noon with low abundances in the late afternoon, (2) measurements of water vapor over the Mars Pathfinder landing site (Carl Sagan Memorial Station) on July 12, 1997, found 21 ppt μm in the spatial sector centered near 19° latitude, 36° longitude while abundances around the site varied from as low as 6 to as high as 28 ppt μm, and (3) water vapor abundance is patchy on hourly and daily time scales but follows the usual seasonal trends.

Meiofaunal abundances and faunal similarity on the continental rise off the coast of California

Science.gov (United States)

Rohal, Melissa; Thistle, David; Easton, Erin E.

2014-11-01

Metazoan meiofauna (e.g., nematodes, benthic copepods) play important roles in deep-sea sediment communities, but information as basic as standing stocks is not known for much of the world ocean. We therefore sampled six stations: one near the 2700-m isobath and one near the 3700-m isobath off northern, central, and southern California. We counted benthic copepods, both Desmoscolecidae and nondesmoscolecid nematodes, kinorhynchs, nauplii, and ostracods from multiple-corer samples. Nematodes from our 2700-m and 3700-m stations, and ostracods and nauplii from our 3700-m stations, were unusually abundant compared to those from other stations from comparable depths in the Pacific. Off California, the abundances of benthic copepods, kinorhynchs, and nondesmoscolecids at the 2700-m stations were significantly greater than those at the 3700-m stations. Abundance of benthic copepods was correlated with the percentage of medium sand in the sediment, so sediment texture could be important to them. That of kinorhynchs was correlated with the concentration of chloroplastic-pigment equivalents and percentage nitrogen, so consumable material from the euphotic zone could be important to them. In contrast to the usual pattern of decreasing abundance with depth, Desmoscolecidae abundance in the central region was greater at the 3700-m than at the 2700-m station. The three regions differed significantly in both kinorhynch and ostracod abundances, independently of depth. In the food-poor deep sea, animals are expected to be more abundant where food is plentiful. Unexpectedly, ostracod abundance was negatively correlated with all food variables. A possible explanation is that the natural enemies of ostracods are abundant where food is abundant. Multivariate faunal similarity at 2700 m differed significantly from that at 3700 m, independently of regions. Benthic copepods were most responsible for the difference. Regions also differed in multivariate faunal similarity independently of

Aerial Survey as a Tool to Estimate Abundance and Describe Distribution of a Carcharhinid Species, the Lemon Shark, Negaprion brevirostris

Directory of Open Access Journals (Sweden)

S. T. Kessel

2013-01-01

Full Text Available Aerial survey provides an important tool to assess the abundance of both terrestrial and marine vertebrates. To date, limited work has tested the effectiveness of this technique to estimate the abundance of smaller shark species. In Bimini, Bahamas, the lemon shark (Negaprion brevirostris shows high site fidelity to a shallow sandy lagoon, providing an ideal test species to determine the effectiveness of localised aerial survey techniques for a Carcharhinid species in shallow subtropical waters. Between September 2007 and September 2008, visual surveys were conducted from light aircraft following defined transects ranging in length between 8.8 and 4.4 km. Count results were corrected for “availability”, “perception”, and “survey intensity” to provide unbiased abundance estimates. The abundance of lemon sharks was greatest in the central area of the lagoon during high tide, with a change in abundance distribution to the east and western regions of the lagoon with low tide. Mean abundance of sharks was estimated at 49 (±8.6 individuals, and monthly abundance was significantly positively correlated with mean water temperature. The successful implementation of the aerial survey technique highlighted the potential of further employment for shark abundance assessments in shallow coastal marine environments.

Combined evaluation of grazing incidence X-ray fluorescence and X-ray reflectivity data for improved profiling of ultra-shallow depth distributions

NARCIS (Netherlands)

Ingerle, D.; Meirer, F.; Pepponi, G.; Demenev, E.; Giubertoni, D.; Wobrauschek, P.; Streli, C.

2014-01-01

The continuous downscaling of the process size for semiconductor devices pushes the junction depths and consequentially the implantation depths to the top few nanometers of the Si substrate. This motivates the need for sensitive methods capable of analyzing dopant distribution, total dose and

Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert

Science.gov (United States)

Aguilera-Gómez, Claudia; Ramírez, Iván; Chanamé, Julio

2018-06-01

Aims: We address the existence and origin of the lithium (Li) desert, a region in the Li-Teff plane sparsely populated by stars. Here we analyze some of the explanations that have been suggested for this region, including mixing in the late main sequence, a Li dip origin for stars with low Li abundances in the region, and a possible relation with the presence of planets. Methods: To study the Li desert, we measured the atmospheric parameters and Li abundance of 227 late-F dwarfs and subgiants, chosen to be in the Teff range of the desert and without previous Li abundance measurements. Subsequently, we complemented those with literature data to obtain a homogeneous catalog of 2318 stars, for which we compute masses and ages. We characterize stars surrounding the region of the Li desert. Results: We conclude that stars with low Li abundances below the desert are more massive and more evolved than stars above the desert. Given the unexpected presence of low Li abundance stars in this effective temperature range, we concentrate on finding their origin. We conclude that these stars with low Li abundance do not evolve from stars above the desert: at a given mass, stars with low Li (i.e., below the desert) are more metal-poor. Conclusions: Instead, we suggest that stars below the Li desert are consistent with having evolved from the Li dip, discarding the need to invoke additional mixing to explain this feature. Thus, stars below the Li desert are not peculiar and are only distinguished from other subgiants evolved from the Li dip in that their combination of atmospheric parameters locates them in a range of effective temperatures where otherwise only high Li abundance stars would be found (i.e., stars above the desert). Full Tables 1 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A55This paper includes observations collected at The McDonald Observatory and

The shape of oxygen abundance profiles explored with MUSE

Science.gov (United States)

Sánchez, S. F.; Sánchez-Menguiano, L.; Pérez, I.

2017-11-01

We characterise the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allows us to detect 14345 HII regions with the same image quality as with photometric data, avoiding any dilution effect. We develop a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10) or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence for the outer flattening. We find that the inner drop appears always around 0.5 r_e, while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope of α_{O/H} = - 0.10±0.03 dex/r_e. This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale (r_{O/H}) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (˜0.5 r_{O/H}) and the outer flattening (˜1.5 r_{O/H}).Finally, we find no significant dependence of the dispersion around the negative gradient with any galaxy property, with values compatible with the uncertainties of the derived abundances.

Abundance, distribution and population structure of the copepod Calanus finmarchicus in a springtime right whale feeding area in the southwestern Gulf of Maine

Science.gov (United States)

Wishner, Karen F.; Schoenherr, Jill R.; Beardsley, Robert; Chen, Changsheng

older Calanus were found in the southwestern and northeastern part. This was probably due to the advection of maturing copepods by the regional circulation, especially the near-surface current associated with the movement of the low-salinity surface plume which forms each spring off Cape Cod. The copepod development cycle occurs within a moving frame of reference (i.e. the water itself); thus, peak abundances of the older copepods (those fed on by the whales) occurred later in the spring and further downstream in 1989 (when there were colder springtime temperatures and faster currents) than in 1988 (when the springtime temperatures were warmer and currents slower). Maximum Calanus abundances and biomass and water-colum abundances of older copepodite stages were significantly higher (about double) in 1989 than in 1988, both in the region as a whole and at sites where whales were feeding. Maximum concentrations from the MOCNESS tows were 13,300 m -3 in 1988 and 30,800 m -3 in 1989; however, a thin, visibly-red surface patch of Calanus, sampled in 1989 by a bucket, had a concentration of 331,000 m -3. Copepods were also more aggregated in the vertical (i.e. more highly concentrated at the depth of maximum abundance) in 1989 than in 1988, and samples from whale-feeding areas were more homogeneous in composition (higher proportion of Calanus relative to all zooplankton) in 1989. At smaller spatial and temporal scales, abundances varied by a factor of 1-890 X in samples from horizontal tows spanning about 0.5-1.5 km and by a factor of 1-50 X over 24 h in the same geographic location in whale-feeding areas. Some of this variability was probably due to advection by the semidiurnal tidal currents. Near feeding whales, the copepod spatial distribution was patchy on small scales (with an estimated mean patch "size" of about 500 m), but the patchiness varied in texture interannually. Copepod abundances were much lower in early spring (March 1988) than in later spring (May 1988

Patterns of Insect Abundance and Distribution in Urban Domestic Gardens in Bangalore, India

Directory of Open Access Journals (Sweden)

Madhumitha Jaganmohan

2013-10-01

Full Text Available Domestic gardens may play a vital role in supporting urban insect biodiversity, despite their small size. This paper assesses the abundance, diversity and distribution of insects in urban domestic gardens in the tropics, through a study in the rapidly expanding Indian city of Bangalore. Fifty domestic gardens were studied using a combination of light traps and pitfall traps. We recorded a large number of insects, 2,185 insects from 10 orders, of which ants, bugs, beetles and flies were the most common. We found 25 species of trees (from 160 individuals and 117 species of herbs and shrubs in the 50 sampled domestic gardens. The number of insect orders encountered was significantly related to the number of tree and herb/shrub species. Garden management practices also influenced the abundance and richness of insect orders. Thus, greater numbers of insects were observed in gardens with a greater proportion of bare soil relative to grass area and with less intensive weeding practices. More insect orders were encountered in gardens with a composting pit. Insect numbers were significantly reduced in gardens subjected to pesticide application. Most residents avoided application of pesticides and herbicides, citing health concerns.

Distribution and relative abundance of large whales in a former whaling ground off eastern South America

Directory of Open Access Journals (Sweden)

Artur Andriolo

2010-10-01

Full Text Available Ship-based sighting surveys for cetaceans were conducted in the former whaling ground off the northeastern coast of Brazil. The cruises took place in winter and spring of 1998-2001 with the objectives of investigating current distribution and abundance of cetaceans, particularly large whale species taken during whaling. In 1998 the survey were conducted between the parallels 5°30'W and 9°S and the 200 m isobath and the meridian 033°W. A total of about 3,100 nm were surveyed between 1998 and 2001 Surveys were conducted using line transect methods from about 5-10°S, and from the coast to 33°W. A total of 151 sightings (203 individuals of large whales were recorded on effort. The Antarctic minke whale - Balaenoptera bonaerensis (Burmeister, 1867 was the most frequently sighted species (97 groups/132 individuals; Sighting Rate [SR] = 0.031 groups/nm, being recorded only in offshore waters. Density gradually increased from August to October. Minke whales were distributed throughout the area, both to the north and the south of former whaling ground. Sighting data indicate this is the most abundant species, particularly in the area beyond the continental shelf break. Breeding behavior was observed for Antarctic minke whales, but few groups containing calves were recorded (4.3% of the groups sighted on effort. Three other large whale species were recorded in low numbers: the Bryde's whale - Balaenoptera edeni (Anderson, 1879¹; the sei whale, B. borealis (Lesson, 1828, and the sperm, Physeter macrocephalus (Linnaeus, 1758. Sei, Bryde and sperm whales were regularly caught during whaling operations, but are rare in the area, suggesting they were depleted by whaling and have yet to recover to their pre-explotation abundance. In contrast, minke whales are abundant in this area, suggesting that either they were not substantially depleted, or that they have recovered rapidly. Blue whale, Balaenoptera musculus (Linnaeus, 1758, and fin whale, B. physalus

Seasonal distribution and abundance of cetaceans within French waters- Part I: The North-Western Mediterranean, including the Pelagos sanctuary

Science.gov (United States)

Laran, Sophie; Pettex, Emeline; Authier, Matthieu; Blanck, Aurélie; David, Léa; Dorémus, Ghislain; Falchetto, Hélène; Monestiez, Pascal; Van Canneyt, Olivier; Ridoux, Vincent

2017-07-01

The biodiversity of the Mediterranean Sea is undergoing important changes. Cetaceans, as top predators, are an important component of marine ecosystems. The seasonal distribution and abundance of several cetacean species were studied with a large aerial survey over the North-Western Mediterranean Sea, including the international Pelagos sanctuary, the largest Marine Protected Area (MPA) designed for marine mammals in the Mediterranean. A total of 8 distinct species of cetaceans were identified, and their occurrence within the sanctuary was investigated. Abundance estimates were obtained for three groups of species: the small delphinids (striped dolphins mainly), the bottlenose dolphin and the fin whale. There was a seasonal variation in striped dolphin abundance between winter (57,300 individuals, 95% CI: 34,500-102,000) and summer (130,000, 95% CI: 76,800-222,100). In contrast, bottlenose dolphin winter abundance was thrice that of summer. It was also the only species to exhibit any preference for the Pelagos sanctuary. Fin whale abundance had the reverse pattern with winter abundance (1000 individuals, 95% CI: 500-2500) and summer (2500 individuals, 95% CI: 1500-4300), without any preference for the sanctuary. Risso's dolphins, pilot whales and sperm whales did not exhibit strong seasonal pattern in their abundance. These results provide baseline estimates which can be used to inform conservation policies and instruments such as the Habitats Directive or the recent European Marine Strategy Framework Directive.

Monte Carlo simulation of the electron and X-ray depth distribution for quantitative electron probe microanalysis of PWR spent fuels

Energy Technology Data Exchange (ETDEWEB)

Kwon, Hyoung Mun; Lee, Hyung Kwon; Son, Young Zoon; Chun, Yong Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2011-10-15

Electron probe microanalysis requires several corrections to quantify an element of a specimen. The X-rays produced by the primary beam are created at some depth in the specimen. This distribution is usually represented as the function {Phi}(pz), and it is possible to calculate the correction factors for atomic number and absorption effects. The electron and X-ray depth distributions for a quantitative electron probe micro analysis were simulated by the CASINO Monte Carlo program to quantify some elements of the PWR spent fuel with 50 GWd/tU of burnup and 2 years of cooling time

Monte Carlo simulation of the electron and X-ray depth distribution for quantitative electron probe microanalysis of PWR spent fuels

International Nuclear Information System (INIS)

Kwon, Hyoung Mun; Lee, Hyung Kwon; Son, Young Zoon; Chun, Yong Bum

2011-01-01

Electron probe microanalysis requires several corrections to quantify an element of a specimen. The X-rays produced by the primary beam are created at some depth in the specimen. This distribution is usually represented as the function Φ(pz), and it is possible to calculate the correction factors for atomic number and absorption effects. The electron and X-ray depth distributions for a quantitative electron probe micro analysis were simulated by the CASINO Monte Carlo program to quantify some elements of the PWR spent fuel with 50 GWd/tU of burnup and 2 years of cooling time

Emission Depth Distribution Function of Al 2s Photoelectrons in Al2O3

Science.gov (United States)

Hucek, S.; Zemek, J.; Jablonski, A.; Tilinin, I. S.

The escape probability of Al 2s photoelectrons leaving an aluminum oxide sample (Al2O3) has been studied as a function of depth of origin. It has been found that the escape probability (the so-called emission depth distribution function - DDF) depends strongly on the photoelectron emission direction with respect to that of the incident X-ray beam. In particular, in the emission direction close to that of photon propagation, the DDF differs substantially from the simple Beer-Lambert law and exhibits a nonmonotonic behavior with a maximum in the near-surface region at a depth of about 10 Å. Experimental results are in good agreement with theoretical predictions based on Monte Carlo simulations of the electron transport and with analytical solution of the linearized Boltzmann kinetic equation with appropriate boundary conditions. Both theoretical approaches take into account multiple elastic scattering of photoelectrons on their way out of the sample. It is shown that the commonly used straight line approximation (SLA), which neglects elastic scattering effects, fails to describe adequately experimental data at emission directions close to minima of the differential photoelectric cross section.

Distribution of benthic invertebrates at different depths in a shallow reservoir in the KwaZulu-Natal Midlands

Directory of Open Access Journals (Sweden)

M.J. Samways

1996-08-01

Full Text Available The bottom of a freshwater reservoir in the KwaZulu-Natal Midlands was sampled for macro-invertebrates and macrophytes at depths of 0.5 m, 1 m, 2 m, and 3 m. The water plants Elodea spp. which did not occur much beyond 1 m appeared to be a major deter-minant for the presence of invertebrates. At 2 m and 3 m, when temperature and light decreased greatly, it was replaced by the algae Chara spp. Over 98 of the macroinvertebrate individuals in 21 species and 14 families occurred in water 1 m or less in depth. At 2 m and deeper, there was a rapid decline of species, with only one, a snail, occurring at 3 m. Odonata species occurred only in water 1 m or less in depth. Among the Ephemeroptera, Caenis sp. was abundant at 0.5 m and the most dominant species of all. At 1 m, the most dominant species was Cleon palidulosum of the Baetidae. Both in terms of food for waterfowl and trout, and as a reserve for aquatic macroin vertebrates, the shallow fringe of the reservoir was playing by far the major role compared with the deeper, open water. It is recommended both for biotic conservation and fishing that reservoirs have a shallow rim and constant water levels.

Species-abundance distribution patterns of soil fungi: contribution to the ecological understanding of their response to experimental fire in Mediterranean maquis (southern Italy).

Science.gov (United States)

Persiani, Anna Maria; Maggi, Oriana

2013-01-01

Experimental fires, of both low and high intensity, were lit during summer 2000 and the following 2 y in the Castel Volturno Nature Reserve, southern Italy. Soil samples were collected Jul 2000-Jul 2002 to analyze the soil fungal community dynamics. Species abundance distribution patterns (geometric, logarithmic, log normal, broken-stick) were compared. We plotted datasets with information both on species richness and abundance for total, xerotolerant and heat-stimulated soil microfungi. The xerotolerant fungi conformed to a broken-stick model for both the low- and high intensity fires at 7 and 84 d after the fire; their distribution subsequently followed logarithmic models in the 2 y following the fire. The distribution of the heat-stimulated fungi changed from broken-stick to logarithmic models and eventually to a log-normal model during the post-fire recovery. Xerotolerant and, to a far greater extent, heat-stimulated soil fungi acquire an important functional role following soil water stress and/or fire disturbance; these disturbances let them occupy unsaturated habitats and become increasingly abundant over time.

The penetration depth and lateral distribution of pigment related to the pigment grain size and the calendering of paper

International Nuclear Information System (INIS)

Buelow, K.; Kristiansson, P.; Schueler, B.; Tullander, E.; Oestling, S.; Elfman, M.; Malmqvist, K.; Pallon, J.; Shariff, A.

2002-01-01

The interaction of ink and newspaper has been investigated and the specific question of penetration of ink into the paper has been addressed with a nuclear microprobe using particle induced X-ray emission. The penetration depth of the newsprint is a critical factor in terms of increasing the quality of newsprint and minimising the amount of ink used. The objective of the experiment was to relate the penetration depth of pigment with the calendering of the paper. The dependence of the penetration depth on the pigment grain size was also studied. To study the penetration depth of pigment in paper, cyan ink with Cu as a tracer of the coloured pigment was used. For the study of the penetration depth dependence of pigment size, specially grounded Japanese ink with well-defined pigment grain size was used. This was compared to Swedish ink with pigment grains with normal size-distribution. The results show that the calendering of the paper considerably affects the penetration depth of ink

Spatial pattern of a fish assemblage in a seasonal tropical wetland: effects of habitat, herbaceous plant biomass, water depth, and distance from species sources

Directory of Open Access Journals (Sweden)

Izaias M Fernandes

Full Text Available The influence of habitat, biomass of herbaceous vegetation, depth and distance from permanent water bodies on the structure of fish assemblages of a seasonal floodplain was evaluated using data collected along 22 transects in an area of 25 km² in the floodplain of Cuiabá River, Pantanal, Brazil. Each transect was sampled for fish using throw traps and gillnets during the flood period of 2006. Multivariate multiple regression analysis and multivariate analysis of covariance indicated that depth was the only variable that affected the structure of the fish assemblage, both for quantitative data (abundance and qualitative data (presence-absence. Species such as Neofundulus parvipinnis and Laetacara dorsigera were more abundant in shallower sites (below 25 cm, while Serrasalmus maculatus and Metynnis mola were found mostly in the deepest areas (over 55 cm. However, species such as Hoplias malabaricus and Hoplerythrinus unitaeniatus occurred at all sampled depths. Although the distribution of most species was restricted to a few sites, there was a positive relationship between species richness and depth of the water body. Surprisingly, the replacement of native vegetation by exotic pasture did not affect the fish assemblage in the area, at the probability level considered.

Depth profile distribution of Cr, Cu, Co, Ni and Pb in the sediment cores of Mumbai Harbour Bay

International Nuclear Information System (INIS)

Madhuparna, D.; Hemalatha, P.; Raj, Sanu S.; Jha, S.K.; Tripathi, R.M.

2014-01-01

Estuarine and coastal sediments act as ultimate sink for trace metals that are discharged into the aquatic environment. Sources of environmental contaminants to the coastal system are numerous and may enter the estuarine environment via a number of pathways Mumbai Harbour Bay on the western coast of India, receives low level nuclear wastes and industrial and domestic sewage waste from the surrounding dwellings. Also, the bay is extensively exploited for various other local activities. The present study was carried out in the bay sediment cores to investigate the depth profile distribution of trace element concentration. Biologically significant toxic elements such as Cr, Cu, Co, Ni and Pb were estimated in the sediment cores to find out pattern of distribution in the sediment bed to follow the accumulation of elements with respect to depth

Distribution and abundance of small plastic debris on beaches in the SE Pacific (Chile): a study supported by a citizen science project.

Science.gov (United States)

Hidalgo-Ruz, Valeria; Thiel, Martin

2013-01-01

The accumulation of large and small plastic debris is a problem throughout the world's oceans and coastlines. Abundances and types of small plastic debris have only been reported for some isolated beaches in the SE Pacific, but these data are insufficient to evaluate the situation in this region. The citizen science project "National Sampling of Small Plastic Debris" was supported by schoolchildren from all over Chile who documented the distribution and abundance of small plastic debris on Chilean beaches. Thirty-nine schools and nearly 1000 students from continental Chile and Easter Island participated in the activity. To validate the data obtained by the students, all samples were recounted in the laboratory. The results of the present study showed that the students were able to follow the instructions and generate reliable data. The average abundance obtained was 27 small plastic pieces per m(2) for the continental coast of Chile, but the samples from Easter Island had extraordinarily higher abundances (>800 items per m(2)). The abundance of small plastic debris on the continental coast could be associated with coastal urban centers and their economic activities. The high abundance found on Easter Island can be explained mainly by the transport of plastic debris via the surface currents in the South Pacific Subtropical Gyre, resulting in the accumulation of small plastic debris on the beaches of the island. This first report of the widespread distribution and abundance of small plastic debris on Chilean beaches underscores the need to extend plastic debris research to ecological aspects of the problem and to improve waste management. Copyright © 2013 Elsevier Ltd. All rights reserved.

Varying Land-Use Has an Influence on Wattled and Grey Crowned Cranes’ Abundance and Distribution in Driefontein Grasslands Important Bird Area, Zimbabwe

Science.gov (United States)

Fakarayi, Togarasei; Mashapa, Clayton; Gandiwa, Edson; Kativu, Shakkie

2016-01-01

Three species of cranes are distributed widely throughout southern Africa, but little is known about how they respond to the changes in land-use that have occurred in this region. This study assessed habitat preference of the two crane species across land-use categories of the self contained small scale commercial farms of 30 to 40 ha per household (A1), large scale commercial agriculture farms of > 50 ha per household (A2) and Old Resettlement, farms of crane species abundance. Crane bird counts and data on influencing environmental variables were collected between June and August 2012. Our results show that varying land-use categories had an influence on the abundance and distribution of the Wattled Crane (Bugeranus carunculatus) and the Grey Crowned Crane (Belearica regulorum) across Driefontein Grasslands IBA. The Wattled Crane was widely distributed in the relatively undisturbed A2 farms while the Grey Crowned Crane was associated with the more disturbed land of A1 farms, Old Resettlement and its communal grazing land. Cyperus esculentus and percent (%) bare ground were strong environmental variables best explaining the observed patterns in Wattled Crane abundance across land-use categories. The pattern in Grey Crowned Crane abundance was best explained by soil penetrability, moisture and grass height variables. A holistic sustainable land-use management that takes into account conservation of essential habitats in Driefontein Grasslands IBA is desirable for crane populations and other wetland dependent species that include water birds. PMID:27875552

Varying Land-Use Has an Influence on Wattled and Grey Crowned Cranes' Abundance and Distribution in Driefontein Grasslands Important Bird Area, Zimbabwe.

Science.gov (United States)

Fakarayi, Togarasei; Mashapa, Clayton; Gandiwa, Edson; Kativu, Shakkie

2016-01-01

Three species of cranes are distributed widely throughout southern Africa, but little is known about how they respond to the changes in land-use that have occurred in this region. This study assessed habitat preference of the two crane species across land-use categories of the self contained small scale commercial farms of 30 to 40 ha per household (A1), large scale commercial agriculture farms of > 50 ha per household (A2) and Old Resettlement, farms of crane species abundance. Crane bird counts and data on influencing environmental variables were collected between June and August 2012. Our results show that varying land-use categories had an influence on the abundance and distribution of the Wattled Crane (Bugeranus carunculatus) and the Grey Crowned Crane (Belearica regulorum) across Driefontein Grasslands IBA. The Wattled Crane was widely distributed in the relatively undisturbed A2 farms while the Grey Crowned Crane was associated with the more disturbed land of A1 farms, Old Resettlement and its communal grazing land. Cyperus esculentus and percent (%) bare ground were strong environmental variables best explaining the observed patterns in Wattled Crane abundance across land-use categories. The pattern in Grey Crowned Crane abundance was best explained by soil penetrability, moisture and grass height variables. A holistic sustainable land-use management that takes into account conservation of essential habitats in Driefontein Grasslands IBA is desirable for crane populations and other wetland dependent species that include water birds.

The distribution, abundance, and habitat preference of lovebirds ...

African Journals Online (AJOL)

SARAH

2014-04-30

Apr 30, 2014 ... Key words: Abundance, micro-habitat, preference, riparian, vegetation .... human interference and more food resources availability. In the month of May, June .... force birds to feed on areas of less quality because survival rate ...

Empirical phylogenies and species abundance distributions are consistent with pre-equilibrium dynamics of neutral community models with gene flow

KAUST Repository

Bonnet-Lebrun, Anne-Sophie

2017-03-17

Community characteristics reflect past ecological and evolutionary dynamics. Here, we investigate whether it is possible to obtain realistically shaped modelled communities - i.e., with phylogenetic trees and species abundance distributions shaped similarly to typical empirical bird and mammal communities - from neutral community models. To test the effect of gene flow, we contrasted two spatially explicit individual-based neutral models: one with protracted speciation, delayed by gene flow, and one with point mutation speciation, unaffected by gene flow. The former produced more realistic communities (shape of phylogenetic tree and species-abundance distribution), consistent with gene flow being a key process in macro-evolutionary dynamics. Earlier models struggled to capture the empirically observed branching tempo in phylogenetic trees, as measured by the gamma statistic. We show that the low gamma values typical of empirical trees can be obtained in models with protracted speciation, in pre-equilibrium communities developing from an initially abundant and widespread species. This was even more so in communities sampled incompletely, particularly if the unknown species are the youngest. Overall, our results demonstrate that the characteristics of empirical communities that we have studied can, to a large extent, be explained through a purely neutral model under pre-equilibrium conditions. This article is protected by copyright. All rights reserved.

Empirical phylogenies and species abundance distributions are consistent with pre-equilibrium dynamics of neutral community models with gene flow

KAUST Repository

Bonnet-Lebrun, Anne-Sophie; Manica, Andrea; Eriksson, Anders; Rodrigues, Ana S.L.

2017-01-01

Community characteristics reflect past ecological and evolutionary dynamics. Here, we investigate whether it is possible to obtain realistically shaped modelled communities - i.e., with phylogenetic trees and species abundance distributions shaped similarly to typical empirical bird and mammal communities - from neutral community models. To test the effect of gene flow, we contrasted two spatially explicit individual-based neutral models: one with protracted speciation, delayed by gene flow, and one with point mutation speciation, unaffected by gene flow. The former produced more realistic communities (shape of phylogenetic tree and species-abundance distribution), consistent with gene flow being a key process in macro-evolutionary dynamics. Earlier models struggled to capture the empirically observed branching tempo in phylogenetic trees, as measured by the gamma statistic. We show that the low gamma values typical of empirical trees can be obtained in models with protracted speciation, in pre-equilibrium communities developing from an initially abundant and widespread species. This was even more so in communities sampled incompletely, particularly if the unknown species are the youngest. Overall, our results demonstrate that the characteristics of empirical communities that we have studied can, to a large extent, be explained through a purely neutral model under pre-equilibrium conditions. This article is protected by copyright. All rights reserved.

Picoplankton distribution influenced by thermohaline circulation in the southern Adriatic

Science.gov (United States)

Šilović, Tina; Mihanović, Hrvoje; Batistić, Mirna; Radić, Iris Dupčić; Hrustić, Enis; Najdek, Mirjana

2018-03-01

In this study, we focus on the interactive dynamics between physico-chemical processes and picoplankton distribution in order to advance our current understanding of the roles of various parameters in regulating picoplankton community structure in highly dynamic marine system such as the South Adriatic Sea. The research was carried out between October 2011 and September 2012 along the transect in the northern part of the South Adriatic Pit. The deep water convection occurred in the southern Adriatic during February 2012, with vertical mixing reaching the depth of 500 m. The picoplankton community was highly affected by this mixing event, whilst its compartments each responded differently. During deep water convection low nucleic acid heterotrophic bacteria (LNA HB) and Synechococcus had their lowest abundances (4 × 105 cell ml-1 and 8 × 102 cell ml-1, respectively), picoeucaryotes had their highest abundances (104 cell ml-1), while Prochlorococcus was absent from the area, most likely due to intense cooling and vertical mixing. In March 2012 Eastern Adriatic Current (EAC) brought warm and saline water with more nutrients, which resulted in the proliferation of high nucleic acid heterotrophic bacteria (HNA HB), having maximal abundance (4 × 105 cell ml-1). The re-establishment of Levantine Intermediate Water (LIW) intrusion after the deep water convection resulted in the re-appearance of Prochlorococcus and maximal abundances of Synechococcus (4 × 104 cell ml-1) in May 2012. The distribution of picoheterotrophs was mainly explained by the season, while the distribution of picophytoplankton was explained by the depth. Aside from nutrients, salinity was an important parameter, affecting particularly Prochlorococcus. The re-appearance of Prochlorococcus in the southern Adriatic during the period of LIW intrusion, together with their correlation with salinity, indicates their potential association with LIW. The relationship between Prochloroccocus distribution and

2011 Aerial survey of distribution and abundance of western Pacific leatherback turtles (Dermochelys coriacea) in coastal waters of Oregon and Washington

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Aerial surveys were conducted during 10 - 29 September 2011 to determine distribution and abundance of endangered leatherback turtles (Dermochelys coriacea) in...

Marine litter abundance and distribution on beaches on the Isle of Rügen considering the influence of exposition, morphology and recreational activities.

Science.gov (United States)

Hengstmann, Elena; Gräwe, Dennis; Tamminga, Matthias; Fischer, Elke Kerstin

2017-02-15

The abundance, weight and composition of marine debris were determined at the northwest coast of the Isle of Rügen in 2015. A total number of 1115 macrolitter items were registered, resulting in an abundance of 304±88.96 items per 100m of beach length and therefore being greater than the abundances found for other beaches at the Baltic Sea. Macrolitter items were predominantly composed of plastic, on average 83%. The four beaches under investigation have different exposition as well as touristic levels. The differing influence of wind and water currents as well as recreational activities on the macrolitter at these beaches was detectable. The distribution of items within a beach segment was analyzed by implementing D-GPS and drone aerial photography. The results of this analysis suggested that the identity of the substrate as well as the presence of vegetation are both major influencing factors in the macrolitter distribution. Copyright © 2016 Elsevier Ltd. All rights reserved.

Depth distribution of secondary phases in kesterite Cu2ZnSnS4 by angle-resolved X-ray absorption spectroscopy

Directory of Open Access Journals (Sweden)

J. Just

2017-12-01

Full Text Available The depth distribution of secondary phases in the solar cell absorber material Cu2ZnSnS4 (CZTS is quantitatively investigated using X-ray Absorption Near Edge Structure (XANES analysis at the K-edge of sulfur at varying incidence angles. Varying information depths from several nanometers up to the full thickness is achieved. A quantitative profile of the phase distribution is obtained by a self-consistent fit of a multilayer model to the XANES spectra for different angles. Single step co-evaporated CZTS thin-films are found to exhibit zinc and copper sulfide secondary phases preferentially at the front or back interfaces of the film.

Abundances in the Galactic bulge

Energy Technology Data Exchange (ETDEWEB)

Barbuy, B; Alves-Brito, A [Universidade de Sao Paulo, IAG, Rua do Matao 1226, Sao Paulo 05508-900 (Brazil); Ortolani, S; Zoccali, M [Dipartimento di Astronomia, Universita di Padova, Vicolo dell' Osservatorio 2, I-35122 Padova (Italy); Hill, V; Gomez, A [Observatoire de Paris-Meudon, 92195 Meudon Cedex (France); Melendez, J [Centro de AstrofIsica da Universidade de Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Asplund, M [Max Planck Institute for Astrophysics, Postfach 1317, 85741 Garching (Germany); Bica, E [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, CP 15051, Porto Alegre 91501-970 (Brazil); Renzini, A [Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Minniti, D [Department of Astronomy and Astrophysics, Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)], E-mail: barbuy@astro.iag.usp.br

2008-12-15

The metallicity distribution and abundance ratios of the Galactic bulge are reviewed. Issues raised by recent work of different groups, in particular the high metallicity end, the overabundance of {alpha}-elements in the bulge relative to the thick disc and the measurement of giants versus dwarfs, are discussed. Abundances in the old moderately metal-poor bulge globular clusters are described.

Relative Abundance and Diversity of Bacterial Methanotrophs at the Oxic?Anoxic Interface of the Congo Deep-Sea Fan

OpenAIRE

Bessette, Sandrine; Moalic, Yann; Gautey, S?bastien; Lesongeur, Fran?oise; Godfroy, Anne; Toffin, Laurent

2017-01-01

Sitting at ∼5,000 m water depth on the Congo-Angola margin and ∼760 km offshore of the West African coast, the recent lobe complex of the Congo deep-sea fan receives large amounts of fluvial sediments (3–5% organic carbon). This organic-rich sedimentation area harbors habitats with chemosynthetic communities similar to those of cold seeps. In this study, we investigated relative abundance, diversity and distribution of aerobic methane-oxidizing bacteria (MOB) communities at the oxic–anoxic in...

Abundance of sea kraits correlates with precipitation.

Directory of Open Access Journals (Sweden)

Harvey B Lillywhite

Full Text Available Recent studies have shown that sea kraits (Laticauda spp.--amphibious sea snakes--dehydrate without a source of fresh water, drink only fresh water or very dilute brackish water, and have a spatial distribution of abundance that correlates with freshwater sites in Taiwan. The spatial distribution correlates with sites where there is a source of fresh water in addition to local precipitation. Here we report six years of longitudinal data on the abundance of sea kraits related to precipitation at sites where these snakes are normally abundant in the coastal waters of Lanyu (Orchid Island, Taiwan. The number of observed sea kraits varies from year-to-year and correlates positively with previous 6-mo cumulative rainfall, which serves as an inverse index of drought. Grouped data for snake counts indicate that mean abundance in wet years is nearly 3-fold greater than in dry years, and this difference is significant. These data corroborate previous findings and suggest that freshwater dependence influences the abundance or activity of sea kraits on both spatial and temporal scales. The increasing evidence for freshwater dependence in these and other marine species have important implications for the possible impact of climate change on sea snake distributions.

Microdiversity of an Abundant Terrestrial Bacterium Encompasses Extensive Variation in Ecologically Relevant Traits

Directory of Open Access Journals (Sweden)

Alexander B. Chase

2017-11-01

Full Text Available Much genetic diversity within a bacterial community is likely obscured by microdiversity within operational taxonomic units (OTUs defined by 16S rRNA gene sequences. However, it is unclear how variation within this microdiversity influences ecologically relevant traits. Here, we employ a multifaceted approach to investigate microdiversity within the dominant leaf litter bacterium, Curtobacterium, which comprises 7.8% of the bacterial community at a grassland site undergoing global change manipulations. We use cultured bacterial isolates to interpret metagenomic data, collected in situ over 2 years, together with lab-based physiological assays to determine the extent of trait variation within this abundant OTU. The response of Curtobacterium to seasonal variability and the global change manipulations, specifically an increase in relative abundance under decreased water availability, appeared to be conserved across six Curtobacterium lineages identified at this site. Genomic and physiological analyses in the lab revealed that degradation of abundant polymeric carbohydrates within leaf litter, cellulose and xylan, is nearly universal across the genus, which may contribute to its high abundance in grassland leaf litter. However, the degree of carbohydrate utilization and temperature preference for this degradation varied greatly among clades. Overall, we find that traits within Curtobacterium are conserved at different phylogenetic depths. We speculate that similar to bacteria in marine systems, diverse microbes within this taxon may be structured in distinct ecotypes that are key to understanding Curtobacterium abundance and distribution in the environment.

Nematode diversity, abundance and community structure 50 years after the formation of the volcanic island of Surtsey

Science.gov (United States)

Ilieva-Makulec, K.; Bjarnadottir, B.; Sigurdsson, B. D.

2014-10-01

The soil nematode fauna can give important insights into soil development and other habitat changes that occur during primary succession. We investigated the generic composition, density, distribution and community structure of nematodes 50 years after the formation of a pristine volcanic island, Surtsey, Iceland. Part of the island has received additional nutrient inputs from seagulls breeding there since 1985, while the reminder has been much less affected and is at present found at a different successional sere. In total, 25 genera of nematodes were identified, of which 14 were reported on Surtsey for the first time. Nematode communities were more diverse in the more infertile area outside the gull colony, where 24 genera were found, compared to 18 inside. The trophic structure of the nematode communities showed relatively higher abundance of fungal feeders in the infertile areas, but relatively more bacterial- and plant-feeders inside the colony. Nematode abundance in surface soil was, however, significantly higher within the gull colony, with 16.7 ind. cm-2 compared to 3.6 ind. cm-2 outside. A multivariate analysis indicated that the nematode abundance and distribution on Surtsey were most strongly related to the soil C : N ratio, soil acidity, plant cover and biomass, soil temperature and soil depth.

Inter-epidemic abundance and distribution of potential mosquito vectors for Rift Valley fever virus in Ngorongoro district, Tanzania.

Science.gov (United States)

Mweya, Clement N; Kimera, Sharadhuli I; Mellau, Lesakit S B; Mboera, Leonard E G

2015-01-01

Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that primarily affects ruminants but also has the capacity to infect humans. To determine the abundance and distribution of mosquito vectors in relation to their potential role in the virus transmission and maintenance in disease epidemic areas of Ngorongoro district in northern Tanzania. A cross-sectional entomological investigation was carried out before the suspected RVF outbreak in October 2012. Mosquitoes were sampled both outdoors and indoors using the Centre for Disease Control (CDC) light traps and Mosquito Magnets baited with attractants. Outdoor traps were placed in proximity with breeding sites and under canopy in banana plantations close to the sleeping places of animals. A total of 1,823 mosquitoes were collected, of which 87% (N=1,588) were Culex pipiens complex, 12% (N=226) Aedes aegypti, and 0.5% (N=9) Anopheles species. About two-thirds (67%; N=1,095) of C. pipiens complex and nearly 100% (N=225) of A. aegypti were trapped outdoors using Mosquito Magnets. All Anopheles species were trapped indoors using CDC light traps. There were variations in abundance of C. pipiens complex and A. aegypti among different ecological and vegetation habitats. Over three quarters (78%) of C. pipiens complex and most (85%) of the A. aegypti were trapped in banana and maize farms. Both C. pipiens complex and A. aegypti were more abundant in proximity with cattle and in semi-arid thorn bushes and lower Afro-montane. The highest number of mosquitoes was recorded in villages that were most affected during the RVF epidemic of 2007. Of the tested 150 pools of C. pipiens complex and 45 pools of A. aegypti, none was infected with RVF virus. These results provide insights into unique habitat characterisation relating to mosquito abundances and distribution in RVF epidemic-prone areas of Ngorongoro district in northern Tanzania.

Dworshak Dam impacts assessment and fisheries investigation -- Kokanee depth distribution in Dworshak Reservoir and implications toward minimizing entrainment. Annual progress report, January--December 1994

International Nuclear Information System (INIS)

Maiolie, M.A.; Elam, S.

1996-10-01

The authors measured the day and night depth distribution of kokanee Oncorhynchus nerka kennerlyi directly upstream of Dworshak Dam from October 1993 to December 1994 using split-beam hydroacoustics. At night most kokanee (70%) were distributed in a diffuse layer about 10 m thick. The depth of the layer varied with the season and ranged from 30 to 40 m deep during winter and from 15 to 25 m deep during summer. Nighttime depth of the kokanee layer during summer roughly corresponded to a zone where water temperatures ranged from 7 C to 12 C. Daytime kokanee distribution was much different with kokanee located in dense schools. Most kokanee (70%) were found in a 5--15 m thick layer during summer. Daytime depth distribution was also shallowest during fall and deepest during winter. Dworshak Dam has structures which can be used for selective water withdrawal and can function in depth ranges that will avoid the kokanee layer. Temperature constraints limit the use of selective withdrawal during the spring, summer, and fall, but in the winter, water is nearly isothermal and the full range of selector gate depths may be utilized. From October 1993 to February 1994, selector gates were positioned to withdraw water from above the kokanee layer. The discharge pattern also changed with more water being released during May and July, and less water being released during fall and winter. A combination of these two changes is thought to have increased kokanee densities to a record high of 69 adults/ha

Fitness consequences of habitat variability, trophic position, and energy allocation across the depth distribution of a coral-reef fish

Science.gov (United States)

Goldstein, E. D.; D'Alessandro, E. K.; Sponaugle, S.

2017-09-01

Environmental clines such as latitude and depth that limit species' distributions may be associated with gradients in habitat suitability that can affect the fitness of an organism. With the global loss of shallow-water photosynthetic coral reefs, mesophotic coral ecosystems ( 30-150 m) may be buffered from some environmental stressors, thereby serving as refuges for a range of organisms including mobile obligate reef dwellers. Yet habitat suitability may be diminished at the depth boundary of photosynthetic coral reefs. We assessed the suitability of coral-reef habitats across the majority of the depth distribution of a common demersal reef fish ( Stegastes partitus) ranging from shallow shelf (SS, restrict foraging. Fish in MP environments had a broader diet niche, higher trophic position, and higher muscle C:N ratios compared to shallower environments. High C:N ratios suggest increased tissue lipid content in fish in MP habitats that coincided with higher investment in reproduction based on gonado-somatic index. These results suggest that peripheral MP reefs are suitable habitats for demersal reef fish and may be important refuges for organisms common on declining shallow coral reefs.

Defect distribution in low-temperature molecular beam epitaxy grown Si/Si(100), improved depth profiling with monoenergetic positrons

International Nuclear Information System (INIS)

Szeles, C.; Asoka-Kumar, P.; Lynn, K.G.; Gossmann, H.; Unterwald, F.C.; Boone, T.

1995-01-01

The depth distribution of open-volume defects has been studied in Si(100) crystals grown by molecular beam epitaxy at 300 degree C by the variable-energy monoenergetic positron beam technique combined with well-controlled chemical etching. This procedure gave a 10 nm depth resolution which is a significant improvement over the inherent depth resolving power of the positron beam technique. The epitaxial layer was found to grow defect-free up to 80 nm, from the interface, where small vacancy clusters, larger than divacancies, appear. The defect density then sharply increases toward the film surface. The result clearly shows that the nucleation of small open-volume defects is a precursor state to the breakdown of epitaxy and to the evolution of an amorphous film

Abundance Tomography of Type Ia Supernovae

International Nuclear Information System (INIS)

Stehle, M.; Mazzali, P.A.; Hillebrandt, W.

2005-01-01

An analysis of early time spectra of Type Ia Supernovae is presented. A new method to derive a detailed abundance distribution of the SN ejecta through comparison with synthetic spectra, called 'Abundance Tomography' is introduced and applied to the normal SN Ia 2002bo. Conclusions regarding the explosion mechanism are drawn

Patterns and trends of macrobenthic abundance, biomass and production in the deep Arctic Ocean

Directory of Open Access Journals (Sweden)

Renate Degen

2015-08-01

Full Text Available Little is known about the distribution and dynamics of macrobenthic communities of the deep Arctic Ocean. The few previous studies report low standing stocks and confirm a gradient with declining biomass from the slopes down to the basins, as commonly reported for deep-sea benthos. In this study, we investigated regional differences of faunal abundance and biomass, and made for the first time ever estimates of deep Arctic community production by using a multi-parameter artificial neural network model. The underlying data set combines data from recent field studies with published and unpublished data from the past 20 years, to analyse the influence of water depth, geographical latitude and sea-ice concentration on Arctic benthic communities. We were able to confirm the previously described negative relationship of macrofauna standing stock with water depth in the Arctic deep sea, while also detecting substantial regional differences. Furthermore, abundance, biomass and production decreased significantly with increasing sea-ice extent (towards higher latitudes down to values <200 ind m−2, <65 mg C m−2 and <73 mg C m−2 y−1, respectively. In contrast, stations under the seasonal ice zone regime showed much higher standing stock and production (up to 2500 mg C m−2 y−1, even at depths down to 3700 m. We conclude that particle flux is the key factor structuring benthic communities in the deep Arctic Ocean as it explains both the low values in the ice-covered Arctic basins and the higher values in the seasonal ice zone.

Habitat traits and patterns of abundance of the purple sea urchin, Paracentrotus lividus (Lamarck, 1816), at multiple scales along the north Portuguese coast

Science.gov (United States)

Domínguez, Rula; Domínguez Godino, Jorge; Freitas, Cristiano; Machado, Inês; Bertocci, Iacopo

2015-03-01

Spatial and temporal patterns of abundance and distribution of sea urchins (Paracentrotus lividus) from intertidal rockpools of the north Portuguese coast were examined in relation to physical (surface, altitude, depth, topographic complexity and exposure) and biological (substrate cover by dominant organisms) habitat traits. The methodology was based on a multi-factorial design where the total number and the abundance of urchins in each of six size classes were sampled over a range of spatial scales, from 10s of cm to kms, and a temporal scale of five months. The results highlighted three main features of the studied system: (1) the largest proportion of variability of sea urchins occurred at the smallest scale examined; (2) urchins from different size classes showed different patterns of abundance in relation to habitat traits; (3) variables normally invoked as potential drivers of distribution of urchins at a range of scales, such as hydrodynamics and shore height, were relatively less important than other abiotic (i.e. pool area, pool mean depth calculated over five replicate measures and sand cover) and biological (i.e. space occupancy by the reef-forming polychaete Sabellaria alveolata and mussels vs. availability of bare rock) variables to provide a considerable contribution to the variability of sea urchins. Intertidal populations of sea urchins are abundant on many rocky shores, where they are socially and economically important as food resource and ecologically key as habitat modelers. This study provides new clues on relatively unstudied populations, with relevant implications for possible management decisions, including the implementation of protection schemes able to preserve the main recruitment, settlement and development areas of P. lividus.

Trophic diversity, size and biomass spectrum of Bay of Bengal nematodes: A study case on depth and latitudinal patterns

Science.gov (United States)

Ansari, Kapuli Gani Mohamed Thameemul; Lyla, Somasundharanair; Khan, Syed Ajmal; Bhadury, Punyasloke

2017-09-01

Depth and latitudinal patterns of nematode functional attributes were investigated from 35 stations of Bay of Bengal (BoB) continental shelf. We aim to address whether depth and latitudinal variations can modify nematode community structure and their functional attributes (trophic diversity, size and biomass spectra). Global trend of depth and latitudinal related variations have also been noticed from BoB shelf in terms of nematode abundance and species richness, albeit heterogeneity patterns were encountered in functional attributes. Index of trophic diversity values revealed higher trophic diversity across the BoB shelf and suggested variety of food resource availability. However, downstream analysis of trophic status showed depth and latitude specific patterns but not reflected in terms of size and biomass spectrum. The peaks at different positions clearly visualized heterogeneity in distribution patterns for both size and biomass spectrum and also there was evidence of availability of diversified food resources. Nematode biomass spectra (NBS) constructed for nematode communities showed shift in peak biomass values towards lower to moderate size classes particularly in shallower depth but did not get reflected in latitudes. However, Chennai and Parangipettai transects demonstrated shift in peak biomass values towards higher biomass classes explaining the representation of higher nematode abundance. Our findings concluded that depth and latitudes are physical variables; they may not directly affect nematode community structure and functional attributes but they might influence the other factors such as food availability, sediment deposition and settlement rate. Our observations suggest that the local factors (seasonal character) of phytodetrital food flux can be very important for shaping the nematode community structure and success of nematode functional heterogeneity patterns across the Bay of Bengal shelf.

Spatial Interpolation of Aerosol Optical Depth Pollution: Comparison of Methods for the Development of Aerosol Distribution

Science.gov (United States)

Safarpour, S.; Abdullah, K.; Lim, H. S.; Dadras, M.

2017-09-01

Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters are important due to health impact. One widely available metric of aerosol abundance is the aerosol optical depth (AOD). The AOD is the integrated light extinction coefficient over a vertical atmospheric column of unit cross section, which represents the extent to which the aerosols in that vertical profile prevent the transmission of light by absorption or scattering. Seasonal aerosol optical depth (AOD) values at 550 nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA's Terra satellites, for the 10 years period of 2000 - 2010 were used to test 7 different spatial interpolation methods in the present study. The accuracy of estimations was assessed through visual analysis as well as independent validation based on basic statistics, such as root mean square error (RMSE) and correlation coefficient. Based on the RMSE and R values of predictions made using measured values from 2000 to 2010, Radial Basis Functions (RBFs) yielded the best results for spring, summer and winter and ordinary kriging yielded the best results for fall.

SPATIAL INTERPOLATION OF AEROSOL OPTICAL DEPTH POLLUTION: COMPARISON OF METHODS FOR THE DEVELOPMENT OF AEROSOL DISTRIBUTION

Directory of Open Access Journals (Sweden)

S. Safarpour

2017-09-01

Full Text Available Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters are important due to health impact. One widely available metric of aerosol abundance is the aerosol optical depth (AOD. The AOD is the integrated light extinction coefficient over a vertical atmospheric column of unit cross section, which represents the extent to which the aerosols in that vertical profile prevent the transmission of light by absorption or scattering. Seasonal aerosol optical depth (AOD values at 550 nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS sensor onboard NASA’s Terra satellites, for the 10 years period of 2000 - 2010 were used to test 7 different spatial interpolation methods in the present study. The accuracy of estimations was assessed through visual analysis as well as independent validation based on basic statistics, such as root mean square error (RMSE and correlation coefficient. Based on the RMSE and R values of predictions made using measured values from 2000 to 2010, Radial Basis Functions (RBFs yielded the best results for spring, summer and winter and ordinary kriging yielded the best results for fall.

Taxa Composition, Abundance, Distribution And Diversity Of The ...

African Journals Online (AJOL)

Forty-eight genera of plankton were recorded; nine of Cyanophyceae, thirteen each of Chlorophyceae and Bacillariophyceae, seven of Protozoa and three each of Rotifera and Crustacea. Members of Cyanophyceae dominated the assemblage accounting for 91.77% of the total plankton abundance. All the major plankton ...

Particle and solution phase depth distributions of transuranics and 55Fe in the North Pacific

International Nuclear Information System (INIS)

Livingston, H.D.; Mann, D.R.; Casso, S.A.; Schneider, D.L.; Surprenant, L.D.; Bowen, V.T.

1987-01-01

In situ large volume filtration and chemisorption techniques were used to collect samples from the North Pacific for radiochemical analyses of fallout transuranics and 55 Fe in filterable and filtered phases. The data cover several locations for surface collections and a detailed depth profile north of Hawaii at 30 0 N. The observed partition of these nuclides between suspended particulate and filtered phases is directly linked to the rates at which they are moved downward through the water column in association with sinking particles. Particulate phases in open ocean surface waters contain higher Pu than subsurface particulates. 241 Am was found to exhibit much stronger particle association in accord with its known greater particle reactivity. In the high Pu deep water layer, particle associated Pu dropped to close to 1% of total Pu concentration. Together with a correlated increase in the proportion of oxidized Pu in this layer close to the sediment-water interface, this is clear evidence of remobilization of Pu from particles at, or near to, the interface. 55 Fe distributions on filtered particulates indicate a much deeper depth distribution relative to the transuranics. This may reflect both a higher particle association reactivity in respect to scavenging and a longer exposure history to scavenging. (author)

Relationship between viral and prokaryotic abundance on the Bajo O’Higgins 1 Seamount (Humboldt Current System off Chile

Directory of Open Access Journals (Sweden)

Oscar E. Chiang

2007-03-01

Full Text Available There is little known about the ecology of microbial communities living in the water column over seamounts. Here, for the first time, the spatial distribution and abundance of virus-like particles (VLP are described over a seamount. The association between VLP distribution, prokaryotic abundance, and environmental variables is also analyzed. Sampling was conducted in December 2004 on the Bajo O’Higgins 1 seamount (32°54’S, 73°53’W located in the Humboldt Current System off Chile. A oxygen minimum layer (OMZ was clearly present between 130 and 280 m in the water column over the seamount. Water samples were taken with Niskin bottles at 10 oceanographic stations over the seamount at depths of 5, 20, 50, 75, 100, and 150 m and at the benthic boundary layer (BBL; 5-12 m over the sediments. Temperature, salinity, oxygen, chlorophyll , and phaeopigments were measured at each station. Viral and prokaryotic abundances were determined with fluorochrome SYBR Green I. Viral abundance ranged from 1.53 x 109 VLP L-1 - 16.48 x 109 VLP L-1, whereas prokaryotic abundance ranged from 1.78 x 10 8 cell L-1 - 14.91 x 108 cell L-1. The virus-like particle/prokaryote ratio varied widely among the analyzed layers (i.e. surface, OMZ, and BBL, probably due to the presence of different prokaryotic and viral assemblages in each layer. Our results indicate that the environmental conditions, mainly the concentration of dissolved oxygen in the water column over Bajo O’Higgins 1 seamount, shape the association between viral and prokaryotic abundance.

Observations of distributed snow depth and snow duration within diverse forest structures in a maritime mountain watershed

Science.gov (United States)

Dickerson-Lange, Susan E.; Lutz, James A.; Gersonde, Rolf; Martin, Kael A.; Forsyth, Jenna E.; Lundquist, Jessica D.

2015-11-01

Spatially distributed snow depth and snow duration data were collected over two to four snow seasons during water years 2011-2014 in experimental forest plots within the Cedar River Municipal Watershed, 50 km east of Seattle, Washington, USA. These 40 × 40 m forest plots, situated on the western slope of the Cascade Range, include unthinned second-growth coniferous forests, variable density thinned forests, forest gaps in which a 20 m diameter (approximately equivalent to one tree height) gap was cut in the middle of each plot, and old-growth forest. Together, this publicly available data set includes snow depth and density observations from manual snow surveys, distributed snow duration observations from ground temperature sensors and time-lapse cameras, meteorological data collected at two open locations and three forested locations, and forest canopy data from airborne light detection and ranging (LiDAR) data and hemispherical photographs. These colocated snow, meteorological, and forest data have the potential to improve understanding of forest influences on snow processes, and provide a unique model-testing data set for hydrological analyses in a forested, maritime watershed. We present empirical snow depletion curves within forests to illustrate an application of these data to improve subgrid representation of snow cover in distributed modeling.

Fish distribution and abundance in mediterranean streams:the role of habitat quality, spatial context, and movement patterns

OpenAIRE

Pires, Daniel Filipe Carvalho Miranda, 1977-

2012-01-01

Tese de doutoramento, Biologia (Ecologia), Universidade de Lisboa, Faculdade de Ciências, 2012 Patterns of fish distribution and abundance in streams are currently thought of as a product of multi-scale factors. Local habitats, spatial relationships and movement are increasingly emerging as drivers of population and assemblage dynamics, though the way in which these factors may interplay remains poorly addressed, particularly in temporary streams. This dissertation addressed the role of mu...

AFSC/RACE/FBEP/Ryer: Polychaete worm tubes modify juvenile northern rock sole Lepidopsetta polyxystra depth distribution in Kodiak nurseries

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset is from a study that evaluates whether inter-annual variability in the depth distribution of juvenile northern rock sole on their nursery grounds around...

Inferring river bathymetry via Image-to-Depth Quantile Transformation (IDQT)

Science.gov (United States)

Legleiter, Carl

2016-01-01

Conventional, regression-based methods of inferring depth from passive optical image data undermine the advantages of remote sensing for characterizing river systems. This study introduces and evaluates a more flexible framework, Image-to-Depth Quantile Transformation (IDQT), that involves linking the frequency distribution of pixel values to that of depth. In addition, a new image processing workflow involving deep water correction and Minimum Noise Fraction (MNF) transformation can reduce a hyperspectral data set to a single variable related to depth and thus suitable for input to IDQT. Applied to a gravel bed river, IDQT avoided negative depth estimates along channel margins and underpredictions of pool depth. Depth retrieval accuracy (R25 0.79) and precision (0.27 m) were comparable to an established band ratio-based method, although a small shallow bias (0.04 m) was observed. Several ways of specifying distributions of pixel values and depths were evaluated but had negligible impact on the resulting depth estimates, implying that IDQT was robust to these implementation details. In essence, IDQT uses frequency distributions of pixel values and depths to achieve an aspatial calibration; the image itself provides information on the spatial distribution of depths. The approach thus reduces sensitivity to misalignment between field and image data sets and allows greater flexibility in the timing of field data collection relative to image acquisition, a significant advantage in dynamic channels. IDQT also creates new possibilities for depth retrieval in the absence of field data if a model could be used to predict the distribution of depths within a reach.

Predicting species distribution and abundance responses to climate change: why it is essential to include biotic interactions across trophic levels.

Science.gov (United States)

Van der Putten, Wim H; Macel, Mirka; Visser, Marcel E

2010-07-12

Current predictions on species responses to climate change strongly rely on projecting altered environmental conditions on species distributions. However, it is increasingly acknowledged that climate change also influences species interactions. We review and synthesize literature information on biotic interactions and use it to argue that the abundance of species and the direction of selection during climate change vary depending on how their trophic interactions become disrupted. Plant abundance can be controlled by aboveground and belowground multitrophic level interactions with herbivores, pathogens, symbionts and their enemies. We discuss how these interactions may alter during climate change and the resulting species range shifts. We suggest conceptual analogies between species responses to climate warming and exotic species introduced in new ranges. There are also important differences: the herbivores, pathogens and mutualistic symbionts of range-expanding species and their enemies may co-migrate, and the continuous gene flow under climate warming can make adaptation in the expansion zone of range expanders different from that of cross-continental exotic species. We conclude that under climate change, results of altered species interactions may vary, ranging from species becoming rare to disproportionately abundant. Taking these possibilities into account will provide a new perspective on predicting species distribution under climate change.

Application of General Circulation Models to Assess the Potential Impact of Climate Change on Potential Distribution and Relative Abundance of Melanoplus sanguinipes (Fabricius (Orthoptera: Acrididae in North America

Directory of Open Access Journals (Sweden)

O. Olfert

2011-01-01

Full Text Available Climate is the dominant factor determining the distribution and abundance of most insect species. In recent years, the issue of climatic changes caused by human activities and the effects on agriculture has raised concern. General circulation model scenarios were applied to a bioclimatic model of Melanoplus sanguinipes to assess the potential impact of global warming on its distribution and relative abundance. Native to North America and widely distributed, M. sanguinipes is one of the grasshopper species of the continent most responsible for economic damage to grain, oilseed, pulse, and forage crops. Compared to predicted range and distribution under current climate conditions, model results indicated that M. sanguinipes would have increased range and relative abundance under the three general circulation model scenarios in more northern regions of North America. Conversely, model output predicted that the range of this crop pest could contract in regions where climate conditions became limiting.

Development of a multi-layer ion chamber for measurement of depth dose distributions of heavy-ion therapeutic beam for individual patients

International Nuclear Information System (INIS)

Shimbo, Munefumi; Futami, Yasuyuki; Yusa, Ken; Matsufuji, Naruhiro; Kanai, Tatsuaki; Urakabe, Eriko; Yamashita, Haruo; Akagi, Takashi; Higashi, Akio

2000-01-01

In heavy-ion radiotherapy, an accelerated beam is modified to realize a desired dose distribution in patients. The set-up of the beam-modifying devices in the irradiation system is changed according to the patient, and it is important to check the depth dose distributions in the patient. In order to measure dose distributions realized by an irradiation system for heavy-ion radiotherapy, a multi-layer ionization chamber (MLIC) was developed. The MLIC consists of 64 ionization chambers, which are stacked mutually. The interval between each ionization chamber is about 4.1 mm water. There are signal and high voltage plates in the MLIC, which are used as electrodes of the ionization chambers and phantom. Depth dose distribution from 5.09 mm to 261.92 mm water can be measured in about 30 seconds using this MLIC. Thus, it is possible to check beam quality in a short amount of time. (author)

Unexpectedly higher metazoan meiofauna abundances in the Kuril-Kamchatka Trench compared to the adjacent abyssal plains

Science.gov (United States)

Schmidt, Christina; Martínez Arbizu, Pedro

2015-01-01

We studied meiofauna standing stocks and community structure in the Kuril-Kamchatka Trench and its adjacent abyssal plains in the northwestern Pacific Ocean. In general, the Nematoda were dominant (93%) followed by the Copepoda (4%). Nematode abundances ranged from 87% to 96%; those of copepods from 2% to 7%. The most diverse deployment yielded 17 taxa: Acari, Amphipoda, Annelida, Bivalvia, Coelenterata, Copepoda, Cumacea, Gastrotricha, Isopoda, Kinorhyncha, Loricifera, Nematoda, Ostracoda, Priapulida, Tanaidacea, Tantulocarida, and Tardigrada. Nauplii were also present. Generally, the trench slope and the southernmost deployments had the highest abundances (850-1392 individuals/cm2). The results of non-metric multidimensional scaling indicated that these deployments were similar to each other in meiofauna community structure. The southernmost deployments were located in a zone of higher particulate organic carbon (POC) flux (g Corg m-2 yr-1), whereas the trench slope should have low POC flux due to depth attenuation. Also, POC and abundance were significantly correlated in the abyssal plains. This correlation may explain the higher abundances at the southernmost deployments. Lateral transport was also assumed to explain high meiofauna abundances on the trench slope. Abundances were generally higher than expected from model results. ANOSIM revealed significant differences between the trench slope and the northern abyssal plains, between the central abyssal plains and the trench slope, between the trench slope and the southern abyssal plains, between the central and the southern abyssal plains, and between the central and northern deployments. The northern and southern abyssal plains did not differ significantly. In addition, a U-test revealed highly significant differences between the trench-slope and abyssal deployments. The taxa inhabited mostly the upper 0-3 cm of the sediment layer (Nematoda 80-90%; Copepoda 88-100%). The trench-slope and abyssal did not differ

Anthropogenic influence on the distribution, abundance and diversity of sandfly species (Diptera: Phlebotominae: Psychodidae, vectors of cutaneous leishmaniasis in Panama

Directory of Open Access Journals (Sweden)

Anayansi Valderrama

2011-12-01

Full Text Available In Panama, species of the genus Lutzomyia are vectors of American cutaneous leishmaniasis (ACL. There is no recent ecological information that may be used to develop tools for the control of this disease. Thus, the goal of this study was to determine the composition, distribution and diversity of Lutzomyia species that serve as vectors of ACL. Sandfly sampling was conducted in forests, fragmented forests and rural environments, in locations with records of ACL. Lutzomyia gomezi, Lutzomyia panamensis and Lutzomyia trapidoi were the most widely distributed and prevalent species. Analysis of each sampling point showed that the species abundance and diversity were greatest at points located in the fragmented forest landscape. However, when the samples were grouped according to the landscape characteristics of the locations, there was a greater diversity of species in the rural environment locations. The Kruskal Wallis analysis of species abundance found that Lu. gomezi and Lu. trapidoi were associated with fragmented environments, while Lu. panamensis, Lutzomyia olmeca bicolor and Lutzomyia ylephiletor were associated with forested environments. Therefore, we suggest that human activity influences the distribution, composition and diversity of the vector species responsible for leishmaniasis in Panama.

The 14N(d,0)15N nuclear reaction method for nitrogen depth distribution measurements in wheat and barley

International Nuclear Information System (INIS)

Goenczi, L.; Didriksson, R.; Berggren, H.; Sundqvist, B.; Lindh, U.; Awal, M.A.

1980-01-01

The 14 N(d,p 0 ) 15 N reaction has been used to measure nitrogen depth distributions in single grains of wheat and barley. With the beam energy used (6 MeV) a depth of 225 μm was reached. In order to test the applicability of the method for plant breeding purposes we have studied 1000 grains of wheat and grains of barley, which are part of a larger material of about 50 000 grains grown and harvested under controlled biological conditions. The measured nitrogen distributions in wheat show striking correlations with parameters describing the nitrogen level of fertilizer, the time of harvesting, the grain position in a head and the analyzed variety of wheat. Contributions to the spectra from silicon in the hull of barley are demonstrated. Contributions from interfering elements in the aleuron layer in wheat placed a limit of 120 μm to the depth region analyzed. The importance of effects like pileup, heating of the grains by the beam and grain asymmetries were studied in detail. The possibility to use the technique for selection purposes in plant breeding will be discussed. (author)

Padrões de abundância, riqueza e diversidade de moluscos bivalves na plataforma continental ao largo de Ubatuba, São Paulo, Brasil: uma comparação metodológica

Directory of Open Access Journals (Sweden)

Soares-Gomes Abílio

2003-01-01

Full Text Available The diversity and richness patterns of bivalve molluscs were studied on the continental shelf of Ubatuba (23º38'S, 45º14'W and 23º25'S, 44º51'W between 15-120 metres depth. The samples were taken with a rectangular dredge and a beam trawl. The results showed higher values of richness, diversity and evenness for inner shelf (from coast to nearly 50 m depth and greater values of abundance for outer shelf (from 50 to around 120 m depth. This pattern might be due to the higher instability of the inner shelf, which is influenced by the seasonal intrusion of the South Atlantic Central Water (SACW and the occurrence of cold fronts. Sanders' rarefation curves, distribution and abundance curves and DIMO model were used and the results compared. The Qinghong's model proved to be a good tool for summarizes the results of diversity in a such plural account.

Distribution and abundance of West Greenland humpback whales ( Megaptera novaeangliae )

DEFF Research Database (Denmark)

Larsen, Finn; Hammond, P.S.

2004-01-01

Photo-identification surveys of humpback whales Megaptera novaeangliae were conducted at West Greenland during 1988-93, the last 2 years of which were part of the internationally coordinated humpback whale research programme YoNAH, with the primary aim of estimating abundance for the West Greenland...... effort. A total of 670 groups of humpback whales was encountered leading to the identification of 348 individual animals. Three areas of concentration were identified: an area off Nuuk; an area at c. 63degrees30'N; and an area off Frederikshab. Sequential Petersen capture-recapture estimates of abundance...

The effects of coastal development on sponge abundance, diversity, and community composition on Jamaican coral reefs.

Science.gov (United States)

Stubler, Amber D; Duckworth, Alan R; Peterson, Bradley J

2015-07-15

Over the past decade, development along the northern coast of Jamaica has accelerated, resulting in elevated levels of sedimentation on adjacent reefs. To understand the effects of this development on sponge community dynamics, we conducted surveys at three locations with varying degrees of adjacent coastal development to quantify species richness, abundance and diversity at two depths (8-10 m and 15-18 m). Sediment accumulation rate, total suspended solids and other water quality parameters were also quantified. The sponge community at the location with the least coastal development and anthropogenic influence was often significantly different from the other two locations, and exhibited higher sponge abundance, richness, and diversity. Sponge community composition and size distribution were statistically different among locations. This study provides correlative evidence that coastal development affects aspects of sponge community ecology, although the precise mechanisms are still unclear. Copyright © 2015 Elsevier Ltd. All rights reserved.

Inter-epidemic abundance and distribution of potential mosquito vectors for Rift Valley fever virus in Ngorongoro district, Tanzania

Directory of Open Access Journals (Sweden)

Clement N. Mweya

2015-01-01

Full Text Available Background: Rift Valley fever (RVF is a mosquito-borne viral zoonosis that primarily affects ruminants but also has the capacity to infect humans. Objective: To determine the abundance and distribution of mosquito vectors in relation to their potential role in the virus transmission and maintenance in disease epidemic areas of Ngorongoro district in northern Tanzania. Methods: A cross-sectional entomological investigation was carried out before the suspected RVF outbreak in October 2012. Mosquitoes were sampled both outdoors and indoors using the Centre for Disease Control (CDC light traps and Mosquito Magnets baited with attractants. Outdoor traps were placed in proximity with breeding sites and under canopy in banana plantations close to the sleeping places of animals. Results: A total of 1,823 mosquitoes were collected, of which 87% (N=1,588 were Culex pipiens complex, 12% (N=226 Aedes aegypti, and 0.5% (N=9 Anopheles species. About two-thirds (67%; N=1,095 of C. pipiens complex and nearly 100% (N=225 of A. aegypti were trapped outdoors using Mosquito Magnets. All Anopheles species were trapped indoors using CDC light traps. There were variations in abundance of C. pipiens complex and A. aegypti among different ecological and vegetation habitats. Over three quarters (78% of C. pipiens complex and most (85% of the A. aegypti were trapped in banana and maize farms. Both C. pipiens complex and A. aegypti were more abundant in proximity with cattle and in semi-arid thorn bushes and lower Afro-montane. The highest number of mosquitoes was recorded in villages that were most affected during the RVF epidemic of 2007. Of the tested 150 pools of C. pipiens complex and 45 pools of A. aegypti, none was infected with RVF virus. Conclusions: These results provide insights into unique habitat characterisation relating to mosquito abundances and distribution in RVF epidemic-prone areas of Ngorongoro district in northern Tanzania.

A method for exploring the distribution of radioelements at depth using gamma-ray spectrometric data

International Nuclear Information System (INIS)

Li Qingyang

1997-01-01

Based on the inherent relation between radioelements and terrestrial heat flow, theoretically shows the possibility of exploring the distribution of radioelements at depth using gamma-ray spectrometric data, and a data-processing and synthesizing method has been adopted to deduce the calculation formula. The practical application in the uranium mineralized area No. 2801 in Yunnan Province proves that this method is of practical value, and it has been successfully applied to the data processing and good results have been obtained

Some peculiarities of fish abundance, species and sizes distribution, and spacing

International Nuclear Information System (INIS)

Astrauskas, A.; Bernotas, E.; Jovaisha, R.

1995-01-01

During the construction and exploitation process of Ignalina NPP the abundance of fishes has dropped, and especially stenothermic species (smelt and vendace). The general increase of fish abundance is observed in recent years (1992-1994). This is linked with changes of fish species and their adaptation to the new environmental conditions. Now the partial renovation of vendace abundance is observed, too. It is a result of free feeding recess coming out as the smelt dramatically decreased. Before now the ecosystem of the lake is greatly disbalanced due to antropogenetic impact of the NPP. It's partial stabilisation (but on the essentially high level) is possible only in some generations of fish living in the lake. (author). 18 refs., 1 tab., 11 figs

Crystal orientation effects on helium ion depth distributions and adatom formation processes in plasma-facing tungsten

International Nuclear Information System (INIS)

Hammond, Karl D.; Wirth, Brian D.

2014-01-01

We present atomistic simulations that show the effect of surface orientation on helium depth distributions and surface feature formation as a result of low-energy helium plasma exposure. We find a pronounced effect of surface orientation on the initial depth of implanted helium ions, as well as a difference in reflection and helium retention across different surface orientations. Our results indicate that single helium interstitials are sufficient to induce the formation of adatom/substitutional helium pairs under certain highly corrugated tungsten surfaces, such as (1 1 1)-orientations, leading to the formation of a relatively concentrated layer of immobile helium immediately below the surface. The energies involved for helium-induced adatom formation on (1 1 1) and (2 1 1) surfaces are exoergic for even a single adatom very close to the surface, while (0 0 1) and (0 1 1) surfaces require two or even three helium atoms in a cluster before a substitutional helium cluster and adatom will form with reasonable probability. This phenomenon results in much higher initial helium retention during helium plasma exposure to (1 1 1) and (2 1 1) tungsten surfaces than is observed for (0 0 1) or (0 1 1) surfaces and is much higher than can be attributed to differences in the initial depth distributions alone. The layer thus formed may serve as nucleation sites for further bubble formation and growth or as a source of material embrittlement or fatigue, which may have implications for the formation of tungsten “fuzz” in plasma-facing divertors for magnetic-confinement nuclear fusion reactors and/or the lifetime of such divertors.

Depth resolved investigations of boron implanted silicon

Science.gov (United States)

Sztucki, M.; Metzger, T. H.; Milita, S.; Berberich, F.; Schell, N.; Rouvière, J. L.; Patel, J.

2003-01-01

We have studied the depth distribution and structure of defects in boron implanted silicon (0 0 1). Silicon wafers were implanted with a boron dose of 6×10 15 ions/cm -2 at 32 keV and went through different annealing treatments. Using diffuse X-ray scattering at grazing incidence and exit angles we are able to distinguish between different kinds of defects (point defect clusters and extrinsic stacking faults on {1 1 1} planes) and to determine their depth distribution as a function of the thermal budget. Cross-section transmission electron microscopy was used to gain complementary information. In addition we have determined the strain distribution caused by the boron implantation as a function of depth from rocking curve measurements.

Modelling tick abundance using machine learning techniques and satellite imagery

DEFF Research Database (Denmark)

Kjær, Lene Jung; Korslund, L.; Kjelland, V.

satellite images to run Boosted Regression Tree machine learning algorithms to predict overall distribution (presence/absence of ticks) and relative tick abundance of nymphs and larvae in southern Scandinavia. For nymphs, the predicted abundance had a positive correlation with observed abundance...... the predicted distribution of larvae was mostly even throughout Denmark, it was primarily around the coastlines in Norway and Sweden. Abundance was fairly low overall except in some fragmented patches corresponding to forested habitats in the region. Machine learning techniques allow us to predict for larger...... the collected ticks for pathogens and using the same machine learning techniques to develop prevalence maps of the ScandTick region....

THE DISTRIBUTION OF THE ELEMENTS IN THE GALACTIC DISK. II. AZIMUTHAL AND RADIAL VARIATION IN ABUNDANCES FROM CEPHEIDS

International Nuclear Information System (INIS)

Luck, R. E.; Andrievsky, S. M.; Kovtyukh, V. V.; Gieren, W.; Graczyk, D.

2011-01-01

This paper reports on the spectroscopic investigation of 101 Cepheids in the Carina region. These Cepheids extend previous samples by about 35% in number and increase the amount of the Galactic disk coverage especially in the direction of l ∼ 270 0 . The new Cepheids do not add much information to the radial gradient, but provide a substantial increase in azimuthal coverage. We find no azimuthal dependence in abundance over an 80 deg. angle from the Galactic center in an annulus of 1 kpc depth centered on the Sun. A simple linear fit to the Cepheid data yields a gradient d[Fe/H]/dR G = -0.055 ± 0.003 dex kpc -1 which is somewhat shallower than found from our previous, smaller Cepheid sample.

Modeling the winter-to-summer transition of prokaryotic and viral abundance in the Arctic Ocean.

Science.gov (United States)

Winter, Christian; Payet, Jérôme P; Suttle, Curtis A

2012-01-01

One of the challenges in oceanography is to understand the influence of environmental factors on the abundances of prokaryotes and viruses. Generally, conventional statistical methods resolve trends well, but more complex relationships are difficult to explore. In such cases, Artificial Neural Networks (ANNs) offer an alternative way for data analysis. Here, we developed ANN-based models of prokaryotic and viral abundances in the Arctic Ocean. The models were used to identify the best predictors for prokaryotic and viral abundances including cytometrically-distinguishable populations of prokaryotes (high and low nucleic acid cells) and viruses (high- and low-fluorescent viruses) among salinity, temperature, depth, day length, and the concentration of Chlorophyll-a. The best performing ANNs to model the abundances of high and low nucleic acid cells used temperature and Chl-a as input parameters, while the abundances of high- and low-fluorescent viruses used depth, Chl-a, and day length as input parameters. Decreasing viral abundance with increasing depth and decreasing system productivity was captured well by the ANNs. Despite identifying the same predictors for the two populations of prokaryotes and viruses, respectively, the structure of the best performing ANNs differed between high and low nucleic acid cells and between high- and low-fluorescent viruses. Also, the two prokaryotic and viral groups responded differently to changes in the predictor parameters; hence, the cytometric distinction between these populations is ecologically relevant. The models imply that temperature is the main factor explaining most of the variation in the abundances of high nucleic acid cells and total prokaryotes and that the mechanisms governing the reaction to changes in the environment are distinctly different among the prokaryotic and viral populations.

Modeling the Winter–to–Summer Transition of Prokaryotic and Viral Abundance in the Arctic Ocean

Science.gov (United States)

Winter, Christian; Payet, Jérôme P.; Suttle, Curtis A.

2012-01-01

One of the challenges in oceanography is to understand the influence of environmental factors on the abundances of prokaryotes and viruses. Generally, conventional statistical methods resolve trends well, but more complex relationships are difficult to explore. In such cases, Artificial Neural Networks (ANNs) offer an alternative way for data analysis. Here, we developed ANN-based models of prokaryotic and viral abundances in the Arctic Ocean. The models were used to identify the best predictors for prokaryotic and viral abundances including cytometrically-distinguishable populations of prokaryotes (high and low nucleic acid cells) and viruses (high- and low-fluorescent viruses) among salinity, temperature, depth, day length, and the concentration of Chlorophyll-a. The best performing ANNs to model the abundances of high and low nucleic acid cells used temperature and Chl-a as input parameters, while the abundances of high- and low-fluorescent viruses used depth, Chl-a, and day length as input parameters. Decreasing viral abundance with increasing depth and decreasing system productivity was captured well by the ANNs. Despite identifying the same predictors for the two populations of prokaryotes and viruses, respectively, the structure of the best performing ANNs differed between high and low nucleic acid cells and between high- and low-fluorescent viruses. Also, the two prokaryotic and viral groups responded differently to changes in the predictor parameters; hence, the cytometric distinction between these populations is ecologically relevant. The models imply that temperature is the main factor explaining most of the variation in the abundances of high nucleic acid cells and total prokaryotes and that the mechanisms governing the reaction to changes in the environment are distinctly different among the prokaryotic and viral populations. PMID:23285186

Abundance and distribution of archaeal acetyl-CoA/propionyl-CoA carboxylase genes indicative for putatively chemoautotrophic Archaea in the tropical Atlantic's interior.

Science.gov (United States)

Bergauer, Kristin; Sintes, Eva; van Bleijswijk, Judith; Witte, Harry; Herndl, Gerhard J

2013-06-01

Recently, evidence suggests that dark CO2 fixation in the pelagic realm of the ocean does not only occur in the suboxic and anoxic water bodies but also in the oxygenated meso- and bathypelagic waters of the North Atlantic. To elucidate the significance and phylogeny of the key organisms mediating dark CO2 fixation in the tropical Atlantic, we quantified functional genes indicative for CO2 fixation. We used a Q-PCR-based assay targeting the bifunctional acetyl-CoA/propionyl-CoA carboxylase (accA subunit), a key enzyme powering inter alia the 3-hydroxypropionate/4-hydroxybutyrate cycle (HP/HB) and the archaeal ammonia monooxygenase (amoA). Quantification of accA-like genes revealed a consistent depth profile in the upper mesopelagial with increasing gene abundances from subsurface layers towards the oxygen minimum zone (OMZ), coinciding with an increase in archaeal amoA gene abundance. Gene abundance profiles of metabolic marker genes (accA, amoA) were correlated with thaumarchaeal 16S rRNA gene abundances as well as CO2 fixation rates to link the genetic potential to actual rate measurements. AccA gene abundances correlated with archaeal amoA gene abundance throughout the water column (r(2)  = 0.309, P < 0.0001). Overall, a substantial genetic predisposition of CO2 fixation was present in the dark realm of the tropical Atlantic in both Archaea and Bacteria. Hence, dark ocean CO2 fixation might be more widespread among prokaryotes inhabiting the oxygenated water column of the ocean's interior than hitherto assumed. © 2013 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Unusual algal turfs associated with the rhodophyta Phyllophora crispa: Benthic assemblages along a depth gradient in the Central Mediterranean Sea

Science.gov (United States)

Bonifazi, Andrea; Ventura, Daniele; Gravina, Maria Flavia; Lasinio, Giovanna Jona; Belluscio, Andrea; Ardizzone, Gian Domenico

2017-02-01

Macroalgal assemblages dominated by the turf-forming alga Phyllophora crispa are described in detail for the first time in the Central Mediterranean Sea. This particular form of algal growth, which comprises an upper mixed layer of multiple algal species with a basal stratum formed by entangled thalli of P. crispa, was observed for the first time in 2012 along the promontory of Punta del Lazzaretto (Giglio Island, Italy). In this study, this assemblage was analysed to document the diversity of macroalgae and invertebrate associated communities and assess their distribution along a depth gradient. The algae forming turfs grow directly on the rock at low depth up to 10-15 m depth, while they grow above P. crispa from 15 m to 35 m depth, resulting in luxuriant beds covering up to 100% of the substrate. Multivariate analysis revealed clear differences regarding algae and invertebrate species richness and abundance between shallow and deep strata because of the dominance of Phyllophora crispa at depths greater than 20 m. The long laminal thalli of P. crispa favoured sessile fauna colonization, while the vagile species were principally linked to the architectural complexity of the turf layer created by the P. crispa, which increased the microhabitat diversity and favoured sediment deposition within the turf layer. The complex structures of these turf assemblages and their widespread distribution along the whole coast of the island suggest a well-established condition of the communities linked to the high natural sedimentation rate observed in the area.

Epiphytic flora on Gelidium corneum (Rhodophyta: Gelidiales in relation to wave exposure and depth

Directory of Open Access Journals (Sweden)

Endika Quintano

2015-12-01

Full Text Available The canopy-forming macroalga Gelidium corneum (Hudson J.V. Lamouroux plays a major role in the functioning of the subtidal ecosystem of the Cantabrian Sea (northern Spain. Despite its importance, little is known about the factors that may potentially affect the distribution pattern of its epiphytic flora. Here we examine two indirect factors: coastal orientation (N and NW and depth (3 and 7 m, as proxies for wave exposure and light availability, respectively. We test their effects on the total epiphytic load, alpha diversity (species richness, Shannon, Simpson and evenness measures and multivariate structure of the epiphytic flora growing on G. corneum in subtidal waters off the Basque coast. Plocamium cartilagineum, Dictyota dichotoma and Acrosorium ciliolatum were found to be the most common epiphytes. Significant interactive effect of coastal orientation and depth were observed for species composition and abundance of epiphytic flora. Increased wave exposure resulted in a lower epiphyte load and a less diverse community, suggesting that under high hydrodynamic conditions epiphytes were more likely to become dislodged from hosts. However, light availability only had a significant effect on the distribution of epiphytes below a certain threshold of wave action, with the epiphytic load being 30-40% greater on shallow bottoms.

Regional Distribution Shifts Help Explain Local Changes in Wintering Raptor Abundance: Implications for Interpreting Population Trends

Science.gov (United States)

Paprocki, Neil; Heath, Julie A.; Novak, Stephen J.

2014-01-01

Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas Bird Counts from 1975–2011. Also, we considered whether population indices within western North America Bird Conservation Regions (BCRs) were explained by distribution shifts. All six raptors had significant poleward shifts in their wintering distributions over time. Rough-legged Hawks (Buteo lagopus) and Golden Eagles (Aquila chrysaetos) showed the fastest rate of change, with 8.41 km yr−1 and 7.74 km yr−1 shifts, respectively. Raptors may be particularly responsive to warming winters because of variable migration tendencies, intraspecific competition for nesting sites that drives males to winter farther north, or both. Overall, 40% of BCR population trend models were improved by incorporating information about wintering distributions; however, support for the effect of distribution on BCR indices varied by species with Rough-legged Hawks showing the most evidence. These results emphasize the importance of understanding how regional distribution shifts influence local-scale population indices. If global climate change is altering distribution patterns, then trends within some management units may not reflect changes in local habitat conditions. The methods used to monitor and manage bird populations within local BCRs will fundamentally change as

Regional distribution shifts help explain local changes in wintering raptor abundance: implications for interpreting population trends.

Directory of Open Access Journals (Sweden)

Neil Paprocki

Full Text Available Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas Bird Counts from 1975-2011. Also, we considered whether population indices within western North America Bird Conservation Regions (BCRs were explained by distribution shifts. All six raptors had significant poleward shifts in their wintering distributions over time. Rough-legged Hawks (Buteo lagopus and Golden Eagles (Aquila chrysaetos showed the fastest rate of change, with 8.41 km yr(-1 and 7.74 km yr(-1 shifts, respectively. Raptors may be particularly responsive to warming winters because of variable migration tendencies, intraspecific competition for nesting sites that drives males to winter farther north, or both. Overall, 40% of BCR population trend models were improved by incorporating information about wintering distributions; however, support for the effect of distribution on BCR indices varied by species with Rough-legged Hawks showing the most evidence. These results emphasize the importance of understanding how regional distribution shifts influence local-scale population indices. If global climate change is altering distribution patterns, then trends within some management units may not reflect changes in local habitat conditions. The methods used to monitor and manage bird populations within local BCRs will fundamentally

Corrosion pit depth extreme value prediction from limited inspection data

International Nuclear Information System (INIS)

Najjar, D.; Bigerelle, M.; Iost, A.; Bourdeau, L.; Guillou, D.

2004-01-01

Passive alloys like stainless steels are prone to localized corrosion in chlorides containing environments. The greater the depth of the localized corrosion phenomenon, the more dramatic the related damage that can lead to a structure weakening by fast perforation. In practical situations, because measurements are time consuming and expensive, the challenge is usually to predict the maximum pit depth that could be found in a large scale installation from the processing of a limited inspection data. As far as the parent distribution of pit depths is assumed to be of exponential type, the most successful method was found in the application of the statistical extreme-value analysis developed by Gumbel. This study aims to present a new and alternative methodology to the Gumbel approach with a view towards accurately estimating the maximum pit depth observed on a ferritic stainless steel AISI 409 subjected to an accelerated corrosion test (ECC1) used in automotive industry. This methodology consists in characterising and modelling both the morphology of pits and the statistical distribution of their depths from a limited inspection dataset. The heart of the data processing is based on the combination of two recent statistical methods that avoid making any choice about the type of the theoretical underlying parent distribution of pit depths: the Generalized Lambda Distribution (GLD) is used to model the distribution of pit depths and the Bootstrap technique to determine a confidence interval on the maximum pit depth. (authors)

Determination of the thickness distribution of a graphene layer grown on a 2″ SiC wafer by means of Auger electron spectroscopy depth profiling

International Nuclear Information System (INIS)

Kotis, L.; Gurban, S.; Pecz, B.; Menyhard, M.; Yakimova, R.

2014-01-01

Highlights: • The thickness of graphene grown on SiC was determined by AES depth profiling. • The AES depth profiling verified the presence of buffer layer on SiC. • The presence of unsaturated Si bonds in the buffer layer has been shown. • Using multipoint analysis thickness distribution of the graphene on the wafer was determined. - Abstract: Auger electron spectroscopy (AES) depth profiling was applied for determination of the thickness of a macroscopic size graphene sheet grown on 2 in. 6H-SiC (0 0 0 1) by sublimation epitaxy. The measured depth profile deviated from the expected exponential form showing the presence of an additional, buffer layer. The measured depth profile was compared to the simulated one which allowed the derivation of the thicknesses of the graphene and buffer layers and the Si concentration of buffer layer. It has been shown that the graphene-like buffer layer contains about 30% unsaturated Si. The depth profiling was carried out in several points (diameter 50 μm), which permitted the constructing of a thickness distribution characterizing the uniformity of the graphene sheet

Distribution and abundance of key vectors of Rift Valley fever and other arboviruses in two ecologically distinct counties in Kenya.

Directory of Open Access Journals (Sweden)

Rosemary Sang

2017-02-01

Full Text Available Rift Valley fever (RVF is a mosquito-borne viral zoonosis of ruminants and humans that causes outbreaks in Africa and the Arabian Peninsula with significant public health and economic consequences. Humans become infected through mosquito bites and contact with infected livestock. The virus is maintained between outbreaks through vertically infected eggs of the primary vectors of Aedes species which emerge following rains with extensive flooding. Infected female mosquitoes initiate transmission among nearby animals, which amplifies virus, thereby infecting more mosquitoes and moving the virus beyond the initial point of emergence. With each successive outbreak, RVF has been found to expand its geographic distribution to new areas, possibly driven by available vectors. The aim of the present study was to determine if RVF virus (RVFV transmission risk in two different ecological zones in Kenya could be assessed by looking at the species composition, abundance and distribution of key primary and secondary vector species and the level of virus activity.Mosquitoes were trapped during short and long rainy seasons in 2014 and 2015 using CO2 baited CDC light traps in two counties which differ in RVF epidemic risk levels(high risk Tana-River and low risk Isiolo,cryo-preserved in liquid nitrogen, transported to the laboratory, and identified to species. Mosquito pools were analyzed for virus infection using cell culture screening and molecular analysis.Over 69,000 mosquitoes were sampled and identified as 40 different species belonging to 6 genera (Aedes, Anopheles, Mansonia, Culex, Aedeomyia, Coquillettidia. The presence and abundance of Aedes mcintoshi and Aedes ochraceus, the primary mosquito vectors associated with RVFV transmission in outbreaks, varied significantly between Tana-River and Isiolo. Ae. mcintoshi was abundant in Tana-River and Isiolo but notably, Aedes ochraceus found in relatively high numbers in Tana-River (n = 1,290, was totally

Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

Science.gov (United States)

Li, Chenyu; Peng, Zhigang; Yao, Dongdong; Guo, Hao; Zhan, Zhongwen; Zhang, Haijiang

2018-05-01

The 2015 Mw7.5 Hindu Kush earthquake occurred at a depth of 213 km beneath the Hindu Kush region of Afghanistan. While many early aftershocks were missing from the global earthquake catalogues, this sequence was recorded continuously by eight broad-band stations within 500 km. Here we use a waveform matching technique to systematically detect earthquakes around the main shock. More than 3000 events are detected within 35 d after the main shock, as compared with 42 listed in the Advanced National Seismic System catalogue (or 196 in the International Seismological Centre catalogue). The aftershock sequence generally follows the Omori's law with a decay constant p = 0.92. We also apply the recently developed double-pair double-difference technique to relocate all detected aftershocks. Most of them are located to the west of the hypocentre of the main shock, consistent with the westward propagation of the main-shock rupture. The aftershocks outline a nearly vertical southward dipping plane, which matches well with one of the nodal planes of the main shock. We conclude that the aftershock sequence of this intermediate-depth earthquake shares many similarities with those for shallow earthquakes and infer that there are some common mechanisms responsible for shallow and intermediate-depth earthquakes.

Diversity and Spatial Distribution of Extant Freshwater Ostracodes (Crustacea in Ancient Lake Ohrid (Macedonia/Albania

Directory of Open Access Journals (Sweden)

Julia Lorenschat

2014-07-01

Full Text Available We carried out an intensive sampling survey in ancient Lake Ohrid (Macedonia/Albania, covering all seasons, to determine total species number, relative species abundances and spatial distribution of Ostracoda. We identified 32 living species that belong to seven families (Candonidae, Ilyocyprididae, Cyprididae, Leptocytheridae, Limnocytheridae, Cytherideidae, and Darwinulidae and 15 genera (Candona, Fabaeformiscandona, Candonopsis, Cypria, Cyclocypris, Ilyocypris, Eucypris, Prionocypris, Bradleystrandesia, Herpetocypris, Dolerocypris, Amnicythere, Paralimnocythere, Cytherissa, and Darwinula. Six additional species were identified from empty carapaces and valves. Dominant families in Lake Ohrid were Candonidae and Limnocytheridae, representing 53% and 16% of all species, respectively. Prevalence of species flocks in these two families confirms the “young” ancient status of the lake. Amnicythere displays a preference for oligo-haline to meso-haline waters, but some species are found in saline environments, which suggests Lake Ohrid has a marine history. Recent studies, however, indicate fluvial/glaciofluvial deposition at the onset of Lake Ohrid sedimentation. Candona is the most diverse genus in Lake Ohrid, represented by 12 living species. Paralimnocythere is represented by five living species and all other genera are represented by one or two species. Reports of Candona bimucronata, Ilyocypris bradyi, Eucypris virens, Eucypris sp., Prionocypris zenkeri, Bradleystrandesia reticulate, Herpetocypris sp. 2, and Dolerocypris sinensis are firsts for this lake. Living ostracodes were collected at the maximum water depth (280 m in the lake (Candona hadzistei, C. marginatoides, C. media, C. ovalis, C. vidua, Fabaeformiscandona krstici, Cypria lacustris, C. obliqua and Amnicythere karamani. Cypria lacustris was overall the most abundant species and Cypria obliqua displayed the highest abundance at 280 m water depth. Principal environmental variables

Inter-epidemic abundance and distribution of potential mosquito vectors for Rift Valley fever virus in Ngorongoro district, Tanzania

OpenAIRE

Mweya, Clement N.; Kimera, Sharadhuli I.; Mellau, Lesakit S. B.; Mboera, Leonard E. G.

2015-01-01

Background: Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that primarily affects ruminants but also has the capacity to infect humans. Objective: To determine the abundance and distribution of mosquito vectors in relation to their potential role in the virus transmission and maintenance in disease epidemic areas of Ngorongoro district in northern Tanzania. Methods: A cross-sectional entomological investigation was carried out before the suspected RVF outbreak in October 2012. Mos...

Abundances of Demersal Sharks and Chimaera from 1994-2009 Scientific Surveys in the Central Mediterranean Sea

Science.gov (United States)

Ragonese, Sergio; Vitale, Sergio; Dimech, Mark; Mazzola, Salvatore

2013-01-01

Bibliographic and data gathered in scientific bottom trawl surveys carried out off the Southern Coasts of Sicily (Mediterranean Sea), from 1994 to 2009 and between a depth of 10 and 800 m, were analysed in order to prepare a checklist of demersal sharks and chimaera, which are species sensitive to fisheries exploitation. Out of the 27 previously reported demersal shark and chimaera taxa in the Mediterranean, only 23 were found in literature and 20 sampled during the surveys in the investigated area. Among the species sampled in the surveys, only 2 ubiquitous ( Squalus blainville and Scyliorhinus canicula ) and 3 deep-water ( Chimaera monstrosa , Centrophorus granulosus and Galeus melastomus ) species showed a wide geographical distribution with a consistent abundance. Excluding the rare (such as Oxynotus centrina ) or uncommon shark (e.g. Squalus acanthias ), the estimated frequencies of occurrence and abundance indexes show a possible risk of local extinction for the almost exclusively (e.g. angelshark, Squatina spp.) or preferential (e.g. Scyliorhinus stellaris ) neritic species. PMID:24086386

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 ...

Microbial Distribution and Abundance in the Digestive System of Five Shipworm Species (Bivalvia: Teredinidae)

Science.gov (United States)

Betcher, Meghan A.; Fung, Jennifer M.; Han, Andrew W.; O’Connor, Roberta; Seronay, Romell; Concepcion, Gisela P.; Distel, Daniel L.; Haygood, Margo G.

2012-01-01

Marine bivalves of the family Teredinidae (shipworms) are voracious consumers of wood in marine environments. In several shipworm species, dense communities of intracellular bacterial endosymbionts have been observed within specialized cells (bacteriocytes) of the gills (ctenidia). These bacteria are proposed to contribute to digestion of wood by the host. While the microbes of shipworm gills have been studied extensively in several species, the abundance and distribution of microbes in the digestive system have not been adequately addressed. Here we use Fluorescence In-Situ Hybridization (FISH) and laser scanning confocal microscopy with 16S rRNA directed oligonucleotide probes targeting all domains, domains Bacteria and Archaea, and other taxonomic groups to examine the digestive microbiota of 17 specimens from 5 shipworm species (Bankia setacea, Lyrodus pedicellatus, Lyrodus massa, Lyrodus sp. and Teredo aff. triangularis). These data reveal that the caecum, a large sac-like appendage of the stomach that typically contains large quantities of wood particles and is considered the primary site of wood digestion, harbors only very sparse microbial populations. However, a significant number of bacterial cells were observed in fecal pellets within the intestines. These results suggest that due to low abundance, bacteria in the caecum may contribute little to lignocellulose degradation. In contrast, the comparatively high population density of bacteria in the intestine suggests a possible role for intestinal bacteria in the degradation of lignocellulose. PMID:23028923

Magnetotelluric inversion for depth-to-basement estimation

DEFF Research Database (Denmark)

Cai, Hongzhu; Zhdanov, Michael

2015-01-01

The magnetotelluric (MT) method can be effectively applied for depth-to-basement estimation, because there exists a strong contrast in resistivity between a conductive sedimentary basin and a resistive crystalline basement. Conventional inversions of MT data are usually aimed at determining...... the volumetric distribution of the conductivity within the inversion domain. By the nature of the MT method, the recovered distribution of the subsurface conductivity is typically diffusive, which makes it difficult to select the sediment-basement interface. This paper develops a novel approach to 3D MT...... inversion for the depth-to-basement estimate. The key to this approach is selection of the model parameterization with the depth to basement being the major unknown parameter. In order to estimate the depth to the basement, the inversion algorithm recovers both the thickness and the conductivities...

Distribution and seasonal abundance of large cetaceans in the ...

African Journals Online (AJOL)

Killer whale Orcinus orca presence was coincident with that of offshore minke whales and the southward migrations of other baleen whales, whereas densities of animals deemed as bottlenose whale Hyperoodon planifrons suggest strong early and late summer seasonal abundance in the offshore region. Such extensive ...

Determination of distribution function of refraction index and anion diffusion depth in porous alumina photonic crystals

Directory of Open Access Journals (Sweden)

H. Kaviani

2007-09-01

Full Text Available   Band structure of porous alumina photonic crystal in the Γ X direction was calculated using order-N method . In a comparison of calculated results with experimental data of reflective and absorptive index, the variation of refractive index of alumina in the external region of oxide layer, around the pores were studied. A Gaussian distribution function was adopted for phosphate anions in the external oxide layer and the variation of refractive index and diffusion depth were determined. The structure of the first four bands was calculated using the obtained distribution of refractive index in the external oxide layer for both TE and TM mode. This results show a narrow full band gap in the TM mode.

Combining counts and incidence data: an efficient approach for estimating the log-normal species abundance distribution and diversity indices.

Science.gov (United States)

Bellier, Edwige; Grøtan, Vidar; Engen, Steinar; Schartau, Ann Kristin; Diserud, Ola H; Finstad, Anders G

2012-10-01

Obtaining accurate estimates of diversity indices is difficult because the number of species encountered in a sample increases with sampling intensity. We introduce a novel method that requires that the presence of species in a sample to be assessed while the counts of the number of individuals per species are only required for just a small part of the sample. To account for species included as incidence data in the species abundance distribution, we modify the likelihood function of the classical Poisson log-normal distribution. Using simulated community assemblages, we contrast diversity estimates based on a community sample, a subsample randomly extracted from the community sample, and a mixture sample where incidence data are added to a subsample. We show that the mixture sampling approach provides more accurate estimates than the subsample and at little extra cost. Diversity indices estimated from a freshwater zooplankton community sampled using the mixture approach show the same pattern of results as the simulation study. Our method efficiently increases the accuracy of diversity estimates and comprehension of the left tail of the species abundance distribution. We show how to choose the scale of sample size needed for a compromise between information gained, accuracy of the estimates and cost expended when assessing biological diversity. The sample size estimates are obtained from key community characteristics, such as the expected number of species in the community, the expected number of individuals in a sample and the evenness of the community.

BORON ABUNDANCES ACROSS THE “Li–Be DIP” IN THE HYADES CLUSTER

Energy Technology Data Exchange (ETDEWEB)

Boesgaard, Ann Merchant; Lum, Michael G. [Institute for Astronomy, University of Hawai‘i at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Deliyannis, Constantine P. [Department of Astronomy, Indiana University, 727 East 3rd Street, Swain Hall West 319, Bloomington, IN 47405-7105 (United States); King, Jeremy R. [Department of Physics and Astronomy, Clemson University, 118 Kinard Laboratory of Physics, Clemson, SC 29634-0978 (United States); Pinsonneault, Marc H.; Somers, Garrett, E-mail: boes@ifa.hawaii.edu, E-mail: mikelum@ifa.hawaii.edu, E-mail: cdeliyan@indiana.edu, E-mail: jking2@clemson.edu, E-mail: pinsonneault.1@osu.edu, E-mail: somers@astronomy.ohio-state.edu [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

2016-10-10

Dramatic deficiencies of Li in the mid-F dwarf stars of the Hyades cluster were discovered by Boesgaard and Tripicco. Boesgaard and King discovered corresponding, but smaller, deficiencies in Be in the same narrow temperature region in the Hyades. Using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope , we investigate B abundances in the Hyades F stars to look for a potential B dip using the B i resonance line at 2496.8 Å. The light elements Li, Be, and B are destroyed inside stars at increasingly hotter temperatures: 2.5, 3.5, and 5 × 10{sup 6} K, respectively. Consequently, these elements survive to increasingly greater depths in a star and their surface abundances indicate the depth and thoroughness of mixing in the star. We have (re)determined Li abundances/upper limits for 79 Hyades dwarfs, Be for 43 stars, and B for 5 stars. We find evidence for a small drop in the B abundance across the Li–Be dip. The B abundances for the four stars in the temperature range 6100–6730 K fit the B–Be correlation found previously by Boesgaard et al. Models of rotational mixing produce good agreement with the relative depletions of Be and B in the dip region. We have compared our nLTE B abundances for the three high B stars on either side of the Li–Be dip with those found by Duncan et al. for the two Hyades giants. This confirms the factor of 10 decline in the B abundance in the Hyades giants as predicted by dilution due to the deepening of the surface convection zone.

Neutral theory and the species abundance distribution: recent developments and prospects for unifying niche and neutral perspectives

Science.gov (United States)

Matthews, Thomas J; Whittaker, Robert J

2014-01-01

Published in 2001, The Unified Neutral Theory of Biodiversity and Biogeography (UNTB) emphasizes the importance of stochastic processes in ecological community structure, and has challenged the traditional niche-based view of ecology. While neutral models have since been applied to a broad range of ecological and macroecological phenomena, the majority of research relating to neutral theory has focused exclusively on the species abundance distribution (SAD). Here, we synthesize the large body of work on neutral theory in the context of the species abundance distribution, with a particular focus on integrating ideas from neutral theory with traditional niche theory. First, we summarize the basic tenets of neutral theory; both in general and in the context of SADs. Second, we explore the issues associated with neutral theory and the SAD, such as complications with fitting and model comparison, the underlying assumptions of neutral models, and the difficultly of linking pattern to process. Third, we highlight the advances in understanding of SADs that have resulted from neutral theory and models. Finally, we focus consideration on recent developments aimed at unifying neutral- and niche-based approaches to ecology, with a particular emphasis on what this means for SAD theory, embracing, for instance, ideas of emergent neutrality and stochastic niche theory. We put forward the argument that the prospect of the unification of niche and neutral perspectives represents one of the most promising future avenues of neutral theory research. PMID:25360266

Neutral theory and the species abundance distribution: recent developments and prospects for unifying niche and neutral perspectives.

Science.gov (United States)

Matthews, Thomas J; Whittaker, Robert J

2014-06-01

Published in 2001, The Unified Neutral Theory of Biodiversity and Biogeography (UNTB) emphasizes the importance of stochastic processes in ecological community structure, and has challenged the traditional niche-based view of ecology. While neutral models have since been applied to a broad range of ecological and macroecological phenomena, the majority of research relating to neutral theory has focused exclusively on the species abundance distribution (SAD). Here, we synthesize the large body of work on neutral theory in the context of the species abundance distribution, with a particular focus on integrating ideas from neutral theory with traditional niche theory. First, we summarize the basic tenets of neutral theory; both in general and in the context of SADs. Second, we explore the issues associated with neutral theory and the SAD, such as complications with fitting and model comparison, the underlying assumptions of neutral models, and the difficultly of linking pattern to process. Third, we highlight the advances in understanding of SADs that have resulted from neutral theory and models. Finally, we focus consideration on recent developments aimed at unifying neutral- and niche-based approaches to ecology, with a particular emphasis on what this means for SAD theory, embracing, for instance, ideas of emergent neutrality and stochastic niche theory. We put forward the argument that the prospect of the unification of niche and neutral perspectives represents one of the most promising future avenues of neutral theory research.

The distribution and abundance of Sphaeroma terebrans, a wood-boring isopod of red mangrove (Rhizophora mangle) habitat within Tampa Bay

Science.gov (United States)

Brooks, R.A.; Bell, S.S.

2005-01-01

This study was conducted to determine the distribution, abundance, and demography of a wood boring isopod, Sphaeroma terebrans Bate, 1866, within the prop roots of the red mangrove, Rhizophora mangle L., in eight sites within Tampa Bay, Florida. Sphaeroma terebrans in Tampa Bay displayed reproductive activity year-round and bay-wide synchrony in their density pattern. On average approximately 60% (range: 25%-86%) of the intertidal aerial roots surveyed were occupied by S. terebrans. Although infestation levels by S. terebrans in Tampa Bay were similar to that of more tropical regions, the distribution of S. terebrans was not continuous throughout the study sites. A substantially higher occurrence and density of S. terebrans was found in the northern compared to more southern study sites within the Bay. Additionally, some seemingly suitable areas of the bay (i.e., Pinellas Point, Skyway, Fort Desoto) were actually unoccupied on some dates. Although sites differed in the frequency with which roots were attacked, the density of burrows and isopods in an occupied root was similar, with most attacked roots containing 3-5 burrows. The results of a transplantation experiment indicated that neither abiotic factors nor substrate quality limit the burrowing capabilities or survival of adult S. terebrans in the areas where they are absent. Instead, dispersal limitation, linked with differential juvenile survival, most likely controls isopod distribution and abundance within Tampa Bay.

The distribution, relative abundance, and seasonal phenology of Ceratitis capitata, Ceratitis rosa, and Ceratitis cosyra (Diptera: Tephritidae) in South Africa.

Science.gov (United States)

De Villiers, Marelize; Manrakhan, Aruna; Addison, Pia; Hattingh, Vaughan

2013-10-01

Ceratitis capitata (Wiedemann), Ceratitis rosa Karsch, and Ceratitis cosyra (Walker) are fruit fly species (Diptera: Tephritidae) of economic importance in South Africa. These pests cause direct damage to a number of commercially produced fruit and are of phytosanitary concern. A study was conducted to determine the distribution, relative abundance, and seasonal occurrence of the three species in different climatic regions of South Africa. The relative abundance and seasonal phenology of C. capitata and C. rosa were also compared between production areas and home gardens in Stellenbosch, Western Cape. Yellow bucket traps baited with Biolure were used to trap the flies over a 2-yr period in the different sampling areas. Different fruit types were sampled in Stellenbosch to determine fruit fly infestation. C. capitata was found to have a widespread distribution in South Africa, whereas C. rosa were absent from or only present in low numbers in the drier regions. C. cosyra was restricted to the North East and East coast, following a similar pattern to the distribution of marula, Sclerocarrya birrea, an important wild host. Fruit in home gardens provided a breeding ground for C. capitata and C. rosa and a source for infestation of orchards when fruit started to mature, highlighting the need for an area-wide strategy for the control of fruit flies.

Gray whale distribution relative to benthic invertebrate biomass and abundance: Northeastern Chukchi Sea 2009-2012

Science.gov (United States)

Brower, Amelia A.; Ferguson, Megan C.; Schonberg, Susan V.; Jewett, Stephen C.; Clarke, Janet T.

2017-10-01

The shallow continental shelf waters of the Bering and Chukchi seas are the northernmost foraging grounds of North Pacific gray whales (Eschrichtius robustus). Benthic amphipods are considered the primary prey of gray whales in these waters, although no comprehensive quantitative analysis has been performed to support this assumption. Gray whale relative abundance, distribution, and behavior in the northeastern Chukchi Sea (69°-72°N, 155-169°W) were documented during aerial surveys in June-October 2009-2012. Concurrently, vessel-based benthic infaunal sampling was conducted in the area in July-August 2009-10, September 2011, and August 2012. Gray whales were seen in the study area each month that surveys were conducted, with the majority of whales feeding. Statistical analyses confirm that the highest densities of feeding gray whales were associated with high benthic amphipod abundance, primarily within 70 km of shore from Point Barrow to Icy Cape, in water whales were not seen in 40-km×40-km cells containing benthic sampling stations with 85 m-2 or fewer amphipods. Continuing broad-scale aerial surveys in the Chukchi Sea and prey sampling near feeding gray whales will be an important means to monitor and document ongoing and predicted ecosystem changes.

Stable abundance, but changing size structure in grenadier fishes (Macrouridae) over a decade (1998-2008) in which deepwater fisheries became regulated

Science.gov (United States)

Neat, Francis; Burns, Finlay

2010-03-01

A ten-year time series (1998-2008) from a trawl survey of the continental slope of the NE Atlantic was analyzed to assess temporal variation in the abundance and length frequency of seven species of deepwater grenadier fish. This period coincided (in 2003) with the regulation of deepwater fisheries in this area. None of the species declined in numbers or biomass over the period, and 2 species significantly increased. This suggests that the declines in abundance of these deepwater species following the onset of fishing in the 1970s may now have stabilized, albeit at much lower levels than the virgin biomass. Although two metrics of body size (mean length and maximum length) did not show any evidence for consistent decrease over time, there were significant changes in the overall length-frequency distributions. The species found in shallower depths (500 m) had a greater number of larger individuals in 2008 whereas those found deeper (1500 m) tended to have a greater number of smaller individuals. This suggests the presence of a lagged indirect effect of fishing on species that live beyond the actual depths that fishing takes place.

The 2005 Tarapaca, Chile, Intermediate-depth Earthquake: Evidence of Heterogeneous Fluid Distribution Across the Plate?

Science.gov (United States)

Kuge, K.; Kase, Y.; Urata, Y.; Campos, J.; Perez, A.

2008-12-01

The physical mechanism of intermediate-depth earthquakes remains unsolved, and dehydration embrittlement in subducting plates is a candidate. An earthquake of Mw7.8 occurred at a depth of 115 km beneath Tarapaca, Chile. In this study, we suggest that the earthquake rupture can be attributed to heterogeneous fluid distribution across the subducting plate. The distribution of aftershocks suggests that the earthquake occurred on the subhorizontal fault plane. By modeling regional waveforms, we determined the spatiotemporal distribution of moment release on the fault plane, testing a different suite of velocity models and hypocenters. Two patches of high slip were robustly obtained, although their geometry tends to vary. We tested the results separately by computing the synthetic teleseismic P and pP waveforms. Observed P waveforms are generally modeled, whereas two pulses of observed pP require that the two patches are in the WNW-ESE direction. From the selected moment-release evolution, the dynamic rupture model was constructed by means of Mikumo et al. (1998). The model shows two patches of high dynamic stress drop. Notable is a region of negative stress drop between the two patches. This was required so that the region could lack wave radiation but propagate rupture from the first to the second patches. We found from teleseismic P that the radiation efficiency of the earthquake is relatively small, which can support the existence of negative stress drop during the rupture. The heterogeneous distribution of stress drop that we found can be caused by fluid. The T-P condition of dehydration explains the locations of double seismic zones (e.g. Hacker et al., 2003). The distance between the two patches of high stress drop agrees with the distance between the upper and lower layers of the double seismic zone observed in the south (Rietbrock and Waldhauser, 2004). The two patches can be parts of the double seismic zone, indicating the existence of fluid from dehydration

Linking carbon and nitrogen metabolism to depth distribution of submersed macrophytes using high ammonium dosing tests and a lake survey.

Science.gov (United States)

Yuan, Guixiang; Cao, Te; Fu, Hui; Ni, Leyi; Zhang, Xiaolin; Li, Wei; Song, Xin; Xie, Ping; Jeppesen, Erik

2013-12-01

Strategies of carbon (C) and nitrogen (N) utilisation are among the factors determining plant distribution. It has been argued that submersed macrophytes adapted to lower light environments are more efficient in maintaining C metabolic homeostasis due to their conservative C strategy and ability to balance C shortage. We studied how depth distributions of 12 submersed macrophytes in Lake Erhai, China, were linked to their C-N metabolic strategies when facing acute [Formula: see text] dosing.[Formula: see text] dosing changed C-N metabolism significantly by decreasing the soluble carbohydrate (SC) content and increasing the [Formula: see text]-N and free amino acid (FAA) content of plant tissues.The proportional changes in SC contents in the leaves and FAA contents in the stems induced by [Formula: see text] dosing were closely correlated (positive for SC and negative for FAA) with the colonising water depths of the plants in Lake Erhai, the plants adapted to lower light regimes being more efficient in maintaining SC and FAA homeostasis.These results indicate that conservative carbohydrate metabolism of submersed macrophytes allowed the plants to colonise greater water depths in eutrophic lakes, where low light availability in the water column diminishes carbohydrate production by the plants.

Depth distribution analysis of Martensitic transformations in Xe implanted austenitic stainless steel

DEFF Research Database (Denmark)

Johnson, E.; Gerritsen, E.; Chechenin, N.G.

1989-01-01

In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase...... transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission...... electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1 × 1020 m−2. The thickness of the transformed layer increases with fluence to ≈ 150 nm at 1 × 10 21 m−2, which far exceeds the range plus straggling...

Distribution and Diversity of Microbial Eukaryotes in Bathypelagic Waters of the South China Sea.

Science.gov (United States)

Xu, Dapeng; Jiao, Nianzhi; Ren, Rui; Warren, Alan

2017-05-01

Little is known about the biodiversity of microbial eukaryotes in the South China Sea, especially in waters at bathyal depths. Here, we employed SSU rDNA gene sequencing to reveal the diversity and community structure across depth and distance gradients in the South China Sea. Vertically, the highest alpha diversity was found at 75-m depth. The communities of microbial eukaryotes were clustered into shallow-, middle-, and deep-water groups according to the depth from which they were collected, indicating a depth-related diversity and distribution pattern. Rhizaria sequences dominated the microeukaryote community and occurred in all samples except those from less than 50-m deep, being most abundant near the sea floor where they contributed ca. 64-97% and 40-74% of the total sequences and OTUs recovered, respectively. A large portion of rhizarian OTUs has neither a nearest named neighbor nor a nearest neighbor in the GenBank database which indicated the presence of new phylotypes in the South China Sea. Given their overwhelming abundance and richness, further phylogenetic analysis of rhizarians were performed and three new genetic clusters were revealed containing sequences retrieved from the deep waters of the South China Sea. Our results shed light on the diversity and community structure of microbial eukaryotes in this not yet fully explored area. © 2016 The Author(s) Journal of Eukaryotic Microbiology © 2016 International Society of Protistologists.

Water column distribution of phospholipid-derived fatty acids of marine microorganisms in the Humboldt Current system off northern Chile

Science.gov (United States)

Espinosa, Luisa F.; Pantoja, Silvio; Pinto, Luis A.; Rullkötter, Jürgen

2009-07-01

Suspended particulate matter samples from the oxygenated surface zone, the oxygen minimum zone, and the oxygenated deeper zone were collected from the upwelling area off Antofagasta in northern Chile during austral autumn (April 2001) to study the composition of microbial phospholipid-derived fatty acid methyl esters, using capillary gas chromatography-mass spectrometry. Whereas phytoplanktonic carbon dominated living organic matter near the coast, bacterial carbon was most abundant offshore. The biomarker distribution showed some differences between the depth levels sampled, such as the highest microbial abundance in the epipelagic zone represented by phytoplankton, especially diatoms, and a homogeneous distribution of bacterial biomarkers, with no indication of vertical segregation of functional groups as previously thought.

The dependence of skin lesions on the depth-dose distribution from β-irradiation of people in the Chernobyl nuclear power plant accident

International Nuclear Information System (INIS)

Barabanova, A.

1990-01-01

A detailed study was made of conditions of exposure of 56 Chernobyl victims who suffered skin radiation lesions. The most typical conditions were experimentally reconstructed to investigate specific characteristics of dose distribution to the skin according to depth for different exposure conditions. Absorbed doses at depths of 7 mg cm -2 and 150 mg cm -2 were calculated on the basis of measurements with multilayer skin dosemeters. Patients were classified into four groups. Dosimetric characteristics for each group were compared with clinical pictures to establish critical factors in the occurrence of lesions. It was demonstrated that depth-dose distribution of β-radiation to the skin is of great influence not only for early effects of radiation but also for later effects. Radiation lesions in the skin led to death if the area of the lesions exceeded about 50% total body surface, and if doses to the skin were about 200-300 Gy at 7 mg cm -2 and more than about 30 Gy at 150 mg cm -2 . (author)

Fossil Signatures Using Elemental Abundance Distributions and Bayesian Probabilistic Classification

Science.gov (United States)

Hoover, Richard B.; Storrie-Lombardi, Michael C.

2004-01-01

Elemental abundances (C6, N7, O8, Na11, Mg12, Al3, P15, S16, Cl17, K19, Ca20, Ti22, Mn25, Fe26, and Ni28) were obtained for a set of terrestrial fossils and the rock matrix surrounding them. Principal Component Analysis extracted five factors accounting for the 92.5% of the data variance, i.e. information content, of the elemental abundance data. Hierarchical Cluster Analysis provided unsupervised sample classification distinguishing fossil from matrix samples on the basis of either raw abundances or PCA input that agreed strongly with visual classification. A stochastic, non-linear Artificial Neural Network produced a Bayesian probability of correct sample classification. The results provide a quantitative probabilistic methodology for discriminating terrestrial fossils from the surrounding rock matrix using chemical information. To demonstrate the applicability of these techniques to the assessment of meteoritic samples or in situ extraterrestrial exploration, we present preliminary data on samples of the Orgueil meteorite. In both systems an elemental signature produces target classification decisions remarkably consistent with morphological classification by a human expert using only structural (visual) information. We discuss the possibility of implementing a complexity analysis metric capable of automating certain image analysis and pattern recognition abilities of the human eye using low magnification optical microscopy images and discuss the extension of this technique across multiple scales.

Vertical distribution and community composition of anammox bacteria in sediments of a eutrophic shallow lake.

Science.gov (United States)

Qin, H; Han, C; Jin, Z; Wu, L; Deng, H; Zhu, G; Zhong, W

2018-07-01

The aim of this study was to explore the vertical distribution traits of anaerobic ammonium-oxidizing (anammox) bacterial relative abundance and community composition along the oxic/anoxic sediment profiles in a shallow lake. The Illumina Miseq-based sequencing and quantitative polymerase chain reactions were utilized to analyse relative abundance of anammox hydrazine synthase (hzsB) gene in comparison with bacterial 16S rRNA genes, anammox bacterial relative abundance (the number of anammox sequences divided by total number of sequences), community composition and diversity in sediments. The relative abundance of hzsB gene at the low-nitrogen (LN) site in the lake sediments showed that the vertical distribution of anammox bacteria increased to a peak, then decreased with increasing depth. Moreover, the relative abundance of hzsB gene at the high-nitrogen site was significantly lower than that at the LN site. Additionally, the community composition results showed that Candidatus Brocadia sp. was the dominant genus. In addition, the anammox bacterial diversity was also site specific. Redundancy analysis showed that the total N and the NH 4 + -N content might be the most important factors affecting anammox bacterial community composition in the studied sites. The results revealed the specific vertical variance of anammox bacterial distribution and community composition in oxic/anoxic sediments of a eutrophic shallow lake. This is the first study to demonstrate that anammox bacteria displayed the particular distribution in freshwater sediments, which implied a strong response to the anthropogenic eutrophication. © 2018 The Society for Applied Microbiology.

Abundance and distribution of fatty acids within the walls of an active deep-sea sulfide chimney

Science.gov (United States)

Li, Jiwei; Zhou, Huaiyang; Peng, Xiaotong; Fu, Meiyan; Chen, Zhiqiang; Yao, Huiqiang

2011-04-01

Abundance and distribution of total fatty acids (TFAs) were examined along the physicochemical gradient within an active hydrothermal chimney collected from the Main Endeavour segment of Juan de Fuca Ridge. Approximately 27 fatty acids are identified with a chain-length ranging from C12 to C22. From the exterior to the interior of the chimney walls, the total concentrations of TFAs (∑ TFAs) show a trend of evident decrease. The observed compositions of TFAs are rich in bacterial biomarkers especially monounsaturated fatty acids (MUFAs) and minor branched and cyclopropyl FAs. On the basis of the species-specific FAs and bacterial 16SrRNA gene analysis (Li et al., unpublished data), sulfur-based metabolism appears to be the essential metabolic process in the chimney. Furthermore, the sulfur oxidizing bacteria (SOB) are identified as a basic component of microbial communities at the exterior of the hydrothermal chimney, and its proportion shows an inward decrease while the sulfate reducing bacteria (SRB) have an inverse distribution.

Abundance and distribution of microplastics within surface sediments of a key shellfish growing region of Canada.

Science.gov (United States)

Kazmiruk, T N; Kazmiruk, V D; Bendell, L I

2018-01-01

The abundance and distribution of microplastics within 5 sediment size classes (>5000 μm, 1000-5000 μm, 250-1000 μm, 250-0.63 μm and Microplastics were found at all sampling locations indicating widespread contamination of this region with these particles. Three types of microplastics were recovered: microbeads, which occurred in the greatest number (up to 25000/kg dry sediment) and microfibers and microfragments, which were much less in number compared with microbeads and occurred in similar amounts (100-300/kg dry sediment). Microbeads were recovered primarily in the microplastics were spatially dependent with principal component analysis (PCA) indicating that 84 percent of the variation in abundance and distribution was due to the presence of high numbers of microbeads at three locations within the study region. At these sites, microbeads expressed as a percent component of the sediment by weight was similar to key geochemical components that govern trace metal behavior and availability to benthic organisms. Microbeads have been shown to accumulate metals from the aquatic environment, hence in addition to the traditional geochemical components such as silt and organic matter, microplastics also need to be considered as a sediment component that can influence trace metal geochemistry. Our findings have shown that BC's premier oyster growing region is highly contaminated with microplastics, notably microbeads. It would be prudent to assess the degree to which oysters from this region are ingesting microplastics. If so, it would have direct implications for Canada's oyster farming industry with respect to the health of the oyster and the quality of product that is being farmed and sets an example for other shellfish growing regions of the world.

Depth distribution of bubbles in 4He+-ion irradiated nickel and the mechanism of blister formation

International Nuclear Information System (INIS)

Fenske, G.; Das, S.K.; Kaminsky, M.; Miley, G.H.

1978-01-01

While the radiation blistering phenomenon has been widely studied, the mechanism of blister formation is still not well understood. The present studies on depth distribution of helium bubbles in nickel were carried out in order to obtain a better understanding of the radiation blistering process. Particularly, the aim was to understand the experimental observation that the blister skin thickness for many metals irradiated with He + ions of energies lower than 20-keV is a factor of two or more larger than the calculated projected range. (Auth.)

Fitting and comparing competing models of the species abundance distribution: assessment and prospect

Directory of Open Access Journals (Sweden)

Thomas J Matthews

2014-06-01

Full Text Available A species abundance distribution (SAD characterises patterns in the commonness and rarity of all species within an ecological community. As such, the SAD provides the theoretical foundation for a number of other biogeographical and macroecological patterns, such as the species–area relationship, as well as being an interesting pattern in its own right. While there has been resurgence in the study of SADs in the last decade, less focus has been placed on methodology in SAD research, and few attempts have been made to synthesise the vast array of methods which have been employed in SAD model evaluation. As such, our review has two aims. First, we provide a general overview of SADs, including descriptions of the commonly used distributions, plotting methods and issues with evaluating SAD models. Second, we review a number of recent advances in SAD model fitting and comparison. We conclude by providing a list of recommendations for fitting and evaluating SAD models. We argue that it is time for SAD studies to move away from many of the traditional methods available for fitting and evaluating models, such as sole reliance on the visual examination of plots, and embrace statistically rigorous techniques. In particular, we recommend the use of both goodness-of-fit tests and model-comparison analyses because each provides unique information which one can use to draw inferences.

Spatial distributions of dose enhancement around a gold nanoparticle at several depths of proton Bragg peak

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jihun [Department of Radiation Oncology, Hokkaido University Graduate School of Medicine, Hokkaido University (Japan); Sutherland, Kenneth [Department of Medical Physics, Hokkaido University Graduate School of Medicine, Hokkaido University (Japan); Hashimoto, Takayuki [Department of Radiation Medicine, Hokkaido University Graduate School of Medicine (Japan); Shirato, Hiroki [Department of Radiation Medicine, Hokkaido University Graduate School of Medicine and Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University (Japan); Date, Hiroyuki, E-mail: date@hs.hokudai.ac.jp [Faculty of Health Sciences, Hokkaido University (Japan)

2016-10-01

Gold nanoparticles (GNPs) have been recognized as a promising candidate for a radiation sensitizer. A proton beam incident on a GNP can produce secondary electrons, resulting in an enhancement of the dose around the GNP. However, little is known about the spatial distribution of dose enhancement around the GNP, especially in the direction along the incident proton. The purpose of this study is to determine the spatial distribution of dose enhancement by taking the incident direction into account. Two steps of calculation were conducted using the Geant4 Monte Carlo simulation toolkit. First, the energy spectra of 100 and 195 MeV protons colliding with a GNP were calculated at the Bragg peak and three other depths around the peak in liquid water. Second, the GNP was bombarded by protons with the obtained energy spectra. Radial dose distributions were computed along the incident beam direction. The spatial distributions of the dose enhancement factor (DEF) and subtracted dose (D{sub sub}) were then evaluated. The spatial DEF distributions showed hot spots in the distal radial region from the proton beam axis. The spatial D{sub sub} distribution isotropically spread out around the GNP. Low energy protons caused higher and wider dose enhancement. The macroscopic dose enhancement in clinical applications was also evaluated. The results suggest that the consideration of the spatial distribution of GNPs in treatment planning will maximize the potential of GNPs.

History of the stellar birthrate from lithium abundances in red giants

International Nuclear Information System (INIS)

Scalo, J.M.; Miller, G.E.

1980-01-01

The lithium abundance at the end of main-sequence evolution should increase strongly with mass for masses less than 1.4 M/sub sun/. It is shown that because of this dependence the frequency distribution of Li abundances in red giants is a sensitive probe of the history of the stellar birthrate in the solar neighborhood since the Li distribution directly reflects the stellar age distribution. A birthrate which decreases with time gives a smaller mean red giant Li abundance than an increasing birthrate because a larger fraction of red giants are older and hence less massive. Theoretical Li abundance frequency distributions are calculated for exponentially increasing, constant, and exponentially decreasing birthrates using a semiempirical prescription for main-sequence Li destruction, theoretical main-sequence lifetimes and red giant dilution factors, and self-consistent initial mass functions. The results are compared with the observed abundance distribution for 35 giants studied by Lambert and his colleagues. Allowing for uncertainties, we find that the ratio of present birthrate to average past birthrate has a value between 0.5 and 2. These limits are consistent with results of most other methods of determining the birthrate history, but the present method provides a considerably more stringent lower limit. It is also shown that, with more observational data, fluctuations in the birthrate with a time scale of about one billion years during the period between two and six billion years ago could be resolved

Plant nutrient acquisition strategies in tundra species: at which soil depth do species take up their nitrogen?

Science.gov (United States)

Limpens, Juul; Heijmans, Monique; Nauta, Ake; van Huissteden, Corine; van Rijssel, Sophie

2016-04-01

The Arctic is warming at unprecedented rates. Increased thawing of permafrost releases nutrients locked up in the previously frozen soils layers, which may initiate shifts in vegetation composition. The direction in which the vegetation shifts will co-determine whether Arctic warming is mitigated or accelerated, making understanding successional trajectories urgent. One of the key factors influencing the competitive relationships between plant species is their access to nutrients, in particularly nitrogen (N). We assessed the depth at which plant species took up N by performing a 15N tracer study, injecting 15(NH4)2SO4 at three depths (5, 15, 20 cm) into the soil in arctic tundra in north-eastern Siberia in July. In addition we explored plant nutrient acquisition strategy by analyzing natural abundances of 15N in leaves. We found that vascular plants took up 15N at all injection depths, irrespective of species, but also that species showed a clear preference for specific soil layers that coincided with their functional group (graminoids, dwarf shrubs, cryptogams). Graminoids took up most 15N at 20 cm depth nearest to the thaw front, with grasses showing a more pronounced preference than sedges. Dwarf shrubs took up most 15N at 5 cm depth, with deciduous shrubs displaying more preference than evergreens. Cryptogams did not take up any of the supplied 15N . The natural 15N abundances confirmed the pattern of nutrient acquisition from deeper soil layers in graminoids and from shallow soil layers in both deciduous and evergreen dwarf shrubs. Our results prove that graminoids and shrubs differ in their N uptake strategies, with graminoids profiting from nutrients released at the thaw front, whereas shrubs forage in the upper soil layers. The above implies that graminoids, grasses in particular, will have a competitive advantage over shrubs as the thaw front proceeds and/or superficial soil layers dry out. Our results suggest that the vertical distribution of nutrients

Landscape Effects on the Presence, Abundance and Diversity of Mosquitoes in Mediterranean Wetlands.

Directory of Open Access Journals (Sweden)

David Roiz

Full Text Available Environment determines the distribution of mosquito-borne diseases in that it influences the vector-host-pathogen transmission cycle, including vector distribution, abundance and diversity. In this study, we analyse the relationship between environmental variables estimated by remote sensing and the spatial distribution (presence, abundance and diversity of seven mosquito species vectors of West Nile and other pathogens (Usutu, avian malaria and dirofilariasis in the Doñana Natural Park, Spain. Traps were distributed over an area of 54,984 ha divided into six ecological units: marshland, sand dunes, scrubland, ricefields, crops and fishponds. We collected mosquitoes once a month from up to 112 locations using BG-Sentinel traps baited with BG-lure and CO2 during March-November 2010. Hydroperiod, NDVI and Inundation surface were estimated at several resolution scales (100, 250, 500, 1000 and 2000 metres from corrected and normalized Landsat Images. We sampled 972,346 female mosquitoes, the most abundant species being Culex theileri, Ochlerotatus caspius, Culex modestus, Culex perexiguus, Culex pipiens, Anopheles atroparvus and Ochlerotatus detritus. Our results suggest that: (1 hydroperiod, inundation surface and NDVI are strongly related to the spatial distribution of mosquitoes; (2 the spatial scales used to measure these variables affected quantification of these relationships, the larger scale being more informative; (3 these relationships are species-specific; (4 hydroperiod is negatively related to mosquito presence and richness; (5 Culex abundance is positively related to hydroperiod; (6 NDVI is positively related to mosquito diversity, presence and abundance, except in the case of the two salt marsh species (Oc. caspius and Oc. detritus; and (7 inundation surfaces positively condition the abundance and richness of most species except the salt marsh mosquitoes. Remote sensing data provided reliable information for monitoring mosquito

Abundances in galaxies

International Nuclear Information System (INIS)

Pagel, B.E.J.

1991-01-01

Standard (or mildly inhomogeneous) Big Bang nucleosynthesis theory is well confirmed by abundance measurements of light elements up to 7 Li and the resulting upper limit to the number of neutrino families confirmed in accelerator experiments. Extreme inhomogeneous models with a closure density in form of baryons seem to be ruled out and there is no evidence for a cosmic 'floor' to 9 Be or heavier elements predicted in some versions of those models. Galaxies show a correlation between luminous mass and abundance of carbon and heavier elements, usually attributed to escape of hot gas from shallow potential wells. Uncertainties include the role of dark matter and biparametric behaviour of ellipticals. Spirals have radial gradients which may arise from a variety of causes. In our own Galaxy one can distinguish three stellar populations - disk, halo and bulge - characterised by differing metallicity distribution functions. Differential abundance effects are found among different elements in stars as a function of metallicity and presumably age, notably in the ratio of oxygen and α-particle elements to iron. These may eventually be exploitable to set a time scale for the formation of the halo, bulge and disk. (orig.)

Potential impacts of OCS oil and gas activities on fisheries. Volume 1. Annotated bibliography and database descriptions for target-species distribution and abundance studies. Section 1, Part 2. Final report

International Nuclear Information System (INIS)

Tear, L.M.

1989-10-01

The purpose of the volume is to present an annotated bibliography of unpublished and grey literature related to the distribution and abundance of select species of finfish and shellfish along the coasts of the United States. The volume also includes descriptions of databases that contain information related to target species' distribution and abundance. An index is provided at the end of each section to help the reader locate studies or databases related to a particular species

Potential impacts of OCS oil and gas activities on fisheries. Volume 1. Annotated bibliography and database descriptions for target species distribution and abundance studies. Section 1, Part 1. Final report

International Nuclear Information System (INIS)

Tear, L.M.

1989-10-01

The purpose of the volume is to present an annotated bibliography of unpublished and grey literature related to the distribution and abundance of select species of finfish and shellfish along the coasts of the United States. The volume also includes descriptions of databases that contain information related to target species' distribution and abundance. An index is provided at the end of each section to help the reader locate studies or databases related to a particular species

Abundance and size distribution of the sacoglossan Elysia viridis on co-occurring algal hosts on the Swedish west coast.

Directory of Open Access Journals (Sweden)

Finn A Baumgartner

Full Text Available Sacoglossans are specialized marine herbivores that tend to have a close evolutionary relationship with their macroalgal hosts, but the widely distributed species Elysia viridis can associate with several algal species. However, most previous investigations on the field abundance and size distribution of E. viridis have focussed on Codium spp. in the British Isles, and algae from this genus are considered superior hosts for E. viridis. In the present study, we investigated the abundance and size distribution of E. viridis on 6 potential host algae with differing morphologies (the septate species Cladophora sericea, Cladophora rupestris, Chaetomorpha melagonium, and Ceramium virgatum, as well as the siphonaceous species Codium fragile and Bryopsis sp. at 2 sites on the Swedish west coast over the course of a year. In spring, slugs were almost absent from all algal hosts. In summer and autumn, E. viridis consistently occurred on several of the algal species at both sites. The highest number of small E. viridis were found on C. sericea, intermediate numbers of significantly larger E. viridis were found on C. rupestris, while fewer, intermediate sized animals were found on C. fragile. Throughout the study period, only a few E. viridis individuals were found on C. melagonium, Bryopsis sp., and C. virgatum. Our results indicate that E. viridis is an annual species in Sweden, capable of exploiting co-occurring congeneric and intergeneric algal hosts with differing morphologies. These results corroborate previous findings that E. viridis can exploit several different algal species, but does not indicate that C. fragile is a superior host.

Influence of climatic conditions and elevation on the spatial distribution and abundance of Trypodendron ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in Alaska

Science.gov (United States)

Robin M. Reich; John E. Lundquist; Robert E. Acciavati

2014-01-01

The objective of this study was to model the influence of temperature and precipitation on the distribution and abundance of the ambrosia beetles in the genus Trypodendron. Although these beetles do not attack and kill healthy trees, their gallery holes and accompanying black and gray stain associated with symbiotic ambrosial fungi can cause significant economic losses...

CHARACTERIZING THE HEAVY ELEMENTS IN GLOBULAR CLUSTER M22 AND AN EMPIRICAL s-PROCESS ABUNDANCE DISTRIBUTION DERIVED FROM THE TWO STELLAR GROUPS

International Nuclear Information System (INIS)

Roederer, I. U.; Marino, A. F.; Sneden, C.

2011-01-01

We present an empirical s-process abundance distribution derived with explicit knowledge of the r-process component in the low-metallicity globular cluster M22. We have obtained high-resolution, high signal-to-noise spectra for six red giants in M22 using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory. In each star we derive abundances for 44 species of 40 elements, including 24 elements heavier than zinc (Z = 30) produced by neutron-capture reactions. Previous studies determined that three of these stars (the 'r+s group') have an enhancement of s-process material relative to the other three stars (the 'r-only group'). We confirm that the r+s group is moderately enriched in Pb relative to the r-only group. Both groups of stars were born with the same amount of r-process material, but s-process material was also present in the gas from which the r+s group formed. The s-process abundances are inconsistent with predictions for asymptotic giant branch (AGB) stars with M ≤ 3 M ☉ and suggest an origin in more massive AGB stars capable of activating the 22 Ne(α,n) 25 Mg reaction. We calculate the s-process 'residual' by subtracting the r-process pattern in the r-only group from the abundances in the r+s group. In contrast to previous r- and s-process decompositions, this approach makes no assumptions about the r- and s-process distributions in the solar system and provides a unique opportunity to explore s-process yields in a metal-poor environment.

Determination of the columnar aerosol size distribution by inversion of spectral aerosol optical depth measurements at different areas in Egypt

International Nuclear Information System (INIS)

EI-Metwally, M.; Madkour, M.A.

2006-01-01

Aerosols have a great effects on nuclear safety calculations and atmospheric environment. The aerosol optical depth measurements are carried out at four areas in Egypt: Cairo and Helwan as urban/industrial areas, Aswan as an arid area and Mansoura as an agricultural area covering the period from Jun 1992 to May 1993. These measurements were recorded by ground-based pyrheliometers with large band-pass filters. Monthly average values of aerosol optical depth (AOD) showed a pronounced temporal trend, with a maximum AOD during summer and the transition seasons (spring and autumn) at all sites. Levels of AODs are higher at both urban and industrial areas than at other areas. Variation of Angstrom exponent a with the AOD was clear at most sites and the a value depends on the spectral range used in its determination. The mean contribution of anthropogenic sources to AOD over Cairo was at the range of 25.1-54.3%, whereas those values in Helwan were at the range of 34.5-59.8%. Finally, columnar aerosol size distributions have been inferred by inverting particularly AOD measurements as a function of wavelength. The Junge (type I) and bimodal (type III) distributions are dominant at urban and arid areas (Cairo and Aswan), whereas mono dispersion distribution (type II) are dominant in industrial and agricultural areas (Helwan and Mansoura). In Cairo and Aswan, the peak of columnar size distribution for the fine mode at radius r is around 0.1 and 0.2 μm respectively, while it is around 1.0 and 2.0 μm for the coarse mode. .Also, the peak of size distribution for the mono dispersion mode was marked at radius around 0.2 μm at both Helwan and Mansoura. A comprehensive comparison of our results with literature size distributions is very sparse, nevertheless, our size distributions in general agree with them

Low planktic foraminiferal diversity and abundance observed in a spring 2013 west-east Mediterranean Sea plankton tow transect

Science.gov (United States)

Mallo, Miguel; Ziveri, Patrizia; Mortyn, P. Graham; Schiebel, Ralf; Grelaud, Michael

2017-05-01

Planktic foraminifera were collected with 150 µm BONGO nets from the upper 200 m water depth at 20 stations across the Mediterranean Sea between 2 May and 2 June 2013. The main aim is to characterize the species distribution and test the covariance between foraminiferal area density (ρA) and seawater carbonate chemistry in a biogeochemical gradient including ultraoligotrophic conditions. Average foraminifera abundances are 1.42 ± 1.43 ind. 10 m-3 (ranging from 0.11 to 5.20 ind. 10 m-3), including 12 morphospecies. Large differences in species assemblages and total abundances are observed between the different Mediterranean sub-basins, with an overall dominance of spinose, symbiont-bearing species indicating oligotrophic conditions. The highest values in absolute abundance are found in the Strait of Gibraltar and the Alboran Sea. The western basin is dominated by Globorotalia inflata and Globigerina bulloides at slightly lower standing stocks than in the eastern basin. In contrast, the planktic foraminiferal assemblage in the warmer, saltier, and more nutrient-limited eastern basin is dominated by Globigerinoides ruber (white). These new results, when combined with previous findings, suggest that temperature-induced surface water stratification and food availability are the main factors controlling foraminiferal distribution. In the oligotrophic and highly alkaline and supersaturated with respect to calcite and aragonite Mediterranean surface water, standing stocks and ρA of G. ruber (white) and G. bulloides are affected by both food availability and seawater carbonate chemistry. Rapid warming increased surface ocean stratification impacting food availability and changes in trophic conditions could be the causes of reduced foraminiferal abundance, diversity, and species-specific changes in planktic foraminiferal calcification.

Use of abundance of one species as a surrogate for abundance of others

Science.gov (United States)

Samuel A. Cushman; Kevin S. McKelvey; Barry R. Noon; Kevin McGarigal

2010-01-01

Indicator species concepts have a long history in conservation biology. Arguments in favor of these approaches generally stress expediency and assume efficacy. We tested the premise that the abundance patterns of one species can be used to infer those of other species. Our data consisted of 72,495 bird observations on 55 species across 1046 plots distributed across 30...

Abundance and Diversity of Denitrifying and Anammox Bacteria in Seasonally Hypoxic and Sulfidic Sediments of the Saline Lake Grevelingen

Science.gov (United States)

Lipsewers, Yvonne A.; Hopmans, Ellen C.; Meysman, Filip J. R.; Sinninghe Damsté, Jaap S.; Villanueva, Laura

2016-01-01

Denitrifying and anammox bacteria are involved in the nitrogen cycling in marine sediments but the environmental factors that regulate the relative importance of these processes are not well constrained. Here, we evaluated the abundance, diversity, and potential activity of denitrifying, anammox, and sulfide-dependent denitrifying bacteria in the sediments of the seasonally hypoxic saline Lake Grevelingen, known to harbor an active microbial community involved in sulfur oxidation pathways. Depth distributions of 16S rRNA gene, nirS gene of denitrifying and anammox bacteria, aprA gene of sulfur-oxidizing and sulfate-reducing bacteria, and ladderane lipids of anammox bacteria were studied in sediments impacted by seasonally hypoxic bottom waters. Samples were collected down to 5 cm depth (1 cm resolution) at three different locations before (March) and during summer hypoxia (August). The abundance of denitrifying bacteria did not vary despite of differences in oxygen and sulfide availability in the sediments, whereas anammox bacteria were more abundant in the summer hypoxia but in those sediments with lower sulfide concentrations. The potential activity of denitrifying and anammox bacteria as well as of sulfur-oxidizing, including sulfide-dependent denitrifiers and sulfate-reducing bacteria, was potentially inhibited by the competition for nitrate and nitrite with cable and/or Beggiatoa-like bacteria in March and by the accumulation of sulfide in the summer hypoxia. The simultaneous presence and activity of organoheterotrophic denitrifying bacteria, sulfide-dependent denitrifiers, and anammox bacteria suggests a tight network of bacteria coupling carbon-, nitrogen-, and sulfur cycling in Lake Grevelingen sediments. PMID:27812355

Abundance and diversity of denitrifying and anammox bacteria in seasonally hypoxic and sulfidic sediments of the saline Lake Grevelingen

Directory of Open Access Journals (Sweden)

Yvonne A. Lipsewers

2016-10-01

Full Text Available Denitrifying and anammox bacteria are involved in the nitrogen cycling in marine sediments but the environmental factors that regulate the relative importance of these processes are not well constrained. Here, we evaluated the abundance, diversity and potential activity of denitrifying, anammox, and sulfide-dependent denitrifying bacteria in the sediments of the seasonally hypoxic saline Lake Grevelingen, known to harbor an active microbial community involved in sulfur oxidation pathways. Depth distributions of 16S rRNA gene, nirS gene of denitrifying and anammox bacteria, aprA gene of sulfur-oxidizing and sulfate-reducing bacteria, and ladderane lipids of anammox bacteria were studied in sediments impacted by seasonally hypoxic bottom waters. Samples were collected down to 5 cm depth (1 cm resolution at three different locations before (March and during summer hypoxia (August. The abundance of denitrifying bacteria did not vary despite of differences in oxygen and sulfide availability in the sediments, whereas anammox bacteria were more abundant in the summer hypoxia but in those sediments with lower sulfide concentrations. The potential activity of denitrifying and anammox bacteria as well as of sulfur-oxidizing, including sulfide-dependent denitrifiers and sulfate-reducing bacteria, was potentially inhibited by the competition for nitrate and nitrite with cable and/or Beggiatoa-like bacteria in March and by the accumulation of sulfide in the summer hypoxia. The simultaneous presence and activity of organoheterotrophic denitrifying bacteria, sulfide-dependent denitrifiers and anammox bacteria suggests a tight network of bacteria coupling carbon-, nitrogen- and sulfur cycling in Lake Grevelingen sediments.

Fluctuating water depths affect American alligator (Alligator mississippiensis) body condition in the Everglades, Florida, USA

Science.gov (United States)

Brandt, Laura A.; Beauchamp, Jeffrey S.; Jeffery, Brian M.; Cherkiss, Michael S.; Mazzotti, Frank J.

2016-01-01

Successful restoration of wetland ecosystems requires knowledge of wetland hydrologic patterns and an understanding of how those patterns affect wetland plant and animal populations.Within the Everglades, Florida, USA restoration, an applied science strategy including conceptual ecological models linking drivers to indicators is being used to organize current scientific understanding to support restoration efforts. A key driver of the ecosystem affecting the distribution and abundance of organisms is the timing, distribution, and volume of water flows that result in water depth patterns across the landscape. American alligators (Alligator mississippiensis) are one of the ecological indicators being used to assess Everglades restoration because they are a keystone species and integrate biological impacts of hydrological operations through all life stages. Alligator body condition (the relative fatness of an animal) is one of the metrics being used and targets have been set to allow us to track progress. We examined trends in alligator body condition using Fulton’s K over a 15 year period (2000–2014) at seven different wetland areas within the Everglades ecosystem, assessed patterns and trends relative to restoration targets, and related those trends to hydrologic variables. We developed a series of 17 a priori hypotheses that we tested with an information theoretic approach to identify which hydrologic factors affect alligator body condition. Alligator body condition was highest throughout the Everglades during the early 2000s and is approximately 5–10% lower now (2014). Values have varied by year, area, and hydrology. Body condition was positively correlated with range in water depth and fall water depth. Our top model was the “Current” model and included variables that describe current year hydrology (spring depth, fall depth, hydroperiod, range, interaction of range and fall depth, interaction of range and hydroperiod). Across all models, interaction

Relative abundance and distribution of bacteria in the gut of ...

African Journals Online (AJOL)

Escherichia coli, Aeromonas hydrophila, Salmonella typhi and Pseudomonas aeruginosa were the most abundant species in the samples from Epe Lagoon while Escherichia coli, Aeromonas hydrophila, Proteus vulgaris and Pseudomonas aeruginosa were predominant in Badagry Creek. It was noteworthy that Citrobacter ...

Abundance, composition and distribution of solid wastes in the ...

African Journals Online (AJOL)

... 2013 at 68 stations in six depth strata using the bottom trawl swept area method. ... (42%), longlines and hooks (7%), plastic bags (4%), floats (2%), and clothing (1%). ... solid waste pollution is not at present a major problem in Lake Victoria.

ISLSCP II Ecosystem Rooting Depths

Data.gov (United States)

National Aeronautics and Space Administration — The goal of this study was to predict the global distribution of plant rooting depths based on data about global aboveground vegetation structure and climate....

ISLSCP II Ecosystem Rooting Depths

Data.gov (United States)

National Aeronautics and Space Administration — ABSTRACT: The goal of this study was to predict the global distribution of plant rooting depths based on data about global aboveground vegetation structure and...

Quantitative distribution of metazoan meiofauna in continental margin sediments of the Skagerrak (Northeastern North Sea)

Science.gov (United States)

De Bovée, F.; Hall, P. O. J.; Hulth, S.; Hulthe, G.; Landén, A.; Tengberg, A.

1996-02-01

A quantitative survey of metazoan meiofauna in continental-margin sediments of the Skagerrak was carried out using virtually undisturbed sediment samples collected with a multiple corer. Altogether 11 stations distributed along and across the Norwegian Trench were occupied during three cruises. Abundance ranged from 155 to 6846 ind·10 cm -2 and revealed a sharply decreasing trend with increasing water depth. The densities were high on the upper part of the Danish margin (6846 ind·10 cm -2 at 194 m depth) and low in the central part of the deep Skagerrak (155 ind·10 cm -2 at 637 m depth). Also body lengths were significantly shorter on the Danish margin then elsewhere in the Skagerrak, indicating a greater importance of juveniles in this area. We suggest that the high densities may be explained by a stimulated renewal of the fauna, possibly induced by an adequate food supply. The low abundances found in sediments from the deepest part of the Norwegian Trench cannot be attributed to any lack of oxygen. We suggest that the low meiofaunal abundances are caused by a decrease in the food supply (accentuated in this area by lower sedimentation rates) and/or by the very high concentrations of dissolved manganese in the pore water of these sediments. The metazoan meiofauna was largely dominated by nematodes. Comparison of the respiration rates of the nematode population with the total benthic respiration (0.5 to 14%) suggests that the relative importance of metazoan meiofauna decreased with water depth.

Tracking Electroencephalographic Changes Using Distributions of Linear Models: Application to Propofol-Based Depth of Anesthesia Monitoring.

Science.gov (United States)

Kuhlmann, Levin; Manton, Jonathan H; Heyse, Bjorn; Vereecke, Hugo E M; Lipping, Tarmo; Struys, Michel M R F; Liley, David T J

2017-04-01

Tracking brain states with electrophysiological measurements often relies on short-term averages of extracted features and this may not adequately capture the variability of brain dynamics. The objective is to assess the hypotheses that this can be overcome by tracking distributions of linear models using anesthesia data, and that anesthetic brain state tracking performance of linear models is comparable to that of a high performing depth of anesthesia monitoring feature. Individuals' brain states are classified by comparing the distribution of linear (auto-regressive moving average-ARMA) model parameters estimated from electroencephalographic (EEG) data obtained with a sliding window to distributions of linear model parameters for each brain state. The method is applied to frontal EEG data from 15 subjects undergoing propofol anesthesia and classified by the observers assessment of alertness/sedation (OAA/S) scale. Classification of the OAA/S score was performed using distributions of either ARMA parameters or the benchmark feature, Higuchi fractal dimension. The highest average testing sensitivity of 59% (chance sensitivity: 17%) was found for ARMA (2,1) models and Higuchi fractal dimension achieved 52%, however, no statistical difference was observed. For the same ARMA case, there was no statistical difference if medians are used instead of distributions (sensitivity: 56%). The model-based distribution approach is not necessarily more effective than a median/short-term average approach, however, it performs well compared with a distribution approach based on a high performing anesthesia monitoring measure. These techniques hold potential for anesthesia monitoring and may be generally applicable for tracking brain states.

Shallow moonquakes - Depth, distribution and implications as to the present state of the lunar interior

Science.gov (United States)

Nakamura, Y.; Latham, G. V.; Dorman, H. J.; Ibrahim, A.-B. K.; Koyama, J.; Horvath, P.

1979-01-01

The observed seismic amplitudes of HFT (high-frequency teleseismic) events do not vary with distance as expected for surface sources, but are consistent with sources in the upper mantle of the moon. Thus, the upper mantle of the moon is the only zone where tectonic stresses deriving from differential thermal contraction and expansion of the lunar interior are presently high enough to cause moonquakes. The distribution of shallow moonquake epicenters suggests a possible correlation with impact basins, implying a lasting tectonic influence of impact basins long after their formation. The finite depths now assigned to these shallow moonquakes necessitate further revision to the seismic structural model of the lunar interior.

Impacts of macro - and microplastic on macrozoobenthos abundance in intertidal zone

Science.gov (United States)

Bangun, A. P.; Wahyuningsih, H.; Muhtadi, A.

2018-02-01

Plastics pollution in coastal areas is one of the topics that have received more attention over the past few years. The intertidal zone is a waters area that is directly affected by contamination of plastic waste from land and sea. The purpose of this study was to analyze the types and abundance of plastic waste in the intertidal zone and its impact on macrozoobenthos abundance. This research was conducted at Pesisir Desa Jaring Halus in February-April 2017. Macrozoobenthos and macro - micro plastic were collected by using quadratic transect. Sediments were collected with a core, to a depth of 30 cm. Microplastic and macroplastic abundances were analyzed using separation of sediment density and hand sorting. The dominant micro plastic types were film (52.30%), fiber (24.88%), fragments (22.74%), followed by pellets (0.1%). The total number of microplastics were 326,33 items and macro plastic were 308 items. Macroplastic abundance is positively correlated with microplastic (0.765). The abundance of macrozoobenthos is negatively correlated with microplastic abundance (-0.368) and with macro plastic abundance (-0.633). The management strategies were suggested clean up marine debris, decrease plastic using and built up the station of debris processing.

Fluence dependence of disorder depth profiles in Pb implanted Si

International Nuclear Information System (INIS)

Christodoulides, C.E.; Kadhim, N.J.; Carter, G.

1980-01-01

The total, depth integrated disorder, induced by Pb implantation into Si at room temperature, initially increases rapidly with implantation fluence and then reaches a quasi saturation level where the increase with fluence is slow. Measurements of the depth distributions of the disorder, using high resolution low angle exit Rutherford Backscattering/Channelling analysis, suggest that the quasi saturation results from overlapping of disordered zones generated deep in the tail of the disorder-depth profiles. The depth of the disordered solid-crystal boundary, xsub(D), increases with ion fluence PHI, according to the relation xsub(D) = x bar + f(PHI).σ, where x bar is the most probable projected depth and σ the projected standard deviation of disorder generation. It is shown that this relationship is consistent with an approximately Gaussian depth distribution of disorder production. (author)

Does footprint depth correlate with foot motion and pressure?

Science.gov (United States)

Bates, K T; Savage, R; Pataky, T C; Morse, S A; Webster, E; Falkingham, P L; Ren, L; Qian, Z; Collins, D; Bennett, M R; McClymont, J; Crompton, R H

2013-06-06

Footprints are the most direct source of evidence about locomotor biomechanics in extinct vertebrates. One of the principal suppositions underpinning biomechanical inferences is that footprint geometry correlates with dynamic foot pressure, which, in turn, is linked with overall limb motion of the trackmaker. In this study, we perform the first quantitative test of this long-standing assumption, using topological statistical analysis of plantar pressures and experimental and computer-simulated footprints. In computer-simulated footprints, the relative distribution of depth differed from the distribution of both peak and pressure impulse in all simulations. Analysis of footprint samples with common loading inputs and similar depths reveals that only shallow footprints lack significant topological differences between depth and pressure distributions. Topological comparison of plantar pressures and experimental beach footprints demonstrates that geometry is highly dependent on overall print depth; deeper footprints are characterized by greater relative forefoot, and particularly toe, depth than shallow footprints. The highlighted difference between 'shallow' and 'deep' footprints clearly emphasizes the need to understand variation in foot mechanics across different degrees of substrate compliance. Overall, our results indicate that extreme caution is required when applying the 'depth equals pressure' paradigm to hominin footprints, and by extension, those of other extant and extinct tetrapods.

Ammonia abundances in comets

Science.gov (United States)

Wyckoff, S.; Tegler, S.; Engel, L.

The emission band strengths of the NH2 bands of Comets Halley, Hartley-Good, Thiele, and Borrelly were measured to determine the NH2 column densities for the comets. Production rates obtained using the Haser and vectorial models are in agreement within the observational errors, suggesting that a simple two-step decay model may be used to approximate the NH2 distribution in a comet's coma. Ammonia-to-water abundance ratios from 0.01 to 0.4 percent were found for the four comets. The ratio in Comet Halley is found to be Q(NH3)/Q(H2O) = 0.002 + or - 0.001. No significant difference in the ammonia abundance was found before or after perihelion in Comet Halley.

Influence of climatic conditions on the distribution, abundance and activity of Agriotes lineatus L. adults in sex pheromone traps in Croatia

Science.gov (United States)

Kozina, Antonela; Čačija, Maja; Igrc Barčić, Jasminka; Bažok, Renata

2013-07-01

The aims of this work were: (i) to determine the distribution and abundance of Agriotes lineatus, (ii) correlate the abundance with the prevailing climatic conditions to establish how temperature and rainfall are influencing the dominance, and (iii) to determine the activity characteristics of the adults. Investigations were conducted in 17 fields grouped in four regions characterized by different climatic conditions. Using sex pheromone traps the most important Agriotes species ( A. lineatus L., A. sputator L., A. obscurus L., A. brevis Cand. and A. ustulatus Schall.) were collected. The monitoring period for A. brevis, A. sputator, A. lineatus and A. obscurus was from the 18th to the 32nd, and for A. ustulatus from the 23rd to the 32nd week of the year. A total of 61,247 individuals Agriotes were captured, of which 24,916 individuals were A. lineatus. Abundance and dominance of A. lineatus were significantly higher in the region of Zagreb compared to other regions. Moving east, rainfall decreased and temperatures increased and associated with that the abundance and dominance indices were lower. It was determined that the abundance of A. lineatus was negatively correlated with average air temperature ( r = -0.5201; p < 0.0001). Compared to earlier data from the region of Zagreb the dominance index decreased. This might be a result of climate change as established average yearly temperature in these regions increased for 1.04 °C compared to the average data for the period 1961-1990. Other potentially damaging Agriotes species ( A. brevis and A. ustulatus) were also present in high abundances in some micro-regions.

Seasonal Blowfly Distribution and Abundance in Fragmented Landscapes. Is It Useful in Forensic Inference about Where a Corpse Has Been Decaying?

Science.gov (United States)

Zabala, Jabi; Díaz, Beatriz; Saloña-Bordas, Marta I.

2014-01-01

Blowflies are insects of forensic interest as they may indicate characteristics of the environment where a body has been laying prior to the discovery. In order to estimate changes in community related to landscape and to assess if blowfly species can be used as indicators of the landscape where a corpse has been decaying, we studied the blowfly community and how it is affected by landscape in a 7,000 km2 region during a whole year. Using baited traps deployed monthly we collected 28,507 individuals of 10 calliphorid species, 7 of them well represented and distributed in the study area. Multiple Analysis of Variance found changes in abundance between seasons in the 7 analyzed species, and changes related to land use in 4 of them (Calliphora vomitoria, Lucilia ampullacea, L. caesar and L. illustris). Generalised Linear Model analyses of abundance of these species compared with landscape descriptors at different scales found only a clear significant relationship between summer abundance of C. vomitoria and distance to urban areas and degree of urbanisation. This relationship explained more deviance when considering the landscape composition at larger geographical scales (up to 2,500 m around sampling site). For the other species, no clear relationship between land uses and abundance was found, and therefore observed changes in their abundance patterns could be the result of other variables, probably small changes in temperature. Our results suggest that blowfly community composition cannot be used to infer in what kind of landscape a corpse has decayed, at least in highly fragmented habitats, the only exception being the summer abundance of C. vomitoria. PMID:24918607

Amphipod family distributions around Iceland

Directory of Open Access Journals (Sweden)

Saskia Brix

2018-01-01

Full Text Available Amphipod crustaceans were collected at all 55 stations sampled with an epibenthic sledge during two IceAGE expeditions (Icelandic marine Animals: Genetics and Ecology in 2011 and 2013. In total, 34 amphipod families and three superfamilies were recorded in the samples. Distribution maps are presented for each taxon along with a summary of the regional taxonomy for the group. Statistical analyses based on presence/absence data revealed a pattern of family distributions that correlated with sampling depth. Clustering according to the geographic location of the stations (northernmost North Atlantic Sea and Arctic Ocean can also be observed. IceAGE data for the Amphilochidae and Oedicerotidae were analysed on species level; in case of the Amphilochidae they were compared to the findings from a previous Icelandic benthic survey, BIOICE (Benthic Invertebrates of Icelandic waters, which also identified a high abundance of amphipod fauna.

species composition, relative abundance and distribution

African Journals Online (AJOL)

Preferred Customer

College of Natural Sciences, Addis Ababa University, 2011. ISSN: 0379– ... distribution at Entoto Natural Park and escarpment was carried out during July 2009 - March 2010. The study ..... University Press, Princeton and Oxford, 496 pp. 20.

Temporal and spatial distribution of the meiobenthic community in Daya Bay, South China Sea

Science.gov (United States)

Tang, L.; Li, H. X.; Yan, Y.

2012-04-01

Spatial and temporal biodiversity patterns of the meiobenthos were studied for the first time in Daya Bay, which is a tropical semi-enclosed basin located in the South China Sea. The abundance, biomass, and composition of the meiobenthos and the basic environmental factors in the bay were investigated. The following 19 taxonomic groups were represented in the meiofauna: Nematoda, Copepoda, Polychaeta, Oligochaeta, Kinorhyncha, Gastrotricha, Ostracoda, Bivalvia, Turbellaria, Nemertinea, Sipuncula, Hydroida, Amphipoda, Cumacea, Halacaroidea, Priapulida, Echinodermata, Tanaidacea, and Rotifera. Total abundance and biomass of the meiobenthos showed great spatial and temporal variation, with mean values of 993.57 ± 455.36 ind cm-2 and 690.51 ± 210.64 μg 10 cm-2, respectively. Nematodes constituted 95.60 % of the total abundance and thus had the greatest effect on meiofauna quantity and distribution, followed by copepods (1.55 %) and polychaetes (1.39 %). Meiobenthos abundance was significantly negatively correlated with water depth at stations (r=-0.747, P<0.05) and significantly negatively correlated with silt-clay content (r=-0.516, P<0.01) and medium diameter (r=-0.499, P<0.01) of the sediment. Similar results were found for correlations of biomass and abundance of nematodes with environmental parameters. Polychaete abundance was positively correlated with the bottom water temperature (r=0.456, P<0.01). Meiobenthos abundance differed significantly among seasons (P<0.05), although no significant difference among stations and the interaction of station × season was detected by two-way ANOVA. In terms of vertical distribution, most of the meiobenthos was found in the surface layer of sediment. This pattern was apparent for nematodes and copepods, but a vertical distribution pattern for polychaetes was not as obvious. Based on the biotic indices and analyses of their correlations and variance, the diversity of this community was likely to be influenced by

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.

Current land bird distribution and trends in population abundance between 1982 and 2012 on Rota, Mariana Islands

Science.gov (United States)

Camp, Richard J.; Brinck, Kevin W.; Gorresen, P. Marcos; Amidon, Fred A.; Radley, Paul M.; Berkowitz, S. Paul; Banko, Paul C.

2015-01-01

The western Pacific island of Rota is the fourth largest human-inhabited island in the Mariana archipelago and designated an Endemic Bird Area. Between 1982 and 2012, 12 point-transect distance-sampling surveys were conducted to assess bird population status. Surveys did not consistently sample the entire island; thus, we used a ratio estimator to estimate bird abundances in strata not sampled during every survey. Trends in population size were reliably estimated for 11 of 13 bird species, and 7 species declined over the 30-y time series, including the island collared-dove Streptopelia bitorquata, white-throated ground-dove Gallicolumba xanthonura, Mariana fruit-dove Ptilinopus roseicapilla, collared kingfisher Todiramphus chloris orii, Micronesian myzomela Myzomela rubratra, black drongo Dicrurus macrocercus, and Mariana crow Corvus kubaryi. The endangered Mariana crow (x̄  =  81 birds, 95% CI 30–202) declined sharply to fewer than 200 individuals in 2012, down from 1,491 birds in 1982 (95% CI  =  815–3,115). Trends increased for white tern Gygis alba, rufous fantail Rhipidura rufifrons mariae, and Micronesian starling Aplonis opaca. Numbers of the endangered Rota white-eye Zosterops rotensis declined from 1982 to the late 1990s but returned to 1980s levels by 2012, resulting in an overall stable trend. Trends for the yellow bittern Ixobrychus sinensis were inconclusive. Eurasian tree sparrow Passer montanus trends were not assessed; however, their numbers in 1982 and 2012 were similar. Occupancy models of the 2012 survey data revealed general patterns of land cover use and detectability among 12 species that could be reliably modeled. Occupancy was not assessed for the Eurasian tree sparrow because of insufficient detections. Based on the 2012 survey, bird distribution and abundance across Rota revealed three general patterns: 1) range restriction, including Mariana crow, Rota white-eye, and Eurasian tree sparrow; 2) widespread distribution, low

Ichthyoplankton distribution and abundance in the northern Todos os Santos and Camamu Bays, Bahia State - Brazil

Directory of Open Access Journals (Sweden)

Mario Katsuragawa

2011-03-01

Full Text Available The occurrence, distribution and abundance of ichthyoplankton in Todos os Santos and Camamu Bays were analyzed based on four samplings (winter 2003, summer 2003, winter 2004 and summer 2005. Samples were obtained by surface horizontal hauls, using a 200-µm mesh conical-cylinder plankton net. The distribution and abundance of eggs indicate a remarkable seasonal and annual variation of spawning activity in the region, especially when the two summer campaigns are compared. In summer 2003 the highest quantitative values were recorded, especially for Camamu, where the maximum reached 106.56 eggs.m-3, with an overall average of 43.46 eggs.m-3 for the two areas. In summer 2005 values were relatively low, the overall average being 3.49 eggs.m-3. The larval taxonomic composition is characterized by the predominance of gobiids, with small variation from summer to winter. Considering all the campaigns and samplings undertaken in both areas, larvae of 11 families were identified: Engraulidae, Clupeidae, Mugilidae, Atherinopsidae, Hemiramphidae, Syngnathidae, Blenniidae, Carangidae, Gobiidae, Achiridae and Tetraodontidae.O ictioplâncton coletado ao norte da baía de Todos os Santos e na baía de Camamu (Inverno 2003, Verão 2003, Inverno 2004 e Verão 2005 é analisado de forma comparativa. As amostras foram obtidas com redes de plâncton do tipo cônica-cilíndrica de 200 µm de malhagem, em arrastos horizontais de subsuperfície. Os resultados sobre a distribuição e abundância de ovos de peixes sugerem uma ampla variação sazonal e anual da desova. Entre os verões as diferenças foram especialmente visíveis, sendo observados no primeiro verão (dez/03 os maiores valores quantitativos do projeto (máximo = 106,56 ovos.m-3; média = 43,46 ovos.m-3, enquanto que no segundo verão (jan/05 os valores foram em geral baixos (média geral = 3,49 ovos.m-3. A composição taxonômica é caracterizada pela predominância de gobiídeos, com pequenas varia

Characterizing the Heavy Elements in Globular Cluster M22 and an Empirical s-process Abundance Distribution Derived from the Two Stellar Groups

Science.gov (United States)

Roederer, I. U.; Marino, A. F.; Sneden, C.

2011-11-01

We present an empirical s-process abundance distribution derived with explicit knowledge of the r-process component in the low-metallicity globular cluster M22. We have obtained high-resolution, high signal-to-noise spectra for six red giants in M22 using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory. In each star we derive abundances for 44 species of 40 elements, including 24 elements heavier than zinc (Z = 30) produced by neutron-capture reactions. Previous studies determined that three of these stars (the "r+s group") have an enhancement of s-process material relative to the other three stars (the "r-only group"). We confirm that the r+s group is moderately enriched in Pb relative to the r-only group. Both groups of stars were born with the same amount of r-process material, but s-process material was also present in the gas from which the r+s group formed. The s-process abundances are inconsistent with predictions for asymptotic giant branch (AGB) stars with M <= 3 M ⊙ and suggest an origin in more massive AGB stars capable of activating the 22Ne(α,n)25Mg reaction. We calculate the s-process "residual" by subtracting the r-process pattern in the r-only group from the abundances in the r+s group. In contrast to previous r- and s-process decompositions, this approach makes no assumptions about the r- and s-process distributions in the solar system and provides a unique opportunity to explore s-process yields in a metal-poor environment. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Distribution and abundance of marine debris along the coast of karachi (arabian sea), pakistan

International Nuclear Information System (INIS)

Qari, R.; Shaffat, M.

2015-01-01

This study reports the first assessment of distribution and abundance of marine debris along the coast of Karachi (Arabian Sea), Pakistan. The quadrate method was used for estimating the debris material. Total 40 quadrates were made for collecting the debris on 4 beaches: Sandspit, Buleji, Paradise Point and Korangi Creek in the year of 2012. Nine different types of debris comprising of plastics, glasses, thermopore, clothing, rubber, paper, pot pieces and cigarette filters were collected. The study revealed that, plastic was found in high quantity at all four beaches of Karachi. Other most common items were as follow: plastic at Paradise Point and Sandspit; pot pieces at Korangi Creek and rubber at Buleji. A total weight of 12277.45 g debris was recorded during the whole study period. It was also noted that Paradise Point is the dirtiest beach (5612.6 g) when compared with other studied beaches. (author)

The distribution, composition and abundance of fish species in two ...

African Journals Online (AJOL)

Fish composition and abundance of two Gold mine reservoir were investigated between May, 2008 and May, 2009. Seven fish families comprising of twelve species of fish were caught during the period of study. The families of fish caught included Anabantidae, Channidae, Clariidae, Cichlidae, Melanopluridae, Mormyridae ...

Emission depth distribution function of Al 2s photoelectrons in Al.sub.2./sub.O.sub.3./sub..

Czech Academy of Sciences Publication Activity Database

Hucek, Stanislav; Zemek, Josef; Jablonski, A.; Tilinin, L. S.

2000-01-01

Roč. 7, 1&2 (2000), s. 109-114 ISSN 0218-625X R&D Projects: GA ČR GA202/95/0032 Grant - others:GA UK(CZ) 33 Institutional research plan: CEZ:AV0Z6022909; CEZ:AV0Z1010914 Keywords : depth distribution function * DDF * Monte Carlo simulation * Beer - Lambert law * Boltzmann kinetic equation * straight line approximation * SLA Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.886, year: 2000

Origin and spatial distribution of gas at seismogenic depths of the San Andreas Fault from drill-mud gas analysis

International Nuclear Information System (INIS)

Wiersberg, Thomas; Erzinger, Joerg

2008-01-01

Data are presented on the molecular composition of drill-mud gas from the lower sedimentary section (1800-3987 m) of the SAFOD (San Andreas Fault Observatory at Depth) Main Hole measured on-line during drilling, as well as C and H isotope data from off-line mud gas samples. Hydrocarbons, H 2 and CO 2 are the most abundant non-atmospheric gases in drill-mud when drilling seismogenic zones. Gas influx into the well at depth is related to the lithology and permeability of the drilled strata: larger formation gas influx was detected when drilling through organic-rich shales and permeable sandstones. The SAF (San Andreas Fault), encountered between approximately 3100 m and 3450 m borehole depth, is generally low in gas, but is encompassed by two gas-rich zones (2700-2900 m and below 3550 m) at the fault margins with enhanced 222 Rn activities and distinct gas compositions. Within the fault, two interstratified gas-rich lenses (3150-3200 m and 3310-3340 m) consist of CO 2 and hydrocarbons (upper zone), but almost exclusively of hydrocarbons (lower zone). The isotopic composition indicates an organic source of hydrocarbons and CO 2 in the entire sedimentary section of the well. Hydrocarbons in sedimentary strata are partly of microbial origin down to ∼2500 m borehole depth. The contribution of thermogenic gas increases between ∼2500 m and 3200 m. Below ∼3200 m, hydrocarbons fully derive from thermal degradation of organic matter. The lack of H 2 in the center of the fault and the high concentration of H 2 in the fractured zones at the fault margins are consistent with H 2 formation by interaction of water with fresh silica mineral surfaces generated by tectonic activities, however, this needs to be verified by laboratory experiments. Based on these studies, it is concluded that the fault zone margins consist of strata with enhanced permeability, separated by a low-permeability fault center

Atom depth analysis delineates mechanisms of protein intermolecular interactions

International Nuclear Information System (INIS)

Alocci, Davide; Bernini, Andrea; Niccolai, Neri

2013-01-01

Highlights: •3D atom depth analysis is proposed to identify different layers in protein structures. •Amino acid contents for each layers have been analyzed for a large protein dataset. •Charged amino acids in the most external layer are present at very different extents. •Atom depth indexes of K residues reflect their side chains flexibility. •Mobile surface charges can be responsible for long range protein–protein recognition. -- Abstract: The systematic analysis of amino acid distribution, performed inside a large set of resolved protein structures, sheds light on possible mechanisms driving non random protein–protein approaches. Protein Data Bank entries have been selected using as filters a series of restrictions ensuring that the shape of protein surface is not modified by interactions with large or small ligands. 3D atom depth has been evaluated for all the atoms of the 2,410 selected structures. The amino acid relative population in each of the structural layers formed by grouping atoms on the basis of their calculated depths, has been evaluated. We have identified seven structural layers, the inner ones reproducing the core of proteins and the outer one incorporating their most protruding moieties. Quantitative analysis of amino acid contents of structural layers identified, as expected, different behaviors. Atoms of Q, R, K, N, D residues are increasingly more abundant in going from core to surfaces. An opposite trend is observed for V, I, L, A, C, and G. An intermediate behavior is exhibited by P, S, T, M, W, H, F and Y. The outer structural layer hosts predominantly E and K residues whose charged moieties, protruding from outer regions of the protein surface, reorient free from steric hindrances, determining specific electrodynamics maps. This feature may represent a protein signature for long distance effects, driving the formation of encounter complexes and the eventual short distance approaches that are required for protein�

AN IN-DEPTH STUDY OF THE ABUNDANCE PATTERN IN THE HOT INTERSTELLAR MEDIUM IN NGC 4649

International Nuclear Information System (INIS)

Loewenstein, Michael; Davis, David S.

2012-01-01

We present our X-ray imaging spectroscopic analysis of data from deep Suzaku and XMM-Newton Observatory exposures of the Virgo Cluster elliptical galaxy NGC 4649 (M60), focusing on the abundance pattern in the hot interstellar medium (ISM). All measured elements show a radial decline in abundance, with the possible exception of O. We construct steady-state solutions to the chemical evolution equations that include infall in addition to stellar mass return and Type Ia supernova (SNIa) enrichment, and consider recently published SNIa yields. By adjusting a single model parameter to obtain a match to the global abundance pattern in NGC 4649, we infer that introduction of subsolar metallicity external gas has reduced the overall ISM metallicity and diluted the effectiveness of SNIa to skew the pattern toward low α/Fe ratios, and estimate the combination of SNIa rate and level of dilution. Evidently, newly introduced gas is heated as it is integrated into, and interacts with, the hot gas that is already present. These results indicate a complex flow and enrichment history for NGC 4649, reflecting the continual evolution of elliptical galaxies beyond the formation epoch. The heating and circulation of accreted gas may help reconcile this dynamic history with the mostly passive evolution of elliptical stellar populations. In an Appendix, we examine the effects of the recent updated atomic database AtomDB in spectral fitting of thermal plasmas with hot ISM temperatures in the elliptical galaxy range.

Where to nest? Ecological determinants of chimpanzee nest abundance and distribution at the habitat and tree species scale.

Science.gov (United States)

Carvalho, Joana S; Meyer, Christoph F J; Vicente, Luis; Marques, Tiago A

2015-02-01

Conversion of forests to anthropogenic land-uses increasingly subjects chimpanzee populations to habitat changes and concomitant alterations in the plant resources available to them for nesting and feeding. Based on nest count surveys conducted during the dry season, we investigated nest tree species selection and the effect of vegetation attributes on nest abundance of the western chimpanzee, Pan troglodytes verus, at Lagoas de Cufada Natural Park (LCNP), Guinea-Bissau, a forest-savannah mosaic widely disturbed by humans. Further, we assessed patterns of nest height distribution to determine support for the anti-predator hypothesis. A zero-altered generalized linear mixed model showed that nest abundance was negatively related to floristic diversity (exponential form of the Shannon index) and positively with the availability of smaller-sized trees, reflecting characteristics of dense-canopy forest. A positive correlation between nest abundance and floristic richness (number of plant species) and composition indicated that species-rich open habitats are also important in nest site selection. Restricting this analysis to feeding trees, nest abundance was again positively associated with the availability of smaller-sized trees, further supporting the preference for nesting in food tree species from dense forest. Nest tree species selection was non-random, and oil palms were used at a much lower proportion (10%) than previously reported from other study sites in forest-savannah mosaics. While this study suggests that human disturbance may underlie the exclusive arboreal nesting at LCNP, better quantitative data are needed to determine to what extent the construction of elevated nests is in fact a response to predators able to climb trees. Given the importance of LCNP as refuge for Pan t. verus our findings can improve conservation decisions for the management of this important umbrella species as well as its remaining suitable habitats. © 2014 Wiley Periodicals, Inc.

Variation in rank abundance replicate samples and impact of clustering

NARCIS (Netherlands)

Neuteboom, J.H.; Struik, P.C.

2005-01-01

Calculating a single-sample rank abundance curve by using the negative-binomial distribution provides a way to investigate the variability within rank abundance replicate samples and yields a measure of the degree of heterogeneity of the sampled community. The calculation of the single-sample rank

Depth to the bottom of magnetic sources (DBMS) from aeromagnetic data of Central India using modified centroid method for fractal distribution of sources

Science.gov (United States)

Bansal, A. R.; Anand, S. P.; Rajaram, Mita; Rao, V. K.; Dimri, V. P.

2013-09-01

The depth to the bottom of the magnetic sources (DBMS) has been estimated from the aeromagnetic data of Central India. The conventional centroid method of DBMS estimation assumes random uniform uncorrelated distribution of sources and to overcome this limitation a modified centroid method based on scaling distribution has been proposed. Shallower values of the DBMS are found for the south western region. The DBMS values are found as low as 22 km in the south west Deccan trap covered regions and as deep as 43 km in the Chhattisgarh Basin. In most of the places DBMS are much shallower than the Moho depth, earlier found from the seismic study and may be representing the thermal/compositional/petrological boundaries. The large variation in the DBMS indicates the complex nature of the Indian crust.

Quantifying changes in abundance, biomass and spatial distribution of Northeast Atlantic (NEA) mackerel (Scomber scombrus) in the Nordic Seas from 2007 to 2014

DEFF Research Database (Denmark)

Nøttestad, Leif; Utne, Kjell Rong; Óskarsson, Gudmundur .J.

2016-01-01

The Northeast Atlantic (NEA) mackerel (Scomber scombrus) is a widely distributed pelagic fish species that plays a key role in the marine ecosystem. In recent years, there has been a large fishery targeting mackerel in the NEA. At the same time as the geographic range of the mackerel fishery has...... on coordinated and standardized swept-area surface trawling in July–August from IESSNS increased from 1.96 million t [relative standard error (RSE) ¼ 30.35%] in 2007 to 8.77 million t (RSE ¼ 7.95%) in 2014. Simultaneously, the mackerel stock expanded its geographic range during the feeding season from 1......%). Furthermore, evaluation of the performance of the estimated abundance indices by age for this time-series, based on internal consistency and catch curves, suggest that the abundance indices of ages 3–12 track the temporal variation in abundance reasonably, and thus is applicable for stock assessments...

Ultraviolet-B radiation influences the abundance and distribution of phylloplane fungi on pedunculate oak (Quercus robur)

International Nuclear Information System (INIS)

Newsham, K.K.; Low, M.N.R.; McLeod, A.R.; Greenslade, P.D.; Emmett, B.A.

1997-01-01

influence the distribution of fungi on leaf surfaces and that future increases in u.v.-B radiation will directly affect the abundances of specific phylloplane fungi. (author)

Stellar Oxygen Abundances

Science.gov (United States)

King, Jeremy

1994-04-01

This dissertation addresses several issues concerning stellar oxygen abundances. The 7774 {\\AA} O I triplet equivalent widths of Abia & Rebolo [1989, AJ, 347, 186] for metal-poor dwarfs are found to be systematically too high. I also argue that current effective temperatures used in halo star abundance studies may be ~150 K too low. New color-Teff relations are derived for metal-poor stars. Using the revised Teff values and improved equivalent widths for the 7774A O I triplet, the mean [O/Fe] ratio for a handful of halo stars is found to be +0.52 with no dependence on Teff or [Fe/H]. Possible cosmological implications of the hotter Teff scale are discussed along with additional evidence supporting the need for a higher temperature scale for metal-poor stars. Our Teff scale leads to a Spite Li plateau value of N(Li)=2.28 +/- 0.09. A conservative minimal primordial value of N(Li)=2.35 is inferred. If errors in the observations and models are considered, consistency with standard models of Big Bang nucleosynthesis is still achieved with this larger Li abundance. The revised Teff scale raises the observed B/Be ratio of HD 140283 from 10 to 12, making its value more comfortably consistent with the production of the observed B and Be by ordinary spallation. Our Teff values are found to be in good agreement with values predicted from both the Victoria and Yale isochrone color-Teff relations. Thus, it appears likely that no changes in globular cluster ages would result. Next, we examine the location of the break in the [O/Fe] versus [Fe/H] plane in a quantitative fashion. Analysis of a relatively homogeneous data set does not favor any unique break point in the range -1.7 /= -3), in agreement with the new results for halo dwarfs. We find that the gap in the observed [O/H] distribution, noted by Wheeler et al. [1989, ARAA, 27, 279], persists despite the addition of more O data and may betray the occurrence of a hiatus in star formation between the end of halo formation and

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Science.gov (United States)

Sánchez-Menguiano, L.; Sánchez, S. F.; Pérez, I.; Ruiz-Lara, T.; Galbany, L.; Anderson, J. P.; Krühler, T.; Kuncarayakti, H.; Lyman, J. D.

2018-02-01

We characterised the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allowed us to detect 14345 H II regions with the same image quality as with photometric data, avoiding any dilution effect. We developed a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10), or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence in the case of the outer flattening. We find that the inner drop appears always around 0.5 re, while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope in the sample of αO/H =-0.10 ± 0.03 dex /re. This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale ("the abundance scale length", rO/H) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop ( 0.5 rO/H) and the outer flattening ( 1.5 rO/H). Finally, we find no significant dependence of the dispersion around the negative gradient with any property of the galaxies, with values compatible with the uncertainties associated with the derivation of the abundances.

Measurements of the gas temperature and iron abundance distribution in the Coma Cluster

International Nuclear Information System (INIS)

Hughes, J.P.; Gorenstein, P.; Fabricant, D.

1988-01-01

The medium energy X-ray detectors onboard the EXOSAT Observatory have been used to determine the gas temperature at several positions in the Coma Cluster of galaxies. Evidence is found at greater than 95 percent confidence for a higher temperature in the center of the cluster than in a position approximately 45 arcmin off-center. No difference in iron abundance is observed between the center and off-center regions and the equilibrium model for the distribution of elements in the Coma Cluster of Abramopoulos, Chanan, and Ku can be rejected with greater than 99.5 percent confidence, in favor of a model with more uniform composition. A phenomenological model is presented of the Coma Cluster, which is consistent with the data presented here, as well as the imaging data from the Einstein Observatory and the Tenma X-ray spectrum. The model has a central isothermal region of temperature about 9 keV extending to about 25 arcmin (about 1 Mpc). Beyond this radius the temperature falls as a polytrope with index about 1.6. 36 references

A dynamic optimization model of the diel vertical distribution of a pelagic planktivorous fish

Science.gov (United States)

Rosland, Rune; Giske, Jarl

A stochastic dynamic optimization model for the diel depth distribution of juveniles and adults of the mesopelagic planktivore Maurolicus muelleri (Gmelin) is developed and used for a winter situation. Observations from Masfjorden, western Norway, reveal differences in vertical distribution, growth and mortality between juveniles and adults in January. Juveniles stay within the upper 100m with high feeding rates, while adults stay within the 100-150m zone with very low feeding rates during the diel cycle. The difference in depth profitability is assumed to be caused by age-dependent processes, and are calculated from a mechanistic model for visual feeding. The environment is described as a set of habitats represented by discrete depth intervals along the vertical axis, differing with respect to light intensity, food abundance, predation risk and temperature. The short time interval (24h) allows fitness to be linearly related to growth (feeding), assuming that growth increases the future reproductive output of the fish. Optimal depth position is calculated from balancing feeding opportunity against mortality risk, where the fitness reward gained by feeding is weighted against the danger of being killed by a predator. A basic run is established, and the model is validated by comparing predictions and observations. The sensitivity for different parameter values is also tested. The modelled vertical distributions and feeding patterns of juvenile and adult fish correspond well with the observations, and the assumption of age differences in mortality-feeding trade-offs seems adequate to explain the different depth profitability of the two age groups. The results indicate a preference for crepuscular feeding activity of the juveniles, and the vertical distribution of zooplankton seems to be the most important environmental factor regulating the adult depth position during the winter months in Masfjorden.

The Abundance of Large Arcs From CLASH

Science.gov (United States)

Xu, Bingxiao; Postman, Marc; Meneghetti, Massimo; Coe, Dan A.; Clash Team

2015-01-01

We have developed an automated arc-finding algorithm to perform a rigorous comparison of the observed and simulated abundance of large lensed background galaxies (a.k.a arcs). We use images from the CLASH program to derive our observed arc abundance. Simulated CLASH images are created by performing ray tracing through mock clusters generated by the N-body simulation calibrated tool -- MOKA, and N-body/hydrodynamic simulations -- MUSIC, over the same mass and redshift range as the CLASH X-ray selected sample. We derive a lensing efficiency of 15 ± 3 arcs per cluster for the X-ray selected CLASH sample and 4 ± 2 arcs per cluster for the simulated sample. The marginally significant difference (3.0 σ) between the results for the observations and the simulations can be explained by the systematically smaller area with magnification larger than 3 (by a factor of ˜4) in both MOKA and MUSIC mass models relative to those derived from the CLASH data. Accounting for this difference brings the observed and simulated arc statistics into full agreement. We find that the source redshift distribution does not have big impact on the arc abundance but the arc abundance is very sensitive to the concentration of the dark matter halos. Our results suggest that the solution to the "arc statistics problem" lies primarily in matching the cluster dark matter distribution.

Seed drill instrumentation for spatial coulter depth measurements

DEFF Research Database (Denmark)

Kirkegaard Nielsen, Søren; Munkholm, Lars Juhl; Lamandé, Mathieu

2017-01-01

coulter depth varied up to ±5 mm between the blocks. In addition, significant depth variations between the individual coulters were found. The mean depths varied between −14.2 and −25.9 mm for the eleven coulters. The mean shallowest coulter depth (−14.2 mm) was measured for the coulter running...... in the wheel track of the tractor. The power spectral densities (distribution) of the coulter depth oscillation frequencies showed that the majority of oscillations occurred below 0.5 Hz without any natural vibration frequency. The study concluded that the instrumentation concept was functional for on...

Abundance and Summer Distribution of a Local Stock of Black Sea Bottlenose Dolphins, Tursiops truncatus (Cetacea, Delphinidae, in Coastal Waters near Sudak (Ukraine, Crimea