Sample records for geukensia demissa dillwyn

  1. Effect of field exposure to 38-year-old residual petroleum hydrocarbons on growth, condition index, and filtration rate of the ribbed mussel, Geukensia demissa

    International Nuclear Information System (INIS)

    Culbertson, Jennifer B.; Valiela, Ivan; Olsen, Ylva S.; Reddy, Christopher M.


    In September 1969, the Florida barge spilled 700,000 L of No. 2 fuel oil into the salt marsh sediments of Wild Harbor, MA. Today a substantial amount, approximately 100 kg, of moderately degraded petroleum remains within the sediment and along eroding creek banks. The ribbed mussels, Geukensia demissa, which inhabit the salt marsh creek bank, are exposed to the spilled oil. Examination of short-term exposure was done with transplantation of G. demissa from a control site, Great Sippewissett marsh, into Wild Harbor. We also examined the effects of long-term exposure with transplantation of mussels from Wild Harbor into Great Sippewissett. Both the short- and long-term exposure transplants exhibited slower growth rates, shorter mean shell lengths, lower condition indices, and decreased filtration rates. The results add new knowledge about long-term consequences of spilled oil, a dimension that should be included when assessing oil-impacted areas and developing management plans designed to restore, rehabilitate, or replace impacted areas. - Mussels exposed to petroleum in transplant and field experiments exhibited significant long-term effects


    Increased residential development in coastal watersheds has led to increases in anthropogenic nitrogen inputs into estuaries. Sessile bivalves are good candidate organisms to examine animal condition in nutrient-enriched areas because they contribute significantly to energy flow...

  3. Chemical and ancillary data associated with bed sediment, young of year Bluefish (Pomatomus saltatrix) tissue, and mussel (Mytilus edulis and Geukensia demissa) tissue collected after Hurricane Sandy in bays and estuaries of New Jersey and New York, 2013–14 (United States)

    Smalling, Kelly L.; Deshpande, Ashok D.; Blazer, Vicki; Galbraith, Heather S.; Dockum, Bruce W.; Romanok, Kristin M.; Colella, Kaitlyn; Deetz, Anna C.; Fisher, Irene J.; Imbrigiotta, Thomas E.; Sharack, Beth; Summer, Lisa; Timmons, DeMond; Trainor, John J.; Wieczorek, Daniel; Samson, Jennifer; Reilly, Timothy J.; Focazio, Michael J.


    This report describes the methods and data associated with a reconnaissance study of young of year bluefish and mussel tissue samples as well as bed sediment collected as bluefish habitat indicators during August 2013–April 2014 in New Jersey and New York following Hurricane Sandy in October 2012. This study was funded by the Disaster Relief Appropriations Act of 2013 (PL 113-2) and was conducted by the U.S. Geological Survey (USGS) in cooperation with the National Oceanic and Atmospheric Administration (NOAA).

  4. Biología reproductiva, crecimiento y dieta del caracol ciego Buccinanops cochlidium (Dillwyn, 1817) (Gastropoda: Nassariidae) en el golfo San José, Patagonia Argentina


    Averbuj, Andrés


    El genero Buccinanops (dŽOrbigny, 1841) (Caenogastropoda, Nassariidae) es endémico del océano Atlántico sudoccidental, y su nombre significa "sin ojos", debido a su ausencia en los adultos. El caracol Buccinanops cochlidium (Dillwyn, 1817) se distribuye en aguas someras de las costas desde el paralelo 19ºS (Brasil) hasta el golfo San Matias (43º44ŽS) en Argentina, a profundidades entre 5 y 50m. En el golfo San José habita aguas someras en fondos de sedimento fino. Se realizo un estudio de la ...

  5. Phylogenetic analysis of Bangiadulcis atropurpurea (A. Roth W.A. Nelson and Bangia fuscopurpurea (Dillwyn Lyngbye (Bangiales, Rhodophyta in Taiwan

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    Chou Jui-Yu


    Full Text Available Samples of the freshwater red algae, Bangiadulcis atropurpurea, collected from the mountain waterfalls and its close species, Bangia fuscopurpurea, collected from coasts, were phylogenetically analyzed. The sequences of the rbcL gene and RuBisCO spacer region of the freshwater Bangiadulcis atropurpurea species were identical or similar to those of B. atropurpurea from Japan, North America and Europe. This result indicated that the freshwater Bangiadulcis species from Taiwan shared a common ancestor with the three above-mentioned populations and formed a distinct clade from the marine Bangia species in the phylogenetic trees. It is suggested that all the previous records on marine Bangia species should be revised and the name B. fuscopurpurea be used for the marine species in Taiwan. In this study, the freshwater alga B. atropurpurea presents a new record in the algal flora of Taiwan. This finding is important for the protection of the biodiversity of red algal flora, and provides useful information on the ecological conservation of the species in Taiwan.

  6. Hemigrapsus sanguineus in Long Island salt marshes: experimental evaluation of the interactions between an invasive crab and resident ecosystem engineers

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    Bradley J. Peterson


    Full Text Available The invasive Asian shore crab, Hemigrapsus sanguineus, has recently been observed occupying salt marshes, a novel environment for this crab species. As it invades this new habitat, it is likely to interact with a number of important salt marsh species. To understand the potential effects of H. sanguineus on this ecosystem, interactions between this invasive crab and important salt marsh ecosystem engineers were examined. Laboratory experiments demonstrated competition for burrows between H. sanguineus and the native fiddler crab, Uca pugilator. Results indicate that H. sanguineus is able to displace an established fiddler crab from its burrow. Feeding experiments revealed that the presence of H. sanguineus has a significantly negative impact on the number as well as the biomass of ribbed mussels (Geukensia demissa consumed by the green crab, Carcinus maenas, although this only occurred at high predator densities. In addition, when both crabs foraged together, there was a significant shift in the size of mussels consumed. These interactions suggests that H. sanguineus may have long-term impacts and wide-ranging negative effects on the saltmarsh ecosystem.

  7. Hemigrapsus sanguineus in Long Island salt marshes: experimental evaluation of the interactions between an invasive crab and resident ecosystem engineers. (United States)

    Peterson, Bradley J; Fournier, Alexa M; Furman, Bradley T; Carroll, John M


    The invasive Asian shore crab, Hemigrapsus sanguineus, has recently been observed occupying salt marshes, a novel environment for this crab species. As it invades this new habitat, it is likely to interact with a number of important salt marsh species. To understand the potential effects of H. sanguineus on this ecosystem, interactions between this invasive crab and important salt marsh ecosystem engineers were examined. Laboratory experiments demonstrated competition for burrows between H. sanguineus and the native fiddler crab, Uca pugilator. Results indicate that H. sanguineus is able to displace an established fiddler crab from its burrow. Feeding experiments revealed that the presence of H. sanguineus has a significantly negative impact on the number as well as the biomass of ribbed mussels (Geukensia demissa) consumed by the green crab, Carcinus maenas, although this only occurred at high predator densities. In addition, when both crabs foraged together, there was a significant shift in the size of mussels consumed. These interactions suggests that H. sanguineus may have long-term impacts and wide-ranging negative effects on the saltmarsh ecosystem.

  8. Minimal incorporation of Deepwater Horizon oil by estuarine filter feeders

    International Nuclear Information System (INIS)

    Fry, Brian; Anderson, Laurie C.


    Highlights: • Oil from the Deepwater Horizon oil spill entered Louisiana bays in mid-2010. • Oil was used minimally (<1%) in diets of mussels and barnacles. • Also, oil did not enhance planktonic respiration rates. • Use of oil carbon was relatively small in these productive estuarine food webs. - Abstract: Natural abundance carbon isotope analyses are sensitive tracers for fates and use of oil in aquatic environments. Use of oil carbon in estuarine food webs should lead to isotope values approaching those of oil itself, −27‰ for stable carbon isotopes reflecting oil origins and −1000‰ for carbon-14 reflecting oil age. To test for transfer of oil from the 2010 Deepwater Horizon spill into estuarine food webs, filter-feeding barnacles (Balanus sp.) and marsh mussels (Geukensia demissa) were collected from Louisiana estuaries near the site of the oil spill. Carbon-14 analyses of these animals from open waters and oiled marshes showed that oil use was <1% and near detection limits estimated at 0.3% oil incorporation. Respiration studies showed no evidence for enhanced microbial activity in bay waters. Results are consistent with low dietary impacts of oil for filter feeders and little overall impact on respiration in the productive Louisiana estuarine systems

  9. Evaluation of Rapid, Early Warning Approaches to Track Shellfish Toxins Associated with Dinophysis and Alexandrium Blooms

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    Theresa K. Hattenrath-Lehmann


    Full Text Available Marine biotoxin-contaminated seafood has caused thousands of poisonings worldwide this century. Given these threats, there is an increasing need for improved technologies that can be easily integrated into coastal monitoring programs. This study evaluates approaches for monitoring toxins associated with recurrent toxin-producing Alexandrium and Dinophysis blooms on Long Island, NY, USA, which cause paralytic and diarrhetic shellfish poisoning (PSP and DSP, respectively. Within contrasting locations, the dynamics of pelagic Alexandrium and Dinophysis cell densities, toxins in plankton, and toxins in deployed blue mussels (Mytilus edulis were compared with passive solid-phase adsorption toxin tracking (SPATT samplers filled with two types of resin, HP20 and XAD-2. Multiple species of wild shellfish were also collected during Dinophysis blooms and used to compare toxin content using two different extraction techniques (single dispersive and double exhaustive and two different toxin analysis assays (liquid chromatography/mass spectrometry and the protein phosphatase inhibition assay (PP2A for the measurement of DSP toxins. DSP toxins measured in the HP20 resin were significantly correlated (R2 = 0.7–0.9, p < 0.001 with total DSP toxins in shellfish, but were detected more than three weeks prior to detection in deployed mussels. Both resins adsorbed measurable levels of PSP toxins, but neither quantitatively tracked Alexandrium cell densities, toxicity in plankton or toxins in shellfish. DSP extraction and toxin analysis methods did not differ significantly (p > 0.05, were highly correlated (R2 = 0.98–0.99; p < 0.001 and provided complete recovery of DSP toxins from standard reference materials. Blue mussels (Mytilus edulis and ribbed mussels (Geukensia demissa were found to accumulate DSP toxins above federal and international standards (160 ng g−1 during Dinophysis blooms while Eastern oysters (Crassostrea virginica and soft shell clams (Mya

  10. New synonyms and combinations in Asiatic Ardisia (Myrsinaceae)

    NARCIS (Netherlands)

    Ming, Hu Chi


    Studies on the genus Ardisia Sw. for Flora Malesiana have led to the reduction of 95 taxa to synonymy, seven species to the infraspecific level: A. demissa Miq. var. bambusetorum (King & Gamble) C.M. Hu, A. polysticta Miq. subsp. punctipelata (Merr.) C.M. Hu, A. ternatensis Scheff. var. forstenii

  11. Carex flava agg. (section Ceratocystis, Cyperaceae in Poland: taxonomy, morphological variation, and soil conditions

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    Więcław Helena


    Full Text Available Sedges of Carex flava agg., typical of moist or wet habitats, are difficult to classify because of a lack of clear-cut morphological differences between them and the existence of numerous hybrids. This monograph presents results of research conducted in 2007-2012 in various parts of Poland. The plant material consisted of 1852 living specimens of Carex flava agg., collected from 80 localities, and dried specimens from 26 herbaria and from 7 private collections. The analysis involved 45 morphological characters (34 quantitative and 11 qualitative and 9 soil parameters. Univariate, bivariate, and multivariate statistical methods were used to process the data. The results confirm the taxonomic classification dividing the C. flava group into 4 species: C. flava s.s., C. lepidocarpa, C. demissa, and C. viridula. This classification is based on (i a high observed level of morphological separation of these taxa, resulting mostly from differences in generative characters, i.e. length of the utricle and its beak, and percentage ratio of beak length to total utricle length; (ii integrity of the taxa at the sites where they coexist, although some intermediate forms resulting from hybridization are also present; (iii habitat preferences of the taxa, especially the preference of C. lepidocarpa for calcareous sites and of C. demissa for slightly acidic soils. Thus in Poland the analysed taxa are morphologically well-defined and show clear ecological preferences. Continuous variation of morphological characters was observed among specimens of C. viridula, so it is not justifiable to distinguish its subspecies (sometimes classified even as separate species, described previously in literature. Consequently, the 2 subgroups of C. viridula were treated as local variants (i.e. varieties: var. viridula and var. pulchella, considering their different habitat requirements. Additionally, 5 hybrids were distinguished within C. flava agg.: C. ×alsatica [= C. demissa

  12. Healthy eating design guidelines for school architecture. (United States)

    Huang, Terry T-K; Sorensen, Dina; Davis, Steven; Frerichs, Leah; Brittin, Jeri; Celentano, Joseph; Callahan, Kelly; Trowbridge, Matthew J


    We developed a new tool, Healthy Eating Design Guidelines for School Architecture, to provide practitioners in architecture and public health with a practical set of spatially organized and theory-based strategies for making school environments more conducive to learning about and practicing healthy eating by optimizing physical resources and learning spaces. The design guidelines, developed through multidisciplinary collaboration, cover 10 domains of the school food environment (eg, cafeteria, kitchen, garden) and 5 core healthy eating design principles. A school redesign project in Dillwyn, Virginia, used the tool to improve the schools' ability to adopt a healthy nutrition curriculum and promote healthy eating. The new tool, now in a pilot version, is expected to evolve as its components are tested and evaluated through public health and design research.

  13. Anatomical study on Myoforceps aristatus, an invasive boring bivalve in S.E. Brazilian coast (Mytilidae

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    Luiz Ricardo L. Simone


    Full Text Available The bivalve Myoforceps aristatus (Dillwyn, 1817, also known as Lithophaga aristata, have been recently collected in the coasts of Rio de Janeiro and São Paulo, Brazil; a species that bores shells of other mollusks. This occurrence has been interpreted as an invasion of this species, originally from the Caribbean. The distinguishing character of the species is the posterior extensions of the shell crossing with each other. Because specimens with this character have also been collected in the Pacific Ocean, they all have been considered a single species. However, it is possible that more than one species may be involved in such worldwide distribution. With the objective of providing full information based on Atlantic specimens, a complete anatomical description is provided, which can be used in comparative studies with specimens from other oceans. Additional distinctive features of M. aristatus are the complexity of the incurrent siphon, the kidney opening widely into the supra-branchial chamber (instead of via a nephropore, and the multi-lobed auricle.O bivalve Myoforceps aristatus (Dillwyn, 1817, também conhecido como Lithophaga aristata, tem sido recentemente coletado nas costas do Rio de Janeiro e São Paulo, Brasil; uma espécie que perfura conchas de outros moluscos. Esta ocorrência está sendo interpretada como uma invasão de uma espécie originada do Caribe. O caráter distintivo da espécie é a região posterior da concha, com extensões que se cruzam. Como espécimes com esta característica também têm sido coletados no oceano Pacífico, eles tem sido considerados como pertencentes à mesma espécie. Entretanto, é possível que mais de uma espécie possam estar envolvidas nesta suposta distribuição mundial. Com o objetivo de fornecer informação completa baseada em material do Atlântico, uma descrição anatômica completa é dada, a qual pode ser usada em estudos comparativos com espécimes de outros oceanos. As caracter

  14. Shell occupation by the hermit crab Dardanus insignis (Decapoda, Diogenidae from the north Coast of São Paulo state, Brazil

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    I. F. Frameschi

    Full Text Available Abstract The pattern of shell occupation by the hermit crab Dardanus insignis (Saussure, 1858 from the subtropical region of southeastern coast of Brazil was investigated in the present study. The percentage of shell types that were occupied and the morphometric relationships between hermit crabs and occupied shells were analyzed from monthly collections conducted during two years (from January 1998 to December 1999. Individuals were categorized according to sex and gonadal maturation, weighed and measured with respect to their cephalothoracic shield length (CSL and wet weight (CWW. Shells were measured regarding their aperture width (SAW, dry weight (SDW and internal volume (SIV. A total of 1086 hermit crabs was collected, occupying shells of 11 gastropod species. Olivancillaria urceus (Roding, 1798 was most commonly used by the hermit crab D. insignis, followed by Buccinanops cochlidium (Dillwyn, 1817, and Stramonita haemastoma (Linnaeus, 1767. The highest determination coefficients (r2 > 0.50, p < 0.01 were recorded particularly in the morphometric relationships between CSL vs. CWW and SAW vs. SIV, which are important indication that in this D. insignis population the great majority the animals occupied adequate shells during the two years analysed. The high number of used shell species and relative plasticity in pattern of shell utilization by smaller individuals of D. insignis indicated that occupation is influenced by the shell availability, while larger individuals demonstrated more specialized occupation in Tonna galea (Linnaeus, 1758 shell.

  15. Apparent characteristics and taxonomic study of macroalgae in Pattani Bay

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    Naruemol Pianthumdee


    Full Text Available 2A survey on macroalgae in Pattani Bay was carried out to build up a database resource for the management of algae in the area. From February 2004 to March 2005, samples of macroalgae from 10 sites were randomly collected monthly. Macroalgae were found at 4 sites in the north of the bay, namely Laem Tachi, Lighthouse, Ban Bu Di and Ban Ta Lo Samilae; 3 sites in the east, namely Ban Da To, the Yaring River Mouth and Ban Bang Pu and only one site in the south at Ban Tanyong Lu Lo. Twelve species of 3 divisions of macroalgae were detected. They were Division Cyanophyta, Lyngbya majuscula (Dillwyn Harvey ex Gomont; Division Chlorophyta; Ulva intestinalis Linnaeus, U. pertusa Kjellman and U. reticulata Forsskal, Rhizoclonium riparium (Roth Harvey, R. tortuosum Kutzing, Chaetomorpha crassa (C. Agardh Kutzing and Cladophora sp.; and Division Rhodophyta, namely Gracilaria tenuistipitata Chang et Xia, G. fisheri (Xia et Abbott Abbott, Zhang et Xia, Hypnea spinella (C. Agardh Kutzing and Acanthophora spicifera (Vahl B∅rgesen. Among them, four species were new recordings at Pattani Bay: Lyngbya majuscula, Rhizoclonium riparium, R. tortuosum and Acanthophora spicifera. Most of these seaweeds were found at the east sites in the dry season from February to September 2004 and from January to March 2005. Only a few species could be found in the wet season from November to December 2004.

  16. Integrative taxonomy resolves the cryptic and pseudo-cryptic Radula buccinifera complex (Porellales, Jungermanniopsida, including two reinstated and five new species

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    Matt Renner


    Full Text Available Molecular data from three chloroplast markers resolve individuals attributable to Radula buccinifera in six lineages belonging to two subgenera, indicating the species is polyphyletic as currently circumscribed. All lineages are morphologically diagnosable, but one pair exhibits such morphological overlap that they can be considered cryptic. Molecular and morphological data justify the re-instatement of a broadly circumscribed ecologically variable R. strangulata, of R. mittenii, and the description of five new species. Two species Radula mittenii Steph. and R. notabilis sp. nov. are endemic to the Wet Tropics Bioregion of north-east Queensland, suggesting high diversity and high endemism might characterise the bryoflora of this relatively isolated wet-tropical region. Radula demissa sp. nov. is endemic to southern temperate Australasia, and like R. strangulata occurs on both sides of the Tasman Sea. Radula imposita sp. nov. is a twig and leaf epiphyte found in association with waterways in New South Wales and Queensland. Another species, R. pugioniformis sp. nov., has been confused with Radula buccinifera but was not included in the molecular phylogeny. Morphological data suggest it may belong to subg. Odontoradula. Radula buccinifera is endemic to Australia including Western Australia and Tasmania, and to date is known from south of the Clarence River on the north coast of New South Wales. Nested within R. buccinifera is a morphologically distinct plant from Norfolk Island described as R. anisotoma sp. nov. Radula australiana is resolved as monophyletic, sister to a species occurring in east coast Australian rainforests, and nesting among the R.buccinifera lineages with strong support. The molecular phylogeny suggests several long-distance dispersal events may have occurred. These include two east-west dispersal events from New Zealand to Tasmania and south-east Australia in R. strangulata, one east-west dispersal event from Tasmania to

  17. Lichens

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    Kershaw, K A


    The extreme susceptibility of lichens to air pollution is emphasized in a discussion of the distribution and ecology of the symbionts. The susceptibility is possible due to the indiscriminate and rapid absorption of solutes over the surface of the thallus. Lichens are virtually absent from towns and industrial areas. In an investigation in Kvarntorp, Sweden, the distribution of lichens corresponded markedly with the levels of air pollution, mainly by sulfur dioxide and secondly to the low humidity of the area. There are a few lichens that are tolerant of pollution and occur abundantly in industrial and suburban areas. Lecandra conizaeoides and Stereocaulton pileatum are prevalent in large cities of Great Britain and are early colonizers of trees and brickwork. The apparent preference of lichens for asbestos roofing in polluted areas is related to the high water absorbing power of the substratum and the high base content, with the consequent power of neutralizing acidic atmospheric pollutants. The flora growing on an asbestos tiled roof eight miles from London was examined and revealed four species: S. muralis, L. dispersa, R. demissa, and C. vitellina. The density of the S. muralis was approximately 1/sq m with diameters up to 6 cm. The density of the other species was extremely high, up to 368 apothecia/sq cm for L. dispersa. The figures suggest that the high water absorbing properties and basicity of the asbestos are the factors responsible for the prolific lichen growth. 15 references, 13 figures.

  18. Occurrence of Colombian datura virus in Brugmansia hybrids, Physalis peruviana L. and Solanum muricatum Ait. in Hungary. (United States)

    Salamon, P; Palkovics, L


    Colombian datura virus (CDV) has been found to infect angel trumpets (Brugmansia spp.) frequently and cape gooseberry (Physalis peruviana) and pepino (Solanum muricatum) sporadically in Hungary. A CDV BRG/H isolate was characterized. It had flexuous thread-like virions of about 750 x 12 nm in size. Host range and symptomathological studies revealed its great similarity to authentic CDV isolates. Nicotiana tabacum cultivars and lines resistant to Potato virus Y (PVYN) either genically or transgenically proved highly susceptible to the BRG/H isolate. Tomato (L. esculentum cvs.) was systemically susceptible to this isolate, but some lines of Lycopersicon hirsutum and L. peruvianum turned out to be resistant. Browallia demissa, Ipomoea purpurea, N. megalosiphon and S. scabrum were demonstrated as new experimental hosts of CDV. The BRG/ H isolate proved to be transmissible by the aphid Myzus persicae Sulz. in a non-persistent manner. Potyvirus-specific coat protein (CP) gene sequences of about 1700 bp from angel trumpet, cape gooseberry and pepino plants were amplified by RT-PCR. The cloned BRG/H CP gene showed a 99.12-99.31% identity with other CDV isolates. CDV has been found for the first time to infect naturally cape gooseberry and pepino. Since the botanical genus name of original hosts of CDV has changed from Datura to Brugmansia, we propose to change the virus name from CDV to Angel trumpet mosaic virus (ATMV).

  19. Distribution of alginate and cellulose and regulatory role of calcium in the cell wall of the brown alga Ectocarpus siliculosus (Ectocarpales, Phaeophyceae). (United States)

    Terauchi, Makoto; Nagasato, Chikako; Inoue, Akira; Ito, Toshiaki; Motomura, Taizo


    This work investigated a correlation between the three-dimensional architecture and compound-components of the brown algal cell wall. Calcium greatly contributes to the cell wall integrity. Brown algae have a unique cell wall consisting of alginate, cellulose, and sulfated polysaccharides. However, the relationship between the architecture and the composition of the cell wall is poorly understood. Here, we investigated the architecture of the cell wall and the effect of extracellular calcium in the sporophyte and gametophyte of the model brown alga, Ectocarpus siliculosus (Dillwyn) Lyngbye, using transmission electron microscopy, histochemical, and immunohistochemical studies. The lateral cell wall of vegetative cells of the sporophyte thalli had multilayered architecture containing electron-dense and negatively stained fibrils. Electron tomographic analysis showed that the amount of the electron-dense fibrils and the junctions was different between inner and outer layers, and between the perpendicular and tangential directions of the cell wall. By immersing the gametophyte thalli in the low-calcium (one-eighth of the normal concentration) artificial seawater medium, the fibrous layers of the lateral cell wall of vegetative cells became swollen. Destruction of cell wall integrity was also induced by the addition of sorbitol. The results demonstrated that electron-dense fibrils were composed of alginate-calcium fibrous gels, and electron negatively stained fibrils were crystalline cellulose microfibrils. It was concluded that the spatial arrangement of electron-dense fibrils was different between the layers and between the directions of the cell wall, and calcium was necessary for maintaining the fibrous layers in the cell wall. This study provides insights into the design principle of the brown algal cell wall.

  20. Influence of Black Mangrove Expansion on Salt Marsh Food Web Dynamics in Coastal Louisiana (United States)

    Powell, C.; Baustian, M. M.; Polito, M. J.


    The range of black mangroves (Avicennia germinans) is projected to expand in the northern Gulf of Mexico due to reduced winter freeze events and an increased rate of droughts. The colonization of mangroves in salt marshes alters habitat structure and creates a novel basal carbon source for consumers. This addition may modify trophic linkages and the structure of estuarine food webs. To understand the implications of mangrove expansion on food web dynamics of traditional Spartina alterniflora marshes, two sites in coastal Louisiana with three habitat types, marsh-dominated, mangrove-dominated, and a transition or mix of the two, were studied. Community composition of juvenile nekton was sampled using fyke nets, minnow traps, and suction sampling and analyzed for abundance and diversity. Primary carbon sources (emergent vegetation, phytoplankton, macroalgae, benthic microalgae, submerged aquatic vegetation, and soil organic matter) and consumers ((blue crabs (Callinectes sapidus), brown shrimp (Farfantepenaeus aztecus), grass shrimp (Palaemonetes spp.), Gulf killifish (Fundulus grandis), periwinkle snails (Littoraria irrorata), eastern oysters (Crassostrea virginica), and southern ribbed mussels (Geukensia granosissima)) collected at each habitat type were measured using stable isotope analysis (δ13C, δ15N, δ34S) to identify trophic level, basal carbon sources, and assess how mangrove carbon is incorporated into salt marsh food webs. While data analysis is ongoing, preliminary results indicate that basal carbon sources supporting some marsh consumers (e.g., periwinkle snails) shift between habitat types, while others remain static (e.g., grass shrimp). This research will further develop our understanding of how climate induced shifts in vegetation influences valued marsh-dependent consumers in the estuarine ecosystems of northern Gulf of Mexico.

  1. Diplochory in western chokecherry: you can't judge a fruit by its mesocarp. (United States)

    Beck, Maurie J; Vander Wall, Stephen B


    Western chokecherry (Prunus virginiana var. demissa, Rosaceae) is dispersed by frugivorous birds and carnivores, but it has large seeds that are potentially attractive to rodents that could act as seed predators and dispersers. Here, we quantify the benefits of primary dispersal by birds and secondary dispersal by scatter-hoarding rodents. In the fall, avian frugivores (mostly American robins, Turdus migratorius, and cedar waxwings, Bombycilla cedrorum) consumed 87% of the fruit crop and dispersed 67% of the fruit crop away from parent plants. Rodents removed 89% of seeds that simulated bird-dispersed seed rain from transects in riparian zones and 58% from transects in upland habitats. Rodents scatter-hoarded 91.6% of the seeds they removed, burying most in small caches (two to eight seeds) 8-25 mm deep. About 39% of the seeds in spring caches produced seedlings. Inside rodent-proof exclosures, 52.1% of seeds buried to simulate rodent caches produced seedlings, 29.7% of which were still alive after 1 year. In contrast, only 3.8% of seeds placed on the soil surface, simulating dispersal by avian frugivores, produced seedlings. Seed dispersal by frugivorous birds likely contributes to colonization of unoccupied habitat through long-range dispersal and to escape from distance-dependent seed mortality near the parent plant. Despite seed losses, rodents offer short-range seed dispersal and bury seeds in more favorable sites for germination, improving seedling emergence and establishment. The combined mechanisms of seed dispersal significantly enhanced chokecherry seedling recruitment by providing more dispersal-related benefits than either frugivorous bird or scatter-hoarding rodents could provide alone.