Trace metal concentrations in sediments of the Eastern Mississippi Bight

Sediments collected from 3 onshore-offshore transects (12 stations total) in the Eastern Mississippi Bight at 5 different times during 1987–1988 have been analyzed for total Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Se, Sn, Th and Zn. The data show considerable variation both spatially and temporally, largely as a result of natural variability in grain size and mineralogy. Clay-rich samples from deep water were always more metal-rich than sandy samples from shallow areas. Many samples from near the Mississippi River Delta appeared to be enriched in Ba by about a factor of two, probably as a result of contamination from oil well drilling mud, but there were few other indications of pollution influences. Many samples from throughout the area gave Mn/Fe and Cd/Fe ratios a factor of two or more lower than their Mississippi River source material. This shows that biochemical activity in the sediment is capable of solubilizing reducible and adsorbed metals.     

The role of organic coatings in the enrichment of marine particles with selenium. The fixation of selenite on an adsorbed amino acid

The enrichment of marine particles with selenium cannot be explained as that with metals present in cationic form by complexation with anionic functional groups of adsorbed organic matter. Physicochemical data obtained using a model system are reported. The surface of the particles is modelized by a mercury electrode whose surface charge density can be easily changed, covered by a layer of adsorbed polymers. Studies with different kinds of macromolecules and salts show a specific interaction between adsorbed polyalanine and selenite. The results can be explained by the concordance of the distances between two oxygen atoms in this oxyanion and between two amine groups of the adsorbed polypeptide. A similar mechanism could occur in marine aggregates whatever their nature, as long as they contain amine groups at their surface which result in this concordance. Some prospects derived from the results are discussed.     

Analysis of the economic benefits associated with the recovery of threatened marine mammal species in the Canadian St. Lawrence Estuary

This paper examines Canadians' willingness to pay to recover the populations of three marine mammal species found in the St Lawrence Estuary. The valuation approach utilized a stated preference tool that is somewhat a hybrid between contingent valuation and a choice experiment with multiple species recovery program options and choices framed as referenda. Program options involved the use of a marine protected area and restrictions on whale watching and shipping industries. The estimated willingness to pay (WTP) for different levels of marine mammal recovery ranged from $77 to $229 per year per household and varied according to the species affected and the recovery program effort. A series of tests revealed that people would be willing to pay more for programs that contribute to greater increases in marine mammal populations, but the additional value of programs that improve a species status beyond the “at risk” threshold is relatively small.     

Modeling photosynthesis and the growth of marine phytoplankton

The paper analyzes the most popular models of photosynthesis and growth of marine phytoplankton in the literature and demonstrates their limitations. A new approach to modeling is proposed and used to obtain new models of marine phytoplankton photosynthesis and growth. An important feature of the proposed models is their ability to describe coupled multisubstrate cyclical interactions typical of biochemical and physiological processes. As a first approximation, the mathematical models are represented by equations of nonrectangular hyperbolas. The models describe the stoichiometry of extraction of elements from the medium, whatever the degree of their limitation, an important feature in describing biogeochemical cycles of elements. This stoichiometry is governed by measurable internal parameters of an organism (substrate parameters) and can be a key cause of stoichiometric formation of elements in the ambient medium, described, for example, by the Redfield ratio. The substrate constants are fundamental characteristics of the models, which form “automatically” in the construction of model equations in arbitrary units.     

Anthropogenic factors and habitat complexity influence biodiversity but wave exposure drives species turnover of a subtropical rocky inter‐tidal metacommunity

Coastal ecosystems are complex and species rich, but are vulnerable to degradation from a variety of anthropogenic activities. Nevertheless, information on inter‐tidal community composition in the Caribbean Basin and at other oceanic sites is lacking. Such information is essential to developing a more comprehensive understanding of rocky inter‐tidal systems and their responses to global change. The goals of this study were to determine the relative importance of environmental (wave power density, wave height), habitat (e.g. algal cover, slope, complexity of rock surfaces) and anthropogenic (distance to roads, population density) factors associated with the structure of local assemblages at multiple shore heights and the regional metacommunity of mobile invertebrates on oceanic rocky inter‐tidal habitats. Environmental characteristics associated with habitat complexity (algal cover, rock surface complexity) and human population density were most strongly associated with abundance and biodiversity of invertebrates. Species richness was positively correlated with surface complexity, but abundance was negatively correlated with both surface complexity and per cent algal cover. By contrast, abundance of invertebrates was positively correlated with human population density, and diversity was negatively correlated with human population density. Abundance of invertebrates was greatest in the mid inter‐tidal zone, whereas diversity was greatest in the lower inter‐tidal zone. Metacommunity structure was Gleasonian, but the gradient along which species turnover occurred was correlated with measures of wave exposure, rather than anthropogenic activity. Unlike in previous studies, mostly at mainland sites, human activity primarily altered dominance patterns of communities, while having relatively little effect on species richness or composition.     

Differentiation in reproductive traits of geminate mangrove crabs of the genus Aratus (Decapoda: Brachyura) across the Central American Isthmus

The mangrove crab Aratus pisonii was considered to have an amphi‐American distribution; however, a recent study revealed that the Eastern Tropical Pacific populations were genetically distinct, thus representing a new species: Aratus pacificus. These species separated by the Isthmus of Panama have diverged under different environmental conditions that may have influenced their reproductive biology. As the available information about this genus concerns almost exclusively the Caribbean species, the aim of the present study was to analyse and compare reproductive aspects of A. pacificus and A. pisonii obtained from both the Pacific and Caribbean coasts of Costa Rica. Females were collected from April 2011 to April 2012, and reproductive features such as breeding season, size distribution of ovigerous females, fecundity, reproductive output, embryo volume and embryo water content were assessed. Both species produced embryos during the entire sampled period. Most females of A. pacificus carrying embryos close to hatching were found during the rainy season. Ovigerous females of A. pisonii were substantially larger and reached sexual maturity at a larger size than females of A. pacificus. Embryo production started in A. pacificus at a smaller female size than in A. pisonii. As fecundity increased with female size, the average fecundity was lower in A. pacificus. Females of A. pisonii produced larger embryos, which might be related to lower food availability: higher energy content in the embryo enhances the chances of larval survival. These data regarding reproductive features of the Pacific and Caribbean species support the conclusion to separate A. pacificus from A. pisonii.     

Changes in the macrobenthic communities of the Gudauta Oyster Bank

Twenty-nine benthic invertebrate species were registered for the Gudauta Bank in the depth range of 8–32 m in 1990. The shallow-water biocenose was defined for the depths of less than 10 m, the biocenoses of Anadara inaequivalvis and A. inaequivalvis-Upogebia pusilla occupied the depths of 10–30 m; and the biocenosis of Pitar rudis was found for the depths of more than 30 m. The highest biodiversity and abundance of benthos was registered for the Anadara biocenoses, while the lowest, for the shallow-water ones. It was found that significant changes in the benthic communities took place in the forty years after the predator gastropod Rapana venosa was introduced into the Black Sea. The oysters became extinct on Gudauta Bank, and the species composition of the benthic community has been significantly depleted. Alien species of Anadara and Rapana became the most abundant by biomass, comprising more than 80% of the total biomass of the benthos. The population density of Rapana constituted 12 ind./m² and was the highest ever registered for the studied areas of the Black Sea. Insufficient nutrition preconditioned the small size of the mollusks.     

Statistical characteristics of polar lows over the Nordic Seas based on satellite passive microwave data

Izvestiya, Atmospheric and Oceanic Physics - In this study polar lows over the Nordic Seas for the period of 1995–2008 have been detected and studied using the Special Sensor Microwave Imager...