Distribuição espacial dos moluscos bivalves na região da plataforma continental do Cabo Frio, Praia de Maçambaba, Estado do Rio de Janeiro, Brasil

Molluscs bivalves of the continental shelf of the Cabo Frio region were sampled every month, during September 1985 to February 1987, using a Van-Veen grab, a rectangular dredge and a otter trawl. Forty five species were identified belonging to 29 families. The spatial distribution at 30, 45 and 60 metres of depth was determined by classification and ordination analysis. The distribution paterns were compared with data obtained with dredge and grab, and also with results given by the simple matching índex and by Pearson coefficient of linear correlation. It was possible to verify the existence of two communities: one living between 30 and 45 meters and another at 60 metros. The most frequent species were Mactra petiti Orbigny,1846, Tellina petitiana Orbigny,1846, Tellina gibber Ihering,1907 and Crassinella lunulata(Conrad,1834) at 30m and Nucula puelcba Orbigny,1846, Corbula patagonica Orbigny,1846 and Malletia cumingii (Hanley, 1860) at 60m. The average size of the particles and selection coefficient of the sediment seem to be the main cause of this distribution. The relation trophic group/sediment type hypothesis seems to be applied to the studied area, ocurring higher number of species and organisms with detritivorous habit at 60m and a higher number of species an organisms with .suspensivorous habit at 30 and 45m. The highest values of diversity were verified at 60m, possibly due to a higher spatial heterogeneity and a higher hydrodynamic stability of the sediments at -'this depth. There was no sazonality in the occurrence or density of any species collected.CAPESOs moluscos bivalves da Praia de Maçambaba da região da plataforma continental do Cabo Frio foram amostrados mensalmente, durante o período de setembro de 1985 a fevereiro de 1987, utilizando-se um pegador Van-Veen, uma draga retangular e uma rede "otter trawl". Foram identificadas 45 espécies pertencentes a 29 famílias. A distribuição espacial entre as profundidades de 30, 45 e 60 metros foi determinada através de análise de classificação e ordenação. Foram comparados os padrões de distribuição determinados com os dados obtidos com a draga e o pegador. Compararam-se, também, os padrões de distribuição gerados pelo índice binário "simple matching" e pelo coeficiente de correlação linear de Pearson. Pôde-se verificar a existência de duas comunidades distintas habitando a faixa de 30-45 metros e 60 metros. Utilizando-se conjuntamente os valores obtidos com a draga e o pegador pôde-se estabelecer as seguintes espécies como mais frequentes: Mactra petiti Orbigny, 1846, Tellina petitiana Orbigny, 1846, Tellina gibber Ihering,1907 e Cra.ssinella lunulata(Conrad,1834) nas estações de 30 metros e Nucula puelcba Orbigny, 1846, Corbula patagonica Orbiby, 1846 e Malletia·cumingii(Hanley, 1860) nas estações de 60 metros. As estações de 45 metros parecem se situar em uma faixa de transição, apresentando espécies características tanto de 30 metros quanto de 60 metros. O tamanho médio de partículas dos grãos e o grau de seleção dos sedimentos parecem ser os fatores que determinam essa distribuição. A hipótese da relação grupos tróficos/tipo de sedimento parece se sustentar para a área estudada, ocorrendo um maior número de espécies e de indivíduos detritivoros a 60 metros e um maior número de espécies e indivíduos filtradores a 30 e 45 metros. Os maiores valores de diversidade foram verificados a 60 metros, o que pode ser relacionado a uma maior heterogeneidade espacial dos sedimentos nessa profundidade

Spatial variability of macrozoobenthic community and trophic structure of a subtropical lagoon on southeastern Brazil's Atlantic coast

The objective of this study was to investigate the macrobenthic community of two compartments of the Maricá-Guarapina lagoon system, along the coast of Rio de Janeiro, Brazil, in relation to its abiotic sediment factors. An additional discrimination between sites was made, wherever the macrophyte Typha domingensis was found. This vegetation supposedly represents a potentially important food source for consumers. Furthermore, the trophic pathways were analyzed functionally by means of stable isotope analysis to assess the role of organic matter sources for consumers in the study area. In conclusion, the results showed differences between abiotic features in the compartments of the lagoon system, which, although they have affected the different species' distribution, have led to a homogeneous low-diversity system. Macrozoobenthic species tend to change with increasing distance from the sea, with a slightly different distribution in the two compartments. The macrophyte T. domingensis did not exercise any great influence on the biotic distribution and was not the main food source for consumers in the lagoon system, where, instead, sedimentary organic matter and macrophyte detritus also seem to play an important role in the trophic web

Spatial variability of macrozoobenthic community and trophic structure of a subtropical lagoon on southeastern Brazil's Atlantic coast

The objective of this study was to investigate the macrobenthic community of two compartments of the Maricá-Guarapina lagoon system, along the coast of Rio de Janeiro, Brazil, in relation to its abiotic sediment factors. An additional discrimination between sites was made, wherever the macrophyte Typha domingensis was found. This vegetation supposedly represents a potentially important food source for consumers. Furthermore, the trophic pathways were analyzed functionally by means of stable isotope analysis to assess the role of organic matter sources for consumers in the study area. In conclusion, the results showed differences between abiotic features in the compartments of the lagoon system, which, although they have affected the different species' distribution, have led to a homogeneous low-diversity system. Macrozoobenthic species tend to change with increasing distance from the sea, with a slightly different distribution in the two compartments. The macrophyte T. domingensis did not exercise any great influence on the biotic distribution and was not the main food source for consumers in the lagoon system, where, instead, sedimentary organic matter and macrophyte detritus also seem to play an important role in the trophic web.O objetivo deste trabalho foi estudar a comunidade macrobentônica em dois compartimentos do sistema lagunar Maricá-Guarapina, situado na costa sudeste do Brazil, relacionando com fatores abióticos do sedimento. Adicionalmente, foi feita uma discriminação entre locais com e sem a presença da macrofita Thypha dominguensis, que supostamente representa uma importante fonte alimentar para os consumidores dos sistemas lagunares. A contribuição das macrofitas e outras fontes primárias de alimento para a rede trófica local foi investigada através do método das análises isotópicas. In conclusão, os resultados obtidos mostraram que os fatores abióticos diferiram pouco entre os compartimentos estudados, embora pareçam influenciar a distribuição do macrobentos local, que se caracteriza por uma baixa diversidade específica. As espécies do macrobentos tendem a mudar com o distanciamento do canal de conexão com o mar, existindo pouca diferença na estrutura da comunidade nos dois compartimentos. Igualmente, a presença da macrófita não influenciou a distribuição do macrobentos e os resultados da análise isotópica indicaram que a referida macrófita não representa fonte alimentar importante para os consumidores locais. Por sua vez, a matéria orgânica sedimentar e detritos de macrófitas parecem exercer um papel importante na rede trófica desse sistema lagunar

Foraminifera as health bioindicators in nearshore and offshore Brazilian coral reef sediments

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Foraminifera on coral reefs of Brazil: the FOCO project

Abstrac

A global approach to mapping the environmental risk of commercial harbours on aquatic systems

The goal of this paper is to propose a screening method for assessing the environmental risk to aquatic systems in harbours worldwide. A semi-quantitative method is based on environmental pressures, environmental conditions and societal response. The method is flexible enough to be applied to 15 harbours globally distributed through a multinational test using standardised and homogenised open data that can be obtained for any port worldwide. The method emerges as a useful approach towards the foundation of a global environmental risk atlas of harbours that should guide the harbour sector to develop a more globally informed strategy of sustainable development

Population structure and reproductive biology of Uca rapax (Decapoda: Ocypodidae) in a tropical coastal lagoon, southeast Brazil

A population of the fiddler crab Uca rapax (Smith, 1870) found in Itaipu Lagoon, southeast Brazil, was sampled monthly from July 2006 to June 2007 in order to study population and reproductive features. The sex ratio of the population was statistically different from the expected (1:1) in almost every month, with a predominance of males. The reproductive cycle and the recruitment of juveniles were continuous, with two peaks. The fecundity ranged from 1.110 to 13.189 eggs (4.984 ± 2.493.8), not differing statistically among seasons. In contrast, the relative fecundity (F') and the reproductive intensity index (RII) were highest in the summer. Female size at the onset of sexual maturity was estimated as 6.1 mm and egg diameter ranged from 0.20 to 0.28 mm. The anthropogenic impact on the environment of Itaipu Lagoon probably had adverse effects on the local U. rapax population, as inferred by its low fecundity rates, early maturation age and biased sex ratio