Spatial distribution of epibenthic molluscs on a sandstone reef in the Northeast of Brazil / Distribuição espacial de moluscos epibentônicos em um recife arenítico no Nordeste do Brasil

The present study investigated the distribution and abundance of epibenthic molluscs and their feeding habits associated to substrate features (coverage and rugosity) in a sandstone reef system in the Northeast of Brazil. Rugosity, low coral cover and high coverage of zoanthids and fleshy alga were the variables that influenced a low richness and high abundance of a few molluscan species in the reef habitat. The most abundant species were generalist carnivores, probably associated to a lesser offer and variability of resources in this type of reef system, when compared to the coral reefs. The results found in this study could reflect a normal characteristic of the molluscan community distribution in sandstone reefs, with low coral cover, or could indicate a degradation state of this habitat if it is compared to coral reefs, once that the significantly high coverage of fleshy alga has been recognized as a negative indicator of reef ecosystems health.

O presente estudo investigou a distribuição, a abundância e os hábitos alimentares de moluscos epibentônicos associados à cobertura e à rugosidade do substrato, em um sistema recifal arenítico no Nordeste do Brasil. A rugosidade, a baixa cobertura de corais e a alta cobertura de zoantídeos e algas frondosas foram as variáveis que influenciaram na baixa riqueza e na alta abundância de poucas espécies de moluscos no habitat recifal. As espécies mais abundantes foram classificadas em carnívoras generalistas, provavelmente associadas à baixa oferta e variabilidade de recursos nesse tipo de sistema recifal, quando comparado a recifes coralíneos. Os resultados encontrados neste estudo podem estar refletindo características normais para a distribuição dos moluscos em recifes areníticos, com baixa cobertura de coral, ou podem estar indicando um estado de degradação desse habitat, quando comparado aos recifes de corais, uma vez que a cobertura significativa de algas frondosas vem sendo reconhecida como um indicador negativo quanto à saúde dos ecossistemas recifais.

Spatio-temporal distribution of soft-bottom epibenthic fauna on the Cilician shelf (Turkey), Mediterranean Sea

Spatio-temporal distribution of epifauna collected with a sledge was studied on the Cilician shelf of the Mediterranean Sea. There were two different communities: the shallow community was restricted to water at 5 and 10 m deep with sandy bottom inhabited abundantly by Conomurex persicus, Arnoglossus laterna and Murex trunculus. Conomurex persicus, an introduced tropical species predominated the shallow zone and distinguished it from the deep zone. The deep community (25-150 m) lacked shallow water species and was dominated by Arnoglossus laterna, Goneplax rhomboides and Parapenaeus longirostris. Seasonality was not a major factor in the epibenthic community structure of the entire shelf, but it is in the shallow waters. Bottom depth was main factor for structuring the community on the shelf. Sediment size and organic content is also a controlling factor for the distribution of the epibenthic fauna. Rev. Biol. Trop. 56 (4): 1919-1946. Epub 2008 December 12.

Se estudió la distribución espacio-temporal de la epifauna recolectada con un trineo en la plataforma de Armenia Menor, Mar Mediterráneo. Hubo dos comunidades diferentes: una comunidad de aguas someras entre los 5 y 10 metros de profundidad con fondo arenoso habitado en forma abundante por Conomurex persicus, Arnoglossus laterna y Murex trunculus. Conomurex persicus, una especie tropical introducida, predominó en la zona de aguas someras, y la diferenció de la zona profunda. La comunidad profunda (25-150 m) no presentaba especies de aguas someras y estaba dominada por Arnoglossus laterna, Goneplax rhomboides y Parapenaeus longirostris. La estacionalidad no fue un factor importante en la estructura de la comunidad epibentónica presente en toda la plataforma, pero sí lo fue en las aguas someras. La profundidad del fondo del mar fue el factor principal en la estructura de la comunidad en la plataforma. El tamaño del sedimento y el contenido de materia orgánica es también un factor que controla la distribución de la fauna epibentónica.