Relação da comunidade bentônica com variáveis ambientais e com a ictiofauna em um canal de maré do manguezal de Guaratiba, Baía de Sepetiba, RJ

Abstract

Sepetiba Bay support the main reminiscent of Rio de Janeiro Municipality mangroves and is on of the main formation of this kind of ecosystem in the State. This study aims to describe spatial and temporal patterns of the infauna and its relationship with environmental variables along a mangrove channel in the Sepetiba Bay, as well as to describe the fish community in the area and to search for relationship with the infauna. The raised hypothesis is that the infauna of a tidal channel (Bacalhau Channel) change according to distance of sea connection, with sediment texture and depth gradient, and along seasons. The Bacalhau channel has an extension of approximately 2.2 km and connects the Guaratiba Mangrove with the Atlantic Ocean. Samplings were carried out between October 2008 and August 2009, in four sites along the channel. Sampling dates were performed aimed to encompass the characteristics of different seasons: Summer (January and February), Autumn (April and May), Winter (July and August) and Spring (October and November). Substratum samples were taken during the ebb tide along a depth transect (from marginal vegetation to the inner channel substratum) in two replicates. Fish were collected with 2, 3 and 3.5 m diameter casting nets and size mesh of 5, 15 e 20 mm between adjacent knots, with 20 tries along the channel margins. Environmental variables were of temperature, salinity, dissolved oxygen, pH, turbidity and conductivity were taken at each sampling occasion. The mangrove channel sediment was mainly sandy with sites near to seas connection and in inner in the channel having comparatively high coarse factions. Percentage of organic carbon were highest at fine sediment, with the highest concentration in Spring. Physico-chemical environmental variables did not change significantly along the mangrove channel, but seasonal variations were detected. Infauna was comprised by 35 taxa, mainly Polychaeta, Isopoda and Tanaidacea. Microcrustaceans predominated in the marginal vegetation while Polychaeta distributed mainly within the thinner sediment layers. Ichthyofauna was compised by 24 species, numerically dominated by Diapterus rhombeus, Eucinostomus argenteus and Mugil liza. No significant relationship was detected between fish community and the infauna, although some specific associations were detected.