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Assessment of macrozoobenthic communities in the lagoon of Obidos, western coast of Portugal
V. Quintino, A.M. Rodrigues and F. Gentil

A benthic and sedimentological survey undertaken in the lagoon of Obidos, western coast of Portugal, based on 57 fauna1 samples and 61 grain-size analysis provided initial data for the assessment of the bio-sedimentological gradients in that system. Five sediment types were characterized and charted, ranging from clean coarse sand, in the vicinity of the lagoon mouth, to fine mud in the inner areas with a mean silt percentage of 98 %. The 68157 individuals collected were distributed among 119 species characteristic of both Atlantic and Mediterranean lagoons. Species richness was higher at those intermediate sampling stations, where more diverse surface sediments occur. Faunal abundance was higher in the center of the lagoon, on fine muds, and on the intertidal sand-banks. The correspondence analysis shows that both surface sediments and benthic communities were distributed along a gradient normal to the longitudinal axis of the lagoon, evolving from an outer marine community, occupying 4 % of the lagoon bottom and settled on clean coarse unstable sand, to an inner lagoon community, corresponding to 85 % of the lagoon bottom and located on fine muds. Transition occurred within a central ecotone area, where species richness was higher, which occupied the remaining 11 % of the bottom surface and was located on slightly silty medium sand. A cenotic model proposed for this lagoon is discussed in relation to hydrological and sedimentological data, and compared with both the faunistically similar lagoon of Albufeira located 140 km south of Obidos, and the general model proposed for Mediterranean lagoon systems.

Keywords: benthic macrofauna, surface sediments, bio-sedimentological gradients, coastal lagoons.
Contents of this volume Sci. Mar. 53(2-3) : 645-654 Back PDF
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