Shallow sublittoral benthic communities of the Laguna Estuarine System, South Brazil

Sediment properties, microphytobenthos biomass (chlorophyll a and phaeopigments), and the structure of the benthic communities of the three main lagoons (Mirim, Imaruí and Santo Antonio) of the Laguna Estuarine System, South Brazil, were analyzed during summer and winter. Microphytobenthos biomass did not differ significantly among the lagoons, but showed higher values in the summer. The macrofauna was characterized by low species richness and the dominance of the gastropod Heleobia australis, the tanaidean Kalliapseudes schubartti and the bivalve Erodona mactroides. The meiofauna was composed of 20 higher taxa and the nematodes dominated in all the lagoons and periods. Desmodora (Desmodora) sp.1, Terschllingia sp. and Microlaimus sp. were numerically the most important among the 74 nematode species registered. This study showed that, in the Laguna Estuarine System, differences in the benthos among lagoons and periods were dependent on the fauna component analyzed. Whilst macrofauna and nematodes were significantly more diverse in the inner stations, in the Mirim Lagoon, the number of meiofauna taxa did not differ significantly among the lagoons and the diversity and evenness were highest in Santo Antonio. These results were a response of the fauna to the salinity oscillations coupled with the heterogeneity of the sediment in the lagoons. The temporal variability of the fauna, macrofauna being more abundant in the summer and meiofauna in the winter, could be related to the different life strategies of these groups. Propriedades do sedimento, biomassa microfitobêntica (clorofila a e feopigmentos), e a estrutura das comunidades bênticas das três principais lagoas (Mirim, Imaruí e Santo Antonio) do Sistema Estuarino de Laguna, sul do Brasil, foram analisadas durante o verão e inverno. A biomassa microfitobêntica não diferiu significativamente entre as lagoas, mas seus valores foram maiores no verão. A macrofauna foi caracterizada pela baixa riqueza específica e a dominância do gastrópode Heleobia australis, do tanaidáceo Kalliapseudes schubartti e do bivalve Erodona mactroides. A meiofauna foi composta por 20 grupos taxonômicos e os nemátodas dominaram todas as lagoas e períodos. Desmodora (Desmodora) sp.1, Terschllingia sp. e Microlaimus sp. foram numericamente as mais importantes entre as 74 espécies de nemátodas registradas. Este estudo mostrou que, no Sistema Estuarino de Laguna, as diferenças no bentos entre as lagoas e períodos foram dependentes do comp