Volumen 41 - Número 1: 1-9 | 2006
Article

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Temporal variability of the estuarine macrofauna of the Patos Lagoon, Brazil

Leonardo C. Rosa^1,2* and Carlos E. Bemvenuti²

¹Pós-Graduação em Oceanografia Biológica – FURG
²Laboratório de Ecologia de Invertebrados Bentônicos. Departamento de Oceanografia, Fundação Universidade Federal do Rio Grande (FURG), Caixa Postal 474, 96201-900, Rio Grande, RS, Brasil

*This email address is being protected from spambots. You need JavaScript enabled to view it.

Temporal variability of the macrofauna density and its relationship with water and sediments characteristics were studied through monthly sampling at an estuarine embayment of the Patos Lagoon, Brazil from January to December 2001. Both, water and sediments characteristics showed distinct seasonal patterns. High salinity and water temperature values were registered in summer months. Increase of fine fractions in the sediments occurred in cold months. A total of 38,827 individuals represented by 18 species were collected during the study period. The bivalve Erodona mactroides, the tanaid Kalliapseudes schübartii, the polychaetes Heteromastus similis and Nephtys fluviatilis, and the gastropod Heleobia australis were the dominant organisms, accounting for more than 90% of total macrofauna. The macrofauna also showed a seasonal pattern, with the highest density found in summer (January = 62,205 ind. m^-2) and the lowest one in winter (July = 9,410 ind. m^-2). This pattern results from the species reproductive process, which was strongly correlated to the increase of water temperature at the end of spring. The low macrofauna densities in winter are related to a high predation during summer along with the absence of effective recruitment in cold months. Furthermore, sedimentary proprieties changes due to natural climatic disturbances could also be important factors controlling the estuarine macrofauna of the Patos Lagoon by increasing mortality rates.

Key words: Benthos, shallow water, estuary, southwest Atlantic Ocean