Zooplankton from the Maracajaú Reefs, Northeastern Brazil.

This study was carried out to assess the diversity and the abundance of the reef zooplankton in the Maracajaú reefs. Samples were collected with two plankton nets (65 and 300 micrometers mesh size, each) from February to June/2000 at three stations in a transect perpendicular to coast. Plankton biomass in the 65 µm fraction varied from 45.19 mg.m-3 to 316.45 mg.m-3. In the 300 µm fraction biomass varied from 9.33 mg.m-3 to 43.16 mg.m-3. Zooplankton presented 61 taxa. Copepods were the most diverse taxa with 23 species. Euterpina acutifrons, Oithona oswaldocruzi, Oithona hebes, Oithona sp., Parvocalanus crassirostris, Acartia lilljeborgi, Bivalvia and Gastropoda larvae, Trilocularina sp., Balanus sp. larvae, Spirillina sp., Polychaeta larvae, Brachyura (zoea) and Oikopleura longicauda occurred in more than 75% of the samples. The zooplankton followed a seasonal pattern, with the highest numbers occurring during the rainy season (February). A high density of microzooplankton was found which varied from 1,917 ind.m-3 to 47,620 ind.m-3. The macrozooplankton presented lower densities with a minimum of 92.4 ind.m-3 and a maximum of 1,617 ind.m-3. Species diversity was intermediate (~2 bits.ind-1) and eveness relatively high (~0.78). Samples could be joined into 3 groups, mainly influenced by rainfall. Species similarity presented 5 groups: oceanic, neritic, a mixture of neritic and oceanic, reef and estuarine. Our data suggest a dynamic relationship between the zooplankton communities characteristic of inshore water trapped by the coastal boundary layer and more offshore plankton communities. Key words: Zooplankton, reefs, distribution, diversity