A study of the structure of the plankton community along the coastal zone of the Casa Caiada-Rio Doce area (Pernambuco, Brazil) is presented. The results obtained indicated that in the protected zones the water presented high turbidity, high temperature, low salinity and high nutrient and oxygen rates. All of these conditions were responsible for the reduction in plankton diversity and an increase in the biomass of the most opportunistic (rstrategist) species e.g. Gyrosigma balticum and Bacillaria paxillifera (Phytoplankton) and Euterpina acutifrons (Zooplankton). The differences found with respect to others area studies performed in pristine conditions indicated that plankton structure could be used as an environmental health indicator and that, in this specific area, it was indicative of a poor quality coastal environment.

To evaluate the Maracajaú reef ecosystem (Northeastern Brazil), observations, sampling and measurements were performed monthly during spring low tides from February to June 2000, covering the transition from dry to rainy season. In this area, there is an extensive (approximately 10 km x 4 km), but to date poorly investigated, offshore coral reef formation, where a Marine Protected Area was established recently. The reef area presented chlorophyll a concentrations varying from 1.1 mg m -3 to 9.3 mg m (microzooplankton) and 15.7 mg m -3 (mesozooplankton). A total of 136 phytoplankton taxa were identified. Diatoms were the most abundant and diverse group, with 102 species. Average phytoplankton density was 3,125 10 -3 cells 1 -1 . It was identified that there were 61 zooplankton taxa, with copepods showing the highest diversity (23 species) and abundance. Seasonal forcing determined the micro-and mesozooplankton community structure, rather than the coastal-offshore gradient. In spite of the distance from the coast (5 to 7 km offshore), this area is intensively used by local populations, mainly for artisan fishery and diving tourism. The area is exposed to seasonally varying negative impacts due to freshwater runoff, mangrove degradation and tourism, being also menaced by coastal eutrophication.

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Zooplankton was examined in 14 commercial shrimp Litopenaeus vannamei ponds in tropical Brazil to assess their composition, determine their density, and indicate environmental quality. In each farm, two ponds and the water intake point were monitored in 2003. Sampling was made with a standard plankton net 50 micrometers mesh size. The zooplankton presented 40 taxa and was essentially composed of typical marine euryhaline species and suspensionfeeding forms. In all farms the dominant group was Copepoda with a total of 45%, followed by Protozoa (18%). The most abundant meroplankton were Polychaeta larvae, Gastropoda larvae, nauplii of Cirripedia and zoeae of Brachyura with large distribution in the region, sometimes dominating the community. Zooplankton abundance varied from 972+209 ind m -3 to 4,235 + 2,877 ind m -3 . In the studied marine shrimp culture ponds, copepods dominance were replaced by protozoan and rotifers as nutrient concentrations increased with the culture period, indicating that zooplankton trophic structure can be strongly affected by the occurrence of eutrophic conditions in shrimp ponds. The tendency of low species diversity is indicative of an unbalanced hypereuthrophic system decreasing the water quality and the cultured species. These results can be an important appointment to understand the effects of eutrophication in coastal plankton structure and its effects to marine aquatic food web.

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