Fernando de Figueiredo Porto Neto

Phytoplankton dynamics in a highly eutrophic estuary in tropical Brazil

Para avaliar a qualidade ambiental Porto do Recife (Nordeste do Brasil), uma area ecologica e socialmente importante mas pouco investigada, observacoes, medicoes e amostragem do fitoplâncton foram realizadas durante as mares de sizigia e quadratura no periodo de estiagem (janeiro-fevereiro / 2005) e chuvoso (junho/2005). A area apresentou concentracao de clorofila a variando de 3,30 a 54,40 mg m-3, com maiores valores registrados durante a mare baixa no periodo de estiagem. Um total de 129 especies foi identificada com 53 especies durante o periodo de estiagem e 97 especies no chuvoso. As diatomaceas formaram o grupo mais diverso, com 75,47% no periodo de estiagem e 60,82% no chuvoso. Coscinodiscus sp. e Helicotheca tamesis caracterizaram o periodo de estiagem e Oscillatoria sp. e Coscinodiscus centralis o periodo chuvoso. A diversidade de especie variou de 1,06 a 3,74 bits cel-1 . Os baixos indices foram relacionados com a dominância de Helicotheca tamesis, Coscinodiscus centralis, Coscinodiscus sp. e Aulacoseira granulata. A sazonalidade determinou a estrutura da comunidade fitoplanctonica, em vez do fluxo estuarino. A area e exposta sazonalmente a varios impactos negativos, devido a degradacao metropolitana e ao elevado nivel de eutrofizacao.

Demersal zooplankton communities from tropical habitats in the southwestern Atlantic

Abstract Demersal zooplankton were captured with traps from a set of tropical coastal habitats (seagrass bed, coral reef, gravel, and sand bottoms) to allow comparisons among communities. Sampling was carried out during dry and rainy seasons in 2000 and 2001. Traps with and without light were placed at 18:00 and removed at 06:00 the next day for three consecutive days. Eighty-eight zooplankton taxa were identified. Copepoda was the most abundant group, outranking in relative abundance in seagrass and in sandy bottoms. Copepoda was mainly represented by Oithona oculata, Pseudodiaptomus acutus, and Acartia lilljeborgi. No significant differences were found among substrates (P=0.1464); however, differences were significant between light and dark traps communities (P=0.0410). The average density was 7113 (±3966) ind m−2 in the light and 4759 (±4825) ind m−2 in the dark. In the light traps, Amphipoda and O. oculata were more representative. Without light, the main group was Foraminifera (>40%). Cluster analysis presented two main groups, Itamaracá Island and Tamandaré Bay; light and dark traps formed separate groups within these location groups. The results allow us to assess the efficiency of the used traps in a set of habitats of the tropical coastal area and gives information on the preference of specific organism groups in one of the tested substrates.