Maria da Glória Gonçalves da Silva Cunha

Trophic ecology of the zoanthid Palythoa caribaeorum (Cnidaria: Anthozoa) on tropical reefs

This study examined the trophic ecology of the zoanthid Palythoa caribaeorum in tropical reefs and evaluated its role in the energy flow in that ecosystem. Colonies of this species were sampled in the infralittoral zone of reefs in north-eastern Brazil in 2008. We calculated the richness, total abundance, relative abundance and frequency of occurrence of prey items. The biovolumes and weighted biovolumes of prey were calculated to characterize the most important food items in terms of their biomasses. To evaluate the selectivity, zoanthid and plankton samples were collected in 2010. Pennate diatoms were the most abundant and most frequent prey and, together with invertebrate eggs, constituted the most important food items in terms of their biomasses. There were no significant differences in abundance or richness among the different beaches studied, nor between the different seasons. The mean size of prey items within the polyps was significantly smaller than of the general plankton, indicating that P. caribaeorum selected for (or limited) certain prey sizes. This species predominantly fed on diatoms, and did not take advantage of many other prey items abundant in the plankton. Our results indicate that P. caribaeorum is suspensivorous and feeds principally on small phytoplankton. As this species is prey for benthic organisms such as polychaetes and nektonic organisms, our results indicate the importance of this zoanthid in tropical reef ecosystems as a primary consumer that serves as an energy transfer link between the planktonic environment and the nektonic and benthic spheres.

The instantaneous transport of inorganic and organic material in a highly polluted tropical estuary

The contribution of the estuarine channel of Recife harbour to the eutrophication of the Recife coastal area was evaluated by quantifying the instantaneous transport of salt, dissolved inorganic nutrients (PO4–, SiOH4, NO3–, NO2– and, NH4+), material in suspension, Chlorophyll-a, pico–nanoplankton and microplankton during the rainy (June 2007) and dry (November 2007) seasons. The results showed that all of the dissolved nitrogenated nutrients, the silicate and the material in suspension had higher concentrations during the rainy season, whereas the phosphate and Chlorophyll-a (both the total and the pico–nanoplankton and microplankton fractions) showed greater concentrations during the dry season. All of the materials considered were exported to the sea except for Chlorophyll-a (pico–nanoplankton and microplankton fractions) during the dry season, when these materials were imported into the area. The total liquid transport in the rainy season was three times higher than that found for the dry season. Silicate represented nearly 85% of the total exported material during the rainy period, whereas during the dry season, phosphate and silicate represented 79% of the total exported material. The stratification and circulation processes indicated a well mixed environment. The water-renewal rate was low, as demonstrated by the input of phytoplankton biomass during November. The area was characterised as eutrophic during the months investigated.

Fitoplâncton como ferramenta de gestão ambiental na praia de Brasília Teimosa, Pernambuco, nordeste do Brasil.

O objetivo deste trabalho foi avaliar os parâmetros ambientais, biomassa, comunidade fitoplanctonica e especies bioindicadoras, como ferramenta de gestao ambiental na praia Brasilia Teimosa, Pernambuco (8o04’S; 34o52’W). Parâmetros abioticos (precipitacao, temperatura da agua, salinidade, material em suspensao, teor e taxa de saturacao do oxigenio, nitrito, nitrato, fosfato e silicato) foram obtidos simultaneamente as coletas de fitoplâncton (garrafa e rede) no periodo chuvoso (maio; junho e julho/2005) e de estiagem (novembro e dezembro/2005; janeiro/2006). Com excecao dos valores de nitrato (maiores no periodo chuvoso), os demais parâmetros estiveram dentro dos padroes recomendados. Foram identificados 84 taxa, com maior representatividade das diatomaceas em abundância e frequencia, Asterionellopsis glacialis, Chaetoceros lorenzianus, Cylindrotheca closterium, Helicotheca tamesis, Licmophora abbreviata e Skeletonema costatum. Altos niveis de nitrato, clorofila a, numero de celulas por litro e especies bioindicadores de eutrofizacao (Oscillatoria sp., Scenedesmus sp., Euglena sp., Synedra sp., Pleurosigma sp., Pseudo-nitzschia sp. e Skeletonema costatum) corroboraram a influencia das atividades humanas na area, evidenciando um possivel comprometimento da sanidade ambiental relacionado ao periodo de estiagem (periodo de maior exploracao turistica-recreativa). Palavras-chave: Bioindicadores, Clorofila a, Florescimentos, Diatomaceas.