The plankton was examined as an indicator of water quality in 14 shrimp Litopenaeus vannamei farms in Brazil in 2003. The ponds were categorized by high stocking density (>30 PL m(-2)) of phytoplankton, consisting of 51 species with concentrations ranging from 365,218+/-416,615 cells mL(-1) to 1,961,675+/-3,160,172 cells mL(-1). Diatoms contributed to almost 70% of the species number and high densities resulted from Cyanophyta blooms, mainly Pseudanabaena cf limnetica. Forty zooplankton taxa were registered and were essentially composed of typical marine euryhaline species and suspension-feeders. Copepoda dominated (45%) the make-up, followed by Protozoa (18%), Rotifera (12%), and Mollusca (12%) larvae. Zooplankton varied from 972+/-209 ind m(-3) to 4235+/-2877 ind m(-3). Enhanced nutrient input affected plankton density and composition. Diatom and Copepoda dominance was replaced by cyanobacteria, protozoan, and rotifers as nutrient concentrations increased with the cultured period, indicating that plankton structure is affected by eutrophic conditions.

In order to address the impact on phytoplankton, sampling was conducted monthly at 4 fixed stations, from April/86 to March/87 at diurnal low and high tide using a plankton net (65 mum mesh size) and a 1 L Van Dorn bottle. Among the 133 taxa identified, marine littoral euryhaline species were most common, outranking Gyrosigma balticum (Ehrenberg) Rabenhorst, Nitzschia sigma (Kützing) Wm. Smith, Licmophora abbreviata Agardh, Climacosphenia moniligera Ehrenberg, Surirella febigerii Lewis, Terpsinoe musica Ehrenberg and Cylindrotheca closterium (Ehrenberg) Reiman and Lewis. The port construction caused significant changes to the phytoplankton community with a strong influence of marine species (mainly dinoflagellate) because of the opening of the reef near the river mouth in 1983. The shallow depth and hydrodynamic brought many littoral species to the water columm. The community was composed by marine euryhaline and limnetic organisms, influenced by the salinity, rain and tide. Species diversity was high (> 3 bits.cel-1) owing to the high environmental heterogeneity (marine, freshwater and benthic interactions). After the port implantation, a strong decrease occurred in phytoplankton density owing to high loads of suspended matter. Lowest values (121,00 cells.l-1) were registered during rainy season. During dry season, when light intensity was higher, phytoplankton presented highest density ( 1,789,000 cells.l-1).

This study reports the occurrence and the effect of the environmental factors on the spatial and temporal distribution of the dinoflagellate Akashiwo sanguinea ( . Density values were within the normal range and blooms were not detected. Despite being common in the area, the species showed preference for sites with high concentrations of orthophosphate and total dissolved phosphorus and with salinity in the mesohaline regime.Keywords: Akashiwo sanguinea, dinoflagellate, distribution, estuarine waters, northeastern Brazil. ). Os valores quantitativos estiveram dentro dos padrões normais, não tendo sido detectados florescimentos com conotações de blooms. Apesar de ser frequente na área, a espécie mostrou preferência pelos locais com maiores concentrações de ortofosfato dissolvido e fósforo total dissolvido e salinidade compreendida no regime mesoalino. Novo registro dePalavras-chave: Akashiwo sanguinea, dinoflagelado, distribuição, águas estuarinas, nordeste do Brasil.

manoel messias da silva costa, sonia maria barreto pereira, patri 'cia campos de arruda and enide eskinazi lec ‚a Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros, s / n, Recife, Pernambuco, Brazil This study aimed at describing the quantitative variations of epiphytic diatoms in Rhodophyta Galaxaura rugosa, collected in the Fernando de Noronha archipelago (north-eastern Brazil), during two annual periods (June 2006 and June 2007). The distribution of epiphytic diatoms in G. rugosa confirmed the occurrence of a quantitative variation/zoning along the thallus of the analysed host, with an increase in density (cells per gram wet weight of seaweed) of apical portions towards the basal parts of the seaweed, regardless of the collection points and the annual periods. The abundance was characterized by individuals with pennate symmetry with raphe, belonging to the Bacillariophyceae class. This fact is the result of the host being collected in an insular environment with great water movement under the direct action of trade winds and ocean currents for most of the year. The study confirmed that in marine ecosystems with strong hydrodynamics, epiphytic flora tends to comprise species with the largest adhesive strength.

This study reports the first occurrence of Trichodesmiumthiebautii Gomont ex Gomont on the coast of northeastern Brazil. Samples were gathered during the rainy season (July 2005) and the dry season (November 2006) at six stations distributed along two perpendicular profiles of the coast of Pernambuco (8º18'S - 34º56'W and 8º32'S - 35º00'W). T. thiebautii was found during both periods of the year and at the six collection stations, forming colonies in the form of clusters or more rarely, bundles, with straight cylindrical trichomes, quadratic or slightly longer cells, with widths between 5-10 µm and heights of 3-15 µm. The hydrological variables presented small variations, contributing to wide distribution of the species.