Bragança's socioeconomic situation is highly dependent on estuarine and marine biological resources that are influenced by tidal cycles and climatology. Field measurements (hydrological, hydrodynamic and microbiological variables) were taken in the most urbanized zone from Caeté estuary to characterise the quality of the local environment. During the dry period, the estuary was more eutrophic and presented the highest temperature (30.5 • C in Oct./06), salinity (17 psu in Feb./07), pH (8.24 in Feb./07) and fecal coliform (>1000 MPN/100 ml in Dec./06 and Feb./07) values. The phytoplankton Cyclotella meneghiniana, Coscinodiscus centralis and other r-strategist species were observed. The lack of basic hydric canalization was responsible for the local contamination, especially during the dry period when more concentrated wastewater from the city was emitted into the estuary, showing the human influence on the reduction of local estuarine water quality. In Bragança, the fishery is considered one of the main economic activities so, this contamination is worrisome because a large part of the local economy depends on biological resources and, thus, the contamination could negatively affect the environmental health of this Amazon ecosystem.

RESUMO(Caracterização quali-quantitativa do fitoplâncton da zona de arrebentação de uma praia amazônica). A estrutura da comunidade fitoplanctônica da praia da Princesa (Ilha de Maiandeua) foi estudada durante um ciclo nictemeral nos meses de novembro/08, março/09, junho/09 e setembro/09, de modo a verificar os efeitos de algumas variáveis ambientais sobre esta comunidade. O microfitoplâncton da praia da Princesa esteve representado por 98 táxons, com predomínio das diatomáceas, seguidas dos dinoflagelados e cianofíceas. Nas amostras qualitativas, Coscinodiscus perforatus Ehrenberg se destacou como abundante nos meses de março (45,6%) e junho (45,1%), enquanto que a análise quantitativa revelou Dimeregramma minor (Gregory) Ralfs como dominante, principalmente, em novembro (82,0%) e setembro (83,0%). A biomassa fitoplanctônica (clorofila-a) foi significativamente mais elevada em março (U= 0,0; p<0,05). Os valores médios de densidade fitoplanctônica total foram significativamente mais elevados no período chuvoso (F= 6,2; p<0,05), principalmente em junho (1223 ± 110 x 10 3 céls L -1). As curvas de K-dominância revelaram um declínio gradual na diversidade ao longo do período seco. A análise de ordenação (MDS) evidenciou a formação de três grupos, enquanto que a análise de componentes principais (PCA) mostrou a salinidade e a turbidez como as principais variáveis que definiram os componentes. A praia da Princesa é um ambiente dinâmico, onde os processos de ressuspensão promovem o intercâmbio entre populações fitoplanctônicas e fitobênticas. A elevada precipitação e o maior aporte fluvial, carreando elevadas concentrações de nutrientes, favoreceram o maior desenvolvimento do fitoplâncton, principalmente, durante o período chuvoso. Palavras-chave: Plâncton, Variáveis ambientais, Litoral Amazônico ABSTRACT(Phytoplankton of the surf zone in Amazon beach). The structure of the phytoplankton community of Princesa beach (Maiandeua island) was investigated during a nyctemeral cycle in the months of November/08, March/09, June/09 and September/09 to verify the effects of certain environmental variables on this community. The microphytoplankton of Princesa beach was represented by 98 taxa with the dominance of the diatoms, which were followed by the dinoflagellates and cyanophytes. The qualitative study revealed that Coscinodiscus perforatus Ehrenberg was abundant in March (45.6%) and June (45.1%), whereas in the quantitative analysis Dimeregramma minor (Gregory) Ralfs was dominant, mainly in November/08 (82.0%) and September/09 (83.0%). Biomass (chlorophyll-a content) was significantly higher in March/08 (U= 0.0; p <0.05). The average total phytoplankton density was significantly higher during the rainy period (F= 6.2; p< 0.05), mainly in June (1,223 ±110 x 10 3 cell L -1). K-dominance curves showed a gradual decrease in diversity along the dry period. Non-Metric Multidimensional Scaling analysis (MDS) revealed the formation of three groups, whereas Principal Component Analysis (PCA) showed that salinity and turbidity were th...

The present study aimed to analyze the structure and the temporal variation of the phytoplankton of Ajuruteua beach (Bragança, Pará) and to investigate the influence of environmental variables on the dynamics of this community to provide a basis about the trophic state of this environment. Biological, hydrological and hydrodynamic samplings were performed during a nyctemeral cycle in the months of November/08, March/09, June/09 and September/09. We identified 110 taxa, which were distributed among the diatoms (87.3%), dinoflagellates (11.8%) and cyanobacteria (0.9%), with the predominance of neritic species, followed by the tychoplankton species. Chlorophyll-a concentrations were the highest during the rainy period (24.5 mg m -3 ), whereas total phytoplankton density was higher in the dry period(1,255 x 10 3 cell L -1 ). However, phytoflagellates density was significantly higher during the rainy period.Cluster Analysis revealed the formation of four groups, which were influenced by the monthly differences in the environmental variables. The Principal Component Analysis indicated salinity and chlorophyll-a as the main variables that explained the components. Spearman correlation analysis supported the influence of these variables on the local phytoplankton community. Overall, the results obtained suggest that rainfall and strong local hydrodynamics play an important role in the dynamic of the phytoplankton of Ajuruteua beach, by influencing both environmental and biological variables.

Many dinoflagellate groups have been overlooked because of their small size compared with their larger counterparts; consequently, little is known about their diversity, distribution, and contribution to the planktonic community. Ansanella is a recently described genus of small marine planktonic dinoflagellates belonging to the order Suessiales. In this study, morphological observations together with molecular SSU and LSU rDNA analyses of clonal strains from the Catalan coast (NW Mediterranean Sea) allowed the identification of A. cf. natalensis and a newly reported species, Ansanella catalana. The cells of A. catalana are oval and 9.6-15.5 μm long; the cell surface is covered with amphiesmal vesicles arranged in 10-13 latitudinal rows; the episome has an apical furrow complex with a single elongated apical vesicle; a type E eyespot is also present. This newly identified species can be distinguished from congeneric species by morphological details of the cell surface, the presence of mucocysts and an extrusome type not previously reported in dinoflagellates. The characterization of this structure could provide insights into extrusome evolution in dinoflagellates. Metabarcoding analysis of plankton and sediment samples from the Catalan coast revealed a wide distribution of Ansanella and the remarkable contribution of this genus to the dinoflagellate communities from three different coastal habitats. HIGHLIGHTS• Members of Ansanella genus are widespread along the Catalan coast.• A new species of the genus Ansanella (Dinophyceae) is described.• A new type of extrusome was observed.

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