Variações sazonal e nictemeral do microfitoplâncton foram estudadas em uma estação fixa (00º46'37,2''S-046º43'24,5''W), localizada em uma área costeira próxima à ilha Canela (Norte do Brasil), durante os meses de setembro e dezembro/2004 (período seco) e março e junho/2005 (período chuvoso). As amostras destinadas à análise qualitativa do fitoplâncton foram obtidas a partir da filtragem de 400 L de água, através de uma rede planctônica (65 μm de abertura de malha), durante marés de sizígia, em intervalos regulares de três horas, por um período de 24 horas. O material coletado foi fixado com formol neutro a 4%. Paralelamente a essas coletas foi medida a salinidade da superfície da água. A salinidade apresentou variação significativa ao longo do período de estudo, variando entre 26,1 (junho/2005) e 39,0 (dezembro/2004), caracterizando o ambiente como eualino-polialino. Foram identificados 130 táxons incluídos nas divisões Cyanophyta (dois táxons), Bacillariophyta (115 táxons) e Dinophyta (13 táxons). As diatomáceas dominaram o microfitoplâncton da área, sendo Asterionellopsis glacialis, Dimeregramma minor, Skeletonema sp. e Thalassiosira subtilis os táxons mais freqüentes e abundantes. Os altos valores de salinidade condicionaram a maior representatividade das espécies marinhas neríticas, polialóbias. Os processos de ressuspensão provocados pelos ventos e arrebentação das ondas promoveram intercâmbios entre as populações planctônicas e ticoplanctônicas, dentre as quais as espécies Dimeregramma minor, Triceratium biquadratum e T. pentacrinus representaram novas ocorrências para as águas costeiras do litoral amazônico.

Pinheiro, S.C.C., Magalhães, A., Costa, V.B. da, Pereira, L.C.C. and Costa, R.M. da, 2013. Temporal variation of zooplankton on a tropical Amazonian beach. To assess the spatial and temporal variation in zooplankton populations at Ajuruteua Beach, northern Brazil, monthly samples were taken between August, 2004, and July, 2005, at three fixed stations, during the spring (flood/ebb) tide. The zooplankton community was characterized by the absence of any significant spatial or seasonal variation in density, diversity or evenness. However, density was significantly higher during the ebb tides, with mean values ranging from 4,967±670.0 ind.m−3 in July (flood tide) to 38,213±15,157 ind.m−3 in April (ebb tide). A similar tidal pattern was recorded for the density of copepods. The dominant copepod species were Euterpina acutifrons (47.0±30.5 to 18,313±2,431 ind.m−3) and Paracalanus quasimodo (420.0±60.0 to 11,260±7,203 ind.m−3) and, together with Oithona hebes and O. oswaldocruzi, were responsible for t...

The influence of environmental variables on planktonic biodiversity is widely known. However, the absence of information about the cyanobacterial community in tropical estuarine regions motivated this work, whose objective was to investigate the spatio-temporal variation of cyanobacterial density related to physicochemical factors in a Brazilian Amazonian estuary. For the qualitative and quantitative study of cyanobacteria and physicochemical variables, samples were collected in April/July/2009 and April/August/2010. We identified 31 species of the orders Chroococcales, Oscillatoriales and Nostocales. Species of the genera Aphanocapsa, Dolichospermum, Komvophoron, Microcystis, Pseudanabaena and Merismopedia were frequent and abundant throughout the study period. Some of the found genera have already been described as potential toxin producers. The dynamics of cyanobacteria were temporal, the highest densities occurred in 2010 (average= 1080.86 ± 702.86 cells.mL-1) mainly influenced by the high values of pH, temperature, electrical conductivity, total dissolved solids, ammonium nitrogen which led cyanobacteria to present different responses in terms of richness, density and diversity between the years.

The port regions of the Amazon are subject to environmental impacts high shipping traffic. In October 2015, a cargo ship containing 5000 oxen sank in the Port of Vila do Conde, northern Brazil, releasing large amounts of organic matter and diesel oil into the aquatic environment. We evaluated the consequences of this shipwreck on the zooplankton community. Sampling was carried out using a phytoplankton net (64 μm) at two locations close to the port. We calculated the frequency of occurrence, relative abundance, and trophic state index and performed a canonical redundancy analysis of zooplankton in this area. Total density values ranged from 371 to 8600 organisms/m³, with minimum values being recorded during the period of the shipwreck and maximum values after the shipwreck. The areas categorized as super eutrophic had the lowest density values. The most abundant species/groups were nauplii and copepodites of the orders Cyclopoida and Calanoida. Of the environmental variables, only biochemical oxygen demand, chemical oxygen demand, and total dissolved solids were selected by the redundancy canonical analysis. The environmental conditions of the region and the ongoing environmental impacts might substantially influence the structure of the zooplankton community. The predominance of these organisms, in addition to the high densities of nauplii and copepodites, was likely related to the large amounts of nutrients generated by the shipwreck.