Mayza Pompeu

Assessment of plankton community and environmental conditions in São Sebastião Channel prior to the construction of a produced water outfall

A comunidade planctonica e condicoes hidrologicas foram avaliadas como parte de um diagnostico ambiental no Canal de Sao Sebastiao, previamente a construcao de um emissario submarino de agua de producao, oriunda do terminal maritimo da PETROBRAS. As amostras foram coletadas em vinte estacoes oceanograficas situadas na area adjacente ao terminal petrolifero, durante a primavera de 1991. As concentracoes de nutrientes inorgânicos dissolvidos e de cIorofila-a obtidas, indicam um ambiente oligo-mesotrofico. Fenois e sulfetos nao foram detectados e os valores de 080, com excecao de tres pontos, foram caracteristicos de ambientes nao poluidos, apesar da contaminacao por oleos e graxas ter sido observada em metade das estacoes amostradas. O fito e o zooplâncton apresentaram altos indices de diversidade e equitatividade para toda area estudada. O fitoplâncton foi dominado por fitoflagelados, enquanto que o zooplâncton foi dominado por copepodos, especialmente Paracalanus quasimodo. A composicao da comunidade planctonica foi similar a de outras areas adjacentes, sob baixa pressao aotropogenica.

The genetic diversity of Mesodinium and associated cryptophytes

Ciliates from the genus Mesodinium are globally distributed in marine and freshwater ecosystems and may possess either heterotrophic or mixotrophic nutritional modes. Members of the Mesodinium major/rubrum species complex photosynthesize by sequestering and maintaining organelles from cryptophyte prey, and under certain conditions form periodic or recurrent blooms (= red tides). Here, we present an analysis of the genetic diversity of Mesodinium and cryptophyte populations from 10 environmental samples (eight globally dispersed habitats including five Mesodinium blooms), using group-specific primers for Mesodinium partial 18S, ITS, and partial 28S rRNA genes as well as cryptophyte large subunit RuBisCO genes (rbcL). In addition, 22 new cryptophyte and four new M. rubrum cultures were used to extract DNA and sequence rbcL and 18S-ITS-28S genes, respectively, in order to provide a stronger phylogenetic context for our environmental sequences. Bloom samples were analyzed from coastal Brazil, Chile, two Northeastern locations in the United States, and the Pribilof Islands within the Bering Sea. Additionally, samples were also analyzed from the Baltic and Barents Seas and coastal California under non-bloom conditions. Most blooms were dominated by a single Mesodinium genotype, with coastal Brazil and Chile blooms composed of M. major and the Eastern USA blooms dominated by M. rubrum variant B. Sequences from all four blooms were dominated by Teleaulax amphioxeia-like cryptophytes. Non-bloom communities revealed more diverse assemblages of Mesodinium spp., including heterotrophic species and the mixotrophic Mesodinium chamaeleon. Similarly, cryptophyte diversity was also higher in non-bloom samples. Our results confirm that Mesodinium blooms may be caused by M. major, as well as multiple variants of M. rubrum, and further implicate T. amphioxeia as the key cryptophyte species linked to these phenomena in temperate and subtropical regions.

Satellite estimates of chlorophyll-a concentration in the Brazilian Southeastern continental shelf and slope waters, southwestern Atlantic

Comparisons between in situ measurements of surface chlorophyll-a concentration (CHL) and ocean color remote sensing estimates were conducted in the Brazilian Southeast coast, Southwestern South Atlantic. In situ fluorometric data were acquired in four hydrographic cruises carried out during the austral summer and winter of 2001 and 2002. The satellite estimates of CHL were derived from SeaWiFS data recorded in HRPT mode by INPEs station with a nominal 1.1 km resolution. Four algorithms were used to estimate CHL: two empirical - Ocean Chlorophyll 4 bands (OC4v4), and 2 bands (OC2v4); one semi-analytical - Garver, Siegel, Maritorena (GSM01); and one based on neural network (NN). Comparisons of estimated and measured CHL were done within a temporal window of 12 hours from the in situ sampling time. SeaWiFS algorithms values are 5x5 pixel medians centered on the location of in situ sampling station. For the study area CHL was fairly well estimated by all the SeaWiFS algorithms. OC4 performed better (R2 = 0.71; rms = 0.22) than the other algorithms (OC2, GSM01, and NN). The OC2 algorithm also showed a good performance with R2 = 0.67 and rms = 0.23. The neural network algorithm performed better than the semi-analytical one (R2 = 0.62 and 0.55, respectively), but with a higher rms (0.34 and 0.20, respectively). In general, the OC4, OC2, and NN algorithms showed a tendency for overestimating CHL at higher concentrations and underestimating at lower values. The semi-analytic GSM01 algorithm overestimated only the lower CHL, but underestimated most of the other values.