Recebido em 20/12/2011. Aceito em 4/07/2012 RESUMO(Morfologia e distribuição de duas diatomáceas (Bacillariophyta) epizóicas no Brasil). As diatomáceas epizóicas em copépodos Pseudohimantidium pacificum e Falcula hyalina foram investigadas em microscopias óptica e eletrônica de varredura, com base em amostras coletadas em diferentes ambientes marinhos da costa brasileira. Pseudohimantidium pacificum é reportada pela primeira vez no Oceano Atlântico Sul Ocidental, ampliando significativamente sua faixa de distribuição geográfica. A espécie ocorreu sobre os copépodos Corycaeus amazonicus e Euterpina acutifrons, e em larvas cypris de Cirripedia. Falcula hyalina utilizou um número maior de hospedeiros, particularmente os copépodos Oithona oswaldocruzii, Pseudodiaptomus richardii e Acartia spp. A morfologia e dados biométricos das valvas de ambas as diatomáceas estiveram dentro dos limites registrados na literatura, incluindo as publicações originais. As duas espécies ocorreram em todas as estações de coleta ao longo da região costeira entre as latitudes 12°S e 28°S. F. hyalina havia sido registrada anteriormente no Oceano Atlântico Sul Ocidental na latitude 31°S.Palavras-chave: epibionte, Pseudohimantidium, Falcula, copépoda, biogeografia ABSTRACT (Morphology and distribution of two epizoic diatoms (Bacillariophyta) in Brazil). The epizoic diatoms Pseudohimantidium pacificum and Falcula hyalina, which live on copepods, were investigated using light and electron microscopes, based on material gathered from different marine environments along the Brazilian coast. Pseudohimantidium pacificum is reported for the first time for the Southwestern Atlantic Ocean, significantly enlarging its range of geographic distribution. This species usually covers the entire body surface of the copepods Corycaeus amazonicus and Euterpina acutifrons, and of cypris larvae of Cirripedia. Falcula hyalina uses a higher number of copepod hosts, particularly Oithona oswaldocruzii, Pseudodiaptomus richardii and Acartia spp. The valve morphology and biometrical data of both diatoms were within the range limits recorded in the literature, including the original publications. Both species occurred in all the sampling stations along the Brazilian coastline stretching from 12°S down to 28°S. Falcula hyalina had already been found as far as latitude 31°S in the Southwestern Atlantic Ocean.

The phytoplankton composition and biomass are being monitored in Admiralty Bay, Antarctic Peninsula since 2002 to detect possible interannual changes on a long-term monitoring perspective. In this report, we present the results of the 2009/2010 monitoring program regarding the phytoplankton composition during the PROANTAR XVIII operation. The community was dominated by both planktonic and benthic diatoms. A total of 140 species were found, many of them awaiting further morphological studies to determine their specific identity. A preliminary assessment of habitat preferences was made, showing that the diatoms in the Admiralty Bay came from distinct substrates like ice, rocks, sediments, plankton and macroalgae. These results indicate that benthic microalgae, particularly diatoms, play an important role in primary productivity of the pelagic community in inshore waters. The next steps will be to refine identification to analyse the whole water samples and to relate the results with the environmental and hydrographical features in Admiralty Bay.