2013-03-012013-03-012010-06-18COSTA, Brenda Oliveira da. Variação nictemeral do microfitoplâncton em um estuário do nordeste paraense, Brasil. 2010. 102 f. Dissertação (Mestrado) - Universidade Federal do Pará, Instituto de Ciências Biológicas, Belém, 2010. Programa de Pós-Graduação em Ecologia Aquática e Pesca.https://repositorio.ufpa.br/handle/2011/3506This study’s object was to get to know micro phytoplankton’s diversity, as its nyctemeral variation related to environmental factors on Curuçá river (Curuçá, PA – Brazil). Twelve phytoplankton samples were collected in 3 collecting spots next to a Littopnaeus vannamei sea shrimp farm in a 24 hour time, during spring tides on the 14th and 15th of august 2004 and on the 24th and 25th of January 2005. It was determined its specific composition and phytoplankton density (org.L-1), analyzed its occurrence rate, diversity and evenness, grouping and main components. Physicochemical parameters did not show any significant variability between the collecting months, though it was observed an important rainfall influence on the salinity, filing the bottom values in jan/05 and the top ones in aug/04. There were 170 registered taxa that belong to the Baccilariophyta (149), Dinophyta (16), Chlorophyta (3) and Cyanobacteria (2) divisions. Bacillariophyta had the higher number of species shown, higher occurrence and density (97.59%). A few showed high abundance rates. During August the phytoplankton community is dominated by Bacteriastrum hyalinum, Bellerochea horologicalis, Chaetoceros curvisetus, Dimerograma dubium, Dytilium brigtwelli, Pseudo-nitzschia seriata and Skeletonema costatum. In January predominated Chaetoceros pseudocrinitus, Chaetoceros curvisetus and Skeletonema costatum. Neritic marine planktonic species, oceanic marine planktonic, neritic-oceanic marine planktonic predominated the samples. Specific diversity oscillated from 0.7591 bits.org-1 to 1.3314 bits. org-1 generally characterized by a low to very low diversity, showing a poorly diversified structure. Phisicochemical parameters and density among species was the main factor to determinate sample grouping in two big groups: the first one with august samples and the second one with January samples. Its component analysis showed that despite its low physicochemical variation amongst the collecting months, the rainfall and salinity variations were really important on the species density, causing an increase on phytoplankton density in January.porAcesso AbertoFitoplânctonEcossistema aquáticoDinâmica populacionalEstuáriosLitoralRio Curuçá - PACuruçá - PAPará - EstadoAmazônia brasileiraDissertaçãoCNPQ::CIENCIAS BIOLOGICAS::ECOLOGIA::ECOLOGIA DE ECOSSISTEMAS