Distribution of the mesozooplankton at continental shelf off Sergipe, Brazil

Abstract

The purpose of this work was to study the composition and abundance of the mesozooplankton at two stations at the continental shelf off Sergipe. At each station, oblique plankton tows were carried using plankton nets with 200 µm mesh size, in six hours intervals during three consecutive days. One hundred and three taxa were identified and Copepoda was the dominant group with fifty one species. The mesozooplankton assemblage was composed by coastal, neritic and oceanic tropical species. There were significant differences in composition and abundance between the two studied stations (p<0,05) but not between tidal stages. At station 1, the most abundant species were Creseis acicula, Oikopleura spp., Temora stylifera, Paracalanus quasimodo and Aglaura hemistoma, and at station 2 Paracalanus quasimodo, Paracalanus spp., Siphonophora, Gastropoda and Decapoda larvae. Coastal species such as Parvocalanus crassirostris, Acartia lilljeborgi, Euterpina acutifrons and Corycaeus giesbrechti occurred only at the last station, located close to the mouth of the São Francisco River, where surface salinity and transparency values were low. In this station the salinity average value at surface was 30,8±1,9 and at the bottom layer was 35.0±0.3 PSU. Mesozooplanhton density values ranged between 124 ind.m-3 and 2,658 ind.m-3 at station 1, and from 734 ind.m-3 to 3,061 ind.m-3 at station 2. A Monte Carlo test based on a canonical ordination revelead that local depth and water transparency were significantly correlated to the mesozooplankton distribution. Key words: zooplankton community, Copepoda, shelf off Sergipe, tropical.