Temporal variation of marine cladocerans in an estuarine region of Ubatuba, SP, Brazil

Abstract

The influence of temperature, salinity, pH and dissolved oxygen on the temporal distribution of marine cladocerans at Escuro River estuary, Municipality of Ubatuba, SP, was analysed. Sampling nearest to the surf zone was carried out from July 2004 to June 2005. The cladoceran Penilia avirostris (Dana, 1852) was the dominant species and appeared throughout the sampled period. The species Pseudevadne tergestina (Claus, 1877) and Pleopis polyphemoides (Leuckart, 1859) were the less frequent and Pleopis polyphemoides has occurred mainly in the winter. A negative relationship was obtained for P. avirostris abundance and the water dissolved oxygen, probably as an indirect effect to the water turbulence. Pleopis polyphemoides had a negative relationship with the water temperature and positive with salinity and pH. Abundance of P. tergestina was associated only with salinity. Our findings suggest that P. avirostris is the most resistant species to the local environmental oscillations and that the main factor avoiding their entrance into the estuary is the water turbulence near to the surf zone. Largest abundances of P. tergestina and P. polyphemoides are depending on higher salinity and, low temperatures are good indicators of occurrence of P. polyphemoides.