Spatial and temporal variations of Penilia avirostris and evadne tergestina (Crustacea, Branchiopoda) in a Tropical Bay, Brazil

We analysed monthly samples collected in Guanabara Bay, with a conical net of 200 mum mesh during 1985. The bay was divided into three areas: an outer region (area A), influenced by oceanic waters; an inner region (area C), i nfluenced by fluvial inflow; and a transition region (area B) with intermed iate features. Penilia avirostris and Evadne tergestina were observed in th e three areas, with greatest densities, however, in the outermost region, w hich had the highest salinities and lowest temperatures. Penilia avirostris was more abundant in summer (March), a period with the greatest relative d ensities of nanoplankton. Evadne tergestina was also abundant in summer, bu t its peak fell in November, a period with a relative increase in microphyt oplankton density in the bay. The two species disappeared in winter: Penili a avirostris was absent from May to August, whereas Evadne tergestina disap peared in August and September.