Temporal variability of diversity and biomasa of tintinnids (Ciliophora) in a southwestern Atlantic temperate estuary

Abstract

Seasonal variations in diversity and biomass of tintinnids (Ciliophora: Tintinnida) were investi- gated at two fixed stations in the inner part of the Bahía Blanca Estuary (38°42` S, 61° 50` W) during an annual cycle. The variations were analysed in relation to surface temperature, salinity, transparency, solar radiation and chlorophyll a (Chl a)concentration. Biomass was calculated in terms of biovolume and carbon units. Diversity was estimated as the number of species and the Shannon Index (H`, ln based). Density of tintinnids ranged from 100 to 7800 individuals L-1 H` ranged from 0 to 1.81. The biomass varied from 0.3 to 127.78 10 6 m 3 L 1 (0.02–39.4 gCL 1 ). Density was significantly related to temperature, solar radiation and Secchi distance (P < 0.01); diversity was significantly related to temperature (P < 0.01) and solar radiation (P < 0.05). Biomass was significantly related only to temperature (P < 0.01) in one of the stations. According to principal components analysis (PCA) tintinnids exhibited a segregation of three groups: winter, spring–summer and autumn for the most internal station and winter, spring and summer–autumn for the most external station. H 0 values were lower than those observed in other coastal systems found at about the same latitude in the northern hemisphere.