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

Abstract

Seasonal variations in diversity and biomass of tintinnids (Ciliophora: Tintinnida) were investigated at two fixed stations in the inner part of the Bahia 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 (If, In 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 x 10 6 μm 3 L - 1 (0.02-39.4 μg C L - 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' values were lower than those observed in other coastal systems found at about the same latitude in the northern hemisphere.