Protist functional groups in a sublittoral estuarine epibenthic area

Abstract

Protist communities were studied monthly at Santona beach (Cantabrian Sea, Spain) throughout one year. Twelve abiotic parameters were analyzed. The following functional groups (defined according to the preferential source of food) were considered: photoautotrophs (P), saprotrophs (S), bacterivores (B), algivores (A), non-selectives (N), and predators or raptors (R). A total of 269 species was found. The percentage of species in each functional group was: 11.66% A, 33.66% B, 26.45% N, 28.02% P, and 0.21% R. No species belonging to functional group S were found. Functional groups B and N had the highest percentage of biomass (up to 100% in certain months). The percentage of biomass for each functional group was calculated. There was a remarkable negative correlation between groups B and N at the four sampling sites. The biomass percentage of group A was important at several sampling points in March, June, and July, coinciding with an increase in their source of food. The percentage of group P rose in April and May, the months the period of irradiance was longer. The canonical population analysis showed that there were no significant differences with respect to the composition in terms of functional groups at the four sampling sites. These data were compared with those found in the literature on both marine and freshwater areas, by means of a hierarchical conglomerate analysis. The statistical analysis showed that there are generally noticeable differences between these two types of media. It is suggested that each area may have a characteristic species composition respect to functional groups, which is influenced by the environmental parameters.