Biofilms coating Schoenoplectus californicus as indicators of water quality in the Rio de la Plata Estuary (Argentina)

Community composition, structure, biomass and tolerance to pollution of biofilms growing on Schoenoplectus californicus were assessed, together with physico-chemical parameters of the water, to evaluate their usefulness as water quality indicators along the Argentinian shore of the freshwater zone of the Rio de la Plata Estuary. Monthly sampling was carried out at three sites, one of which, located in a nature reserve, was considered as the reference site while the others were affected by sewage outlets and port activity. The reference site had higher dissolved oxygen and turbidity values, the polluted sites greater conductivity, oxygen demands, phosphate, ammonium and nitrite values. Diatoms dominated the biofilms at the reference site; ciliates reached higher densities at the polluted sites. Significant differences were found in species numbers, species diversity index, biomass, tolerance to pollution of the taxa, and the Pampean Diatom Index, between the reference and the impacted sites. This study shows that the biofilms growing on Schoenoplectus californicus are good indicators of the changes in the water quality of their environment.