Structural characteristics and oxygen consumption of the epipelic biofilm in three lowland streams exposed to different land uses

The structural features and O-2 consumption of the epipelic biofilm in streams of the Pampean plain were explored. The study was conducted in three lowland streams subjected to different anthropic disturbances. Three sampling sites were selected in different sectors of these streams considering land use intensity (high, moderate, and low). Samples of the water and of the epipelic biofilm were taken seasonally. El Pescado stream is subjected to a low level of human impact and showed lower organic matter and nutrient contents than the Rodriguez and Don Carlos streams which are subjected to moderate and high levels of human impact. The biofilm composition of the three streams was represented by cyanophytes and diatoms but with different species composition and dominance; protozoans and nematodes were the characteristic heterotrophic groups in the three streams. The Rodriguez and Don Carlos streams showed the highest abundance of organisms. Multiple regression showed that O-2 consumption, chlorophyll a and trophic index were significantly correlated with the oxygen demands. On the other hand, the Rodriguez and Don Carlos streams exhibited significant differences with the El Pescado stream in O-2 consumption, trophic index, and chlorophyll a content. Our results demonstrated that the different biological descriptors responded to environmental variables that are influenced by the different land use intensities, being chlorophyll a, abundance of organisms, and O-2 consumption the most sensitive variables to the changes water quality.