Epilithic biofilm metabolism during the high water flow period in an Andean neotropical stream

Tropical rivers show high discharge during the rainy period, and this might limit the epilithic biofilm biomass. While high discharge may limit algal biomass, high light and nutrient availability common in disturbed watersheds may promote high productivity, and even autotrophy. Metabolism may be affected by discharge peaks, but well-adapted algal communities should support quick recovery. These assumptions were analyzed through the patterns of oxygen production and consumption in the Rio Tota, an Andean stream in the north of the Colombian Andes with relevant farming activities. Metabolism was measured for 26 consecutive days with in situ recirculating incubation chambers. The results stressed that these are net autotrophic systems during the high water flow period and that this occurs with algal communities of low biomass and low diversity. The environmental conditions of high light, high but non-catastrophic flow, and moderate temperature favor the algal community performance. However, the stream metabolism was sensitive to the day-by-day variations of environmental conditions, in particular to the above-average hydrological variations.