Community-level changes in periphytic biofilm caused by copper contamination

Abstract

Periphyton has been recognized as an important element in aquatic food chains due to its role in primary production. More recently, it has been used as bioindicator of contamination in reservoirs since biofilm analysis can support in understanding the impacts of bottom-up contaminants to the reservoirs. Copper (Cu) is one of these pollutants which has been used as an algicide; it accumulates in the sediment and can be released to the water column, causing harm to various aquatic organisms, including the periphytic biofilm. In this work periphyton cultivated in the laboratory was exposed to copper, using concentrations from 0.013 to 0.15 mg Cu L−1 over 15 days under controlled conditions (temperature, light, and oxygenation). Different physical-chemical and ecological parameters were measured in order to describe the effects of Cu on the community, which included alterations in ash-free dry mass and chlorophyll concentration, as well as an earlier photosynthetically light saturation point. The results reflected different ecological behavior with modifications in the community composition and greater cyanobacteria dominance like abundance of species with mucilage as the Cu concentration increased. Furthermore, some species of diatoms were not found when the water was contaminated with Cu. This disturbance in the ecological composition of periphyton affects significantly the food chain due to the unpalatability of tolerant species and/or the bioaccumulation of Cu which may be transferred to other organisms potentially causing toxicity to primary consumers.