Efeitos de peixes bentívoros e macrófitas aquáticas submersas sobre o crescimento de microalgas perifíticas em lagos rasos: um experimento de mesocosmo

• Autor(a) principal: Medeiros, Paulo Ivo Silva de
• Data de Publicação: 2016
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/handle/123456789/43283
• topic: Lagos rasos; Shallow lakes; Peixes bentívoros; Benthivorous fish; Bioturbação; Bioturbation; Ecologia

Shallow lakes may present an alternation of stable states, between a clear water state dominated by submerged aquatic macrophytes, and a turbid water state dominated by phytoplankton. In shallow lakes theory, benthivorous fish are considered important to increase the resilience of the turbid state, while aquatic macrophytes are considered important to increased the resilience of the clear water state. However, shallow lakes theory ignores the role of a third category of primary producers, the periphytic microalgae, as well as their interactions with fish and aquatic macrophytes. Benthivorous fish capable of consuming periphytic microalgae must reduce their biomass even though they can stimulate algal growth through nutrient recycling. On the other hand, submerged aquatic macrophytes can provide substrate for the colonization of periphytic microalgae, but also compete with them for light and nutrients. The aim of this work was to test the hypothesis that benthivorous fish and aquatic macrophytes interact synergistically to reduce the periphytic algal biomass on the surface of the sediment. To test this hypothesis a field experiment with a 2 x 2 factorial design was carried out, combining the presence and absence of benthivorous fish (Prochilodus), with the presence and absence of submerged aquatic macrophytes (Ceratophilum and Egeria). The periphytic algal biomass was monitored in plates glued to the surface of the sediment for a period of 3 months. The results show that as expected submerged macrophytes decreased the biomass of periphytic microalgae, but contrary to what we expected, fish had no effects on this variable. Moreover, no significant interaction was observed between the effects of fish and macrophytes on peryphitic microalgae. In conclusion, the above results suggest that the primary production of periphytic microalgae may be important for the benthic communities of shallow lakes in the absence of submerged macrophytes, despite of the grazing effects of some benthivorous fish.