Influência da predação de tilápia (Oreochromis sp.) na estrutura da comunidade de algas perifíticas em tanque de piscicultura tropical

The present study aimed to describe the structure of the periphyton community in the initial and intermediate periods of colonization in ponds with and without fish. Bamboo poles were used as a substrate to the development of phycoperiphyton in a fish pond and submitted to two treatments: in the presence and absence of tilapia (Oreochromis sp.). Periphyton samples were collected 4, 11 and 18 days after the beginning of the experiment, when the following limnological variables were evaluated: electric conductivity, dissolved oxygen, water temperature, pH, total suspended solids, total nitrogen, nitrate, nitrite, ammoniacal nitrogen, total phosphorous and orthophosphate. The phycoperiphyton structure was evaluated by total and class density, functional groups based on morphology, life form, richness, Simpson diversity index, abundant and dominant species, chlorophyll-a and feofitin. Periphytic community density tended to be lower in the presence of fish than in fish absence, mainly in later colonization stages. Small algae colonized the substrate firstly, but they only kept being dominant when the periphytic community was removed. Disturbance caused by fish predation can lead total density decrease, as well as periphyton composition changes. Keywords: disturb, aquaculture, phycoperiphyton, community dynamics.