Abstract
This study aimed at evaluating the effects of the intensive fish-farming and the domestic wastewater on the structure of the phycoperiphyton community. Three experimental supports containing artificial substrate were assembled in two sampling sites: IF – region with intensive fish-farming and DW – near the domestic wastewater discharge. Samplings were carried out after the 21st, 26th and 31st day of colonization. The abiotic variables evaluated were: transparency, electrical conductivity, pH, turbidity, total suspended solids, alkalinity, dissolved oxygen, water temperature and nutrients. Phycoperiphyton was examined with regard to density, richness, abundance, dominance, diversity and eveness. Nutrients (total nitrogen, nitrate, ammonia nitrogen, orthophosphate and silicate) were different among the sampling sites. Although the total density, richness, diversity and evenness of phycoperiphyton were not affected by the different impacts, the density by class had differences between the sampling sites, with Bacillariophyceae presenting higher density at IF and Cyanophyceae and Coscinodiscophyceae at DW. Four taxa have been associated with the impact by domestic wastewater, and four, to the intensive fish-farming. The density by class of phycoperiphyton was the best attribute to evaluate the effects of human activity.
Highlights
Periphyton community is controlled by several factors, such as: temperature (MURAKAMI; RODRIGUES, 2009), light and nutrients (HILL; FANTA, 2008)
The growing urbanization and agricultural practices have increased the input of nutrients in shallow lakes worldwide, causing changes in the biological structure and dynamics of these environments (JEPPESEN et al, 2005), due to the eutrophication process, which may derail the multiple uses of the water bodies due to the unpleasant taste and
47% of the entire world supply of fisheries derive from fish farming, with a great increase in the production per capita of 0.7 kg in 1970 to 7.8 kg in 2008 (KASSAM et al, 2011).The collection and treatment of domestic sewage are insufficient in many countries, as in Brazil, where only 55.2% of the municipalities have sewerage system
Summary
Periphyton community is controlled by several factors, such as: temperature (MURAKAMI; RODRIGUES, 2009), light and nutrients (HILL; FANTA, 2008). The growing urbanization and agricultural practices have increased the input of nutrients in shallow lakes worldwide, causing changes in the biological structure and dynamics of these environments (JEPPESEN et al, 2005), due to the eutrophication process, which may derail the multiple uses of the water bodies due to the unpleasant taste and. Fish farming and the discharge of domestic wastewater stand out among the activities that contribute with the allochthonous input of nutrients into the water bodies. Studies involving changes in the community structure before environmental gradient or different human impacts have been frequently neglected (BLANCO et al, 2008) and the evaluation of these dynamics may reveal environmental changes or conditions of water quality suitable for the development of problems (PORTER et al, 2008). Studies concerning the influence of human impacts on the structure of periphytic communities are necessary, mainly in tropical regions
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