title: Low water quality in tropical fishponds in southeastern Brazil.
abstract: Expansion of aquaculture around the world has heavily impacted the environment. Because fertilizers are needed to raise fish, one of the main impacts is eutrophication, which lowers water quality and increases the frequency of algal blooms, mostly cyanobacteria. To evaluate whether the water quality in 30 fishponds in southeastern Brazilian met the requirements of Brazilian legislation, we analyzed biotic and abiotic water conditions. We expected that the high nutrient levels due to fertilization would cause low water quality. We also analyzed cyanotoxins in seston and fish muscle in some systems where cyanobacteria were dominant. The fishponds ranged from eutrophic and hypereutrophic with high phytoplankton biomass. Although cyanobacteria were dominant in most of the systems, cyanotoxins occurred in low concentrations, possibly because only two of the 12 dominant species were potential producers of microcystins. The high phosphorus concentrations caused the low water quality by increasing cyanobacteria, chlorophyll-a, turbidity, and thermotolerant coliforms, and by depleting dissolved oxygen. We found that all the 30 systems were inappropriate for fish culture, according to Brazilian legislation, based on at least one of the parameters measured. Furthermore, there was not any single system in the water-quality thresholds, according to the Brazilian legislation, to grow fish. Our findings indicate the need for better management to minimize the impacts of eutrophication in fishponds, in addition to a rigorous control to guarantee good food.
authors.affiliation: Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil.
authors.forename: Simone M
authors.initials: SM
authors.lastname: Costa
authors.affiliation: Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Appel
authors.affiliation: Ambientais e Biológicas, Centro de Ciências Agrárias, Universidade Federal do Recôncavo da Bahia, Cruz das Almas, BA, Brasil.
authors.forename: Carla F
authors.initials: CF
authors.lastname: Macedo
authors.affiliation: Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil.
authors.forename: Vera L M
authors.initials: VL
authors.lastname: Huszar
mesh_terms: D000818:Animals; D017756:Aquaculture; D001427:Bacterial Toxins / Q000032:analysis; D001938:Brazil; D000458:Cyanobacteria / Q000254:growth & development*; D004784:Environmental Monitoring; D005068:Eutrophication; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D010839:Phytoplankton / Q000254:growth & development*; D011156:Population Density; D014871:Water Microbiology; D060753:Water Quality
chemical_list: D001427:Bacterial Toxins