Impacts of aquaculture on water nutrients and benthic macroinvertebrates of lake Guamuez

Objective. To determine the level of environmental impact caused by an intensive aquaculture season of rainbow trout (Onchorhynchus mykiss) in floating cage systems in water nutrients and benthic macroinvertebrates in Lake Guamuez. Materials and methods. The study was developed in three areas of Lake Guamuez (two floating cage facilities and one control point). Three sampling stations with depths of 0, 10 and 20 meters were taken in each area, in order to perform measurements of total phosphorus, nitrites, nitrates and phosphates. Also, dives were carried out to a depth of approximately 20 meters, collecting sediment samples for the identification of macroinvertebrates. The environmental impact was evaluated by the relationship of the mentioned variables, using discriminant analysis and analysis of variance, previous verification of the statistical assumptions. Results. The nitrite, nitrate, phosphate and total phosphorus nutrients present significant differences (p<0.05) among all areas and only at some sampling depths. In addition, seven families of macroinvertebrates (Chironomidae, Thiaridae, Ampullariidae, Planaridae and Tubificidae indicative of contaminated and moderately contaminated waters and Hydrobiosidae and Hydrachnidae indicating good water quality) were collected. Conclusions. In the culture cages unlike the control point, higher nutrient content values were evidenced; the families of macroinvertebrates indicating contaminated or moderately contaminated water were also found. However, the results found are not found in risk limits for the lacustrine system or for the animals of culture.