INTERACTION OF TWO ANTHROPOGENIC STRESSORS IN FRESHWATER: GLYPHOSATE AND THE INVASIVE MUSSEL LIMNOPERNA FORTUNEI ON PERIPHYTON COMMUNITY

DI FIORI, E.; PIZARRO, H.; RAMÍREZ, M.; CATALDO, D.

Puerto Rico

Congreso; ASLO 2011 Aquatic Sciences Meeting; 2011

American Society of Limnology and Ocenography

A manipulative experiment was carried out to evaluate the effect of glyphosate herbicide and the invasive fresh-water mussel Limnoperna fortunei on periphyton. The experimental design consisted of 24 microcosms (70L plastic bags) to which different glyphosate concentrations (0, 1, 3 and 6ppm) were applied in combination with L. fortunei (presence or absence), therefore resulting in eight treatments per triplicate. All microcosm bags contained artificial substrata previously colonized during one month with periphyton. Water and periphyton samples were obtained at days 0, 1, 8, 15 and 26 in order to quantify glyphosate, total phosphorus and dissolved phosphate concentration in water, whereas chlorophyll-a, dry weight and ash-free dry weigth were determined for periphyton samples. Glyphosate half-life decreased a 65-70% (ANOVA <0,01) in treatments with mussels. Periphyton mass variables increased with glyphosate concentration, and even more under mussel presence. Total phosphorous increased with herbicide for all treatments while dissolved phosphate was significantly correlated with glyphosate only in microcosm containing L. fortunei. The mussel Limnoperna fortunei would be participating in glyphosate degradation, releasing phosphate, favoring periphyton growth and altering water quality.