Biomonitoring the impact of agricultural pesticides in freshwater habitats using the invasive clam largillierti

LOZANO, VERONICA L.; PAOLUCCI, ESTEBAN; MUÑOZ, CAMILA; MORAÑA, LILIANA; LIQUIN, FLORENCIA ALEJANDRA; SYLVESTER, FRANCISCO

Congreso; XXII International Conference on Aquatic Invasive Species; 2022

Pesticide contamination is a major stressor to nature in agricultural landscapes worldwide, although its impacts on aquatic ecosystems are little understood. Due to their high abundances across large areas, invasive bivalves provide an opportunity toassess those impacts. The herbicide glyphosate and the insecticide neonicotinoid imidacloprid are two of the most widely used pesticides globally, and arecommonly found in freshwater systems in Argentina, a preeminently agricultural country. Using introduced Corbicula largillierti clams from an irrigation channel in the location of Coronel Moldes, an agricultural area in northern Argentina, we conducted 48-h exposureexperiments to two concentrations of imidacloprid (20 and 200 µg L-1a.i.), two concentrations of glyphosate (0.3 and 3 mg L-1 a.i.), andtwo combinations of both pesticides (imidacloprid and glyphosate at low andhigh concentrations, respectively). We assessed the impact on clam metabolicrates using respiration rate as proxy. All single pesticide treatments producedmild, although non-significant, decreases of respiration rates values, and onlythe exposure to the high imidacloprid concentration significantly reduced oxygenconsumption.  However, when a combined treatment of glyphosate and insecticide was applied, both high and low concentrations of pesticides significantly reduced respiration rates in C. largillierti. These results suggest synergetic negative effects on aquatic organisms likely representing a common scenarioin agroecosystems. Physiological endpoints allow the spotting of chemical contamination effects well before more obvious morphological changes or population declines appear. These effects possibly pinpoint more general ecosystem effects and highlight the role of invasive bivalves as potential biomarkersto monitor aquatic habitat degradation. While according to the present results chemical pollution might impose limits to the spread of freshwater invasive bivalves insome situations, it can also enhance their success due to being better adapted than native counterparts to human-altered habitats.