HEAT TOLERANCE, REPRODUCTIVE HEALTH, RESPIRATORY AND CARDIAC ACTIVITY OF AQUATIC ANIMALS EXPOSED TO DICLOFENAC

Diclofenac (DCF) is one of the most important pharmaceutically active compounds present in the water cycle of wastewater treatment plants and often presents in aquatic ecosystems. The potential toxicity of DCF for non-target organisms has been previously highlighted, thus impact of its environmentally relevant concentrations on aquatic invertebrates deserves a special attention. To recognize effects of DCF on resistance and reproductive state of aquatic animals a set of biological endpoints: survival, fecundity, embryo abnormalities, respiration and heart rates, heat tolerance and cardioresistance in two freshwater invertebrates (gammaridean amphipod Gmelinoides fasciatus and bivalve mollusc Unio pictorum), exposed (96 h) to environmental relevant DCF concentrations, from 0.001 and 2  μg/ L, were evaluated. Experimental exposure to these concentrations of DCF resulted in distinct effects of DCF on the metabolism, reproduction and stress-resistance in both studied species (mollusc U. picrorum and amphipod G. fasciatus). An increase in thermal resistance (critical temperature maximum) in both studied species were recorded accompanying by the elevated metabolic rate, measured as the rate of oxygen consumption in amphipods (at DCF of 0.1-2 μg/L) and as heart rate at various temperatures (25 and 30ºC) and 0.1 μg/L of DCF in mollusks. In spite of DCF facilitated the increase in resistance of animals to heating, internal reserves of organisms can notably deplete due to elevated (up to 1.5-2 times compared to the control) energy requirements for adaptation in the presence of DCF. This study provided evidence that the elevated level of DCF (>0.9) can adversely affect amphipod (G. fasciatus) embryos status, increasing the number of embryos with arrested development with their further death and abortion. Sensitivities of various endpoints to diclofenac at used levels were not equal and varied depending on endpoint used, species stages and physiological functions.