Sub-lethal Effects of Anthropogenic Contaminants on Aquatic Invertebrates

Sammanfattning: Anthropogenic contaminants are considered to play a substantial role in the decline of freshwater invertebrate diversity. Sub-lethal effects of many of these contaminants on behaviour and life-history traits of aquatic invertebrates may contribute to their decline. As contaminants are rarely present in the environment alone, the effects of mixture exposures are highly relevant in assessing the risk these substances pose to the biota. This thesis focuses on sub-lethal effects of exposure to aquatic pollutants, separately and in combination, on fresh-water invertebrates. To investigate the single and combined effects of pesticides, larvae of the midge, Chironomus riparius were exposed to a 1 hour pulse of two neonicotinoids and two pyrethroids.  This short exposure to environmentally relevant concentrations of pesticides decreased the survival and delayed development in C. riparius.  The combination of neonicotinoids and pyrethroids did not produce synergistic effects; however, there was some indication of antagonism. Additionally, larvae of the damselfly, Coenagrion puella, were exposed for 14 hours to two environmentally relevant concentrations of pyrethroid pesticides, alone and in combination. Exposure to the pyrethroid, deltamethrin, reduced the larvae’s predatory ability. Combined exposure to both deltamethrin and esfenvalerate inhibited the Glutathione S-transferase detoxification pathway and may have additive toxic effects on the larvae’s predatory ability. Microplastics are increasingly gaining attention as an aquatic pollutant of major concern with respect to the toxicity of the microplastics themselves as well as their capacity to adsorb persistent organic pollutants like pesticides. To investigate the effects of microplastics and a pyrethroid, alone and in combination, C. riparius larvae were raised in sediment spiked with two sizes of polystyrene-based latex microbeads and an environmentally relevant concentration of esfenvalerate under normal and food-restricted conditions. Exposure to both sizes of microplastics and esfenvalerate lead to equally decreased emergence under food-restricted conditions. Additionally, exposure to esfenvalerate led to decreases in survival when food was scarce that did not occur when microplastics were co-present. Antishistamines are also an emerging aquatic contaminant of concern with very little known about their biological effects on aquatic wildlife. Antihistamines could potentially interfere with the histaminergic pathways and thus affect thermal tolerance and temperature preference in aquatic invertebrates. The freshwater snail, Planorbarius corneus, was exposed for 24 hours to the antihistamine, diphenhydramine. This exposure increased thermal tolerance and righting time, but did not affect temperature preference. The results of the investigation suggest that anthropogenic contaminates alone and/or in combination have sub-lethal effects on life history, behavior and physiology of aquatic invertebrates. Such sub-lethal effects have the potential to affect populations and community structure in the aquatic and terrestrial environment.