Salinity in a changing world: salts as modifiers of aquatic animal physiology and fitness

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Impacts of climate change will be mediated by the salinity of aquatic systems. Thus, there is an urgent need to investigate interactions between salinity and aquatic biota in order to understand the effects of a rapidly changing environment on the health of ecosystems. This program seeks to develop mechanistic knowledge of the salinity-organism interaction, and how this might influence future aquatic environments. One research objective will investigate how salinity contributes towards the invasive success of the European green crab. Recent work shows that this species can take up amino acids directly from the water, and that this may play a role in the crab's ability to withstand salinity fluctuations, and thus invade estuarine settings. Research will employ molecular, biochemical and physiological techniques to investigate amino acid transport in concert with mechanisms of salt and water balance to determine whether this invasive crab species is better equipped to use amino acids than native crab species. Studies will examine effects at a whole animal level, but the ability of the invasive species to thrive at the expense of a native species will also be investigated in experimental environmental systems. A second research objective seeks to understand the tolerance of freshwater animals to the increasing presence of salinity (e.g. via road salt run-off) in their natural habitats. Using many of the same molecular, biochemical and physiological tools employed in other objectives, the toxicological impact of different salt compositions will be examined, and the mechanisms by which these salts exert their effects will be explored. A third research focus will examine how salinity influences toxicity in aquatic animals living in Northern waters. These species exhibit biological characteristics that differ markedly from more temperate species, and given that regulations for the protection of aquatic systems have been developed in animals from warmer climates, such regulations may not be adequately protective of cold-water species. Metals are one important class of emerging toxicants in polar waters, and exert their effects through interfering with salt and water balance. Consequently, the sensitivity of Northern fish and aquatic invertebrates to metal toxicants will depend upon salinity, and their biological responses to salinity. Molecular, biochemical and physiological measurements will be combined with toxicological assays to characterize the sensitivity of Northern biota to a metal toxicant (copper) and to discern the influence that salinity has on this interaction. Collectively, this program will broaden our understanding of the role that salinity has in shaping organismal and ecological health, through enhanced knowledge of: the drivers of successful biological invasion; the sensitivity of freshwater animals to salts; and the applicability of current regulatory guidelines for the protection of Northern aquatic biota against metal toxicity.