Effects of environmental change on the olfactory system of fish

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For aquatic animals, the sense of smell is vital, as it has been linked to behaviours such as recognizing conspecifics, selecting mates and avoiding predators. Moreover, similar principles apply to how most aquatic organisms smell their environment; therefore, a change in the quality or effectiveness of their sense of smell could affect not only individuals but populations, species and ecosystems. The increase in CO2 in our atmosphere is causing not only an increase in sea surface temperatures but also ocean acidification, as a quarter of the CO2 released into the atmosphere is absorbed by the oceans. My research program aims to understand the functioning of the sensory systems of aquatic animals to better predict how these animals will respond to environmental change. I have recently shown a new mechanism by which ocean acidification negatively affects the olfactory system and behaviour of marine fish that is independent of changes in acid-base balance proposed by others. Hypoxia, high temperature, and high CO2 often occur together naturally. They are known as the "deadly trio" because they have the potential to limit species distribution in the near future. However, their combined effects on the olfaction of fish is currently not known. Moreover, plasticity is likely to be especially important in allowing organisms to cope with changing environments. Yet, all studies to date have been performed over relatively short periods or on adult fish, with little information about the capacity of their sensory systems to acclimate to these conditions. I propose to use the marine medaka (Oryzias melastigma) as a model system to address the following 3 short-term objectives: 1) Establish a better understanding of the mechanisms by which ocean acidification impairs olfaction; 2) Determine how multiple stressors combine to affect the sensory systems of fish; 3) Elucidate the role of developmental and trans-generational plasticity of the olfactory system in response to prolonged environmental stress. The general approach to objective 1-3 is to test specific hypotheses at multiple levels of biological organization, from the molecular level to the whole animal. We will use a combination of exposures to environmental stressors, olfactory nerve recording, histology, gene expression and behavioural tests to address these objectives. The funding requested will train 3 PhD, 2 MSc and 5 BSc students, who will obtain advanced skills that are invaluable for many scientific careers. The proposed work is expected to make unique and significant contributions to the understanding of how environmental change can affect the sensory systems of fish. This research will provide important insights into the potential effects of anthropogenic climate change not only on the behaviour and physiology but also their ability to cope with such a rapidly changing environment. The findings have clear implications for marine conservation, fisheries management and global food production.