Researching the role of dissolved organic matter as a nutrient resource in freshwater ecosystems

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Freshwaters are losing biodiversity at a higher rate than any other planetary domain. A wide range of stressors are driving this trend, of which climate change and increasing nutrient delivery from food production and consumption are ubiquitous. Research to date on nutrient enrichment impacts on freshwater biota has been limited by the physical challenge of experimentation in a rapidly changing environment, and a narrow perception of bioavailable nutrient forms. It has focused on species-specific responses to inorganic nutrient forms, often in vitro or in lakes, rarely for flowing waters under ambient conditions, and usually for microbial or planktonic organisms, ignoring the responses of other biotic groups, community level responses to enrichment, and the combined impacts of the range of bioavailable organic compounds in freshwaters. Transformational research is needed to update current nutrient cycling theory for stream ecosystems, shifting from research explaining how part of the ecosystem responds to a limited range of stressors, to fundamental, holistic theory explaining how whole ecosystems respond to a broad palette of stressors. I will lead a multidisciplinary team to tackle this challenge, applying innovative techniques in molecular scale analysis, stable isotope probing and environmental genomics, under field and climatically-altered conditions. We will then use new data-driven modelling to understand relationships between taxonomic and functional shifts in response to dissolved organic matter (DOM) and inorganic nutrient exposure, revealing environment x gene interactions in biotic responses to nutrient and climate stressors. This will advance current theory and transform our understanding of the impacts of the full nutrient portfolio on freshwater ecosystems, revealing the specific role of DOM as this varies according to the composition of the DOM pool, species composition of the ecosystem, stream stoichoimetry and environmental character.