RESPIRE · Climate-driven oxygen limitation in freshwater macroinvertebrates

To predict future effects of climate change, a comprehensive mechanistic understanding is essential. In marine ecosystems, a mismatch between oxygen demand and oxygen supply to tissues was shown to be the first mechanism to restrict survival at thermal extremes. Here a study is proposed on climate-driven oxygen limitation in freshwater macroinvertebrates. Aquatic invertebrates display a range of adaptations related to respiration and oxygen is a key factor structuring species assemblages in freshwater ecosystems. Therefore, oxygen limitation is likely to play a role. First this research will assess if the thermal limits of species arise due to oxygen limitation. In laboratory experiments the prediction will be tested that a species’ thermal window expands under higher oxygen concentrations. A field study will asses if species occupy different thermal niches under high and low oxygen conditions. Experimental work is proposed to characterize the oxygen demand (metabolic rate) of species and relate these to their observed thermal limits. Secondly, this research will assess if and how differences in a species’ thermal vulnerability can be predicted from their life-history and physiological traits that relate to oxygen supply and demand (e.g. respiration system, body size, development speed, metabolic rate). The oxygen limitation hypothesis may prove to be a new and important mechanism bringing the fields of physiology and ecology together to explain the effects of climate change on freshwater macroinvertebrates. The proposed research will investigate whether water pollution exacerbates the effects of higher temperatures. Such an insight will help in taking the most effective measures mitigating the effects of climate change.