A ‘deadly trio’ of marine environmental change? Past progress and future recommendations for investigating interactive effects of warming, rising CO2 and hypoxia on fish

Abstract

Anthropogenic climate change is associated with warming, reduced O2, and increasing CO2 in the world’s oceans. These combined factors, referred to as a “deadly trio” of marine environmental change, interact to cause biological effects on marine fish which may have population-level consequences. Interactions can be non-linear which presents a challenge when attempting to predict impacts of climate change using data from single factor studies. The potential for combinations of warming, reduced O2, and rising CO2 to affect fish will depend on regionally and locally specific patterns of change as well as the type of habitats which species live in. We identified 68 primary research articles that investigated interactive effects of climate change factors on marine fish. There are large discrepancies in research effort with ~56 % of studies focussing exclusively on combinations of temperature and CO2. Only one study included manipulations of all three of these factors simultaneously. Most studies focused on physiological measures of impact, and there was large variability in the prevalence of non-linear interactions between measurement types and species. Further studies are needed to address critical gaps in knowledge related to ecologically important processes, such as growth and reproduction. Experiments also need to give greater consideration to the magnitude and duration of treatments used in order to increase the relevance of results. We believe that a combination of scenario-based (i.e. specific documented or predicted environmental conditions for a particular location or species) and mechanistic approaches (fully factorial studies across a wide range of environmental conditions) can lead to an improvement in the predictive power of multi-factor experiments. Ultimately, providing much-needed evidence to develop management strategies to mitigate impacts of climate change on key fish species.