Ecological effects of elevated CO2 on marine and freshwater fishes: From individual to community effects

Abstract

Research over the past decade has shown that climate-change relevant CO2 levels can affect the growth, development and survival of some fishes during early life. There are also wide-ranging effects on behavior that could alter performance and survivorship of some species. Yet, there is also substantial variation in the sensitivity of fishes to elevated CO2, both among and within species. This chapter explores the current understanding of ecological effects of projected future CO2 levels on marine and freshwater fishes, including major knowledge gaps and uncertainties, and interactions with other stressors such as global warming. While laboratory experiments show that elevated CO2 can affect ecologically important traits of some species, we are not yet able to predict which species are sensitive and which are tolerant to higher CO2 levels. Moreover, the impacts of elevated CO2 on ecologically relevant traits can depend on food availability and interact with elevated temperature and other stressors in unexpected ways. New studies also demonstrate that natural CO2 variation and ecological complexity can mitigate some of the negative effects of elevated CO2 observed in simplified laboratory experiments. Finally, studies at natural CO2 seeps suggest that indirect effects of elevated CO2 on food resources and habitats may have larger effects on fish populations than the direct effects of elevated CO2 on individual performance.