Rising temperatures increase fish nitrogen excretion: Evidence from a meta‐analysis

Abstract

Abstract Temperature is a critical environmental variable for ecosystem processes, since metabolic rates of organisms increase with temperature, which could potentially elevate their excretion rates. In a warming climate, it is imperative to understand how temperature influences consumers' nutrient excretion, especially nitrogen (N) and phosphorus (P). Here, we review, quantify and synthesize the effect sizes of temperature on nutrient excretion rates of freshwater fishes through a meta‐analysis. Because there are too few studies measuring fish P excretion under different temperatures, we could only test the temperature effect on N excretion rates. Overall, our results show that fish N excretion increases with temperature, but there is considerable variability between studies. We investigated the nature of this heterogeneity by testing the influence of fish body size, climate (tropical, subtropical, temperate), delta temperature (difference between the lowest and highest temperature used in the experiment), acclimatization time, and feeding status (being fed or starved before excretion measurements) as moderators (predictors in meta‐analysis). We found that delta temperature and feeding status significantly influenced the magnitude of the effect, with studies applying the highest delta temperatures, and studies with starved fish, showing the highest effect sizes. Our meta‐analysis suggests that the magnitude of temperature increase and food availability can partly determine how global warming will affect fishes' N excretion in freshwater ecosystems.

Affiliated Institutions

• Universidade do Estado do Rio de Janeiro BR
• Universidade Federal do Pará BR
• Universidade Federal do Rio de Janeiro BR

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