Elevated CO2 enhances aerobic scope of a coral reef fish.

J L Rummer,C S Couturier,G E Nilsson,J A W Stecyk,P L Munday,S.-A Watson

doi:10.1093/conphys/cot023

Abstract

The uptake of anthropogenic CO2 by the ocean has been suggested to impact marine ecosystems by decreasing the respiratory capacity of fish and other water breathers. We investigated the aerobic metabolic scope of the spiny damselfish, Acanthochromis polyacanthus, from the Great Barrier Reef, Australia when exposed for 17 days to CO2 conditions predicted for the end of the century (946 μatm CO2). Surprisingly, resting O2 consumption rates were significantly lower and maximal O2 consumption rates significantly higher in high-CO2-exposed fish compared with control fish (451 μatm CO2). Consequently, high-CO2-exposed fish exhibited an unexpected increase in absolute (38%) and factorial aerobic scopes (47%). Haematological and muscle water changes associated with exercise were not affected by CO2 treatment. Thus, contrary to predictions, our results suggest that elevated CO2 may enhance aerobic scope of some fish species. Long-term experiments are now required to assess the response to elevated CO2 further, because developmental and transgenerational effects can be dramatic in fish. Ultimately, understanding the variability among species regarding the effects of CO2 on aerobic scope will be critical in predicting the impacts of ocean acidification on marine communities and ecosystems.

Highlights

Atmospheric CO2 levels are rising, leading to a corresponding increase in CO2 and a decrease in pH at the ocean surface, a process known as ocean acidification (Doney, 2010)
We investigated the aerobic metabolic scope of the spiny damselfish, Acanthochromis polyacanthus, from the Great Barrier Reef, Australia when exposed for 17 days to CO2 conditions predicted for the end of the century (946 μatm CO2)
Future CO2 levels are expected to impact marine ecosystems widely, because the scope for aerobic performance in fish and other water breathers is predicted to decrease at higher CO2 levels (Pörtner and Farrell, 2008)

Summary

Introduction

Atmospheric CO2 levels are rising, leading to a corresponding increase in CO2 and a decrease in pH at the ocean surface, a process known as ocean acidification (Doney, 2010). Future CO2 levels are expected to impact marine ecosystems widely, because the scope for aerobic performance in fish and other water breathers is predicted to decrease at higher CO2 levels (Pörtner and Farrell, 2008). Reductions in aerobic scope (the difference between resting and maximal oxygen consumption rates) result in less energy being available for life-history processes, such as growth and reproduction. Given that the physiological responses observed in fish at near-future CO2 levels (50 000 μatm), it is important to test the effects of climate change-relevant CO2 levels on fish and other marine species to determine if they have generally negative effects, as predicted by theory, or potentially positive effects in some species, as suggested by recent experimental studies

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