Abstract
AbstractMesopelagic fish are an important component of marine ecosystems, and their contribution to marine biogeochemical cycles is becoming increasingly recognized. However, major uncertainties remain in the rates at which they remineralize organic matter. We present respiration rate estimates of mesopelagic fish from two oceanographically contrasting regions: the Scotia Sea and the Benguela Current. Respiration rates were estimated by measuring the enzyme activities of the electron transport system. Regression analysis of respiration with wet mass highlights regional and inter-specific differences. The mean respiration rates of all mesopelagic fish sampled were 593.6 and 354.9 µl O2 individual−1 h−1 in the Scotia Sea and Benguela Current, respectively. Global allometric models performed poorly in colder regions compared with our observations, underestimating respiratory flux in the Scotia Sea by 67–88%. This may reflect that most data used to fit such models are derived from temperate and subtropical regions. We recommend caution when applying globally derived allometric models to regional data, particularly in cold (<5°C) temperature environments where empirical data are limited. More mesopelagic fish respiration rate measurements are required, particularly in polar regions, to increase the accuracy with which we can assess their importance in marine biogeochemical cycles.
Highlights
The uptake of carbon dioxide (CO2) by the ocean through the biological carbon pump plays an important role in the partitioning of CO2 between the atmosphere and ocean (Kwon et al, 2009)
The mean respiration rate of mesopelagic fish measured in the Scotia Sea was 593.6 ml O2 individualÀ1 hÀ1
As wet mass (WM) is more measured, and to allow comparison with previous studies, we present our data in terms of units of WM
Summary
The uptake of carbon dioxide (CO2) by the ocean through the biological carbon pump plays an important role in the partitioning of CO2 between the atmosphere and ocean (Kwon et al, 2009). Carbon may be transported by passive sinking (the gravitational pump), physical mixing, or active transport through vertical migration of metazoans (Boyd et al, 2019). The gravitational pump was thought to be the dominant mechanism for transferring organic carbon to the deep sea. The importance of additional mechanisms, in particular the role of the VC International Council for the Exploration of the Sea 2020.
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