Abstract
Climatic warming is most pronounced in the polar regions. For marine ectotherms such as fish, temperature is a key abiotic factor, influencing metabolic processes. Species distribution and abundance are driven by reproduction and growth, which depend on available energy exceeding baseline maintenance costs. These routine metabolic costs make up a large part of the energy expenditure. Thermal stress can increase routine metabolism, affecting an organism’s fitness. Data of routine metabolic rates of Antarctic fish are scarce, and comparability of existing data sets is often problematic due to ecological differences between species and in experimental protocols. Our objective was to compare routine metabolism and thermal sensitivity of species with similar ecotypes but different thermal environments to assess possible ecological implications of warming waters on energy expenditure in Antarctic fish, a fauna characterised by geographic isolation, endemism and putative thermal adaptation. We measured routine metabolic rates of three benthic Antarctic fish species from low- and high-Antarctic regions at habitat temperature and during acute temperature increase. Our analysis revealed differences in metabolic rates at the same temperature suggesting local adaptation to habitat temperature. Acute thermal stress induced a comparable response of metabolic rates to increasing temperature. We conclude that higher metabolic rates and thus higher energetic costs could be associated with narrower thermal windows, a potential disadvantage to the endemic high-Antarctic fish fauna facing the challenge of climate change.
Highlights
The polar regions comprise some of the ‘‘hot spots’’ of climatic warming
Our objective was to compare routine metabolism and thermal sensitivity of species with similar ecotypes but different thermal environments to assess possible ecological implications of warming waters on energy expenditure in Antarctic fish, a fauna characterised by geographic isolation, endemism and putative thermal adaptation
Around the Western Antarctic Peninsula, surface waters have risen in temperature about 1 °C in the second half of the twentieth century and around South Georgia a temperature increase of 2.3 °C has been recorded within the last 81 years (Meredith and King 2005; Whitehouse et al 2008)
Summary
Around the Western Antarctic Peninsula, surface waters have risen in temperature about 1 °C in the second half of the twentieth century and around South Georgia a temperature increase of 2.3 °C has been recorded within the last 81 years (Meredith and King 2005; Whitehouse et al 2008). Temperature changes have not yet been recorded for high-Antarctic regions such as the Weddell Sea, water temperature increases of up to 2 °C have been projected by the year 2100 for these areas (Hellmer et al 2012; Turner et al 2014). In some ectotherms, such as many fish species, body temperature is determined by ambient temperature, affecting metabolic processes.
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