Abstract
Marine copepods are central to the productivity and biogeochemistry of marine ecosystems. Nevertheless, the direct and indirect effects of climate change on their metabolic functioning remain poorly understood. Here, we use metabolomics, the unbiased study of multiple low molecular weight organic metabolites, to examine how the physiology of Calanus spp. is affected by end-of-century global warming and ocean acidification scenarios. We report that the physiological stresses associated with incubation without food over a 5-day period greatly exceed those caused directly by seawater temperature or pH perturbations. This highlights the need to contextualise the results of climate change experiments by comparison to other, naturally occurring stressors such as food deprivation, which is being exacerbated by global warming. Protein and lipid metabolism were up-regulated in the food-deprived animals, with a novel class of taurine-containing lipids and the essential polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid and docosahexaenoic acid, changing significantly over the duration of our experiment. Copepods derive these PUFAs by ingesting diatoms and flagellated microplankton respectively. Climate-driven changes in the productivity, phenology and composition of microplankton communities, and hence the availability of these fatty acids, therefore have the potential to influence the ability of copepods to survive starvation and other environmental stressors.
Highlights
To fuel mass spawning events that occur in advance of the spring bloom[8], thereby ensuring that the generation coincides with good feeding conditions
Our data suggest that the metabolic performance of sub-adult Calanus spp. remains unaffected by short-term exposure to the warmer and more acidic conditions that these animals are expected to face by the end of 2100; all univariate comparisons attempting to ascribe changes in the polar- and nonpolar datasets to the effects of temperature and/or pCO2 were non-significant
The apparently benign, direct effects of temperature and elevated CO2 concentration on the metabolome of Calanus spp. could reflect the variable histories of our wild-caught experimental animals[20,24,27], or that we incubated a mixture of Calanus helgolandicus and Calanus finmarchicus
Summary
To fuel mass spawning events that occur in advance of the spring bloom[8], thereby ensuring that the generation coincides with good feeding conditions. Ocean acidification, caused by the increased uptake of anthropogenic CO2 in seawater, has occurred in concert with warming during this observational period Whether or not this phenomenon has contributed to the decline in Calanus spp. remains unknown. The extent to which compensatory feeding occurs in the natural environment remains unknown, and it can only occur where feeding conditions permit External stressors such as ocean acidification are expected to reduce the quantities of resources that would otherwise be available for growth and affect long-term reproductive output. Environmental metabolomics is the study of how the metabolic profile of an organism responds to changes in the external environment This field of research has demonstrated that an organism’s metabolome, the suite of low molecular weight organic metabolites within their tissues and biofluids, changes in response to intrinsic processes such as growth and reproduction and extrinsic factors such as temperature, food availability and contaminant exposure[23]. We expected starvation-induced turnover of lipids and proteins to be elevated in our climate change treatments owing to the additional metabolic demands that these stressors impose
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