Long-term effects of warming and ocean acidification are modified by seasonal variation in species responses and environmental conditions Jasmin A. Godbold and Martin Solan Ocean and Earth Science, National Oceanography Center Southampton, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK Warming of sea surface temperatures and alteration of ocean chemistry associated with anthropogenic increases in atmospheric carbon dioxide will have profound consequences for a broad range of species, but the potential for seasonal variation to modify species and ecosystem responses to these stressors has received little attention. Here, using the longest experiment to date (542 days), we investigate how the interactive effects of warming and ocean acidification affect the growth, behaviour and associated levels of ecosystem functioning (nutrient release) for a functionally important non-calcifying intertidal polychaete (Alitta virens) under seasonally changing conditions. We find that the effects of warming, ocean acidification and their interactions are not detectable in the short term, but manifest over time through changes in growth, bioturbation and bioirrigation behaviour that, in turn, affect nutrient generation. These changes are intimately linked to species responses to seasonal variations in environmental conditions (temperature and photoperiod) that, depending upon timing, can either exacerbate or buffer the long-term directional effects of climatic forcing. Taken together, our observations caution against over emphasizing the conclusions from short-term experiments and highlight the necessity to consider the temporal expression of complex system dynamics established over appropriate timescales when forecasting the likely ecological consequences of climatic forcing.
IntroductionSince the industrial revolution, CO 2 emissions from the burning of fossil fuels and changes in land use have steadily increased atmospheric CO 2 concentration from preindustrial levels of 280 ppm to currently approximately 385 ppm; these levels are projected to increase to 700-1000 ppm by the end of the twenty-first century [1], causing concomitant changes in global sea surface temperature (2-4.58C rise [2]) and chemistry (e.g. 0.4 -0.5 pH reduction [2]). Although historical records indicate that atmospheric CO 2 concentrations and sea surface temperatures have undergone significant oscillations and have exceeded present-day levels in the past [3,4], it is the unprecedented rates of change that are fuelling concerns over whether organisms will retain the capacity to mediate vital ecosystem functions and services [5,6]. A key component in answering this question will be a need to establish the likelihood, and realized extent, of species acclimation (or adaptation) to environmental change [7,8] and, if common across functionally important taxa, how such coping and adaptive strategies will alter species -environment interactions in the long term [9].Over the last decade, the impacts of warming and ocean acidif...