Experimental determination of differential seasonal response in seed of the Manila clam, Ruditapes philippinarum, in context of climate change

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Marine bivalves are found as key components of coastal habitats and have several important roles, such as serving as a food source for human beings and aquatic organisms. In fact, as the world's population continues to grow, bivalve aquaculture is expected to increase in importance as a means of addressing demands for animal protein; however, its growth may be possibly compromised by unfavourable climatic conditions. Thus, we assessed the effects of increased water temperature and acidification on the seeds of a bivalve of commercial importance, the Manila clam, Ruditapes philippinarum, in order to understand how this species may be affected by climate change at its early life stages. We examined the expected response of clams by experimentally mimicking seasonal conditions that could be forecasted to occur at the end of the twenty-first century. Different physiological responses were measured including growth rates, clearance rate, burrowing time and different biochemical biomarkers of metabolic stress. The results showed that growth decreased in acidic experimental conditions in spring, with a weak interaction with temperature. Clearance rate was negatively affected by a lower pH in spring and summer but, under extreme summer conditions, the effect of pH was overridden by the negative impact of a higher temperature. Burrowing rates were reduced by half under warm temperature conditions in spring and summer. In contrast, biochemical biomarkers were only significantly depicted under climate change conditions in autumn. Overall, this study demonstrates the need to consider seasonality when evaluating the potential effects of climate change on clam aquaculture in order to forecast consequences for biological production.