Research progress on eco-physiological responses of shellfish under ocean acidification and global warming

Abstract

Global climate change due to industrialization and anthropogenic activities has been a critical problem worldwide since the last century. Because of anthropogenic activity, the increasing atmospheric concentration of CO 2 not only caused temperature rise, but also increased the H + concentration in the seawater with the large CO 2 absorption, namely ocean acidification. Global average sea surface temperature is significantly higher than before, and the ocean surface pH is also evidently reduced because of the sequestration of a large number of CO 2 by the ocean. Elevated atmospheric CO 2 is set to increase mean global temperatures by 2-4益 , and reduce the surface ocean pH by as much as 0.5 unit in the next century.It is crucial to forecast the impacts of global climate change on eco鄄physiology of marine organisms, especially in a multiple stressor situation expected by the end of this century. Some studies have showed that ocean acidification and global warming heavily threaten the marine ecosystem and biodiversity. Ocean acidification affects survival and reproduction of marine organisms negatively, especially those organisms with shells, such as shellfish, crustacean and echinodermata. The most influenced aspects include fertilization, hatching, early development, calcification, acid鄄base balance, immune function, protein synthesis, gene expression, feeding and energy metabolism, all of which are relevant to physiological functions, and http: / / www.ecologica.cn ocean acidification further impacts the individual behavior, population structure and marine ecosystem. To date, a large number of studies have revealed eco鄄physiological responses of shellfish to ocean acidification, focusing on the mechanisms that underlie physiological plasticity at molecular level with some reference to whole organism fitness. At the same time, seawater temperature rise resulting from global warming occurs with ocean acidification simultaneously. However, the combined effects of elevated temperature and pH variation on coastal and estuarine shellfish are less explored. Many sessile organisms, such as mussels, are unable to move fleetly to avoid warming and acidified areas, so their physiological activities and behavioural responses may be influenced. There is a growing demand to understand the responses of the marine biota to these environmental stressors. Thus, to predict the eco鄄physiological responses of marine organisms to global climate change more realistic and accurate, more and more researchers try to study the combined effects of warming and ocean acidification.This paper reviewed eco鄄physiological effects of ocean acidification on shellfish in recent years, mainly from individual early development, calcification, immune responses and reproduction etc. Moreover, the combined effects of ocean acidification and warming on shellfish were summarized and analyzed, expecting to provide some basic information for studying biological responses to ocean acidification in the future. The future worthy research points include the lati...