Effects of ocean acidification on marine primary producers and related ecological processes under multiple stressors

Although the individual effects of ocean acidification (OA), warming, solar UV radiation, deoxygenation and heavy metal pollution on marine producers are well-studied, their interactive effects are still unclear, strongly limiting our ability to project the ecological consequences of ocean climate changes. This chapter aims to provide an overview of our understanding the eco-physiological effects of OA and its combination with warming, solar UV radiation, deoxygenation and heavy metals. While OA is known to enhance photorespiration in both diatoms and green macroalgae, it enhances growth of coastal diatoms and other macroalgae that are adapted to fluctuating diel pH changes and then potentially enhances its contribution to carbon sequestration in coastal waters. OA is supposed to decrease pelagic primary productivity under multiple stressors (e.g., in combination with ultraviolet radiation, deoxygenation, warming), especially in oligotrophic waters, due to insufficient repairing or improvising processes that require both macro- and trace nutrients for syntheses of required proteins. Under influences of OA, macroalgal communities would shift toward non-calcifying species; diatoms become less abundance in phytoplankton assemblages. OA decreases calcification in algal calcifiers and exposes them to more harmful UV radiation, leading to a further decline of photosynthesis. Therefore, both the magnitude and direction of response of microalgae and macroalgae to OA largely depend on the levels of other environmental drivers (e.g., warming, deoxygenation). OA also exerts tremendous impacts on marine food webs. Total fatty acids and the ratio of long-chain polyunsaturated to saturated fatty acids of microalgae decrease, while some toxic secondary metabolites (such as phenolic compounds) accumulate under OA conditions, indicating a decline of food quality. This decline of food quality in primary producers can be transferred to secondary producers and negatively affect them (e.g., decrease in growth and reproduction). Taken together, OA can influence the biochemical compositions and contents in primary producers and their transfer to higher trophic levels and marine food webs is likely to be destabilized.

Jin P. & Gao K., 2021.Effects of ocean acidification on marine primary producers and related ecological processes under multiple stressors. In: Häder D. P., Helbling E. W. & Villafañe V. E. (Eds.), Anthropogenic pollution of aquatic ecosystems, pp 401-426. Switzerland: Springer, Cham. Chapter (restricted access).

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