Paper Reviewed
Zhao, L., Shirai, K., Tanaka, K., Milano, S., Higuchi, T., Murakami-Sugihara, N., Walliser, E.O., Yang, F., Deng, Y. and Schöne, B.R. 2020. A review of transgenerational effects of ocean acidification on marine bivalves and their implications for sclerochronology. Estuarine, Coastal and Shelf Science 235: 106620.

Writing as background for their study, Zhao et al. (2020) say that transgenerational plasticity (TGP) "is defined as phenotypic changes in offspring in response to environmental stressors experienced by their parental generation."

TGP is a topic of growing interest in so-named ocean acidification studies that seek to understand the impacts of rising atmospheric CO2 on marine life. It is garnering considerable attention because more and more studies are demonstrating the ability of marine organisms to experience TGP; whereas reduced seawater pH conditions may elicit a negative effect on a given species in the current generation, such negative effects are increasingly shown to disappear across multiple generations. And so it was that Zhao et al. set out to conduct a literature review on the topic of TGP in marine species subjected to so-called ocean acidification.

Their review focused on marine bivalves given their high ecological and economical importance to coastal ecosystems and the fact that several TGP studies to date have been conducted on these organisms. Specifically, their work aimed to provide "a concise overview of the long-term and transgenerational responses of marine bivalves to elevated pCO2 manifested at different levels of biological organization." And what did the researchers find?

In their own words, Zhao et al. report that "transgenerationally acclimated bivalves can actively modify the calcification physiology in response to elevated pCO2," noting that "without exception, positive transgenerational responses to an elevated pCO2 scenario projected for the year 2100 have been found in all five bivalve species hitherto studied, under the umbrella of two non-genetic mechanisms (increased maternal provisioning and epigenetic inheritance), suggesting that marine bivalves have remarkable transgenerational phenotypic plasticity which allows them to respond plastically and acclimate rapidly in an acidifying ocean."

This work provides important insights into a topic (transgenerational plasticity) that has been mostly neglected in ocean acidification research. Its encouraging findings reveal ocean acidification is likely a non-issue given that most marine species will have the benefit of employing TGP across dozens to hundreds or even thousands of generations before the ocean's pH falls to values predicted to occur in the year 2100 and beyond. Clearly, more studies need to examine the likelihood of TGP in marine species in response to ocean acidification and no assessment of the impacts of rising atmospheric CO2 on marine life will be valid without it.