Effects of ocean acidification on Antarctic marine organisms: A meta‐analysis

Abstract

Southern Ocean waters are among the most vulnerable to ocean acidification. The projected increase in the CO 2 level will cause changes in carbonate chemistry that are likely to be damaging to organisms inhabiting these waters. A meta-analysis was undertaken to examine the vulnerability of Antarctic marine biota occupying waters south of 60°S to ocean acidification. This meta-analysis showed that ocean acidification negatively affects autotrophic organisms, mainly phytoplankton, at CO 2 levels above 1,000 μatm and invertebrates above 1,500 μatm, but positively affects bacterial abundance. The sensitivity of phytoplankton to ocean acidification was influenced by the experimental procedure used. Natural, mixed communities were more sensitive than single species in culture and showed a decline in chlorophyll a concentration, productivity, and photosynthetic health, as well as a shift in community composition at CO 2 levels above 1,000 μatm. Invertebrates showed reduced fertilization rates and increased occurrence of larval abnormalities, as well as decreased calcification rates and increased shell dissolution with any increase in CO 2 level above 1,500 μatm. Assessment of the vulnerability of fish and macroalgae to ocean acidification was limited by the number of studies available. Overall, this analysis indicates that many marine organisms in the Southern Ocean are likely to be susceptible to ocean acidification and thereby likely to change their contribution to ecosystem services in the future. Further studies are required to address the poor spatial coverage, lack of community or ecosystem-level studies, and the largely unknown potential for organisms to acclimate and/or adapt to the changing conditions.

Predicting potential impacts of ocean acidification on marine calcifiers from the Southern Ocean

“…The authors also reinforced the need for more mineralogical studies to characterize a wider range of species. Further, a recent meta-analysis specifically investigated the effect of altered carbonate chemistry on marine organisms south of 60°S from 60 studies (Hancock et al, 2020). Consistent with the previous findings (discussed above), reduced survival and shell calcification rates, and increased dissolution with OA was found in adult calcifying invertebrates, along with a reduction in embryonic or larval development were also shown (Hancock et al, 2020).…”

“…With the aim of performing a meta-analysis, database searches were conducted to compile all peer-reviewed journal articles and literature reviews that investigated the effect of altered seawater carbonate chemistry on SO marine calcifiers using the criteria and methods outlined in Hancock et al (2020) (database searches completed May 2020). Articles were screened to include studies that manipulated the carbonate chemistry to investigate the effects of OA on specifically SO marine calcifiers, and after manual screening, 20 studies remained for inclusion in the meta-analysis (Fig.…”

“…The effects of OA on the following biological responses were investigated: development (bivalves, sea stars and sea urchins; fertilization rate or normal development), growth rate (brachiopods, pteropods and coccolithophores), shell state (bivalves, limpets, pteropods and sea snails; adult calcification or dissolution rate), coccolith volume (coccolithophores) and survival (sea urchins). The statistical analyses of the data are explained in detail in Hancock et al (2020). In brief, for each study the ln-transformed response ratio to OA was calculated using the ambient treatment (<500 μatm) and highest CO 2 /lowest pH treatment (up to μatm 1500 CO 2 ).…”

Meta‐analysis of multiple driver effects on marine phytoplankton highlights modulating role ofpCO2

“…Figure 3b conceptually illustrates how temperature dependence in solubility could modulate the p CO 2 dependence and explains why polar species are already negatively impacted by p CO 2 levels that are not detrimental to species thriving in warmer waters. A recent meta‐analysis on the effect of ocean acidification on Southern Ocean phytoplankton indeed shows that p CO 2 levels higher than 1,000 µatm become detrimental for most of the investigated traits (Hancock et al., 2020). Half of the Southern Ocean studies included in our meta‐analysis were conducted at 800 µatm, indicating that growth‐dampening effects can already occur within this century even under CO 2 emission scenario SSP3‐7.0 that is less extreme than the “worst‐case” scenario (SSP5‐8.5; O’Neill et al., 2016).…”

“…The effects of multiple drivers on marine phytoplankton have been reviewed in the past (e.g., Deppeler & Davidson, 2017; Edwards et al, 2016; Gao et al., 2012, 2018, 2019; Häder & Gao, 2015). Meta‐analyses, however, deal either with single driver effects (e.g., Dupont et al, 2010; Dutkiewicz et al., 2015; Hancock et al, 2020; Kroeker et al., 2013), only two specific drivers (e.g., Harvey et al, 2013), or only specific phytoplankton groups (e.g., Brandenburg et al, 2019; Crain et al., 2008; Daufresne et al, 2009; Przeslawski et al., 2015). In short, all these investigations reveal substantial nonadditive interactions of multiple drivers on the growth, photosynthesis, and functional traits such as cell size or calcification.…”