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

Jonathan S Stark,Andrew T Davidson,Alyce M Hancock,Catherine K King,Andrew Mcminn

doi:10.1002/ece3.6205

Abstract

Southern Ocean waters are among the most vulnerable to ocean acidification. The projected increase in the CO2 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 CO2 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 CO2 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 CO2 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.

Highlights

Much of the anthropogenic atmospheric carbon dioxide (CO2) emissions is estimated to have been absorbed by the world's oceans leading to significant changes in seawater carbonate chemistry and reduced pH (Doney et al, 2012; Frölicher et al, 2015; Gattuso & Hansson, 2011; Gattuso & Lavigne, 2009; Le Quéré et al, 2018; Raven & Falkowski, 1999; Sabine et al, 2004)
By year 2100, when nearshore Antarctic waters are projected to have CO2 levels between 880 and 1,000 μatm, these waters could experience an increase in the abundance of bacteria, reduction in primary productivity, and phytoplankton communities could be become dominated by smaller cells
Invertebrates could be threatened with reductions in fertilization rate and increased larval abnormalities occurring at a CO2 concentrations above 1,500 μatm

Summary

Introduction

Much of the anthropogenic atmospheric carbon dioxide (CO2) emissions is estimated to have been absorbed by the world's oceans leading to significant changes in seawater carbonate chemistry and reduced pH (Doney et al, 2012; Frölicher et al, 2015; Gattuso & Hansson, 2011; Gattuso & Lavigne, 2009; Le Quéré et al, 2018; Raven & Falkowski, 1999; Sabine et al, 2004). Future predictions of acidification indicate that winter surface waters south of 60°S could reach 1,000 μatm by 2100 when seasonal CO2 cycles are incorporated into model predictions, and areas of the Southern Ocean could experience undersaturation in aragonite by as early as 2030 under the IPCC RCP8.5 (Kawaguchi et al, 2013; McNeil & Matear, 2008; McNeil & Sasse, 2016). The implications of the decrease in the pH and early undersaturation could be significant for many organisms within the Southern Ocean (Wittmann & Pörtner, 2013) These waters have been suggested to serve as a bellweather for the impacts of ocean acidification globally (Fabry et al, 2009; Negrete-García et al, 2019)

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