Calcifying invertebrates succeed in a naturally CO2-rich coastal habitat but are threatened by high levels of future acidification

[摘要] CO₂ emissions are leading to an acidification of theoceans. Predicting marine community vulnerability towards acidification isdifficult, as adaptation processes cannot be accounted for in mostexperimental studies. Naturally CO₂ enriched sites thus canserve as valuable proxies for future changes in community structure. Here wedescribe a natural analogue site in the Western Baltic Sea. SeawaterpCO₂ in Kiel Fjord is elevated forlarge parts of the year due to upwelling of CO₂ rich waters.Peak pCO₂ values of >230 Pa (>2300 μatm) and pH_NBS values of <7.5 are encounteredduring summer and autumn, averagepCO₂ values are ~70 Pa (~700 μatm). In contrast to previously described naturallyCO₂ enriched sites that have suggested a progressivedisplacement of calcifying auto- and heterotrophic species, the macrobenthiccommunity in Kiel Fjord is dominated by calcifying invertebrates. We showthat blue mussels from Kiel Fjord can maintain control rates of somatic andshell growth at a pCO₂ of 142 Pa (1400 μatm, pH_NBS= 7.7). Juvenile mussel recruitmentpeaks during the summer months, when high water pCO₂ values of ~100 Pa (~1000 μatm) prevail. Our findings indicate that calcifying keystonespecies may be able to cope with surface ocean pH_NBSvaluesprojected for the end of this century when food supply is sufficient.However, owing to non-linear synergistic effects of future acidification andupwelling of corrosive water, peak seawater pCO₂ in Kiel Fjord and many otherproductive estuarine habitats could increase to values >400 Pa(>4000 μatm). These changes will most likely affect calcification andrecruitment, and increase external shell dissolution.

[学科分类] 地球化学与岩石