Abstract
Ocean acidification is predicted to have severe consequences for calcifying marine organisms especially molluscs. Recent studies, however, have found that molluscs in marine environments with naturally elevated or fluctuating CO2 or with an active, high metabolic rate lifestyle may have a capacity to acclimate and be resilient to exposures of elevated environmental pCO2. The aim of this study was to determine the effects of near future concentrations of elevated pCO2 on the larval and adult stages of the mobile doughboy scallop, Mimachlamys asperrima from a subtidal and stable physio-chemical environment. It was found that fertilisation and the shell length of early larval stages of M. asperrima decreased as pCO2 increased, however, there were less pronounced effects of elevated pCO2 on the shell length of later larval stages, with high pCO2 enhancing growth in some instances. Byssal attachment and condition index of adult M. asperrima decreased with elevated pCO2, while in contrast there was no effect on standard metabolic rate or pHe. The responses of larval and adult M. asperrima to elevated pCO2 measured in this study were more moderate than responses previously reported for intertidal oysters and mussels. Even this more moderate set of responses are still likely to reduce the abundance of M. asperrima and potentially other scallop species in the world’s oceans at predicted future pCO2 levels.
Highlights
Ocean acidification has been called the ‘‘other CO2 problem’’
Fertilisation and Larvae This study found that exposure to elevated pCO2 significantly affected the early life-history of M. asperrima
The fertilisation, development to trochophore stage and shell length of D-veliger larvae all decreased at elevated pCO2
Summary
Ocean acidification has been called the ‘‘other CO2 problem’’. Anthropogenic emissions of CO2 released into the atmosphere are being absorbed by the world’s oceans causing them to acidify [1,2]. Studies on adult molluscs including the oysters Crassostrea gigas, Crassostrea virginica, Saccostrea glomerata, [13,15,16] and mussels Mytilus edulis [17,19,20] have found decreased calcification and growth in response to elevated pCO2 [19,20], perhaps because of the lowered saturation state of carbonate (CO322) and alterations to the organism’s acid-base status, which they attempt to compensate for by increasing their standard metabolic rate [21,22,23]. Reduced fertilisation success, decreased larval size and development and increased larval abnormality and mortality have been found in the oysters C. gigas, C. virginica, S. glomerata, [11,12,13,25,26,27] and mussels, Mytilus galloprovincialis, Mytilus edulis [18,28]. Molluscs are not the only phylum affected by elevated pCO2, with negative responses recorded for echinoderms, including the sea urchins Hemicentrotus pulcherrimus, Enchinometra mathaei [29,30], Paracetrotus lividus [31], Tripneustes gratilla, Pseudechinus huttoni, Evechinus chloroticus, Sterechinus neumayeri [32], Heliocidaris erythrogramma [33,34,35] and the brittle star Ophiothrix fragilis [7]
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