Assessing the State of Pteropod Shells and Ocean Acidification in Washington Marine Waters

Abstract

The relationship between pteropod shell dissolution and waters undersaturated with aragonite has been well documented (Bednarsek et al 2012). Low aragonite saturation levels decrease the availability of carbonate ions in the water column, causing aragonite to dissolve out of pteropod shell structures. The onset of ocean acidification has decreased the aragonite saturation states across the globe. While studies along the Washington coast have documented widespread pteropod dissolution during peak upwelling season, the state of pteropods during other seasons is unknown (Bednarsek et al 2014). Pteropods exposed to pCO2 levels that exist within the Puget Sound have experienced dissolution in situ, but there has been no study done to date that examines the state of pteropods in the Puget Sound (Busch et al 2014). This study found widespread pteropod dissolution off the coast of Washington during the downwelling season with saturated surface waters, suggesting that even partial undersaturation of the water column can have deleterious effects on pteropod shells. Two stations examined from within the Puget Sound found severe dissolution in all pteropod samples and highly undersaturated waters, pointing towards conditions that are unsuitable for pteropods within the Puget Sound. While it is outside of this scope of this study to definitively conclude that ocean acidification is driving this, it is likely contributing to these damaging states.