Summary: | In recent decades, increasing atmospheric CO2 levels have contributed to the acidification of the world’s oceans. The absorption of CO2 and associated decrease in pH, cause a decrease in seawater carbonate ion concentrations. Marine organisms, including sea urchins, use calcium carbonate for building critical anatomical structures, without which they cannot survive. Declines in sea urchin populations can have economic and ecological effects, as adult sea urchins are important commercially harvested invertebrates and both larvae and adults play critical roles in maintaining ecological balance in marine habitats. In our study, we focused on larval sea urchins, which are particularly vulnerable to pH changes due to their small size and use of calcium building skeletal elements during critical developmental stages. To understand the effect of acidification on larval sea urchins, green sea urchin (Lytechinus variegatus) larvae were exposed to different pHs in the environmentally realistic range of 7.6-8.4, and the effects on early development and mortality were recorded. Increased developmental abnormalities and mortality were expected in more acidic environments. Our results indicate that the most severe developmental abnormalities and highest mortality occurred in larvae exposed to the lowest pH. These results suggest that acidic seawater, at pH values currently found in the world’s oceans, can adversely affect sea urchin larval development, which can, in turn, have negative ecological and economic impacts.
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