| Summary: | Two of the major climate change factors expected to effect marine life, in the near future are changes in seawater temperature and pH. The Intergovernmental Panel on Climate Change, IPCC, assessment report from 2013 predicts a pH drop between 0.14 and 0.35 pH units from the current average of 8.1 in the next century, which is significant over that time period. The IPCC also predicts a global average increase in sea surface temperature of 1oC to 3oC. Many studies of these future changes have been shown to negatively impact marine invertebrates, especially calcifying organisms, through their survival, calcification, abundance, growth, and development. Echinoderm larvae are among the organisms most negatively impacted by ocean acidification. Though many single stressor studies have been preformed on a wide range of organisms, and echinoderm species, much less is know about the effects of multiple stressors. Here, two closely related echinoid species, one tropical Arachnoides placenta, and one temperate Fellaster zelandiae, are tested under the combine stressors of reduced pH and increased temperature. This study found that fertilisation was impacted by an interaction between the two stressors, and embryological and larval morphometrics are likely to be impacted by near future warming, with a negative interactive effect with pH to A. placenta, and possible beneficial effect for the F. zelandiae population studied. Both survival and embryological development are not likely to be negatively impacted by future changes in pH and temperature. Finally, both A. placenta and F. zelandiae have the potential to acclimate to moderate increases in sea surface temperature, as long as evidence of acclimation is observed among current populations residing in thermally variant habitats.
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