No effect of high pCO2 on juvenile blue crab, Callinectes sapidus, growth and consumption despite positive responses to concurrent warming

Abstract

Future climate scenarios predict increases in both ocean temperature and dissolved carbon dioxide (pCO2) over the next century. Calcifying invertebrates, which depend on specific conditions of temperature and carbonate chemistry for many processes, may be especially affected by these changes. In our study, juvenile blue crab, Callinectes sapidus, were exposed to one of four temperature/pCO2 treatments (ambient/low, ambient/high, high/low, and high/high) for two complete molts. Our study is the first to examine the effect of multiple climate stressors on blue crab and therefore basic responses, including the growth per molt (GPM), inter-molt period (IMP), and food consumption, were quantified. GPM was not affected by either increased temperature or pCO2. Although increased pCO2 did not significantly influence the duration of crab IMP, crabs in warm water had significantly shorter IMP (10.6 ± 3.1 days (± SD)) than crabs in ambient water (12.5 ± 2.8 days). Increased pCO2 did not significantly affect the amount of food crabs consumed, but crabs in warm water ate significantly more food than those in ambient water. These data suggest that the impact of warming outweighs the impact of acidification in juvenile blue crab. The effects of these changes on more complex physiological parameters such as metabolism and carapace chemistry remain to be examined. Additionally, quantifying the changes to the Chesapeake Bay food web that may occur due to the observed increase in crab growth and consumption is important to ensure sustainability of this resource in the face of future climatic changes.