The Impacts of Elevated Temperature and Reduced pH on Juvenile Stone Crab Physiology 

Increasing atmospheric carbon dioxide is simultaneously reducing ocean pH and warming seawater temperatures globally. Current models predict that by the end-of-century seawater temperatures will increase by 2-4°C and pH will be reduced by 0.4 units. These changes in the ocean can result in stressful conditions for marine species, especially during their earlier life cycle when they are still developing the physiological mechanism needed to tolerate such changes. Here we tested how simultaneous stressors like elevated temperature and reduced seawater pH impact the physiology of newly settled juvenile stone crabs (Menippe mercenaria). To determine the impact of elevated temperature and reduced pH on juvenile stone crab physiology, individuals were exposed to ambient (28°C, pH 7.8) and end-of-century conditions (32°C, pH 7.6) for 7 days. Juvenile crabs stress levels were determined daily using the lethargy and righting test which measured their ability to right themselves within 3 seconds after being flipped dorsally and respond to a stimulus probe. Respirometry was measured to determine metabolic rates after exposure to the treatments. Results indicate, on average, juveniles consume the highest oxygen concentration in end-of-century conditions, with a 15.7% higher respiration rate in the end-of-century treatment relative to the control. Across all trials, larger crabs (CW > 9.0mm) consumed 18.3% more oxygen than smaller individuals (CW ≤ 7.0mm). The results suggest that warming oceans will result in greater physiological stress on juvenile stone crabs which may result in lower recruitment years and threaten the future sustainability of the fishery.

For more information: amblau@eckerd.edu