THE EFFECTS OF OCEAN ACIDIFICATION AND ELEVATED TEMPERATURE ON THE VERTICAL SWIMMING BEHAVIOR OF THE FLORIDA STONE CRAB 

The combined effects of coastal acidification and elevated seawater temperatures are resulting in changes in behavior, altering physiology and reducing survival. One of the species that may be affected by these stressors is the Florida stone crab, Menippe mercenaria, which is a $30 million dollar per year fishery. This study determined the impacts of reduced seawater pH and elevated seawater temperatures on the larval swimming response to gravity (geotaxis) by monitoring the speed and direction of larval stone crabs when exposed to both singular and simultaneous climate stressors. We used a fully-crossed experimental design with two treatments (pH and temperature) each with two levels (28℃ and 32℃; pH = 8.0 and 7.6). Larvae were raised in each treatment and harvested at each larval stage (stages I–III) for geotaxis experiments. All geotaxis experiments were conducted in a light tight room using individual larvae from ten independent broods. Our results show that there was no difference in larval upward swimming speeds. The majority (> 65%) of stage 1 and 2 larvae swam upwards in all four treatments; however, there was a significant change in swimming direction for stage 3 larvae in the elevated temperature, reduced pH treatment (only 28% swam upwards). This change in swimming direction in the elevated temperature, reduced pH treatment suggests that stone crab populations may have difficulty migrating beyond their range with future changes in climate.

Acknowledgments: We thank A. Smith, G. Faraci, L. Trevillian, C. Potts, J. McFadden, T. White, T. Queen, S. Sujo, L. McKeever for assistance in data collection and analysis. Meberg was supported by the Eckerd College Marine Science First Year Research Program. This research is funded by a National Science Foundation Biological Oceanography Grant (award number OCE-2049047).

For more information: rkmeberg@eckerd.edu