Assessing the Impact of Elevated Temperatures on Caribbean King Crab Physiology 

Gillian Smith, Taylor Queen, Jason Spadaro, Philip Gravinese
Eckerd College, Marine Science Discipline

Increasing ocean temperatures have degraded Florida's coral reefs, reducing coral cover and increasing macroalgae abundance. The herbivorous grazing activity of Caribbean king crabs has gained interest among reef managers, making them attractive for coral restoration efforts, yet no studies have examined their tolerance to the same thermal stress that corals face. We determined how acute thermal stress impacts the physiology of ovigerous king crabs at two temperature treatments: 28°C and 32°C. Experiments were conducted using two Florida Keys subpopulations (Upper vs. Lower). Hemolymph samples were collected and measured for lactate and protein serum at 1 day, 5 days, and the “last day” of the experiment, which was defined as 24 hours after the crab had hatched. Crab stress levels were determined using a righting test. Closed respirometry was used to estimate metabolic rates after 7 days of exposure to the treatments. At the higher temperature, Lower Keys crabs showed a 20% increase in lactate, whereas Upper Keys crabs only showed a 3% increase in lactate. Both populations consumed 35%–45% more oxygen in the 32°C temperature treatment. Our results suggest that thermal extremes cause sublethal physiological stress with low mortality, indicating that the species can tolerate acute anaerobic metabolism. Our work shows that both populations are tolerant to thermal stress, and outplanting larger crabs from the Upper Keys population may be more beneficial because they seem to be more resilient compared to Lower Key crabs.