Abstract
Cucumaria frondosa is the largest and most abundant species of sea cucumber in the North Atlantic and Arctic oceans. C. frondosa are commercially exploited in Maine and Atlantic Canada, and sustainable stock management requires addressing knowledge gaps in their ecophysiology and bioenergetics. While temperature is commonly assumed to be the principal factor affecting the metabolic rates of aquatic ectotherms, food availability determines the feeding ecology and ultimately, growth rates of suspension feeders such as C. frondosa. Effects of temperature and food availability on individual feeding rates, metabolism, and population-level feeding activity were investigated in C. frondosa collected in May-July of 2023 from Nova Scotia, Canada (44°40’41.2’’ N 63°36’30.4’’ W). In the first experiment, temperature was increased from 5°C to 16°C by 1°C every 3 days. Maximum tentacle insertion rates (TIR; a proxy for food intake) and cloacal opening rates (COR; a proxy for respiration) increased with temperature while the total proportion of feeding individuals generally decreased. Above 12°C, novel abnormal behaviors – rhythmic openings of the mouth and incomplete TIR – emerged, and became increasingly common at higher temperatures, suggesting thermal stress. In the second experiment, phytoplankton concentration was increased from 2,000 cells ml− 1 to 50,000 cells ml− 1 by 10,000 cells ml− 1 every 3 days. TIR increased until ~ 30,000 cells ml− 1, then plateaued. The proportion of feeding individuals increased with food availability, with all individuals feeding at 40,000 cells ml− 1. These findings provide insight into the physiological performance of C. frondosa under different environmental conditions and can help inform fisheries management.