Metabolic response of Antarctic pteropods (Mollusca: Gastropoda) to food depriviation and regional productivity

Pteropods are an abundant group of pelagic gastropods that, although temporally and spatially patchy in the Southern Ocean, can play an important role in food webs and biochemical cycles. We found that the metabolic rate in Limacina helicina antarctica is depressed (∼23%) at lower mean chlorophyll a (chl a) concentrations in the Ross Sea. To assess the specific impact of food deprivation on these animals, we quantified aerobic respiration and ammonia (NH ₃) production for 2 dominant Antarctic pteropods, L. helicina antarctica and Clione limacina antarctica. Pteropods collected from sites west of Ross Island, Antarctica were held in captivity for a period of 1 to 13 d to determine their metabolic response to laboratory-induced food deprivation. L. helicina antarctica reduced oxygen consumption by ∼20% after 4 d in captivity. Ammonia excretion was not significantly affected, suggesting a greater reliance on protein as a substrate for cellular respiration during starvation. The oxygen consumption rate of the gymnosome, C. li macina antarctica, was reduced by ∼35% and NH ₃ excretion by ∼55% after 4 d without prey. Our results indicate that there is a link between the large scale chl a concentrations of the Ross Sea and the baseline metabolic rate of pteropods which impacts these animals across multiple seasons.