Metabolism of gymnosomatous pteropods in waters of the western Antarctic Peninsula shelf during austral fall

Abstract

Two species of Southern Ocean gymnosomatous pteropods with dissimilar distributional ranges were collected from western Antarctic Peninsula (WAP) shelf waters in the vicinity of Anvers, Lavoisier, Adelaide and Charcot Islands from March to April 2010 and between 0 and 500 m. The sub-Antarctic gymnosome species, Spongiobranchaea australis, typically occupies regions north of the Polar Front, whereas the true Antarctic gymnosome species, Clione antarctica, inhabits colder waters and higher latitudes. Oxygen consumption rates, ammonia excretion rates, proximate body compositions and the activities of 3 metabolic enzymes-lactate dehydrogenase, malate dehydrogenase, and citrate synthase (CS)-were determined in both gymnosome species. Oxygen consumption rates of S. australis and C. antarctica were found to be similar; however, the mean ratio of oxygen consumed to ammonia excreted (O:N, 61.26 ± 18.68:1) indicated that S. australis was oxidizing primarily lipids while C. antarctica was oxidizing a mixture of proteins and lipids (26.41 ± 14.82:1). Proximate body compositions based on percent protein, percent lipid, and carbon to nitrogen ratios, suggested larger lipid storage in C. antarctica (~5%) than in S. australis (~3%). CS activities among gymnosomes were dissimilar, and comparisons of enzyme activities were made to other Antarctic organisms. Observed differences in S. australis' physiological indicators may be related to prolonged starvation, whereas C. antarctica appears ready to survive overwintering in Antarctica. Water mass advection from the Antarctic Circumpolar Current is thought to be transporting S. australis onto the WAP shelf, and away from its typical sub-Antarctic habitat.

Environmental controls on pteropod biogeography along the Western Antarctic Peninsula

“…In contrast, C. antarctica was more abundant in cold waters associated with the coast (Suprenand et al 2015a). Gymnosome species were recorded in warmer waters (~2 C) in the WAP indicating their ability to tolerate increasingly subantarctic conditions (Suprenand et al 2015b). To the north of the PAL LTER region, high gymnosome abundance corresponded most strongly to a negative MEI in the fall and positive SAM during the summer season (Loeb and Santora 2013), although sea ice and L. antarctica abundance were not directly included in that study.…”