|Amy E. Maas, Karen F. Wishner, and Brad A. Seibel, |
Metabolic suppression in thecosomatous pteropods as an effect of low temperature and hypoxia in the Eastern Tropical Pacific, Marine Biology, 2012
Many pteropod species in the Eastern Tropical Pacific Ocean migrate vertically each day, transporting organic matter and respiratory carbon below the thermocline. These migrations take species into cold (15- 10º C) hypoxic water (> 20 µmole O2 kg-1) at depth. Suppression of aerobic metabolism, as a response to low temperatures and hypoxia, modifies the contribution of these animals to the biological pump. We measured the vertical distribution, oxygen consumption and ammonia excretion for seven species of pteropod, Hyalocylis striata, Creseis virgula, Clio pyramidata, Diacria quadridentata, Cavolinia longirostris, Cavolinia uncinata and Cavolinia inflexa, some of which migrate and some which remain in oxygenated surface waters throughout the day. Within the upper 200 meters of the water column, changes in water temperature result in a ~60-75% reduction in metabolic rate in all species except Cavolinia uncinata. This species was not significantly impacted by changes in water temperature. All three species tested under hypoxic conditions, Hyalocylis striata, Creseis virgula and Cavolinia longirostris, responded to low O2 with an additional ~35-50% reduction in respiratory rate. Combined, low temperature and hypoxia suppress the metabolic rate of vertical migrators by ~80-90%. These results shed light on the ways in which expanding regions of hypoxia and surface ocean warming may impact pelagic ecology.