33. Lethal effects of increasing CO2 on dominant zooplankton in the Southern Ocean

Jake. R. Wallis (1)*, Kerrie, M. Swadling (2), So. Kawaguchi (2)

1 Institute for Marine and Antarctic Studies, Hobart, Tasmania, 7004, Australia,
2 Australian Antarctic Division, Kingston, Tasmania, 7050, Australia

Ocean acidification, caused by the absorption of CO2, is at the forefront of marine research due to the largely unknown implications for marine ecosystems. An increase in studies of the implications of ocean acidification are improving our knowledge of ways in which marine organisms will likely be impacted, including physiological stress, the diminished ability of some calcifying organisms to grow and changes to the base of planktonic food-webs. Information from the Southern Ocean is lacking for zooplankton other than krill and pteropods, making it difficult to investigate the potential implications of continued CO2 increases on lower trophic interactions. This is especially true for the fundamental copepod-fish food pathway that dominates north of the Southern Boundary of the Antarctic Circumpolar Current. Work undertaken during the Australian Antarctic Kerguelen-Axis voyage during the 2016 summer will examine the effects of increased CO2 on mortality of key zooplankton species. Lethal limits will be determined for species including the small, biomass dominant copepod Oithona similis and larger copepods Calanus propinquus, Rhincalanus gigas and Calanoides acutus, all of which undertake vertical migration and thus represent a strong link in the vertical flux of carbon from surface to deep-water. The pCO2 concentrations of ambient, 750, 1000, 1250, 1500, 2000 ppm will be used to determine lethal limits via incubations and thus provide a baseline that will inform further laboratory-based experiments with these species.