title: Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice.
abstract: The Arctic Ocean already experiences areas of low pH and high CO2, and it is expected to be most rapidly affected by future ocean acidification (OA). Copepods comprise the dominant Arctic zooplankton; hence, their responses to OA have important implications for Arctic ecosystems, yet there is little data on their current under-ice winter ecology on which to base future monitoring or make predictions about climate-induced change. Here, we report results from Arctic under-ice investigations of copepod natural distributions associated with late-winter carbonate chemistry environmental data and their response to manipulated pCO2 conditions (OA exposures). Our data reveal that species and life stage sensitivities to manipulated OA conditions were correlated with their vertical migration behavior and with their natural exposures to different pCO2 ranges. Vertically migrating adult Calanus spp. crossed a pCO2 range of >140 μatm daily and showed only minor responses to manipulated high CO2. Oithona similis, which remained in the surface waters and experienced a pCO2 range of <75 μatm, showed significantly reduced adult and nauplii survival in high CO2 experiments. These results support the relatively untested hypothesis that the natural range of pCO2 experienced by an organism determines its sensitivity to future OA and highlight that the globally important copepod species, Oithona spp., may be more sensitive to future high pCO2 conditions compared with the more widely studied larger copepods.
authors.affiliation: College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
authors.forename: Ceri N
authors.initials: CN
authors.lastname: Lewis
authors.forename: Kristina A
authors.initials: KA
authors.lastname: Brown
authors.forename: Laura A
authors.initials: LA
authors.lastname: Edwards
authors.forename: Glenn
authors.initials: G
authors.lastname: Cooper
authors.forename: Helen S
authors.initials: HS
authors.lastname: Findlay
mesh_terms: D025041:Animal Migration / Q000502:physiology; D000818:Animals; D001110:Arctic Regions; D002245:Carbon Dioxide; D033342:Copepoda / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D009792:Oceans and Seas; D012621:Seasons; D015048:Zooplankton / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide
keywords: climate change; diel vertical migration; ecophysiology; pH response