Temperature and pH effects on feeding and growth of Antarctic krill

Grace Saba1, Abigail Bockus2, Ryan L Fantasia3, Caroline Tracy Shaw4, Monisha Sugla3 and Brad Seibel5, (1)Mid-Atlantic Regional Association Coastal Ocean Observing System and Rutgers University, Department of Marine and Coastal Science, New Brunswick, NJ, United States, (2)University of Rhode Island, Biological Sciences, Kingston, RI, United States, (3)Rutgers University, Department of Marine and Coastal Science, New Brunswick, NJ, United States, (4)University of South Florida, College of Marine Science, St Petersburg, FL, United States, (5)University of South Florida St. Petersburg, St Petersburg, FL, United States
Rapid warming in the Western Antarctic Peninsula (WAP) region is occurring, and is associated with an overall decline in primary, secondary, and higher trophic levels, including Antarctic krill (Euphausia superba), a key species in Antarctic food webs. Additionally, there are predictions that by the end of this century the Southern Ocean will be one of the first regions to be affected by seawater chemistry changes associated with enhanced CO2. Ocean acidification and warming may act synergistically to impair animal performance, which may negatively impact Antarctic krill. We assessed the effects of temperature (ambient temperature, ambient +3 degrees C) and pH (Experiment 1 = 8.0, 7.7; Experiment 2 = 8.0, 7.5, 7.1) on juvenile Antarctic krill feeding and growth (growth increment and intermolt period) during incubation experiments at Palmer Station, Antarctica. Food intake was lower in krill exposed to reduced pH. Krill intermolt period (IMP) was significantly lower in the elevated temperature treatments (16.9 days) compared to those at 0 degrees (22.8 days). Within the elevated temperature treatment, minor increases in IMP occurred in krill exposed reduced pH. Growth increment (GI) was lower with decreased pH at the first molt, and this was exacerbated at elevated temperature. However, differences in GI were eliminated between the first and second molts suggesting potential ability of Antarctic krill to acclimate to changes in temperature and pH. Reductions in juvenile krill growth and feeding under elevated temperature and reduced pH are likely caused by higher demands for internal acid-base regulation or a metabolic suppression. However, the subtlety of these feeding and growth responses leaves an open question as to how krill populations will tolerate prolonged future climate change in the Antarctic.