Meeting Abstract
Elevated atmospheric pCO2 concentrations are reducing seawater pH and elevating seawater temperatures along the western Antarctic Peninsula (WAP). These two factors may antagonistically, additively, or synergistically influence benthic macroalgal-associated amphipods. The gammaridean amphipods Gondogeneia antarctica and Paradexamine fissicauda are key members of the mesograzer assemblages associated with the macroalgae of the WAP. We exposed individuals of both amphipod species over a 90-day period to combinations of pH and temperature based on ambient conditions (pH 8.0, 1. 5oC) and those predicted for 2100 (pH 7.6, 3.5oC). We recorded amphipod survival and molt frequency, as well as feeding rates. Following the 90-day exposure period, we assessed growth and body composition. Reduced seawater pH significantly impacted survival in both species and an initial decline in survival corresponded with higher molt frequency. Mean feeding rates for G. antarctica were significantly higher in the reduced pH treatment. There was a significant pH-temperature interaction effect on feeding rates in P. fissicauda resulting in higher feeding rates in the reduced pH and elevated temperature treatment. Proximate body composition analysis revealed a significant pH-temperature interactive effect on whole body lipid content of G. antarctica, and lower protein levels in P. fissicauda. Overall, reduced pH dramatically impacted survival in both species, while elevated temperature induced sublethal impacts on feeding, growth, and whole body composition. Changes in pH and temperature associated with climate change are likely to impact the structure of mesograzer-macroalgal ecosystems along the WAP.
