• Ocean warming and acidification alter Antarctic macroalgal biochemical composition but not amphipod grazer feeding preferences

      Schram, Julie B.; Schoenrock, Kathryn M.; McClintock, James B.; Amsler1, Charles D.; Angus, Robert A. (Inter-Research, 2017-10-13)
      Increased anthropogenic atmospheric CO2 concentrations have resulted in ocean warming and alterations in ocean carbonate chemistry, decreasing seawater pH (ocean acidification). The combination of ocean warming and acidification (OWA) may alter trophic interactions in marine benthic communities along the western Antarctic Peninsula (WAP). Abundant and diverse macroalgae–grazer assemblages, dominated by macroalgae (e.g. chemically defended Desmarestia anceps and D. menziesii) and gammarid amphipods (e.g. Gondogeneia antarctica), occur on the nearshore benthos along the WAP. In the present study, the amphipod G. antarctica and macroalgae D. anceps and D. menziesii were exposed for 39 and 79 d, respectively, to combinations of current and predicted near-future temperature (1.5 and 3.5°C, respectively) and pH (8.0 and 7.6, respectively). Protein and lipid levels of macroalgal tissues were quantified, and 5-way choice amphipod feeding assays were performed with lyophilized macroalgal tissues collected at time zero and following exposure to the 4 temperature-pH treatments. For D. anceps, we found a significant interactive temperature-pH effect on lipid levels and significantly lower protein levels at reduced pH. In contrast, tissues of D. menziesii exhibited significantly greater lipid levels after exposure to reduced pH, but there was no temperature effect on lipid or protein levels. Despite shifts in macroalgal biochemical composition, there were no changes in amphipod feeding preferences. Our results indicate that despite altered macroalgal nutritional quality under OWA, both macroalgae retained their ability to deter amphipod feeding. This deterrent capacity could become an important contributor to net community resistance of macroalgae−mesograzer assemblages of the WAP to predicted OWA.
    • Seawater acidification more than warming presents a challenge for two Antarctic macroalgal-associated amphipods

      Schram, Julie B.; Schoenrock, Kathryn M.; McClintock, James B.; Amsler, Charles D.; Angus, Robert A. (Inter-Research, 2016-07-08)
      Elevated atmospheric pCO2 concentrations are triggering seawater pH reductions and seawater temperature increases along the western Antarctic Peninsula (WAP). These factors in combination have the potential to influence organisms in an antagonistic, additive, or synergistic manner. The amphipods Gondogeneia antarctica and Paradexamine fissicauda represent prominent members of macroalgal-associated mesograzer assemblages of the WAP. Our primary objective was to investigate amphipod behavioral and physiological responses to reduced seawater pH and elevated temperature to evaluate potential cascading ecological impacts. For 90 d, amphipods were exposed to combinations of seawater conditions based on present ambient (pH 8.0, 1.5°C) and predicted end-of-century conditions (pH 7.6, 3.5°C). We recorded survival, molt frequency, and macroalgal consumption rates as well as change in wet mass and proximate body composition (protein and lipid). Survival for both species declined significantly at reduced pH and co-varied with molt frequency. Consumption rates in G. antarctica were significantly higher at reduced pH and there was an additive pH−temperature effect on consumption rates in P. fissicauda. Body mass was reduced for G. antarctica at elevated temperature, but there was no significant effect of pH or temperature on body mass in P. fissicauda. Exposure to the pH or temperature levels tested did not induce significant changes in whole body biochemical composition of G. antarctica, but exposure to elevated temperature resulted in a significant increase in whole body protein content of P. fissicauda. Our study indicates that while elevated temperature causes sub-lethal impacts on both species of amphipods, reduced pH causes significant mortality.
    • Using traditional ecological knowledge to understand and adapt to climate and biodiversity change on the Pacific coast of North America

      de Echeverria, V. R. W.; Thornton, Thomas F. (Springer Netherlands, 2019-10-09)
      We investigate the perceptions and impacts of climate change on 11 Indigenous communities in Northern British Columbia and Southeast Alaska. This coastal region constitutes an extremely dynamic and resilient social-ecological system where Indigenous Peoples have been adjusting to changing climate and biodiversity for millennia. The region is a bellwether for biodiversity changes in coastal, forest, and montane environments that link the arctic to more southerly latitudes on the Pacific coast. Ninety-six Elders and resource users were interviewed to record Traditional Ecological Knowledge (TEK) and observations regarding weather, landscape, and resource changes, especially as concerns what we term Cultural Keystone Indicator Species (CKIS), which provide a unique lens into the effects of environmental change. Our findings show that Indigenous residents of these communities are aware of significant environmental changes over their lifetimes, and an acceleration in changes over the last 15–20 years, not only in weather patterns, but also in the behaviour, distributions, and availability of important plants and animals. Within a broader ecological and social context of dwelling, we suggest ways this knowledge can assist communities in responding to future environmental changes using a range of place-based adaptation modes.