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Marine Ecology Progress Series

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MEPS 554:81-97 (2016)  -  DOI:

Seawater acidification more than warming presents a challenge for two Antarctic macroalgal‑associated amphipods

Julie B. Schram1,2,*, Kathryn M. Schoenrock1, James B. McClintock1, Charles D. Amsler1, Robert A. Angus

1Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294-1170, USA
2Present address: Oregon Institute of Marine Biology, University of Oregon, Charleston, Oregon 97420, USA
*Corresponding author:

ABSTRACT: 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.

KEY WORDS: Western Antarctic Peninsula · Crustacean · Survival · Growth · Molt frequency · Consumption rates · Climate change

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Cite this article as: Schram JB, Schoenrock KM, McClintock JB, Amsler CD, Angus RA (2016) Seawater acidification more than warming presents a challenge for two Antarctic macroalgal‑associated amphipods. Mar Ecol Prog Ser 554:81-97.

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