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Marine Ecology Progress Series

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MEPS 581:45-56 (2017)  -  DOI:

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

Julie B. Schram1,2,*, Kathryn M. Schoenrock1, James B. McClintock1, Charles D. Amsler1, Robert A. Angus1

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

ABSTRACT:  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.

KEY WORDS: Amphipod · Antarctic ecology · Benthos · Climate change · Feeding selectivity · Macroalgae · Temperature

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Cite this article as: Schram JB, Schoenrock KM, McClintock JB, Amsler CD, Angus RA (2017) Ocean warming and acidification alter Antarctic macroalgal biochemical composition but not amphipod grazer feeding preferences. Mar Ecol Prog Ser 581:45-56.

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