Normal 0 false false false EN-US JA X-NONE The Antarctic Peninsula is one of the most rapidly changing regions of the planet due to anthropogenic climate change. The rate of air and seawater warming is currently unprecedented and is already impacting marine organisms and communities that are long adapted to stable, cold temperatures. Ocean acidification is another critical stressor that uniquely challenges marine organisms in Polar Regions. The Southern Ocean is particularly vulnerable to ocean acidification as atmospheric carbon dioxide is more soluble in low temperature waters. Moreover, Antarctic marine organisms tend to be weakly calcified, either or both because of the historical absence of shell crushing predators or the increased costs of calcification at low temperature. This renders Antarctic species more susceptible to skeletal dissolution under conditions of ocean acidification. The calcified body parts of some Antarctic marine invertebrates including representatives of the shelled sea butterflies (swimming snails) are already beginning to show evidence of dissolution due to ocean acidification. By taking a comparative and integrative approach, the present project provided an extensive evaluation of the individual and combined effects of ocean warming and acidification (decreasing pH) on aspects of the physiology, growth, behavior, and survival of ecologically important shallow-water benthic organisms. A further study provided an analysis of future impacts of ocean acidification on the species abundance and composition of crustacean grazer-seaweed assemblages that dominate shallow depths along the eight-hundred mile coast of the western Antarctic Peninsula (WAP). Additionally, we collected seawater temperature and chemistry data daily, weekly, monthly, and seasonally at a coastal site on the central WAP to document current values and their natural variability. These seawater data were then used to inform this projectÆs core organismal (single-species) and assemblage (multi-species) approaches to provide an evaluation of near-future predicted impacts of ocean warming and acidification on benthic marine organisms. Through laboratory-based experimental manipulations we found that with exposure periods of either six weeks or three months, Antarctic marine organisms (including calcified and fleshy seaweeds, limpets, snails, and amphipods) are impacted to various extents by warming and acidification. At the level of individual species of seaweeds and invertebrates, these impacts included a variety of variables associated with organismal health including but not limited to altered photosynthetic capacity and increased chemical defense in seaweeds, and weakened shell strength, alterations in feeding preferences, and changes in escape responses of invertebrates. In some instances, both warming and acidification resulted in significantly elevated rates of organismal mortality. For some of the response variables, evaluated combinations of ocean warming and acidification resulted in interactive effects that either amplified or reduced the negative impacts of exposure. In addition to single species experiments, we also conducted a multi-species analysis focusing on the diverse assemblage of crustacean grazers that are associated with the ecologically dominant, weakly chemically defended seaweeds whose interactions play a key role in determining coastal community dynamics along the WAP. While representatives of this dense grazer assemblage do not graze directly on the seaweeds, they consume and remove the more palatable microalgae that settle on (diatoms), or live within (endophytes), these large seaweeds. If left unchecked, microalgae compete with their host seaweed for light and can hinder photosynthetic capacity. Despite detec...
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