Antarctic crustacean grazer assemblages exhibit resistance following exposure to decreased pH

• Main Authors: Schram, Julie B, Amsler, Margaret O, Amsler, Charles D, Schoenrock, Kathryn M, McClintock, James B, Angus, Robert A
• Format: Dataset
• Language: English
• Published: PANGAEA 2016
• Subjects: Alkalinity; total; standard deviation; Antarctic; Anvers_Island_OA; Aragonite saturation state; Benthos; Bicarbonate ion; Biomass/Abundance/Elemental composition; Calcite saturation state; Calculated using CO2calc; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Community composition and diversity; Entire community; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Identification; Individuals; Laboratory experiment; Mesocosm or benthocosm; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Polar; Potentiometric titration; Rocky-shore community; Salinity; Antarc*; Antarctic Peninsula; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.862139; https://doi.org/10.1594/PANGAEA.862139

Anthropogenic atmospheric CO2 concentrations are increasing rapidly, resulting in declining seawater pH (ocean acidification). The majority of ocean acidification research to date has focused on the effects of decreased pH in single-species experiments. To assess how decreased pH may influence natural macroalgal-grazer assemblages, we conducted a mesocosm experiment with the common, chemically defended Antarctic brown macroalga Desmarestia menziesii and natural densities of its associated grazer assemblage, predominantly amphipods. Grazer assemblages were collected from the immediate vicinity of Palmer Station (64°46'S, 64°03'W) in March 2013. Assemblages were exposed for 30 days to three levels of pH representing present-day mean summer ambient conditions (pH 8.0), predicted near-future conditions (2100, pH 7.7), and distant-future conditions (pH 7.3). A significant difference was observed in the composition of mesograzer assemblages in the lowest pH treatment (pH 7.3). The differences between assemblages exposed to pH 7.3 and those maintained in the other two treatments were driven primarily by decreases in the abundance of the amphipod Metaleptamphopus pectinatus with decreasing pH, reduced copepod abundance at pH 7.7, and elevated ostracod abundance at pH 7.7. Generally, the assemblages maintained at pH 7.7 were not significantly different from those at ambient pH, demonstrating resistance to short-term decreased pH. The relatively high prevalence of generalist amphipods may have contributed to a net stabilizing effect on the assemblages exposed to decreased pH. Overall, our results suggest that crustacean grazer assemblages associated with D. menziesii, the dominant brown macroalgal species of the western Antarctic Peninsula, may be resistant to short-term near-future decreases in seawater pH.