Seawater carbonate chemistry and primary and bacterial production in Antarctic coastal waters during austral summer, supplement to: Westwood, Karen; Thomson, Paul G; van den Enden, Rick; Maher, L E; Wright, S; Davidson, Andrew T (2018): Ocean acidification impacts primary and bacterial production in Antarctic coastal waters during austral summer. Journal of Experimental Marine Biology and Ecology, 498, 46-60

• Main Authors: Westwood, Karen, Thomson, Paul G, van den Enden, Rick, Maher, L E, Wright, S, Davidson, Andrew T
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2018
• Subjects: Antarctic; Biomass/Abundance/Elemental composition; Coast and continental shelf; Community composition and diversity; Containers and aquaria 20-1000 L or < 1 m**2; Entire community; Laboratory experiment; Other metabolic rates; Pelagos; Polar; Primary production/Photosynthesis; Respiration; Type; Experiment; Treatment; Experiment duration; Maximum photosynthetic efficiency normalized to chlorophyll a biomass; Photosynthetic efficiency, carbon production; Saturation light intensity; Chlorophyll a; Gross primary production of carbon; Bacterial production of carbon; Bacterial production of carbon per cell; Bacteria; Carbon, organic, dissolved; Nanoflagellates, heterotrophic; Carbon, organic, particulate; Nitrate and Nitrite; Phosphate; Silicate; Ammonium; Net community production of oxygen; Respiration rate, oxygen; Gross primary production of oxygen; Ratio; Temperature, water; Salinity; Alkalinity, total; Partial pressure of carbon dioxide water at sea surface temperature wet air; Carbonate system computation flag; pH; Carbon dioxide; Fugacity of carbon dioxide water at sea surface temperature wet air; Bicarbonate ion; Carbonate ion; Carbon, inorganic, dissolved; Aragonite saturation state; Calcite saturation state; Calculated using seacarb after Nisumaa et al. 2010; Ocean Acidification International Coordination Centre OA-ICC; Austral; Davidson; Davis Station; Davis-Station; East Antarctica; Enden; Maher; Antarc*; Antarctica; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.902309; https://doi.pangaea.de/10.1594/PANGAEA.902309

Polar waters may be highly impacted by ocean acidification (OA) due to increased solubility of CO2 at colder water temperatures. Three experiments examining the influence of OA on primary and bacterial production were conducted during austral summer at Davis Station, East Antarctica (68°35′ S, 77°58′ E). For each experiment, six minicosm tanks (650 L) were filled with 200 μm filtered coastal seawater containing natural communities of Antarctic marine microbes. Assemblages were incubated for 10 to 12 days at CO2 concentrations ranging from pre-industrial to post-2300. Primary and bacterial production rates were determined using NaH14CO3 and 14C-leucine, respectively. Net community production (NCP) was also determined using dissolved oxygen. In all experiments, maximum photosynthetic rates (Pmax, mg C mg/chl a/h) decreased with elevated CO2, clearly reducing rates of total gross primary production (mg C/L/h). Rates of cell-specific bacterial productivity (μg C/cell/h) also decreased under elevated CO2, yet total bacterial production (μg C/L/h) and cell abundances increased with CO2 over Days 0–4. Initial increases in bacterial production and abundance were associated with fewer heterotrophic nanoflagellates and therefore less grazing pressure. The main changes in primary and bacterial productivity generally occurred at CO2 concentrations > 2 × present day (> 780 ppm), with the same responses occurring regardless of seasonally changing environmental conditions and microbial assemblages. However, NCP varied both within and among experiments, largely due to changing nitrate + nitrite (NOx) availability. At NOx concentrations < 1.5 μM photosynthesis to respiration ratios showed that populations switched from net autotrophy to heterotrophy and CO2 responses were suppressed. Overall, OA may reduce production in Antarctic coastal waters, thereby reducing food availability to higher trophic levels and reducing draw-down of atmospheric CO2, thus forming a positive feedback to climate change. NOX limitation may suppress this OA response but cause a similar decline. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2019-05-17.