Seawater carbonate chemistry and Microalgal photophysiology and macronutrient distribution in summer sea ice in the Amundsen and Ross Seas, Antarctica

• Main Authors: Torstensson, Anders, Fransson, Agneta, Currie, Kim I, Wulff, Angela, Chierici, Melissa
• Format: Dataset
• Language: English
• Published: PANGAEA 2018
• Subjects: Alkalinity; total; Antarctic; Aragonite saturation state; Bacteria; Bicarbonate ion; Biomass/Abundance/Elemental composition; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Coast and continental shelf; Core; DEPTH; ice/snow; Electron transport rate efficiency; Entire community; Field observation; Fucoxanthin; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Ice thickness; Identification; Irradiance; LATITUDE; Light saturation; LONGITUDE; Maximal electron transport rate; relative; Maximum photochemical quantum yield of photosystem II; Nitrate and Nitrite; Non photochemical quenching; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phosphate; Polar; Primary production/Photosynthesis; Salinity; Section; Silicate; Station label; Temperature; water; Antarc*; Antarctica; ice algae; Ocean acidification; Sea ice; Southern Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.924295; https://doi.org/10.1594/PANGAEA.924295

Our study addresses how environmental variables, such as macronutrients concentrations, snow cover, carbonate chemistry and salinity affect the photophysiology and biomass of Antarctic sea-ice algae. We have measured vertical profiles of inorganic macronutrients (phosphate, nitrite + nitrate and silicic acid) in summer sea ice and photophysiology of ice algal assemblages in the poorly studied Amundsen and Ross Seas sectors of the Southern Ocean. Brine-scaled bacterial abundance, chl a and macronutrient concentrations were often high in the ice and positively correlated with each other. Analysis of photosystem II rapid light curves showed that microalgal cells in samples with high phosphate and nitrite + nitrate concentrations had reduced maximum relative electron transport rate and photosynthetic efficiency. We also observed strong couplings of PSII parameters to snow depth, ice thickness and brine salinity, which highlights a wide range of photoacclimation in Antarctic pack-ice algae. It is likely that the pack ice was in a post-bloom situation during the late sea-ice season, with low photosynthetic efficiency and a high degree of nutrient accumulation occurring in the ice. In order to predict how key biogeochemical processes are affected by future changes in sea ice cover, such as in situ photosynthesis and nutrient cycling, we need to understand how physicochemical properties of sea ice affect the microbial community. Our results support existing hypothesis about sea-ice algal photophysiology, and provide additional observations on high nutrient concentrations in sea ice that could influence the planktonic communities as the ice is retreating.