Phytoplankton production after the collapse of the Larsen A Ice Shelf, Antarctica

摘要

Part of the Larsen A Ice Shelf (64°15'S to 74°15'S) collapsed during January 1995. A first oceano-graphic and biological data set from the newly free waters was obtained during December 1996. Typical shelf waters with temperatures near and below the freezing point were found. A nutrient-rich water mass (max: PO_4~(3-) 1.80 μmol L~(-1) and NO_4~(-) 27.64 μmol L~(-1)) was found between 70 and 200 m depth. Chlorophyll-α (Chl-α) values (max 14.24 μg L~(-1)) were high; surface oxygen saturation ranged between 86 and 148%. Diatoms of the genera Nitzschia and Navicula and the prymnesiophyte Phaeocystis sp. were the most abundant taxa found. Mean daily primary production (Pc) estimated from nutrient consumption was 14.80 ± 0.17 mgC m~(-3) day~(-1). Pc was significantly correlated with total diatom abundance and Chl-α. Calculated ΔpCO_2 (difference of the CO_2 partial pressure between surface sea-water and the atmosphere) was -30.5 μatm, which could have contributed to a net CO_2 flux from the atmosphere to the sea and suggests the area has been a CO_2 sink during the studied period. High phytoplankton biomass and production values were found in this freshly open area, suggesting its importance for biological CO_2 pumping.