The potential role of microbial community composition and metabolism in air-sea ΔpCO2 variation in the western Antarctic Peninsula and the Weddell Sea.

• Main Authors: Moreau, Sébastien, di Fiori, Eugenia, Schloss, Irene, International Polar Year conference
• Other Authors: UCL - SST/ELI/ELIC - Earth & Climate
• Format: Conference Object
• Language: English
• Published: 2012
• Subjects: Antarctic; Antarctic Peninsula; Anvers; Anvers Island; Weddell; Weddell Sea; Antarc*
• Online Access: http://hdl.handle.net/2078/122279

The CO2 and O2 dynamics in the Western Antarctic Peninsula (WAP) and the Weddell Sea waters were studied in relation with 1) the biomass of phytoplankton, 2) the primary production and respiration of the microbial community and 3), for the first time, the phytoplankton composition, during four consecutive summers and falls (2002, 2003, 2004 and 2005). In the whole WAP, the areal average of ΔpCO2 for the three years studied (2002, 2003 and 2004) was significantly negative (-20.04 ± 44.3 µatm, p < 0.01) during the summer-fall period, suggesting that the WAP behaved as a CO2 sink. In the southern WAP (i.e. south of Anvers Island), ΔpCO2 was significantly negative (-43.60 ± 39.06 µatm) during fall while, in the northern WAP (i.e. north of Anvers Island), ΔpCO2 values showed a more complex distribution during summer and fall (-4.96 ± 37.6 and 21.71 ± 22.39 µatm, respectively). This was consistent with Chlorophyll a concentration (Chl-a), which averaged 1.03 ± 0.25 µg l-1 in the whole WAP and was significantly higher in the south of the Peninsula. Phytoplankton composition influenced Chl-a concentration with higher and lower Chl-a values for diatoms and phytoflagellates dominated communities, respectively. A significant negative correlation existed between Chl-a and ΔpCO2, indicating the potential influence of biology on CO2 exchanges between the ocean and the atmosphere. From incubation experiments performed in the northern WAP, the net community production (NCP) correlated negatively with ΔpCO2 and positively with the %O2 saturation while the community respiration was low (averaging 5.1 mmol O2 m-3 d-1). In spite of the high NCP values measured, ΔpCO2 was significantly positive in the northern WAP during the summer-fall period, indicating that this region behaved as a CO2 source. Strong mixing of the water column induced by winds and low Chl-a concentration may explain this result. On the contrary, ΔpCO2 was significantly negative in the southern WAP, possibly because of high surface water Chl-a ...