Influence of microbial community composition and metabolism on air-sea pCO2 variation off the western Antarctic Peninsula

MOREAU, SEBASTIEN; SCHLOSS, I. R.; MOSTAJIR, BEHZAD ; DEMERS, SERGE ; ALMANDOZ, G. O.; FERRARIO, M. E.; FERREYRA, G. A.

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 2012 vol. 446 p. 45 - 59

0171-8630

We studied CO2 and O2 dynamics in the western Antarctic Peninsula (WAP) waters in relation to (1) phytoplankton biomass, (2) microbial community primary production and respiration, and (3), for the first time, phytoplankton composition, during summer and fall in 3 consecutive years (2002, 2003 and 2004). The areal average of ΔpCO2 (the difference between surface seawater and atmospheric partial pressure of CO2) for the 3 yr was significantly negative (−20.04 ± 44.3 μatm, p < 0.01) during the summer to fall period in the region, possibly indicating a CO2 sink. In the southern WAP (i.e. south of Anvers Island), pCO2 was significantly negative (−43.60 ± 39.06 μatm) during fall. In the northern WAP (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). Chlorophyll a (chl a) concentration averaged 1.03 ± 0.25 μg l−1 and was higher in the south of the peninsula. Phytoplankton composition influenced chl a concentration with higher and lower values for diatom- and phytoflagellate-dominated communities, respectively. A significant negative correlation existed between chl a and pCO2. From incubation experiments performed in the northern WAP, respiration was low (averaging 5.1 mmol O2 m−3 d−1), and the net community production (NCP) correlated negatively with pCO2 and positively with %O2 saturation. However, despite the high NCP values measured, ΔpCO2 was significantly positive in the northern WAP during the summer to fall period. Strong mixing and lower chl a concentration may explain this result. In contrast, ΔpCO2 was significantly negative in the southern WAP, possibly because of high surface water chl a concentration.