Plankton community respiration in Bransfield Strait (Antarctic Ocean) during austral spring

Abstract

Community respiration (R) was determined in Bransfield Strait from oxygen changes in water samples incubated in borosilicate bottles maintained at in situ temperature. The respiratory electron transport system (ETS) activity of seawater communities was also measured from the same samples. Both data sets were related by the regression equation: log R (mg O2 m−3 day−1)=0.462+0.730×log ETS activity mg O2 m−3 day−1) (r=0.80, n=23). From this equation and 37 ETS activity depth profiles, we calculated the integrated (0–100 m) community respiration as being in the range 1.2–4.5 g O2 m−2 day−1 (mean=2.2). These values do not differ significantly from other published results for the Arctic and Antarctic Oceans. Assuming a respiratory quotient of unity, the areal respiration ranges between 0.45 and 1.69 g C m−2 day−1 (mean=0.8). This would represent an important sink for the primary production reported for Brans Strait. The spatial distribution of community respiration showed higher values associated with the warmer and phytoplankton-rich waters outflowing from Gerlache Strait into Bransfield Strait, and with the front that separates Bellingshausen Sea waters from Weddell Sea waters. We suggest that this pattern of distribution may be related to the transport of organic matter by the Bransfield Current along the front.