Sampling in low oxygen aquatic environments: The deviation from anoxic conditions

Studies of the impact hypoxic or anoxic environments on both climate and ecosystems rely a detailed characterization oxygen (O2) distribution along water column. The former trivial separation between oxic conditions is now often redefined as blurry concentration range in which aerobic anaerobic processes might coexist, situ during experimental incubations. O2 concentrations such incubations have been assumed to be equal levels, but was rarely measured. In order evaluate actual samples collected from low-oxygen environments, series measurements were performed Pacific minimum zones. Our results show significant deviation by Niskin bottles where leakage bottle material resulted up 1 ?M. Subsequent sampling further increased contamination. Sampling analysis Winkler method variable apparent 2–4 Two common procedures avoid atmospheric contamination also tested: allowing gentle overflow keeping submersed portion sampled water. Both similar with values 0.5–1.5 ?M when immediately closed optical sensors, 3–4 analyzed method. titration thus not suited for low-O2 samples. It can concluded that incubation under requires deoxygenation after conventional sampling.