Sediment and pore water collection:
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Short sediment cores were collected using a Bowers & Connelly megacorer, a multiple coring device that can collect ~20-40 cm long sediment cores with undisturbed sediment surfaces. Megacorer cores were either sectioned for solid phase analysis, profiled with polarographic microelectrodes to determine dissolved O2 concentrations, or sectioned in a cold van under N2 for pore water sample extraction.
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Dissolved oxygen analyses:
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This was carried out by microprofiling sediment cores in a cold room using voltametric gold-amalgam (Au/Hg) microelectrodes, as described in detail elsewhere (Brendel and Luther, 1995; Luther et al., 1998; Luther et al., 2008). An Analytical Instrument Systems model DLK-100 voltammetric analyzer was used for all measurements, with profiling carried out using an AIS computer-controlled automated micromanipulator. Oxygen was determined by linear-sweep voltammetry (voltage range: -0.1 to -1.8 V, scan rate: 200 mV/s), and quantified based on the peak height at roughly -0.3 V. Electrodes were calibrated using a two-point calibration curve with O2 saturated bottom water and the electrode response in the deeper O2-free zone of the sediments (Cai and Sayles, 1996). Five scans were carried out at each depth, with the last three scans typically averaged for concentration determinations.
BCO-DMO Data Manager Processing Notes:
\n* Data from file "O2 data.txt" imported into the BCO-DMO data system.
\n* added a conventional header with dataset name, PI name, version date
\n* modified parameter names to conform with BCO-DMO naming conventions (spaces, +, and - changed to underscores).
\n* blank values in this dataset are displayed as "nd" for "no data." nd is the default missing data identifier in the BCO-DMO system.
\n* Joined with supplemental station information file to add lat and lon into the dataset.
\n* Added column for ISO_DateTime_UTC in 8601 format from fields in local time UTC-3.