Concentrations of total organic carbon on vertical profiles in waters of the Weddell Sea measured on water bottle sample during POLARSTERN cruise ANT-X/6
Concentrations of dissolved organic carbon (DOC) and nitrogen (DON) were measured during early austral Spring 1992 at a number of stations along the 6°W meridian between 47° and 60°S. This included the Polar Front in the north, the zone of melting sea-ice in the south, and waters of the Antarctic Ci...
| Main Authors: | , , , |
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| Format: | Dataset |
| Language: | English |
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PANGAEA - Data Publisher for Earth & Environmental Science
2008
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| Subjects: | |
| Online Access: | https://dx.doi.org/10.1594/pangaea.696180 https://doi.pangaea.de/10.1594/PANGAEA.696180 |
| Summary: | Concentrations of dissolved organic carbon (DOC) and nitrogen (DON) were measured during early austral Spring 1992 at a number of stations along the 6°W meridian between 47° and 60°S. This included the Polar Front in the north, the zone of melting sea-ice in the south, and waters of the Antarctic Circumpolar Current in between. Concentrations of DOC were low in deep water (34–38 ?M) with generally similar or slightly higher values in the surface mixed layer (38–55 ?M). DOC:DON ratios are wider in surface water than in deep water, i.e. surface accumulations contain relatively C-rich dissolved organic matter. The highly variable distribution of the surface DOC was not related to hydrographic or biotic features (fronts, plankton development) indicating the lability and transient occurrence of this material.Growth rates of bacteria were determined in subsamples from 51 0.8-?m-filtered batches of seawater incubated in the dark at in-situ temperature. Thymidine and leucine uptake and bacterial biomass change as well as changes in dissolved organic carbon in the batches, and oxygen consumption in parallel incubations correlated linearly over 2 weeks of incubation which allowed extrapolation to in-situ conditions.Bacterial growth in these experiments depended strongly on the amount of initial DOC. Growth in water from greater depth (1000 m) containing 38 ?M DOC was minimal, as were DOC-decrease and oxygen consumption. Higher rates were observed in surface water slightly enriched with DOC, and highest rates in surface water amended with DOC-rich melted sea ice. Bacterial growth efficiencies (biomass C-increase vs DOC consumed) were about 30%. The experiments showed that at least 40–60% of the DOC in excess of deep water concentrations was available to bacteria. : Not filtered water samples were taken in 10 ml ampoules (sealed immediately after being acidified with phosphoric acid to pH<2, sampling), or 40 ml screw-lid vials, and measured on board the ship at the day of sampling or at the next day, or conserved frozen (-20°C) until being acidified and measured in home labs.Measurement was by high-temperature catalytic oxidation in a 10 cm column packed with 5% Pt on aluminum oxide beads at 900°C in a stream of oxygen, and CO2 detection by infrared extinction after the removal of moisture and SO2 by appropriate traps (cold trap, Mg-percarbonate, Na-pyrophosphate, tin, bronze or Sulfix). The apparatus was the dual channel Dimatek 2000 equipped with a Binos 200 detector. |
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