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EARTH SCIENCE > Oceans > Ocean Chemistry > Organic Matter

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  • During passage from Stanley (Falklands Islands) to South Georgia, Stanley to Rothera and within the Western Core Box, 14 depth profiles, 70 surface seawater samples and 60 air samples were analysed for trace gas concentrations. In the Western Core Box, 6 CTD casts (3 off-shelf and 3 on-shelf) were carried out. Seawater and air samples were analysed for selected alkyl nitrates and organohalogens using a gas chromatograph - mass selective detector (GC-MSD). Data collected on biological and physical processes occurring within these regions was also used to compare alkyl nitrate and organo-halogen dynamics in these two geographically-close but hydrodynamically different ocean regions.

  • Conductivity-Temperature-Depth (CTD) casts were conducted to describe the physical structure of the water column and to provide water samples for nutrient and particulate matter analyses from the James Clark Ross. A CTD transect was also conducted on a cruise across the mouth of Marguerite Bay (it was the intention to cover the entire mouth, but sea ice prevented this from happening), and through the trough leading towards the mooring sites. These casts were used to sample nutrients (NO3-, NO2-, Si(OH)4); nutrient isotopes 13DIC (dissolved inorganic carbon) 15NO3; bulk organic POC/PON (particulate organic carbon/nitrogen); bulk organic delta 13POC and delta 15PON.

  • Two moorings were deployed and recovered using the James Clark Ross (cruise numbers: JR112/113, JR155). One was deployed in Ryder Bay at the Rothera Oceanographic and Biological Time Series (RaTS) oceanographic station midway between Rothera Point and Leonie Islands. The other was deployed in deep water in northern Marguerite Bay. The moorings were used to monitor particle flux, currents, salinity and temperature. Two sediment traps on each mooring were used to measure biogenic flux from surface waters to the seafloor and quantify changes down the water column.

  • Water samples were collected from Ryder Bay at the Rothera Time-Series (RaTS) site, using a small boat. A biogeochemical profile was performed at the following 5 depths: 0m (surface), 5m, 10m, 15m and 25m, for four RaTS events on: 7 January, 13 January, 19 January and 1 February 2005. Samples were taken for: phytoplankton nitrate, ammonium and urea uptake measurements, using stable isotope incubations and also primary production PvE curves were produced using 14C radioisotope incubations; Dissolved macronutrients (nitrate, silicate, phosphate, and urea); Surface dissolved iron. A scaled-down sampling RaTS event was performed by the Rothera Marine Assistants involving sampling for all above measurements once every 3 weeks at the 5m depth only at the RaTS site.