Dissolved organic matter in the Southern Ocean

Abstract

The main objective of the present study was to investigate the spatial and temporal distribution of dissolved organic matter in coastal, oceanic waters and sea ice of the Southern Ocean.
The distribution and dynamics of dissolved and particulate organic matter were
investigated in surface waters at a shelf and oceanic station off the island of South Georgia in the South Atlantic sector of the Southern Ocean during an austral spring bloom. A weak coupling was observed between bacterial and phytoplankton activity. Dissolved organic carbon and nitrogen concentrations were in a similar range at both sites. The correlation observed between particulate organic carbon and nitrogen was not found for the dissolved organic carbon and nitrogen pools.
A time series study was conducted at the Rothera Time Series site in coastal
waters of the Antarctic Peninsula over four consecutive years (austral summer
1997-austral summer 2001). Distinct seasonal changes in the organic matter
concentrations were discerned. Dissolved and particulate organic carbon peaked in austral summer in correspondence with greatest phytoplankton abundance and
decreased to negligible values in winter. A significant interannual variation was
observed, with increasing dissolved organic matter concentration and
phytoplankton abundance over time.
Dissolved and particulate organic carbon distribution was investigated in profiles
of first and second year winter pack ice along a transect across the Weddell Sea.
The study indicates an enrichment of dissolved and particulate organic matter in
second-year sea ice.
The incorporation of dissolved organic matter in brine and ice was investigated in
controlled experiments in virtually abiotic conditions. Inorganic nutrients were
conservatively enriched in brine in comparison to water and ice phases, consistent with the processes of sea ice formation and brine rejection. Dissolved organic carbon was also enriched in brine but was more variable and enriched in
comparison to the ranges expected from purely physical dilution, suggesting a
different concentration effect of dissolved organic carbon in brine in comparison to inorganic nutrients.

Date of Award	2002
Original language	English
Awarding Institution	University of Wales, Bangor
Sponsors	University College of North Wales Scholarship, European Union Large-Scale Facility TMR Programme & D J Crisp Fund
Supervisor	David Thomas (Supervisor) & Hilary Kennedy (Supervisor)