Particle fluxes and composition at two mooring sites in the Polar Front Region

• Main Authors: Fischer, Gerhard, Gersonde, Rainer, Wefer, Gerold
• Format: Dataset
• Language: English
• Published: PANGAEA 2002
• Subjects: ANT-V/4; ANT-XII/2; ANT-XII/4; BO1; BO1_trap; BO3; BO3_trap; BO5; Bouvet Island; Center for Marine Environmental Sciences; MARUM; MOOR; Mooring; Mooring (long time); MOORY; PF1; PF3; PF5_trap; PF7; PF8; Polar Front; Polarstern; PS10; PS33; PS35 06AQANTXII_4; South Atlantic Ocean; Trap; Sea ice; Southern Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.760873; https://doi.org/10.1594/PANGAEA.760873

Particle fluxes and composition were examined over 5 years at two mooring sites in the Polar Front Region (site PF: 50°09.S, 5°50.E) and in the marginal winter sea-ice zone (site BO: 54°30.S, 3°20.W) in the eastern Atlantic Sector of the Southern Ocean. Seasonality, interannual variability and the magnitude of total mass fluxes were higher at site BO compared to PF. Five-year averages and standard deviations (1Sigma) of total mass fluxes were 19.6±18.5 and 24.8±29.9 g m**-2 at PF and BO, respectively. Peak fluxes at site BO occurred in January 1995, but the highest peak was measured in February 1991 (almost 1300 mg m**-2 d**-1) followed by post-bloom sedimentation in March through May. This would imply a time shift of several months between the onset of sea-ice retreat in October and major sedimentation events recorded in January/February with the upper BO traps. At site PF, highest fluxes of about 500 mg m**-2 d**-1 were found between December and March. Blooms at site BO, influenced by sea ice as indicated by diatom species composition, seem to occur more sporadically (e.g., in 1991 and 1995). Annual diatom fluxes were 11.8x10**6 and 20x10**6 valves m**-2 during the deployments PF3 (1990) and BO1 (1991), respectively. At PF3, Fragilariopsis kerguelensis (37%) and Thalassionema nitzschioides fo1 (26.5%) dominated diatom flux, while F. kerguelensis (29%) and sea-ice-related algae (40%) were the main contributors to total diatom flux at site BO. During deployment BO1, the bloom collected in February was characterized by a very high molar Si:C of 8.8 that decreased almost continuously during the post-bloom phase, reaching a value of 1 in May. This change, however, was not documented in diatom species composition. We obtained a significant linear increase of biogenic opal with organic carbon fluxes at site PF and a highly significant but exponential relationship at site BO. Higher annual total mass fluxes were recorded at site BO, primarily due to elevated opal and lithogenic fluxes, corresponding to a higher ...