Vertical export of particulate organic carbon: Attenuation, composition and loss rates in the northern Barents Sea (original) (raw)
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Journal of Marine Systems, 2008
Large-volume sampling of 234 Th was conducted to estimate particulate organic carbon (POC) export in conjunction with drifting sediment trap deployments in the northern Barents Sea in July 2003 and May 2005. 234 Th-derived POC fluxes averaged 42.3± 39.7 mmol C m − 2 d − 1 in 2003 and 47.1± 30.6 mmol C m − 2 d − 1 in 2005. Sediment trap POC fluxes averaged 13.1± 8.2 mmol C m − 2 d − 1 in 2003 and 17.3 ± 11.4 mmol C m − 2 d − 1 in 2005, but better reflected the transient bloom conditions that were observed at each station within a season. Although 234 Th fluxes agreed within a factor 2 at most stations and depths sampled, sediment trap POC fluxes were lower than large-volume POC flux estimates at almost every station. This may represent an under-collection of POC by the drifting sediment traps or, conversely, an over-collection of POC by the large-volume sampling of 234 Th. It is hypothesized that the offset between the two methods is partly due to the presence of the prymnesiophyte Phaeocystis pouchetii, which potentially causes a large variation in N53-μm POC/ 234 Th ratios. Due to the large proportion of dissolved carbon or mucilage released by P. pouchetii, and because it is thought that P. pouchetii does not contribute significantly to the vertical export of biogenic matter in the Barents Sea, the application of large-volume sampling of 234 Th may yield relatively high, and possibly inaccurate POC/ 234 Th ratios. Hence, POC fluxes derived from 234 Th sampling may be inappropriate and drifting sediment traps might be a more reliable method to measure the vertical export of biogenic matter in regions that have recurrent P. pouchetii blooms, such as the Barents Sea.
Geophysical Research Letters, 2009
in the northern Laptev Sea to assess the annual variability in vertical export of particulate organic carbon (POC). The second year of deployment coincided with the record low in Arctic summer ice extent reached in 2007 that resulted in an increase in marine primary production over the Siberian shelves. POC export fluxes increased during ice melt in 2007, leading to a $2-fold increase in annual POC export relative to 2005 -2006 over the continental slope of the Laptev Sea. These results suggest that the continuous decrease of sea ice extent could sustain increased POC export in the northern Laptev Sea and adjacent seas, potentially altering marine ecosystem structure in the Siberian Arctic. Citation: Lalande, C., S. Bélanger, and L. Fortier (2009), Impact of a decreasing sea ice cover on the vertical export of particulate organic carbon in the northern Laptev Sea, Siberian