Chlorophyll a and carbon fluxes, and characteristics of the water column during summer 2008 in the Beaufort Sea

Following the extreme low ice year of 2007, primary production and the sinking export of particulate and gel-like organic material, using short-term particle interceptor traps deployed at 100 m, were measured in the southeastern Beaufort Sea during summer 2008. The combined influence of early ice retreat and coastal upwelling contributed to exceptionally high primary production (500 ± 312 mg C/m**2/day, n = 7), dominated by large cells (>5 µm, 73% ± 15%, n = 7). However, except for one station located north of Cape Bathurst, the sinking export of particulate organic carbon (POC) was relatively low (range: 38-104 mg C/m**2/day, n = 12) compared to other productive Arctic shelves. Estimates indicate that 80% ± 20% of the primary production was cycled through large copepods or the microbial food web. Exopolymeric substances were abundant in the sinking material but did not appear to accelerate POC sinking export. The use of isotopic signatures (d13C, d15N) and carbon/nitrogen ratios to identify sources of the sinking material was successful only at two stations with a strong marine or terrestrial signature, indicating the limitations of this approach in hydrographically and biologically complex Arctic coastal waters such as in the Beaufort Sea. At these two stations influenced by either coastal upwelling or erosion, the composition and magnitude of particulate sinking fluxes were markedly different from other stations visited during the study. These observations underscore the fundamental role of mesoscale circulation patterns and hydrodynamic singularities on the export of particulate organic material on Arctic shelves.

Finely dispersed fraction of particulate organic matter and primary production in sea water of the Equatorial East Pacific

Qualitative and quantitative evaluation of the finely dispersed fraction of particulate organic matter in sea water is given. It is demonstrated that in the euphotic zone of high productivity waters this fraction constitutes 86%, in waters with low productivity 61%, and in deep waters (>200 m) 53% of the organic carbon in particulate matter. Formation of the finely dispersed fraction and its role in distribution of energy in the detrital food chain of the ecosystem are discussed.

Primary production and chlorophyll a in waters of the Kara Sea in September 2007

These studies were performed from September 10 to 29, 2007 in the Kara Sea in transects westward of the Yamal Peninsula, near the St. Anna Trough, in the Ob River estuary (Obskay Guba), and on the adjacent shelf. Concentration of chlorophyll a in the euphotic layer varied from 0.02 to 4.37 µg/l, aver. 0.76 µg/l. Primary production in the water column varied from 10.9 to 148.0 mg C/m**2/day (aver. 56.9 mg C/m**2/day). It was shown that frontal zones divided the Kara Sea into distinct areas with different productivities. Maximum levels of primary production were measured in the deep part of the Yamal transect (132.4 mg C/m**2/day) and the shallow Kara Sea shelf near the Ob River estuary (74.9 mg C/m**2/day). Characteristics of these regions were low salinity of the surface water layer (19-25 psu) and elevated silicon concentration (12.8-28.1 µg-atom/l). It is explainable by river runoff. Frontal zones of the Yamal current within the Yamal and Ob transects showed high assimilation numbers reached to 2.32 and 1.49 mg C/mg Chl/hr, respectively; they were maximal for studied areas.