The Barents Sea seasonal ice zone (SIZ) is one of the most dynamic areas in the world ocean. This biologically productive area undergoes extreme intra- and inter-annual variabilities in sea ice and water mass transport properties. Here, we investigate seafloor burial processes in three regions of the SIZ with different ice-cover frequencies: predominantly open water (POW), marginally ice-covered (MIC), and predominantly ice-covered (PIC) with approximately 0, 10 and 50% sea ice cover, respectively, in 2002-2003. Down-core sediment profiles of the radionuclides Th-234, Pb-210, and Cs-137 along with sediment carbon, nitrogen and phosphorus concentrations are examined in two to three cores from each region. Sedimentation rates and velocities using Pb-210(ex) (excess Pb-210) profiles and assuming negligible mixing below a surface mixed layer are relatively uniform throughout the study area, averaging 558 +/- 154 g m(-2) y(-1) and 1.1 +/- 0.4 mm y(-1) (n=7). These sedimentation velocities are confirmed using Cs-137 (1.0 +/- 0.4 mm y(-1), n = 7). Th-234(ex) (excess Th-234) derived bioturbation rates are positively correlated with number of benthic individuals per 0.5 m(2) (R-2 = 0.83) and exhibit a pattern of higher rates in the MIC (14.5 +/- 2.1 cm(-2) y(-1)) relative to both the POW (6.3 +/- 2.2 cm(-2) y(-1)) and PIC (5.3 +/- 1.2 cm(-2) y(-1)) (p < 0.01). Th-234(ex) inventories are also significantly higher (p = 0.026) within the MIC, while both Pb-210(ex) and Cs-137 sediment inventories are more regionally uniform. Furthermore, organic carbon (C-org) and total nitrogen (N-tot) concentrations are relatively high in both the MIC and PIC compared to POW. For this limited data set, higher bioturbation rate coefficients and higher Th-234(ex) sediment inventories in the MIC relative to the other sampled regions, suggest that the MIC exhibits a greater predominance of marine versus terrestrial sediment sources that support enhanced scavenging and benthic biological activity. These results suggest that a climate-driven northward shift in sea ice will result in a corresponding shift in benthic communities that currently depend upon surface derived fluxes of organic matter associated with the present-day location of the ice edge in the Barents Sea. (C) 2009 Elsevier B.V. All rights reserved.
