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Hong, G.H., 1986

Fluxes, dynamics, and chemistry of suspended particulate matter in a southeast Alaskan fjord

Bibliographic Reference

Hong, G.H., 1986, Fluxes, dynamics, and chemistry of suspended particulate matter in a southeast Alaskan fjord: University of Alaska Fairbanks, Ph.D. dissertation, 253 p., illust.


Sedimentation dynamics of suspended particulate matter (SPM) were investigated in the central basin of Boca de Quadra, a southeast Alaskan fjord. The weighted mean fluxes over the June 1982 - October 1983 were 290, 519, 812, 1124 g m-2 yr-1, respectively, determined using sediment traps deployed at 40, 120, 300 and 375 m depth in the 380 m water column. The long-term sedimentation rate was estimated at average 589 g m-2 yr-1 from sediment 210Pb profiles. Substantial SPM input to mid-depths (below 100 m) from the side arms was noted. Thus, the flux measured at 120 m depth was designated as the primary flux of the SPM to the basin. The sediment focusing resulting from the 'V' shaped basin does not appear to be important. Using particulate Al as a tracer, resuspension rate was estimated at some 30 - 80% of the vertical flux below 280 m depth. Based on the SPM dynamics, the non-conservative behavior of particulate biogenic matter, Mn and Fe was investigated using a primary-resuspended-altered flux model. Degradation rates of settling POC, PN and biogenic Si were estimated at about 0.85, 0.11, and 0.57 mol m-2 yr-1, respectively, in the water column, with maxima at the time of the spring phytoplankton bloom. The 'positive alteration' flux of particulate Mn was estimated at 12 - 34 mg m-2 d-1 due to the active recycling of Mn in the benthic regime. Settling fluxes of particulate biogenic matter show strong seasonality due to the precipitation and primary production pattern. The three methods for estimating sources of organic matter (C/N, deltaC, the riverine SPM input and primary productivity) suggest that phytoplankton primary production in situ provides the major portion of settling particulate organic matter (about 70%). Of the 6.6 mol m-2 yr-1 of POC raining at 375 m depth, approximately 67% is recycled to overlying waters mainly via sediment resuspension, and around 30% is incorporated into the sediments. Sediment diagenesis accounts for about 8%, and around 21% is buried below 50 cm in the sediments. The distribution of pore water solute concentrations was apparently affected by nonlocal exchange processes.

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