The benthic geochemical record of late Holocene carbon flux in the northeast Atlantic

Shimmield, Graham; Brand, Tim; Ritchie, George D.

doi:10.1098/rstb.1995.0064

Cited by 7 publications

(1 citation statement)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the EUMELI-Eutro site, the POC flux was estimated using the oxidant flux at the sedimentwater interface (Rabouille et al 1993). At those stations where both sediment-trap and seafloor oxidant-flux data exist (e.g., the BOFS stations at ϳ33Њ and 48ЊN, and the EQPAC transect), they agree to within 30% (Shimmield et al 1995;Smith et al 1997). Regression analyses were conducted with SigmaStat (1994) and the significance of product-moment correlation coefficients (r) was determined from Rohlf and Sokal (1969).…”

Section: The Data Set and Methodsmentioning

confidence: 99%

What controls the mixed‐layer depth in deep‐sea sediments? The importance of POC flux

Smith

Rabouille

2002

Limnology & Oceanography

View full text Add to dashboard Cite

The depth of biogenic particle mixing, i.e., the mixed-layer depth (L), is fundamental in models of organic-matter recycling and paleoreconstructions for deep-sea sediments. Factors postulated to control L in the oxygenated deep sea include particulate organic carbon (POC) flux, oxygen penetration into the sediment, and a balance between the downward mixing and decay of labile POC. We explore the dependence of L on biogeochemical characteristics by compiling, from 36 sites in three oceans, an internally consistent set of deep-sea estimates of L, POC flux, biogenic mixing intensity (D b ), and POC reactivity. We use excess 210 Pb as a tracer for L and D b to avoid the confounding effects of tracer-dependent mixing. We find that L, estimated from the penetration depth of excess 210 Pb, varies systematically with POC flux, with an asymptotic function explaining 88% of the variance in L. Stepwise multiple regression suggests that the penetration depth of excess 210 Pb (and estimated L) is much more likely to be controlled by POC flux than by (1) the sediment inventory of excess 210 Pb or (2) biogenic mixing intensity (D b ). In addition, L is negatively related to oxygen penetration into the sediment (r ϭ Ϫ0.629) and not significantly related to predictions of L from a recent mixing/POC-decay model. We conclude that in the food-poor deep sea, POC flux substantially controls the size and activities of the sediment-mixing benthos and, in turn, the thickness of the biogenic mixed layer. Thus, in contrast to previous suggestions, average mixed-layer depth is not environmentally invariant but rather responds predictably to ecologically important parameters such as POC flux.The mixing of sediment grains by animal activity (i.e., biogenic particle mixing) profoundly influences the structure and geochemistry of marine sediments. In particular, the recycling and burial of organic carbon, nutrients, and pollutants, as well as the resolution of the stratigraphic record, depend substantially on the rates and depths of biogenic sediment mixing (e.g., Aller 1982;Wheatcroft et al. 1990; Smith et al. 1993).In deep-sea regions characterized by low current velocities, low sedimentation rates, and well-oxygenated bottom water, biogenic mixing is thought to control the movement of particles in near-surface sediments. Under these conditions, biogenic mixing is usually parameterized as eddy diffusion, described by an intensity coefficient D b (units of length 2 time Ϫ1 ) that operates over a sediment depth interval, L, called the mixed-layer depth (e.g., Guinasso and Schink 1975;Boudreau 1998). Based on this formulation, at steady

show abstract

Section: The Data Set and Methodsmentioning

confidence: 99%