TY - JOUR

T1 - In situ microscale variation in distribution and consumption of O2: A case study from adeep ocean margin sediment (Sagami Bay, Japan)

AU - Glud, Ronnie Nøhr

AU - Stahl, Henrik

AU - Berg, Peter

AU - Wenzhöfer, Frank

AU - Oguri, Kazumasa

AU - Kitazato, Hiroshi

N1 - KeyWords Plus: DIFFUSIVE BOUNDARY-LAYER; PORE-WATER EXCHANGE; MARINE-SEDIMENTS; ORGANIC-CARBON; OXYGEN-UPTAKE; AQUATIC SEDIMENTS; SURFACE SEDIMENTS; SEA SEDIMENTS; CENTRAL PART; DYNAMICS

PY - 2009

Y1 - 2009

N2 - A transecting microprofiler documented a pronounced small-scale variation in the benthic O2 concentration at1450-m water depth (Sagami Bay, Japan). Data obtained during a single deployment revealed that within asediment area of 190 cm2 the O2 penetration depth varied from 2.6 mm to 17.8 mm (average; 6.6 6 2.5 mm) andthe diffusive O2 uptake, calculated from the vertical concentration gradient within the diffusive boundary layer,ranged from 0.6 mmol m22 d21 to 3.9 mmol m22 d21 (average; 1.8 6 0.7 mmol m22 d21, n 5 129). However,correction for microtopography and horizontal diffusion increased the average diffusive O2 uptake by a factor of1.26 6 0.06. Detailed 2D calculations on the volume-specific O2 consumption exhibited high variability. The oxiczone was characterized by a mosaic of sediment parcels with markedly different activity levels. Millimeter- tocentimeter-sized ‘‘hot spots’’ with O2 consumption rates up to 10 pmol cm23 s21 were separated by parcels of lowor insignificant O2 consumption. The variation in aerobic activity must reflect an inhomogeneous distribution ofelectron donors and suggests that the turnover of material within the oxic zone to a large extent was confined tohot spots. The in situ benthic O2 uptakes, measured during four cruises, reflected a seasonal signal overlying theobserved small-scale variability. The annual benthic mineralization balanced ,50% of the estimated pelagicproduction. However, the central bay is characterized by a significant downslope sediment transport, and massbalance estimates indicate 90% retention of the total organic material reaching the bottom of the central bay.

AB - A transecting microprofiler documented a pronounced small-scale variation in the benthic O2 concentration at1450-m water depth (Sagami Bay, Japan). Data obtained during a single deployment revealed that within asediment area of 190 cm2 the O2 penetration depth varied from 2.6 mm to 17.8 mm (average; 6.6 6 2.5 mm) andthe diffusive O2 uptake, calculated from the vertical concentration gradient within the diffusive boundary layer,ranged from 0.6 mmol m22 d21 to 3.9 mmol m22 d21 (average; 1.8 6 0.7 mmol m22 d21, n 5 129). However,correction for microtopography and horizontal diffusion increased the average diffusive O2 uptake by a factor of1.26 6 0.06. Detailed 2D calculations on the volume-specific O2 consumption exhibited high variability. The oxiczone was characterized by a mosaic of sediment parcels with markedly different activity levels. Millimeter- tocentimeter-sized ‘‘hot spots’’ with O2 consumption rates up to 10 pmol cm23 s21 were separated by parcels of lowor insignificant O2 consumption. The variation in aerobic activity must reflect an inhomogeneous distribution ofelectron donors and suggests that the turnover of material within the oxic zone to a large extent was confined tohot spots. The in situ benthic O2 uptakes, measured during four cruises, reflected a seasonal signal overlying theobserved small-scale variability. The annual benthic mineralization balanced ,50% of the estimated pelagicproduction. However, the central bay is characterized by a significant downslope sediment transport, and massbalance estimates indicate 90% retention of the total organic material reaching the bottom of the central bay.

M3 - Journal article

VL - 54

SP - 1

EP - 12

JO - Limnology and Oceanography

JF - Limnology and Oceanography

SN - 0024-3590

IS - 1

ER -