Resuspension processes and seston dynamics, southern North Sea

Jago, C. F.; Bale, A.J.; Green, M. O.; Howarth, M.J.; Jones, Sarah E.; McCave, I. N.; Millward, G.E.; Morris, A.W.; Rowden, Ashley A.; Williams, Jon J.

doi:10.1007/978-94-011-1236-9_8

Cited by 42 publications

(43 citation statements)

References 15 publications

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“…Superimposed on this pattern, a different quarter-diurnal pattern occurred, related to resuspension and sedimentation of phytopigments. These patterns are in accordance with other observations in the North Sea (Jago et al 1994). The increase in phytopigments on 14 July (Day 194) in the SML and the thermocline (25 m depth) coincided with/was preceded by a slight increase in PO,.…”

Section: Water Column Phytopigment Variability Over Time and Depthsupporting

confidence: 92%

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Short-term variability in pelagic-benthic exchange of phytopigments and their relations to benthic bacterial variables in the North Sea

Duyl¹,

Duineveld²,

Kop³

1997

Aquat. Microb. Ecol.

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The short-term variability in pelagic-benthic exchange of phytopigments and the response of benthic bacteria to changes in phytopigment input in the bottom were studied in a temperature stratified water column including the sediment surface layer in the Oyster Grounds, North Sea, from 5 to 19 July 1994. The exchange of inorganic nutrients and phytopigments across the thermocline was limited during the cruise, with exception of a single short-lasting event on 14 July. This event resulted in enhancement of pigments throughout the water column and affected the pigment content in the surface mixed layer (SML) more and longer than in the benthic mixed layer (BML). The event did not result in a measurable change of sedimentation in the BML. The temporal variability of phytopigments in the SML was not reflected in the BML, where variations in phytopigments were determined by variations in tidal advection, sedimentation and resuspension. Variations in phytopigment fluxes to the bottom were demonstrated, with pigment sedimentation during slack tide exceeding sedimentation during full tide. The bulk of the phytodetrital material which settled during slack tide was resuspended during full tide. Nevertheless, there was net sedimentation of phytopigments, but insufficient to compensate for the decrease of the pigments in the sediment. The benthic phytopigment inventory gradually decreased during the cruise. Spatial variations in benthic phytopigments were significantly reflected by the spatial variations in bacterial variables, however the temporal decrease in algal pigments in the sediment was not reflected by the temporal variations in the benthic bacterial variables. Spatial relations between primary phytopigments and benthic bacterial production were decoupled in time implying that chlorophyll a and fucoxanthin are poor indicators of the amount of bacterial substrate in the absence of fresh algal input (directly utilizable organic matter). The spatial relations between benthic bacterial variables and benthic phytopigments however indicate that the dominant source of food for bacteria in the Oyster Grounds is phytodetritus.

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Section: Water Column Phytopigment Variability Over Time and Depthsupporting

confidence: 92%

“…Wave action and (tidal) currents may diminish settlement rates and can induce resuspension of particles from the bottom influencing the concentrations of phytodetritus in the water column (e.g. Jago et al 1994). Lateral deposition fluxes have been reported to exceed vertical particle fluxes to the bottom (Graf 1992, Thomsen et al 1995.…”

Section: Introductionmentioning

confidence: 99%

Short-term variability in pelagic-benthic exchange of phytopigments and their relations to benthic bacterial variables in the North Sea

Duyl¹,

Duineveld²,

Kop³

1997

Aquat. Microb. Ecol.

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“…The permeability of sediments in this area derived from grain size and porosity (Chilingar 1964) ranges from 20 (Stn 13) to 150 darcy (Stn 4 ) , whereas bottom friction velocities ranged between 1 and 7 cm S-' depending on location and tidal phase (Jago et al 1994, Pohlmann & Puls 1994. The bottom water flow was also investigated by underwater video images, which revealed a maximum speed of suspended particles just above the seafloor between 5 to 20 cm S-' (L. Lohse pers.…”

Section: Discussionmentioning

confidence: 96%

Oxygen pore water profiles in continental shelf sediments of the North Sea:turbulent versus molecular diffusion

Lohse¹,

Epping²,

Helder³

et al. 1996

Mar. Ecol. Prog. Ser.

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Oxygen pore water profiles in North Sea s e d~m e n t s were measured with microelectrodes during 2 contrasting seasons. The measurements were conducted In a wide variety of sediments, including non-depositional areas on the southern shelf as well as depositional areas in the Skagerrak.All measurements were performed within minutes on board at In sltll temperature. The curvature of oxygen profiles in sandy sediments on the southern shelf Indicated the presence of a surface layer characterised by enhanced diffusion. The occurrence of enhanced diffusion was related to sedimentological and seasonal differences. Quantitative evaluat~on of the pore water profiles by a diffusion-reaction model indicated that the effective diffusion coeff~c~ents In a 0.2 to 16 mm subsurface layer were 1.5 to > l 0 0 times higher than the ~nolecular diffusion coefflcient. Highest effective diffusion coefficients were reported for non-depositional sediments characterised by low diffusive oxygen fluxes. Oxygen profiles in sediments of the depositional area of the Skagerrak indicated constant diffusivity throughout the sediment column. Diffusive fluxes cdlculated from profiles ranged from 5.2 to 8.9 ~nlnol m-2 d-' in August 1991, and were between 0.8 and 6.2 mm01 nl ' d-' in February 1992. Seasonal differences in sediments locatt!d In the Skagerrak area were minor. It is proposed that near-bottom tidal currents induce enhanced diffus~on transport processes in the upper millimetres of the sandy sediments of the southern North Sea, while less energetic hydrodynamical conditions in the depos~tional area of the Skagerrak favour sediment-water exchange based on molecular diffusion only. Biogeochemical implications of the enhanced diffusivity close to the sediment-water interface are discussed.

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“…This region is a relatively shallow area ͑10 -40-m water depth͒ where strong semidiurnal tides with current amplitude of ϳ1 ms Ϫ1 combine with frequent strong winds to cause relatively high concentrations of suspended particulate matter ͑SPM͒ ͑e.g., 1-200 g m Ϫ3 ͒ by means of resuspension of bottom sediments. 38 Regarding the optical properties of the region, there is strong absorption in the blue from CDOM that is thought to be of terrestrial origin, e.g., a CDOM absorption coefficient at 400 nm of 0.1-2 m…”

Section: A Seawifs Imagery Of Belgian Coastal Watersmentioning

confidence: 99%

Atmospheric correction of SeaWiFS imagery for turbid coastal and inland waters

Ruddick¹,

Ovidio²,

Rijkeboer³

2000

Appl. Opt.

516

287

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The standard SeaWiFS atmospheric correction algorithm, designed for open ocean water, has been extended for use over turbid coastal and inland waters. Failure of the standard algorithm over turbid waters can be attributed to invalid assumptions of zero water-leaving radiance for the near-infrared bands at 765 and 865 nm. In the present study these assumptions are replaced by the assumptions of spatial homogeneity of the 765:865-nm ratios for aerosol reflectance and for water-leaving reflectance. These two ratios are imposed as calibration parameters after inspection of the Rayleigh-corrected reflectance scatterplot. The performance of the new algorithm is demonstrated for imagery of Belgian coastal waters and yields physically realistic water-leaving radiance spectra. A preliminary comparison with in situ radiance spectra for the Dutch Lake Markermeer shows significant improvement over the standard atmospheric correction algorithm. An analysis is made of the sensitivity of results to the choice of calibration parameters, and perspectives for application of the method to other sensors are briefly discussed.

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Resuspension processes and seston dynamics, southern North Sea

Cited by 42 publications

References 15 publications

Short-term variability in pelagic-benthic exchange of phytopigments and their relations to benthic bacterial variables in the North Sea

Short-term variability in pelagic-benthic exchange of phytopigments and their relations to benthic bacterial variables in the North Sea

Oxygen pore water profiles in continental shelf sediments of the North Sea:turbulent versus molecular diffusion

Atmospheric correction of SeaWiFS imagery for turbid coastal and inland waters

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