Near‐bed turbulence and hydrodynamic control of diffusional mass transfer at the sea floor

Dade, W. Brian

doi:10.4319/lo.1993.38.1.0052

Cited by 136 publications

(101 citation statements)

References 55 publications

(51 reference statements)

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“…Such cases of runoff produce unpredictable pulses in the terrestrial inputs of both inorganic and organic particulate and dissolved nutrients , Lucea et al 2005. On the other hand, wind-driven turbulence and waves may promote sediment resuspension (Ferré et al 2005) and/or increase the flux of dissolved nutrients from the sediment (Dade 1993). For example, the NW Mediterranean littoral is periodically assailed by severe easterly storms ('llevantades'), which, because of a long fetch, are accompanied by relatively long waves.…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Lueck & Reid 1984), particularly in the Mediterranean Sea, where tides are comparatively unimportant (Hopkins 1985). As such, winddriven turbulence may be expected to have an important impact on the coastal osmotrophic plankton, either by increasing sediment resuspension and/or nutrient diffusivities from the sediment (Dade 1993) or by accelerating relevant processes at small scales (e.g. Peters & Marrasé 2000).…”

Section: Types Of Episodic Forcingmentioning

confidence: 99%

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Episodic meteorological and nutrient-load events as drivers of coastal planktonic ecosystem dynamics: a time-series analysis

Guadayol¹,

Peters²,

Marrasé³

et al. 2009

Mar. Ecol. Prog. Ser.

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In temperate coastal zones, episodic meteorological forcing can have a strong impact on the classical seasonal phytoplankton succession. Episodes of continental runoff and wind storms involve nutrient enrichment and turbulence, 2 factors that can promote primary production and alter the planktonic community species composition and size structure. We determined the joint influence of these 2 variables on the osmotrophic plankton of an oligotrophic NW Mediterranean open bay. We used an 8 yr long time series of monthly physical, chemical and biological water-column parameters, and we looked for correlations between these and several meteorological and physical highfrequency time series through cross-correlation analyses. Influence of river runoff in this particular location was found to be very important for phytoplankton dynamics, whereas no immediate response of bacterioplankton was detected. Resuspension events caused by waves had a secondary importance. Cross correlations allowed defining a sequence of responses to these types of forcing, from changes in water turbidity and salinity, to increases in phytoplankton and bacteria abundances through nutrient enrichments. The maximum response of the ecosystem in terms of chlorophyll a concentration lagged nutrient enrichment events by about 1 wk. A more detailed analysis was performed between June 2003 and June 2004, a period characterised by an intense drought in summer and by 6 strong meteorological events afterwards. The increase in the frequency of meteorological events during this period drove the system from heterotrophy to autotrophy. Our data stress the importance of episodic meteorological events in coastal planktonic communities. KEY WORDS: Episodic meteorological forcing · Coastal osmotrophic plankton · Waves · Terrestrial runoff · Sediment resuspension · Nutrients · Time series · NW Mediterranean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 381: [139][140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155] 2009 3 different environments, and thus are subjected to the variability in continental, atmospheric and oceanic forcing. In particular, Mediterranean littoral systems offer a good template to study how such episodic types of forcing may alter the dynamics of the osmotrophic plankton away from the typical seasonal pattern, for 2 reasons. First, because the Mediterranean Sea is generally oligotrophic, and thus signals of allochthonous inputs may be more easily detected. Second, because one of the main characteristics of the Mediterranean climate is the irregularity of its temporal pattern of precipitation and storms (e.g. Cebrián et al. 1996).Episodes of rainfall and wind storms are both likely to cause an input of allochthonous material into the Mediterranean coastal zone. On the one hand, sporadic heavy rainfall events often result in catastrophic terrestrial runoff, a general characteristic of the Mediterranean climate (e.g. Cebrián et al. 1996). Such cases of runo...

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Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

Section: Types Of Episodic Forcingmentioning

confidence: 99%

Episodic meteorological and nutrient-load events as drivers of coastal planktonic ecosystem dynamics: a time-series analysis

Guadayol¹,

Peters²,

Marrasé³

et al. 2009

Mar. Ecol. Prog. Ser.

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“…Unlike other radioactivity transport models [2,11], the exchange rate W pw ð0;1Þ (mass transfer coefficient [7]) is estimated by boundary layer theory [34] and corrected for surface roughness [10] as…”

Section: The Equations Of Radionuclide Transportmentioning

confidence: 99%

Migration of radioactivity in multi-fraction sediments

et al. 2017

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A new 3D radioactivity transport model coupled with multiscale circulation and multi-fractional sediment transport modules is presented. The sediment transport module simulates the transport of a mixture of one cohesive sediment fraction and a number of fractions of non-cohesive sediments of different sizes and densities. The model of radionuclide transport describes the key transport and exchange processes in the system of water-suspended and bottom multi-fraction sediments. Two-step kinetics with two successive reversible fast and slow reactions is used in the model. A noticeable feature of the model is approximation of the sediment and contamination profiles in the bed by multiple well-mixed layers to describe the vertical migration of radioactivity within bottom sediments due to erosion/deposition, molecular diffusion and bioturbation. The model accurately reproduced a laboratory experiment on the uptake of radiocesium by lake sediments. An analytical solution describing mutual adjustment of the concentrations of radioactivity in the pore water and in the multi-fraction sediment showed that activity was redistributed between different fractions of sediments far slower than between water and the total concentration in the sediment. The extended one-layer model of bottom contamination of multi-fraction sediments was derived from a general model and compared with a multilayer model. It was found, however, that the one-layer approximation was not capable of correctly predicting the inventory due to the fact that one-layer averaged concentration can essentially differ from the near-surface value in the multi-layer model. Radionuclide 123Environ Fluid Mech (2017) 17:1207-1231 DOI 10.1007 transport in channel with bottom depression was simulated to estimate the effects of erosion/deposition and the multi-fractionality of sediments on the transport process. It was shown that these factors affect the distribution of sediments by forming local maxima and minima of activity at the beginning and end of the depression, respectively, due to the redistribution of contaminated bottom sediments by flow. The developed model can also be used to simulate the transport of a wide class of toxic substances sorbed on sediments.

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“…Mass transfer from the overlying flowing water to the surface of a flat sediment bed has been studied using the concept of the diffusive boundary layer (Fig. 1) (Rahm & Svensson, 1989;Dade, 1993;Nakamura & Stefan, 1994). The existence and significance of the diffusive boundary layer above the sediment-water interface has been demonstrated in numerous experimental studies (Belanger, 1981;Jørgensen & Revsbech, 1985;Whittemore, 1986;Jørgensen & DesMarais, 1990;Mackenthun & Stefan, 1998;Josiam & Stefan, 1999;Steinberger & Hondzo, 1999;Røy et al 2002;House, 2003).…”

Section: Introductionmentioning

confidence: 99%

Oxygen transfer from flowing water to microbes in an organic sediment bed

et al. 2008

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Mass transfer of dissolved oxygen (DO) across a sediment-water interface was investigated using laboratory experiments and a numerical simulation model. DO concentration profiles and velocity profiles were measured with high resolution in a recirculating flume with water flowing at crosssectional average velocities from 3.5 to 11.5 cm/s over a flat and hydrodynamically smooth organic sediment bed. Parameters extracted from the measurements included (1) the DO penetration depth, (2) the effective diffusion coefficient in the sediment layer, (3) the thickness of the turbulent diffusive boundary layer, and (4) the diffusion coefficients in the diffusive boundary layer. DO penetration depths were less than 1 mm, and diffusive boundary layer thicknesses were less than 8 mm. Diffusion in the sediment porewater system was shown to be essentially molecular. The laboratory data were compared to results from a deterministic simulation model. The model included explicit descriptions of (1) mass transfer through the diffusive boundary layer above the sediment/water interface, (2) the boundary layer development over the sediment bed of finite length, (3) diffusive transfer in the sediment porewater system, and (4) microbial uptake of DO in the sediment. The model included both water-side and sediment-side mass transport limitations. The control of DO flux could alternate between water-side and sediment-side without discontinuity. Monod-type kinetics was adopted for DO uptake in the sediment. Organic substrate availability in the sediment did not vary over the course of an experiment. A kinetic limitation for organic matter (substrate) was not considered, and microbial activity in the sediment was parameterized by biomass density. Measured and simulated DO concentration profiles showed satisfactory agreement, with some discrepancies at the interface caused by roughness and porosity effects of the sediment surface.

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Near‐bed turbulence and hydrodynamic control of diffusional mass transfer at the sea floor

Cited by 136 publications

References 55 publications

Episodic meteorological and nutrient-load events as drivers of coastal planktonic ecosystem dynamics: a time-series analysis

Episodic meteorological and nutrient-load events as drivers of coastal planktonic ecosystem dynamics: a time-series analysis

Migration of radioactivity in multi-fraction sediments

Oxygen transfer from flowing water to microbes in an organic sediment bed

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