A model study on the large-scale effect of macrofauna on the suspended sediment concentration in a shallow shelf sea

Nasermoaddeli, Mohammad Hassan; Lemmen, Carsten; Stigge, G.; Kerimoglu, Onur; Burchard, Hans; Klingbeil, Knut; Hofmeister, Richard; Kreus, Markus; Wirtz, Kai W.; Kösters, Frank

doi:10.1016/j.ecss.2017.11.002

Cited by 17 publications

(22 citation statements)

References 64 publications

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“…Numerous other works (e.g. Lee et al 2013;Nasermoaddeli et al 2018;Ye et al 2018) have shown that it is possible to apply a 3D model to shallow systems and as such future work could consider application of a 3D model to Christchurch Harbour to see if better understanding of circulation patterns could be gained. In addition, future work will consider coupling a biogeochemical model to the hydrodynamic model to identify regions of reduced oxygen concentration.…”

Section: Flushing Timementioning

confidence: 99%

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

Huggett

Purdie

Haigh

2020

Estuaries and Coasts

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Simple flushing time calculations for estuarine systems can be used as proxies for eutrophication susceptibility. However, more complex methods are required to better understand entire systems. Understanding of the hydrodynamics driving circulation and flushing times in small, eutrophic, temperate estuaries is less advanced than larger counterparts due to lack of data and difficulties in accurately modelling small-scale systems. This paper uses the microtidal Christchurch Harbour estuary in Southern UK as a case study to elucidate the physical controls on eutrophication susceptibility in small shallow basins. A depth-averaged hydrodynamic model has been configured of the estuary to investigate the physical processes driving circulation with particular emphasis on understanding the impact of riverine inputs to this system. Results indicate circulation control changes from tidally to fluvially driven as riverine inputs increase. Flushing times, calculated using a particle tracking method, indicate that the system can take as long as 132 h to flush when river flow is low, or as short as 12 h when riverine input is exceptionally high. When total river flow into the estuary is less than 30 m 3 s −1 , tidal flux is the dominant hydrodynamic control, which results in high flushing times during neap tides. Conversely, when riverine input is greater than 30 m 3 s −1 , the dominant hydrodynamic control is fluvial flux, and flushing times during spring tides are longer than at neaps. The methodology presented here shows that modelling at small spatial scales is possible but highlights the importance of particle tracking methods to determine flushing time variability across a system.

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Section: Flushing Timementioning

confidence: 99%

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

Huggett

Purdie

Haigh

2020

Estuaries and Coasts

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“…Nevertheless, bioturbators generally make the sediment less resistant to erosion by loosening it with their activities (Willows, et al, 1998;Ciutat, et al, 2007;Montserrat, et al, 2008;Volkenborn, et al, 2009;van Prooijen, et al, 2011;Rakotomalala, et al, 2015;Cozzoli, et al, 2018a;Joensuu, et al, 2018). The effect of bioturbators on cohesive sediment resuspension impacts the short-and long-term development of coastal morphology (Le Hir, et al, 2007;Orvain, et al, 2012;Winterwerp, et al, 2018), and should hence be taken into account when forecasting the evolution of landscapes and ecosystems Orvain, 2005;Orvain, et al, 2012;Bouma, et al, 2014;Queirós, et al, 2015;Nasermoaddeli, et al, 2018). Beyond coastal morphology, sediment resuspension is related to the oxygenation and the transfer of particles and nutrients within the sediment layers and from the sediment surface to the water column (Ubertini, et al, 2012).…”

Section: Accepted Manuscript Introductionmentioning

confidence: 99%

A process based model of cohesive sediment resuspension under bioturbators' influence

Cozzoli

Gjoni

Pasqua

et al. 2019

Science of The Total Environment

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Macrozoobenthos may affect sediment stability and erodibility via their bioturbating activities, thereby impacting both the short-and long-term development of coastal morphology. Process-based models accounting for the effect of bioturbation are needed for the modelling of erosion dynamics. With this work, we explore whether the fundamental allometric principles of metabolic activity scaling with individual and population size may provide a framework to derive general patterns of bioturbation effect on cohesive sediment resuspension. Experimental flumes were used to test this scaling approach across different species of marine, soft-sediment bioturbators. The collected dataset encompasses a range of bioturbators functional diversity, individual densities, body sizes and overall population metabolic rates. Measurements were collected on a range of hydrodynamic stress from 0.02 to 0.25 Pa. Overall, we observed that bioturbators are able to slightly reduce the sediment resuspension at low hydrodynamic stress, whereas they noticeably enhance it at higher levels of stress. Along the whole hydrodynamic stress gradient, the quantitative effect of bioturbators on sediment resuspension can be efficiently described by the overall metabolic rate of the bioturbating benthic communities, with significant variations across the bioturbators' taxonomic and functional diversity. One of the tested species (the gallery-builder Polychaeta Hediste diversicolor) had an effect that was partially deviating from the general trend, being able to markedly reduce sediment resuspension at low hydrodynamic stress compared to other species. By combining this trend with hydrodynamic forces, we were able to produce a process-based model of biota-mediated sediment resuspension.

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“…For the discretization of advection, we employed a third-order, totalvariation-diminishing P2-PDM (i.e., ULTIMATE QUICK-EST) scheme, recognized for its accuracy and gradientconserving qualities (e.g., Pietrzak, 1998;Burchard and Rennau, 2008). An almost identical model setup was previously employed and shown to capture the spatial and temporal distributions of temperature and salinity within the German Bight for the period 2000-2010 (Kerimoglu et al, 2017a), as well as the tidal dynamics (Nasermoaddeli et al, 2018). Since then, the following refinements have been made: (i) providing meteorological forcing at an hourly resolution extracted from a COSMO-CLM hindcast simulation (Geyer, 2014), which was previously at a 6 h resolution; (ii) specifying the monthly average vertical temperature and salinity profiles at the boundaries for each year separately as predicted by HAMSOM (for a recent description of the setup, see Große et al, 2017), instead of providing climatological averages for all years; (iii) explicitly describing horizontal diffusion through a Smagorinsky parameterization (Smagorinsky, 1963).…”

Section: The Modelmentioning

confidence: 99%

“…Such models are rare (but see, e.g., Baird et al, 2016;Lessin et al, 2019); however, this is expected to change with improving data availability and computational capacities (Lessin et al, 2018). An intermediate step might be to use statistically estimated distributions of benthic organisms for various scenarios (e.g., Singer et al, 2017) as external forcing in biogeochemical models (see, e.g., Nasermoaddeli et al, 2018).…”

Section: Model Limitations and Perspectivesmentioning

confidence: 99%

Interactive impacts of meteorological and hydrological conditions on the physical and biogeochemical structure of a coastal system

et al. 2020

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Abstract. The German Bight was exposed to record high riverine discharges in June 2013, as a result of flooding of the Elbe and Weser rivers. Several anomalous observations suggested that the hydrodynamical and biogeochemical states of the system were impacted by this event. In this study, we developed a biogeochemical model and coupled it with a previously introduced high-resolution hydrodynamical model of the southern North Sea in order to better characterize these impacts and gain insight into the underlying processes. Performance of the model was assessed using an extensive set of in situ measurements for the period 2011–2014. We first improved the realism of the hydrodynamic model with regard to the representation of cross-shore gradients, mainly through inclusion of flow-dependent horizontal mixing. Among other characteristic features of the system, the coupled model system can reproduce the low salinities, high nutrient concentrations and low oxygen concentrations in the bottom layers observed within the German Bight following the flood event. Through a scenario analysis, we examined the sensitivity of the patterns observed during July 2013 to the hydrological and meteorological forcing in isolation. Within the region of freshwater influence (ROFI) of the Elbe–Weser rivers, the flood event clearly dominated the changes in salinity and nutrient concentrations, as expected. However, our findings point to the relevance of the peculiarities in the meteorological conditions in 2013 as well: a combination of low wind speeds, warm air temperatures and cold bottom-water temperatures resulted in a strong thermal stratification in the outer regions and limited vertical nutrient transport to the surface layers. Within the central region, the thermal and haline dynamics interactively resulted in an intense density stratification. This intense stratification, in turn, led to enhanced primary production within the central region enriched by nutrients due to the flood but led to reduction within the nutrient-limited outer region, and it caused a widespread oxygen depletion in bottom waters. Our results further point to the enhancement of the current velocities at the surface as a result of haline stratification and to intensification of the thermohaline estuarine-like circulation in the Wadden Sea, both driven by the flood event.

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A model study on the large-scale effect of macrofauna on the suspended sediment concentration in a shallow shelf sea

Cited by 17 publications

References 64 publications

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

A process based model of cohesive sediment resuspension under bioturbators' influence

Interactive impacts of meteorological and hydrological conditions on the physical and biogeochemical structure of a coastal system

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