This downward flow makes possible the deep aeration of sediment and the transport of fine particles deep into the seabed. An equal volume of water leaves the sediment as compensation for the downward flow.

In effect, each surface sediment layer is washed twice in a cycle, unless this flow washes the sides of the bank. A particle movement model through a permeable sediment was described by Huettel et al. (1996) and Rush et al. (2006). Besides the hydraulic selleck inhibitor pressure of waves, the second mechanism that may be responsible for circulation in the porous layer in Svalbardbanken involves tidal currents and bottom Ekman layer formation. Tidal forcing was modelled by Kowalik & Proshutinsky (1995), who found residual currents of 8 cm s− 1 over Spitsbergenbanken. The model by Massel et al., 2004 and Massel et al., 2005 was constructed for a uniform, geostrophic flow in a homogeneous fluid over a flat porous bottom. An additional effect may be sea bed roughness, which increases turbulent mixing; according to Reidenbach et al. (2010), a cobble bed increases mixing and downstream transport 7.5

times compared to a smooth surface. Other models of water flux forced by gravity waves were produced by King et al. (2009); they show a ca 0.3 m deep penetration of water into the sediment, which is consistent find more with the data obtained for fine coastal sands in the Baltic Sea (Massel et al. 2004). In view of measured and modelled spring and summer concentrations of microplankton biomass (0.05 g ww m− 3 – Piwosz et al. 2009) and a flow rate into the sediment of between 8160 and 15 912 m3 m− 2 day− 1 (Table 2), it is estimated that during 10 days of stormy weather as much as 4 to 8 kg of pelagic biomass wet weight passes through each m2 of Svalbardbanken sediment (Table 2). The figures suggest that the site under examination is an extremely active filter system, important for recycling nutrients and sustaining regional primary production rates.

A similar Cobimetinib mw role of permeable shallows was postulated for temperate shelf environments (Huettel et al., 1996 and Ehrenhauss et al., 2004). A number of studies on the mineralization of organic matter in permeable sediments have been performed in coastal and very shallow waters (Huettel et al. 1996, Rush et al. 2003, 2006): all of them indicate that the intensity of organic matter metabolism depends on the intensity of oxygen flow through porous media. Apart from building up the biomass of interstitial organisms, organic carbon processing in the sediments provides the surrounding waters with regenerated nutrients (Huettel et al. 1996). Flow through the permeable sediment in the offshore banks of the Gulf of Mexico is an important source of nutrients and bioavailable iron for the whole region (Gibbes et al. 2008). There are three main pathways along which organic matter can be oxidized in the sediment – abiotic, microbial, and indirectly through meiofauna (Opaliński et al. 2010).