Fluid Flow in Continental Margin Sediments

Abstract

The transfer of solutes and gases across the sediment-water interface through fluid flow at vents and seeps are complementing the inputs of nutrients, methane and xenobiotics through riverine and atmospheric input and diffusive fluxes from the seafloor to the water column of the continental margin. Fluid advection through sediments provide an efficient mechanism for the upward transport of reactive components and trace gases like methane and carbon dioxide, otherwise remineralised or precipitated within the sediment without impact on the chemistry of the ocean or the biota at the seafloor. Studies on submarine groundwater discharge and fluid venting along accretionay ridges emphasise the importance of fluid flow for hydrological budgets, biogeochemical cycles, and physical properties of sediments. Offshore plankton blooms, methane and trace element plumes, and release of large amounts of fresh water reveal the ecological and economic significance of submarine fluid discharge in the coastal zone. Along accretionary ridges, vent sites are characterised by the unique consortium of benthic organisms, formations of massive authigenic carbonates, methane plumes, and occurrences of gas hydrate. These features are associated with fluid flow in sediments. Techniques and tracers for localisation of discharge sites and quantification of discharge rates are introduced. The similarities between these two environmental settings characterised by fluid flow are considered and potential needs for future studies are discussed.