Geological and Geochemical Influences on Estuarine Ecosystems

Abstract

The physical structure of an estuary is governed by geological circumstance and shaped by a combination of river flows, tidal characteristics, current speeds and wave action. An over-riding constraint on estuarine biota is the nature of the variable salinity regime, since the capacity for ionic and osmotic regulation varies greatly between species and sets the limits for their distribution. Of equal importance, if the organism is to settle and survive, are the properties of deposits. Superimposed on these primary drivers are numerous other factors that influence estuarine biota, either directly or indirectly. These include light attenuation and oxygenation patterns (natural characteristics), together with an assortment of anthropogenic impacts. The current chapter focuses on the ways in which geological and geochemical features (substrate properties) impinge on estuarine ecosystems, including modifications made as a result of contaminant bioavailability and toxicity. We also consider ways in which biological activity can mobility in estuaries through processes such as bioturbation and biodeposition.