Shallow Water Habitats

Physical Characteristics: Hydrodynamic Setting

Waves, tides and current move and mix estuarine and coastal waters and bottom sediments.  The hydrodynamic setting affects the nature of water exchange and the often determines the type of sediment that will be found in a particular location.

Open water areas that are exposed to the effects of  waves, tides, and currents tend to have more water exchange, less chance of hypoxia or anoxia and coarse (sandy) sediments.  Because they are exposed to greater tidal flushing and wave exposure, there is less potential for direct impacts of pollutants in surface runoff and groundwater.
Protected areas such as small tidal creeks, coves and lagoons have low exposure to waves and may even have diminished tides.  As a result, they tend to have less water exchange and fine (muddy) sediments. Because these areas also tend to be in close proximity to potential sources of pollutants in surface runoff and groundwater base flow and because fine sediments tend to retain more pollutants than coarse sediments, protected areas have high potential for direct impacts from pollutants.

For further information about hydrodynamic processes in estuarine and coastal marine habitats refer to the following:

Mann, K. H. 2000. Ecology of coastal waters, with implications for management.  Blackwell Publishing; Chapter 2.3 – Physical structure and functioning of estuaries

OzCoast and OzEstuaries website:
http://www.ozcoasts.org.au/conceptual_mods/index.jsp

http://www.ozcoasts.org.au/conceptual_mods/ about_sed_env.jsp