Indicator Species - Indicators of Environmental Condition

Indicators of Environmental Condition

Indicator species are also known as sentinel organisms, i.e. organisms which are ideal for biomonitoring. Organisms such as oysters and mussels have been extensively used as biomonitors in marine and estuarine environments. For example, the 'Mussel Watch' programme is a world-wide project using mussels to assess environmental impacts on coastal waters. Their well-documented feeding habits, stationary condition and their role as integral parts of the food chain are some of the main reasons why oysters and mussels are widely used biomonitors. A considerable amount of contaminant concentrations are found in the surficial sediments (i.e. the finer-grained particulate matter, usually muds, silts or clays) of marine and estuarine environments. A major physical process governing the transport of fine particulate material and associated particle-bound contaminants in estuarine environments is resuspension. Strong winds create surface waves, which, in shallow water (<5m), project energy to the water-sediment interface resulting in resuspension of fine sediment from the upper layers of the estuary floor. Once in suspension, fine material may be transported by tidal currents to other parts of the estuary and possibly to the ocean during multiple reworking phases. Mussels and oysters are filter feeders and therefore uptake is by ingestion of particulates in the water column. Sediment resuspension is thus very important in the bioaccumulation process which aids the evaluation of possible adverse biological effects of sedimentary contaminants in marine and estuarine environments. GR - Legend