The principle aim of this study is to assess whether mussels and their associated
macrofaunal assemblages can be used in biomonitoring studies of anthropogenic disturbance in an estuarine environment. Field studies were carried out initially, in North Wales and South-West England, that investigated the use of natural populations of mussels and their associated assemblages to monitor for differences in anthropogenic disturbance both within and between
estuaries and the effects of temporal variability of natural environmental and physiological factors on the results of these studies.
Significant correlations were found between mussel-patch assemblage structure and both mussel density and the amount and type of accumulated sediment in the patches, a relationship linked to increased habitat complexity. The results of various immunocompetence assays and measures of mussel condition highlighted the problems associated with field studies of biomarker
responses using native animals due to the complex and fluctuating nature of the environment and genetic or physiological adaptation of native animals to sub-lethal, chronic pollution. Significant temporal variation was observed between mussels (in terms of immunology and condition) and their associated macrofaunal assemblages at the scales of weeks and months. This temporal
variability means that reliance on single sample collections may result in erroneous interpretations of assemblage-based metrics of environmental quality.
Manipulative experiments using artificially constructed mussel patches and caged, transplanted mussels, were employed to try and unconfound some of the effects of natural variability in biotic and abiotic factors on the measures of mussel health and assemblage composition. A study done in Sydney Harbour, Australia indicated that experimental mussel patches might provide a simple, low cost means of studying macrobenthic colonisation or recruitment in a range of locations without the confounding effects caused by differences in mussel patch composition. An experiment to test the theory that the problems associated with using native animals in biomarker studies can be addressed by using mussels transplanted from a single clean site to the locations that need to be monitored, revealed that the natural variability within each location was greater than any differences between them. This highlighted the need to
include within location replication in order to ensure effects are being assessed at the correct spatial scale and to avoid pseudoreplication.
In conclusion, mussel immunological biomarkers and the structure of their associated macrofaunal assemblages can be effective biomonitors of anthropogenic disturbance providing the natural variability in these measures is either controlled for using manipulative experiments or is integrated into monitoring programmes at a series of nested spatial and temporal scales. The
main advantage of using these communities rather than the more commonly used benthic soft-sediment invertebrate assemblages lies in the opportunity it gives to run mussel health assays alongside the assemblage tests, allowing the effects of a disturbance to be assessed at a range of closely related scales of biological organisation.