Conclusion

Benthic communities in Area 222 were within the range of community structure observed in other nearby areas. However, after disturbance Area 222 was different to those areas. This is due to the difference in dredging frequency that every area had experienced. Similarly, the sites within Area 222, which were subjected to different dredging intensity, also developed a different community structure. In the present study, all three common traditional measures, namely abundance, biomass and species richness appeared to show that high dredging intensity caused more damage to the environment than the lower intensity did. However, more current and advanced techniques such as rarefaction, diversity indices and Taxonomic Distinctness suggested that the impact caused by both dredging intensities was fairly similar. However, the immediate impact after the dredging ceased might be different.

The present study also showed how different intensities of dredging can lead to different times for the community to recover once the stress is removed. More importantly, the interpretation of recovery periods was related to different biological

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measurements. However, in general, low dredging intensity did not appear to impose great impacts on benthic community (in certain cases it may have favoured the community), while high dredging intensity showed lasting damage. Different findings from various techniques showed how important it is that many biological aspects should be considered in order to assess macrofaunal community structure. However, it is not feasible to always apply multiple measures in every study. Therefore, for the purpose of ecosystem management, the definition of recovery has to be made based on expert opinion on the question of what kind of recovery is required, whether the quantity, biomass or diversity; or all of these criteria and this has to take into account other potential modes of exploitation of the systems (e.g. fisheries, leisure and aquaculture).

Declaration

The results presented in this chapter have formed part of the following publication: Wan Hussin, W.M.R., Cooper, K.M., Barrio Froján, C.R.S., Defew, E.C., Paterson, D.M. 2012. Impacts of physical disturbance on the recovery of a macrofaunal community: A comparative analysis using traditional and novel approaches. Ecological Indicators, 12: 37-45.

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Chapter 4: Assessment of ecosystem function using functional