Assessing ecological functioning in marine benthic communities

Abstract

With the advent of an ecosystem approach to marine management, the importance of developing methods to investigate ecological functioning is receiving increasing attention. This thesis develops a novel approach for describing ecological functioning in marine benthic systems. Biological traits analysis (BTA) uses a suite of life history, morphology and behaviour characteristics of species to describe aspects of their functioning. Comparison of BTA with two other approaches proposed for describing functioning in marine ecosystems established that BTA identified a range of biological attributes important for differentiating benthic communities and was better able to describe spatial patterns in assemblage composition than the other measures. Appraisal of the analytical tools proposed for use in BTA revealed they provided similar views of assemblage functioning, with the nonparametric tool being appropriate for providing a general picture of functioning, while the more complex parametric tools had greater power to detect anthropogenic impacts. Evaluation of the type and number of traits included in BTA showed it was sensitive to the number of traits selected for analysis, with optimal results being gained by maximising trait number. Examination of the relationship between functioning and environmental variability revealed that trait composition was related to changes in a number of environmental factors, although this relationship was complex and the nature of associations between traits and specific environmental factors varied depending on the location of assemblages. Further analyses focussed on the impacts of anthropogenic activities on benthic assemblage functioning. These revealed that assemblage functioning was impacted by fishing disturbance in both subtidal and intertidal assemblages. A number of traits were impacted by fishing, including some associated with vulnerability to physical stress and others related to resistance to disturbance, while other aspects of functioning remained unaffected. The thesis has increased our understanding of biological traits analysis as a tool for describing functioning in marine benthic systems. It has also contributed to some interesting ecological and management issues, such as the relationship between species and functioning and the importance of, information required for, and strategies available for conservation of ecological functioning in marine ecosystems.