Bellona Foundation

Abstract The offshore Multiuse Setting (MUS) is a concept that seeks to co-locate marine industrial activities including wind farms, aquaculture, and tourism. MUS are thought to be an innovative way to promote efficiency in resource use. Despite this contention, plans for MUS are plagued by an implementation gap whereby innovative ideas do not actualise into commercial operations. A suggested barrier to progression of MUS is the lack of understanding surrounding the consequences to economic, societal and environmental dimensions of the system that result from MUS designs and activities. The implementation of a MUS has the traits of a complex decision problem and thus will benefit from decision analysis to structure the decision-making process. Here we show the consequences resulting from implementation of the Multiuse Setting concept against multiple objectives - environmental, social, and economic – through the application of group-based cognitive mapping. The assessment involved the use of a hypothetical case study to introduce system boundaries and explored predictions about the outcomes of implementation using a modified Delphi method approach. The results demonstrate that there are a network of social-ecological changes with both positive and negative (and potentially costly) implications across and within sustainability dimensions. We illustrate how systemic views contradict existing claims about seaweed aquaculture and co-location with wind farms, such as carbon sequestration potential and spatial resource efficiency, considering the complexity of an MUS project. The methodology provides a route to recognise trade-offs and risks from, and provide alternative strategies for, the MUS and wider seaweed aquaculture within the context of the broader industrial strategy of Sustainable and Circular Bioeconomy transition.

Biological traits analysis (BTA) is considered to be a powerful technique for describing the ecological functioning of marine benthic assemblages. This study is the first to apply BTA to assess differences in the traits of benthic faunal assemblages between areas exposed to heavy and light trawling in a major upwelling ecosystem along the west coast of southern Africa. The data were collected from two sampling locations in Namibia and six sampling locations in South Africa. The intensity of trawling varied from area to area. Significant differences in biological traits (BT) were detected between heavily and lightly trawled areas. Weighted infaunal traits showed significant differences between heavily and lightly trawled areas for 17% of the traits investigated, while 24% of epifaunal traits investigated were significantly different between areas of different trawling intensities. This suggests that the measured BTs of the epifauna might be more sensitive to trawling disturbances than BTs of the infauna. The infaunal traits differed significantly between areas with larger or smaller proportions of sand and mud. Nevertheless, more of the significant differences in infaunal BTs were related to variations in trawling intensity than to variations in sediment composition. Significant modifications of BTs are likely to lead to modified functioning of the community and provide more general potential indicators for management than those based on species. The study confirms the need for more basic biological and life history data on macro-benthic invertebrates but nevertheless shows that BTA detected specific features that correlate with trawling intensity and that these features may be important for epifaunal assemblage functioning.