Restoration of underwater forests

Seaweeds are major habitat-forming organisms that support diverse communities and underpin a wide range of ecosystem functions and services in temperate coastlines around the world. Key species of seaweeds are, however,... [ view full abstract ]

Seaweeds are major habitat-forming organisms that support diverse communities and underpin a wide range of ecosystem functions and services in temperate coastlines around the world. Key species of seaweeds are, however, declining and while conservation in a preventative sense is a partial solution to the challenge of habitat degradation, the status of many of the world’s ecosystems clearly demonstrates that it is not sufficient by itself. The fucoid seaweed Phyllospora comosa forms extensive beds that provide habitat and other resources, supporting diverse assemblages, including economically important species. Phyllospora was once common on shallow subtidal reefs around Sydney, but disappeared in the 1980’s, coincident with peaks in heavy sewage outfall discharges. Comparisons of biodiversity associated with this alga and other key habitat-forming algae demonstrated that Phyllospora is not functionally redundant and thus motivated the need for restoration of this species. Transplanted Phyllospora onto Sydney’s reefs generally survive, grow and reproduce similarly to those in reference populations. In some ‘restored’ locations, these populations are beginning to self-sustain. Because the ultimate goal is not only to restore Phyllospora but also the biodiversity it supports, we have been quantifying several components of associated biodiversity in replicate ‘restored’, reference and control (non-restored) locations several times before and after the restoration efforts. Preliminary results on some of these components (e.g. epifauna) suggest that restoring associated biodiversity can be a complex and long-term process. Our research also shows that improving environmental conditions does not necessarily lead to the recovery of lost species. In the context of “green engineering” in urbanized coastlines, this suggests that clever engineering may need to be coupled with active restoration of key (habitat-forming) species to successfully recover degraded systems.