Marine habitat restoration for future resilience: biogenic reef restoration in sea loughs under a changing climate.

Understanding the optimal approach for seascape-level restoration, where targeted habitats, e.g. biogenic reefs, are restored to support biodiversity and associated ecosystem functioning and stability, is vital for the resilience of the marine ecosystems in general. Such efforts need to include ‘future-proofing’ to both climate change and invasive non-native species. This project will explore the importance of biogenic habitat restoration, targeting shellfish (bivalve) reef and seagrass bed restoration and the interlinkages between these two habitat types with a focus on blue carbon.

Healthy and diverse marine and coastal habitats are recognised as crucial in society’s adaptation to and mitigation of climate change. In a policy context, a range of marine and coastal habitats are recognised for their specific roles in carbon sequestration, coastal protection and in the maintenance and improvement of water quality – often termed “Nature-Based Solutions”. Many coastal habitats are currently in a degraded state, or their areal extent has been reduced due to human activity. There is a global emphasis on the urgent need for restoration, both active and passive, particularly for intertidal and shallow subtidal habitats, yet evidence of appropriate management interventions is lacking. This project will develop an innovative approach reflecting a step-change from traditional conservation approaches.

In order for restoration efforts to be effective an understanding of the wider ecosystem function of specific habitats and their inter-dependencies is required, accounting for local context dependencies. This requires a ‘seascape-scale’ approach to restoration, whereby habitat mosaics are restored at appropriate scales so that interventions cascade across habitat types in a positive way, providing mutually beneficial effects on component species across habitat types. Within Northern Ireland’s sea loughs, both shellfish reefs and seagrass beds co-occur, along with the increasing prevalence of the invasive non-native species, Magallana gigas (the Pacific oyster). This project will focus on establishing local baseline knowledge on the current status of bivalve reef-forming communities in terms of their densities and associated biodiversity (epifauna and infauna). The project will improve knowledge of factors that may limit their restoration (e.g. sedimentation rates, physical disturbance, invasive non-native species) in order to recommend how restoration can be designed to overcome these issues (factors that might also contribute to their role as blue carbon sinks). Where possible, shellfish restoration/reef design will specifically consider co-benefits for local seagrass ecosystems and their restoration.

The project will utilise existing data and involve the collection of new data through both intertidal and subtidal surveys, employing a variety of sampling techniques. This will include remote sensing to support analysis of reef and seagrass bed extent, as well as direct sampling and surveying for structure and function assessment. A mixture of approaches will be used to examine fine-scale physical conditions that are relevant to restoration. The use of community ecology analyses as well as possible modelling approaches to consider future resilience (against a backdrop of climate change – sea temperature and ocean acidification) will be core to achieving the project aims. There will also be opportunities to work with other restoration practitioners to support ecological baseline and reference condition understanding.