A research-led initiative in southern England is testing floating wetland systems as a means of restoring degraded coastal environments, including the introduction of a rarely trialled floating saltmarsh in a marine setting.
The project is being delivered by the University of Portsmouth in partnership with Southern Water, and aims to reintroduce habitat into heavily engineered coastal zones where natural ecosystems have been displaced by infrastructure such as seawalls and flood defences.
Floating wetlands in engineered coastal settings
Specially designed floating pontoons have been developed to support saltmarsh vegetation directly on coastal waters. These structures are intended to replicate ecological functions typically provided by intertidal habitats, which have been extensively lost in urbanised shorelines.
The approach focuses on reinstating “green” habitat in locations where conventional restoration is not feasible due to physical constraints. By creating vegetated platforms above the water surface, the system is designed to support a range of marine and intertidal species while operating within modified coastal environments.
Dr Ian Hendy, from the Institute of Marine Sciences, is leading the research. He said: “This is an exciting step forward in how we think about restoring coastal ecosystems. By creating a floating saltmarsh, we are reintroducing habitat into spaces where it has been completely lost to development. These systems can provide refuge for marine species, improve water quality and help rebuild biodiversity in some of our most impacted coastal areas.”
Addressing long-term habitat loss
The project responds to extensive declines in coastal vegetation, with researchers indicating that more than 85 per cent of aquatic and marine plant habitats, including saltmarsh, seagrass and kelp, have been lost over the past five decades.
Floating saltmarsh systems have been trialled only a limited number of times globally, with this project representing one of the few attempts to establish marine vegetation on floating infrastructure at scale. A range of saltmarsh species will be cultivated on the platforms to assess their viability and ecological performance under these conditions.
The intention is to restore key ecosystem functions, including nursery habitat for fish, feeding grounds for invertebrates, and support for wider biodiversity in areas that currently lack natural substrates.
Monitoring ecological and water quality outcomes
The installation has been deployed at Southcoast Wake Park in Portsmouth as part of a long-term experimental programme. Researchers are applying a before-and-after monitoring framework to evaluate environmental changes associated with the wetlands.
Assessment will include water quality parameters, biodiversity indicators and measures of ecosystem resilience. The programme incorporates environmental DNA (eDNA) analysis to track changes across a wide range of organisms, from microbial communities to fish and invertebrates.
This approach also allows identification of the sources of bacterial contamination, including distinguishing between human, avian and livestock inputs, which is relevant to managing shellfish waters and bathing water quality.
Nature-based solution for urban coastal pressures
The floating wetlands are designed to function as a nature-based solution addressing multiple pressures linked to coastal urbanisation. These include nutrient enrichment from surface runoff and impacts associated with storm overflows.
By absorbing nutrients and pollutants, the systems are expected to contribute to water quality improvements while also supporting biodiversity net gain, including potential benefits for pollinators using emergent vegetation.
Joff Edevane, environment and water quality lead at Southern Water, said: “This is a wonderful opportunity to pilot a floating wetlands approach to improving water quality and providing Natural Capital. The vision is to use this nature-based solution in protected areas in the future.”
Potential for wider deployment
If the trial demonstrates measurable environmental benefits, the technology could be extended to other locations across the UK in both marine and freshwater contexts. The partners indicate that the approach may offer a scalable method for addressing habitat loss and water quality challenges in constrained environments.
The work contributes to broader efforts to expand the use of nature-based solutions in coastal management, with implications for biodiversity restoration, climate resilience and the protection of ecosystem services. Coastal ecosystems are estimated to provide substantial economic value to the UK, reinforcing the case for investment in restoration approaches that can operate alongside existing infrastructure.
