New floating wetlands project targets dramatic loss of coastal ecosystems  

A new project is set to transform degraded coastal environments through the installation of pioneering floating wetlands - including a rarely trialled floating saltmarsh system in a marine setting. 

The project, led by the University of Portsmouth in partnership with Southern Water, will see specially designed floating pontoons, engineered to support saltmarsh vegetation, deployed in coastal waters.  Their purpose will be to recreate crucial lost “green” habitats in areas dominated by concrete infrastructure such as seawalls and flood defences. 

Researchers say the approach offers a practical, scalable solution to the widespread loss of essential coastal ecosystems, with more than 85 per cent of aquatic and marine vegetation, including saltmarsh, seagrass and kelp, lost over the past 50 years. 

The floating wetlands will host a diverse range of saltmarsh plants, with marine species being trialled on a floating system - which has only been trialled six times previously. By effectively creating a floating saltmarsh, the project aims to provide vital habitat for fish and marine life, enhance biodiversity, and restore valuable ecosystem functions to heavily modified coastal environments. 

Dr Ian Hendy, from the Institute of Marine Sciences at the University of Portsmouth, is leading the project. 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.” 

The wetlands have been set up at the Southcoast Wake Park in Portsmouth as part of a long-term research programme, using a before-and-after monitoring approach to assess their environmental impact. Scientists will track changes in water quality, biodiversity and ecosystem resilience over time. 

As a nature-based solution, the floating wetlands are designed to deliver multiple environmental benefits. These include improving water quality by absorbing nutrients and pollutants, supporting biodiversity net gain for both aquatic species and terrestrial pollinators, and contributing to carbon capture. 

The project will also explore how these systems can help mitigate the effects of urbanisation, including nutrient pollution from runoff and impact from storm overflows. 

The initiative builds on the University of Portsmouth’s expertise in constructed wetlands for water remediation and habitat restoration. Using environmental DNA (eDNA) sequencing, researchers will monitor changes in biodiversity, from bacteria and fungi to fish and invertebrates, providing detailed insights into how ecosystems respond to the installation of the wetlands. eDNA work will also allow the origin of bacteriological communities to be identified; for example, human, avian or livestock, which is an important part of Southern Water’s approach to protect shellfish and improve bathing water quality. 
 
Dr Hendy added: “This collaboration demonstrates how innovation and partnership can help tackle some of the most pressing environmental challenges. Floating wetlands offer a promising, nature-based solution to improving water quality and enhancing biodiversity in coastal and urban environments.” 

The project aligns with global efforts to scale up nature-based solutions and supports the delivery of the United Nations Sustainable Development Goals, particularly those focused on climate action, clean water and biodiversity. 

With coastal ecosystem services estimated to be worth £211 billion to the UK economy, researchers say restoring these habitats is critical not only for the environment, but also for long-term economic resilience. 

Joff Edevane, Environment & Water Quality Lead for Southern Water, added that if successful, the floating wetland technology could be deployed widely across the UK in both marine and freshwater environments, such as those targeted in the Three Harbours project (Solent Forum - Three Harbours) helping to address the growing challenges of habitat loss, pollution and climate change. 

He 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.”