Seagrass wrack on beaches traps harmful plastics

A new scientific study has found that natural accumulations of dead seagrass act as traps for plastic debris, including harmful microplastics, before they reach the sea.

The experts behind the study are calling for more sustainable beach cleaning practices, warning that the removal of Posidonia oceanica wrack is ecologically disruptive.

A natural plastic filter

Posidonia oceanica is a protected Mediterranean species recognised for its vital ecosystem services, including producing oxygen, absorbing carbon dioxide, and providing habitats for marine life. At the end of its life cycle, its leaves detach and accumulate on beaches, forming dense piles known as banquettes or wrack.

The study examined three Maltese beaches—Qalet Marku, Xemxija, and Ramla tal-Qortin—and identified 1,913 plastic items embedded within these seagrass deposits. Xemxija, a site characterised by heavy human activity from nearby restaurants, bars, and busy roads, recorded the highest concentration, averaging 102.42 items per square metre.

Mesoplastics (5–25 mm) were the most common type of debris, making up nearly half of all items, with fragments being the dominant shape. This suggests much of the pollution originates from the breakdown of larger plastics. Researchers confirmed that wrack functions as a natural barrier, intercepting debris from both land-based and marine sources.

Rethinking beach cleaning

In Malta, beach management has traditionally involved the removal of seagrass wrack to create “cleaner” shorelines for tourism. The Tourism Authority grooms over 50 coastal sites and removes around 19,000 tonnes of waste annually, a figure that includes seagrass deposits.

The researchers strongly advise against this approach, describing it as ecologically damaging. Wrack deposits play a critical role in stabilising sand dunes, protecting coastlines from erosion, dampening wave energy, and supplying nutrients to dune vegetation. Mechanical removal can strip sand, degrade habitats, and generate additional greenhouse gas emissions.

Beyond these ecological services, the study highlights the role of wrack as an “effective mechanism” for intercepting plastic waste. By trapping plastics onshore, wrack prevents them from dispersing back into the sea, where they could contribute to growing levels of microplastic pollution. If managed carefully, these natural deposits concentrate plastic debris in limited areas, potentially simplifying clean-up efforts without harming ecosystems.

Towards “bio-beaches”

The authors stress that current waste management strategies require urgent revision to reflect the ecological value of seagrass wrack. They recommend shifting from one-off beach cleaning towards continuous, sustainable maintenance. Rather than removing deposits, wrack could be promoted as part of the natural landscape, encouraging a model of “bio-beaches” that balances tourism with ecological protection.

Such an approach would depend on greater awareness among local councils, managers, and beach users about the importance of wrack habitats. Suggested alternatives include seasonal burial or selective displacement of smaller deposits, coupled with educational initiatives to reframe wrack not as waste but as a vital coastal resource.

The research team

The study, titled Posidonia Oceanica Wrack Intercepts Plastic Debris: First Evaluated Evidence On Maltese Beaches, was conducted by a collaborative team of scientists. Contributors include Tosin Afeniforo from Scuola Universitaria Superiore IUSS Pavia, Claudio D’Iglio, Nunziacarla Spanò, and Serena Savoca from the University of Messina, Joseph A. Borg from the University of Malta, and Irina Litvinenko from the University of Milano-Bicocca.

Their work provides the first quantitative evidence of plastic debris trapped within Posidonia oceanica deposits on Maltese beaches, underscoring the ecological importance of these natural formations in tackling plastic pollution. The study was published in the journal: Regional Studies in Marine Science.