How 'water hyacinths' float about quietly and trap plastics

What is it about?

Water Hyacinths are well known as floating patches of nuisance that snuff out the life from freshwater bodies. But studies have shown that hyacinths can absorb large amounts of certain pollutants as well, such as heavy metals. This study explored the ability of water hyacinths to accumulate plastics in the Saigon river of Vietnam. Using naked-eye visual observation, a specific counting technique for plastics, and unmanned aerial vehicle (UAV) observation, an international group of researchers conducted a 6-week monitoring campaign to determine the ratio and composition of plastics accumulated at water hyacinth patches in the river and those floating freely downstream. They found a strong overlap between the locations of the patches and spatial distribution of the plastics. In fact, 78% of the total plastic transported along the river were carried by water hyacinths. Most of these trapped plastics were large and hard; the softer and more flexible plastics were free-floating.

Featured Image

Photo by Naja Bertolt Jensen on Unsplash

Photo by Naja Bertolt Jensen on Unsplash

Why is it important?

Rivers are a major source of marine plastics. Measures to eliminate riverine plastics from entering the sea require comprehensive information on their modes of transport and accumulation through the river. This study shows that water hyacinth patches floating down the river are major transporters of large plastics while those in slow waters near riverbanks could be barriers to these plastics. Therefore, the findings of this study could better inform local river cleaning programmes. Further, considering water hyacinths populate rivers worldwide, such studies could provide greater insight into freshwater plastic transport, accumulation, and composition variations globally. KEY TAKEAWAY: Floating vegetation patches, such as water hyacinths, are major carriers or barriers of plastics in freshwater systems and could be key locations for water cleanup.