Water hyacinths retain river plastics.

Area of Science:

• Environmental Science
• Ecology
• Hydrology

Background:

• Rivers are major pathways for plastic pollution reaching the ocean.
• Tropical rivers face dual threats of plastic pollution and invasive water hyacinths.
• Water hyacinths form dense surface patches that can trap floating debris.

Purpose of the Study:

• To investigate the interaction between water hyacinths and plastic debris in rivers.
• To quantify the amount of plastic trapped by water hyacinth patches.
• To understand how plastic transport properties change when aggregated with water hyacinths.

Main Methods:

• Field observations and measurements conducted at a site on the Saigon River, Vietnam.
• Quantification of surface plastic trapped within water hyacinth patches.
• Comparison of the length scale of plastics in open water versus within plant patches.

Main Results:

• Water hyacinth patches trapped 54%-77% of observed surface plastics.
• A strong temporal and spatial co-occurrence of plastic and water hyacinth presence was observed.
• The length scale of trapped plastics (∼4.0 m) was significantly larger than that of open water plastics (∼0.1 m).

Conclusions:

• Plastic-plant aggregates formed by water hyacinths have significant implications for riverine plastic transport.
• These aggregates are detectable from space and necessitate integrated removal efforts.
• The increased length scale of trapped plastics requires further research into transport dynamics, buoyancy, and mass.