Common weed killer harms underwater plants at surprisingly low doses
de Moura-Silva IA, Bueno SB, Borella J
Phytoremediation
The ponds and slow streams near your home may look clear and healthy while the submerged plants that oxygenate the water and shelter fish are quietly dying off from herbicide runoff that never touches the surface plants you can actually see.
Scientists combined nearly 80 years of research on how a widely used weed killer called 2,4-D affects water plants, and found something surprising: plants that grow fully underwater, like Eurasian watermilfoil, are far more sensitive than floating plants like duckweed or water hyacinth. Some underwater plants started showing damage at herbicide levels far below what regulators currently consider safe, which means the rules protecting our lakes and streams might need a second look. On the bright side, duckweed and a floating fern called Salvinia turned out to be good at soaking up and removing the chemical from water, hinting at a natural cleanup method.
Key Findings
Submerged Eurasian watermilfoil (Myriophyllum spicatum) showed high sensitivity to 2,4-D, with EC50 values as low as 0.04-0.182 mg/L causing growth inhibition.
Floating species like duckweed (Lemna minor) and water hyacinth (Pontederia crassipes) were far more tolerant, needing 7.08 to over 100 mg/L and 8.1 mg/L respectively to show similar effects.
Duckweed and water fern (Salvinia natans) showed the strongest potential for phytoremediation, while water hyacinth was less effective at removing 2,4-D from water.
chevron_right Technical Summary
A review of 86 studies spanning nearly 80 years finds that the common weed killer 2,4-D can harm underwater plants at doses far lower than what floating plants can tolerate, suggesting current water safety limits may not protect sensitive pond and lake vegetation.
Abstract Preview
Original paper
Ecotoxicological responses of aquatic macrophytes to 2,4-D: A global synthesis of species sensitivity and ecological risk.
The widespread use of 2,4-dichlorophenoxyacetic acid (2,4-D) has raised concern about its persistence, mobility, and effects on non-target aquatic vegetation in freshwater ecosystems. Here, we prov...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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Myriophyllum spicatum is a submerged perennial aquatic plant which grows in still or slow-moving water. Eurasian watermilfoil is native to Europe, Asia, and North Africa, but has a wide geographic and climatic distribution among some 57 countries, extending from northern Canada to South Africa. I...