Using a toxicity test with Ruppia maritima (Linnaeus) to assess the effects of Roundup

• The toxic (acute) effect of Roundup on marine monocot Ruppia maritima was examined.
• High concentration caused a significant lethal effect after seven days of exposure to Roundup.
• Roundup causes significant effect on weigh and chlorophyll a content.
• The analysis revealed foliar elongation in the branches exposed to the low concentration.

Glyphosate, the active ingredient in Monsanto’s broad-spectrum herbicide Roundup, consists of one of the most used pesticides worldwide, but its effects on the marine flora are still not well understood. Were examined Roundup toxic effects on Ruppia maritima specimens collected from Jansen Lagoon (São Luís, MA, Brazil) and acclimatized under laboratory conditions. The numbers of new and dead leaves, the root and leaf length, the chlorophyll a content, and the weight of R. maritima branches were determined before and after exposure to different Roundup concentrations for seven days. High concentrations caused a significant lethal effect. In addition, significant changes were observed in the wet and dry weights, the number and length of the leaves, and the chlorophyll a content. Leaf elongation was observed in the branches exposed to low concentrations, and this change was likely activated as a compensatory mechanism. The results indicate that high concentrations of this herbicide may compromise estuarine flora.