Effects of a glyphosate-based herbicide on Fucus virsoides (Fucales, Ochrophyta) photosynthetic efficiency

Highlights: • We tested the effects of glyphosate-based herbicide (GBH) on Fucus virsoides (Ochrophyta). • The photosynthetic efficiency of Fucus was reduced by 95% after 6 days of exposure to GBH. • Fucus showed irreversible damage even with short time of exposure to GBH (1 day). • The use of herbicides on land might drive the reduction of marine macroalgal communities. • Land-sea planning in ecosystem-based management is a priority. Herbicides are increasingly recognised as sources of water pollution. Glyphosate-based herbicides (GBHs) are widely used because of their low cost and high effectiveness. By measuring the photosynthetic efficiency of Fucus virsoides fronds exposed to a GBH (Roundup® Power 2.0), we investigated the effect of a continuous exposure (6 days) and the potential of recovery after a short exposure (24 h). Both experiments were carried out combining GBH with and without nutrient enrichment, simulating a runoff event. A factorial experimental design allowed us to assess the potential of interactions between GBH and nutrients, which are likely to co-occur in coastal areas. Our results show deleterious effects of GBH at low concentration on F. virsoides, independently from the duration of exposure and the presence of nutrients.