Abstract
Increased herbicide use in agriculture is a major threat to adjacent aquatic and wetland ecosystems. In Morocco, the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) poses a risk to temporary ponds found in agricultural landscapes. This study used mesocosm experiments to assess the effects of 2,4-D concentration (0, 0.10, 0.20, and 0.30 mg·L−1) and application timing (early vs. late in the hydrological cycle) on water quality and aquatic plant communities from forest ponds not previously exposed to herbicides. At the highest concentration (0.30 mg·L−1), conductivity increased from 206 to 274 µS and pH from 7.5 to 8.4 under early application. At the same time, species richness and total abundance significantly decreased with increasing 2,4-D concentrations, with the strongest effects observed under early application. Community composition shifted markedly in response to 2,4-D, with annual and submerged species showing greater sensitivity, whereas perennial and emergent species were relatively tolerant. These findings highlight the need to adopt more sustainable agricultural practices to conserve pond biodiversity. Specifically, herbicide applications should be avoided near ponds, at high application rates, and during periods early in the hydroperiod. Lastly, land-use strategies should balance agricultural productivity with the conservation of biodiversity in temporary pond ecosystems.