Effects of foliar spraying of water hyacinth (Pontederia crassipes) with sodium chloride on the benthic macroinvertebrate community

Abstract

The present study aims to evaluate the indirect effects of foliar spraying of water hyacinth with sodium chloride on the benthic macroinvertebrate community in a pond at the Wetland Research Laboratory of the University of Abomey-Calavi, Benin. The experimental setup included two distinct environments: water under hyacinth (ESJ) subjected to spraying and untreated open water (EL). Samples were collected before and one month after the treatment in each environment, and macroinvertebrates were identified at the lowest possible taxonomic level. Non-parametric Wilcoxon tests were conducted to compare macroinvertebrate abundance before and after spraying at a significance level of 5%. The results showed a decrease in macroinvertebrate diversity in the sprayed water under hyacinth, as well as a taxonomic composition shift with a more pronounced density increase in ESJ after spraying. Despite these changes, the overall taxonomic richness did not show a significant difference between ESJ and EL. In conclusion, this control method led to an overall increase in density for certain taxa but a decrease in taxonomic diversity, particularly of those associated with water hyacinth, which may have implications for the ecological balance of the aquatic ecosystem.

Keywords: Foliar spraying, NaCl, Pontederia crassipes, Benthic macroinvertebrates, Pond