The effect of water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae), on benthic biodiversity in two impoundments on the New Year's River, South Africa

Abstract

Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae), forms thick mats that affect water resource utilisation, but little is known about its impacts on biodiversity in aquatic ecosystems. The benthic invertebrate community and algal biomass were sampled under water hyacinth mats and in water hyacinth-free water over a 13-month period, using artificial substrates in New Year's Dam, Eastern Cape Province, South Africa. The number of families per substrate (U = 796.5, P < 0.001), number of individuals per substrate (U = 620.5, P < 0.001), Shannon-Weiner Diversity Index (U = 1 038, P < 0.001), Margalef's Richness index (U = 1 136, P < 0.002), Pielou's Evenness Index (U = 1 230, P < 0.001) and chlorophyll a (U = 678, P < 0.01) were all significantly lower under water hyacinth mats than in water hyacinth-free zones. Similarly, multivariate analyses showed more diversity in invertebrate communities in open water than under water hyacinth. Thus, the control of water hyacinth is important, in order to prevent both ecological and economic impacts of biodiversity loss.

Keywords: aquatic weeds, benthic invertebrates, biodiversity impacts

African Journal of Aquatic Science 2006, 31(1): 25–30