Diversity of macrophytes in relation to environmental conditions in wetlands along the lower part of the Gilgel Abay River catchment in Ethiopia

Abstract

The environmental conditions in wetlands affect the diversity, composition, and distribution of their macrophyte communities. This study investigated the diversity of macrophytes as related to environmental conditions in wetlands of the lower part of Gilgel Abay River catchment in Ethiopia. The study was conducted between September 2017 and March 2018, during wet and dry seasons using a quantitative quadrat method. Six wetlands, two surrounded by agriculture, two in an urban setting, and two reference sites, were selected, and categorised from most to least impaired. Twenty-seven macrophyte species were recorded from the six wetlands. Macrophyte diversity and density were significantly higher at the least impaired sites. The densities of Floscopa glomerata, Ceratophylum muricatum, Hygrophila asteracanthoides, Hydrocotyle ranunculoides and Echinochloa species were positively associated with ammonium and biological oxygen demand, whereas those of Salix subserrata, Persicaria attenuata, P. strigosa, P. glabra, Cyperus papyrus, C. fischerianus, C. macrostachyos, Ipomoea aquatica and Ludwigia abyssinica were positively associated with depth and salinity, and negatively correlated with nitrate, phosphate, total dissolved solids and electrical conductivity. Generally, the results of macrophyte diversity, composition, and density indicate poor ecological conditions of the wetlands, particularly those adjacent to agricultural and urban areas.