Macrophyte Species Composition, Distribution and Diversity in Relation to Some Environmental Factors in Upper Awash River, Ethiopia’
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Date
2020-10-15
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Addis Ababa University
Abstract
Macrophytes play an important role in providing a stable habitat structure to the aquatic ecosystems. Recently Awash River has experienced some undesirable ecological changes due to invasion by exotic weed, Eichhornia crassipes (water hyacinth).With a view come up with scientific information usable in the protection of aquatic resources, this study was carried out between October2019 to April 2020 to assess macrophyte species composition and diversity in upper Awash River in relation to selected environmental factors. Macrophytes were collected manually and physicochemical parameters were measured in situ using YSI 556 multi probe system. Selected nutrients (SRP, TP, TN and Nitrate) were analyzed using standard methods of water and sediment.
In Awash River, a total of Twenty six macrophyte species belonging to fifteen families were identified with relatively low species diversity (H’ = 2.56, Margalef index = 2.91). The emergent macrophytes had the highest percentage composition (92 %) and attained the highest relative frequency and density, followed by free floating (4%) and rooted floating (4%). Results of CCA indicated that Nitrate, SRP, TP and flow velocity were among the factors that had significant impact on the diversity, composition and distribution of the macrophytes in the river. Environmental factors of Awash River were recorded to relate to macrophyte distribution, with emphasis on Eichhornia crassipes density along the river bank. The coverage of Cyperus articulatus L., Echinochloa colona L., Solanum incanum L., Eichhornia crassipes, Persicaria senegalensis, Rorripa nasturtium aquaticum, Ipomoea aquatica and Phragmites mauritianus were almost restricted to sites where there was higher Nitrate, SRP and TP and Ludwigia spp., Sida schimperiana, Alternanthera sessilis, Lagarosiphon cordofanus Casp, Brachiaria mutica, Juncus effuses, Ludwigia abyssinica, Cyperus latifolius, and Cyperus papyrus to sites where there was higher DO,TN and Silt.
In conclusion, the in situ and experimental data obtained indicate that 50% of the macrophytes diversity was determined by the environmental factors like total nitrogen and phosphorus, flow velocity, nitrate (water) and sediment texture and half of the unexplained environmental factors that regulate the macrophyte diversity and distribution in the Awash basin have to be investigated in future studies.
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Awash River, Canonical Correspondence Analysis, Flow Velocity, Macrophyte, Principal Component Analysis, Water Hyacinth