A Study on Phytoplankton Species Composition, and Primary Production in Fincha Reservoir, West Shoa Zone, Ethiopia

摘要

Fincha reservoir is a man-made freshwater body in Ethiopia constructed in 1973 in the course of Chomen swamp for power generation, irrigation and fishing. This reservoir is one of those water bodies which have not received attention in spite of its flourishing commercial fisheries. The phytoplankton species composition, biomass and primary productivity of this reservoir was carried out during the non rainy season for a period of six months. The samples were taken from two selected sites, s1 located near the shore where human interference in the form of washing clothes, cattle and fishing is high and S 2 an open area at the middle of the reservoir (less impacted area). The water in the shallow study site showed high level of total nitrogen, nitrate and total phosphorus than the deeper zone. The Three classes such as green algae, blue green algae and diatom were the major taxonomic group identified. The chlorophyceae comprising 39 species constituted 25-54% of the total plankton. The blue green algae such as Cylindrospermopsis africana and Microcystis sp.?and dinoflagellates, Peridinium gutanense , were important in terms of abundance. The phytoplankton biomass measured as chlorophyll a pigment varied from 13.9 to 22.2 and from 12.3 to 23.7 mg/m 3 at near-shore and central stations?respectively. A maximum gross primary production value (567 mg/cm 3 /h) and the minimum (146 mg/cm 3 /h) were recorded at 0.25 m and 1m depth in the near-shore station.