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Location Impact of Sediment Load on the Littoral Zone (Lacustrine Wetlands and River Mouths) of Lake Tana, Ethiopia

  • Student: Marie Shiferaw Tamrat
  • Institution: Bahir Dar University
  • Degree: M.Sc.
  • Posted on: August 02, 2012

Thesis Abstract

The impact of sediment load on Lake Tana littoral zone was studied at three habitats of littoral and pelagic zones (six sites). Samples of physico-chemical and biota were measured during seasonal intervals. It was covered a period from February, 2009 to January, 2010. Zegie habitat was stable, has macrophyte and wind protected. Gorgora habitat was degraded, no or very patchy macrophyte and muddy. Gumara River mouth habitat was naturally exposed to sedimentation because of upstream inflow of sediment from the degraded catchments. There were spatial and temporal variations of physico-chemical and biota measurements. Plankton diversity of the lake didn’t showed variations. Secchi disc depth range was 0.20m Gorgora littoral- 0.90m Zegie littoral sites and turbidity range was 15NTU Zegie littoral - 67NTU Gorgora littora sites. Turbidity due to sediment load was high at Gorgora and Gumara River mouth littoral sites during August and September. High concentration of silicate was recorded during wet season at Gorgora and Gumara River mouth littoral sites associated to inflow of sediment from the degraded catchments. The concentration of nitrate and soluble reactive phosphate were low. Low and high mean chlorophyll a concentration was recorded at Gorgora littoral site (1.41µg l-1) and Zegie littoral site (4.34µg l-1) respectively. The littoral site of Zegie plankton abundunce was high but low in Gorgora littoral site. One way ANOVA phytoplankton abundance by turbidity (P= .007), zooplankton abundance by turbidity (P< .001) and chlorophyll a concentration by turbidity (P< .001), i.e. turbidity significantly predicted plankton abundance and chlorophyll a concentration. Most Littoral zones (Lacustrine wetlands and river mouths) of Lake Tana were threatening by inflow of sediment load and wind induced resuspension of sediment because macrophyte was degraded and still subjected to severe anthropogenic impacts.