JWARP  Vol.4 No.10 , October 2012
Seasonality in Abundance, Biomass and Production of the Phytoplankton of Welala and Shesher Wetlands, Lake Tana Sub-Basin (Ethiopia)
ABSTRACT
The species composition and production of the phytoplankton community of the Shesher and Welala floodplain Wetlands, on the eastern side of Lake Tana, were studied during four seasons from July 2009 to May 2010. We investigated the spatial and temporal dynamics of phytoplankton, densities, biomass, in relation to physico-chemical conditions. Gross and net primary production was studied at one site in each Wetland. Temperature, dissolved oxygen, conductivity, Secchi-disc depth, nitrate, phosphate and silicate concentrations showed significant temporal variation (p < 0.05), whereas none of these parameters showed significant spatial variation (p > 0.05). Thirty six phytoplankton genera/species, belonging to 7 higher taxa were identified. The Chlorophyta dominated the phytoplankton community and contributed 42% - 53 % of the total observed phytoplankton numbers. Average phytoplankton biomass (chlorophyll a content) over four seasons ranged from 9 - 121 μg.l-1 in Shesher and from 27 - 206 μg.l-1 in Welala, whereas the average gross primary production over three seasons was 10.5 in Shesher and 7.7 mg.O2l-1d-1 in Welala. The peak concentration of chlorophyll a was observed in the pre-rainy season, which coincided with a bloom of Microcystis spp. Both Shesher and Welala Wetlands are very productive and have a good water quality but they are threatened by low water inputs since in the summer of 2009 the construction of a dam by local people and facilitated by local officials prevented overflow from Ribb River into the Wetlands. We conclude that the good water quality, the relative high water temperature and high primary productivity make the two Wetlands suitable for culture based fisheries and/or aquaculture, but a wise water resource management is crucially important.

Cite this paper
T. Wondmagegne, A. Wondie, M. Mingist and J. ijverberg, "Seasonality in Abundance, Biomass and Production of the Phytoplankton of Welala and Shesher Wetlands, Lake Tana Sub-Basin (Ethiopia)," Journal of Water Resource and Protection, Vol. 4 No. 10, 2012, pp. 877-884. doi: 10.4236/jwarp.2012.410103.
References
[1]   M. C. Calijuri, A. C. A. Dos Santos and S. Jati, “Temporal Changes in the Phytoplankton Community Structure in a Tropical and Eutrophic Reservoir (Barra Bonita, S.P. Brazil),” Journal of Plankton Research, Vol. 24, 2002, pp. 617-634. doi:10.1093/plankt/24.7.617

[2]   C. S. Reynolds, “Temporal Scales of Variability in Pelagic Environments and the Response of Phytoplankton,” Freshwater Biology, Vol. 23, 1990, pp. 25-53. doi:10.1111/j.1365-2427.1990.tb00252.x

[3]   W. D. Taylor, E. Kebede and Z. Gebre-Mariam, “Primary and Secondary Production in the Pelagic Zone of Ethiopian Rift Valley Lakes,” In: C. Tudorancea and W. D. Taylor, Eds., Ethiopian Rift Valley Lakes, Backhuys Publishers, Leiden, 2002, pp. 95-108.

[4]   LFDP-Lake Fisheries Development Project, “Phase II. Final Report,” Ministry of Agriculture, Addis Ababa, 1998, pp. 16-20.

[5]   J. F. Talling and J. Lemoalle, “Ecological Dynamics of Tropical Inland Waters,” Cambridge University Press, Cambridge, 1998.

[6]   N. Atnafu, E. Dejen and J. Vijverberg, “Assessment of the Ecological Status and Threats of Welala and Shesher Wetlands, Lake Tana Sub-Basin (Ethiopia),” Journal of Water Resource and Protection, Vol. 3, No. 3, 2011, pp. 540-547. doi:10.4236/jwarp.2011.37064

[7]   A. Getahun, E. Dejen and W. Anteneh, “Fishery Studies of Ribb River, Lake Tana Basin, Ethiopia,” Ethiopian Nile Irrigation and Drainage Project Coordination Office, Ministry of Water Resources, Final Report E1573, Vol. 2, Addis Ababa, 2008.

[8]   T. Alemayehu, M. McCartney and S. Kebede, “The Wa- ter Resource Implications of Planned Development in the Lake Tana Catchment, Ethiopia,” Ecohydrology and Hydro- biology, Vol. 10, No. 2-4, 2010, pp. 211-222. doi:10.2478/v10104-011-0023-6

[9]   N. Atnafu, “Assessment of Ecological and Socio-Economic Importance of Fogera Floodplains: The Case of Welala and Shesher Wetlands,” MSc. Thesis, Bahir Dar University, Bahir Dar, 2010.

[10]   W. Anteneh, E. Dejen and A. Getahun, “Shesher and Welala Floodplain Wetlands (Lake Tana, Ethiopia): Are They Important Breeding Habitats for Clarias gariepinus and the Migratory Labeobarbus Fish Species?” The Scientific World Journal, Vol. 2012, 2012, Article ID: 298742.

[11]   B. Kibret, “In Situ Characterization of Local Chicken Eco-Type for Functional Traits and Production System in Fogera Woreda, Amhara Regional State,” MSc. Thesis, Haramaya University, Haramaya, 2008.

[12]   R. G. Wetzel and G. E. Likens, “Limnological Analysis,” 3rd Edition, Springer, NewDelhi, 2001.

[13]   G. W. Prescott, “Algae of the Western Lakes Area,” Re- vised Edition, WMC Brown Company Publishers, Dubuque, 1962.

[14]   A. Wondie, S. Mengistu, J. Vijverberg and E. Dejen, “Seasonal Variation in Primary Production of a Large High Altitude Tropical Lake (Lake Tana, Ethiopia): Effects of Nutrient Availability and Water Transparency,” Aquatic Ecology, Vol. 41, No. 2, 2007, pp. 195-207. doi:10.1007/s10452-007-9080-8

[15]   SPSS for Windows, “Statistical Package for Social Science (SPSS),” Release 13.0, The Apasche Software Foundation, 2007.

[16]   US Environmental Protection Agency (USEPA), “The Quality of Our Nation’s Water: A Summary of the 1988 National Water Quality Invent

[17]   ory,” EPA Report 440/4- 90-005, Washington DC, 1990.

[18]   A. Wondie, “Dynamics of the Major Phytoplankton and Zooplankton Communities and Its Role in the Food Web of Lake Tana, Ethiopia,” Ph.D Thesis, Addis Ababa University, Addis Ababa, 2006.

[19]   S. M. Ramadhan, “Limnological Studies of Floodplain Lakes Ruwe and Uba, Rufiji River, Tanzania,” Institute for Water Education UNESCO-IHE, Delft, 2003.

[20]   H. B. O. Lungayia, L. Sitoki and M. Kenyanya, “The Nutrient Enrichment of Lake Victoria (Kenya Waters),” Hydrobiologia, Vol. 458, 2001, pp. 75-82. doi:10.1023/A:1013128027773

[21]   Z. Dessalegn, “Temporal Dynamics of Biomass and Primary Production of Phytoplankton in Relation to Some Phsico-Chemical Factors in Lake Koriftu, Ethiopia,” MSc. Thesis, Addis Ababa University, Addis Ababa, 2007.

 
 
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