Long-term Trends of Phyto- and Zooplankton Communities of Lake Hawassa, Ethiopia
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Long-term monitoring of plankton composition and productivity can impart information useful for lake management purposes, though such study is sporadically documented in tropical lakes. The phyto- and zooplankton communities of Lake Hawassa (previously also known as Lake Awasa or Awassa), Ethiopia, was studied between November 2003 and August 2004, and it is compared with historical data since the 1980-ies to assess potential interdecadal changes. Lake Hawassa, located in the Ethiopian rift-valley and neighborhood of the growing city of Hawassa, receives effluents from textile and ceramics industry and municipal sewage with little treatment. In 2003/04, phytoplankton abundance comprised 54% Chlorophyta,
26% cyanoprokaryotes, 18% diatoms and 2% others, a proportion similar to previous records. However, the mean phytoplankton biomass (as surrogate Chlorophyll a, 19 µg L-1) was lower than reported from previous studies (e.g. 43 µg L-1). However, areal rate of gross photosynthesis had increased in the last two decades with
higher values recorded at present (0.35 to 2.21 g O2 m-2 h-1). In a similar way, even though zooplankton community composition remained the same, the abundance and dominance of taxa have changed in the last decades with lower abundance of cladocera (2600 ± 640 SE Indl m-3) and high abundance of the small-sized rotifers (264 000 Indl m-3, more than fivefold decadal increase) and cyclopoid nauplii. The adult cyclopoid to nauplii ratio of 0.27 in the present study indicated that cannibalism previously suggested has diminished at present, probably due to high number of rotifers as prey. Plankton data of 2003/4 compared with those of two decades earlier indicated that Lake Hawassa has become eutrophic with higher gross phytoplankton production rate, reduced phytoplankton biomass due to overtake by nanoplanktonic forms and Nitrogen dominance by NH4. Zooplankton composition has shifted to small-sized groups with Rotifer and Nauplii dominance and Cladocera have become reduced. Most plankton parameters indicate that Lake Hawassa is trending towards eutrophication
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Admassu, D. (1996). The breeding season of tilapia, Oreochromis niloticus L. in Lake Hawassa (Ethiopian rift valley). Hydrobiologia, 337(1-3), 77-83.
Ayenew, D. (2004). Environmental implications of changes in the levels of lakes in the Ethiopian Rift since 1970. Reg. Environ. Change, 4(4), 192-204.
Carlson, R.E. (1977). A trophic state index for lakes. Limnol. Oceanogr., 22(2), 361-369.
Central Statistical Agency. (2011). Website Link
Defaye, D. (1988). Contribution à la connaissance des crustaces copepods d’Ethiopie. Hydrobiologia, 164(1), 103-147.
Dodds, W.K. (2006). Freshwater Ecology: Concepts and Environmental Applications. Academic Press.
Fernando, C.H. (1994). Zooplankton, fish, and fisheries in tropical Freshwaters. Hydrobiologia, 272, 105-123.
Fernando, C.H. (2002). A Guide to Tropical Freshwater Zooplankton. Identification, Ecology and Impact on Fisheries. Backhuys Publishers, Leiden, The Netherlands.
Fetahi, T. (2005). Trophic analysis of Lake Hawassa (Ethiopia) using mass-balance Ecopath model. MSc Thesis, Addis Ababa University, Ethiopia.
Fetahi, T., & Mengistou, S. (2007). Trophic analysis of Lake Hawassa (Ethiopia) using mass balance Ecopath model. Ecological Modelling, 201, 398-408.
Froese, R., & Pauly, D. (Eds.). (2011). FishBase. World Wide Web electronic publication. Website Link
Gamachu, D. (1977). Aspects of climate and water budget in Ethiopia. Addis Ababa University Press, Addis Ababa, Ethiopia.
Gebre-Mariam, Z. (1988). Dynamics of Heterotrophic bacterioplankton in an Ethiopian Rift-Valley lake (Hawassa). PhD dissertation. University of Waterloo.
Gebre-Mariam, Z., Kebede, E., & Desta, Z. (2002). Long-term changes in chemical features of waters of seven Ethiopian rift-valley lakes. Hydrobiologia, 477, 81-91.
Gilbert, J.J., & Stemberger, R.S. (1985). The costs and benefits of gigantism in polymorphic species of the rotifer Asplanchna. Archiv für Hydrobiologie, 21, 185-192.
Hindak, F. (2000). Morphological variation of four planktonic nostocalean cyanophytes – members of the genus Aphanizomenon or Anabaena? Hydrobiologia, 438, 107-116.
Jeeji-bai, N., Hegewald, E., & Soeder, C.J. (1997). Revision and taxonomy analysis of the genus Anabaenopsis. Algological Studies, 18, 3-24.
John, D.M., Whitton, B.A., & Brook, A.J. (2002). The freshwater algal flora of the British Isles: An identification guide to freshwater and terrestrial algae. Cambridge University Press.
Kebede, E., & Belay, A. (1994). Species composition and phytoplankton biomass in a tropical African lake (Lake Hawassa, Ethiopia). Hydrobiologia, 288, 13-32.
Kebede, E., Gebre-Mariam, Z., & Ahlgren, I. (1994). Ethiopian rift valley lakes: Chemical characteristics of a salinity alkalinity series. Hydrobiologia, 288, 1-12.
Kibret, T., & Harrison, A.D. (1989). The benthic and weed bed faunas of Lake Hawassa (Rift Valley, Ethiopia). Hydrobiologia, 174, 1-15.
Kifle, D., & Belay, A. (1990). Seasonal variation in phytoplankton primary production in relation to light and nutrients in Lake Hawassa, Ethiopia. Hydrobiologia, 196, 217-227.
Komarek, J., & Crenberg, G. (2001). Some chroococcalean and oscillatorialean cyanoprokaryotes from South African lakes, ponds, and pools. Nova Hedwigia, 73, 129-160.
Kunz, T.J., & Richardson, A.J. (2006). Impacts of climate change on phytoplankton. In: Impacts of climate change on Australian marine life: part C, literature review. (Eds A.J. Hobday, T.A. Okey, E.S. Poloczanska, T.J. Kunz, and A.J. Richardson) pp. 8-18. Report to the Australian Greenhouse Office, Canberra.
Lampert, W., & Sommer, U. (1997). Limnocology: The ecology of lakes and streams. Translated by J.F. HANEY. Oxford University Press, New York.
Lampert, W. (1988). The relationship between zooplankton biomass and Grazing: a review. Limnologica, 19, 11-20.
Lemma, B. (2003). Ecological changes in two Ethiopian lakes caused by contrasting human intervention. Limnologica, 33, 44-53.
Lewis, W.M. Jr. (1983). A revised classification of lakes based on mixing. Can. J. Fish. Aquat. Sci., 40, 1779-1787.
Lewis, W.M. Jr. (2002). Causes for the high frequency of nitrogen limitation in tropical lakes. Verh. Internat. Verein. Limnol., 28, 210-213.
LFDP. (1998). Final report. Lake Fisheries Development project working Paper.
Magnuson, J.J., Benson, B.J., & Kratz, T.K. (2004). Patterns of coherent dynamics within and between lake districts at local to intercontinental scales. Boreal Environment Research, 9, 359-369.
Magnuson, J.J., Kratz, T.K., & Benson, B.J. (2006). The challenge of Time and Space in Ecology. In: J.J. Magnuson, T.K. Kratz, and B.J. Benson (editors), Long-term dynamics of lakes in the landscape. Oxford University Press, pp. 400.
Makin, M.J., Kingham, T.J., Waddam, A.E., Birchall, C.J., & Teffera, T. (1975). Development projects in the southern rift valley of Ethiopia. Land Resource Study No. 21. Land resource division. Ministry of Overseas Development, England.
Mengistou, S. (1989). Species composition, dynamics and production of the dominant crustacean zooplankton in Lake Hawassa, Ethiopia. PhD dissertation. University of Waterloo.
Mengistou, S., & Fernando, C.H. (1991). Seasonality and abundance of some dominant crustacean zooplankton in Lake Hawassa, a tropical rift valley lake in Ethiopia. Hydrobiologia, 226, 137-152.
Mengistou, S., Green, J., & Fernando, C.H. (1991). Species composition, distribution and seasonal dynamics of Rotifera in a Rift Valley lake in Ethiopia (Lake Hawassa). Hydrobiologia, 209, 203-214.
Hawassamona, W., Elecia, E.-M., Carlton, C., & Dale, W. (2005). Phytoplankton and zooplankton as indicators of water quality in Discovery Bay, Jamaica. Hydrobiologia, 545, 177–193.
Neill W.E. and A. Peacock. (1980). Breaking the bottleneck: Interactions of invertebrate predators and nutrients in oligotrophic lakes. Am. Soc. Limnol. Oceanogr. Spec. Symp., 3, 715-724.
Rapport, D.J., Costanza, R., & Mcmichael, A.J. (1998). Assessing ecosystem health. – TREE, 13, 397-402.
Rott, E., & Lenzenweger, R. (1994). Some rare and interesting plankton algae from Sri Lankan reservoirs. Biologia, Bratislava, 49, 479-500.
Scheffer, M. (1998). Ecology of shallow lakes. Chapman and Hall, London, 357 pp.
Schneider, D.W. (1990). Direct assessment of the independent effects of exploitative and interference competition between Daphnia and rotifers. Limnol. Oceanogr., 35, 916–922.
Sommer, U. (1986). Phytoplankton competition along a gradient of dilution rates. Oecologia, 68, 503-506.
Talling, J.F., & Lemoalle, J. (1998). Ecological dynamics of tropical inland waters. Cambridge University Press.
Talling, J.F., & Driver, D. (1963). Some problems in the estimation of chlorophyll a in phytoplankton. Proc Conf. on primary productivity measurement, Marine and Freshwater. U.S. Atomic Energy Comm. TID-7633. 142-146pp.
Talling, J.F., & Talling, I.B. (1965). The chemical composition of African lake waters. Int. Revue ges. Hydrobiologia, 50, 421-463.
Taylor, W.D., & Gebre-Mariam, Z. (1989). Size-structure and productivity of the plankton community of an Ethiopian Rift Valley lake. Freshw. Biol., 21, 353-363.
Tilahun, G. (2007). Temporal dynamics of the species composition abundance and size-fractionated biomass and primary production of phytoplankton in lakes Ziway, Hawassa, and Chamo, Ethiopia. PhD dissertation. Addis Ababa University, Ethiopia.
Tilahun, G., & Ahlgren, G. (2010). Seasonal variations in phytoplankton biomass and primary production in the Ethiopian Rift Valley lakes Ziway, Hawassa, and Chamo – The basis for fish production. Limnologica-Ecology and Management of Inland Waters, 40, 330-342.
Tudorancea, C., & Taylor, W.D. (2002). Ethiopian Rift Valley Lakes. Backhuys Publishers, Leiden.
Voigt, M., & Koste, W. (1978). Rotatoria. Gebruder Borntraeger, Berlin, Stuttgart.
Welcome, P.L. (1972). The inland waters of tropical African CIFA Technical paper No. 1. FAO Rome, 117pp.
Wetzel, R.G. (2001). Limnology: Lake and river ecosystems. 3rd ed. Academic Press, San Diego, 1006pp.
Zinabu, G.M., Kebede, E., & Desta, Z. (2002). Long-term changes in chemical features of waters of seven Ethiopian rift-valley lakes. Hydrobiologia, 477, 81-91.