Diatom evidence for the timing and causes of eutrophication in Lake Victoria, East Africa

The determination of the history and causes of recent eutrophication and intensified thermal stratification in Lake Victoria is still hampered by the sparsity of paleolimnologic coverage of the enormous lake. Five new diatom records from Ugandan waters now show that a transition from Aulacoseira-dominated planktonic assemblages to those dominated by long Nitzschia spp., occurred in northern coastal sites from the mid-1970s to mid-1980s. Similar transitions developed from the late 1960s to early 1970s offshore and from the 1940s to early 1950s along the Kenyan coast, suggesting a time-transgressive process. These changes are not readily attributable to the trophic effects of Nile perch population growth during the early 1980s, but more likely reflect responses to long-term nutrient enrichment and climatic instability in the region. The diversity of planktonic diatom communities has declined dramatically, and a namesake variety of Aulacoseira nyassensis may now be nearly extirpated. Although local phytoplankton communities varied considerably in the past, the current domination of diatom assemblages by Nitzschia is apparently unprecedented in the 15,000-year history of Lake Victoria.

[1]  M. Munawar,et al.  The Great Lakes of the World (GLOW): Food-Web, Health and Integrity , 2001 .

[2]  R. Hecky,et al.  Pelagic Nitrogen Fixation in Lake Victoria (East Africa) , 2003 .

[3]  E. Worthington.  Observations on the Temperature, Hydrogen‐ion concentration, and other physical conditions of the Victoria and Albert Nyanzas , 1930 .

[4]  J. Halfman,et al.  Deep‐water warming trend in Lake Malawi, East Africa , 2005 .

[5]  R. Hecky,et al.  Hypothesized resource relationships among African planktonic diatoms , 1986 .

[6]  T. Acere.  Observations on the biology, age, growth, maturity and sexuality of Nile perch, Lates niloticus (Linne), and the growth of its fishery in the northern waters of Lake Victoria , 1985 .

[7]  P. Gikuma-Njuru,et al.  Nutrient concentrations in Nyanza Gulf, Lake Victoria, Kenya: light limits algal demand and abundance , 2005, Hydrobiologia.

[8]  T. Goldschmidt,et al.  Cascading Effects of the Introduced Nile Perch on the Detritivorous/Phytoplanktivorous Species in the Sublittoral Areas of Lake Victoria , 1993 .

[9]  L. Meeker,et al.  A 10,000-year high-resolution diatom record from Pilkington Bay, Lake Victoria, East Africa , 2003, Quaternary Research.

[10]  J. V. Sutcliffe,et al.  The Hydrology of the Nile , 1999 .

[11]  Peter B. O. Ochumba,et al.  Observations on blue‐green algal blooms in the open waters of Lake Victoria, Kenya , 1989 .

[12]  G. Kling,et al.  Multiple stressors cause rapid ecosystem change in Lake Victoria , 2010 .

[13]  L. Kaufman,et al.  Biodiversity and Fishery Sustainability in the Lake Victoria Basin: An Unexpected Marriage? , 2003 .

[14]  John T. Lehman,et al.  Lake Victoria Plankton Ecology: Mixing Depth and Climate-Driven Control of Lake Condition , 1998 .

[15]  J. Talling.  The photosynthetic activity of phytoplankton in East African lakes , 1965 .

[16]  T. Johnson,et al.  A 12,400 14c yr Offshore Diatom Record From East Central Lake Victoria, East Africa , 2000 .

[17]  M. Kanamitsu,et al.  NCEP–DOE AMIP-II Reanalysis (R-2) , 2002 .

[18]  J. Talling,et al.  The Annual Cycle of Stratification and Phytoplankton Growth in Lake Victoria (East Africa) , 1966 .

[19]  Gérard Prunier,et al.  The Rwanda Crisis: History of a Genocide , 1998 .

[20]  R. Hecky,et al.  Conservation of the African Great Lakes: A Limnological Perspective , 1993 .

[21]  S. Juggins,et al.  Physical and chemical predictors of diatom dissolution in freshwater and saline lake sediments in North America and West Greenland , 2006 .

[22]  E. Brown,et al.  History and timing of human impact on Lake Victoria, East Africa , 2002, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[23]  J. Stager.  Ancient Analogues for Recent Environmental Changes at Lake Victoria, East Africa , 1998 .

[24]  J. T. Lehman.  Environmental Change and Response in East African Lakes , 1998, Monographiae Biologicae.

[25]  Alexander Ruzmaikin,et al.  Sunspots, El Niño, and the levels of Lake Victoria, East Africa , 2007 .

[26]  H. Kling,et al.  Silica Depletion in Lake Victoria: Sedimentary Signals at Offshore Stations , 1998 .

[27]  A. Cohen,et al.  Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa , 2003, Nature.

[28]  R. Mugidde.  The increase in phytoplankton primary productivity and biomass in Lake Victoria (Uganda) , 1993 .

[29]  R. D. Ricketts,et al.  Late Pleistocene Desiccation of Lake Victoria and Rapid Evolution of Cichlid Fishes , 1996, Science.

[30]  R. Dorit,et al.  Destruction of fisheries in Africa's lakes , 1985, Nature.

[31]  S. Nicholson,et al.  Rainfall Conditions in Equatorial East Africa during the Nineteenth Century as Inferred from the Record of Lake Victoria , 2001 .

[32]  Monica F. Myers,et al.  Climate change and the resurgence of malaria in the East African highlands , 2002, Nature.

[33]  R. Hecky,et al.  The eutrophication of Lake Victoria , 1993 .

[34]  M. Binford,et al.  Calculation and uncertainty analysis of 210Pb dates for PIRLA project lake sediment cores , 1990 .

[35]  T. Johnson,et al.  The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota , 2007, Hydrobiologia.

[36]  R. Crul.  Limnology and Hydrology of Lake Victoria , 1995 .

[37]  J. Talling.  Some Observations on the Stratification of Lake Victoria , 1957 .

[38]  J. T. Lehman.  Role of Climate in the Modern Condition of Lake Victoria , 1998 .

[39]  B. Cumming,et al.  A High-Resolution 11,400-Yr Diatom Record from Lake Victoria, East Africa , 1997, Quaternary Research.

[40]  R. C. M. Crul,et al.  Limnology and hydrology of Lake Victoria : comprehensive and comparative study of Great Lakes : UNESCO/IHP-IV project M-5.1 , 1995 .

[41]  R. Tamatamah,et al.  The atmospheric deposition of phosphorus in Lake Victoria (East Africa) , 2005 .

[42]  P. Verburg,et al.  Ecological Consequences of a Century of Warming in Lake Tanganyika , 2003, Science.

[43]  P.A.M. van Zwieten,et al.  Are the Lake Victoria fisheries threatened by exploitation or eutrophication? Towards an ecosystem-based approach to management , 2008 .

[44]  L. Kaufman,et al.  Deoxygenation of the deep water of Lake Victoria, East Africa , 1994 .

[45]  Les Kaufman,et al.  Evolutionary and Conservation Biology of Cichlid Fishes as Revealed by Faunal Remnants in Northern Lake Victoria , 1993 .