Jon Schlote
Lake Tanganyika
Objective:
Briefly discuss aspects of the ecology and management of Lake Tanganyika while emphasizing the
drivers of phytoplankton and fish diversity.
Introduction:
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Lake Tanganyika is a 32,000 km2 tectonic lake located on the western side of the Albertine Rift
Valley in East Africa. It is the second deepest lake in the world, bounded by Tanzania, Burundi,
Congo, and Zambia.
The lake surface is about 800m above sea level, the maximum water depth=1470m (Soreghan,
1996), mean depth=572m, a series of half-graben basins, 80-160km long and 30-80km wide
make up the lake (ILEC, 2010).
90% of the water accumulation and loss are a result of rainfall and evaporation. The thermocline
ranges between 50-120m deep, and the lake is meromictic (Soreghan, 1996).
Overexploitation of fish, introduction of exotic species, degradation of habitat and pollution have
led to declines in fish catches, reductions in fish species diversity and water quality degradation in
Lake Tanganyika (Ogutu-Ohwayo, 1997).
Over 200 species of Cichlids, greatest diversity in terms of morphology, ecology and breeding
styles (Koblmüller, 2008). The lake is dominated by chlorophytes and cyanobacteria, with an
increased appearance of diatoms in the dry season (Descy, 2010).
Selected Publication:
Descy et al. (2010) attempted to discover the drivers of phytoplankton diversity in Lake Tanganyika. He
analyzed chlorophylls and carotenoids in water column samples from 2002 through 2006, at two study
sites. Using CHEMTAX software, the contributions of the main algal groups to chlorophyll a, variations
of phytoplankton composition and biomass were determined. Dissolved nutrients and zooplankton
abundance were tested for; to explore the relationship between phytoplankton, zooplankton and nutrients.
Results suggest that several phytoplankton taxa can coexist in the pelagic zone because of differential
vertical distribution in the water column, which allow spatial partitioning of light and nutrients, and
temporal variability along with the effects of predation by grazers.
Selected Management Problem:
The pelagic fishery of Lake Tanganyika has focused on three fish since the 1950’s; Stolothrissa
tanganicae, Limnothrissa miodon and the perch Lates stappersii. The fishery has experienced problems
in the past and now there is a declining trend in perch abundance and biomass tied to local over-fishing
and climate change. Human population growth and refugee influx are both causing high fish protein
demand (Kimirei, 2008).
Glossary:
Half-graben: a sedimentary basin where one side is bounded by an extensional fault.
Meromictic: water in this type of lake never completely circulates.
Thermocline: A layer of water where temperature changes rapidly over depth.
Cichlids: Large family of tropical fish species characterized by a broken lateral line, brilliant
and specialized breeding behavior.
Cyanobacteria: Photosynthetic prokaryotes.
Chlorophytes: A division of green algae.
Diatoms: Algae with hard, silica-based shells.
Pelagic: open water that is not near the coast or sea-bottom.
colors
Jon Schlote
Cornet,Y., et al. “Limnological variability and pelagic fish abundance ( Stolothrissa tanganicae
and Lates stappersii) in Lake Tanganyika.” Hydrobiologia 625.1 (2009): 117-134.
Academic Search Complete. EBSCO. Web. 21 Mar. 2011.
Descy, J., et al. “Drivers of phytoplankton diversity in Lake Tanganyika.” Hydrobiologia 653.1
(2010): 29-44. OhioLink. EJC. Web 21 Mar. 2011.
International Lake Environment Committee. “Lake Tanganyika.” (2010). Web. 21 Mar. 2011
Koblmüller, S., Sefc, K., Sturmbauer, C. “The Lake Tanganyika cichlid species assemblage:
recent advances in molecular phylogenetics.” Hydrobiologia 615.1 (2008): 5-20.
Academic Search Complete. EBSCO. Web. 21 Mar. 2011.
Ogutu-Ohwayo, R., Hecky, R. E., Cohen, A. S., Kaufman, L. “Human impacts on the African
Great Lakes.” Environmental Biology of Fishes 50 (1997):117-131. OhioLink. EJC. Web.
21 Mar. 2011.
Soreghan, M. J., Cohen, A. S. “Textural and Compositional Variability Across Littoral Segments
of Lake Tanganyika: The Effect of Asymmetric Basin Structure on Sedimentation in
Large Rift Lakes.” AAPG Bulletin 80.3 (1996): 382-409. OhioLink. EJC. Web. 21 Mar.
2011.