Lake Tanganyika
Research Experience for Undergraduates- The Nyanza Project in Kigoma, Tanzania, at Lake Tanganyika. Interdisciplinary program with courses in geology, limnology, and biology.
Independent project with Robia Charles involved the analysis of a chemical and physical profile 700 meters deep, in both the northern and southern sub-basins of Lake Tanganyika. Here is a brief synopsis of our final paper that can be found at: http://www.geo.arizona.edu/nyanza/pdf/adamscharles.pdf
Title: A preliminary investigation of lake stability and chemical analysis of deep waters of Kigoma sub-basin (northern basin) and the Kalemie sub-basin (southern basin) of Lake Tanganyika.
Objective: To compare the chemical and physical parameters that affect Lake stability in Kigoma sub-basin and in the Kalemie sub-basin of Lake Tanganyika with different total lake depths of 1200 and 800m, respectively.
Description: Lake stability is the amount of work needed for a water column to overcome thermal stratification, and hence vertical density differences in order to completely mix. Using knowledge of relevant mixing processes and density as a function of temperature, it is possible to show that thermal stratification results in high lake stability (no mixing); whereas, an isothermal condition causes low lake stability (complete mixing). In addition to this, deep-water nutrients (down to 700m) will be documented in order to determine the amount available for mixing into shallower waters and their relationship to physical lake stability. This is the environment of bacteria and the microbial loop. Therefore in order to more correctly assess paleolimnological data, it is necessary to understand the current physical and chemical conditions of deeper waters instead of only shallow sampling which allows analysis of a small portion of the water column.
Conclusion: The Wedderburn number, stratification index, buoyancy frequency and stability (Schmidt, 1928) equations all show that the overall stability of the lake is low during the dry season. From the south east winds, turbulence, upwelling and other seasonal effects, the south basin is less stable than the north basin. In fact, night cooling is a more important factor of less stratification in the Kalemie shoal, rather than upwelling in the far south. Testing at the northern end (July 25, 2000) was conducted at night; whereas, the southern testing was conducted during the day around 12pm (time of maximum irradiance). As a result, the temperature stratification in the north was not as strong as it would have been during the daytime. If both of the sites had been tested during the day at the same time, there would have been a larger difference in the results for the north and south in each mathematical equation. The conclusion of overall low lake stability suggests that nutrients such as nitrate, phosphorus and silica can diffuse across the metalimnion. Nitrate in the south basin is probably increased by a large flux of ammonium from the hypolimnion. Nitrogen dynamics should be further investigated by examining N-fixation in the epilimnion, denitrification in the metalimnion, and autotrophic populations throughout the water column. The increased dissolved inorganic carbon in the south basin is indicative of the geological factors affecting water masses in the different sub-basins. The Kalemie sub-basin wind-induced currents are controlled not only by regional wind patterns, but also largely by the Mahale Mountains offshore- inshore winds. Turbidity should theoretically be higher in the south basin as opposed to the north because of the turbation of sediments and local upwelling. The annual limnological cycle should correlate with changes in stability and various nutrient fluxes (chemical variations) into the epilimnion.
References:
Coulter, G.W. 1991. Lake Tanganyika and its Life. Oxford University Press. New York, New York.
Edmond, J., R.F. Stallard, H. Craig, V. Craig, R.F. Weiss and G.W. Coulter. 1993. The chemistry of the water column of Lake Tanganyika 1: The nutrient elements. Limnology and Oceanography. (Suppl.).
Hecky, R.E., E.J. Fee, H.J. Kling, and J.W. Rudd. 1978. Studies on the planktonic ecology of Lake Tanganyika. Canadian Department of Fish and Environment, Fisheries and Marine Service Technical Report. 816: 1-51.
Hutchinson, G. 1957. A Treatise on Limnology. Vol.1. John Wiley & Sons, INC. New York.
Patterson, G., Wooster, M. and Sear, C. 1995. Real-time Monitoring of African Aquatic Resources using Remote Sensing with Special Reference to Lake Malawi. Chatham, UK: Natural Resources Institute.
Plisnier, P.D., D. Chitamwebwa, L. Mwape, K. Tshibangu, V. Langenberg, and E. Coenen. 1999. Limnological annual cycle inferred from physical-chemical fluctuations at three stations of Lake Tanganyika. Hydrobiologia. 407: 45-58.
Rudd, J.W.M. 1980. Methane oxidation in Lake Tanganyika (East Africa). Limnology and Oceanography. 25: 958-963.
Wetzel, R. and Likens, G. 1990. Limnological Analyses. 2nd ed. Springer-Verlag, New York. 35-36pp