Effect of wind induced water movements on nutrients, chlorophyll-a, and primary production in Lake Tanganyika
Keywords:
Shear stress, Wedderburn, mixing cycles, upwellingAbstract
We determined the spatial and temporal distribution of major plant nutrients, dissolved oxygen, chlorophyll-a and primary production, at three deep-water locations in Lake Tanganyika to infer patterns of water displacements and to interpret the impact of wind-generated changes in nutrients on the timing and magnitude of phytoplankton production.
In the southern end of the lake, the onset of cooler, windier conditions during May–September caused stratification weakening, tilting of isotherms and upwelling of dissolved inorganic nitrogen and soluble reactive phosphorus from nutrient-rich deeper waters. These factors coincided with an increase in chlorophyll-a concentrations but not with clear evidence of increased primary production. An internal seiche at that time seemed associated with similar but less pronounced events at the other stations after cessation of the winds.
We suggest that internal seiching can spread kinetic energy throughout the lake, triggering upward nutrient fluxes through mixing elsewhere. The response to water displacements in terms of nutrient supply to the epilimnion seems to be governed by differences in the strength of vertical temperature, and by nutrient and dissolved oxygen gradients. At the most northern station, these gradients were strongest and closest to each other and throughout the year primary production rates, phosphorus and chlorophyll-a concentrations in the euphotic zone appeared generally higher than at the other stations, probably also because of increased nutrient input from the Rusizi River.
We emphasise that the intra- and interannual differences between the strength of lake stratification and wind regime are of major importance in determining the extent of upwelling events upwind as well as internal seiching strength and duration. That consequently affects the extent of internal nutrient loading throughout the lake and ultimately plays an important role in the lake trophic status.
References
Allanson, B. R. 1990. Physical processes and their biological impact. Verb. Internat. Verein. Limnol., 24: 112–116.
Chen, C. T. and Millero, F. J. 1977. The use and misuse of pure water PVT properties for lake waters. Nature, 266: 707–708.
Coulter, G. W. 1988. Seasonal hydrodynamic cycles in Lake Tanganyika. Verb. Internat. Verein. Limnol., 23: 86–89.
Coulter, G. W. and Spigel, R. H. 1991. “Hydrodynamics.”. In 1991 Lake Tanganyika and its Life, Edited by: Coulter, G. W. 49–75. UK: British Museum and Oxford Univ. Press.
Edmond, J. M., Stallard, R. F., Craig, H., Craig, V., Weiss, R. F. and Coulter, G. W. 1993. Nutrient chemistry of the water column of Lake Tanganyika. Limnol. Oceanogr., 38(4): 725–738.
Fer, I., Lemmin, U. and Thorpe, S. A. 2002. Observations of mixing near the sides of a deep lake in winter. Limnol. Oceanogr., 47(2): 535–544.
Garrett, C., MacCready, P. and Rhines, P. 1993. Boundary mixing and arrested Ekman layers: rotating stratified flow near a sloping boundary. Ann. Rev. Fluid Mech., 25: 291–323.
Hecky, R. E., Spigel, R. H. and Coulter, G. W. 1991. “The nutrient regime.”. In 1991 Lake Tanganyika and its Life, Edited by: Coulter, G. W. 76–89. UK: British Museum and Oxford Univ. Press.
Huttula, T. 1997. Flow, thermal regime and sediment transport studies in Lake Tanganyika. Kuopio University Publications C. Natural and Environmental Sciences., 73: 1–173.
Imberger, J. 1979. “Mixing in reservoirs.”. In Mixing in Inland and Coastal Waters, Edited by: Fisher, H. B., List, E. J., Koh, R. C. Y. and Brooks, N. H. New York: Academic Press. Chapter 6
Imberger, J. 1994. “Transport processes in lakes: a review article.”. In Limnology Now, a Paradigm of Planetary Problems, Edited by: Margalef, R. 99–193. UK: Elsevier.
Imberger, J. and Patterson, J. C. 1990. Physical limnology. Adv. Appl. Mech., 27: 303–475.
Ivey, G. N. and Nokes, R. I. 1989. Vertical mixing due to the breaking of internal waves on sloping boundaries. J. Fluid Mech., 204: 479–500.
Kotilainen, P., Huttula, T. and Peltonen, A. 1995. Lake Tanganyika hydrodynamics (results of March 1993-December 1994). FAO/FINNIDA Research for the Management of the Fisheries on Lake Tanganyika, Rome: Food and Agricultural Organization. GCP/RAF/271/FIN-TD/43 (En)
Langenberg, V. T. and Nyamushahu, S. 1997. Nutrient precipitation in the northern part of Lake Tanganyika, FAO/FINNIDA Research for the Management of the Fisheries on Lake Tanganyika Rome: Food and Agricultural Organization. GCP/RAF/271/FIN-TD/75 (En)
Langenberg, V. T., Mwape, L. M., Tshibangu, K., Tumba, J.-M., Koelmans, A. A., Roijackers, R., Salonen, K., Sarvala, J. and Mölsä, H. 2002. Comparison of thermal Stratification, light attenuation and chlorophyll-a dynamics between the ends of Lake Tanganyika. Aquat. Ecosyst. Health Manage., 5(3): 255–265.
Lindqvist, O. V., Mölsä, H., Salonen, K. and Sarvala, J. 1999. From Limnology to Fisheries: Lake Tanganyika and other large lakes. Hydrobiologia, 407: vii
Maclntyre, S., Flynn, K. M., Jellison, R. and Roméro, J. R. 1999. Boundary mixing and nutrient fluxes in Mono Lake, California. Limnol. Oceanogr., 44(3): 512–529.
Mortimer, C. H. 1952. Water movements in lakes during summer stratification; Evidence from the distribution of temperature in Windermere. Phil. Trans. Soc. Lond. B., 236: 355–405.
Ostrovsky, I., Yacobi, Y. Z., Walline, P. and Kalikhman, I. 1996. Seiche-induced mixing: its impact on lake productivity. Limnol. Oceanogr., 41(2): 323–332.
Patterson, J. C., Hamblin, P. F. and Imberger, J. 1984. Classification and dynamic simulation of the vertical density structure of lakes. Limnol. Oceanogr., 29(4): 845–861.
Plisnier, P-D., Chitamwebwa, D., Mwape, L. M., Tshibangu, K., Langenberg, V T and Coenen, E. 1999. Limnological annual cycle inferred from physical-chemical fluctuations at three stations of Lake Tanganyika. Hydrobiologia, 407: 45–58.
Plisnier, P-D. 1996. Limnological sampling during a second annual cycle (1994-1995) and some comparisons with year one on Lake Tanganyika, Rome: Food and Agricultural Organization. FAO/FINNIDA Research for the Management of the Fisheries on Lake Tanganyika GCP/RAF/271/FIN-TD/56 (En)
Salonen, K. and Sarvala, J. 1995. Field manual for the determination of chlorophyll and primary production in Lake Tanganyika research, Rome: Food and Agricultural Organization. FAO/FINNIDA Research for the Management of the Fisheries on Lake Tanganyika. GCP/RAF/271/FIN-FM/18 (En)
Salonen, K., Sarvala, J., Järvinen, M., Langenberg, V T, Nuottajärvi, M., Vuorio, K. and Chitamwebwa, D. B. R. 1999. Phytoplankton in Lake Tanganyika--vertical and horizontal distribution of in vivo fluorescence. Hydrobiologia, 407: 89–103.
Sarvala, J., Salonen, K., Järvinen, M., Aro, E., Huttula, T., Kotilainen, P., Kurki, H., Langenberg, V T., Mannini, P., Peltonen, A., Plisnier, P-D., Vuorinen, L., Mölsä, H. and Lindqvist, O. 1999. Trophic structure of Lake Tanganyika: carbon flows in the pelagic food web. Hydrobiologia, 407: 149–173.
Schindler, D. W., Schmidt, R. V. and Reid, R. A. 1972. Acidification and bubbling as an alternative to filtration in determining phytoplankton production by the C14 method. J. Fish. Res. Bd. Can., 29: 1627–1631.
Spigel, R. H. and Coulter, G. W. 1996. “Comparison of hydrology and physical limnology of the East African Great Lakes: Tanganyika, Malawi, Victoria, Kivu and Turkana (with reference to some North American Great Lakes).”. In The Limnology, Climatology and Paleoclimatology of the East African Lakes, Edited by: Johnson, T. C. and Odada, E. O. 103–139. Amsterdam: Gordon and Breach Publ..
Verbürg, P., Kakogozo, B., Makasa, L., Muhoza, S. and Tumba, J.-M. 1998. Hydrodynamics of Lake Tanganyika: 1993-1996, Synopsis and interannual comparisons, Rome: Food and Agricultural Organization. FAO/FINNIDA. Research for the Management of the Fisheries on Lake Tanganyika. GCP/RAF/271/FIN-TD/87 (En)
Published
Issue
Section
License
Manuscripts must be original. They must not be published or be under consideration for publication elsewhere, in whole or in part. It is required that the lead author of accepted papers complete and sign the MSU Press AEHM Author Publishing Agreement and provide it to the publisher upon acceptance.
