Mysterious Nitrogen Sources Fuel Algae in African Great Lake
Ann Arbor, MI — Microscopic algae of northern Lake Tanganyika (Central Africa) are using more nitrogen than they obtain from rivers and falling dust and rain.
Surface waters of northern Lake Tanganyika have very low levels of nitrogen, an essential food source for microscopic algae. However, these algae proved to grow very efficiently, sustaining a whole productive food chain generating large fish biomasses used by the local populations. Where then does the nitrogen come from?
The Rusizi River, located at the frontier between Burundi and RD Congo, is the largest inflowing river of Lake Tanganyika and annually contributes around 2,000 tons of nitrogen to lake waters. Additional nitrogen-containing gasses and dust particles is massively produced over the African continent by savanna, bush and forest fires. Those gasses and particles mix directly with surface lake water or dissolve in falling rainwater. They represent an additional source of 1,500 tons of nitrogen per year.
Microscopic algae then use this nitrogen as a food source, totaling 14,500 tons in a single year! The 3,500 tons of nitrogen brought by rivers and dust and rainfall thus only represent a small fraction (around 25%) of the used nitrogen.
These findings clearly show that more investigations will be needed if we want to discover the mysterious origin of how nitrogen levels support high algal and fish production in northern Lake Tanganyika.
Original Publication Information
Results of this study "Inorganic Nitrogen Uptake and River Inputs in Northern Lake Tanganyika," are reported by Natacha Brion, Evariste Nzeyimana, Leo Goeyens, David Nahimana, Clavery Tungaraza and Willy Baeyens in the latest issue (Volume 32, No. 3, pp. 553-564) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2006.
Contacts
For more information about the study, contact Natacha Brion, Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium; nnbrion@vub.ac.be; +32 2 629 27 16.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.