Safeguarding biodiversity in Lake Malawi

WATERLOO, Ont. -- Several University of Waterloo biologists are currently involved in a research project intended to preserve the diversity of the fish population in Lake Malawi in Africa.

Among the participants in the project supported by the World Bank through the Global Environment Facility are Profs. Bill Taylor, David Barton, Hamish Duthie and Stephanie Guildford. UW's portion of the funding covers the education of graduate students from Malawi, Tanzania and Mozambique, which share the lake's vast shoreline. It also covers research on the ecology of the lake.

Also known as Lake Nyasa (it is called Lake Nyasa/Niasa by Tanzanians), Lake Malawi occupies most of Malawi's eastern border in the small landlocked country in southeastern Africa surrounded by Mozambique, Zambia and Tanzania.

The Canadian contribution to the "Lake Malawi-Nyasa Biodiversity Conservation Project" is coordinated through Winnipeg's Freshwater Institute, Department of Fisheries and Oceans. The Canadian director is Bob Hecky of Environment Canada in Burlington and also a UW adjunct professor while Tony Ribbink from South Africa is heading up the project in Africa.

Lake Malawi is a "world treasure" in terms of biodiversity since it is estimated that up to 1,000 species of fish live there, and most of these live nowhere else. This is more than the total number of species to be found in all the lakes and rivers of Europe and North America combined.

Fish are a vital food resource for the people of Malawi, providing 75 per cent of the protein they consume. The family Cichlidae (cichlids) constitute most of the species and most of the commercial catch. The rock-dwelling cichlids are well known to aquariasts. Many are beautifully colored, as well as tasty. They are noteworthy for their ability to convert algae into protein; most feed on algae growing along rocky points and islands.

The researchers want to see the diversity of fish life in Lake Malawi preserved. They know that many species have already disappeared in Lake Victoria, to the north. By contrast, Lake Malawi is still in a "pristine condition," Taylor said. Yet there is concern about changing land use in Malawi, including deforestation. Such changes equally concern the people of Tanzania and Mozambique, countries that also border the lake, with the Malawi shoreline the most heavily populated of the three.

The UW research aims to study the water of Lake Malawi at various times during the year, to see if the supply of nitrates is increasing. A second major objective is to train graduate students from the countries around the lake to continue this research in the future, develop programs that will protect the fish populations and staff laboratories in the three countries. Five graduate students now are at UW -- one from Malawi, two from Tanzania and two from Mozambique.

Guildford has already made three trips to Malawi this year to measure the demand for nitrogen and other nutrients in the water throughout various periods -- the rainy season (last winter), the windy season (July), and the dry season (November).

Taylor said that Lake Victoria was similar to Lake Malawi some years ago in that there was great biodiversity within its fish population. But a good deal of this has been lost largely because of the introduction of non-native species, and eutrophication, which results in oxygen depletion in the lake water. One consequence of eutrophication is that Lake Victoria has become turbid to the point that brightly colored fish species cannot see each other clearly enough and they have begun to interbreed.

"We are getting to Lake Malawi early on," he said. "In fact the water there is usually as clear as a bell -- it can compare with our own Lake Superior. Once we learn what changes are taking place, and determine whether these changes may lead to problems, actions can be taken to forestall them. This will be the job of the graduate students now working with us here."

Guildford's studies include determining the phytoplankton in water samples, in order to quantify the extent to which nitrogen and phosphorous loading is affecting growth and species composition. She carries out physiological assays of water samples and has been working at the Senga Bay Research Station, which has the laboratory facilities she requires, as well as boats which she can use to take her water samples.

Her work indicates that nitrogen is the most limiting nutrient, regardless of the season. So far, however, nutrient limitation remains moderate. She has determined also that although the water is clear, the lake is very deep and weakly stratified in the top 250 metres and that light is a significant factor affecting the growth of algae.

A Canadian student, Scott Higgins, has started a master's thesis on biological nitrogen fixation, studying the rock-dwelling algae on which the cichlids feed. He is finding high rates of nitrogen fixation, which may explain how a thin "biofilm" of algae can support such a large fish population.

He has been finding that algae living on rocks in Lake Malawi are able to fix their own nitrogen. To do so, they use nitrogen from the atmosphere. In Canada, which of course has a much colder climate, such algae are associated with the development of toxins in our lakes and poor quality water. But this is not the case in Lake Malawi, which is just south of the equator.

Taylor said a further project is under way in connection with Lake Victoria. "We have students there now and though the Lake Victoria problems are more serious, the project is a somewhat comparable one."

Three students from the Lake Victoria area (Uganda and Tanzania) are also doing graduate work at UW, with the possibility of more yet to come. These students are looking at an already degraded system, and hope to discover ways of remediating the problems.

"In the meantime, we are training senior people of the future here; they will be the ones who will have to deal with whatever problem exists or may yet develop," Taylor said. The African graduate students now at UW will continue the work of monitoring the Lake Victoria and Lake Malawi situations in the future.

He is hopeful that any problems with Lake Malawi will prove more manageable since "we are getting at it quite early on." He is also hopeful that solutions will be found to mediate some of the more severe problems in Lake Victoria (for example, a way to effectively restore water quality), although the species that have already disappeared must be considered lost for all time.

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Written by Bob Whitton for the UW News Bureau, (519) 888-4444

UW experts/releases: http://www.adm.uwaterloo.ca/infonews/

Release no. 65 -- April 8, 1998