Comparative study on the grazing-and detritus-food chains in the littoral benthic community of Lakes Baikal (Boreal), Biwa (Temperate) and Malawi (Tropical).

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Comparison of grazing- and detritus-food-chains on the littoral bottom in boreal Lake Baikal, temperate Lake Biwa, and tropical Lakes Malawi was carried out from 2003 to 2005 by the underwater experiment to test a hypothesis on the bottom-up constraint influencing the evolutionary development of high biodiversities in these lakes. The bottom-up constraint may be prominent where the abundance of benthic organisms in the grazing-food-chain is restricted by a seasonally lowest production, referring chiefly to attached algae, and large fluctuations in the abundance of primary producers provide a resource that is eventually utilized by benthic organisms of the detritus-food-chain. This hypotheses help to explain, for the lakes we cite, the facts that diverse grazing-food-chain organisms live on the littoral bottom of tropical lakes where there is relatively constant large algal production due to suitable conditions of water temperature and light penetration through the year ; while on the other hand, detritus-food-chain organisms are predominant on the littoral bottom of a boreal lake with seasonally fluctuating algal production and its pronounced lowest production in a year. The results based on the field surveys (measurement of DO based primary production and respiration, benthic animal community and their food, amount of detritus) during in the term of this project practically verify above hypothesis.