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Leonard C. Beadle In contrast to the more sta bie oceans, inland waters are, on the geological time scale, short-lived and are subject to great fluctuations in chemical composition and physical features. Very few lakes and rivers have existed continuously for more than a million years, and the life of the majority is to be measured in thousands or less. Earth movements, erosion and long-term climatic changes in the past have caused many of them to appear and disappear. No wonder then that most freshwater organism are especially adapted to great changes and many even to temporary extinction of their environment. Recent studies of residual sediments from existing and extinct lakes in tropical Africa have told us much about their age and the past history of their faunas and floras, from which we may deduce something about the climate and the conditions in the water in the past. The forces that have formed and moulded the African Great Lakes have been catastrophic in their violence and effects. They are not yet finished, but the present rate of change is, in human terms, too slow for direct observation of the ecological effects. The large man-made lakes are providing very good opportunities for studying the chemi cal and biological consequences of the initial filling but, once filled, they are artificially protected against major fluctuations.
List of contents
1. The environmental setting.- 1. Introduction: Perspectives of research at Lake Chilwa.- 2. The physical environment of Lake Chilwa.- 3. The changes in the lake level.- 4. The aquatic environment: I. Chemical and physical characteristics of Lake Chilwa.- 5. The aquatic environment: II. Chemical and physical characteristics of the Lake Chilwa swamps.- 2. The response of plants and animals to changes.- 6. Algae in Lake Chilwa and the waters of its catchment area.- 7. The distribution of aquatic macrophytes in Lake Chilwa: Annual and long-term environmental fluctuations.- 8. Zooplankton in Lake Chilwa: adaptations to changes.- 9. Decline and recovery of the benthic invertebrate communities.- 10. Invertebrate communities in the Lake Chilwa swamp in years of high level.- 11. Fishes: Distribution and biology in relation to changes.- 12. The fisheries of Lake Chilwa.- 13. Interactions between swamp and lake.- 14. Amphibians, reptiles, mammals and birds of Chilwa.- 15. Insects of the floodplain.- 3. The people of the Chilwa area.- 16. The influence of history on Lake Chilwa and its people.- 17. The people and the land.- 18. Fishing and fish trading: Socio-economic studies.- 19. Health and education.- 4. Conclusions.- 20. The Lake Chilwa ecosystem - A limnological overview.- 21. Focus on social problems.- Appendix A. A provisional checklist of plants and animals at lake Chilwa.- Index to Authors.
