Morphometry as a dominant factor in the productivity of large lakes

Summary

The early efforts of limnologists to understand the processes of biological production in lakes, led to the primary classification of lakes on a trophic basis. In this classification the edaphic situation, controlling the supply of nutrient materials from the watershed, is regarded as the primary determinant of trophic condition. It was soon recognized that the morphometry or shape of the lake basin, might also determine trophic type. It is obvious also that in some regions climate will provide a third set of factors which will dominate the situation.

It appears that morphometric factors have a dominant effect on biological production in many large lakes across Canada. This conclusion is supported by the demonstration of inverse correlation between mean depth and the standing crops of net plankton, and between mean depth and macroscopic bottom organisms in some 20 large lakes. Mean depth has also been correlated inversely with the long-term fish production of the Great Lakes and other large lakes in western Canada. It is possible that long-sustained fish production may be a better indication of productivity than the standing crops of plankton and bottom fauna. Equations have been derived and curves drawn to represent the theoretical relationship between mean depth and amounts of plankton, bottom fauna and fish production in these lakes. Deviations of the actual amounts of these materials from those expected theoretically appear in most cases to be attributable to the modifying effects of climatic or edaphic conditions.