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Biological productivity; Lakes--Minnesota; Marl


Physical and chemical characteristics of four dimictic eutrophic lakes of northcentral Minnesota with marl deposits are discussed in relation to production of invertebrate animals (benthos and plankton) that are the basic food of fish . Two of the lakes have a history as "productive" fish lakes and the other two as "problem" fish lakes. The "productive" lakes, as a type, have a larger surface area, a longer shallow-water littoral shelf, and a lower proportion of marly soils in the littoral zone than do the "problem" lakes. The standing crop of invertebrates was about twice as great per habitat unit in the "productive" as in the "problem" lakes. Surface waters of the "productive" lakes were somewhat higher in total phosphorus, total nitrogen and total iron than in the "problem" lakes. Since the "productive" lakes have brownish or greenish water as opposed to clear water in the "problem" lakes, chelation of iron and other trace metals by organic compounds also may be involved in productivity.

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Biology Commons



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