These small fish in turn provide food for the growth of larger fish. All in all, there is a high production of organic matter, like corn planted in rich soil. Much of this organic matter drifts to the bottom and forms a considerable depth of organic sediment. This sediment in turn provides the food for high numbers of bacteria. The descending plankton and the bacteria, through their respiration, can use up much or all of the oxygen from the lower depths of these lakes.
Eutrophic lakes are often relatively shallow and often have weed beds.
Most of Michigan's eutrophic lakes are in the lower two-thirds of the Lower Peninsula. So the oligotrophic and eutrophic lakes are contrast ends of the eutrophic continuum. After all, as the oligotrophic lake ages, it gradually accumulates nutrients and sediments, and moves toward and eventually into the eutrophic stage. This natural eutrophication process commonly takes thousands of years and involves both the physical filling of the lake and chemical enrichment of the lake water. Cultural eutrophication, which can occur in a human generation or two, involves chemical enrichment of the lake water by human activity in the lake drainage basin.