A comparative lake survey of four northern Michigan lakes: Lost Lake.

Abstract

Freshwater lakes with relatively low nutrient availability and low productivity are often placed under the rubric ""oligotrophic."" However, the status of oligotrophy only generally describes the productivity of a lake; it is limited in that it cannot be used to characterize the particular set of chemical, physical, and biological dynamics of the watershed and lake ecosystem which determine productivity. A comparative survey of four very different Michigan lake systems was conducted by UMBS limnologists during the summer of 1998. The survey was intended to evaluate the particular dynamics of each lake-watershed ecosystem and the effects of these dynamics on the trophic status of the lake. Lost Lake, a small, calcareous, hard-water solution lake located in northern Otsego Co., MI, was surveyed on 4 July 1998 as part of this comparative project. The geology and small size of the watershed have the greatest impact on the overall trophic status; the lake receives very little P and N from the minimal watershed, and appears to be phosphorus-limited based on the N:P ratio. The precipitation of Ca CO3 and subsequent adsorption of phosphorus and organic carbon driven by photosynthesis in the euphotic zone, may also contribute to the nutrient limitation. With such low productivity, the lake does not support a very extensive trophic system: levels of chl a and zooplankton are relatively low, as are diversity of fish, invertebrates and macrophytes. While the system appears to be affected by both top-down and bottom-up control, button-up nutrient limitation seems to more strongly affect the trophic structure and oligotrophic status.