Deep holes: Interdepression differences in trophic state in Douglas Lake, Michigan.

Abstract

Historically the deep basins of Douglas Lake have behaved almost as independent lakes in terms of temperature, pH, and dissolved oxygen and carbon dioxide. These depressions have shown high yearly variability. It is also known that Douglas Lake is eutrophying. Rates of eutrophication may be different between the lake's depressions due to higher nutrient inputs from housing development on the western side of the lake. This study examined physical, chemical and biotic factors of two deep depressions in Douglas Lake to observe whether this pattern has remained consistent in the fifteen years since this topic was last studied. We conclude that the depressions still have individual chemical and physical characteristics. In particular the South Fishtail Bay Depression has higher concentrations of most nutrients than the Fairy Island Depression and is more eutrophic. The depression individuality is still poorly understood and merits further investigation.