Water Quality

Ecoli Sampling
The Manistee Health Department started in 2013 to sample Bear Lake to determine if ecoli levels could be harmful to humans.  In other words, is there any danger for our children, grandchildren or even adults to have full or partial body contact with the lake.

Below is a 2013 detailed report prepared by the Manistee Health Department regarding their sampling program as well as the 2013 through current ecoli level reports for Bear Lake were not harmful.

                                2016 Bear Lake Ecoli Report                2013 Health Dept Report
Trophic Level
The classification of the productivity of freshwater lakes was developed in Germany in the 1920’s.  Productivity is defined as the rate at which energy is stored by photosynthesis in rooted plants, algae and diatoms to form organic substances.  More simply, excessive nutrients provide food for plants to grow more.  Less is good.  

There are three trophic levels.

Oligotrophic – BEST - These are lakes that are deep and have low productivity.  Oligotrophic lakes generally have high levels of dissolved oxygen even at significant depths that allow for survival of species such as trout and whitefish even during the warmest periods of the year.

Mesotrophic – GOOD – These lakes fall in the middle of the spectrum between oligotrophic and eutrophic.  Bear Lake and most lakes in Michigan are in this category.

Eutrophic – BAD – These lakes have very high levels of productivity.  They are generally shallower, and in terms of ecological succession are considered geologically old.  The key to increased productivity of eutrophic lakes, in addition to its shallower depth, is often the availability of nutrients, particularly phosphorus and nitrogen that support plant growth.  Lakes that are in an extreme eutrophic state have large areas of rooted aquatic plant growth, occasional significant algal blooms and some depletion of oxygen.  

For a more complete explanation of water quality measurements, please refer to pages 79-91 of the Greater Bear Management Plan in the Plan tab of this website.

Below is the most current chart of measurements that indicate Bear Lake is in the Mesotrophic state which is the middle level or good.

                               April 2013 BL Eutrophication Indices


Dissolved Oxygen
Generally with this measurement, more is better.  Fish need oxygen.  Bear Lake is not in the danger zone.

Click below to view the most current chart of Bear Lake dissolved oxygen readings.

                                 2013 BL DO 4.6.14