Water quality (the physical, chemical and biological properties of water) within Lake Michigan is important both to the organisms living within the lake, and to the human populations living around the lake. Within the lake, water quality plays an important role in controlling the productivity and composition of plankton, which in turn affect other organisms in the aquatic food web, including fish such as perch and salmon. For the human population, the lake serves as a major source of water for domestic, industrial and recreational use.

Water characteristics are altered by a variety of human activities including agriculture, industry, sewage production, urban application of fertilizers and herbicides, and the burning of fossil fuels. Most of these activities are particularly intense in the southwestern basin of Lake Michigan, which is adjacent to dense urban populations. In addition to direct anthropogenic impacts, water quality and ecosystem functioning may be altered by the introduction of exotic species, which has occurred repeatedly over the past century, and will likely continue.

Lake Michigan pelagic monitoring buoy. The buoy includes meteorological instruments and an automated profiler that collects water quality data from the surface to a depth of 100 m several times per day. Data are transmitted near-real-time to the WATER Institute.

Location of the monitoring buoy. Map produced by NOAA/GLERL.

Plankton are collected at each station using several kinds of nets. One collects algae (phytoplankton), and has a very fine mesh. The net in this photo is for collecting tiny animals (zooplankton), a favorite food of perch, for example.

Every station is sampled first with an electronic device similar to the one on the buoy. It measures temperature, oxygen, water clarity, and five other important parameters. Its use is particularly important in winter when the buoy is not operating.

In order to determine how human activities and exotic species introductions are affecting the water quality and general functioning of the Lake Michigan ecosystem, the Great Lakes WATER Institute operates a monitoring program in the Milwaukee region of the lake. Monitoring sites extend from the Milwaukee Harbor to a pelagic station 16 km offshore, and include a perch spawning reef and an urban water intake area. A suite of measurements is made at hourly to monthly time intervals at these locations, including temperature, water clarity, water chemistry, phytoplankton and zooplankton abundance, and bacterial and plankton productivity. Some of these measurements are made directly from the research vessel, Neeskay, while others are made in the WATER Institute laboratories. In addition, continuous near-real-time water quality and meteorological measurements will soon be available from a monitoring buoy that has been installed in the lake.

The monitoring program, along with measurements taken by the Linnwood water treatment plant since the 1930's, makes it possible to determine how the Lake Michigan ecosystem may be changing over time, and what the causes of those changes might be. By making a large variety of measurements over long time periods, scientists not only are keeping their finger on the pulse of the lake, but they are able to answer fundamental questions about the interactions between physical, chemical and biological processes in large lakes. In addition, the monitoring program provides support data and serves as a logistic platform for the development of new aquatic science technologies and for specific research projects.

In order to make data on Lake Michigan water quality available to the larger community of managers, researchers and educators, a web-based database is being developed that will allow users to access data via the internet. The web site will include data visualization tools, and will include near-real-time data collected by the monitoring buoy, as well as archived data sets, some of which extend back as far as the 1930's. The database can be accessed at http://waterbase.glwi.uwm.edu.

(click on the pictures for a larger view)