The MiCorps Monitor: Fall 2012
The newsletter of the Michigan Clean Water Corps,
39 Years of the Cooperative Lakes Monitoring
One of keystone
programs of MiCorps is the Cooperative Lakes Monitoring Program
(CLMP). The CLMP has been around since 1974… that is an impressive
length of time! Since that first year, the thousands of CLMP volunteers
across Michigan have:
- Taken 92,185 secchi disk measurements,
- Grabbed 4,274 water samples for phosphorus analysis,
- Filtered 5,956 water samples for chlorophyll,
- Made 2,023 observations of the dates that ice melted off their
- Measured dissolved oxygen and temperature 52,290 times and created
3,486 dissolved oxygen and temperature lake profiles, and
- Searched 17 lakes for exotic plants and mapped out full plant
communities on 12 lakes.
All of this data is entered
by our volunteers and staff into a publicly
accessible and searchable database!
In total, 827 inland lake
basins have been monitored through one test or another through the
CLMP. Michigan lake volunteers have contributed about 57,400 hours
of work, not counting the time spent driving samples to State offices
and going to trainings. Assuming field technicians across this time
period would make an average of $9/hour, that means these volunteers
have donated well over a half a million dollars in labor.
With 39 years
of data comes a variety of ways to consider how Michigan lakes have
changed over time. In this article, we will take a closer look at
two issues that CLMP data can address: trends in trophic status,
and the effects of zebra mussels on lakes.
in lake trophic status
ability to support plant and animal life defines its level of productivity,
or trophic status. Lakes are commonly put into categories based
on their productivity. These categories range from oligotrophic,
to mesotrophic, to eutrophic. Oligotrophic lakes are generally deep
and clear and have little algae growth and consequently cannot support
fish populations. By contrast, highly productive eutrophic lakes
are generally shallow, turbid, and support abundant aquatic plant
growth and fish, provided that they don’t develop low dissolved
oxygen levels. Lakes that fall between these two classifications
are called mesotrophic lakes. All of these categories can be more
truly understood as a continuum; for example, a mesotrophic lake
may be bordering on oligotrophic while its neighbor lake may be
mesotrophic but bordering on eutrophic. For more detail on trophic
states, see CLMP’s
enrolled in the CLMP take water transparency, phosphorus, and chlorophyll
measurements for their lakes, which are used to place that lake
into one of the trophic categories. By taking these measurements
year after year, we can track how individual lakes change as well
get a sense of how the overall condition of lakes in the program
are changing in time.
Michigan has a mix of oligotrophic,
mesotrophic, and eutrophic lakes. From 1980 through 2000, about
65% of lakes in the CLMP were classified as mesotrophic, about 20%
were oligotrophic and 20% were eutrophic. Hypereutrophic lakes,
which are lakes on the very high end of the eutrophic category,
are rare, but there are usually 2 or 3 of these lakes enrolled in
the program at any one time.
there were significantly more oligotrophic lakes in the program
(34%), while the numbers of eutrophic (11%) and mesotrophic (54%)
lakes dropped. This result can indicate one of two things: 1) more
oligotrophic lakes joined the program and perhaps the other types
lakes dropped out, or 2) lakes that were previously categorized
as mesotrophic had an improvement of water quality and were reclassified
indicate that the second option above is indeed what is happening
here. By only looking at lakes that were enrolled in the program
throughout 1980-2010, we do see that many of them change from a
mesotrophic to an oligotrophic state. Therefore, we do have evidence
that some lakes are becoming less productive over time, probably
due to improved lake management activities, or in some cases, zebra
A valid question
to ask is whether this analysis can be applied to all of the lakes
in Michigan. Certainly, the Upper Peninsula is very underrepresented
and thus this analysis should not be thought to reflect conditions
there. In addition, lakes enrolled in the CLMP are usually monitored
because there are many people that live on those lakes and care
for them. With this in mind, it is reasonable to argue that these
results can be representative of residential lakes in the Lower
Changes in lakes in relation
to zebra mussels invasions
Zebra mussels are an infamous creature throughout the United States,
and the Great Lakes and inland lakes in the midwest in particular
have had to struggle against these mollusk invaders. As filter feeders,
zebra mussels can directly change the water quality of a lake as they
consume algae from the water column. Since the CLMP measures water
transparency, phosphorus, and chlorophyll, the program is well situated
for studying how zebra mussels have affected these water quality parameters.
Through the help of CLMP volunteers throughout Michigan,
I obtained the infestation years for 206 lakes enrolled in the CLMP.
I more closely examined 30 lakes which had at least 6 years of secchi
disk transparency data for both before and after the lake was infested.
Where it was available, I also looked at the phosphorus and chlorophyll
data for these 30 lakes. It was readily apparent that lakes respond
in a huge variety of ways to the presence of zebra mussels.
Eleven of the 30 lakes showed
the expected response with a noticeable increase in water transparency
after the zebra mussel invasion. For example, after the zebra mussels
entered Van Etten Lake in 2001, the average transparency increased
from around 5 feet to around 9 feet. The total phosphorus also decreased
significantly, and the average chlorophyll measurements decreased
Fourteen of the 30 lakes did
not seem to change at all after the zebra mussel invasions. The
exact reason for this differs from lake to lake, and would be impossible
to determine without a concentrated study of each of the lakes.
One possible explanation is that the zebra mussel population was
never able to flourish, perhaps because of the lack of suitable
hard surfaces for the mussels to latch on to. Another possible explanation
for this is that nutrient inputs increased to the lake and were
able to nullify the effect of the mussels. Corey Lake in St. Joseph
County is one example of a lake that did not change after zebra
Five of the 30 lakes changed
in a manner that is contradictory to the expected results of a zebra
mussel invasion; the lakes had a reduction in water transparency.
This rather confounding discovery makes it clear that in dealing
with biological responses, the analysis is rarely cut and dried,
and there are a myriad of environmental variables that are acting
upon the system which are difficult to quantify or understand. Cedar
Lake in Van Buren County is an example of this intricate issue.
After the zebra mussel invasion, the average secchi transparency
decreased from 16 feet to 12 feet, while both the phosphorus and
chlorophyll also dropped. This is the expected response from phosphorus
and chlorophyll, but the opposite response from water transparency.
years is a long time for any program to run, and this should be
a cause of celebration for the MiCorps community. However, lakes
change over the course of decades and centuries, so we need to stay
vigilant in monitoring and measuring. Collecting and analyzing water
quality will continue to be an important part of understanding how
human activities affect our lakes and will continue to inform planning
and management decisions.
Paul Steen, Ph.D.
Huron River Watershed Council