Feature
of the Week
For
the Week of October 19, 2002
Botanical
Study Confirms Significance of Lake Pleasant
By Steve Grund, Botanist, Western Pennsylvania Conservancy
The
closer we look, the more it becomes clear that Lake Pleasant is a very
special place, and an important place to do conservation work. In the
1980's, the Natural Heritage Program staff of WPC visited and evaluated
seven glacial lakes in northwestern Pennsylvania. The result of this
work was the determination that Lake Pleasant was the most appropriate
lake to focus our conservation efforts. Lake Pleasant:
· harbors the largest number of aquatic species of concern,
· is associated with exceptional lakeside wetlands including
a fen,
· is the glacial lake with the least damaged ecosystem, and
· is the most defensible against outside disturbances.
WPC
is now working with the Cleveland Museum of Natural History on a study
of the plants that grow in these lakes, and the results lead us to feel
even better about our land purchases and other conservation efforts
at Lake Pleasant.
In June of 2001, WPC and the Cleveland Museum, with funding from the
Wild Resource Conservation Fund, began a five-year study of the flora
of all eight inland glacial lakes of northwest Pennsylvania. The eight
lakes are: Lake Pleasant, Edinboro Lake, Sugar Lake, Lake LeBoeuf, Sandy
Lake, Lake Canadohta, Conneaut Lake, and Crystal Lake. Crystal Lake,
which, depending on the criteria used, is either just big enough or
not quite big enough to qualify as a lake, was not included in the survey
done in the 1980's. So far, we have completed the mapping of submerged
and floating leaved plants at Lake Pleasant, Lake LeBoeuf and Edinboro
Lake. Water quality was noticeably better at Lake Pleasant, and the
flora was healthier than at the other lakes.
At three of the four lakes we studied, algae in the water has often
prevented direct observation of the plants growing beneath the surface
of the water. These algal blooms are symptoms of nutrient loading, which
can be caused by ineffective sewage treatment, overpopulation of certain
animals (mainly geese) or runoff of fertilizers from fields, pastures
and lawns. At Lake Pleasant, the situation is remarkably different.
Looking over the side of a canoe, one can see the plants on the bottom
as deep as plants will grow. Glass-bottomed buckets to cut the glare
of sunlight reflecting on the surface of the lake were all that was
needed to identify plants to species.
Lake Pleasant continues to be the only natural lake in western Pennsylvania
that has not been invaded with the invasive exotic plant called Eurasian
water-milfoil. This plant grows very fast, branches near the surface
of the water, and can produce a canopy at the top of the lake that shades
out the native species below.
Motorized boats are not allowed at Lake Pleasant. Motor boats chop up
aquatic plants. Some species may suffer from this disturbance, but others
sprout from the fragments, and actually become more abundant. This leads
to changes in the relative abundance of different species, and may account
for the fact that in the lakes we have studied that have motor boats,
species such as elodea and naiad, as well as Eurasian water-milfoil,
tend to dominate certain areas to the near exclusion of any other species.
This does not happen at Lake Pleasant, where one can look almost anywhere
the water is shallow enough for plants to grow and see a half dozen
or more species.
Lake
Pleasant's twenty rare plant species, the most for any lake in western
Pennsylvania, are doing well, and they have a bright future, thanks
to the watershed's landowners and the conservation work that continues
out of WPC's Northwest Field Station. Consider visiting Lake Pleasant
to see one of the finest examples of what you are accomplishing with
your WPC membership.
Our
Photo of the Week offers a unique perspective of those who study life
at Lake Pleasant. More...
