Water Quality and the
Monoosnoc Brook
by April D. Ridlon
Leominster is losing its wild spaces. As
more people move into the city, more homes and businesses are being built,
less natural land is left untouched. The Monoosnoc Brook is one of
Leominster’s thriving natural ecosystems.
While the brook runs through countless backyards, beside and under busy
streets, and even weaves its way behind the parking lots at the Searstown
Mall, it sustains a diverse and abundant range of wildlife.
As a biology student
in college, I conducted a five-month study of the water quality and
biodiversity (the amount, quality and quantity of wildlife supported) of a
section of the Monoosnoc Brook that runs from Pierce’s (Roaches) Pond to the
diverging of Maple and West streets. One of my concerns was that too much
of the natural wetland area that surrounds the brook on both sides had been
degraded, and that as a result, the aquatic condition of the brook might
also be degraded. Natural wetlands act as buffers filtering out toxins such
as street runoff, soil erosion and other pollutants before they reach the
stream.
By monitoring water
quality parameters of dissolved oxygen, carbon dioxide, nitrogen, phosphate
and iron, I was able to trace the aquatic conditions available to the
submerged inhabitants of the brook. I also sampled some of the benthic
macroinvertebrates (insects that live on and in the streambed) and wetland
vegetation around my sample sites. What I found was a relatively healthy
habitat but overloaded by high levels of phosphorous and iron.
Both iron and
phosphate can become very harmful in the levels that I found in the brook.
During my study, I found iron levels up to 8 times higher than the limit
set by the US Public Health Service. In fact, iron levels were consistently
high so that only 3 samples out of 31 fell within the health standards.
Phosphate is an important nutrient needed for plant growth but extra
phosphate in the system can cause rapid plant growth that will choke the
brook. The amount of phosphate I detected for Monoosnoc far exceeded limits
set by US Public Health Service. All site averages for phosphate levels
were 2 to 4 times higher than the limit at which phosphate begins to cause
major problems for the ecosystem.
Other water quality
parameters do not indicate that the iron and phosphate levels I found in the
brook reflect natural occurrences. It seems clear from my data that the
phosphate and iron overloads are being introduced into the brook by human
activity. At one site near the dam at Pierce’s Pond I actually found larges pieces of iron corroding
in the bed of the brook. Phosphate contamination is slightly harder to pin
point, but phosphate and nitrogen are major components in lawn fertilizers
and household detergents. In a way, it is good news that human activity is
part of the problem for the Monoosnoc, because it means that we can all do
something to solve it. Yet many people may be unaware of the innocent
things that we do in the routine care of our homes, gardens and vehicles
have serious consequences for the wildlife and health of the Monoosnoc. Just
by becoming more aware of how our daily activities can affect the brook, we
can help to ensure that the precious ecosystem running literally through
our own backyards stays healthy.
Editor’s Notes:
April graduated from Bradford College with a B.A. in Natural Science
and Mathematics, concentration in Conservation Biology. She is currently
working at the Ipswich River Watershed Association.
A copy of her
study, A
River Runs Through It: A Seasonal Stream Profile of the Monoosnoc Brook
(1998) is available upon request.
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