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By Betsy Lydick
Daily News Correspondent
Ludington Daily News
Spring is here and area residents are
applying fertilizer to ensure a healthy green lawn, but homeowners need to
be careful when selecting fertilizer if they want to keep area waterways
healthy.
Biologists say there is a
connection between excessive or inappropriate fertilization and weedy lakes.
Fertilizer is one of the many
contributing factors to abundant aquatic plant life. Other factors are lawn
runoff, farmland runoff, streambank erosion, decomposing organic matter and
improperly maintained septic systems, according to Dr. Hamdy Helal, an
expert in the field of lake biology.
Limiting the use of
phosphorous-containing fertilizers decreases the likelihood that heavy
rains will transport phosphorous to inland lakes or rivers.
Curt VanderWall of Turf Care Lawn
Services agrees about the potential for water quality problems when using
fertilizers.
“Runoff from fertilizers containing
phosphorous are a contributing factor to excessive aquatic plant growth in
inland lakes and rivers,” VanderWall said. “Phosphorous applied to lawns on
or near any body of water or watershed area can wash into lakes and
stimulate unwanted aquatic plant growth. It is very important that
homeowners do not apply phosphorous to their lawns unless it is absolutely
necessary.
“Random soil tests throughout the area
have shown that Mother Nature has provided enough phosphorous. Established
lawns don’t usually need it, so phosphorous is not a part of our fertilizer
mix,” said VanderWall.
Most commercially available fertilizer
contains phosphorous, according to VanderWall.
“We had to custom formulate our
fertilizer to be phosphorous free.”
When phosphorous is introduced into a
lake it can generate several hundred times its weight in aquatic plants.
Most aquatic plants are a normal and
beneficial part of the lake’s ecosystem. Directly or indirectly, aquatic
plants provide shelter and food for fish and waterfowl that are part of the
aquatic ecosystem. Aquatic plants produce oxygen and reduce shoreline
erosion by reducing the impact of wind and wave action.
Overabundant aquatic plants can also
interfere with lake recreation.
“In the last two or three years I have
had a lot of customers complaining about all of the floating weeds,” said
Dave Mahannah of the North Bayou Resort and Marina on Hamlin Lake.
Even though an overabundance of weeds is
a nuisance for lake users, not all weeds by definition are considered an
aquatic nuisance. The State of Michigan defines an aquatic nuisance species
as a waterborne, non-native and invasive organism that threatens the
diversity or abundance of native species, the ecological stability of
impacted waters, or threatens commercial, agricultural, aquacultural or
recreational activity.
The spread of invasive species —
including aquatic nuisance species — is the fastest growing threat to
biodiversity.
“Once introduced, aquatic nuisance
species can forever alter the infested lake,” said Helal, director
Aquaculture and Natural Resources Institute at West Shore Community
College.
Eurasian watermilfoil is an ANS and has
been widely documented throughout Michigan. Eurasian watermilfoil forms a
dense mat of vegetation, or canopy, at the water’s surface. “The canopy
shades and destroys desirable plant species that provide habitat for fish
and other aquatic organisms,” Helal said.
The presence of Eurasian watermilfoil
has been documented in area lakes.
“It is important to note that the
discovery of Eurasian milfoil in Hamlin Lake is very recent,” Helal said.
“We knew that it was in other lakes; the summer of 2003 is the first
documentation in Hamlin Lake.”
The species Eurasian watermilfoil is
difficult to differentiate from other native aquatic plants. Eurasian
watermilfoil has slender stems and feathery leaves. “It is almost
indistinguishable from native milfoil and many other non-invasive species
of aquatic vegetation,” Helal said.
Chemical treatment of Eurasian milfoil
is expensive and provides temporary relief. Residents of Hamlin Lake’s
Middle Bayou chemically treated the overabundance of aquatic vegetation
with herbicides in the summer of 2003.
Helal examined plant samples from the
Middle Bayou after the chemical application and found evidence of Eurasian
watermilfoil. “Temporarily destroying some of the Eurasian milfoil may have
destroyed beneficial aquatic vegetation and probably enhanced the Eurasian
milfoil population,” Helal said.
Harvesting Eurasian watermilfoil
mechanically would likely increase the population of Eurasian watermilfoil,
according to Dr. Helal. Eurasian watermilfoil propagates through broken
fragments. New colonies of Eurasian watermilfoil emerge when small pieces
are broken off through harvesting or boat movement.
“Boating may be a contributing factor to
the spread of weeds,” Mahannah said. “Weeds are in deeper water than they
used to be (because of the effect of zebra mussels) and the boat props are
cutting up the weeds. Then, the wind carries the weeds that are floating around
on the surface and they grow somewhere else on the lake.”
“There are many factors that contribute
to an abundance of plants,” Helal said. “Chemical treatment produces more
nutrients for the plants because the plants that have been destroyed sink
to the bottom. The solution depends upon the type of plant (that is causing
the problem),” said Helal said.
Helal has studied the results of various
techniques used to control Eurasian watermilfoil. One technique he has
observed is the introduction of milfoil weevils into the aquatic
environment. Milfoil weevil larvae feed on Eurasian watermilfoil stems and
leaves, ultimately killing the plant. When the Eurasian watermilfoil
population is destroyed, the weevils lack nourishment and die.
In October 2001, Helal prepared a report
about the impact of milfoil weevils on the Eurasian watermilfoil population
in Pentwater Lake. Ten thousand milfoil weevil larvae were introduced into
Pentwater Lake and marsh during the summer of 1999. After the milfoil
weevils were established, Helal said, “there was a sharp decline in the
nuisance Eurasian milfoil population.”
Hamlin Township has contracted with
Progressive Engineering to conduct an aquatic vegetation survey of Hamlin
Lake. The results of the survey will identify the location of significant
beds of Eurasian watermilfoil and will provide computer-generated maps
indicating the distribution of aquatic vegetation. Based on the findings of
the aquatic vegetation study, Progressive Engineering will prepare its
recommendations including a discussion of plant control alternatives.
Helal believes that milfoil weevils are
a viable option to reduce the Eurasian watermilfoil population in Hamlin
Lake. “The Middle Bayou of Hamlin Lake would be an excellent habitat for
the milfoil weevil larvae,” Helal said.
“Approximately 740,000 people visit the
Ludington State Park annually,” stated Mike Mullen, park manager of the
Ludington State Park. “Most visitors at the State Park also enjoy spending
time at Hamlin Lake.”
“Overall, people do a very good job of
being natural resource managers,” said Mullen. “Following a few simple
guidelines can help protect the natural beauty of a very valuable
resource.”
Invasive species, such as Eurasian
milfoil, have the potential to destroy a priceless resource. “Lakes, such
as Hamlin Lake, belong to everyone,” said Kent Gage, president of the
Hamlin Lake Preservation Society. “Part-time or occasional lake use can
have long term consequences. We all need to take a few extra steps, such as
using fertilizers that do not contain phosphorous, to protect our lakes for
future generations.”
blydick@ludingtondailynews.com
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