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Other Fishing Articles:
Cleaning Fish
Mr. Pike
Keeper of the Keys
Loons on the Lake
An Open Letter
In a Hurry?
Algae
Knots
Lake Turnover
Mayflies
Ticks
Finest of Times
Ice Fishing
Knives
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 Not long ago, I read
an article about algae that was adapted from a book called Lake Watch:
A Guide to the Care of the
Yahara Lakes, written by
several distinguished authors from the University of Wisconsin. I thought
I would share with you some of the information gleaned from that article.
My first question for
you is whether or not the word algae is singular or plural… or perhaps
both? I always thought it was singular; the article I read indicates
plural. But the answer is perhaps not as important as the function that
these little critters serve. Even though they are responsible for making
swimming in your favorite lake a little difficult – simply because of the
distinct green color and tiny floating green things in the water – the
lake would not be a very happy place without them. And for the fisherman
in all of us, know that the “lowly” algae are very important. They are at
the very base of the aquatic food chain. Without them, there would be no
fish! By the way, algae are primitive plants.
There are literally
hundreds of species of the culprits in question – the ones found floating
and suspended in the water. They are called phytoplankton and they
definitely affect the clarity of the water. Obviously, throughout the
year, conditions change on any lake. Seasonal changes bring corresponding
changes in the air and water temperature, amount of light and nutrients to
the lake. The changes favor various species of algae at various times,
which, as they become abundant, affect not only the clarity of the water
but the color as well.
The algae swim about
(plants that swim!) by means of long, hair-like appendages called
flagella. Only a small number survive in the winter months, swimming just
beneath the ice and capturing the weak sunlight that is able to
penetrate. The water in the lake is very clear at this point. As the
days lengthen in the springtime, the ice melts. But other changes are
afoot: spring storms stir the waters again, bringing from the bottom of
the lake the spores of another species of algae, the diatoms. These
long-dormant organisms come to life in the light of the nutrient-rich
waters and begin to reproduce. The diatoms are extremely tiny yet ornate;
a spring “bloom” of them can turn the lake water brown in a matter of only
a few days. The water color is due to a pigment that makes the diatoms
appear brown in the same manner that chlorophyll makes the leaves on a
tree green.
In the calmer days of
early to mid-summer, the diatoms produce the spores that once again settle
to the lake bottom. The diatoms’ decline makes way for the green algae.
Green phytoplankton don’t really get a chance to dominate the scene, since
they make a great meal for another species of microscopic animal called
Daphnia. By now – midsummer – the species referred to as blue-green algae
get the upper hand. They thrive in warm, still water because many of them
can manufacture the nitrogen that they need right from the atmosphere.
They can also reproduce at a phenomenal rate… often turning your favorite
swimming hole into an ominous pea soup-looking mess in short order. The
blue-greens don’t sink out of sight like the diatoms and are not the
favorite meal of many species – like the Daphnia, so will tend to hang
around for most of the rest of the summer. Worse, as they die and decay,
they can be blown to shore to create a stinky and unsightly scum. But
there is some very good news in all of this. The decay of these organisms
releases needed nutrients back into the water. And, as the summer heat
yields to the onset of the cooler temperatures of the fall, the cooler
waters also cause the majority of the blue-green population, as well as
the shore scum, to disappear. The lake “turning over” is simply the winds
of autumn recalling the diatoms from the depths. The warm and oxygen
depleted waters near the surface are replaced with the nutrients from
below while the storms and wind can whip life-giving oxygen into the waves
once again, and the cycle of life is ready to begin anew. We take many
things in the waters for granted, but some of the most important processes
are undertaken by organisms too small to be seen or appreciated.
As always, I hope to
see you On
the Lake!
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