From an
article posted by the
What are
those tiny floating balls in our lake?
They're
called Gleotrichia (glee-oh-trick-ee-ah). The minute floating dots that
appeared and stayed in many lakes during the summer are not a new phenomenon.
They often appear mid-summer for a short time, then disappear. Over the last
four-five years, however, there have been more frequent complaints about the
density and duration of these growths.
This year, they arrived early, proliferated, and stayed throughout most
of July and August.
Puzzlingly,
Gleotrichia seems to be present only in lakes with good water clarity. Clear
water normally means that there is low phosphorus fertility so most algae do
not grow prolifically. One reason for the high growth of Gleotrichia is that it
over-winters as resting cells on the lake's bottom, then grows its summer
colonies (groups of similar cells bound together) on the sediment surface where
light can reach it. These colonies absorb lots of phosphorus in the process
which is in short supply in the surface water of the lake. When they are well
developed, these algae release from the sediment and float to the surface,
where they multiply their colonies in the light environment.
One of the
problems with Gleotrichia is that it tends to float in the top few feet of
water. Wind-driven currents can concentrate colonies in one part of the lake or
another, and high densities result, especially in coves. As quickly as they
appear in an area, they can diminish, though usually they don't go away
completely until late in the season.
Gleotrichia
is not generally a health concern. There are reports in the literature that it
may cause a skin irritation that could be mistaken for Swimmer's Itch when it
is thick in the water. Ingesting a lot of it can cause stomach upset. While
most of us would not drink lake water anyway, children should always be
cautioned not to swallow water while swimming (and not just because of algae).
What does
Gleotrichia mean? Is this a permanent state of affairs or will it change for
the better or the worse? Most research on Gleotrichia has been conducted in the
mid-West and Washington state. There is not a lot of information on how
persistent it will be or whether it will naturally decline over time like many
biological populations of plants and other wildlife. What is know is that
Gleotrichia can move a lot of phosphorus in the lake water that normally would
not get there, but there is no indication that it will lead to worse conditions
down the road. It is also known that there are few direct ways to control this
condition.
This
condition certainly does indicate that our lake bottoms have enough nutrients
to sustain repeated growths of Gleotrichia. That should prompt us to do
everything we can to prevent phosphorus loading from run-off sites in the
watershed. While such preventative actions may not affect Gleotrichia blooms in
the short term, they could help over time and are absolutely needed to avoid
more obnoxious lake-wide algae blooms in our lakes.