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Gloeotrichia, a type of blue-green algae, has shown up recently in the
Belgrade Lakes as a variable green blush on the water. Following, Roy Bouchard
of the Maine Department of Environmental Protection (DEP), introduces us to the
problem. DEP, BLA, and Colby College have put their heads together to find out
more about this mysterious little plant.
Gloeotrichia Algae: Great and Long Ponds
by Roy Bouchard
The minute, fuzzy green floating dots that appeared and stayed in many lakes
during the summer are not a new phenomenon. They're called Gloeotrichia
echinulata (glee-oh-trick'-ee-ah e-kin-u-la'-ta). It is a blue-green alga
(really a bacterium) but it is not the type that usually makes a lake 'go green'
as happens in East Pond or over in China Lake . It often appears mid-summer for
a short time, and then disappears. Over the last 4-5 years, however, there have
been more frequent complaints about the density and duration of the growths in
Great and Long Ponds. They have arrived as early as May, and persisted through
August.
No systematic survey of its occurrence is available for Maine . It is known to
be present in a number of lakes in central Maine . In samples from over 70
lakes, mostly in the 1980's, it was not uncommon to find Gloeotrichia. Though
shoreline samples from the time period were occasionally dense, it was usually
not in high densities in the open areas of the lakes proper. Besides Great and
Long Ponds, it is likely in several other Belgrade chain lakes, but we have not
had many reports except for appearance in Messalonske in the summer of 2005.
Gloeotrichia is found all over the northern tier of the US and Canada , as well
as on other continents.
Gloeotrichia does not necessarily indicate poor water quality since it is
commonly present in Maine lakes having good water clarity. Clear water normally
means that there is low phosphorus fertility, so most algae do not grow
prolifically. However, Gloeotrichia over-winters as resting cells on the lake's
bottom, and 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 (see .pdf graphic at Colby).
One of the problems with Gloeotrichia is that it tends to float in the top few
feet of water. Wind-driven currents can concentrate them 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.
Gloeotrichia is not generally a health concern. There are reports in the
literature that it may cause a skin irritation that could be mistaken for
swimmers' itch. Ingesting a lot of it can cause stomach upset. Consultation with
a leading expert in the field (Dr. Wayne Carmichael) and others suggests that
severe toxic effects have not been reported in the literature. While most of us
would not drink lake water anyway, children should be always cautioned not to
swallow water while swimming (and not just because of algae).
What does this appearance of Gloeotrichia mean? Is this a permanent state of
affairs or will it change for the better or worse? Only limited research on the
ecology of Gloeotrichia has been conducted in North America , primarily in the
mid-West and Washington state. The Belgrade Lakes, in collaboration with Colby
College, mounted a comprehensive new study in 2005 which is anticipated to
continue for one or more years. There is not a lot of information on how
persistent this will be or whether it will naturally decline over time, like
many biological populations of plants and other wildlife. What is known is that
Gloeotrichia can move a lot of phosphorus into the lake water from the bottom
sediments that normally would not get there, but there is no indication that it
will lead to worse conditions down the road. One reason for this is that
Gloeotrichia colonies use up their internally-stored phosphorus by dividing and
generating 'daughter' colonies. Even as they do this, older colonies die off and
settle down through the lake to deeper water. They carry some of their
phosphorus with them while some leaks out of the dying colonies. How much of
this escaped phosphorus becomes available to other sorts of algae and how much
just returns to the lake bottom is not known. We do know that this phosphorus
movement (both up and down) can be a significant amount. However, neither Great
nor Long Ponds have shown high algae growth in late summer or fall as a result.
It is also known that there are few direct ways to control this condition.
Great and Long Ponds are just too large and complex for conventional tools such
as aluminum treatments to work. Killing algae with chemicals creates more
environmental problems than it solves, and is illegal to boot.
This condition certainly does indicate that our lake bottoms have enough
nutrients to sustain repeated growths of Gloeotrichia. 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 Gloeotrichia blooms in
the short term, they could help over time and are absolutely needed to avoid
more obnoxious, lake-wide algae blooms in the large lakes of the Belgrade chain.
Contact: Roy Bouchard: (207)287-7798 or (207)287-3901, or fax (207)287-0719.
Address: Maine Dept. Environmental Protection
State House Station 17
Augusta , ME 04333
Email: roy.bouchard@maine.gov LakeSmart Program
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