Gleotrichia echinulata, a blue green algae, is present in a number of Maine lakes. In 2002, 2003, and 2004 gleotrichia blooms in some of these lakes have been of longer duration and higher concentrations than previously observed, becoming in some instances the predominant algal form observed in the waterbody. In an effort to broaden understanding of this phenomenon and aid future research planning, this article seeks observations on Gleotrichia echinulata from our readers.


Background: Gleotrichia over-winters in lakes as spores which are attached to the sediments. The spores germinate in springtime, forming colonies which grow steadily in size. Its name derives from Greek for “gelatinous hair” (See title picture). Many of these “hairs”, or trichomes, radiate from a central point. Encased in a gelatinous substance, they form a whitish sphere-like structure. When mature, these colonies (then about pin head size) detach from the sediment and float to the upper layers of the water. Visible then to the naked eye, the colonies look like many tapioca grains dispersed throughout the topmost part of the epilimnion. Slight to moderte blooms are noticeable for a short period of time mid-summer in waters of sufficient depth to obscure the lake bottom.

If blooms are robust and extend over time, Gleotrichia echinulata may be concentrated by wind and water currents on downwind shores — only to be dispersed again when the wind shifts. An extensive bloom, when stacked-up on downwind shores, clouds the water, limiting visibility (See photos). Gleotrichia can become toxic, causing a skin irritation similar to swimmers’ itch and/or a gastro-intestinal upset in swimmers who ingest a quantity of water. As with any algal bloom, it is not recommended that humans or animals drink water dominated by Gleotrichia.

Generally, Gleotrichia in lakes is not an indicator of bad water quality, most often appearing in lakes of good clarity. It is important to note that this algae draws all needed nutrients from the sediments, not the water column. Some biologists theorize that Gleotrichia blooms could become a vehicle for the transfer of phosphorus from bottom sediments into the water column, but there is insufficient data to draw this conclusion at present.

Do you recognize this algae? Does it occur in a lake with which you are familiar? If so, has the incidence or duration of its bloom changed in recent years? If you have any relevant information to add, please e-mail the Maine Lakes Society.

Thank you,

Maggie Shannon, Executive Director, Maine Lakes Society


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