Filamentous Algae

Many are asking questions about our current algae blooms...ILM ( was here Thursday  June 1st and sprayed the algae.  They are visiting weekly and will return June 8th to treat our lakes again. 

As for ideas as to what is going on...  my unprofessional thoughts are the following:  

The unusual winter set us up for problems.  That followed by some nice spring days when landscaping activities were triggered with spring lawn cutting and fertilization followed then by lots of rain exacerbated the problem.  Our lakes are storm water retention ponds and all the fertilizer and lawn clipping blown in to the lake and street from blocks around by residents wind up in our lakes.  Nutrients turn lawns green and so they do when they wash into the lakes.  The debris that washes in to our lakes also results in an increase in oxygen demand as the decay process begins.  Then the recent warm weather has rapidly increased the water temperature creating the algae blooms.  The algae because of photosynthesis do oxygen and carbon dioxide gas exchange creating bubbles in the algae and up it comes.  It is currently 78 degrees under my dock and things are a mess along my shoreline and on most lakes in the county.  Add to that the fact that the applicators told me on Thursday that the DO (dissolved oxygen) for my lake was 6.0 mg/l.  That is low.  It is usually 10 to 12 mg/l or higher.  Hot water degases and looses oxygen for the same reason soda goes flat.  That is hard on the fish population.  Herbicide applicators test the DO and can not add more herbicide when the number is 5.8 mg/l or below.  If they "kill" more vegetation it will sink to the bottom and the decay process increases the BOD (biological oxygen demand) which then lowers the DO to "anoxic" conditions resulting in a fish kill. 

Hopefully the continued winds will help to break up the algae mats and send them to the bottom.  Of course the wind favors some residents (and beaches) at the expense of others.  I've got algae along my shoreline for the last I have to live with the problem as well.  Admittedly it is not as bad as Lake Linden right now, but we take our turn from time to time as well.

As for the safely and accessibility of the Lake Linden beaches for swimming, that is a question for our Lindenhurs Parks District. 

Concerned residents are always welcome at our meetings and currently there are commissioner positions available.


On Thursday June 8th ILM again treated our lakes.  The DO had increased sufficiently (Waterford ~ 8 mg/l; Linden ~7.5 mg/l) to allow additional herbicide application.  The surface algae was treated along with areas of underwater macrophyte growth that is nearing or has reached the surface.  The algae was treated all around the lakes.  You can tell treatment because the algae will turn brown.  We need some rain or wind and hopefully both to break up and sink the surface algae.  Algae treatment does not require any health hazard posting.  Some other herbicides require posting of health hazard for human and/or pets for various short periods of time.  Those restrictions appear at the location here ILM launched their watercraft. 


Below are old photos which are examples of the filamentous algae we are now experiencing.  This in NOT blue-green algae what we sometimes get in the summer, which can be toxic.  For more on blue-green algae see below.

Click any picture below to enlarge

Springledge 03/15/12

Potomac 03/17/12


Filamentous Algae (Spirogyra, etc.) are long visible chains of single algae cells that form threads or filaments.  The algae grows on the bottom of our lakes in shallow water attaching itself to chara (another form of algae), branches, rocks, docks and bottom debris.    As the water warms unsightly mats float on or near the surface of our lakes as a thick green pond scum.

Filamentous algae is a phytophankton that grows prolifically because of the high nutrient load in our lakes.  The water level o four lakes is maintained only by rain water run-off.  We have no springs or streams inflows.  The storm water run-off from all of the yards, streets, sidewalks and driveways goes into our lakes carrying with it all grass clippings, leaves and excess fertilizer this is not absorbed by our lawns or buffer strips.  Since the majority of commercial fertilizers contain phosphate our lakes are inundated with excessive nutrients. 

Read more on the impact of Phosphorus in Lake County 

Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates (i.e. bugs, worms, etc.). These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food for many aquatic invertebrates. However, filamentous algae has no known direct food value to wildlife.

McCloud Aquatic Services treats our lakes as needed with an algaecide called copper sulfate.  It is effective in killing the algae and you will see the mats turn brown after being treated.  Copper sulfate if toxic to the lake and accumulates in the bottom mud and muck.  Eventually one time it builds up to harmful levels to the inhabitants of the lake. 

ALL OUR RESIDENTS need to realize that they live in our watershed and that what they do in and around their property directly impacts our lakes causing the algae blooms and the resulting use of chemical to control it.  If all or us would become more environmentally conscious and either stop the use of fertilizer or at a minimum purchase phosphate-free fertilizer it would reduce both the blooms of algae and need for toxic chemicals to treat it.

Phosphorus in Lake County

Blue-green Algae