On June 6, 2007, Allied Biological, completed a vegetation survey of Glen Lake.  The Spring Vegetation Survey was used to get a preliminary look at the growing vegetation in the lake as well as a look at the possible expansion of Eurasian water milfoil.  Basic water quality data was also collected.  Paul Derby, the President of Glen Lake Protective Association, was the contact for the June 6 survey.

          Before starting the survey, Paul Derby provided a little history of the lake and pointed out some areas of concern.  Paul noted several areas of Eurasian water milfoil that have grown substantially since last summer.  Within these areas, the majority of the beds of Eurasian water milfoil were nearing the surface of the water and several were extended out above the water (i.e. topping out).  Lake Association members or lake users have not witnessed these growth conditions of Eurasian water milfoil in recent years.

          The survey began around 10:00am and was completed at 1:30pm.  The survey consisted of maneuvering a boat around the edges of the shoreline while visually assessing the current conditions.  A NYSDEC regulation aquatic rake was used periodically to get a more complete assessment of the vegetation.  The water quality parameters that were taken during the survey are as follows: Dissolved Oxygen/Temperature profile, Total Hardness, Sec chi, pH, and Alkalinity.  Total Phosphorus and Phytoplankton samples were taken and analyzed in a laboratory. 

          The lake was broken down into sections to get a better understanding of the 320-acres of water.  The first section for the survey started at the launch site, which is adjacent to the Docksider Restaurant and continued north along the same shoreline and into Saint Mary’s Cove.  Here the primary vegetation is Chara and Illinois Pondweed.  The Chara gives a favorable blanket over the bottom of the lake, which in turn helps prevent other species from becoming established.  Eurasian water milfoil (milfoil) was present along this shoreline, but at low numbers.  The majority of the milfoil from the launch site to the mouth of Saint Mary’s Cove is around boat docks.  Saint Mary’s Cove has primary plants of Chara, Elodea, and other Pondweeds.  Water lilies, Coontail, and Benthic Filamentous Algae (BFA) were also present.  Along the shorelines, leading out of Saint Mary’s Cove, milfoil is trace to sparse.  However, in the back section of the cove, milfoil is starting to take a stronghold and soon could be out competing the desired vegetation.

          The next section focuses on the shoreline exiting Saint Mary’s Cove and heading northeast toward the mouth of the northern most cove.  Once again, the primary plants include Chara and Illinois Pondweed.  Elodea, Water lilies, and other species of Pondweed were present.  Curly-leaf Pondweed, an invasive species, was observed throughout this section, but not at nuisance densities.  There were areas along the shoreline that had nuisance densities of Floating and Benthic Filamentous Algae.  The milfoil through this section was mostly contained to areas around boat docks at trace to sparse amounts.

          The third section consisted of the entire Northern Cove and a small cove directly across the lake from Osprey Point.  In the Northern Cove, an entire pass of the shoreline was done as well as several passes throughout the middle of the cove.  In the Northern Cove, the primary plants were Clasping-leaf Pondweed, Illinois Pondweed, Elodea, and Chara.  FFA and BFA were medium to dense at certain locations.  Water lilies were present in small densities.  Curly-leaf Pondweed was present throughout most of the cove in small patches, with a few of the patches topping out at the surface.  One area of potential concern is the outlet stream.  The Curly-leaf pondweed was most prevalent at this site.  Eurasian water milfoil was present throughout the cove as well.  In the northeastern part of the cove, there was a medium to dense patch of milfoil and was topping out at the surface.  Along the eastern shoreline, there were small, but numerous patches of milfoil topping out or nearing the surface of the water.  The most dominant patches of milfoil came at the mouth of the Northern Cove.  Just at the mouth, the milfoil is most dense and few of the patches were reaching the waters surface.  Noted by Paul Derby, the milfoil in this area last summer was nowhere near the surface.  The cove directly across the lake from Osprey Point was another area where the milfoil seems to be gaining a stronghold over the native vegetation.  The cove was undoubtedly dominated by Eurasian water milfoil and with several patches topping out at the surface.

          The fourth section focused on the southern portion of the lake.  This area is the inlet portion of Glen Lake and like most lakes has extensive amounts of vegetation due to incoming nutrients.  This area had well established milfoil beds throughout.  Most of the milfoil beds are medium density, but are numerous.  Other primary plants are Illinois Pondweed, Chara, Clasping-leaf Pondweed, and Elodea.  FFA and BFA along with Water lilies were observed in the area. 

          Upon completion of the survey, it is obvious that Eurasian water milfoil is becoming well established in the lake and should be of great concern.  Three areas of Glen Lake have dominant beds of Eurasian water milfoil  These are located at the mouth of the Northern Cove, the cove directly across from Osprey Point, and the area at the southern portion of the lake.  In these three areas, it is projected that the Eurasian water milfoil will be the primary vegetation.  More over, these areas could soon become monothilic stands of Eurasian water milfoil.  Another invasive species of concern would be Curly-leaf Pondweed.  Curly-leaf Pondweed is present throughout most of the littoral zone, but at low to medium densities.  This plant could continue to grow and become denser.  Keeping a watch out for its expansion is important.  There is only one area for potential concern and that is the outlet area in the Northern Cove as noted earlier.

          Attached to the survey is a map showing areas of the lake that contained the significant beds of Eurasian water milfoil.  The red dots indicate areas of primary concern, while the green dots indicate areas of secondary concern.  The dots are not precisely located as in earlier maps that were generated during the 2006 GPS vegetation survey.  Once again, the dots only show areas of primary and secondary concern.  Eurasian water milfoil. was observed along ~70% of Glen Lake’s shoreline as well as in the center portions of the Northern Cove.  A more detailed, geo-referenced plant survey will be performed later this summer.

Steve Wilson
Aquatic Biologist