V3 was contracted by the Wawasee Area Conservancy Foundation (WACF) to update the 2006 Lake Wawasee Aquatic Vegetation Management Plan and include results of vegetation surveys in ecozone areas of Conklin and Johnson Bay. Native species provide many benefits which can be diminished by the presence of exotic aquatic vegetative species. The primary submersed aquatic exotic species at Lake Wawasee are Eurasian watermilfoil (Myriophyllum spicatum), curly leaf pond weed (Potamogeton crispus), and starry stonewort (Nitellopsis obtusa). In addition to disrupting the native vegetative community, exotic species inhibit recreational uses such as swimming, boating and fishing.
Herbicide treatments are an effective management tool for controlling exotic species at Lake Wawasee. Aquatic Weed Control applied liquid 2,4-D (DMA®4 IVM) at a rate of 2.8 gal/A-ft.
to 25 acres of Eurasian watermilfoil on July 20, 2009 and treated an additional 25 acres on August 24, 2009. Aquatic Weed control applied liquid Nautique at a rate of 1.0 ppm to 15
acres of starry stonewort within Johnson Bay on August 31, 2009 (Figure 4). The treatment of starry stonewort was done later in the growth season when the star-shaped bulbils are developed
and allows for positive identification. V3 conducted the summer Tier II survey on August 12, 2009 to evaluate the vegetative community and determine the extent of exotic species in Lake Wawasee. The 2009 summer sampling effort had vegetation at 78 of the 100 sampling locations and collected a total of 16 species. The two exotic species collected were Eurasian watermilfoil and curlyleaf pondweed. Chara was the most frequently occurring species within Lake Wawasee (39%). Eurasian watermilfoil was present at 33% of sampling locations and collected from depths ranging from 4 to 23 feet during the 2009 Tier II survey. Curlyleaf pondweed was collected at one sampling location from a depth of 16 feet during the 2009 Tier II survey. Starry stonewort was collected at 4 sampling locations in Johnson Bay with a rake score frequency of 3 (20-100% rake teeth filled). Starry stonewort was collected from depths ranging from 3 to 5 feet (Figure 15).
In addition to the Tier II vegetation survey, V3 conducted ecozone surveys in Johnson Bay, Conklin Bay and North Bay. The ecozone survey of Johnson Bay was conducted on August 10, 2009.
Ecozone areas of Conklin Bay and North Bay were surveyed on August 11, 2009. The most common floating-leaf emergent species within Johnson and Conklin Bay are yellow pond lily
(Nuphar variegate) and white water lily (Nymphaea oderata). Fifteen emergent beds were mapped within Johnson Bay’s shoreline, which ranged from 0.01 – 2.74 acres in size and totaled
9.75 acres (Figure 13). The 2009 emergent survey results indicate that the buoys within Johnson Bay are protecting the ecozone areas, as emergent beds increased by 1 acre from 2008 to
2009. V3 mapped 9 beds along the shoreline of Conklin Bay. Conklin Bay’s emergent beds ranged from 0.09 – 3.44 acres in size and totaled 8.9 acres (Figure 14). Conklin Bay’s emergent
beds have increased by 0.93 acres since the 2008 emergent survey. Hardstem bulrush (Scirpus acutus), floating pondweed (Potamogeton natans) and white water lily composed the three
emergent clumps in North Bay in 2008 and 2009. North Bay’s clumps 1 and 3 expanded in 2009 and clump 2 decreased in size by 0.02 acres (Figure 17).
Eurasian watermilfoil has shown a steady increase in frequency from 2005 to 2009 (12.8% and 33% respectively) which substantiates the need for treatment in 2010. The 2005 survey effort
included more sampling locations in the shallow zones of Lake Wawasee which could have resulted in an underestimate of Eurasian watermilfoil’s abundance as it can thrive in deeper depth
zones. Locations where starry stonewort was retrieved in 2009 remained consistent with the locations starry stonewort was collected in 2008.