Results

At each point, ARC scientists: • estimated percent cover of all plants as measured by the areal extent of plants within an approximate two square meter visual area. • estimated percent biovolume as measured by the height of the water column occupied by plants within the two square meter area. Cover and biovolume are estimated using a semiquantitative (0-4) ranking system as follows:

Rank Percent Cover or Biovolume 0 0% 1 1-25% 2 26-50% 3 51-75% 4 76-100%

• identified plants to the species level or to genus level for those that were not readily identifiable in the field. • estimated the density of all species present using categories of: Trace, Sparse,

Moderate and Dense. • used a rake toss to verify the visual identification of plants and density observed with the Aqua-Vu®.

ARC utilized QGIS software to produce maps depicting tapegrass and EWM densities. Note: there are inherent error/precision limitations associated with biological surveys and data are an estimation of conditions at the time of the survey.

Table 1 provides a listing of data collected at each observation point. Plant cover was greater than 50% (cover ranks 3 & 4) at the 33 observation points. Biovolume, a representation of the portion of the water column occupied by plants, was high with 39% of the observation locations exhibiting more than half of the water depth occupied by plants. Most of the observation points had plants occupying 26-50% of the water column (rank 2). Six percent of the observation locations had plants topping out at the surface. In comparison to the 2020 survey, plant biovolume was less; 39% (13 of 33 locations) of the 2021 observation locations showed a bio-volume decrease over 2020 (Table 2). This is likely the result of harvesting activities lessening the extent of plant growth reaching the surface.

Plant species richness (number of species encountered) contained three different species. Filamentous green algae, slender naiad (Najas flexilis), and tapegrass were the most commonly encounters species. Filamentous green algae and EWM were more frequently encountered this year than during the September 2020 survey. When present, tapegrass was typically dense (79% of locations Figure 2). Slender naiad and tapegrass were commonly encountered together. Filamentous green algae were also widely distributed and present at 82% of the observation locations. EWM was encountered at seven locations (Figure 2). Specific changes in EWM and tapegrass density is shown in Table 3.