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January 26, 2024 <br />Don Peterson <br />Page 5 of 21 <br />Reference: Water Quality Assessment of Silver View Pond, Mounds View, MN <br />Table 2. Range of concentrations for water quality parameters. <br />Parameter <br />ih <br />Concentration Range <br />(n=2) <br />Eutrophication Standards for Shallow Lakes <br />in North Central Hardwood Forest Ecoregion <br />• .- <br />Nitrite/nitrate <br />Vertical profiles of physicochemical parameters are shown in Table 3. In a small shallow pond like Silver <br />View Pond, we expect well -mixed conditions such that temperature and pH are consistent throughout the <br />water column. Dissolved oxygen (DO) tends to decrease from the surface towards the sediments due to the <br />demand for oxygen during microbially-driven organic matter decomposition and other oxygen -consuming <br />geochemical processes. In early September when the profile data was collected, the pond had extensive <br />coverage of floating aquatic plants such as duckweed and watermeal (discussed in more detail below), <br />which can cut off the oxygen supply from the atmosphere across the air -water interface. Combined with the <br />oxygen demand, DO in Silver View Pond was extremely low. Dissolved oxygen concentrations below 2 <br />mg/L are considered hypoxic and would be detrimental to aquatic organisms that are not tolerant of low DO <br />conditions. <br />Table 3. Phvsicochemical parameters collected at 0.5 m increments in the water column. <br />0 <br />23.88 <br />2.86 <br />7.56 <br />0.5 <br />23.92 <br />2.35 <br />7.55 <br />1 <br />23.81 <br />1.52 <br />7.5 <br />1.5 <br />23.73 <br />0.2 <br />7.31 <br />Aquatic Vegetation Community <br />Silver View Pond is shallow with a mean depth of approximately 6.5 ft. Consequently, the pond is shallow <br />enough to support aquatic vegetation growth across its entire surface area, and indeed the pond <br />experiences significant coverage by aquatic vegetation in the summer growing season. Figure 2 shows the <br />points surveyed in Silver View Pond and conveys the number of individual taxa found at each location. <br />Submerged aquatic vegetation (SAV) metrics from the two surveys are shown in Table 4 and Table 5. The <br />diversity of aquatic plant species in Silver View Pond is relatively high for a small, shallow urban stormwater <br />pond. Shallow ponds and lakes tend to be either macrophyte-dominated or algae -dominated 2. Systems <br />may alternate from one state to another and experience unstable periods that reflect high densities of algae <br />2 Scheffer, Marten. Ecology of Shallow Lakes. The Netherlands: Kluwer Academic Publishers, 2004. <br />Design with community in mind <br />