8984-R2_NewGloucester_2023-2024_AnnualReport_Web

2024 Sabbathday Lake Water Quality Report Table 1. Average annual water clarity for Sabbathday Lake at Station 1 (1975-2024). Water clarity in Maine lakes ranges from 0.2 m to 21.3 m with a statewide average of 5.3 m. Transparency readings of 2 m or less generally indicate an algal bloom. The 2024 annual average water clarity was 7.3 m, 0.6 m clearer than the historical average (Table 1.) The lowest annual average water clarity over the historical sampling period (since 1975) is 5.5 m (1989) and the highest annual average water clarity was 8.1 m (2022). The historical average water clarity for Sabbathday Lake is 6.7 m. 2 Long-term annual average water clarity has remained steady (Figure 3 & 4) or improved slightly, with an average SDT over the first 10 years of continuous sampling (1986-1995) of 6.5 m, vs. an average SDT over the last 10 years (2015-2024) of 7.1 m. Water Clarity Years Annual SDT (m) Mean Min Max 2024 Sabbathday Lake 7.3 6.7 7.8 Historical Average (1975-2024) 6.7 5.5 8.0 10-Year Average (2015-2024) 7.2 5.8 8.0 Avg. Maine Lakes 5.3 0.2 21.3

Average Annual Water Clarity Sabbathday Lake (1975-2024)

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Figure 3. Average annual water clarity for Sabbathday Lake, Station 1 (1975-2024). Data from MDEP, VLMP/LSM, and Ecological Instincts.

Total Phosphorus Total phosphorus (TP) is the concentration of phosphorus found in the water, including organic and inorganic forms. TP is one of the major nutrients for plant growth. It is generally present in small amounts and limits plant growth in freshwater ecosystems. As phosphorus increases, the amount of

2 Annual averages for SDT are from Lakes of Maine through Maine DEP (1975-2022), and data collected by Ecological Instincts in 2023 and 2024.

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