Phillipsdale Landing
Overall, the water quality at Phillipsdale Landing was fair this week. Weather conditions were wet this week, with 0.32 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week, while remaining below the 20-year daily median. Surface salinity averaged 23.7 ppt and ranged from 17.8 ppt to 27.3 ppt. At the bottom, salinity averaged 26.7 ppt and ranged from 22.6 ppt to 28.7 ppt. Temperatures averaged 21.9°C at the surface and 21.8°C at the bottom. Surface temperatures ranged from 19.6°C to 23.7°C, while bottom temperatures ranged from 21.3°C to 22.8°C.
Dissolved oxygen (DO) at Phillipsdale Landing dropped below the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. The longest periods of hypoxic conditions spanned 3.5 hours, occurring at the bottom depth from the morning of September 19th. During this period, the bottom DO averaged around 2.57 mg/L. Surface DO averaged 5.9 mg/L and ranged from 2.8 mg/L to 14.1 mg/L. Bottom DO concentrations averaged 3.8 mg/L and ranged from 2.3 mg/L to 7.0 mg/L. Chlorophyll readings decreased from last week, averaging 9.7 µg/L at the surface and 3.1 µg/L at the bottom. Maximum chlorophyll at the surface reached 55.7 µg/L on the afternoon of September 15th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Sondes were swapped this week on the morning of September 16th. Overall, water quality was good at Bullock Reach this week. Salinity averaged 28.8 ppt, 31.2ppt, and 32.4 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 27.2– 30.3 ppt, mid salinity ranged 28.9 – 32.9 ppt, and bottom salinity ranged 30.8 – 33.1 ppt. Surface temperature averaged 21.4°C and ranged from 20.1°C to 22.9°C. Mid temperatures averaged 21.3°C and ranged from 20.4°C to 22.3°C. Bottom temperatures averaged 21.0C and ranged from 20.7°C to 21.3°C.
Dissolved oxygen (DO) at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. Surface DO averaged 7.8 mg/L and ranged 6.0 – 10.6 mg/L. In the mid waters, DO averaged 6.6 mg/L and ranged 4.4 – 9.7 mg/L. At the bottom, DO averaged 5.3 mg/L and ranged 4.3 – 6.5 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 9.5 µg/L at the surface, 15.0 µg/L at mid-depth, and 7.5 µg/L at the bottom. The maximum surface chlorophyll was 66.0 µg/L on the morning of September 17th.