Phillipsdale Landing
Overall, the water quality at Phillipsdale Landing was fair this week. Weather conditions included trace amounts of rain this week, recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week. Surface salinity averaged 19.5 ppt and ranged from 9.2 ppt to 25.4 ppt. At the bottom, salinity averaged 24.2 ppt and ranged from 10.4 ppt to 29.0 ppt. Surface temperature decreased this week, averaging 24.9°C at the surface and ranging 22.7°C – 29.0°C. The bottom temperature increased this week, averaging 24.3°C and ranged 22.4°C – 25.9°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 21.0 hours, occurring at the bottom depth from the afternoon of July 21st until July 22nd. During this period, the bottom DO averaged around 1.68 mg/L. Surface DO averaged 6.2 mg/L and ranged from 0.8 mg/L to 15.4 mg/L. Bottom DO concentrations averaged 3.4 mg/L and ranged from 0.3 mg/L to 12.0 mg/L. Chlorophyll readings decreased from last week, averaging 30.7 µg/L at the surface and 20.8 µg/L at the bottom. Maximum chlorophyll at the surface reached 236.9 µg/L on the afternoon of July 25th. 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 July 22nd. Overall, water quality was fair to good at Bullock Reach this week. Salinity averaged 27.2 ppt, 28.9 ppt, and 30.6 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 24.4– 29.2 ppt, mid salinity ranged 26.5 – 30.1 ppt, and bottom salinity ranged 29.1 – 32.0 ppt. Surface temperature averaged 24.5°C and ranged from 23.2°C to 25.9°C. Mid temperatures averaged 24.3°C and ranged from 23.3°C to 25.4°C. Bottom temperatures averaged 22.8°C and ranged from 20.9°C to 24.4°C.
Dissolved oxygen (DO) at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface and middle depths throughout the week, while DO at the bottom waters dropped below the hypoxic threshold at the start of the week. Surface DO averaged 7.2 mg/L and ranged 5.2– 10.4 mg/L. In the mid waters, DO averaged 6.2 mg/L and ranged 3.8 – 8.0 mg/L. At the bottom, DO averaged 4.3 mg/L and ranged 2.0 – 6.7 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 13.0 µg/L at the surface, 15.8 µg/L at mid-depth, and 9.1 µg/L at the bottom. The maximum chlorophyll of 31.9 µg/L was on the bottom on the morning of July 24th.