Phillipsdale Landing
Sondes were swapped this week on the morning of August 26th. Overall, the water quality at Phillipsdale Landing was fair this week. Weather conditions were wet, with 0.86 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week. Surface salinity averaged 20.0 ppt and ranged from 0.0 ppt to 25.6 ppt. At the bottom, salinity averaged 25.9 ppt and ranged from 20.6 ppt to 29.6 ppt. Temperatures averaged 22.8°C at the surface and 23.0°C at the bottom. Surface temperatures ranged from 12.5°C to 25.0°C, while bottom temperatures ranged from 22.1°C to 24.6°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 9.5 hours, occurring at the bottom depth on the night of August 30th into August 31st. During this period, the bottom DO averaged around 1.81 mg/L. Surface DO averaged 9.5 mg/L and ranged from 2.8 mg/L to 19.9 mg/L. Bottom DO concentrations averaged 4.7 mg/L and ranged from 0.4 mg/L to 14.8 mg/L. Chlorophyll readings increased from last week, averaging 41.1 µg/L at the surface and 38.5 µg/L at the bottom. Maximum chlorophyll at the surface reached 437.8 µg/L on the morning of August 26th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Overall, water quality was good to fair at Bullock Reach this week. Salinity averaged 29.1 ppt, 30.7 ppt, and 30.3 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 27.6– 30.2 ppt, middle salinity ranged 29.2 -31.9 ppt, and bottom salinity ranged 31.0 – 32.7 ppt. Surface temperature averaged 22.5°C and ranged from 21.2°C to 23.9C. Middle temperature averaged 22.2°C, and ranged from 21.2°C to 23.4°C. Bottom temperatures averaged 21.9°C and ranged from 21.2°C to 22.7°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 7.6 mg/L, and ranged 5.7 – 9.8 mg/L. Middle DO averaged 6.5 mg/L, and ranged 4.8 – 8.3 mg/L. At the bottom, DO averaged 5.7 mg/L and ranged 4.6 – 7.2 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 9.1 µg/L at the surface, 11.2 µg/L at the middle, and 7.8 µg/L at the bottom. The maximum surface chlorophyll was 18.29 µg/L on the afternoon of August 30th.