Phillipsdale Landing
Overall, water quality at Phillipsdale Landing was fair to poor this week. Weather conditions included sporadic rain events, with 1.18 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated through the week in response to rain. Surface salinity averaged 16.3 ppt and ranged from 7.0 ppt to 23.5 ppt. At the bottom, salinity averaged 25.0 ppt and ranged from 14.9 ppt to 28.5 ppt. Temperatures continued to increase this week, averaging 24.4°C at the surface and ranging 22.5°C – 26.7°C. At the bottom, temperatures averaged 23.4°C and ranged 22.2°C – 24.8°C.
Dissolved oxygen (DO) at Phillipsdale Landing dropped below the hypoxia threshold (i.e., DO >2.9 mg/L) over the week. Surface DO average 8.3 mg/L and ranged from 2.0 mg/L to 21.8 mg/L. Bottom DO concentrations averaged 1.7 mg/L and ranged from 0.5 mg/L to 6.2 mg/L. The longest period of hypoxic conditions (1 day, 12 hours and 15 minutes) occurred at the bottom depth between the night of August 13th to the morning of August 15th. During this period, bottom DO averaged around 0.86 mg/L. Chlorophyll readings increased from last week, averaging 51.1 µg/L at the surface and 25.6 µg/L at the bottom. Maximum chlorophyll at the surface reached 219.8 µg/L on the afternoon of August 12th. 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 August 15th. Overall, the water quality was good to fair at Bullock Reach this week. Salinity averaged 26.3 ppt, 28.7 ppt, and 30.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 22.8 – 25.3 ppt, mid salinity ranged 21.8 – 24.8 ppt, and bottom salinity ranged 20.3 – 23.1 ppt. Surface temperature averaged 24.1°C and ranged from 22.8°C to 25.3°C. Mid temperatures averaged 23.1°C and ranged from 21.8°C to 24.8°C. Bottom temperatures averaged 21.4°C and ranged from 20.3°C to 23.1°C.
DO at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface. Middle and Bottom DO dropped below the hypoxia threshold sporadically throughout the week. Surface DO averaged 8.7 mg/L and ranged 5.6 – 13.7 mg/L. In the mid waters, DO averaged 4.6 mg/L and ranged 2.1 – 9.0 mg/L. At the bottom, DO averaged 3.0 mg/L and ranged 1.8 – 5.1 mg/L. The longest period of hypoxic conditions (1 day, 10 hours, and 45 minutes) occurred at the bottom depth during the night of August 16th until the morning of August 18th. During this period, bottom DO averaged around 2.29 mg/L. Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 20.1 µg/L at the surface, 13.4 µg/L at mid-depth, and 4.1 µg/L at the bottom. The maximum surface chlorophyll was 54.5 µg/L on the afternoon of August 13th.