July 2023
Phillipsdale Landing
The Phillipsdale Landing sondes have been deployed since May 9th, 2023 utilizing a new setup allowing staff access to the equipment from the boat instead of standing on the dock. Sondes were changed out for routine maintenance on July 6th and July 18th. July was a wet month, with 8.37 inches of precipitation recorded at T.F. Green. The largest storm occurred on July 16th (3.35 inches). Blackstone River flows were elevated due to the frequent precipitation throughout the month of July. Salinity at Phillipsdale averaged 4.3 ppt at the surface (range 0.2 – 18.8 ppt) and 42.0 ppt at the bottom (range -0.6 – 108.9 ppt). Temperatures increased from June, averaging 25.4°C at the surface and 24.0°C at the bottom. Surface temperatures ranged 22.6 – 30.0°C, while bottom temperatures ranged 21.0 – 26.7°C.
The surface dissolved oxygen (DO) concentrations remained mostly above the hypoxia threshold (2.9 mg/L), only briefly dropping below the threshold for a half hour the morning of July 10th. The bottom waters were hypoxic periodically throughout the month. The longest sustained period of hypoxic conditions (~1.5 days) occurring from the morning of July 9th until the night of July 10th. DO averaged 7.3 mg/L at the surface with a minimum of 2.2 mg/L, while bottom waters averaged 3.3 mg/L with a minimum of -0.1 mg/L.
Chlorophyll readings were generally low with periods of moderately elevated chlorophyll intermittently through the month, suggestive of moderate phytoplankton blooms. The surface and bottom readings averaged 8.3µg/L and 8.6 µg/L, respectively. The maximum surface reading of 112.8 µg/L occurred on July 9th and the maximum bottom reading of 130.9 µg/L occurred on July 22nd. Please note that data from the bottom sonde between July 23rd and the 29th was excluded due to mud compromising the results. Also, gaps occurred in the bottom on July 4th to the 6th potentially due to equipment failure.
Bullock Reach
The Bullock Reach buoy was deployed June 1st for the 2023 season. Sondes were changed out for routine maintenance on July 11th and 25th. Overall, water quality was fair at Bullock Reach Buoy throughout the month of July 2023. Surface, middle, and bottom DO averaged 7.5 mg/L, 4.8 mg/L, and 2.6 mg/L, respectively. Hypoxic conditions were not observed at the surface. However, hypoxic conditions occurred sporadically in middle waters beginning July 19th. Bottom waters periodically fell below the hypoxia threshold (2.9 mg/L) throughout the month and the longest duration of hypoxic conditions occurred for 5.5 days between the 22nd and the 28th.
Surface salinity at Bullock Reach ranged 9.5 – 27.2 ppt and averaged 21.1 ppt. Mid-depth salinity ranged 16.4 – 30.0 ppt and averaged 25.7 ppt. Bottom salinity ranged 23.5 – 31.3 ppt and averaged 30.1 ppt. Water column temperatures averaged 25.7°C, 25.1°C, and 22.1°C at the surface, middle, and bottom, respectively. Temperatures ranged 23.2°C – 28.6°C at the surface, 21.6°C – 27.4°C at mid-depth, and 19.4°C – 25.7°C at the bottom.
Chlorophyll readings were moderately elevated, averaging 25.7 µg/L at the surface, 15.0 µg/L at mid-depth, and 2.8 µg/L at the bottom. Periods of elevated chlorophyll occurred around July 6th – 10th. The maximum surface reading of 81.2 µg/L occurred on July 22nd. Please note that minor data gaps occurred between the 8th to the 25th on the surface and bottom due to potential equipment failure and fouling.
Please note that the data exclusions mentioned in the above text for Phillipsdale Landing and Bullock Reach does not affect the raw data, and any exclusions occurred during a QC process, prior to the average, maximum, and minimum calculations discussed.
