Week of December 12 – 18, 2021
Water Column Clarity
Water clarity was measured at seven locations in the Providence River estuary on December 15, 2021. Less than 0.1 inches of precipitation occurred in the three days prior to sampling. Overall, secchi depth increased by 0.8 meters compared to the previous week. Secchi depth averaged 3.1 meters. The lowest clarity (2.4 meters) was measured at Edgewood Shoal, while the greatest clarity (3.6 meters) was measured at Bullock Reach Buoy. Generally, water clarity increased along a gradient from north to south.
Week of December 12 - 18, 2021
Fixed Site Network
Phillipsdale Landing
Sondes were swapped for routine maintenance on the morning of December 14. Water quality at Phillipsdale Landing was good this week. Minor rainfall was recorded over the course of the week, with daily rain totals less than 0.1 inches on December 12, 15, and 16, and 0.14 inches on December 18, as recorded at TF Green. Blackstone River flows generally increased this week, though remain low compared to historical median levels. Salinity at the surface decreased, averaging 5.2 ppt and ranging 2.0–14.0 ppt. Bottom salinity also declined, averaging 19.2 ppt and ranging 2.6–31.4 ppt. Water temperatures cooled slightly, averaging 6.7°C at the surface and 8.0°C at the bottom. Surface temperatures ranged from 4.5°C to 8.5°C while bottom temperatures ranged from 5.6°C to 9.0°C.
Dissolved oxygen (DO) continues to remain well above the hypoxia threshold of 2.9 mg/L; it is unusual to see hypoxic conditions at this time of year. Surface DO averaged 11.4 mg/L with a minimum of 9.6 mg/L. Bottom DO averaged 9.1 mg/L with a minimum of 7.4 mg/L. Chlorophyll concentrations remained low this week, averaging 1.4 ug/L on the surface and 1.2 ug/L on the bottom, with a surface maximum of 2.1 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
The Bullock Reach sondes were removed for the 2021 monitoring season on November 18.
Week of December 5 - 11, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale Landing was good this week. After a dry week prior, this week included 0.37 inches of rainfall on December 6, 0.2 inches of snow over December 8-9, and 0.17 inches of rain on December 11, as recorded at TF Green. Despite the precipitation, Blackstone River flows remained relatively low and steady all week. Salinity at the surface increased slightly from the previous week, averaging 13.0 ppt and ranging 2.1–26.7 ppt. Bottom salinity declined slightly, averaging 22.0 ppt and ranging 2.2–32.5 ppt. Water temperatures warmed slightly at the surface, averaging 7.1°C, and cooled slightly at the bottom, averaging 8.4°C. Surface temperatures ranged from 4.9°C to 9.2°C while bottom temperatures ranged from 6.9°C to 9.6°C.
Dissolved oxygen (DO) continues to remain well above the hypoxia threshold of 2.9 mg/L; it is unusual to see hypoxic conditions at this time of year. Surface DO averaged 10.2 mg/L with a minimum of 8.2 mg/L. Bottom DO averaged 8.1 mg/L with a minimum of 7.2 mg/L. Chlorophyll concentrations remained low this week, averaging 1.7 ug/L on the surface and 1.5 ug/L on the bottom, with a surface maximum of 4.5 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
The Bullock Reach sondes were removed for the 2021 monitoring season on November 18.
Week of December 5 – 11, 2021
Water Column Clarity
Water clarity was measured at six locations in the Providence and Seekonk River estuaries on December 8, 2021. Two days prior to sampling, 0.37 inches of precipitation was recorded at T.F. Green. Overall, secchi depth averaged 2.3 meters. The lowest clarity (1.2 meters) was measured at Point St. Bridge, while the greatest clarity (2.8 meters) was measured at Conimicut Point. Generally, water clarity increased along a gradient from north to south.
Week of November 28 – December 4, 2021
Nutrients Sampling
Nutrient samples were collected from fourteen local and border river stations and five bay stations (surface and bottom) on December 1, 2021. Bay sampling remains limited due to mechanical problems with NBC’s research vessel, the R/V Monitor. Conditions leading up to the sampling event were relatively dry, with 0.14 inches of precipitation recorded at T.F. Green in the five days prior to sampling.
Among the river stations sampled, the greatest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) occurred at the Ten Mile River at Central Ave. site, with concentrations of 1,950 ppb, 2,020 ppb, and 1,640 ppb, respectively. Lowest TN (599 ppb; average of two duplicates) and TDN (620 ppb; average of two duplicates) occurred at the Moshassuck River at Higginson Ave. station. The lowest DIN value, 266.7 ppb, occurred at Coles River at Milford Rd.
Among the Bay sites, greatest surface nitrogen concentrations occurred at Pawtuxet Cove, where TN was 1,520 ppb, TDN was 1,390 ppb, and DIN was 1,166 ppb. The lowest surface TN, TDN, and DIN values occurred in surface waters of Edgewood Yacht Club, with measured concentrations of 571 ppb, 380 ppb, and 247.5 ppb, respectively. Chlorophyll a concentrations were greater than those measured at the last sampling event, averaging 1.5 µg/L, with a maximum of 2.5 µg/L measured at Edgewood Yacht Club.
Results from nutrient sampling on December 15 and 29, 2021 are pending analysis. The next scheduled date of sampling is January 12, 2022.
