Week of July 4 - 10, 2021
Water Column Profiles
Water column profiles were conducted at eight locations in the Providence and Seekonk Rivers using a Seabird profiling instrument on July 7, 2021. Conditions leading up to the survey were relatively wet, with 1.75 inches of rainfall recorded at T.F. Green over the five days prior. Evidence of density stratification was observed at almost all sites.
Surface salinities this week ranged from 2 psu at Phillipsdale Landing to 24 psu at Pomham Rocks and Edgewood Yacht Club. Bottom salinities ranged from 22 psu at Phillipsdale Landing to 31 psu at Conimicut Point. The highest temperatures were observed at Point St. Bridge, where surface waters reached 23°C and bottom waters were slightly cooler at 21°C. Edgewood Yacht Club and Pomham Rocks had the coolest surface waters at 21°C while the coolest bottom temperatures (18°C) were observed at Conimicut Point.
Dissolved oxygen (DO) concentrations were variable this week. Hypoxic conditions (e.g., DO <2.9 mg/L) were observed in the bottom waters of Edgewood Yacht Club, where DO below 3 m averaged 1.3 mg/L. Among the other sites, DO ranged from 3.1 mg/L to 9.3 mg/L. The highest DO concentrations were associated with relatively high fluorescence values in the sub-surface waters at Bullock Reach and Conimicut Point. Please note that due to a quality control issue, numerical fluorescence data are not posted at this time.
Week of September 19 – 25, 2021
Nutrients Sampling
Nutrient samples were collected from thirteen local and border river stations and one bay station on September 22, 2021. Please note that due to ongoing mechanical issues with the NBC research vessel, R/V Monitor, bay sampling this week was limited to only the surface at Phillipsdale Landing. Weather conditions leading up to the sampling day was mostly dry, with 0.03 inches of recorded rainfall in the five days prior to sampling.
Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were all observed at Ten Mile River at Central Avenue. At this site, surface TN, TDN, and DIN were 1,920 ppb, 1,910 ppb, and 1,556.9 ppb, respectively. The lowest TN (666 ppb) and TDN (533 ppb) were observed at Moshassuck River at Higginson Avenue, while the lowest DIN (216.8 ppb) was observed Coles River at Milford Road.
This week at the Phillipsdale Landing surface, the results for TN, TDN, and DIN were 777 ppb, 615 ppb, and 433 ppb, respectively.
Results from nutrient sampling on September 29 are pending analysis. The next scheduled sample date is October 6.
Week of September 12 – 18, 2021
Nutrients Sampling
Due to ongoing mechanical issues with the NBC research vessel, R/V Monitor, nutrient sampling was only collected from the surface and bottom waters at the Bullock Reach Buoy station on September 14, 2021. Weather conditions leading up to the sampling day were dry, with no recorded rainfall in the five days prior to sampling.
At the Bullock Reach Buoy surface, the results for total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were 619 ppb, 344 ppb, and 153.8 ppb, respectively. In the bottom waters at this site, TN was 490 ppb, TDN was 347 ppb, and DIN was 216.2 ppb.
Results from nutrient sampling on September 22 are pending analysis. The next scheduled sample date is September 29.
Week of September 26 - October 2, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale Landing was fair-to-poor this week. Rainfall was moderate and Blackstone River flows remained elevated above historical medians. Specifically, 0.35 inches of rainfall were recorded on September 26th and 0.16 inches recorded on September 28th at TF Green. Salinity at the surface decreased compared to the week before, averaging 6.8 ppt and ranging 2.1-11.8 ppt. Bottom salinity increased, averaging 22.5 ppt and ranging 6.9-30.7 ppt. Water temperatures cooled slightly, averaging 19.6°C on the surface and 21.3°C on the bottom. Surface temperatures ranged from 15.9°C to 22.8°C while bottom temperatures ranged from 18.3°C to 22.4°C.
Surface dissolved oxygen (DO) averaged 6.9 mg/L, with a minimum of 4.1 mg/L. Bottom DO averaged 3.1 mg/L, with a minimum of 1.1 mg/L. Hypoxic conditions (DO ≤ 2.9 mg/L) at the bottom increased this week, with the longest duration hypoxic period (10 hours) occurring on September 28th. Generally, DO conditions were better at low tide and hypoxic conditions were associated with the high-salinity flows of the rising and high tide. Chlorophyll concentrations decreased this week, averaging 5.0 ug/L on the surface and 4.2 ug/L on the bottom, with a surface maximum of 15.4 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Sondes were swapped for routine maintenance on the morning of September 29th. Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 26.7 ppt and ranged from 21.6 ppt to 29.8 ppt. Salinity at the mid depth averaged 29.3 ppt and ranged from 24.9 ppt to 33.1 ppt. Salinity in bottom waters averaged 31.8 ppt and ranged from 28.6 ppt to 34.4 ppt. Temperatures cooled since the previous week, averaging 20.7°C, 21.1°C, and 21.1°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 18.4°C to 22.9°C, mid temperatures ranged from 19.4°C to 22.4°C, and bottom temperatures ranged from 19.8°C to 22.0°C.
DO concentrations were similar to the previous week, averaging 6.5 mg/L at the surface, 5.5 mg/L at mid-depth, and 4.9 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 3.7 mg/L. Chlorophyll concentrations averaged 5.1 ug/L at the surface and 4.6 ug/L at mid-depth; please note that approximately 10 hours of mid-depth chlorophyll data from September 29th were omitted from this summary due to a suspect increase which may have been associated with sonde fouling observed at instrument retrieval. Evidence of phytoplankton bloom activity was greatest during the first half of the week. The maximum chlorophyll value in surface waters was 16.3 ug/L, on September 28th.
Week of September 19 - 25, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale Landing was fair-to-poor this week. Rainfall was light to moderate, and Blackstone River flows remained elevated above historical medians. Specifically, 0.13 inches of rain were recorded on September 24th and trace amounts recorded on several other days at TF Green. Salinity at the surface increased compared to the week before, averaging 11.4 ppt and ranging 1.6-21.7 ppt. Bottom salinity averaged 20.9 ppt and ranged 3.5-28.1 ppt. Water temperatures averaged 21.9°C on the surface and bottom for the second week in a row. Surface temperatures ranged from 19.2°C to 23.2°C while bottom temperatures ranged from 21.1°C to 22.6°C.
Surface dissolved oxygen (DO) averaged 5.9 mg/L, with a minimum of 3.1 mg/L. Bottom DO averaged 3.6 mg/L, with a minimum of 2.1 mg/L. Hypoxic conditions (DO ≤ 2.9 mg/L) at the bottom were most extensive early in the week. The longest duration hypoxic period this week was just over 8 hours on September 19th. There was improvement in bottom DO as the week progressed. Chlorophyll concentrations increased slightly this week, averaging 8.1 ug/L on the surface and 7.0 ug/L on the bottom, with a surface maximum of 27.3 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 26.1 ppt and ranged from 21.2 ppt to 28.3 ppt. Salinity at the mid depth averaged 28.0 ppt and ranged from 25.7 ppt to 30.4 ppt. Salinity in bottom waters averaged 29.5 ppt and ranged from 27.3 ppt to 31.5 ppt. Temperatures were similar to the previous week, averaging 22.0°C, 21.7°C, and 21.3°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 20.9°C to 22.8°C, mid temperatures ranged from 20.7°C to 22.4°C, and bottom temperatures ranged from 20.3°C to 22.4°C.
DO concentrations were also similar to the previous week, averaging 6.9 mg/L at the surface, 6.0 mg/L at mid-depth, and 4.9 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 3.4 mg/L. Chlorophyll concentrations averaged 9.0 ug/L at the surface and 5.3 ug/L at mid-depth. Evidence of phytoplankton bloom activity was greatest during the first half of the week. The maximum chlorophyll value in surface waters was 36.4 ug/L, on September 21st.
