Historical News
Fixed Site Network
Water quality was fair to poor this week at Phillipsdale Landing. This week, 0.54 inches of precipitation was recorded, with the majority of this rainfall (0.42 in) occurring on September 2. Sondes were changed out for routine maintenance the morning of September 1.
Tides and rainfall influenced fluctuations in water column salinity throughout the week. Surface salinity averaged 20.8 ppt and ranged from 10.4 ppt to 25.8 ppt. Bottom salinity averaged 26.1 ppt and ranged from 19.2 ppt to 30.0 ppt. Surface and bottom temperatures decreased slightly throughout the week, averaging 23.7°C and 23.6°C, respectively. Surface temperatures ranged from 20.5°C to 25.6°C, while bottom temperatures ranged from 22.7°C to 24.7°C.
Hypoxia (dissolved oxygen [DO] ≤ 2.9 mg/L) was observed intermittently in surface waters during the beginning of the week and frequently in bottom waters throughout the week. Surface DO averaged 5.9 mg/L and ranged from 2.0 mg/L to 11.4 mg/L. Bottom DO averaged 3.2 mg/L and ranged from 1.3 mg/L to 8.3 mg/L. The greatest duration of bottom hypoxia this week occurred for approximately 24 hours from the afternoon of August 30th to the afternoon of August 31st. Surface chlorophyll averaged 28.1 ug/L, while bottom chlorophyll readings averaged 13.8 ug/L; maximum readings observed at both depths were > 35 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location.
Bullock Reach
Water quality was good this week at Bullock Reach. Please note, a specific conductivity/temperature sensor was replaced on the mid-depth sonde on September 3 after the sensor sustained damage in the field; impacted data are excluded from this analysis. Surface salinity averaged 29.2 ppt and ranged from 27.3 ppt to 30.5 ppt. Salinity increased with depth, averaging 30.6 ppt at the middle of the water column (range: 29.1 ppt to 32.4 ppt) and 31.0 ppt at the bottom of the water column (range: 29.9 ppt to 32.1 ppt). Temperatures at all three depths decreased slightly throughout the week, averaging 22.9°C, 22.6°C, and 22.2°C at the surface, middle, and bottom of the water column, respectively. Surface temperatures ranged from 22.1°C to 24.6°C, mid temperatures ranged from 21.9°C to 23.3°C, and bottom temperatures ranged from 21.3°C to 23.1°C.
Dissolved oxygen (DO) concentrations remained above the hypoxia threshold (2.9 mg/L) at all three depths. Surface DO averaged 7.5 mg/L, with a minimum of 5.1 mg/L. Mid DO averaged 6.3 mg/L, with a minimum of 4.0 mg/L, and bottom DO averaged 5.0 mg/L, with a minimum of 3.4 mg/L. Surface chlorophyll averaged 12.4 ug/L, with a maximum concentration of 71.6 ug/L. Chlorophyll concentrations of ≥ 25 ug/L were also observed at the mid and bottom depths.
Bacteria Sampling
Twenty stations were sampled for fecal coliform in the Providence and Seekonk Rivers on September 2, 2020. Five of these stations were also sampled for enterococci bacteria. Conditions leading up to the September 2 sampling day were mostly dry, with 0.12 inches of rainfall recorded over the five days prior.
The geometric mean of fecal coliform results for all sites was 18 MPN/100 mL, with Seekonk River sites having higher counts than Providence River sites (geometric means of 125 and 7 MPN/100 mL, respectively). The maximum count (430 MPN/100 mL) was measured at the Phillipsdale Landing site in the Seekonk River. Fecal coliform results in the Providence River were within the state standards for primary contact and shellfishing, however, results from the Seekonk River exceeded both state standards.
The enterococci results decreased slightly from the previous sampling event, from an overall geomean of 17 MPN/100mL to 10 MPN/100mL. Enterococci results ranged from <10 MPN/100 mL at four sites (Phillipsdale Landing, South FP East, Gaspee Point, and Conimicut Point) to 20 MPN/100 mL at Point St. Bridge site. Enterococci results from both the Seekonk and Providence Rivers were within state primary contact standards.
Please note: the results of NBC's fecal coliform and enterococci monitoring are for informational/research purposes only and are not to intended to suggest official state compliance with bathing or shellfishing standards.
Fixed Site Network
Phillipsdale Landing
Water quality was poor this week at Phillipsdale Landing. Despite 0.63 inches of rainfall recorded over the course of the week, conditions at this site remained steady with a slight salinity increase observed towards the end of the week. Both surface and bottom water salinity decreased from the previous week, with evidence of increased stratification beginning on August 25th. For the week, surface salinity averaged 21.2 ppt (range 10.3 – 26.4 ppt) while bottom salinity averaged 26.1 ppt (range 19.3 – 29.1 ppt). Both surface and bottom water temperatures increased from the previous week; surface temperatures averaged 24.5°C (range 21.0°C – 27.5°C) while bottom temperatures averaged 24.5°C (range 23.4°C – 26.6°C). Dissolved oxygen (DO) concentrations decreased in both surface and bottom waters, leading to sustained periods of hypoxia (DO < 2.9mg/L) towards the end of the week. For the week, surface water DO averaged 4.6 mg/L with a minimum of 1.2 mg/L and the longest period of sustained hypoxic conditions (7.25 hours) started in the evening of August 27th. Bottom water DO was below the hypoxic threshold starting late night on August 25th, averaging 2.6 mg/L with a minimum of 0.5 mg/L. Surface chlorophyll decreased from the previous week, averaging 15.8 ug/L with a maximum of 71.4 ug/L occurring in the afternoon on August 24th.
Bullock Reach
Water quality was good this week at Bullock Reach. Overall, salinity at all depths decreased slightly from the previous week with evidence of increased salinity stratification occurring during the middle of the week; surface salinity averaged 29.4 ppt (range 28.3 – 30.3 ppt), mid water salinity averaged 30.2 ppt (range 28.8 – 31.2 ppt) and bottom salinity averaged 31.2 ppt (range 29.8 – 31.9 ppt). Water temperatures at all depths increased from the previous week; surface water temperatures ranged from 22.4°C to 26.1°C averaging 24.0°C, mid-depth water temperature ranged from 22.6°C to 25.5°C averaging 23.7°C, and bottom water temperature ranged from 22.2°C to 24.9°C averaging 23.3°C. Periodic periods of stronger temperature stratification was observed over the course of the week. This week dissolved oxygen (DO) concentrations did not fall below the hypoxic threshold (2.9 mg/L) at any depth. Overall, surface DO averaged 6.8 mg/L with a minimum of 4.9 mg/L, mid-depth DO averaged 5.9 mg/L with a minimum of 3.2 mg/L, and bottom DO averaged 4.8 mg/L with a minimum of 3.2 mg/L. Chlorophyll at all depths decreased this week; surface chlorophyll averaged 6.3 ug/L with a maximum of 31.5 ug/L, while mid and bottom waters averaged 4.7 ug/L and 12.7 ug/L, respectively.
Nutrients Sampling
Among the river stations sampled, total nitrogen (TN) ranged from 582 ppb at the Moshassuck River at Higginson Avenue site to 2,070 ppb at the Warren Reservoir/Kickemuit River. The highest dissolved nitrogen concentrations occurred at Pawtuxet River at Broad Street, where total dissolved nitrogen (TDN) measured 1,750 ppb and dissolved inorganic nitrogen (DIN) measured 1,349 ppb. Dissolved nitrogen concentrations were lowest at the Palmer River at Rt. 6 site, where TDN and DIN measured 524 ppb and 13 ppb, respectively.
Results from sampling on August 13, 26, and September 10 are pending analysis.
R/V Monitor's Blog
The R/V Monitor was out on the upper Bay twice this week. First, on Wednesday, September 2nd, the crew was out collecting bacteria samples, taking Secchi Disk and Par sensor water clarity measurements, conducting water column profiles using Seabird and sonde instruments, and conducting real-time surface mapping of water quality parameters, including dissolved oxygen, chlorophyll, water temperature, salinity, and pH, all in an effort to document water quality improvements associated with NBC construction projects. Jeff captained the boat while monitoring professionals Sara and Steve collected the samples and data. The day started cloudy and humid with calm waters. Light winds picked up out of the South and intermittent showers occurred by mid-morning. On Thursday, September 3rd, the crew serviced the mid-depth sonde on the Bullock's Reach Buoy. In addition, the temporary buoy in Pawtuxet Cove was serviced, as the sonde was changed out with a freshly calibrated sonde. The day started cloudy with rain showers. There was no wind and the water remained calm. The featured photo taken Wednesday while in the Seekonk River shows Osprey flying overhead.
