Week of March 14 – 20, 2021
Water Column Clarity
Water clarity was measured at seven locations in the Providence and Seekonk Rivers on March 17, 2021. No precipitation was recorded in the five days prior to the survey. Overall, water clarity decreased from the previous survey. Secchi depth averaged 2.56 meters, compared to 4.04 meters on February 24, 2021. The lowest clarity (2.30 meters) was measured at India Point Park, while the greatest clarity (2.90 meters) was measured at Conimicut Point. Generally, water clarity increased along a down-bay gradient this week.
Week of March 14 - 20, 2021
Fixed Site Network
Phillipsdale Landing
Sondes were changed out for routine maintenance this week mid-day on March 16. Water quality at Phillipsdale was good this week. Heavy rains totaling 1.01 inches were recorded on March 18-19 at TF Green. Blackstone River flows exhibited an increase following these rains, but remain below average for this time of year. Salinity at the Phillipsdale surface averaged 11.4 ppt and ranged from 2.9 ppt to 24.5 ppt. Bottom salinity averaged 21.7 ppt and ranged from 6.3 ppt to 29.5 ppt. Surface and bottom water temperatures remain cold, averaging 5.1°C and 4.7°C, respectively. Surface temperatures ranged from 1.9°C to 8.4°C, while bottom temperatures ranged from 3.4°C to 7.6°C.
Dissolved oxygen (DO) was high at both depths, typical for this time of year, and well above the hypoxia threshold (2.9 mg/L). Surface DO averaged 12.9 mg/L, with a minimum of 11.7 mg/L, and bottom DO averaged 11.9 mg/L, with a minimum of 9.4 mg/L. Chlorophyll concentrations came up from the previous week, averaging 8.2 ug/L at the surface and 51.0 ug/L at the bottom. Maximum surface chlorophyll concentrations reached 37.2 ug/L, measured on March 15; note elevated chlorophyll readings (particularly at the bottom this week) may be impacted by suspended particulates or other matter. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location.
Bullock Reach
Bullock Reach sondes are expected to be deployed in May 2021.
Week of March 7 - 13, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale was good this week. The weather was dry, with no recorded precipitation at TF Green. Blackstone River flows exhibited a slight uptick mid-week, but remain below average for this time of year. Salinity at the Phillipsdale surface averaged 7.1 ppt and ranged from 2.3 ppt to 16.1 ppt. Bottom salinity averaged 19.8 ppt and ranged from 3.9 ppt to 28.4 ppt. Surface and bottom water temperatures remain cold, averaging 5.4°C and 4.5°C, respectively. Surface temperatures ranged from 1.6°C to 9.4°C, while bottom temperatures ranged from 2.2°C to 8.2°C.
Dissolved oxygen (DO) was high at both depths, typical for this time of year, and well above the hypoxia threshold (2.9 mg/L). Surface DO averaged 13.0 mg/L, with a minimum of 11.2 mg/L, and bottom DO averaged 11.5 mg/L, with a minimum of 10.0 mg/L. Chlorophyll concentrations came up from the previous week, averaging 5.5 ug/L at the surface and 22.8 ug/L at the bottom. Maximum surface chlorophyll concentrations reached 55.8 ug/L, measured on March 10; note elevated chlorophyll may be due to interference by sediment or macroalgae, as these readings were not associated with changes in pH or DO saturation that typically co-occur with phytoplankton bloom activity. Please note also that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location.
Bullock Reach
Bullock Reach sondes are expected to be deployed in May 2021.
Week of February 28 - March 6, 2021
Fixed Site Network
Phillipsdale Landing
Phillipsdale Landing sondes were deployed for the start of the 2021 monitoring season on March 3. Water quality at this site was good this week. Moderate rain events on February 27-28 (0.69 inches) and March 1 (0.34 inches) preceded sonde deployment, though the rest of the week was dry (NOAA TF Green data). Blackstone River flows were declining over the course of the week. This week, salinity at the surface averaged 6.2 ppt and ranged from 2.6 ppt to 10.7 ppt. Bottom salinity averaged 17.6 ppt and ranged from 3.5 ppt to 27.5 ppt. Surface and bottom water temperatures remain cold, averaging 3.1°C and 3.2°C, respectively. Surface temperatures ranged from 1.5°C to 4.9°C, while bottom temperatures ranged from 2.3°C to 4.3°C.
Dissolved oxygen (DO) was high at both depths, typical for this time of year, and well above the hypoxia threshold (2.9 mg/L). Surface DO averaged 13.0 mg/L, with a minimum of 12.4 mg/L, and bottom DO averaged 11.4 mg/L, with a minimum of 10.2 mg/L. Chlorophyll concentrations were low, averaging 2.9 ug/L at the surface and 5.3 ug/L at the bottom. Maximum surface chlorophyll concentrations reached 9.2 ug/L, measured on March 6. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location.
Bullock Reach
Bullock Reach sondes are expected to be deployed in May 2021.
Week of March 28 - April 3, 2021
Bacteria Sampling
On March 31, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers. Five of these stations were also sampled for enterococci bacteria. Precipitation in the five days prior to sampling totaled 1.53 inches, with a majority of the rainfall (1.47 inches) occurring on March 28.
The geometric mean of fecal coliform results for all sites was 31 MPN/100 mL, with Seekonk River sites having higher counts than Providence River sites (geometric means of 116 and 16 MPN/100 mL, respectively). The maximum count (230 MPN/100 mL) was measured at both Phillipsdale Landing and Crook Point in the Seekonk River. Overall, fecal coliform results from the Seekonk River exceeded both state shellfishing and primary contact standards. Fecal coliform results from the Providence River also exceed state shellfishing standards, but results were within state primary contact standards for the Providence River.
Enterococci results increased slightly from the previous sampling event, from an overall geometric mean of 12 MPN/100 mL to 16 MPN/100 mL. Enterococci results at all sites ranged from <10 MPN/100 mL at three stations (South FP East, Gaspee Point, and Conimicut Point) to 63 MPN/100 mL at Phillipsdale Landing. Overall, enterococci results were within state primary contact standards for both rivers.
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.
