Snapshot of the Bay

Historical News

Week of May 1 - 7, 2022

Nutrients Sampling

Nutrient samples were collected from seven local river stations and eight bay stations on May 4, 2022. Most bay stations were sampled at the surface only; one station, Edgewood Shoal, was sampled at the surface and bottom. Moderate rainfall of 0.5 inches was recorded at T.F. Green two days prior to sampling and 0.14 inches was recorded during the day of sampling itself.

Among the river stations sampled, the highest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were all observed at the Pawtuxet River at Broad St. At this site, average of duplicate surface samples measured 1,255 ppb TN, 1,230 ppb TDN, and 996 ppb DIN. The lowest nitrogen concentrations occurred at the Moshassuck River at Higginson Ave. at 464 ppb TN, 561 ppb TDN, and 229 ppb DIN.

Among the bay stations sampled, the highest surface nitrogen concentrations were again measured near the Pawtuxet River, at the Pawtuxet Cove site. Concentrations at this site were 1,080 ppb TN, 1,000 ppb TDN, and 759 ppb DIN. The lowest TN concentration (423 ppb) was measured at Bullock Reach Buoy, while the lowest TDN (211 ppb) and DIN (50 ppb) were measured at Conimicut Point. Surface chlorophyll a concentrations were generally low, averaging 5.6 ug/L with a maximum of 12.0 ug/L measured at Phillipsdale Landing.

Results from nutrient sampling on May 18 are pending analysis. The next scheduled sample date is June 1.

Week of June 12 – 18, 2022

Fixed Site Network

Phillipsdale Landing

Sondes were swapped for routine maintenance on the morning of June 14. Overall, water quality at Phillipsdale Landing was fair to good this week. Weather conditions this week were mostly wet, with 1.57 inches of rainfall recorded at T.F. Green. A majority of the rainfall (1.31 inches) occurred on June 13, resulting in Blackstone River flows declining over the course of the week and remaining below historical 16-year median flow rates. Surface salinity averaged 17.7 ppt and ranged from 5.5 ppt to 26.5 ppt, while bottom salinity averaged 23.4 ppt and ranged from 13.7 ppt to 28.1 ppt. Temperatures continue to warm, averaging 21.6°C at the surface and 20.8°C on the bottom. Surface temperatures ranged from 19.8°C to 24.9°C, while bottom temperatures ranged from 19.6°C to 22.7°C.

Dissolved oxygen (DO) remained above the hypoxia threshold (2.9 mg/L) for most of the week. Surface DO averaged 6.3 mg/L with a minimum of 3.0 mg/L, while bottom DO averaged 4.6 mg/L, with a minimum of 2.2 mg/L. A maximum duration of hypoxia of approximately four hours occurred during late night on June 11. Chlorophyll readings this week were similar to the previous week, averaging 16.1 µg/L on the surface and 13.3 µg/L on the bottom. Maximum surface chlorophyll readings reached 70.5 µg/L. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Overall, water quality at Bullock Reach was good this week. Surface salinity ranged from 23.3 ppt to 30.0 ppt and averaged 27.2 ppt. Salinity at mid-depth ranged from 25.6 ppt to 30.4 ppt and averaged 28.7 ppt. Bottom salinity ranged from 28.9 ppt to 31.1 ppt and averaged 30.2 ppt. Water column temperatures averaged 21.2°C, 20.4°C, and 19.3°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 19.9°C to 23.1°C, mid temperatures ranged from 18.9°C to 21.6°C, and bottom temperatures ranged from 17.8°C to 20.7°C.

This week, DO averaged 7.9 mg/L at the surface, 6.8 mg/L at mid-depth, and 5.3 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 4.1 mg/L. Chlorophyll concentrations were low, averaging 12.2 µg/L at the surface, 11.2 µg/L at mid-depth, and 3.9 µg/L at the bottom. The maximum chlorophyll this week was 41.4 µg/L measured in surface waters on June 15.

Week of June 05 – 11, 2022

Fixed Site Network

Phillipsdale Landing

Overall, water quality at Phillipsdale Landing was fair this week. A total of 1.81 inches of rainfall was recorded at T.F. Green on June 08 and 09, which led to increased flows from the Blackstone River in the middle of the week. Following the influx of freshwater in the middle of the week, salinity decreased at Phillipsdale Landing as the week progressed. Surface salinity averaged 11.9 ppt and ranged from 4.0 ppt to 21.0 ppt, while bottom salinity averaged 22.5 ppt and ranged from 8.3 ppt to 28.2 ppt. Temperatures continue to warm, averaging 21.7°C at the surface and 19.8°C on the bottom. Surface temperatures ranged from 19.0°C to 24.7°C, while bottom temperatures ranged from 17.6°C to 22.4°C.

Dissolved oxygen (DO) concentrations decreased through the week but remained mostly above the hypoxia threshold (2.9 mg/L). Surface DO averaged 8.2 mg/L with a minimum of 3.3 mg/L, while bottom DO averaged 4.2 mg/L, with a minimum of 1.6 mg/L. Chlorophyll readings decreased from the previous week, averaging 15.8 µg/L on the surface and 12.7 µg/L on the bottom. Maximum surface chlorophyll readings reached 80.5 µg/L. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Sondes were swapped for routine maintenance at mid-day on June 08. Please note that there is an extra hour's worth of data included in the summary below caused by updating the timestamps of the sondes to local eastern standard time. Also note that portions of chlorophyll data from the mid-depth sonde from June 08 – 11 are not included in the summary below due to an issue with the chlorophyll sensor. Overall, water quality at Bullock Reach was good this week. Surface salinity ranged from 24.3 ppt to 28.8 ppt and averaged 26.9 ppt. Salinity at mid-depth ranged from 26.4 ppt to 30.2 ppt and averaged 28.8 ppt. Bottom salinity ranged from 29.1 ppt to 32.3 ppt and averaged 30.8 ppt. Water column temperatures averaged 20.5°C, 19.6°C, and 18.0°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 18.4°C to 22.5°C, mid temperatures ranged from 17.9°C to 21.2°C, and bottom temperatures ranged from 15.9°C to 19.8°C.

This week, DO averaged 8.2 mg/L at the surface, 6.8 mg/L at mid-depth, and 5.3 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 4.1 mg/L. Chlorophyll concentrations were low, averaging 8.0 µg/L at the surface, 6.0 µg/L at mid-depth, and 3.0 µg/L at the bottom. The maximum chlorophyll this week was 36.2 µg/L measured in surface waters on June 11.

Week of June 5 - 11, 2022

Bacteria Sampling

On June 7, 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 0.55 inches as recorded at T.F. Green.

Overall, bacteria counts were lower this week than during the previous sampling event on May 25. The geometric mean of fecal coliform results for all sites was 17 MPN/100 mL, with the Seekonk River sites having higher counts than the Providence River sites (geometric means of 65 MPN/100 mL and 9 MPN/100 mL, respectively). The maximum count (930 MPN/100 mL) was measured at Division St. Dock in the Seekonk River.

Enterococci results had an overall geometric mean of 13 MPN/100 mL. Enterococci results ranged from non-detect at four sites (Phillipsdale Landing, South FP East, Gaspee Point, and Conimicut Point) to 63 MPN/100 mL at the Point St. Bridge site.

The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of water ingestion (e.g., swimming, diving, water skiing, and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

	Fecal Coliform	Enterococci
Primary Contact¹	Geometric mean ≤50 MPN/100 mL <10% of samples >400 MPN/100 mL	Geometric mean ≤35 colonies/100 mL All samples ≤104 colonies/100 mL²
Shellfishing	Geometric mean ≤14 MPN/100 mL <10% of samples >49 MPN/100 mL³	NO ENTEROCOCCI CRITERIA

¹Fecal coliform primary contact criteria applied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1); see regulations for complete details.

Week of June 12 - 18, 2022

Water Column Clarity

Water clarity was measured at six locations in the Providence River estuary on June 15, 2022. Conditions leading up to the survey were wet, with 1.34 inches of precipitation recorded in the three days prior. Secchi depth averaged 1.4 meters, compared to 1.8 meters on the previous survey (June 7). The lowest clarity this week (0.9 meters) was measured at Pawtuxet Cove, while the greatest clarity (2.0 meters) was measured at Bullock Reach. There was no clear north-to-south gradient in water clarity among the sites this week.