News – Page 6 – Narrabay

August 11 – 17, 2025

Phillipsdale Landing

Sondes were swapped this week on the morning of August 14^th. Overall, the water quality at Phillipsdale Landing was good to fair this week. Weather conditions included sporadic rain events, with 0.37 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week. Surface salinity averaged 20.7 ppt and ranged from 12.2 ppt to 25.0 ppt. At the bottom, salinity averaged 24.8 ppt and ranged from 19.1 ppt to 29.3 ppt. Temperatures averaged 25.6°C at the surface and 25.2°C at the bottom. Surface temperatures ranged from 22.0°C to 27.9°C, while bottom temperatures ranged from 24.1°C to 26.8°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface, while DO at the bottom waters dropped below the hypoxic threshold throughout the week. The longest period of hypoxic conditions spanned 6 hours, occurring during the day of August 16^th. During this period, the bottom DO averaged around 2.32 mg/L. Surface DO averaged 6.9 mg/L and ranged from 3.2 mg/L to 13.3 mg/L. Bottom DO concentrations averaged 4.2 mg/L and ranged from 1.4 mg/L to 12.4 mg/L. Chlorophyll readings decreased from last week, averaging 26.7 µg/L at the surface and 27.0 µg/L at the bottom. Maximum chlorophyll at the surface reached 154.4 µg/L on the morning of August 16^th. 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 was good to fair at Bullock Reach this week. Salinity averaged 28.2 ppt, 29.5 ppt, and 30.4 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 26.0– 29.6 ppt, middle salinity ranged 0.0 – 30.7 ppt, and bottom salinity ranged 29.2 – 31.3 ppt. Surface temperature averaged 25.0°C and ranged from 23.5°C to 26.5°C. Middle temperature averaged 24.3°C and ranged from 22.7°C to 25.8°C. Bottom temperatures averaged 23.2°C and ranged from 21.3°C to 24.9°C.

Dissolved oxygen (DO) at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface and middle depths throughout the week. DO at the bottom waters dropped below the hypoxic threshold for half an hour on the morning of August 11^th. Surface DO averaged 7.5 mg/L and ranged 5.6 – 10.1 mg/L. At the middle depth, DO averaged 5.9 mg/L and ranged 3.9 – 8.6 mg/L. At the bottom, DO averaged 4.4 mg/L and ranged 2.4 – 6.4 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 16.3 µg/L at the surface, 10.1 at the middle, and 3.7 µg/L at the bottom. The maximum surface chlorophyll was 34.4 µg/L on the afternoon of August 15^th.

November 26, 2025

Nutrient samples were collected from seven river stations and one bay station on November 26^th. The bay station was sampled at the surface and bottom. In the five days prior to sampling, 0.59” of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN) and dissolved inorganic nitrogen (DIN) were observed at Pawtuxet River @Broad St (TN = 1,740 ppb, DIN = 1,562.0 ppb). The highest total dissolved nitrogen (TDN) was observed at Woonasquatucket River @Valley St (TDN = 1820 ppb). The lowest TN and TDN were observed at Moshassuck River @Footbridge at Mill St (TN = 536 ppb, TDN = 723 ppb). The lowest DIN was observed at Woonasquatucket River @ Manton Ave. Bridge (DIN = 389.4 ppb).

At the bay station sampled, Phillipsdale Landing, the surface concentrations were as follows: total nitrogen (TN) = 1,420 ppb, total dissolved nitrogen (TDN) = 1,380 ppb and dissolved inorganic nitrogen (DIN) = 1018.5 ppb.

The next scheduled sampling date is December 10^th, 2025.

November 13, 2025

Nutrient samples were collected from six bay stations on November 13^th. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, 0.69” of precipitation were recorded at T.F. Green.

Among the bay stations sampled, the highest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Pawtuxet Cove (TN = 1,160 ppb, TDN = 1200 ppb, DIN = 940.8 ppb). The lowest surface TN, TDN, and DIN were observed at Bullock Reach (TN = 540 ppb, TDN = 464 ppb, DIN = 258.0 ppb).

The next scheduled sampling date is November 26^th, 2025.

November 12, 2025

Nutrient samples were collected from seven river stations on November 12^th. In the five days prior to sampling, 0.69” of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Pawtuxet River @ Broad St. (TN = 1,520 ppb, TDN = 2,430 ppb, DIN = 1,340.6 ppb). The lowest TN and DIN were observed at Moshassuck River @ Footbridge at Mill St. (TN = 533 ppb, DIN = 342.2 ppb). The lowest TDN was observed at Woonasquatucket River @ Manton Ave. Bridge (669 ppb).

The next scheduled sampling date is November 13^th, 2025.

December 3, 2025

On December 3rd, 2025, thirteen stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; two of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 0.97 inches of precipitation was recorded at TF Green. Overall, bacteria counts were higher than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 471 MPN/100 mL for the Seekonk River compared to 56 MPN/100mL for the Providence River) for sampling conducted on December 3rd. The maximum count (1,500 MPN/100 mL) was measured at the Crook Point sampling location.

Fecal coliform counts were higher in the Providence River, compared to the previous sampling on November 19th (geometric mean of 56 MPN/100 mL compared to 22 MPN/100 mL on 11/19). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on November 19th (geometric mean of 471 MPN/100 mL compared to 31 MPN/100 mL on 11/19).

Enterococci results had an overall geometric mean of 208 MPN/100 mL. Enterococci counts ranged from 122 MPN/100 mL at Phillipsdale Landing to 504 MPN/100 mL at Point Street Bridge.

The next scheduled sampling date is December 17^th.

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 ingesting water (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.

October 15, 2025

Phytoplankton samples were collected on October 15, 2025 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

It was sunny and windy on this day. The water temperature was 16.13 °C and the salinity was 26.53 psu.

The qualitative tow net sample had a short to moderate filtration time. The filtrate was light tan and contained some dark precipitates.

The analysis of the quantitative whole water sample revealed a total of 69,000 cells/L. The microflagellates were found at 30,000 cells/L. The most predominant phytoplankton genera were Chaetoceros spp. at 31,000 cells/L, Prorocentrum spp. at 3,000 cells/L, and pennate diatoms at 3,000 cells/L.

400x phase contrast image of *Dinophysis acuminata*

Dinophysis acuminata is a marine phytoplankton species of dinoflagellates that is found in the coastal waters of Rhode Island and north Atlantic waters. This is one of several phototrophic species that are classed as toxic, as they produce okadaic acid which can cause diarrhetic shellfish poisoning (DSP).

October 29, 2025

Nutrient samples were collected from thirteen river stations on October 29^th. In the five days prior to sampling, trace amounts of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Ten Mile River @ Central Ave. (TN = 2,710 ppb, TDN = 2,720 ppb, DIN = 2,640.0 ppb). The lowest TN was observed at Moshassuck River @ Footbridge at Mill St. (590 ppb). The lowest TDN was observed at Palmer River @ Rt. 6 (691 ppb). The lowest DIN was observed at Coles River @ Milford Rd. (101.4 ppb).

The next scheduled sampling date is November 13^th, 2025.

October 15, 2025

Nutrient samples were collected from seven river stations and seven bay stations on October 15^th. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, 2.41” of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Blackstone River @ Bikepath Bridge (TN = 1,390 ppb, TDN = 1,390 ppb, DIN = 971.9 ppb). The lowest TN, TDN, and DIN were observed at Moshassuck River @ Footbridge at Mill St. (TN = 577 ppb, TDN = 542 ppb, DIN = 310.8 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN) and dissolved inorganic nitrogen (DIN) were observed at Phillipsdale Landing (TN = 1,320 ppb, DIN = 833.0 ppb). The highest surface total dissolved nitrogen (TDN) was observed at Pawtuxet Cove (1770 ppb). The lowest surface TN, TDN, and DIN were observed at Bullock Reach (TN = 642 ppb, TDN = 522 ppb, DIN = 245 ppb).

The next scheduled sampling date is October 29^th, 2025.

October 1, 2025

Nutrient samples were collected from thirteen river stations and eight bay stations on October 1st. In the five days prior to sampling, 0.06” of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Ten Mile River @ Central Ave. (TN = 1,860 ppb, TDN = 1,830 ppb, DIN = 1,516.0 ppb). The lowest TN was observed at Coles River @ Milford Rd. (661 ppb). The lowest TDN was observed at Taunton River @ Berkley Bridge (385 ppb). The lowest DIN was observed at Taunton River @ River Rd. (119.9 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Phillipsdale Landing (TN = 967 ppb, TDN = 737 ppb, DIN = 415.0 ppb). The lowest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Pomham Rocks (TN = 556 ppb, TDN = 363 ppb, DIN = 149.9 ppb).

The next scheduled sampling date is October 15^th, 2025.

November 19, 2025

On November 19th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 0.77 inches of precipitation was recorded at TF Green. Overall, bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 31 MPN/100 mL for the Seekonk River compared to 22 MPN/100mL for the Providence River) for sampling conducted on November 19th. The maximum count (430 MPN/100 mL) was measured at the Point Street Bridge sampling location.

Fecal coliform counts were lower in the Providence River, compared to the previous sampling on November 5th (geometric mean of 22 MPN/100 mL compared to 63 MPN/100 mL on 11/5). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on November 5th (geometric mean of 31 MPN/100 mL compared to 196 MPN/100 mL on 11/5).

Enterococci results had an overall geometric mean of 16 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at South FP East and Conimicut Point to 61 MPN/100 mL at Point Street Bridge.

The next scheduled sampling date is December 3^rd.

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

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