Daria DiBiasio – Page 2

May 21, 2025

On May 21st, 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, 0.04 inches of precipitation was recorded at TF Green. Overall bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were lower in the Seekonk River, compared to the Providence River (geometric mean of 37 MPN/100 mL for the Seekonk River compared to 45 MPN/100mL for the Providence River) for sampling conducted on May 21st. The maximum count (2,300 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 May 7th (geometric mean of 45 MPN/100 mL compared to 369 MPN/100 mL on 5/7). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on May 7th (geometric mean of 37 MPN/100 mL compared to 1121 MPN/100 mL on 5/7).

Enterococci results had an overall geometric mean of 16 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 74 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is June 4^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.

May 7, 2025

On May 7th, 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, 2.10 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 1121 MPN/100 mL for the Seekonk River compared to 369 MPN/100mL for the Providence River) for sampling conducted on May 7th. The maximum count (9,300 MPN/100 mL) was measured at the Collier Point Park sampling location.

Fecal coliform counts were higher in the Providence River, compared to the previous sampling on April 23rd (geometric mean of 369 MPN/100 mL compared to 12 MPN/100 mL on 4/23). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on April 23rd (geometric mean of 1121 MPN/100 mL compared to 72 MPN/100 mL on 4/23).

Enterococci results had an overall geometric mean of 128 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at Conimicut Point to 2046 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is May 21^st.

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.

April 23, 2025

On April 23rd, 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, 0.05 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 72 MPN/100 mL for the Seekonk River compared to 12 MPN/100mL for the Providence River) for sampling conducted on April 23rd. 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 March 26th (geometric mean of 12 MPN/100 mL compared to 38 MPN/100 mL on 3/26). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on March 26th (geometric mean of 72 MPN/100 mL compared to 67 MPN/100 mL on 3/26).

Enterococci results had an overall geometric mean of 12 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 20 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is May 7th.

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.

June 11, 2025

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on June 11, 2025. In the five days prior to the survey, 0.85 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.4 meters. The lowest clarity this week (2.1 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.9 meters) was measured at India Point Park. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity among most sites remained relatively consistent compared to previous measurements (data collected June 4, 2025). However, water quality at Point Street Bridge decreased (1.1 meters) and water quality at Bullock’s Reach decreased (1.3 meters), both compared to previous measurements (data collected June 4, 2025).

June 4, 2025

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on June 4, 2025. In the five days prior to the survey, 0.39 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.6 meters. The lowest clarity this week (1.9 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.5 meters) was measured at Point Street Bridge and Bullock’s Reach. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity remained approximately the same from the previous measurements (data collected May 28, 2025).

May 28, 2025

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on May 28, 2025. In the five days prior to the survey, 0.15 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.5 meters. The lowest clarity this week (1.7 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.9 meters) was measured at Edgewood Shoal. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity among most sites remained relatively consistent compared to previous measurements (data collected May 21, 2025). However, water quality at Conimicut Point decreased (1.2 meters) from the previous measurements (data collected May 21, 2025).

May 21, 2025

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on May 21, 2025. In the five days prior to the survey, 0.04 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.8 meters. The lowest clarity this week (2.1 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.9 meters) was measured at Conimicut Point. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity increased from the previous measurements (data collected May 14, 2025).

May 14, 2025

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on May 14, 2025. In the five days prior to the survey, 1.73 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.0 meters. The lowest clarity this week (1.7 meters) was measured at Phillipsdale Landing, Edgewood Yacht Club, and Bullock’s Reach, while the greatest clarity (2.5 meters) was measured at Conimicut Point. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity decreased from the previous measurements (data collected May 7, 2025).

May 7, 2025

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on May 7, 2025. In the five days prior to the survey, 2.10 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.8 meters. The lowest clarity this week (1.5 meters) was measured at Phillipsdale Landing, while the greatest clarity (4.3 meters) was measured at Conimicut Point. There was a general north-to-south trend of increasing water clarity among the sites this week.

May 14, 2025

Phytoplankton samples were collected on May 14, 2025 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

The water temperature was 16.64 degrees Celsius, and the salinity was 13.43 psu. The qualitative tow net sample had a quick filtration time and the filtrate was mostly clear in appearance.

The analysis of the quantitative whole water sample revealed a total of 1,158,000 cells/L. The microflagellates were found at 307,000 cells/L. The most predominant phytoplankton genera were Dinoflagellate spp. at 523,000 cells/L, Skeletonema spp. at 290,000 cells/L, and Chaetoceros spp. at 20,000 cells/L.

200x phase contrast micrograph of Dictyocha spp.

Dictyocha is a genus of silicoflagellates, which are marine photosynthetic unicellular protists that take the form of either flagellates or axopodial amoebae. Many important species of phytoplankton belong to this genus, and some of them are responsible for algal blooms that are toxic to fish. Silicoflagellates are most commonly found in inshore waters, though they can also be found in temperate, polar, coastal and oceanic regions.