May 28-June 3, 2023

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on May 31, 2023 using a Seabird Electronics profiler. There was no precipitation recorded at T.F. Green in the three days leading up to the survey. All sites exhibited strong density stratification except for Pomham Rocks, which was moderately stratified.

Dissolved oxygen (DO) conditions remained above the hypoxia threshold (2.9 mg/L) at all sites this week; the lowest DO observed was approximately 3.01 mg/L in the bottom waters of Edgewood Shoal. Fluorescence was fairly low this week, ranging from 1.80 to 11.9 mg/m3.

May 28-June 3, 2023

Phillipsdale Landing

Overall, water quality at Phillipsdale Landing was fair to good. Weather conditions were dry this week, with only a very light rain of 0.02 inches recorded at T.F. Green. Blackstone River flow continued its declined over the course of the week from the increase in flow last week on May 20th. Surface salinity averaged 9.2 ppt and ranged from 3.3 ppt to 21.8 ppt. At the bottom, salinity averaged 21.0 ppt and ranged from 4.4 ppt to 27.6 ppt. Temperatures increased this week, averaging 20.2°C at the surface and ranging 16.5°C – 23.6°C. At the bottom, temperatures averaged 17.6°C and ranged 15.1°C –21.0°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L at the surface. DO dropped below the hypoxia threshold at the bottom intermittently through May 28th to May 31st. Surface DO increased from the previous week, averaging 10.3 mg/L and ranging 6.0-17.5 mg/L. Bottom water DO concentration averaged 4.9 mg/L and ranged from 1.9 mg/L to 11.3 mg/L. Chlorophyll readings increased from last week, averaging 18.9 ug/L at the surface and 18.4 ug/L at the bottom. Maximum chlorophyll at the surface reached 58.2 ug/L in the afternoon of May 31st. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location. Also, please note that an isolated portion of suspect chlorophyll data from May 29th was excluded from the summary.

Bullock Reach 

Bullock Reach sondes was deployed on June 1st for the season. Please note that due to the technical difficulties which occurred on June 1st during set up and the week ending on June 3rd, this post is based on a very limited Bullock Reach data set. Overall, water quality was good at Bullock Reach this week. Salinity averaged 24.1 ppt, 25.8 ppt, and 30.0 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 21.3-26.2 ppt, mid salinity ranged 22.0-29.0 ppt, and bottom salinity ranged 28.2-31.1 ppt. Surface temperature averaged 20.1°C and ranged from 16.9°C to 21.9°C. Mid temperatures averaged 19.2°C and ranged from 16.7°C to 21.3°C. Bottom temperatures averaged 15.1°C and ranged from 13.6°C to 17.1°C.

DO concentrations at Bullock Reach remained above the hypoxia threshold all week. Surface DO averaged 8.6 mg/L and ranged 7.2 – 10.4 mg/L. In the mid waters, DO averaged 7.7 mg/L and ranged 5.9 – 9.1 mg/L. At the bottom, DO averaged 5.3 mg/L and ranged 4.6– 6.5 mg/L.  Chlorophyll concentrations were low, averaged 7.4 ug/L, 8.6 ug/L, and 2.3 ug/L at the surface, mid, and bottom waters, respectively. The maximum surface chlorophyll of 11.6 ug/L was during the morning of June 3rd.

May 21-27, 2023

​Surface chlorophyll data were collected on May 24, 2023 while the R/V Monitor was underway collecting bacteria samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as good in the Seekonk River area and fair in all the other areas surveyed. Overall, chlorophyll ranged between 1.13 and 23.93 µg/L with an average of 8.84 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

May 21-27, 2023

​Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on May 24. Rainfall totaling 3.04 inches was recorded at TF Green in the five days prior to the survey, most of which occurred on May 20. Secchi depth averaged 1.3 meters, compared to 2.0 meters on the previous survey (May 18). The lowest clarity this week (0.9 meters) was measured at Pomham Rocks and Edgewood Yacht Club while the greatest clarity (1.7 meters) was measured at Bullock Reach and Point St. Bridge. There was a general north-to-south gradient of increasing water clarity among the sites this week.​

May 21-27, 2023

​On May 24, 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 3.04 inches as recorded at TF Green, most of which occurred on May 20. 

The geometric mean of fecal coliform results for all sites was 73 MPN/100 mL compared to 23 MPN/100 mL on May 10. Overall, bacteria counts were higher in the Seekonk River and Providence River this week than during the previous sampling event on May 10. Fecal coliform counts were geomeans of 132 MPN/ 100 mL in the Seekonk River and 56 MPN/ 100 mL in the Providence River. The maximum count (430 MPN/100 mL) was measured at Narragansett Boating Center (Seekonk River) and Point St. Bridge (Providence River). 

Enterococci results had an overall geometric mean of 13 MPN/100 mL. Enterococci counts ranged from non-detect at Phillipsdale Landing, South FP East, and Conimicut Point to 74 MPN/100 mL at Point St. Bridge.​

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 Coli​fo​rmEnterococci
Primary Con​​​t​a​c​t1​​​​​Geom​e​tric me​a​n​ ≤50 MPN/1​​00​ mL
<10% ​o​f​ samples >400 MPN/100 mL		Geom​etric mean ≤35 colo​nies/100 mL​
All sa​mples ≤104 colonies/100 ​​mL2
ShellfishingGeometric mean ≤14 MPN/100​ mL
<10% of samples >49 MPN/100 mL3​		NO ENTEROCOCCI CR​ITERIA

1Fecal coliform primary contact criteria app​lied 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 21-27, 2023

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on May 24, 2023 using a Seabird Electronics profiler. In the three days leading up to the survey, there were 0.02 inches of precipitation recorded at T.F. Green. Despite the lack of recent rainfall, all sites exhibited strong density stratification except for Point St Bridge, which exhibited moderate density stratification.

Dissolved oxygen (DO) conditions remained above the hypoxia threshold (2.9 mg/L) at all sites this week; the lowest DO observed was approximately 4.56 mg/L in the bottom waters of Phillipsdale landing. Fluorescence was low to moderately elevated this week, with the highest value (25.3 mg/m3) observed at Pomham Rocks.

May 21-27, 2023

​Phillipsdale Landing

Overall, water quality at Phillipsdale Landing was fair to good this week. Weather conditions were dry this week, with only a very light rain of 0.02 inches recorded at T.F. Green. Blackstone River flow started the week off with a high flow rate due to the May 20th storm, but then decreased over the course of the week. Surface salinity remained well below bottom salinity. Surface salinity this week averaged 13.2 ppt and ranged from 6.5 ppt to 24.5 ppt. At the bottom, salinity averaged 22.5 ppt and ranged from 9.6 ppt to 28.6 ppt. Salinity at the surface averaged 5.2 ppt and ranged from 1.9 ppt to 8.9 ppt. At the bottom, salinity averaged 15.8 ppt and ranged from 3.2 ppt to 27.8 ppt. Temperatures this week averaged 18.3°C at the surface and 16.3 °C at the bottom. Surface temperatures ranged from 15.3°C to 22.0°C, while bottom temperatures ranged from 14.0°C to 19.5°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L at the surface. DO dropped below the hypoxia threshold at the bottom only briefly on the morning of May 26th. Surface DO remained similar to the previous week, averaging 8.3 mg/L and ranging 6.9-10.0 mg/L. Bottom water DO concentration averaged 5.6 mg/L and ranged from 2.0 mg/L to 8.6 mg/L. Chlorophyll concentrations decreased from the previous week, averaging 2.8 ug/L at the surface and 13.1 ug/L at the bottom. Maximum surface chlorophyll readings reached 34.5 ug/L, recorded in the morning of March 23rd. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location. Also, please note that isolated portions of chlorophyll data from the surface sonde on May 23rd and from the bottom sonde on May 27th were excluded from the summary this week due to suspected interference.

Bullock Reach 

Bullock Reach sondes will be deployed later this spring for the 2023 monitoring season. 

May 14-20, 2023

​Surface chlorophyll data were collected on May 18, 2023 while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as good in the areas surveyed. Overall, chlorophyll ranged between 1.79 and 7.20 µg/L with an average of 3.29 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

May 14-20, 2023

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on May 18. There was no precipitation recorded at TF Green in the five days prior to the survey. Secchi depth averaged 2.0 meters, compared to 1.9 meters on the previous survey (May 10). The lowest clarity this week (1.4 meters) was measured at Pawtuxet Cove while the greatest clarity (2.6 meters) was measured at Phillipsdale Landing and India Point Park. There was no clear north-to-south gradient in water clarity among the sites this week.​

May 14-20, 2023

​Phytoplankton samples were collected on May 18, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. It was a beautiful sunny day with little to no wind on Narragansett Bay. Floating dead algae were detected and the Secchi disk measured 2.2 meters. Sondes data revealed the surface water temperature was 14.23⁰C, salinity was 24.16 psu, and chlorophyll a was 3.63 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light brown color and had a medium filter time. The tow net sample was analyzed qualitatively for microorganisms using phase contrast microscopy. The whole water sample was analyzed quantitatively under 200x phase contrast microscopy. A Hensen Stempel pipette was used to accurately deliver 1ml of sample to a Sedge-wick Rafter chamber. This analysis revealed a total of 2,328,000 cells per Liter. The micro flagellates were found at 72,000 cells/L. The most predominant phytoplankton genus was Guinardia​ spp. at 1,108,000 cells/L. Other representative genera include Dactyliosolen spp., Skeletonema spp., Chaetoceros spp.

 200x phase contrast micrograph of Guinardia.

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