May 14-20, 2023

Nutrient samples were collected from seven river stations on May 17th and seven bay stations on May 18th. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, there were 0.01 inches of rainfall recorded at T.F. Green. 

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) concentrations were observed at Ten Mile River @ Central Ave. (TN = 1,360 ppb, TDN = 1,310 ppb, DIN = 1,080 ppb). The lowest TN, TDN, and DIN concentrations were observed at Woonasquatucket River @ Manton Ave. Bridge (TN and TDN = 743 ppb, DIN = 538 ppb, average of duplicates).

Among the bay stations sampled, the highest surface TN, TDN, and DIN concentrations were observed at Pawtuxet Cove (TN = 1,110 ppb, TDN = 1,010 ppb, DIN = 778 ppb). The lowest surface TN and DIN concentrations were observed at Conimicut Point (TN = 439 ppb, DIN = 13.0 ppb), while the lowest surface TDN concentration was observed at Bullock Reach Buoy (149 ppb, average of duplicates). Chlorophyll a concentrations at the surface bay stations were relatively low, averaging 9.61 μg/L across all sites with a maximum of 14.0 μg/L (average of duplicates) at Bullock Reach Buoy.

The next scheduled sampling date is May 31, 2023.

May 14-20, 2023

Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on May 18, 2023 using a Seabird Electronics profiler. There was no precipitation recorded at T.F. Green in the three days leading up to the survey. Despite the lack of recent rainfall, Phillipsdale Landing still showed strong density stratification and Bullock Reach Buoy showed moderate density stratification; all other sites were well mixed to weakly 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 6.62 mg/L near the middle of the water column at Pomham Rocks. Fluorescence was low to moderately elevated, with the highest value (10.09 mg/m3) observed 2.5 m deep at Conimicut Point West.

May 14-20, 2023

​Phillipsdale Landing

Overall, water quality at Phillipsdale Landing was fair to good this week. Weather conditions were wet this week, with a total of 3.02 inches on March 20th, recorded at T.F. Green. Blackstone River flow declined over the course of the week only to increase at the end with the March 20th storm. 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. Temperatures increased this week, averaging 16.6°C at the surface and 15.0 at the bottom. Surface temperatures ranged from 13.8°C to 20.0°C, while bottom temperatures ranged from 12.6°C to 17.8°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 for a few hours on the night of May 17th. Surface DO averaged 9.1 mg/L and ranged 6.7 – 11.4 mg/L. Bottom DO concentrations averaged 6.2 mg/L and ranged from 0.5 mg/L to 10.5 mg/L. Chlorophyll readings rose from the previous week, averaging 12.9 ug/L at the surface and 26.2 ug/L at the bottom. Maximum chlorophyll at the surface reached 107.5 ug/L on May 15th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location. Also, please note that portions of chlorophyll data from the surface and bottom sondes from May 14th – 20th are not included in the summary above due potential fouling interference which is common at this site.

Bullock Reach 

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

May 7-13, 2023

​Surface chlorophyll data were collected on May 10, 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 areas surveyed. Overall, chlorophyll ranged between 0.66 and 6.74 µg/L with an average of 1.61 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

May 7-13, 2023

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on May 10. Rainfall totaling 0.17 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 1.9 meters, compared to 1.4 meters on the previous survey (May 3). The lowest clarity this week (1.5 meters) was measured at Bullock Reach while the greatest clarity (2.1 meters) was measured at Conimicut Point, India Point Park, and Point St. Bridge. There was a general north-to-south gradient of decreasing water clarity among the sites this week.​

May 7-13, 2023

On May 10, 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 0.26 inches as recorded at TF Green.

The geometric mean of fecal coliform results for all sites was 23 MPN/100 mL compared to 29 MPN/100 mL on April 26, 2023. Overall, bacteria counts were lower in the Seekonk River and Providence River this week than during the previous sampling event on April 26. Fecal coliform counts were 40 MPN/ 100 mL in the Seekonk River and 18 MPN/ 100 mL in the Providence River. The maximum count (430 MPN/100 mL) was measured at Point St. Bridge in the Providence River.

Enterococci results had an overall geometric mean of 14 MPN/100 mL. Enterococci results were non-detect at all sites except the Point St. Bridge site with a measurement of 134 MPN/100 mL.​

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 7-13, 2023

​Phillipsdale Landing

The sondes were deployed on May 9th as a new setup was devised to circumvent the dock. Also, please note that the depth sensor was malfunctioning for the first day of deployment. Due to the sondes being deployed on May 9th, we only have data from a portion of the month. Overall, water quality at Phillipsdale Landing was good this week. Weather conditions this week included light rain, with a total of 0.27 inches as recorded at T.F. Green. The Blackstone River flow declined over the course of the week from its increased flow due to the May 2nd storm. Surface salinity remained well below bottom salinity. Salinity at the surface averaged 6.3 ppt and ranged from 3.4 ppt to 10.4 ppt. At the bottom, salinity averaged 19.5 ppt and ranged from 6.9 ppt to 27.9 ppt. Temperatures this week averaged 17.6°C at the surface and 14.7°C at the bottom. Surface temperatures ranged from 14.2°C to 21.3°C, while bottom temperatures ranged from 12.7°C to 17.9°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L throughout the week. Surface DO did drop slightly compared to the last reading in April, averaging 9.4 mg/L and ranging 7.9 – 10.9 mg/L. Bottom water DO concentration averaged 6.9 mg/L and ranged from 5.1 mg/L to 9.5 mg/L. Chlorophyll remained low, averaging 3.4 ug/L at the surface and 5.1 ug/L at the bottom. Maximum surface chlorophyll readings reached 30.3 ug/L, recorded on the morning of May 13th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location. 

Bullock Reach 

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

April 30-May 6, 2023

Phytoplankton samples were collected on May 3, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 13.37⁰C, salinity was 6.62 psu, and chlorophyll a was 1.86 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light brown color and had a quick filter time. There was lots of zooplankton activity in today’s sample. 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 214,000 cells per Liter. The micro flagellates were found at 7,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 87,000 cells/L. Representative genera in the tow net sample include Thalassionema spp., Leptocylindrus spp. and pennate diatoms.

 200x phase contrast micrograph of Fragilaria spp.

April 30-May 6, 2023

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on May 3. Rainfall totaling 3.64 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 1.4 meters, compared to 2.5 meters on the previous survey (April 19). The lowest clarity this week (0.9 meters) was measured at India Point Park while the greatest clarity (1.7 meters) was measured at Pomham Rocks and Pawtuxet Cove. There was a general north-to-south gradient of increasing water clarity among the sites this week.​

April 20-May 6, 2023

Nutrient samples were collected from 14 river stations and eight bay stations on May 3rd. Edgewood Shoal was sampled at the surface and bottom; all other bay stations were sampled at the surface only. In the five days prior to sampling, there were 3.64 inches of rainfall recorded at T.F. Green due to some heavy rain events on April 29th and 30th. 

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) concentrations were observed at Ten Mile River @ Central Ave. (TN and TDN = 1,020 ppb, DIN = 686 ppb). The lowest TN and TDN concentrations were observed at Blackstone River @ Stateline (TN = 565 ppb, TDN = 512 ppb), while the lowest DIN was observed at Palmer River @ Rt. 6 (69.9 ppb).

Among the bay stations sampled, the highest surface TN concentration was observed at Edgewood Shoal (895 ppb), while the highest surface TDN and DIN were observed at Phillipsdale Landing (TDN = 798 ppb, DIN = 507 ppb). The lowest surface TN was observed at Pawtuxet Cove (753 ppb), the lowest surface TDN was observed at Pomham Rocks (662 ppb), and the lowest surface DIN was observed at India Point Park (437 ppb, average of duplicates). Chlorophyll a concentrations at the surface bay stations were relatively low, averaging 2.33 μg/L across all sites with a maximum of 4.10 μg/L at Edgewood Shoal.

The next scheduled sampling date is May 17, 2023.​

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