News – Page 18 – Narrabay

February 26-March 1, 2023

On March 1, fifteen stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers. Four of these stations were also sampled for enterococci bacteria. Precipitation in the five days prior to sampling totaled 0.67 inches as recorded at TF Green.

The geometric mean of fecal coliform results for all sites was 11 MPN/100 mL compared to 25 MPN/100 mL on January 18, 2023. Overall, bacteria counts were lower in the Providence River this week than during the previous sampling event on January 18. The Providence River geomean this week was 10 MPN/ 100 mL. Only one site was sampled this week in the Seekonk River (43 MPN/100 mL at Crook Point). The maximum count (390 MPN/100 mL) was measured at Point St. Bridge in the Providence River.

Enterococci results had an overall geometric mean of 10 MPN/100 mL. Enterococci results ranged from non-detect at South FP East, Gaspee Point, and Conimicut Point to 52 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 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.

February 19-25, 2023

On Wednesday, February 22nd, the crew of the R/V Monitor was out on the upper Bay collecting nutrients and plankton samples, taking Secchi Disk water clarity measurements, conducting water column profiles using the Seabird instrument, and conducting real-time surface mapping of water quality parameters, including dissolved oxygen, chlorophyll, water temperature, salinity, and pH, all in an effort to document water quality improvements associated with NBC construction projects. Jeff captained the boat while monitoring professionals Fern and Michael collected the samples and data. The day started sunny but turned cloudy by late morning with cool temperatures all day. The featured photo shows a cargo ship at ProvPort.

February 19-25, 2023

Water clarity was measured at seven locations in the Providence River estuary on February 22. Rainfall totaling 0.52 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 2.8 meters, compared to 2.7 meters on the previous survey (January 18). The lowest clarity this week (2.6 meters) was measured at India Point Park, while the greatest clarity (3.0 meters) was measured at Conimicut Point. There was no clear north-to-south gradient in water clarity among the sites this week.

February 19-25, 2023

Phytoplankton samples were collected on February 23, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 5.49⁰C, salinity was 26.72 psu, and chlorophyll a was 3.26 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a dark yellow/golden brown color and had a quick 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 7,824,000 cells per Liter. The most predominant phytoplankton genus was Skeletonema spp. at 7,408,000. Representative genera in the tow net sample include Thalassiosira spp., Asterionellopsis spp., and Leptocylindrus spp.

200x phase contrast image of diatomic phytoplankton.

February 19-25, 2023

Water column profiles were conducted at seven locations in the Providence River Estuary on February 22, 2023 using a Seabird Electronics profiler. In the three days leading up to the survey, 0.17 inches of rainfall were recorded at T.F. Green. Evidence of moderate density stratification was observed at most sites this week, with Pawtuxet Cove showing signs of strong stratification and Bullock Reach and Edgewood Shoals showing signs of weak stratification.

Surface salinities ranged from 20 psu at Pawtuxet Cove to 26 psu at Bullock Reach Buoy and Edgewood Shoal. Bottom salinities ranged from 27 psu at Pawtuxet Cove to 30 psu at Conimicut Point. The coolest water temperatures ranged from 5.4°C at the surface of Conimicut Point to 5.7°C at bottom of India Point Park. The warmest surface water temperature (5.9°C) was observed at Pawtuxet Cove and Edgewood Shoal, while the warmest bottom temperature (6.0°C) was observed at Pawtuxet Cove and Conimicut Point.

Dissolved oxygen (DO) conditions remained above the hypoxia threshold (2.9 mg/L) at all sites this week; the lowest DO observed was approximately 9.4 mg/L in the bottom waters at India Point Park. Overall, fluorescence was generally low, with the highest value (9.23 mg/m³) observed near the middle of the water column (4.0 meters deep) at Edgewood Yacht Club. Please note numerical fluorescence data were not posted from 2020 to 2021 due to a QC issue. This issue has been resolved and fluorescence data from 2020 and 2021 will be backfilled.

February 19-25, 2023

Fixed-Site Network – February 19-25, 2023

Phillipsdale Landing

Sondes were swapped for routine maintenance on the morning of February 23rd. Depth data had been lost by the sondes on February 15th but was restored with the deployment of new sondes at the swap. Data in this week’s summary should be interpreted with caution due to the lack of depth data to confirm sonde positioning for most of the week.

Weather conditions this week included light to moderate rain or snow every day, totaling 0.62 inches as recorded at TF Green. The largest rain event was on February 23rd with 0.32 inches. Blackstone River flows showed a slight increase after this rain event but remained below the 18-year median flow rates. Surface salinity this week averaged 12.6 ppt and ranged from 4.1 ppt to 22.9 ppt. At the bottom, salinity averaged 21.0 ppt and ranged from 8.7 ppt to 27.5 ppt. Temperatures at the surface averaged 5.6°C, ranging 2.9°C – 8.0°C. At the bottom, temperatures averaged 5.8°C and ranged 4.1°C – 6.7°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L throughout the week. Surface DO averaged 10.8 mg/L and ranged 9.2 – 12.4 mg/L. Bottom DO concentrations averaged 10.0 mg/L and ranged from 8.9 mg/L to 11.6 mg/L. Chlorophyll readings generally remained low, averaging 1.5 ug/L at the surface and 4.2 ug/L at the bottom. The maximum chlorophyll reading this week was 35.5 ug/L at the bottom on February 23rd. 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.

February 19-25, 2023

Nutrient samples were collected from fifteen local and border river stations, and eight bay stations on February 22nd, 2023. The Edgewood Shoal bay station was sampled at surface and bottom while all other bay stations were only sampled at the surface. In the five days prior to sampling, 0.42 inches of rainfall was 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 at Central Ave. The TN, TDN, and DIN were 2,680 ppb, 2,670 ppb, and 2,410 ppb respectively. The lowest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Palmer River at Route 6. The TN, TDN, and DIN were 606 ppb, 387 ppb, and 171.9 ppb, respectively.

Among the bay stations sampled, the highest surface TN, TDN, and DIN concentrations was observed at Phillipsdale Landing as 1,740 ppb, 1,610 ppb, and 1,326 ppb, respectively. The lowest surface TN (551 ppb), TDN (289 ppb) and DIN (166 ppb) were observed at Bullock Reach Buoy. Chlorophyll a concentrations at the bay stations have increased (averaging 5.54 ug/L) since all these sites had previously been sampled in January. The maximum result (10.65 ug/L) occurred at Bullock Reach Buoy.

Data from additional sampling dates (typically every two weeks) are pending analysis and writeup

February 19-25, 2023

Surface chlorophyll data were collected on February 22, 2023 while the R/V Monitor was underway collecting nutrient samples in the Providence River estuary. The average chlorophyll concentrations were categorized as good in the areas surveyed. Overall, chlorophyll ranged between 0.54 and 5.19 µg/L with an average of 1.95 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

February 12-18, 2023

Phillipsdale Landing

The surface sonde deployed on February 7th failed to log data internally, and so there is a data gap until DCP communications were restored this week on February 15th. Unfortunately, restoration of this connection resulted in lost depth data for both sondes through the end of the deployment on February 23rd. Data in this week’s summary should be interpreted with caution due to the gap in surface data and lack of depth data to confirm sonde positioning at both depths.

Weather conditions this week were mostly dry, with just 0.25 inches of rainfall on February 17th and trace rainfall on the 13th and 16th. Blackstone River flows continued to decline all week and fell below the 18-year median flow rates for this time of year. Surface salinity from the latter half of the week averaged 7.4 ppt and ranged from 2.0 ppt to 20.3 ppt. At the bottom, salinity averaged 20.6 ppt and ranged from 5.2 ppt to 29.8 ppt. Temperatures at the surface (latter half of the week) averaged 6.4°C, ranging 4.4°C – 8.1°C. At the bottom, temperatures averaged 5.4°C and ranged 4.6°C – 7.0°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L throughout the week. Surface DO (latter half of the week) averaged 11.3 mg/L and ranged 10.1 – 12.4 mg/L. Bottom DO concentrations averaged 9.9 mg/L and ranged from 8.8 mg/L to 12.3 mg/L. Chlorophyll readings generally remained low, averaging 0.8 ug/L at the surface (latter half of the week) and 2.9 ug/L at the bottom. Maximum chlorophyll at the surface reached just 6.8 ug/L in the data available this week. At the bottom, chlorophyll hit an isolated maximum of 25.1 ug/L on February 17th, though this does not appear to be related to phytoplankton activity as there were no concurrent changes to pH or DO. 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.