Historical News

Week of November 8 - 14, 2020

Fixed Site Network

Phillipsdale Landing

Phillipsdale Landing sondes were changed out for routine maintenance during the morning of November 10. Water quality at this site was good this week. Precipitation totaled 0.31 inches at TF Green, with most of the rainfall (0.22 inches) falling on November 13. In response to a relatively dry week, freshwater discharge from the Blackstone River decreased from the previous week. This week, salinity at the surface averaged 13.8 ppt and ranged from 3.3 ppt to 26.3 ppt. Bottom salinity averaged 24.4 ppt and ranged from 16.6 ppt to 28.4 ppt. Both surface and bottom water temperatures increased slightly from the previous week, averaging 13.0°C and 13.1°C, respectively. Surface temperatures ranged from 10.2°C to 15.4°C, while bottom temperatures ranged from 12.3°C to 14.1°C.

Dissolved oxygen (DO) remained above the hypoxia threshold (2.9 mg/L) in surface and bottom waters this week. Surface DO averaged 8.3 mg/L, with a minimum of 6.7 mg/L, while bottom DO averaged 6.5 mg/L, with a minimum of 5.2 mg/L. Chlorophyll concentrations continue to be low through the week, averaging 2.1 ug/L at the surface and 1.9 ug/L at the bottom. Maximum surface chlorophyll concentrations reached 4.3 ug/L on November 12. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location.

Bullock Reach

Following the deployment of the sondes on November 3, the mid-sonde salinity data are not reported in this summary due to suspected probe drift. Water quality was good this week at Bullock Reach. Surface salinity averaged 26.7 ppt and ranged from 23.1 ppt to 29.5 ppt, while bottom waters averaged 30.8 ppt and ranged from 29.2 ppt to 31.5 ppt. Temperatures averaged 13.2°C, 12.8°C, and 12.4°C at the surface, mid, and bottom waters, respectively. Surface temperatures ranged from 12.0°C to 14.4°C, mid temperatures ranged from 11.8°C to 14.1°C, and bottom temperatures ranged from 11.7°C to 13.2°C.

Dissolved oxygen (DO) concentrations remained above the hypoxia threshold (2.9 mg/L) throughout the water column. Surface Do averaged 8.5 mg/L, while mid DO averaged 8.1 mg/L. Bottom DO averaged 7.7 mg/L, with a minimum of 7.2 mg/L. Chlorophyll concentrations were low this week, averaging 3.9 ug/L at the surface, 2.3 ug/L in mid-depth waters, and 3.2 ug/L in bottom waters. The maximum water column chlorophyll concentration was 10.2 ug/L, measured at the surface on November 12.

Week of December 6 - 12, 2020

Phytoplankton Sampling

Phytoplankton samples were collected on November 4, 2020 at Bullock's Reach and analyzed in the laboratory shortly after collection. It was a windy and brisk day on Narragansett Bay. Sondes data revealed the surface water temperature was 10.23oC, salinity was 25.96 psu, and chlorophyll a was 2.0 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light tan color and had a short filter time. The tow net sample was analyzed qualitatively for microorganisms using 100x 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 222,000 cells per Liter. The flagellates were found at 16,000 cells/L. The most predominant phytoplankton was Skeletonema spp. at 105,000 cells/L. Representative genera include Leptocylindrus spp., Thalassiosira spp. and pennate diatoms.

200x phase contrast micrograph of a pennate diatom

pennate diatom 12.2020.jpg 

Week of November 1 - 7, 2020

Fixed Site Network

Phillipsdale Landing

Water quality was good this week at Phillipsdale Landing. Precipitation totaled 0.73 inches at TF Green this week, with all the rainfall occurring on November 1. Blackstone River flows increased at the beginning of the week in response to the precipitation, with freshwater flows reducing through the week. This week, surface salinity averaged 10.1 ppt and ranged from 2.0 ppt to 20.4 ppt. Bottom salinity averaged 22.2 ppt and ranged from 4.9 ppt to 29.3 ppt. Both surface and bottom water temperatures continued their seasonal decline, averaging 10.9°C and 12.8°C, respectively. Surface temperatures ranged from 7.2°C to 13.6°C, while bottom temperatures ranged from 8.2°C to 15.3°C.

Dissolved oxygen (DO) remained above the hypoxia threshold (2.9 mg/L) in surface and bottom waters this week. Surface DO averaged 9.4 mg/L, with a minimum of 6.6 mg/L, and bottom DO averaged 6.9 mg/L, with a minimum 5.4 mg/L. Chlorophyll concentrations were low, averaging 2.0 ug/L at the surface and 1.6 ug/L at the bottom. Maximum surface chlorophyll concentrations reached 4.4 ug/L, measured on November 1. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location.

Bullock Reach

Bullock Reach sondes were changed out for routine maintenance during the morning on November 3. Following the deployment of the sondes, the mid-sonde salinity data are not reported in this summary due to suspected probe drift.  Water quality was good this week at Bullock Reach. Surface salinity averaged 27.6 ppt and ranged from 24.0 ppt to 30.1 ppt, while bottom waters averaged 30.7 ppt and ranged from 26.8 ppt to 32.8 ppt. Temperatures averaged 12.0°C at the surface, and 12.1 ppt at the mid depth and bottom waters. Surface temperatures ranged from 10.0°C to 13.8°C, mid depth temperatures ranged from 10.2°C to 14.0°C, and bottom temperatures ranged from 10.3°C to 14.4°C.

Dissolved oxygen (DO) concentrations remained above the hypoxia threshold (2.9 mg/L) throughout the water column. Surface DO averaged 8.3 mg/L for the week, while mid and bottom DO averaged 8.0 mg/L and 7.7 mg/L, respectively. Chlorophyll concentration remained low at this site, averaging 1.4 ug/L at the surface and mid waters, while bottom waters averaged 2.0 ug/L. The maximum water chlorophyll concentrations was 7.7 ug/L, measured in surface waters on November 1.

Week of November 22 - 28, 2020

Bacteria Sampling

​Twenty stations in the Providence and Seekonk Rivers were sampled for fecal coliform on November 25, 2020; five of these stations were also sampled for enterococci bacteria. Weather preceding this sampling day was wet, with 1.37 inches of precipitation recorded over the two days prior. 

Fecal coliform counts increased compared to the prior survey in late October. Counts were higher at the Seekonk River sites than the Providence River, with geometric means of 457 MPN/100 mL and 338 MPN/100 mL, respectively. The maximum count, 2,300 MPN/100 mL occurred in samples from three sites – Bishop Point in the Seekonk River, Collier Point Park and Off FP Outfall in the Providence River. Overall, fecal coliform results from both the Providence and Seekonk Rivers exceeded state primary contact and shellfishing standards. 

Enterococci results also increased from the previous sampling event, from an overall geometric mean of 19 MPN/100 mL to 237 MPN/100 mL. Enterococci results at all sites ranged from 75 MPN/100 mL at Conimicut Point to 650 MPN/100 mL at Point St. Bridge. As with fecal coliform, enterococci results exceeded the state standards for primary contact.

Please note: the results of NBC's fecal coliform and enterococci monitoring are for informational/research purposes only and are not intended to suggest official state compliance with bathing or shellfishing standards.

Week of November 22 - 28, 2020

Water Column Clarity

​Water clarity was measured at seven stations in the Providence and Seekonk Rivers on November 25, 2020. Heavy rainfall of 1.37 inches was recorded at TF Green two days prior to the survey, likely impacting clarity in the Bay. Overall, Secchi depths averaged 3.02 m, compared to 3.91 m on November 4; note that comparisons to the survey on November 18 are limited, since only three sites were visited on that day. The greatest clarity was observed at Edgewood Yacht Club, at 3.70 m. This was the only site that exhibited an increase in clarity compared to previous surveys: 2.70 m on November 4 and 2.97 m on November 18. The greatest decrease in clarity occurred at Conimicut Point; clarity at this site decreased by 2.70 m since the survey on November 4. The lowest water clarity this week was observed at India Point Park, at 2.50 m. There was a weak spatial gradient in clarity this week, with slightly higher clarity at southern sites than northern.​

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