Historical News

Week of August 22 – August 28, 2021

Phytoplankton Sampling

​Phytoplankton samples were collected on August 25, 2021 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 24.94°C, salinity was 21.18 psu, and chlorophyll a was 15.70 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light tan 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 4,628,000 cells per Liter. The flagellates were found at 2,236,000 cells/L. The most predominant phytoplankton genus was Leptocylindrus spp. at 2,092,000 cells/L. Other representative genera include Prorocentrum spp., Skeletonema spp., Chaetoceros spp., and Thalassiosira spp.

200x phase contrast micrograph of Akashiwo sanguineum.

Akashiwo sanguineum 8.25.21.jpg

Week of August 22 - 28, 2021

Water Column Clarity

​Water clarity was measured at eight locations in the Providence and Seekonk River estuaries on August 25, 2021. Conditions this week were wet, with 0.51 inches of rainfall recorded at T.F. Green three days prior to the survey on August 22, and an additional 0.40 inches on August 23. Despite the rain, there was a slight increase in water clarity since the previous week’s survey. Overall, sites averaged 2.0 meters Secchi depth, compared to 1.9 meters on August 18, 2021. The lowest clarity (1.7 meters) was measured at Phillipsdale Landing, while the highest (2.3 meters) was measured at Edgewood Shoal. There was no gradient of increasing clarity from north to south this week.​

Week of August 15 - 21, 2021

Bacteria Sampling

Twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers on August 18, 2021. Five of these stations were also sampled for enterococci bacteria. Conditions preceding sampling were relatively dry, and 0.14 inches of precipitation occurred five days prior to sampling.

The geometric mean of fecal coliform results for all sites was 26 MPN/100 mL, compared to a geometric mean of 40 MPN/100 mL the prior sampling event. Seekonk River sites generally had higher counts than Providence River sites (geometric means of 161 and 11 MPN/100 mL, respectively). The maximum count (430 MPN/100 mL) was measured at Bishop Point in the Seekonk River. Overall, fecal coliform results from the Providence River were within the state criteria for primary contact and shellfishing, while fecal coliform results from the Seekonk River exceeded state criteria for primary contact and shellfishing.

Enterococci results decreased from an overall geometric mean of 17 MPN/100 mL during the previous sampling event to a geometric mean of 13 MPN/100 mL. Results were <10 MPN/100 mL at all sites except for Point St. Bridge. At Point St. Bridge, the enterococci result was 52 MPN/100 mL. Enterococci results from both rivers were within state primary contact standards.

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

Week of August 15 - 21, 2021

Water Column Clarity

​Water clarity was measured at six locations in the Providence and Seekonk River estuaries on August 18, 2021. Conditions this week were dry, with no rainfall recorded at T.F. Green over the three days prior to the survey. There was a slight increase in water clarity since the previous week’s survey. Overall, sites averaged 1.9 meters Secchi depth, compared to 1.8 meters on August 11, 2021. The lowest clarity (1.3 meters) was measured at Phillipsdale Landing, while the highest (2.9 meters) was measured at Conimicut Point. Overall, a gradient of increasing clarity from north to south was observed among sites. ​

Week of August 8 - 14, 2021

Water Column Clarity

​Water clarity was measured at six locations in the Providence River on August 11, 2021. Conditions this week were mostly dry, with just 0.02 inches of rainfall recorded at T.F. Green over the three days prior to the survey. There was a slight increase in water clarity since the prior week’s survey. Overall, sites averaged 1.8 meters Secchi depth, compared to 1.5 meters on August 4, 2021. The lowest clarity (1.2 meters) was measured at Pawtuxet Cove, while the highest (2.8 meters) was measured at Conimicut Point. Overall, a gradient of increasing clarity from north to south was observed among most sites. ​

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