Historical News

Week of November 26 – December 2, 2017

Bacteria Sampling

​Twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers on November 29, 2017. Five of these stations were additionally sampled for Enterococci bacteria. The 5 days prior to sampling were dry with no precipitation.

Overall, the fecal coliform geometric mean was 14 MPN/100 mL for both rivers, a decrease from the previous sample date. The fecal coliform geomean was higher in the Seekonk River (34 MPN/100 mL) compared to the Providence River (9 MPN/100 mL). The maximum fecal coliform concentration (93 MPN/100mL) was measured in the Seekonk River at Phillipsdale Landing. Fecal coliform concentrations for both rivers were within state guidelines for primary contact, and the Providence River results were also within state guidelines for shellfishing.

Enterococci results were similarly low. The overall Enterococci geometric mean was 10 MPN/100 mL. Concentrations ranged from below detection to 10 MPN/100 mL. These results are within state criteria 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 October 22 - 28, 2017

Phytoplankton Sampling

​Phytoplankton samples were collected at Bullock Reach on October 25, 2017 and analyzed in the laboratory shortly after collection. Water temperature was 17.98°C, salinity was 28.52 psu, and chlorophyll a concentration was low at 2.4 µg/L.

The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light tan color with a quick filter-ability 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 1 mL of sample to a Sedge-wick Rafter chamber.

The total phytoplankton concentration was 417,000 cells/L. The most predominant phytoplankton genus was Chaetoceros at 22,000 cells/L. The flagellates were found at 358,000 cells/L and other representative genera include Skeletonema and Thalassiosira.

pseudonitzschia_10252017.jpg 

200x phase contrast image of Pseudo-nitzschia spp., which was observed in the net tow this week. Certain Pseudo-nitzschia species can form harmful algal blooms.

Week of November 12- 18, 2017

Bacteria Sampling

​Twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers on November 15, 2017. Five of these stations were additionally sampled for Enterococci bacteria. Moderate rainfall of 0.28 inches fell during the 5 days prior to sampling.

After much less rain in comparison to the previous sampling, the overall fecal coliform geometric mean decreased substantially to 25 MPN/100 mL. Concentrations were higher in the Seekonk River (56 MPN/100mL) than in the Providence River (17 MPN/100mL). The maximum fecal coliform concentration (150 MPN/100mL) was observed in the Seekonk River at Phillipsdale Landing. Fecal coliform concentrations for the Providence River were within the state criteria for primary contact, but fecal coliform concentrations in the Seekonk and Providence Rivers were not within state criteria for shellfishing.

Overall, the Enterococci geometric mean for the Seekonk and Providence Rivers was 14 MPN/100 mL, also a large decrease from the previous sampling date. Enterococci concentrations ranged from below detection at four stations to 52 MPN/100 mL at the Point Street Bridge station. These results are within the state criteria 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 October 29 – November 4, 2017

Bacteria Sampling

​Nineteen stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers on November 1, 2017. Four of these stations were additionally sampled for Enterococci bacteria. A total of 2.34 inches of rain fell during the 5 days prior to sampling.

The fecal coliform geometric mean was 1,061 MPN/100mL, a large increase from the previous sampling date. The geomean was similar in both rivers with a value of 1,086 MPN/100 mL in the Seekonk and a value of 1,048 MPN/100 mL in the Providence River. The maximum fecal coliform geomean of 4,300 MPN/100 mL was observed at Collier Point Park in the Providence River. Fecal coliform concentrations for the Providence River were not within state criteria for primary contact or shellfishing.

The overall Enterococci geometric mean for the Seekonk and Providence Rivers was 851 MPN/100mL, similarly an increase from the previous week. The maximum value of 1470 MPN/100 mL was observed at the South Field’s Point East station. These results do not fall within state criteria for primary contact and shellfishing.

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 December 3 – 9, 2017

Water Column Clarity

​Water clarity was measured at five locations in the Providence and Seekonk Rivers on December 6, 2017. A total of 0.79 inches of rain fell on December 5th and the early morning of December 6th, which may have contributed to decreased water clarity. Average water clarity decreased by 1.1 m from the previous sampling to 1.6 m. Secchi depth ranged from 1.2 m at Edgewood Yacht Club to 2.2 m at Pomham Rocks, showing no evidence of a north to south gradient. The largest decrease of 2.2 m was observed at Bullock Reach.

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