Snapshot of the Bay

Historical News

Week of February 23 - 29, 2020

Nutrients Sampling

Nutrient samples were collected at fourteen local and border river stations on February 27, 2020; bay sampling was not conducted this week due to a small-craft advisory. Approximately 0.94 inches of rain was recorded over the five days prior, most of which fell during the morning of sampling. The highest nitrogen concentrations occurred at the Ten Mile River at Central Avenue site. At this site, concentrations of total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were 1,915 ppb, 2,010 ppb, and 1,699 ppb, respectively (average of duplicates). The lowest TN (627 ppb) and DIN (197 ppb) concentrations occurred at the Coles River at Milford Road, while the lowest TDN (336 ppb) occurred at the Palmer River at Route 6.

Further nutrients sampling of the bay and rivers has been temporarily suspended in order to comply with local health and safety guidance regarding social distancing as part of the ongoing COVID-19 response.

Week of February 9 - 15, 2020

Nutrients Sampling

Nutrient samples were collected at seven local river stations and in surface and bottom waters of seven bay stations on February 12, 2020. Approximately 0.83 inches of rain was recorded over the five days prior to sampling, half of which fell the day before the survey. Among the river stations sampled, the highest nitrogen concentrations occurred at the Ten Mile River at Roger Williams Avenue. At this site, concentrations of total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were 1,890 ppb, 2,560 ppb, and 2,235 ppb, respectively. The lowest nitrogen concentrations were measured at the Moshassuck River at Higginson Avenue site, where TN was 621 ppb, TDN was 651 ppb, and DIN was 511 ppb.

Among the bay stations sampled, the greatest surface concentrations of TN (1,860 ppb), TDN (2,060 ppb), and DIN (1,825 ppb) occurred at Phillipsdale Landing, the northernmost bay site sampled. The lowest TN concentration (516 ppb) occurred at Edgewood Yacht Club, while the lowest TDN (181 ppb) and DIN (222 ppb) occurred at Conimicut Point.

Results from sampling on February 27 and March 11 are pending analysis. Further nutrients sampling of the bay and rivers has been temporarily suspended in order to comply with local health and safety guidance regarding social distancing as part of the ongoing COVID-19 response.

Week of March 08 – 14, 2020

Water Column Clarity

Water clarity was measured at five locations in the Providence River on March 11, 2020. In the three days prior to the survey there were no recorded precipitation, and water clarity increased compared to the previous survey day. Overall, sites surveyed this week averaged 2.7 m Secchi depth, compared to 1.9 m on March 4. The lowest clarity was measured at Edgewood Yacht Club (2.0 m), while the greatest clarity was measured at Bullock Reach (3.4 m). Overall, a gradient of increasing clarity among the sites from north to south was observed.

Week of March 8-14, 2020

Phytoplankton Sampling

Phytoplankton samples were collected on March 11, 2020 at Bullock’s Reach and analyzed in the laboratory shortly after collection. It was a sunny and brisk day with a north-northwest wind, less than 10 knots, on Narragansett Bay. Sondes data revealed the surface water temperature was 7.16^oC, salinity was 27.11 psu, and chlorophyll a was 1.7 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a deep brown 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 1,559,000 cells per Liter. The most predominant phytoplankton was Skeletonema spp.at 1501,000 cells/L. Representative genera include Thalassiosira spp. and Chaetoceros spp.

200x phase contrast image of the phytoplankton

phytoplankton 3.11.2020.jpg

Week of March 8 - 14, 2020

Fixed Site Network

Phillipsdale Landing

Water quality was good this week at Phillipsdale Landing. Approximately 0.33 inches of precipitation was recorded towards the end of the week, on March 13.

Water column salinity was greater than the previous week. Surface salinity averaged 14.4 ppt and ranged from 3.5 to 23.5 ppt. Surface salinity declined over the course of the week, particularly in response to the rainfall on March 13. Bottom salinity also exhibited a decreasing trend, averaging 20.6 ppt and ranging from 7.1 ppt to 28.0 ppt.

Average surface and bottom water temperatures were greater than those measured last week. Surface water temperatures averaged 7.9°C and ranged from 4.4°C to 10.1°C, while bottom waters averaged 7.3°C and ranged from 5.2°C to 9.5°C. Water temperatures at both depths increased over the course of the week.

Dissolved oxygen (DO) concentrations remained above the hypoxia threshold (>2.9 mg/L) at both depths. Surface DO averaged 11.7 mg/L, with a minimum of 10.4 mg/L, and bottom DO averaged 11.3 mg/L, with a minimum of 9.8 mg/L. Surface chlorophyll averaged 9.2 ug/L and generally increased over the course of the week, with a maximum concentration of approximately 30 ug/L recorded on March 13.

Bullock Reach

The Bullock Reach sondes were removed for the season on November 19.