Historical News

August 21 - 27, 2022

Phytoplankton Sampling

​Phytoplankton samples were collected on August 24, 2022 at Bullock Reach and analyzed in the laboratory shortly after collection. It was sunny on Narragansett Bay with calm conditions. Sondes data revealed the surface water temperature was 24.09⁰C, salinity was 23.83 psu, and chlorophyll a was 6.37 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light 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 2,068,000 cells per Liter. The microflagellates were found at 556,000 cells/L. The most predominant phytoplankton genus was Leptocylindrus spp. at 1,084,000 cells/L. Other representative genera include Skeletonema spp., Guinardia spp., and Chaetoceros spp. ​

200x phase contrast image of a loricate ciliate​.​

August 24.PNG

Week of September 4 - 10, 2022

Water Column Clarity

Water clarity was measured at six locations in the Providence River estuary on September 7, 2022. Conditions leading up to the survey were rainy, with 3.77 inches of precipitation recorded in the five days prior. Secchi depth averaged 1.8 meters, compared to 1.3 meters on the previous survey (August 31, 2022). The lowest clarity this week (1.2 meters) was measured at India Point Park, while the greatest clarity (2.4 meters) was measured at Edgewood Yacht Club. There was no clear north-to-south gradient in water clarity among the sites this week. ​

Week of August 28 - September 3, 2022

Water Column Clarity

​Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on August 31, 2022. Rainfall totaling 0.22 inches was recorded at TF Green in the five days prior to the survey, all of which occurred on the day of sampling. Secchi depth averaged 1.3 meters, comparable to the previous survey (August 24, 2022). The lowest clarity this week (0.6 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.6 meters) was measured at Conimicut Point. There was no clear north-to-south gradient in water clarity among the sites this week. ​

Week of September 4 – September 10, 2022

Surface Mapping

​Data were collected on September 7, 2022, while the R/V Monitor was underway collecting nutrient samples in the Providence River estuary. The average chlorophyll concentrations were good in the areas surveyed. From north to south, average chlorophyll concentrations were as follows: Upper Providence River (1.09 µg/L), Edgewood Shoals area (0.61 µg/L), Pawtuxet River area (1.52 µg/L), and Lower Providence River (1.40 µg/L). Overall, chlorophyll ranged between 0.39 and 3.16 µg/L with an overall average of 1.20 µg/L. The chlorophyll data from this date are presented in the map below:

Dataflow 2022-09-07_small.jpg​​

Week of July 24 – 30, 2022

Water Column Profiles

​Water column profiles were conducted at eight locations in the Providence and Seekonk Rivers using a Seabird profiling instrument on July 27, 2022. In the three days leading up to the sampling event conditions were dry, with no recorded rainfall at T.F. Green. Evidence of density stratification was observed at most sites.

Surface salinities among all sites ranged from 22 psu at Phillipsdale Landing to 27 psu at six locations: Bullock Reach Buoy, Conimicut Point, Edgewood Shoals, Edgewood Yacht Club, India Point Park, and Pomham Rocks. Bottom salinities ranged from 28 psu at three locations (Edgewood Shoals, Pawtuxet Cove, & Phillipsdale Landing) to 31 psu at three locations (Bullock Reach Buoy, Conimicut Point, & Pomham Rocks). The warmest temperatures were observed at Pawtuxet Cove, ranging from 26.8°C at the surface to 26°C at the bottom. The lowest surface water temperature (25.3°C) was observed at India Point Park, while the lowest bottom temperature (22.6°C) was observed at Pomham Rocks.

Overall, dissolved oxygen (DO) was low at most sites this week, with sites (Phillipsdale Landing, India Point Park, Pawtuxet Cove, Edgewood Yacht Club, and Edgewood Shoals) falling below the hypoxia threshold (DO<2.9 mg/L). The minimum DO observed was 0.98 mg/L in the middle waters (~2.25 meters) of Phillipsdale Landing. Overall, fluorescence increased from the previous week, with the highest values (19.52 mg/m3) observed near the surface (~0.75 m) at Phillipsdale Landing. 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 back-filled. ​​

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