Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing
| ||Fecal Coliform||Enterococci|
Geometric mean ≤50 MPN/100 mL
Geometric mean ≤35 colonies/100 mL
Geometric mean ≤14 MPN/100 mL
|NO ENTEROCOCCI CRITERIA|
Fixed Site Network
Overall, water quality at Phillipsdale Landing was fair to good this week. Weather conditions this week were moderately dry, with 0.41 inches of rainfall recorded at T.F. Green. Blackstone River flows decreased through the week and remaining below historical 16-year median flows. Surface salinity averaged 19.1 ppt and ranged from 11.6 ppt to 24.9 ppt, while bottom salinity averaged 24.9 ppt and ranged from 18.1 ppt to 28.5 ppt. Water temperatures continue to warm, averaging 21.7°C at the surface and 20.9°C on the bottom. Surface temperatures ranged from 16.8°C to 25.7°C, while bottom temperatures ranged from 19.1°C to 23.5°C.
Dissolved oxygen (DO) remained above the hypoxia threshold (2.9 mg/L) for most of the week. Surface DO averaged 6.9 mg/L with a minimum of 3.3 mg/L, while bottom DO averaged 4.2 mg/L, with a minimum of 2.3 mg/L. A maximum duration of hypoxia of approximately four hours occurred early morning on June 20. Chlorophyll readings this week were higher that the previous week, averaging 22.1 ug/L on the surface and 9.8 ug/L on the bottom. Maximum surface chlorophyll readings reached 92.5 ug/L on June 21. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.
Sondes were swapped for routine maintenance on the morning of June 21. Overall, water quality at Bullock Reach was good this week. Surface salinity ranged from 26.1 ppt to 29.2 ppt and averaged 28.0 ppt. Salinity at mid-depth ranged from 27.6 ppt to 30.5 ppt and averaged 29.2 ppt. Bottom salinity ranged from 28.4 ppt to 32.0 ppt and averaged 30.9 ppt. Water column temperatures averaged 20.7°C, 20.2°C, and 19.0°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 18.5°C to 24.8°C, mid temperatures ranged from 18.5°C to 22.4°C, and bottom temperatures ranged from 18.0°C to 20.8°C.
This week, DO averaged 8.2 mg/L at the surface, 7.5 mg/L at mid-depth, and 5.8 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 4.4 mg/L. Chlorophyll concentrations were low, averaging 9.3 µg/L at the surface, 9.9 µg/L at mid-depth, and 5.4 µg/L at the bottom. The maximum chlorophyll this week was 43.8 µg/L measured in surface waters on June 19.
Phytoplankton samples were collected on June 15, 2022 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 21.9°C, salinity was 27.74 psu, and chlorophyll a was 4.8 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a yellow light brown color and had a quick filter time. There was a lot of zooplankton activity and pollen in the sample which was viewed with a stereo-microscope. 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 2,894,000 cells per Liter. The micro flagellates were found at 884,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 1,640,000 cells/L. Pseudo-nitzschia spp. was found in the tow net sample only. Other representative genera include Chaetoceros spp., Leptocylindrus spp. and Heterocapsa spp.
200x phase contrast micrograph of Chaetoceros spp.
Phytoplankton samples were collected on June 1, 2022 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 20.25°C, salinity was 24.67 psu, and chlorophyll a was 5.85 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a yellow-green light brown color and had a medium 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 29,464,000 cells per Liter. The micro flagellates were found at 96,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 29,168,000 cells/L. Pseudo-nitzschia spp. was found in the tow net sample and whole water sample. Some of these diatoms were found dead or oddly shaped, unlike the previous examination. Other representative genera include Leptocylindrus spp. and Chaetoceros spp.
200x phase contrast micrograph of diatoms.
Data were collected on June 22, 2022, while the R/V Monitor was underway collecting bacteria samples in the Seekonk and Providence River estuaries. The average chlorophyll concentrations were good to fair in the areas surveyed. From north to south, average chlorophyll concentrations were as follows: Seekonk River (13.00), Upper Providence River (8.17 µg/L), Edgewood Shoals area (6.35 µg/L), Pawtuxet River area (5.89 µg/L), and Lower Providence River (4.67 µg/L). Overall, chlorophyll ranged between 1.47 and 31.70 µg/L with an overall average of 8.57 µg/L. The chlorophyll data from this date are presented in the map below: