Historical News

Week of June 26 - July 2, 2022

Phytoplankton Sampling

​Phytoplankton samples were collected on June 29, 2022 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 22.75°C, salinity was 24.67 psu, and chlorophyll a was 14.04 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 1,371,000 cells per Liter. The micro flagellates were found at 1,246,000 cells/L. The most predominant phytoplankton genus was Chaetoceros spp. at 42,000 cells/L. Other representative genera include Scrippsiella spp., and Heterocapsa spp. 

200x phase contrast image of Gonyaulax spp.

7_27_2022.PNG 

Week of July 17 - 23, 2022

Fixed Site Network

Phillipsdale Landing

There were some data quality issues this week at Phillipsdale. The surface sonde became tangled and out of position for several hours at a time on July 18, 19, and 20; data where the sonde was out of position were excluded from this summary. In addition, there is evidence that the conductivity and temperature sensor failed during the evening of July 22, impacting most parameters; these data were also excluded from the summary here. Water quality at Phillipsdale Landing was poor to fair this week. The weather remains dry, with only trace rainfall on July 18 and 20, and 0.17 inches on July 19 recorded at T.F. Green. Blackstone River flows increased following the rain on July 19 but remained below 17-year median flow rates overall. Salinity at the surface averaged 19.4 ppt and ranged 8.4 ppt – 24.4 ppt. At the bottom, salinity averaged 23.4 ppt and ranged 16.5 ppt – 27.5 ppt. Temperatures warmed this week, averaging 26.7°C at the surface and 25.8°C at the bottom. Surface temperatures ranged from 24.8°C to 30.0°C, while bottom temperatures ranged from 24.1°C to 28.4 °C.

Dissolved oxygen (DO) remains low at Phillipsdale, particularly in the bottom waters which were hypoxic for much of the week (i.e., DO < 2.9 mg/L). Bottom water DO concentration averaged 2.2 mg/L for the week and ranged from 0.1 mg/L to 8.0 mg/L. The longest duration of hypoxic conditions was nearly 48 hours, beginning the afternoon of July 22 and lasting until the afternoon of July 24. During this time DO averaged 0.69 mg/L. Surface DO was higher, averaging 6.1 mg/L and ranging 0.7 mg/L – 17.7 mg/L for the week. Surface waters were hypoxic for 1.75 hours on July 21 (average DO 1.62 mg/L during that time), and during isolated shorter periods on other days (though note there are also substantial data gaps in the record this week). Chlorophyll concentrations remained elevated, averaging 26.1 ug/L at the surface and 14.4 ug/L at the bottom. Maximum surface chlorophyll readings reached 216 ug/L on July 21. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach Buoy

Sondes were swapped for maintenance during the morning of July 19. Please note there are some indications that the turbidity data for the surface sonde deployed July 7 and retrieved July 19 are problematic; use these turbidity data with caution. Water quality was fair at Bullock Reach this week. Salinity averaged 28.3 ppt, 29.7 ppt, and 31.4 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 21.0-29.9 ppt, mid salinity ranged 28.5-30.5 ppt, and bottom salinity ranged 29.7-32.7 ppt. Temperatures increased this week. Surface temperature averaged 26.0°C and ranged from 24.1°C to 29.4°C. Mid temperatures averaged 25.2°C and ranged from 23.6°C to 27.5°C. Bottom temperatures averaged 23.9°C and ranged from 22.6°C to 25.7°C. 

DO concentrations at Bullock Reach declined this week compared to last. Surface DO averaged 7.4 mg/L and ranged 4.9-11.5 mg/L. In the mid waters, DO averaged 5.8 mg/L and ranged 3.4-8.0 mg/L. At the bottom, DO averaged 4.2 mg/L and ranged 2.5-6.2 mg/L. Hypoxic conditions below 2.9 mg/L DO in bottom waters occurred on July 23, lasting for a maximum duration of 3.5 hours. Chlorophyll readings were slightly elevated (e.g., 10-30 ug/L) at the mid and surface depths for much of the week. Overall chlorophyll averaged 12.6 ug/L, 11.6 ug/L, and 5.9 ug/L at the surface, mid, and bottom, respectively. The maximum surface chlorophyll reading was 35.6 ug/L on July 21. 

Week of July 10 - 16, 2022

Fixed Site Network

Phillipsdale Landing

Sondes were swapped for maintenance during the morning of July 12. Water quality at Phillipsdale Landing was poor to fair this week. The weather remains dry, with only trace rainfall on July 12 and 16, and 0.02 inches on July 14 recorded at T.F. Green. Blackstone River flows increased midweek but remained below 17-year median flow rates. Salinity at the surface averaged 20.5 ppt and ranged 11.1 ppt – 26.2 ppt. At the bottom, salinity averaged 23.9 ppt and ranged 16.1 ppt – 27.8 ppt. Temperatures averaged 24.9°C at the surface and 24.2°C at the bottom. Surface temperatures ranged from 22.1°C to 27.5°C, while bottom temperatures ranged from 21.9°C to 26.4 °C.

Dissolved oxygen (DO) remains low at Phillipsdale, particularly in the bottom waters. Bottom water DO concentration averaged 3.2 mg/L for the week and ranged from 0.2 mg/L to 8.9 mg/L. The longest duration of hypoxia (i.e., DO < 2.9 mg/L) was approximately 12 hours from overnight July 9 through the morning of July 10, during which time DO averaged 1.46 mg/L. Surface DO was higher, averaging 5.9 mg/L and ranging 0.9 mg/L – 15.1 mg/L. Surface waters were hypoxic for approximately 6.5 hours on July 14 (average DO 1.83 mg/L during that time), and during isolated short periods (<1 hr) on other days. Chlorophyll concentrations remain elevated, but declined since last week, averaging 21.2 ug/L at the surface and 18.2 ug/L at the bottom. Maximum surface chlorophyll readings reached 166 ug/L on July 10. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach Buoy

Water quality was fair to good at Bullock Reach this week. Salinity averaged 28.4 ppt, 29.7 ppt, and 30.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 26.1-30.1 ppt, mid salinity ranged 27.7-30.7 ppt, and bottom salinity ranged 29.3-32.1 ppt. Temperatures increased this week. Surface temperature averaged 24.3°C and ranged from 22.8°C to 26.0°C. Mid temperatures averaged 23.5°C and ranged from 21.8°C to 25.0°C. Bottom temperatures averaged 22.4°C and ranged from 19.4°C to 24.0°C. 

DO concentrations at Bullock Reach remained above the acute hypoxia threshold (2.9 mg/L) all week. Surface DO averaged 7.2 mg/L and ranged 5.3-9.0 mg/L. In the mid waters, DO averaged 6.1 mg/L and ranged 4.3-8.2 mg/L. At the bottom, DO averaged 4.7 mg/L and ranged 3.2-6.6 mg/L. Chlorophyll readings were generally low, but became slightly elevated on July 13 into July 14, suggestive of phytoplankton activity. Overall chlorophyll averaged 12.1 ug/L, 10.8 ug/L, and 4.1 ug/L at the surface, mid, and bottom, respectively. The maximum surface chlorophyll reading was 29.5 ug/L on July 14. Please note there are some indications that the turbidity data for the surface sonde deployed July 7 are problematic; use these turbidity data with caution.

Week of July 3 - 9, 2022

Fixed Site Network

Phillipsdale Landing

Water quality at Phillipsdale Landing was poor to fair this week. The weather was dry, with only trace rainfall on July 5 and 6 recorded at T.F. Green. Blackstone River flows had increased slightly in response to rainfall the week prior, but remained low overall, declining all this week. Salinity at the surface averaged 17.4 ppt and ranged 9.2 ppt – 23.3 ppt. At the bottom, salinity averaged 24.1 ppt and ranged 17.3 ppt – 28.2 ppt. Temperatures averaged 24.2°C at the surface and 22.8°C at the bottom. Surface temperatures ranged from 21.2°C to 27.0°C, while bottom temperatures ranged from 21.1°C to 27.0 °C.

Dissolved oxygen (DO) this week was low, with conditions below the hypoxia threshold (2.9 mg/L) for much of the week. Bottom water DO concentration averaged 2.4 mg/L and ranged from 0.3 mg/L to 10.8 mg/L. The longest duration of hypoxia was 17 hours on July 8, during which time DO averaged 1.31 mg/L. Surface DO was higher, in some part due to an active phytoplankton bloom. Surface DO this week averaged 9.2 mg/L and ranged 1.6 mg/L – 23.0 mg/L. Surface waters were hypoxic briefly on July 3 and 5. Chlorophyll concentrations were elevated all week, averaging 46.2 ug/L at the surface and 26.3 ug/L at the bottom. Maximum surface chlorophyll readings reached 488.5 ug/L on July 4. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach Buoy

Sondes were swapped for maintenance during the morning of July 7. Please note there are some indications that the turbidity data for the surface sonde deployed July 7 are problematic; use these turbidity data with caution. Water quality was fair at Bullock Reach this week. Salinity averaged 27.3 ppt, 29.3 ppt, and 31.2 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 24.4-29.2 ppt, mid salinity ranged 27.0-30.9 ppt, and bottom salinity ranged 29.6-32.1 ppt. Surface temperature averaged 23.6°C and ranged from 22.3°C to 25.5°C. Mid temperatures averaged 22.8°C and ranged from 20.9°C to 24.3°C. Bottom temperatures averaged 20.9°C and ranged from 19.4°C to 23.2°C. 

DO concentrations at Bullock Reach generally remained above the hypoxic threshold, except for some isolated periods of hypoxia at the bottom on July 5 and 6. The longest duration of hypoxic conditions in these waters was approximately 45 minutes. DO at the surface averaged 7.7 mg/L and ranged 4.9-10.6 mg/L. In the mid waters, DO averaged 6.0 mg/L and ranged 3.6-8.6 mg/L. At the bottom, DO averaged 4.0 mg/L and ranged 2.6-6.5 mg/L. Chlorophyll readings were slightly elevated, particularly during the second half of the week, when readings in surface and mid waters reached maxima of 34.9 ug/L and 37.1 ug/L, respectively. Overall chlorophyll averaged 12.6 ug/L, 12.8 ug/L, and 5.2 ug/L at the surface, mid, and bottom, respectively. 

Week of July 17 - 23, 2022

Bacteria Sampling

On July 20, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers.  Five of these stations were also sampled for enterococci bacteria. Precipitation in the five days prior to sampling totaled 0.17 inches as recorded at TF Green.

Overall, bacteria counts were lower in the Seekonk River and higher in the Providence River this week than during the previous sampling event on July 6.  The geometric mean of fecal coliform results for all sites was 98 MPN/100 mL, with the Seekonk River sites having higher counts than the Providence River sites (geometric means of 345 MPN/100 mL and 54 MPN/100 mL, respectively). The maximum count (4300 MPN/100 mL) was measured at Division St. Dock in the Seekonk River.

Enterococci results had an overall geometric mean of 10 MPN/100 mL. Enterococci results ranged from non-detect at four sites (Phillipsdale Landing, South FP East, Gaspee Point, and Conimicut Point) to 10 MPN/100 mL at the Point St. Bridge site.

The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of water ingestion (e.g., swimming, diving, water skiing, and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing 
 ​
Fecal ColiformEnterococci
Primary Con​​​t​a​ct1​​​​​

Geome​tric mea​n​ ≤50 MPN/1​00​ mL
<10% ​of​ samples >400 MPN/100 mL

Geom​etric mean ≤35 colo​nies/100 mL
All sa​mples ≤104 colonies/100 ​​mL2

Shellfishing

Geometric mean ≤14 MPN/100 mL
<10% of samples >49 MPN/100 mL3

NO ENTEROCOCCI CR​ITERIA
1Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; 2Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; 3For a three-tube decimal dilution

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.

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