Snapshot of the Bay

Historical News

Week of August 11 - 17, 2019

Fixed Site Network

Phillipsdale Landing

Water quality was poor to fair this week at Phillipsdale Landing. Rainfall was light throughout the week, just 0.13 inches recorded on August 13, and 0.1 inches on August 17; salinity at the surface and bottom increased over the course of the week. Surface salinity averaged around 15 ppt, ranging 5.6 – 23 ppt; bottom salinity averaged 24 ppt, ranging 11.5 – 28.5 ppt. Water temperatures were slightly cooler this week than last, with surface waters averaging 24.4°C and bottom waters averaging 23.8°C. Dissolved oxygen (DO) levels were poor at the start of the week, showing some improvement as the week progressed. Surface water DO averaged 8.6 mg/L, with observations of hypoxia (DO <2.9 mg/L) occurring periodically; the longest period of continuous hypoxia at the surface was just over two hours during the night of August 13-14. Bottom DO averaged 2.6 mg/L and waters were hypoxic for much of the first half of the week. The longest continuous stretch of hypoxic conditions was 22 hours, from mid-day August 12 to mid-day August 13. Chlorophyll was slightly higher this week than last, averaging 51.6 ug/L in surface waters; peaks in chlorophyll concentrations >300 ug/L occurred overnight on August 12-13 and August 13-14.

Note that tidal fluctuations and Blackstone River flow greatly influence water column DO, temperature, and salinity at this location.

Bullock Reach

This week at Bullock Reach, water quality was good to fair; the sondes were changed-out for maintenance on August 14 at 09:30 EDT. Average water temperatures were 24.0°C at the surface, 23.3°C at the mid sonde, and 21.8°C at the bottom, all displaying a slight decrease compared to last week. Surface salinity ranged from 21.9 ppt to 28.4 ppt, averaging 26.4 ppt. Salinity values at the mid sonde and bottom sondes averaged 28.5 and 30.1 ppt, respectively. Density stratification was most apparent in the latter half of the week, when temperature differences between the surface and bottom reached 4 – 6°C and salinity differences of 3 – 7 ppt were observed. DO showed some improvement compared to the previous week. There were no recorded measurements of hypoxia (DO <2.9 mg/L) at the surface or bottom sondes; DO at the middle sonde dipped just below the hypoxia threshold for a single reading during the morning of August 16. For the week overall, surface DO averaged 7.8 mg/L with a minimum of 5.4 mg/L, the mid depth had an average of 5.9 mg/L with a minimum of 2.8 mg/L, and the bottom had an average of 4.2 mg/L with a minimum of 2.9 mg/L. Water column chlorophyll was variable throughout the week and hit the highest concentrations in bottom waters. Surface chlorophyll averaged 12.2 ug/L, chlorophyll at the mid sonde averaged 9.2 ug/L, and chlorophyll at the bottom sonde averaged 8.1 ug/L.

Week of July 28 - August 3, 2019

Nutrients Sampling

Seven bay stations and seven local and state border river stations were sampled for nutrients on July 31, 2019. Surface and bottom waters were sampled at all bay stations. Conditions were dry for the five days prior to sampling, with no recorded precipitation.

Among the river stations sampled, highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) values occurred at the Pawtuxet River at Broad St. site, at 1290 ppb, 1340 ppb, and 1048 ppb, respectively. Lowest TN and TDN values were recorded at Ten Mile River at Roger Williams Ave, with concentrations of 497 ppb and 472 ppb. The Blackstone River at Slater Mill had the lowest recorded DIN concentrations, at 44 ppb.

At the bay surface stations, greatest TN, TDN, and DIN was observed at Pawtuxet Cove (average of duplicate samples: 1065 ppb, 746 ppb, 619 ppb, respectively). Lowest TN values were observed at Phillipsdale Landing, at 453 ppb. Four bay stations had TDN values below detection (<100 ppb) – Conimicut Point, Edgewood Yacht Club, Pomham Rocks, and Bullock Reach Buoy; low DIN values (<20 ppb) were also observed at these sites. Chlorophyll a concentrations averaged 5.2 ug/L and ranged from 1.8 ug/L at Bullock Reach Buoy to 12.3 ug/L at Edgewood Yacht Club.

Week of August 18 - 24, 2019

Bacteria Sampling

Twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers on August 21, 2019. Five stations were also sampled for enterococci. In the five days prior to sampling, 0.51 inches of precipitation was recorded.

The geometric mean of fecal coliform results for all sites was 70 MPN/100 mL; counts were higher at the Seekonk River sites than the Providence River sites (geometric means of 316 and 35 MPN/100 mL, respectively). The maximum count (2,300 MPN/100 mL) was measured at the Point St. Bridge site. Overall, the Providence River results were within state standards for primary contact.

The enterococci results decreased from the previous sampling event on August 7, from 19 MPN/100 mL to 14 MPN/100 mL. Enterococci results ranged from <10 MPN/100 mL at most sites to 86 MPN/100 mL at Point St. Bridge. These results met state standards 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 August 25 - 31, 2019

R/V Monitor's Blog

The crew of the R/V Monitor was out on the upper Bay twice this week. First, on Tuesday, August 27th, the crew deployed equipment for the temporary buoy to be installed next week in the Bullock's Reach area. They then conducted 3 profiling transects across the upper Bay using the Seabird instrument. The transects were done at India Point, Pomham Rocks, and Bullock's Reach. Jeff captained the boat while monitoring professionals Mike and Bekki deployed the buoy equipment and conducted the transects. NBC scientist Eliza joined the crew in the afternoon for the transects. It was a calm partly sunny day with a breeze out of the southeast. On Wednesday, August 28th, the crew was out collecting nutrients and plankton samples, taking Secchi Disk and Par sensor water clarity measurements, conducting water column profiles using the Seabird instrument, and conducting real-time surface mapping of water quality parameters, including dissolved oxygen, chlorophyll, water temperature, salinity pH, all in an effor to document water quality improvements associated with NBC construction projects. Jeff captained the boat, while monitoring professionals Sara and Mike collected the samples and data. The day began sunny but became cloudy by late morning. There was no wind and very calm waters. Monitoring was only conducted in the morning due to stormy weather predicted for the afternoon. The Block Island Ferry was observed outbound by the Port of Providence this day.

8-28-19 Block Island Ferry.jpg

Week of August 11 - 17, 2019

Water Column Clarity

Water clarity was measured at eight locations in the Providence and Seekonk Rivers on August 15, 2019. Light rain fell two days prior to the survey, totaling 0.13 inches. Average Secchi depth decreased very slightly since the previous week’s survey, from 1.5 m to 1.4 m. Three sites exhibited decreased clarity since the previous survey, with the greatest drop observed at India Point Park (-0.9 m). Three sites exhibited increased clarity, with the greatest increase observed at Pomham Rocks (+0.8 m); the remaining two sites were either unchanged from the previous survey or had not been surveyed for several weeks before, making such comparisons inappropriate. Overall, there was no gradient in water clarity up or down bay. The lowest clarity was measured at India Point Park and at Pawtuxet Cove: 0.8 m. The highest water clarity was observed at Pomham Rocks, at 1.9 m.