Fourteen local and border river stations and one bay station (surface and bottom) were sampled for nutrients on December 5, 2018. Due to inclement weather, the boat did not go out to collect bay samples, but Phillipsdale Landing was collected by land. In the five days before sampling, there was 0.69 in of recorded rainfall.
Among the river stations sampled, highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) values were measured in the Ten Mile River at Central Ave, with reported values of 1,480 ppb, 1,660 ppb, and 1,401 ppb, respectively. The Coles River had the lowest measured TN (569 ppb) and DIN, TDN (253 ppb) values with the Palmer River having the lowest TDN value with 638 ppb.
The only bay sample at Phillipsdale Landing had surface TN, TDN and DIN values of 1,100 ppb, 1,280 ppb, and 928 ppb respectively. The bottom sample had concentrations of 1,080 pbb for TN, 1,130 for TDN, and a DIN of 909 ppb.
Results from nutrient sampling completed on December 19, January 2, 2019 and January 16 are pending final analysis from the NBC Laboratory. The next anticipated date of sampling is January 30, 2019.
Fixed Site Network
The sondes at Phillipsdale were deployed on February 20, 2018 and remained deployed throughout the year, except for a short time in December when a large downed tree floated up against the sondes at the Phillipsdale Landing dock. Surface and bottom temperatures averaged 15.2oC and 14.9oC respectively for the entire season and had maximum daily averages of 28.0oC and 27.2oC on August 9th. Surface and bottom salinity ranged from 0.19 – 23.4 ppt and 0.19 – 26.7 ppt, respectively during the year. Flow from the Blackstone River particularly affected salinity concentrations in the fall with high rainfall and subsequent high river flow. Surface DO was fair to good throughout the season with the lowest daily DO values of about 3.0 mg/L observed in mid-August and early September, and a seasonal average of 9.6 mg/L. Surface chlorophyll was elevated several times throughout the season, particularly July, August, and September that had many consecutive days with daily chlorophyll averages above 10 ug/L; the daily maximum for chlorophyll was about 50.0 ug/L at the end of August and there was a seasonal average of 9.4 ug/L. Bottom dissolved oxygen (DO) had a minimum daily average of about 0.3 mg/L in August, with the majority of time in late July and most of August with DO under the hypoxic threshold of 2.9 mg/L; bottom DO averaged 7.1 mg/L for the year.
The Bullock Reach sondes were removed for the season on November 6th, and EMDA staff assisted DEM with buoy removal on November 14th. The sondes at Bullock Reach were deployed from June 14th to November 6th. The season had fair to good water quality. Dissolved oxygen (DO) was fair at the bottom with a minimum daily average of about 1.5 mg/L and 8.1% of the season showing hypoxic conditions for periods of 24 hours; this was an increase from 2017 and the highest percent of hypoxia that has been observed at Bullock Reach since 2013. The seasonal DO average of the bottom was 4.6 mg/L. Mid-depth DO was hypoxic for approximately 0.4% of the summer and had a seasonal average of 5.6 mg/L. Surface DO was good throughout the season with only some moderate hypoxia on August 14th, and a seasonal average of 7.3 mg/L. Seasonal temperatures peaked in early August at all three depths with highest daily average temperatures measuring about 28.0oC on August 7th at the surface, 27.0oC on August 8th at the mid-depth and 25.0oC on August 4th at the bottom. Average seasonal temperatures at the surface, mid, and bottom were 21.9oC, 21.4oC, and 20.5oC respectively. Compared to 2017, bottom water temperatures were elevated above last year’s average temperatures by about 2oC, whereas surface and mid temperatures were similar. Chlorophyll was moderate this season at the surface with a daily maximum of about 35.0 ug/L in mid-September and a seasonal average of 9.9 ug/L. Chlorophyll at the mid-depth peaked at around 17.0 ug/L at the end of July with a seasonal average of 5.9 ug/L; bottom chlorophyll peaked at about 11.5 ug/L at the end of June and the end of July and a seasonal average of 4.1 ug/L.
R/V Monitor's Blog
On Wednesday, January 9th, the crew of the R/V Monitor was out on the upper Bay collecting bacteria 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 and pH, all in an effort to document water quality improvements associated with NBC construction projects. Jeff captained the boat, while monitoring professionals Mike and Fern collected the samples and data. The day started sunny any calm, but winds picked up by late morning. The water remained calm throughout the sampling day. The photo below was taken back in December on the Seekonk River.
Water Column Profiles
Highest water column salinity was measured at Conimicut Point, where salinity ranged from approximately 18 psu at the surface to 29.3 psu at depth. Lowest salinity was recorded at Pawtuxet Cove, with readings of 3.5 psu in surface waters and 19.9 psu at depth. Surface water temperature was coldest at Pomham Rocks, at 4.3°C, while the greatest surface water temperature, 5.7°C, occurred at Edgewood Yacht Club. Bottom water temperatures ranged from 6.4°C at Pawtuxet Cove to 7.0°C at Conimicut Point.
Hypoxic conditions (dissolved oxygen <2.9 mg/L) were not present at any of the sites sampled. Dissolved oxygen ranged from 9.06 mg/L at depth at Pawtuxet Cove to 12.29 mg/L in surface waters of Pomham Rocks. Fluorescence averaged 1.3 mg/m3 at all sites, and the maximum fluorescence (2.4 mg/m3) was observed at Bullock Reach.
Data was collected on January 9, 2019 while the R/V Monitor was underway collecting bacteria samples. The chlorophyll concentrations were low in areas surveyed. From north to south, average chlorophyll concentrations were as follows: Seekonk River (3.04 µg/l), Upper Providence River (3.12 µg/l), Edgewood Shoals area (3.49 µg/l), Pawtuxet River area (3.00 µg/l), and the Lower Providence River (2.61 µg/l). Overall, chlorophyll ranged between 1.40 µg/l and 5.30 µg/l with an overall average of 3.00 µg/l. The chlorophyll data from this date is presented in the map below: