Snapshot of the Bay

Historical News

Week of October 20 - 26, 2019

Water Column Profiles

Water column profiles were measured at five sites in the Providence River on October 24, 2019. A sixth site, Bullock Reach, was also surveyed however a malfunction with the instrument caused the data to be incomplete and unusable. The two days prior to the survey were rainy, with 0.16 inches recorded on October 22 and 0.42 inches recorded on October 23 (TF Green gauge data). Salinity stratification was observed at three sites (Pomham Rocks, Conimicut Point, and India Point Park), while the remaining two sites exhibited well-mixed conditions.

Surface salinities were highest at Pomham Rocks (29 psu), and lowest at India Point Park (25 psu). The highest bottom salinity (31 psu) was observed at Pomham Rocks and Conimicut Point, while the lowest (29 psu) was observed at Pawtuxet Cove. The warmest waters overall were observed at Pawtuxet Cove, from 15.8°C at the surface to 15.6°C at the bottom. The coolest surface waters (14.3°C) were observed at Conimicut Point, while the coolest bottom waters (15.1°C) were observed at India Point Park and Pomham Rocks.

This week, hypoxic conditions (e.g., dissolved oxygen [DO] concentrations <2.9 mg/L) were not observed at any of the sites. Surface and bottom DO ranged from 5 to 7 mg/L across all sites. Fluorescence was much lower than previous surveys on September 25, averaging 1.4 mg/m³among all sites, with a maximum of 3.1 mg/m³ at 3.25 – 3.5 m at Conimicut Point.

Week of October 20 - 26, 2019

Phytoplankton Sampling

Phytoplankton samples were collected on October 24, 2019 at Bullock's Reach and analyzed in the laboratory shortly after collection. It was a clear and calm day, with abundant sunshine on Narragansett Bay. Sondes data revealed the surface water temperature was 14.40^oC, salinity was 25.86 psu, and chlorophyll a was 1.4 ug/L. There was noticeable jellyfish in the sample. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a tan color and had a medium filter time. The tow net sample was analyzed qualitatively for microorganisms using 100x 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 108,000 cells per Liter. The most predominant phytoplankton was Leptocylindrus spp.at 68,000 cells/L. The flagellates were found at 32,000 cells/L. Representative genera include Guinardia spp. and Chaetoceros spp.

200x phase contrast micrograph of a centric diatom

centric diatom.jpg

Week of October 27 - November 2, 2019

Fixed Site Network

Phillipsdale Landing

Water quality at Phillipsdale Landing was good this week. The sondes were changed for routine maintenance mid-day on October 29. The week began with heavy rains of 1.4 inches on October 27, with additional light rainfall adding up to 0.42 inches over October 30 through November 1. Salinity at the surface and the bottom decreased over the course of the week following the rain and subsequent increases to freshwater river flows. Surface salinity averaged 10.3 ppt, ranging 2 – 27 ppt, while bottom salinity averaged 19.4 ppt and ranged 2 – 28 ppt. Water temperatures were relatively steady this week, averaging 14.2°C at the surface and 14.8°C at the bottom overall, similar to the previous week. Dissolved oxygen (DO) remained high all week, with no hypoxia (DO <2.9 mg/L) observed at either depth. Surface DO averaged 8.5 mg/L with a minimum of 6.1 mg/L, while bottom DO averaged 7.1 mg/L with a minimum of 5.8 mg/L. Surface chlorophyll-a was low, with an overall average of 2.9 ug/L and a maximum of 9.7 ug/L; three elevated chlorophyll readings from the morning of October 27 were excluded as outliers prior to analysis. Note that tidal fluctuations and Blackstone River flow greatly influence water column DO, temperature, and salinity at this location; in addition, approximately 4.75 hours of surface data from the morning of November 2 has been excluded from this analysis as the depth readings indicated the sonde was possibly hung up on the dock or nearby pilings, and out of the water.

Bullock Reach

Bullock Reach data beyond October 19 are not currently available for posting. The sondes are still deployed and internally logging data, but a careful review of these data is underway. Data will be posted as soon as possible.

Week of October 20 - 26, 2019

Fixed Site Network

Phillipsdale Landing

Water quality at Phillipsdale Landing was good this week. Minor rainfall of approximately 0.5 inches occurred over October 22 and 23, and Blackstone River flows generally decreased over the course of the week. Surface salinity subsequently increased as the week progressed, averaging 10.5 ppt, and ranging from 4 ppt to 23 ppt; variability in surface salinity also increased following the mid-week rain. Bottom salinity was higher than the surface all week, averaging 25.3 ppt and ranging 9 – 31 ppt. Water temperatures were relatively steady, averaging 14.1°C at the surface and 15.0°C at the bottom overall, just slightly cooler than the previous week. In terms of dissolved oxygen (DO) conditions, hypoxia (DO <2.9 mg/L) was not observed at any depths. Surface DO averaged 8.3 mg/L with a minimum of 6.0 mg/L, while bottom DO averaged 6.0 mg/L with a minimum of 4.6 mg/L. Surface chlorophyll-a was low for most of the week, with an overall average of 2.5 ug/L and a maximum of 32.5 ug/L; this high result was a single reading, not indicative of lasting bloom conditions. Note that tidal fluctuations and Blackstone River flow greatly influence water column DO, temperature, and salinity at this location; in addition, approximately 3.5 hours of surface data from the morning of October 20 has been excluded from this analysis as the depth readings indicated the sonde was hung up and out of the water.

Bullock Reach

Week of November 3 - 9, 2019

R/V Monitor's Blog

The R/V Monitor was out on the upper Bay twice this week. First, on Tuesday, November 5th, the crew was out servicing the Bullock's Reach and temporary buoys. Jeff captained the boat while monitoring professionals Bekki and Mike serviced the buoys. It was a sunny day with no wind and calm waters. On Wednesday, November 6th , the crew was collecting nutrients samples, taking Secchi Disk and Par sensor water clarity measurements, conducting water column profiles using the Seabird instruments, 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 Fern and Mike collected the samples and data. It was another sunny day with a slight breeze out of the west-northwest. There were some small waves out on the Bay this day, and a few elusive seals were spotted. The featured photo shows NBC's Seabird instruments being readied for deployment this day.