Snapshot of the Bay

Historical News

Week of October 14 - 20, 2018

Benthic Video Blog

The boat crew conducted benthic video surveys along all three permanent transect locations on October 19th. Scale lasers were used in the footage, separated by 29 cm. Visibility through the water column was moderate.

The bottom was characterized by muddy sand along both transects, though Sabin also has an extensive area of boulders and areas covered in clam shell rubble; several small fishes were observed using the shell rubble as habitat structure. One larger fish, a summer flounder (Paralichthys dentatus) was observed along the Bullock Reach transect. Common observations along all transects included hermit crabs, boring sponges in clam shells, small-medium infaunal burrows, large burrow openings (likely from the mantis shrimp, Squilla) and parchment tube worms (Chaetopteridae; particularly abundant along Bullock Reach). Mudsnails were highly abundant along the Edgewood transect (see photo), while seastars were observed along the Sabin transect. Sparse algae (Ulva and Grateloupia, mainly) were observed in all areas, but there were no extensive rafts; similarly, no amphipod tube mats were observed.

Week of December 16 - 22, 2018

Water Column Clarity

Water clarity was measured at five locations in the Providence and Seekonk Rivers on December 19, 2018. In the five days prior to sampling, 0.91 inches of rainfall occurred. Average water clarity increased from the previous sampling, from 1.6 m to 2.8 m.

Water clarity increased at all five sites sampled: India Point, Pomham Rocks, Edgewood Yacht Club, Pawtuxet Cove, and Conimicut Point. The largest increase in clarity, 2.2 m, occurred at India Point. Secchi depth ranged from 1.83 m at Pawtuxet Cove to 3.63 m at India Point. There was evidence of a slight north to south water clarity gradient.

Week of December 16 - 22, 2018

Water Column Profiles

Water column profiles were measured at five sites in the Seekonk and Providence Rivers on December 19, 2018. Nearly an inch of rain (0.87 inches) was recorded in the area over the three days prior to the survey, and two sites (Pawtuxet Cove and Edgewood Yacht Club) displayed some density stratification.

The lowest surface salinities were 3-4 psu, measured at Pawtuxet Cove; the highest surface salinities (26 psu) occurred at Conimicut Point and Pomham Rocks. Bottom salinity ranged from 21 psu at Pawtuxet Cove to 30 psu at Conimicut Point and Edgewood Yacht Club. The coldest surface water temperature was observed at Pawtuxet Cove at 4°C, while the warmest surface water temperature (6.9°C) occurred at Pomham Rocks. Bottom water temperatures ranged from 6.2°C at Pawtuxet Cove to 8°C at Edgewood Yacht Club.

Hypoxic conditions (dissolved oxygen <2.9 mg/L) were not observed at any site this week. Dissolved oxygen ranged from 7.74 mg/L in the bottom waters of Edgewood Yacht Club to 11.88 mg/L at the surface at Pawtuxet Cove. Fluorescence was low (<3 mg/m³) at all sites, with the maximum (2.3 mg/m³) observed at 1 meter depth at Pawtuxet Cove.

Week of November 18 - 24, 2018

Phytoplankton Sampling

Phytoplankton samples were collected at Bullock's Reach on November 21, 2018 and analyzed in the laboratory shortly after collection. It was a cold day on Narragansett Bay. Sondes data revealed the surface water temperature was 9.11^oC, salinity was 22.55 psu, and chlorophyll a was 0.6 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was thick and opaque with a light rusty brown color and a long 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 43,000 cells per Liter. The most predominant phytoplankton was Thalassionema at 5,000 cells/L. The flagellates were found at 13,000 cells/L and other representative genera include Leptocylindrus spp. and Skeletonema spp.

200x phase contrast micrograph of Odontella spp

odontella spp.jpg

Week of November 18 – 24, 2018

Nutrients Sampling

Seven bay stations and seven river stations were sampled for nutrients on November 21, 2018. Surface and bottom waters were sampled at all bay stations. In the day prior to sampling, 0.2 inches of rainfall occurred. Five days before sampling, there was 0.94 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 Roger Williams Avenue, with reported values of 1210 ppb, 1320 ppb, and 1033 ppb, respectively. The Woonasquatucket River at Manton Avenue had the lowest measured TN (580 ppb), TDN (620 ppb), and DIN (400 ppb) values.

Out of the bay surface water samples, the highest TN concentration was observed at Phillipsdale Landing, at 878 ppb. The highest bay surface TDN and DIN concentrations occurred at Pawtuxet Cove, at 869 ppb and 644 ppb, respectively. Lowest TN and TDN values were observed at Conimicut Point, at 500 ppb TN and 536 ppb TDN. The lowest bay DIN value (334 ppb) occurred at Bullock Reach Buoy. Chlorophyll a averaged 1.0 ug/L, ranging from 0.4 ug/L at Edgewood Yacht Club to 1.9 ug/L at Phillipsdale Landing.

Results from nutrient sampling completed on December 5 and December 19 are pending final analysis from the NBC Laboratory. The next anticipated date of sampling is January 2, 2019.