Updated Results
| Project | Years | Focus | Data |
| Saltwater Quality Monitoring | 2022- 2024 | Collect detailed data on water quality | Data Table |
| Saltwater and Freshwater | 2022- 2024 | Summary & Analysis |
Preface – What Are We Measuring?
by Dave Stevens
Friends of Taunton Bay (FTB) has been closely monitoring the saltwater quality of the bay since 2022. This ongoing initiative helps ensure the bay remains a vibrant ecosystem for marine life. Monitoring happens at four key locations (see map below): Gordon’s Wharf, Egypt Bay, CCAR Inlet, and Hog Bay, where water quality is tested regularly for temperature, salinity, dissolved oxygen (DO), pH, and clarity. The results have been impressive. Dissolved oxygen levels are consistently safe, supporting marine life, and bacteria levels around stream inlets show no signs of contamination.
In addition to basic water quality, FTB also tracks essential nutrients like nitrogen and phosphorus, as well as heavy metals. So far, these elements have remained at safe levels, reassuring residents and marine life alike. Volunteers, including students from local high schools, play a crucial role in these efforts, gathering valuable data that helps scientists understand the seasonal changes in the bay’s health.
We use a boat to sample at the four sites shown in the aerial view on this page. These four sites form our baseline to see what (if any) variation there is in water quality within the bay structure. Testing occurs roughly every three weeks, to coincide with the highest and lowest of the monthly tides. Data is taken and analyzed where data indicates a specific need; such as extra-low-tide sampling at specific sites, or investigating areas where there maybe septic or runoff issues.
2022-24 Results
by Dave Stevens
Summary of Saltwater and Freshwater Results 2022- 2024
The FTB Water Quality Team is in its third year of studying the health of the bay. Water samples from four designated bay sites have been taken twice a month from May to November. As a reminder the sites are: Gordon’s Wharf, Egypt Bay (by seal pup island), the CCAR inlet (close to Butler Point), and Hog Bay (adjacent to seal rocks).
The team attempts to get two samples per month – at a low and a high tide. There are 29 sampling sessions represented in the data to date).
Temperature:
Temperature at Gordon’s Wharf is very consistent (less than 1 degree F difference) from the surface to the bottom at both tide stages. We think this is because of the excellent mixing due to the narrow channel and the tide velocity. As one travels north in the bay, the temperature generally increases (more so at low tide). Surface to depth temperature difference can be as much as 4 to 5 degrees F on bright sunny summer days, and very little on overcast days.
pH:
pH measures the acidity or alkalinity of the water. In Taunton Bay it has been very consistent so far–averaging 7.9 across all samples. As a comparison, pure water is 7.0, and seawater is normally more basic, 8.0-8.5. Marine life, especially juvenile shellfish, grow best at optimal pH levels, (at risk below 7.5). Our individual low sample was 7.7 and our high was 8.0. The majority of samples rounded between 7.8 and 7.9.
Dissolved Oxygen (DO):
DO is an important measure of water quality, indicating an aquatic system’s ability to support life. It measures the amount of “free” (usable) oxygen in the water. Low levels (below 5mg/L) can be harmful to aquatic organisms.
The good news is that in all samples at all sites, the dissolved oxygen was above the levels generally thought to support most marine species. The overall average for all the DO sampling was 98.5% at the surface and 96.5% at depth. Generally, wave action tends to increase DO at the surface by mixing oxygen into the water.
Readings over 100%, caused by photosynthesis or turbulent waters (like at Tidal Falls), mean extra oxygen is available for aquatic life.
There appeared to be very little difference between DO levels at high and low tides (0.1%).
There is a slight trend of DO dropping the farther north one goes in the bay. One unexplained finding is that the CCAR inlet sample point has the lowest overall DO numbers of all four sample points. Our lowest reading—86.9% at the CCAR inlet 10 meters deep during low tide—is still an excellent saturation amount and sufficient to support native species. More investigation is needed to explain this.
Salinity:
Salinity in Gulf of Maine ocean water varies seasonally from roughly 31.9 parts per thousand (ppt) to 33.2 ppt and is fairly well correlated with ocean temperature.
Taunton Bay is obviously tidal with one estimate of over 5 billion gallons flowing in (or out) at each tide. This brings in a lot of seawater compared to the runoff from small streams that also contribute. We would expect
salinity to be higher in the summer (less stream run off) and at high tides (pushing water in). As predicted, the graph on salinity indicates a generally lower salinity as one travels north in the bay, at low tides (versus high tides), and at the surface compared to depth (seawater is denser so tends to sink if not mixed).
Turbidity:
We have experimented with three methods of assessing water clarity (turbidity) and have settled on two)–a Secchi disk and a turbidity tube. In the bay, we measure turbidity by lowering a Secchi disk (circular black and white disk) into the water column and noting the distance when it first is not visible. Our sampling of turbidity is much less variable than the actual turbidity of Taunton Bay. This is due to the fact that we do not go out and sample at wave heights over two feet; the greatest turbidity noted on our
shoreline is when winds/waves are highest. However, even with milder winds and wave height we can detect the correlation to turbidity.
Total Nitrogen and Total Phosphorus:
In 2024, lab analysis was conducted on Total Nitrogen and Total Phosphate. Our Total Phosphate results (0.0390 to 0.0522) were lower than the average for concentrations along the Maine coast (0.057 to 0.085mg/L)1. Our Total Nitrogen results were 0.25 to 0.28 mg/L compared to the Maine coastal waters mean range of 0.22 to 0.30
mg/L. 2 We will continue to monitor these factors.
Bacterial Pollution:
We have not detected much pollution in the bay, nor much coming in with the ocean water. The four bay sites were sampled for E.coli/coliforms (bacteria) in August and October this year and those bacteria were not detected. In past years, bacterial testing near the stream inlets showed the
presence of some E. coli/ coliforms, prompting us to study this further.
Summary of Results:
The sampling to date indicates that the water quality in the bay is, and continues to be, of good quality for all macro factors sampled. In three years of sampling there does not appear to be a consistent trend in temperature change. Turbidity has been variable and related to wave height and position in the bay. Dissolved oxygen has been excellent in most cases, and even rare low measurements are adequate for almost all ocean creatures to survive. Salinity has been predictable by tide stage and position in the bay.