The short version
Each summer the Mashpee Wampanoag Tribe, the Town of Mashpee and UMass Dartmouth’s School for Marine Science and Technology (SMAST) sample Waquoit Bay and Popponesset Bay. Their memo on summer 2022 finds both bays still badly overloaded with nitrogen. Every Waquoit Bay station was above its state nitrogen limit, and nitrogen rose at most stations compared with 2021. Algae levels dropped from 2021 but stayed above the impairment line almost everywhere, and the lowest bottom-water oxygen readings fell below the state minimum. With Mashpee’s sewering just getting started, the authors did not expect improvement yet.
What the report covers
This memo is the newer edition of the program summarized in our post on Mashpee’s monitoring, 2010–2020.
- Volunteers and SMAST staff sampled stations throughout both bays in summer 2022 for nitrogen, salinity, algae (chlorophyll pigments), oxygen and water clarity.
- The authors compared 2022 with 2021, with the 1997–2009 long-term average, and with three-year periods since 2010.
- They scored each station on a “Bay Health Index” first developed for Buzzards Bay, which combines nitrogen, algae, bottom oxygen and clarity into one score.
What they found
- Nitrogen above the limit everywhere. All Waquoit Bay stations exceeded their state limits (0.38 mg/L for most of the bay, 0.446 for Jehu Pond and 0.5 for the Quashnet River). Nitrogen rose at 11 of 16 Waquoit stations compared with 2021, by 5% to 54%. Summer 2022 averages ranged from 2.47 mg/L in the upper Childs River to 0.42 mg/L in the main bay near the inlet.
- Less algae, but still too much. Algae pigments were 9% to 80% lower than in 2021 and below the long-term average, yet still above the 3 µg/L impairment threshold at nearly every station. The authors could not yet say why 2022 was different.
- Too little oxygen. The memo reports that all but one Waquoit station had low-end oxygen (the average of the lowest 20% of readings) below the state’s 6 mg/L standard. The worst were the upper Childs River at 0.9 mg/L and Jehu Pond at 1.5 mg/L.
- The rivers are the worst. Six of 18 Waquoit stations scored Fair/Poor on the health index, all in the estuary reaches of the Childs River, Quashnet River and Red Brook. Only the main-bay station closest to the inlet scored High. Fourteen of 18 stations scored a little better than the long-term baseline.
- Saltier upper rivers. At the uppermost river stations, 2022 salinity was 55% to 112% above the long-term average. The authors suggest a growing tidal range as one possible cause but say more data are needed.
- Some ponds may bounce back faster. Hamblin and Jehu Ponds had lost their eelgrass only recently when the state’s study was done, so they may recover sooner than basins far above their limits.
What it means for Waquoit Bay today
Summer 2022 is essentially a “before” picture. The authors conclude that both bays are still well above their assimilative capacity
(Eichner et al., 2024) and expect nitrogen to keep rising as building continues, with big swings from year to year. Their main recommendation is that Mashpee update its baseline before sewers start to work, measuring bottom-dwelling animals, sediments, round-the-clock oxygen and algae, streamflow, tides and watershed nitrogen loads, so that improvements can be shown to the state. The limits the bay is measured against are explained in our summary of the 2020 Waquoit Bay TMDL.
One caution on the oxygen numbers. The memo’s text says the middle Quashnet River station (WB08) rose above the 6 mg/L standard in 2022, but its own data table lists 4.16 mg/L for that station, and no Waquoit station in the table reaches 6 mg/L. The salinity discussion also labels WB8 as the Childs River. Readers should treat the station-by-station oxygen statements with some care; the overall picture of low oxygen is not in doubt.
Read the report
Eichner, E., Samimy, R., & Sampieri Horvet, S. (2024, February 6). Water Quality Monitoring Program for the Popponesset Bay and Waquoit Bay Estuaries (summary of summer 2022 results). Technical memorandum for the Mashpee Water Quality Monitoring Consortium (Mashpee Wampanoag Tribe and Town of Mashpee Waterways Commission). Coastal Systems Program, School of Marine Science and Technology, University of Massachusetts Dartmouth. https://www.mashpeema.gov/DocumentCenter/View/1448/2022-Water-Quality-Report
License: A technical memorandum prepared for the Mashpee Wampanoag Tribe and the Town of Mashpee. It is not openly licensed, so we link to the copy on the Town’s Water Quality Reports page rather than hosting one. The card image is the memo’s first page.
Drafted with AI assistance from the linked source.
