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New, high-tech sensors that monitor oxygen levels in Buzzards Bay show that the bay’s water quality is worse than previously shown in data collected by hand.
Local scientists have been testing out 20 low-cost sensors — which collect data every 10 minutes — across Buzzards Bay. The data shows that a major local water quality monitoring program is missing roughly 40% to 50% of the low-oxygen events happening in bay waters, compared to the sensors.
The scientists want to deploy more sensors. Yet doing so comes with challenges for the local monitoring program and its volunteers that have tested the water quality of Buzzards Bay weekly during summers, for decades.
So these researchers are studying how to integrate this sensor technology with this local water-quality monitoring program.
The Buzzards Bay Coalition, Woodwell Climate Research Center, and UMass-Amherst researchers are working on the Continuous Oxygen Monitoring in Buzzards Bay project, or COMBB. It’s funded by a four-year, $2 million National Science Foundation grant. It’s starting its second year.
The researchers are evaluating the dissolved oxygen data from the sensors against the data gathered by the coalition’s Baywatchers volunteers during the summer. They are investigating what kinds of sensors can produce useful data efficiently, and where to put them in bay waters.
Meanwhile, the UMass-Amherst team has developed a platform to store and manage the data from the sensors.
They are also surveying volunteers to see how to best incorporate the sensors while sustaining volunteer engagement. They are interviewing regulators, elected officials, and area residents to see how they make sense of the new dissolved oxygen data.
COMBB will enter a new phase this spring. UMass-Amherst researchers are recruiting residents from the 10 communities around Buzzards Bay to talk about the data from these monitoring sensors.
Woodwell Climate Research Center senior scientist Chris Neill said the findings from COMBB will be helpful to coastal water quality monitoring programs nationwide looking to incorporate sensors like these into their work.
The project will also help the Buzzards Bay Coalition advocate for regulation to restore polluted waters in Buzzards Bay, said the Buzzards Bay Coalition’s vice president of bay science, Rachel Jakuba.
What is dissolved oxygen?
Dissolved oxygen is the oxygen gas that is present and dissolved in water. Water bodies absorb oxygen from the atmosphere. Aquatic plants also produce oxygen. It is crucial for the survival of most marine organisms, like fish and shellfish.
Dissolved oxygen levels fluctuate in coastal waters. They experience highs during the daytime, when aquatic plants are photosynthesizing. They experience lows at night, when those plants stop producing oxygen, and marine organisms continue consuming it.
If dissolved oxygen levels in a water body drop too low, even for a short time, it can stress fish and marine life and cause them to leave. It can also result in fish kills.
Low dissolved oxygen levels in coastal waters are an indicator of nitrogen pollution. Major sources of nitrogen in the environment include sewage and septic systems, along with impervious surfaces and fertilizers.
Excessive nitrogen loads cause algae to bloom in coastal waters, making them murky and smelly. When the algae dies, microorganisms break it down, and suck oxygen out of the water.
Warm temperatures can also cause levels of dissolved oxygen in bay waters to temporarily drop. Tides, light, and winds can affect them, too.
Dissolved oxygen is a direct indicator for state environmental regulators of a water body’s ability to support life. The Massachusetts Department of Environmental Protection has a quantitative standard for it: six milligrams per liter.
Waters that do not meet this standard are considered impaired by the state, under the Clean Water Act.
Having a Buzzards Bay water body listed as impaired is the first step toward developing a legally-enforceable pollution reduction target for it, Jakuba said. Those lead to water quality improvements.
Baywatchers and sensors
For more than three decades, the Buzzards Bay Coalition’s Baywatchers program has been responsible for supplying state environmental regulators with water quality data for Buzzards Bay.
Program volunteers collect water samples once per week at 200-plus locations around the bay from May to September. They measure levels of dissolved oxygen, salinity, temperature, and water clarity on-site.
State regulators have used Baywatchers data in listing most of the embayments of Buzzards Bay as impaired.
Still, Jakuba and other local water quality researchers were concerned the data they were getting from Baywatchers did not fully reflect how polluted some bay waters were. They were seeing indicators of more severe nitrogen pollution, like black muck on the bottom of some embayments.
“We just didn’t have the numbers to show just how bad it was,” Jakuba said.
In recent years, companies started producing low-cost continuous oxygen monitoring sensors that can gather more data than programs like Baywatchers.
So the coalition began investing in these sensors about five years ago. It built up a network of roughly 14 around the bay, all made by the Onset Computer Corporation.
The coalition put them in embayments where volunteers were monitoring, so they could compare the data the sensors and volunteers collected.
The sensors and Baywatchers produced data that was in “pretty good agreement,” Jakuba said. However, it showed volunteer monitors were missing the periods of lowest dissolved oxygen in Buzzards Bay waters — in the early morning. They were also missing low oxygen events happening between sampling days.
“We get an incomplete picture of the true water quality if we’re only measuring in periodic intervals,” he said.
Those low oxygen events could be “potentially really important” to ecosystem health, Neill said. They also indicate the scale of nitrogen pollution is more serious in Buzzards Bay waters than the Baywatchers data showed.
The coalition does not want to — nor does it have the capacity to — replace their Baywatchers volunteers with sensors, Jakuba said. It wants to continue the volunteer-based water quality monitoring program.
“The volunteers are a critical resource,” Jakuba said.
So the COMBB project is an effort to ensure the coalition is gathering, managing, and communicating the sensor data effectively, Jakuba said.
“If we can do those three things, this data is extremely powerful,” she said. “It can help communicate … the scale of the problem that we’re facing, and where we need to make changes in order to protect water quality.”
Recent work and findings
Field work started on COMBB last summer. The coalition and Woodwell research team deployed and gathered data from six new Onset Computer Corporation dissolved oxygen sensors across Onset Bay, from June to October. They also gathered data from the 14 existing dissolved oxygen sensors in the coalition’s network.
The researchers collaborated with UMass-Amherst data scientists to develop systems for managing the data. They analyzed the results, and compared them to the data they got from Baywatchers.
The Woodwell team also analyzed 30-plus years of Baywatchers data for trends in dissolved oxygen levels. Anita Milman, a UMass-Amherst professor of environmental conservation, and her research team also surveyed Baywatcher volunteers in the fall about their motivations for participating in the program.
The researchers found that the period in which researchers start to detect low oxygen events across Buzzards Bay comes roughly two weeks earlier now than it did in previous decades. Neill said this reflects the impacts of climate change and warming temperatures on local water quality.
The data also revealed dissolved oxygen levels vary in different sections of Onset Bay with different environmental characteristics.
Next steps
This spring and summer, the coalition and Woodwell researchers will test Onset Computer Corporation dissolved oxygen sensors in three new embayments of Buzzards Bay: New Bedford Harbor, Apponagansett Bay, and West Falmouth Harbor.
They will also try out Woods Hole Oceanographic Institution-designed TideRider robots, which float on the water and can monitor dissolved oxygen at different locations of an embayment as the tides change, Neill said.
Milman and her doctoral students will also begin researching how area residents, town officials, and state regulators make sense of the data from the sensors, and how they can use it.
Over an hour, the researchers will show participants raw data from the dissolved oxygen sensors, and some basic tools to manipulate it. They will show participants summary statistics for important measurements, like the low point for dissolved oxygen in a water body’s daily cycle.
The researchers will ask participants to discuss and record their thoughts about the data. They will analyze interview transcripts for patterns in responses. They will come up with potential data visualizations.
Next year, Milman and her team will host focus group discussions with participants to test out different data visualizations.
Jakuba of the Buzzards Bay Coalition said the data shows “we need to double down on … trying to improve water quality and reducing nitrogen pollution, and we need to only accelerate that.”
Email climate and environment reporter Adam Goldstein at agoldstein@newbedfordlight.org.
How will the DOGE activity affect the grants needed to continue this important project?