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USM senior Tyler Walsh assessing, addressing pollution in Casco Bay

Tyler Walsh and Curtis Bohlen

In a state with nearly 3,500 miles of coastline, where some of the most economically- and culturally-significant exports come from the sea, clean water is crucial. But threats from a changing climate and rapid development contribute to pollution that can have a lasting — and possibly detrimental — impact on Maine’s aquaculture industries.

Research conducted this summer by University of Southern Maine (USM) student Tyler Walsh, through an internship with the Casco Bay Estuary Partnership (CBEP), aims to better understand nutrient pollution in Casco Bay. 

The goals of the project, said Curtis Bohlen, CBEP director and chief scientist on the study, are to assess when nitrogen levels are high, to help identify sources of pollution entering the bay and to help inform future policy decisions around mitigating nitrogen pollution. 

The overall project is funded by the U.S. Environmental Protection Agency’s National Estuary Program (NEP). The NEP works in place to protect and restore the water quality and ecological integrity of 28 estuaries estuaries designated as being of national significance, Casco Bay among them.

Walsh’s internship, separately funded by Maine EPSCoR’s Sustainable Ecological Aquaculture Network (SEANET), was a natural fit for the senior General Biology student, who hails from the Coastal Maine community of Saco.

“Growing up in Saco and being in the Portland area for most of my life, I’ve always loved the view and I’ve loved the bay. “It’s been an important aspect in my life,” he said.

Assessing Casco Bay

Walsh, 24, is one of four students who completed summer internships through Assistant Professor of Biology Rachel Lasley-Rasher’s ecology lab. Other projects included habitat restoration in the Penobscot River estuary; zooplankton diversity research; and optimizing scallop aquaculture practices.

Work monitoring nitrogen began in June. Utilizing the Green Eyes’ NuLAB system — what Bohlen describes as a “water quality robot” — he and Walsh worked throughout the summer to measure nutrient levels, specifically nitrogen, in the water off the Portland Street Pier in South Portland.

Tyler Walsh cleaning NuLAB systemNitrogen pollution can trigger water quality problems that are often called eutrophication, an excess of nutrients in the water. This is of concern because it can lead to the rapid growth of harmful algal blooms and the creation of hypoxic (oxygen-depleted) regions known as “dead zones” that are a threat to marine life.

According to CBEP data, stormwater runoff from lawns and city streets — which carries with it fertilizer, pet waste and other debris — accounts for 23-64% of nutrient pollution in Casco Bay. Human sewage accounts 36-58% of pollution, and enters primarily from wastewater treatment.

But without knowing the source of pollutants, and at what times they are most prevalent in the bay, it’s hard to pinpoint areas of improvement that could be fixed through policy. And even then, such improvements don’t come cheap.

“Knowing where the nutrients are coming from helps us figure out what are the most cost-effective investments for protecting water quality,” Bohlen said. “Projects cost millions to address; they’re not small investments for our communities.” 

A Novel Approach

The NuLAB system is unique in that it can take and process samples all on its own. For this project, the solar-powered robot collected water samples every two hours, running them through a wet-chemistry process to monitor for nitrate, nitrite and ammonium levels. The majority of the chemical work is done by the machine itself, and the researchers are able to check the machine’s status remotely.

The research can inform future policy decisions surrounding wastewater treatment, stormwater runoff and alleviating the effects of pollution on Casco Bay’s marine ecology. 

While Bohlen and Walsh haven’t completed their statistical analyses, they have been able to identify there is a relationship between rain events — specifically heavy rainfalls — with increased nitrogen levels in the bay’s waters.

“There is clearly a pattern with rainfall,” Bohlen said. “We see a jump in nitrogen concentration in almost every rainfall event.”

He also said there is a relationship with increased nitrogen and combined sewer overflow (CSO) events. These happen when the city’s sewer systems become overwhelmed due to large rain events, periodically leading to untreated sewage and runoff being washed into the bay.

“None of this is a surprise, but the pattern is exactly what we would expect if runoff is an important source of nutrients entering the bay. Knowing that can help us get a handle on pollution.” Bohlen said. “We’re figuring out how to invest intelligently in mitigating runoff from the urban landscape.” 

Making Professional Connections

Time spent working with CBEP not only helped Walsh gain field experience, he said, but it also gave him greater insight into working with community partners in a professional setting.

In addition to working with Bohlen, Walsh has worked with nonprofit groups and other environmental organizations; been exposed to a variety of scientific settings, both in and out of the lab; reviewed technical documents; and attended management committee meetings. 

Walsh with the NuLAB systemHe also presented at the SEA Fellows Symposium, held this summer at the University of Maine's Darling Marine Center, with three other interns from Lasley-Rasher’s lab, to an audience of more than 100 people.

“I do know that when you pick up an internship, not only do you want to check that box, you’re hoping you get to really learn something and get some real-world experience,” Walsh said. "I’ve definitely been provided that.”

Those skillsets — networking, collaboration and hands-on learning — are the true benefits of internships, said Lasley-Rasher, who teaches courses focused on ecology and organismal biology at USM.

“One of the most tangible benefits of an internship is the opportunity to network with potential employers in the local community,” Lasley-Rasher said. “These connections, coupled with relevant training, greatly increase the chance of a student landing a job after graduation.”

She said the same is also true with research experience, where students learn transferable skills like project-based learning, experience troubleshooting and collaborating with multiple research partners.

“From the undergraduate’s perspective, a research internship can help them think through potential career options,” Lasley-Rasher said. “They can get a feel for what it is like to work in a particular field and determine if they want to pursue a career in research.”

Symbiotic Relationship

The relationship between USM and CBEP is symbiotic, Bohlen said. While career preparedness is a factor in any internship, when students work with CBEP, they’re helping the organization collect data that will hopefully influence future public policy. 

"We try very hard as an organization to figure out: how do we strengthen the university by our presence, and how does the university strengthen our mission?” Bohlen said. “One of the primary ways we are able to do that is by looking for opportunities to connect students — whether that’s in classrooms or through internships — with the real-world environmental challenges that our region is facing.”

Tyler Walsh and Curtis BohlenCBEP encourages students to be effective participants in their local environment by engaging them with dozens of connected organizations, Bohlen said. The goal is to share those relationships with students so they understand not only the science behind their work, but also the process of policy development in a collaborative and positive way.

“When we have somebody working for us on an internship basis, we take it very seriously. This is a training opportunity; it is not just a job,” Bohlen said.

Lasley-Rasher echoed that sentiment.

“One of the benefits of students doing research with external partners is seeing the applications of the research beyond an academic setting,” she said. “Seeing that, in fact, these data may be used to inform decisions by resource managers or by local government agencies, allows them to be part of a larger system and gives a broader context to their work.”

The approach worked for Walsh, who said he has been able to build connections across the region while developing a passion for water quality issues here.

“Going to school in Maine, specifically at USM, I’ve always wanted to build a better connection with myself, with Portland and the southern Maine region, and I’ve really been able to do that,” he said.

Walsh will earn his Bachelor’s degree in December, and is currently exploring options for after graduation. He is interested in becoming a volunteer with the AmeriCorps conservation corps programs, but may pursue further research or a master’s degree program.

But whatever the case, he said, he’ll be prepared.

“I think the one thing that I’ve learned about myself is I’m constantly finding new things that I enjoy and that I want to get into. I don’t exactly know what I want to do, but I’m content with trying new things and getting myself out there.

“I firmly believe that USM has provided that foundation for me,” he said.


Watch: Walsh and Bohlen talk about their research on "The USM Update"

Story, photos and videos by Alan Bennett // Office of Public Affairs