UNCW's Mike Mallin and Larry Cahoon Part of $350,000 Greenfield Lake Project

Monday, May 18, 2020

UNCW research professor Mike Mallin and professor Larry Cahoon are involved in a $350,000 collaborative effort to reduce the flow of nutrients that feed pervasive algae growth in Wilmington’s Greenfield Lake. The grant, which includes $206,485 in federal money and $140,308 in matching or in-kind services, was awarded by the NC Department of Environmental Quality with funding that originated with the Environmental Protection Agency. 

“The problems in Greenfield Lake have been growing for decades,” said Mallin, whose research on the water quality of the manmade lake spans more than two decades. “Having seen the shape that the lake is in, with fish kills and other ecological concerns, it is particularly gratifying that the state is coming through with this funding so we can do something tangible.” 

Partners on the project include Cape Fear River Watch, which is administering the grant; North Carolina State University; the City of Wilmington; and global infrastructure advisory firm Moffatt & Nichol. Collaborative research involving other universities, communities and community organizations are among priorities outlined in UNCW’s 2016-21 Strategic Plan. 

“The work of Dr. Mallin, Dr. Cahoon and their community and university partners to identify the sources of and reduce excess nutrients in Greenfield Lake is an example of research with local impact that UNCW continues to encourage,” said Stuart Borrett, associate provost for research and innovation. 

The website for Cape Fear River Watch describes the shallow lake as suffering from “green and blue-green algal blooms, bottom-water hypoxia, fish kills and high fecal coliform bacterial counts.” It is included on the state’s list of impaired waters. 

In a peer-reviewed article in 2016, Mallin, UNCW primary investigator on the project, outlined the history of the lake, the degradation of its water quality and how it came to be placed on North Carolina’s impaired waters list. In his master’s thesis, former UNCW graduate student Nick Iraola18M outlined the Jumping Run and Squash branches as the two main sources of nutrients in the lake. This project focuses on Jumping Run, which collects stormwater runoff from a heavily developed area in midtown Wilmington and flows underneath 16th and 17th streets toward the urban lake. 

One component of the multi-tiered restoration plan will involve building up the wetlands near the branch and building a “riser” structure that operates much like a dam. Its purpose is to hold stormwater long enough to trap and remove nutrients before sending water into the lake. Another element will focus on mitigating the flow of nutrients from a stormwater detention pond that overflows into Jumping Run. Cahoon and two graduate students will focus on reducing the conversion of nitrogen gas into algae-feeding nutrients. 

Our hope is to cause a decrease in nitrogen fixation (driven by phosphate-loving cyanobacteria, or blue-green algae, which bloom in the lake) and an increase in denitrification, so that the lake receives less nitrogen overall and will then become less likely to have noxious algae blooms,” Cahoon said. 

UNCW’s share of the three-year grant totals $82,928. 

-- Tricia Vance