REHOBOTH BEACH, Del. — Advanced monitoring technology is revealing troubling details about contamination levels in Delaware’s most polluted waterways, according to new findings from the Delaware Center for the Inland Bays.
The organization has deployed specialized underwater sensors known as “sondes” that gather environmental data around the clock at five strategic points throughout the Inland Bays watershed. These blue monitoring devices record water conditions every half hour as part of the Center’s newly revised Environmental Monitoring Plan for Delaware’s Inland Bays.
This comprehensive monitoring strategy focuses on tracking critical environmental factors to assess the overall health of the bay system, its connecting waterways, and the marine species that call them home. The enhanced surveillance efforts represent a crucial element of the plan, designed to provide scientists with detailed information about actual environmental conditions in the Inland Bays.
According to Dr. Marianne Walch, the Center’s Science & Restoration Coordinator, sustained monitoring efforts are essential for multiple reasons. “Long-term monitoring is key to not only understanding the health of our Bays, but also to evaluating the effectiveness of the many investments that have been directed at improving water quality and habitats,” Dr. Walch explained. “The Environmental Monitoring Plan is intended to guide future research and increase the integration and efficiency of monitoring efforts across organizations involved in collecting data.”
Beyond water quality surveillance, the Center’s comprehensive plan encompasses research into baygrasses (which serve as reliable water quality indicators), identification of new pollutants, monitoring sea-level rise effects, oyster development, and changes to coastlines and marshlands.
The continuous data collection has already provided valuable insights during recent environmental crises. When fish die-offs occurred in both Rehoboth and Indian River Bays, the monitoring equipment documented dangerously low oxygen concentrations across multiple bay locations. These findings suggest that harmful conditions and resulting marine deaths — including more than one million menhaden fish in June alone — represent widespread seasonal problems rather than isolated incidents.
Dr. Walch noted concerning trends in the data, particularly from Indian River sections. “Despite the millions of dollars that have been put into management actions, water quality in many parts of our Bays is not improving,” she stated. “Data collected monthly or bimonthly by the state of Delaware does not reveal the full picture of what is actually happening in polluted areas. That points out the importance of the Center’s work to collect and share high-frequency data.”
Severe algae outbreaks, fueled by nutrient contamination from farm and city runoff, regularly plague the bays during this season. These blooms deplete dissolved oxygen that marine life requires for survival.
The monitoring network functions as constant surveillance of bay conditions, measuring dissolved oxygen, salt content, water transparency, pH levels, and temperature at locations throughout Indian River, Pepper Creek, and Guinea Creek.
Information gathered between June 1, 2020, and October 1, 2020, revealed that oxygen concentrations in upper Indian River fell short of state water quality requirements on 75% of mornings. During five separate periods, dissolved oxygen remained below safe thresholds for eight hours or more. Researchers are documenting similar patterns during summer 2021.
The Center has formed a partnership with the University of Delaware for this initiative, with additional monitoring stations planned for installation in 2021 and 2022.
Details about this research project appear in the Spring/Summer 2021 edition of the Inland Bays Journal, a complimentary quarterly publication showcasing the Center’s initiatives and achievements. The Journal reaches anyone enrolled in the Center’s mailing list through inlandbays.org/mailing.
Nitrogen and phosphorus nutrient contamination continues to pose the most significant danger to bay water quality. The Center is currently developing a five-year update to its State of the Inland Bays report, which will present the most recent data on bay conditions.
Established in 1994, the Delaware Center for the Inland Bays operates as a nonprofit organization and serves as one of 28 National Estuary Programs. Working alongside numerous partners, the Center focuses on preserving, protecting, and restoring Delaware’s Inland Bays and surrounding watershed areas.
