REHOBOTH BEACH — A new research effort by the Delaware Center for the Inland Bays aims to offer deeper insight into the true state of water in the most polluted areas of the bays.

Continuous monitoring devices called “sondes” are part of a new network of sensors that collect water-quality data every 30 minutes, 24 hours a day, at five locations in the Inland Bays watershed, a news release from the center stated.

This network is part of the center’s recently updated environmental-monitoring plan for the Inland Bays, which aims to track the status and trends of indicators to gauge the health of the waterways, their tributaries and the fish and shellfish that depend on them.

Expanding water-quality monitoring is a key recommendation of the plan, which will help scientists learn more about the state of the water and the conditions in the Inland Bays. That knowledge will help inform management decisions, while also educating the public and providing scientific support for the resources and policies needed to restore the watershed, the release added.

“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. Marianne Walch, the center’s science and restoration coordinator, said in the release. “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.”

In addition to expanded monitoring efforts, the center’s plan outlines the need for studies of bay grasses (which are a good indicator of water quality), identification of emerging contaminants, the impact of sea-level rise, oyster growth, shoreline and marsh changes and more.

According to the release, the center is already gaining insight from continuously collected water-quality data.

For example, during recent fish kills reported in the Rehoboth and Indian River bays, the center’s monitors recorded extremely low oxygen levels in multiple areas — indicating that the unhealthy conditions and the resulting death of marine life (over a million menhaden in June) are neither isolated nor uncommon this time of year, the center said.

“Despite the millions of dollars that have been put into management actions, water quality in many parts of our Bays is not improving,” Dr. Walch said. “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.”

Intense algae blooms, which are driven by nutrient pollution from agricultural and urban runoff, are common in the bays in the summer, the release noted. They also lead to low levels of dissolved oxygen, which fish and shellfish need to survive.

The center’s sondes serve as “continuous eyes on the bays,” collecting data on dissolved oxygen levels, salinity, water clarity, pH and temperature in the Indian River, Pepper Creek and Guinea Creek, the release added.

Data shows that between June 1 and Oct. 1, 2020, oxygen levels in the upper Indian River failed to meet the state’s water-quality standard for dissolved oxygen on 75% of mornings. On five occasions, dissolved oxygen levels remained below the healthy limit for eight hours or longer. Similar conditions are being observed this summer.

The center has partnered with the University of Delaware on this project, with plans to install additional stations in 2021 and 2022.