By Reagan Gulledge
Algal blooms are probably not the first thing that comes to mind for many people when watching television for the latest hurricane updates. When these powerful storms make landfall, people are similarly unlikely to consider algal blooms and their impact on local water quality as a major consequence. However, the torrential downpours accompanying hurricanes can cause extensive flooding, ultimately bringing large amounts of nutrient-laden runoff to downstream waters. Excess storm-driven nutrient loads entering nutrient-sensitive waters can promote the proliferation of harmful algal blooms (HABs) from the freshwater sources to the marine continuum that characterizes North Carolina’s coastal zone.
When Hurricane Floyd slammed down onto the coast of North Carolina in 1999, it resulted in major changes in water quality for the Pamlico Sound because of intense flooding, accompanied by sediment and nutrient loading. This inciting event prompted Hans Paerl, Ph.D., to dig into the hurricane’s impact on water quality in the Sound. As Paerl stated, “It’s interesting how catastrophes often lead to opportunities.”
In this case, the opportunity was FerryMon – a ferry-based water quality monitoring project developed by Paerl and his colleagues at the University of North Carolina at Chapel Hill’s Institute of Marine Sciences in Morehead City and Duke University’s Marine Lab.
Taking inspiration from Finish research happening in the Baltic Sea, where large ferries autonomously collect water samples and record data on its quality during their transits, Paerl leveraged two ferries, one in the Pamlico Sound and another in the Neuse River Estuary, to implement a similar program. Paerl’s research, which has now been running for 24 years, analyzes numerous factors, including intense, potentially toxic HABs, accompanied by low dissolved oxygen conditions, and pH changes using an automated flow-through system that continuously collects environmental data and water samples and transmits the data to the lab via the internet while the ferries travel down the waterway.
Since these ferries operate almost daily, transporting commuters, visitors, and supplies, Paerl’s research project was cost-efficient in its inception. These ferries serve as ships of opportunity – providing a chance to understand the impacts of storms on water quality. The innovative use of these ferries enables the researchers to capture water quality measurements in real-time, linking fluctuations to meteorological events.
Water Quality Fluctuations Prompt Algal Growth, Impacting Marine Life
Salinity and temperature fluctuate considerably in the presence of storms, especially in the large Pamlico Sound. Both parameters are also important factors in determining the growth rate of algae and impact finfish and shellfish habitat conditions. As the Sound is also connected to coastal waters, the salinity and temperature fluctuations can vary depending on the quantity of freshwater coming in compared to the coastal water tidal exchange. Changes in the wind direction, speed of water currents, and river elevation can also cause nutrient-rich bottom water to upwell on one side of the estuary, which promotes algal blooms growing and accumulating in specific areas.
Algal blooms do not grow uniformly and can even proliferate while invisible to the naked eye. “They are what I call raisin cookies: You get some dense areas of bloom and some not dense areas,” described Paerl. These dense areas greatly affect the water quality as potentially toxic algal blooms accumulate and dissolved oxygen levels decrease. FerryMon collects and analyzes these water samples to determine the type of algal blooms and their impacts on water quality.
Data Collection Aboard the Ferries
FerryMon is a complex system, but you wouldn’t know it standing aboard the boat. Most of the necessary equipment is located below the deck. The ferry is designed to take in water through the bow, where it is then transported to a plenum – a large tank containing sensors – to detect various water quality parameters, including dissolved oxygen, pH, temperature, salinity, and chlorophyll. The levels of these parameters are essential because they play a critical role in supporting marine life. Water samples and the initially collected data are sent to the lab for further analysis of the chlorophyll, which indicates the presence of algae, pathogens, organic pollutants, nutrients, and chemical constituents.
FerryMon also utilizes a carousel system to sample water intermittently and a global positioning system (GPS) to record latitude and longitude. When the ferry boats are in transit, the water quality parameters and spatial coordinates are measured and recorded at one-minute intervals. These GPS points are essential for learning where major algae blooms may occur and determining geospatial trends in the water quality data.
Importance in a Changing Climate
Paerl and his team are a part of the Albemarle-Pamlico National Estuary Partnership (APNEP), an organization focused on protecting and restoring the essential resources in the estuary system. APNEP was established after the Clean Water Act was enacted and comprises different committees and partners working collectively to improve the natural world. The FerryMon project falls under APNEP’s Monitoring and Assessment Committee, which provides data and analysis to other national estuary partnerships for implementing new strategies to protect estuarine resources. William (Bill) Crowell, Ph.D. and director of APNEP, shared how FerryMon benefits the community: “FerryMon is unique because of the way it gathers data – it gives us information we would not be able to collect otherwise.” APNEP hopes that FerryMon will help them assess trends that have occurred in the past and predict future water quality parameters.
“It’s a program for all times and all seasons,” stated Paerl.
Record-breaking storms are an increasingly common occurrence, and it is important to observe the impact of such storms on the marine environment and water quality parameters. Paerl and his research team are working on making portable sensing systems that can, conveniently, be loaded onto any ferry, allowing for more geographic flexibility in research opportunities. “It’s a program for all times and all seasons,” stated Paerl.
In 2021, the FerryMon project began receiving funding from the NC Collaboratory, ensuring the continuation of the long-term water quality monitoring in the estuaries. FerryMon is a joint project with ModMon (modeling and monitoring), and together, the projects have received approximately $660,000 in funding from the Collaboratory to continue the research.
The future of FerryMon is only expanding, promising to provide new data about the future of water quality. With the help of the NC Collaboratory in addition to the guidance of APNEP, FerryMon will continue to be integral in the search for the right solution to best combat human and climatically driven change in local waters. The climate is forever changing, and major storms are hitting the country around the clock, but Paerl and his team are confident in the unique data that this project is providing. FerryMon aids scientists in finding the right management solutions and mitigation steps to ensure acceptable water quality conditions are met in these changing times.
Reagan Gulledge is a junior environmental science major with a chemistry minor. She joined the NC Collaboratory as a Communications Intern in the fall of 2024.