Susquehanna's Impact Downstream
We started our science careers studying Pennsylvania lakes and streams that feed into the Susquehanna River with Professor of Biology Jack Holt. Little did we know that our work on diatoms (single-cell phytoplankton often used to assess a body of water's health) in the freshwaters of central Pennsylvania would lead us to monitoring the health of the nation's largest and most productive estuary. After earning our biology degrees from Susquehanna, we both continued to study algae during graduate school at Old Dominion University in Norfolk, Va. Today we comprise the phytoplankton monitoring team for the Chesapeake Bay Monitoring Program, a federal initiative that has been monitoring water quality, phytoplankton, zooplankton and fisheries health throughout the Chesapeake Bay Watershed for more than 40 years.
More than 50 percent of the freshwater entering the bay is delivered by the Susquehanna River, making the health of the Susquehanna vital to the health of the Chesapeake. The river drains 27,500 square miles, including half the land in Pennsylvania, via its northern and western branches and hundreds of tributaries, and empties into the Chesapeake at Havre de Grace, Md. As of 2009, 36 percent of all the nitrogen and 25 percent of all the phosphorus entering the bay were coming from the Susquehanna, which accumulates these nutrients mostly from residential fertilizers
and agricultural lands in its drainage basin.
In abundance, nitrogen and phosphorus lead to a decline in water quality because these nutrients stimulate phytoplankton, or algae blooms. Prolonged algae blooms deplete the oxygen levels in the water and block the sunlight needed by submerged aquatic plants. Low oxygen levels, the destruction of aquatic plant habitats, and the possibility of toxins being produced by algal blooms negatively impact fish and other living resources in the bay.
Over the past 20 years, there has been a marked increase in harmful algal blooms in the Chesapeake, and it's on this problem that we do most of our collaborative research. We work together to characterize the taxonomy and toxicity of harmful algal species in an effort to help create biotoxin contingency plan guidelines and predictive models for monitoring.
In 2015, there were a number of extraordinary algal blooms in Maryland and Virginia. Building off of the electron microscopy skills we initially learned from Professor Holt, we identified several toxic algae species of Dinophysis, in the region. Dinophysis produces toxins harmful to humans who consume the fish and shellfish exposed to them. Similarly, we are studying the impact of a large bloom of the bioluminescent and toxin-producing algae Alexandrium monilatum in the southern bay and Virginia Beach oceanfront. These deadly, but beautiful, organisms thrive on high nutrient levels.
Research that focuses on methods to reduce nutrient input upstream, including the Susquehanna River and its tributaries, is crucial to implementing management practices that will aid in the reduction of harmful algal blooms throughout the estuary. The work being done through the new Freshwater Research Initiative at Susquehanna will provide critical data for understanding where impacted waters are upstream of the Chesapeake Bay and how those nutrient loads are impacting the overall watershed. Even more importantly, we hope the newest generation of students involved with the Freshwater Research Initiative finds the same passion for aquatic sciences that we did at Susquehanna, and that they turn that passion into careers that help contribute to conservation and restoration efforts in their own communities.
Jennifer Wolny Shurtleff leads phytoplankton research for the Maryland Department of Natural Resources, and Todd Egerton is an adjunct biology professor and directs the Phytoplankton Analysis Lab at Old Dominion University.