The National Science Foundation has awarded $1 million to a team of researchers at the University of Maryland Center for Environmental Science to study how the nutrient plume of the nation’s largest estuary, the Chesapeake Bay, changes over the course of the year and what those changes mean for food webs and nutrient cycles in the coastal Atlantic Ocean. This knowledge is pressing imperative to accurately update estuary-ocean food web models for long-term shifts in regional climate and the changing frequency and severity of extreme weather events in many regions.
“We'll be going out to the inner continental shelf over the next several years with the ultimate goals of developing a hydrodynamic model of the Chesapeake Bay plume and gathering empirical and experimental data focused on understanding how the plume drives productivity at the base of the coastal food web,” said UMCES ecologist and Assistant Professor Ryan Woodland, who is leading the three-year project.
In the coastal ocean areas affected by river or estuarine plumes, nutrient-rich river or estuary waters mix with less-enriched marine waters; these very productive regions are important for fisheries and nutrient cycling. The location and size of these estuary plumes are highly variable in space and time because of seasonal changes in winds, river flows and ocean currents. The amount of nutrients carried by plumes— and their impact on the coastal ocean—also changes seasonally.
“The areas where estuaries and shelf habitats intersect are super dynamic. There’s a lot of interacting processes going on. All of the nutrients coming out of the rivers are mixing with oceanic water in these shallow areas. Phytoplankton is growing, and animals are eating the phytoplankton. It can be a really productive area for fisheries,” Woodland said.
The scientists will embark on a series of scientific research cruises off the coast, sampling 21 fixed stations to see how the community is changing over time. They will start with the base of the food web – organisms that live on the bottom like worms, clams, snails, shrimp, and tiny crustaceans. Woodland will lead biological and ecological sampling, using underwater grabs and sleds to gather samples of the organisms within the bottom sediment and living just above the sediment to count, identify, and calculate their productivity.
UMCES Professor Ming Li, who studies the regional impacts of climate change and extreme weather events on estuaries and coastal oceans, will develop a model of water movements to predict how river flow, winds, waves, tides, and currents converge to cause seasonal changes in plume size, location, and composition.
Associate Professor Jeremy Testa, who studies the processes of eutrophication, nutrient cycling, and dissolved oxygen dynamics in coastal waters, will capture and incubate sediment to understand how patterns of sediment metabolism change in relation to plume location.
Experiments conducted on the ship will also investigate how the animals and the chemical reactions in the sediment respond to materials produced and moved within the plume. To do this, UMCES scientists will conduct experiments on the ship using isotopes to trace which different types of nutrients and foods are being consumed by bottom-dwelling species in the different areas on the shelf.
“We want to get a better handle on the processes that influence the productivity of these food webs that support fisheries and develop a better understanding of the interactions and that effect the ecology of zones between rivers and estuaries and shelves,” said Woodland. “Historically, the scientific focus has been on what’s in the water column, but fewer studies have looked at the bottom and how the plumes affect the spatial and temporal structure and productivity of bottom food webs.”
Researchers will share findings with regional fisheries management groups to ensure relevant information is available for ecosystem-based management applications.
The project will also support graduate and post-doctoral researchers, along with an internship program with the College of Southern Maryland as part of an ongoing effort to increase diversity in the STEM fields and give local students a real taste of geosciences and ecology. Students will spend 10 weeks at UMCES Chesapeake Biological Laboratory working alongside their scientific mentors, learning and applying research methods and techniques, and participating in a research cruise off the coast that semester to gain valuable, hands-on experience.