Blue carbon is a key consideration in the fight against climate change. The term refers to carbon stored by the ocean, including carbon that has been buried in marine sediments.
Dalhousie PhD candidate Haley Geizer, with supervisor Dr. Christopher Algar of Dalhousie’s oceanography department, is currently studying the rate of carbon burial in Arctic and Subarctic marine sediment to better understand these processes in the Canadian North. This has been identified as a critical gap in scientific literature. Geizer’s research is supported by the Ocean Frontier Institute’s Ocean Graduate Excellence Network (OGEN) program, thanks in part to funding from the Canada First Research Excellence Fund, as well as the National Sciences and Engineering Research Council (NSERC) and Fisheries and Oceans Canada.
Carbon storage
Carbon storage in sediment starts with tiny, microscopic organisms floating at the sea surface. These organisms, called phytoplankton, carry out photosynthesis, using sunlight to produce oxygen, which in turn removes carbon dioxide. This process is also known as carbon fixation as the organisms take carbon from the atmosphere and store it in their bodies.
When the phytoplankton die, they sink throughout the water column. A small fraction make it all the way down to the seafloor, taking the captured carbon with them. Once there, other microbial communities will break down that material, releasing nutrients and carbon dioxide that can resurface with ocean mixing. Those nutrients, when at the surface, help start the process all over again. Any of the material that escapes breakdown by microbes is stored as sediment, effectively locking it away. This buried carbon can potentially be stored for thousands of years.
“Understanding where carbon is going is really important to predict future warming,” says Geizer.
“I look at how much carbon is stored in sediment versus how much re-enters the water column to hopefully improve the accuracy of climate models.”
Sampling in the North Atlantic
Geizer joined her first research cruise shortly before she started graduate school, collecting samples and learning about marine carbon on the spot.
“I have a background in environmental science,” says Geizer.
“I didn't know much about the ocean at first. I remember being at sea and my supervisor explaining the different biogeochemical processes in the ocean. I was writing everything down and learning in the moment.”
That year, Geizer spent six weeks at sea. She has since participated in three additional research cruises aboard the CCGS Amundsen in the North Atlantic, where she joined colleagues in collecting samples along the Nunatsiavut shelf, several northern fjords, and off the coast of Nunavut. In this collaborative environment, other researchers study the same sites from different angles including: larger benthic animals, phytoplankton communities, fishes communities, eDNA, water column chemistry, deep sea corals, and much more. Together, this diverse research group paints a detailed picture of each sampling location.
Geizer says the scientific community has continued to inspire and impact her research. “Oceanography is really multidisciplinary—You’re looking at questions from so many different lenses. Our lab studies biogeochemistry, but discussions with other researchers with different perspectives led to more questions that we can help to answer. How does melting subsea permafrost impact carbon storage? What does the geochemistry of a fjord look like? How would a submarine landslide impact carbon storage? All of these questions arose on the spot and have become integral parts of this project.”
Analyzing the data
The four research cruises that Geizer participated in provided a large number of samples for the project. The next step is to put it all together. Geizer will input her data into a simple model that will imitate the chemistry in the natural environment at each sampling location. Once the model is accurately mimicking the carbon storage processes, Geizer can change variables such as temperature to see how processes might shift with a warming climate.
“It’s amazing what you can learn in a few years when you dedicate yourself to one topic,” says Geizer.
“I feel lucky to be contributing information that will improve the accuracy of climate predictions and I’m excited to start connecting the puzzle pieces of my project.”
