Dark Data Sheds Light on Shellfish Parasites

Take a drive along Maine’s State Route 129, and as you wind along the Damariscotta River estuary, you will pass lobster boats, agricultural fields — and a series of oyster farms. Shellfish aquaculture has been growing in Maine, and it may play an essential role in the future of the state’s coastal economy.

However, shellfish growers in Maine need more information about a significant threat to the aquaculture industry, according to several Bigelow Laboratory for Ocean Sciences researchers. Single-celled parasites are one of the main threats to aquaculture programs around the globe. The diseases they cause in shellfish have the potential to hurt thriving farms in Maine, as the state saw during an oyster die-off in 2010 that was blamed on the parasite Haplosporidium, popularly known as MSX.

“If you want to grow oysters or other shellfish, you need to have a baseline of information about the parasites that could infect them,” said José Fernández Robledo, a Senior Research Scientist at Bigelow Laboratory who specializes in molecular biology and parasitology.

One wintry day in 2015, Fernández Robledo went snowshoeing with Senior Research Scientists Pete Countway and Nick Record along the trail network outside Bigelow Laboratory. As they trekked through the fresh snow, the scientists discussed writing a review article to explore the history of shellfish disease in Maine. A historical survey would provide crucial baseline information about the presence of shellfish parasites in Maine and enable each scientist to study these parasites from a different angle.

Countway is working to assess how many different single-celled organisms, such as oyster parasites and harmful algae, exist in Maine’s coastal environments today. He plans to quantify how abundant they are, and characterize whether it is possible to detect them in seawater by looking for their genetic signatures.

Record writes algorithms that allow him to mathematically forecast populations of animals in Maine like jellyfish and ticks. This historical data would allow him to develop algorithms to forecast future parasite infections, just like meteorologists forecast the weather.

Fernández Robledo uses molecular biology techniques to study the oyster genome. He plans to look for strains of oysters that are resistant to parasites and could be useful for farmers who want to selectively breed their stocks for resistance.

Each of these approaches can help shellfish farmers anticipate and prevent the spread of shellfish diseases caused by parasites. Together, they comprise a comprehensive and multi-faceted effort to equip and inform Maine’s aquaculture industry.

“One of our primary goals is to find linkages between the parasite diversity we see in the seawater and the genetic signatures they leave in the shellfish,” Countway said. “This could provide us with critical information to help us understand the sources and timing of parasitic infections of shellfish.”

Laying the necessary groundwork for these future studies required the researchers to find every peer-reviewed publication about shellfish disease in Maine. They mined old books and journals to illuminate “dark data,” information gathered before the digital age.

“The past always has lessons about the future,” Record said. “The historical record often gives us key information about how quickly an ecosystem can change and allows us to predict future changes."

To help conduct the survey, the researchers teamed up with several students who had spent time at Bigelow Laboratory in the <a href="/education/reu"; target="_blank">Research Experience for Undergraduates internship program, the <a href="http://www.colby.edu/bigelowprogram/changing-oceans"; target="_blank">Colby-Bigelow Changing Oceans semester program, or as part of their undergraduate research.

What the team found surprised them. Out of all the peer-reviewed publications about shellfish disease in Maine, most reports focused on oysters in the Damariscotta River Estuary, with relatively few papers about the rest of the state. These reports were published sporadically over the last several decades and largely in response to specific oyster die-off events rather than representing a steady progression of research.

“Maine needs to make an effort to have a more extensive and routine parasite monitoring program,” said Fernández Robledo. “To make informed decisions, we need to be proactive about conducting research rather than just responding to problems.”

Fernández Robledo, Countway, and Record have begun the next phase of this research already. With funding from the NOAA Saltonstall-Kennedy Grant Program, they are conducting the largest-ever survey of oyster parasites in Maine. When they finish, they hope to create a map of pathogen “hotspots” across the state, provide guidelines to help aquaculturists keep their shellfish stocks healthy, and help inform local agencies making management decisions.

“We see ourselves as independent observers, or as lighthouses that can warn of hidden hazards,” said Fernández Robledo. “Through this study, we can provide the industry with the information it needs to chart the best course forward.”