Bedford Basin perfect to monitor coastal climate change, scientists say

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PhD student Brent Robicheau at work on environmental DNA testing of phytoplankton at Dalhousie University in Halifax. (Robert Short/CBC - image credit)
PhD student Brent Robicheau at work on environmental DNA testing of phytoplankton at Dalhousie University in Halifax. (Robert Short/CBC - image credit)

An underwater fiord in Halifax harbour could help monitor the effects of climate change along the Atlantic continental shelf, according to a new study.

Using tests that detect trace amounts of genetic material, scientists say the Bedford Basin is home to many of the microscopic organisms called phytoplankton that form the base of the ocean food chain.

What happens in the 17-square-kilometre basin could be an indicator of what is occurring in coastal waters.

"I think really the main important thing was seeing how similar it was to the Scotian Shelf in terms of the community composition," said Brent Robicheau, a PhD student at Dalhousie University in Halifax.

Robicheau co-authored a paper on the findings that was published earlier this month in the microbial ecology journal ISME Communications.

The paper concludes the easily accessible and frequently monitored Bedford Basin is a "perfect backdrop" to assess future effects of climate change.

Robert Short/CBC
Robert Short/CBC

Tiny creatures in both places

The Department Fisheries and Oceans has monitored the basin weekly for a variety of conditions like temperature, salinity, oxygen and basic phytoplankton levels since 1992.

In 2014, scientists based at Dalhousie in collaboration with DFO started sampling with environmental DNA, which provided more detail about the population.

Using sampling data from 2014 to 2017, the study found about 85 per cent of dominant plankton species in the basin were also present on the Scotian Shelf during the annual spring and fall at-sea survey conducted by DFO vessels.

It said 66 per cent of the dominant plankton on the Scotian Shelf were present in the basin. Researchers suspect they respond the same way to changing conditions.

More smaller phytoplankton species than expected in the basin grew in 2016 when water temperatures were unusually warm — a potential indicator for climate change effects.

Dalhousie University
Dalhousie University

"We want to track the current members of the phytoplankton community, find out how various members respond to hotter temperatures during the time series, and then use this info to inform how the community may shift in connection to the effects of climate change,'' said Robicheau.

The sampling in the basin is part of a joint program between Dalhousie University, the Ocean Frontier Institute and MEOPAR, the Marine Environmental Observation Prediction and Response Network.

The environmental DNA testing is being carried out by the laboratory of Dalhousie biology professor Julie LaRoche, a co-author of the paper.

Dalhousie University
Dalhousie University

'Much more accessible'

She said the basin is a useful place to study specific processes like phytoplankton blooms and nitrogen cycling by microbes, which helps feed microorganisms. It can detect immediate changes because it is easy to reach and cheaper to study.

"It's much more accessible," she said. "Coastal basins like the Bedford Basin are important to the community. So what happens if there's pollutants or anything like that, that if the conditions might change, then we will be able to follow it."

The basin has its limitations. It cannot replicate major open ocean processes like oxygen transfer in the Labrador Sea, where the sea floor is 2,000 metres deep versus 71 metres in the basin.

Still, the detailed record being amassed by weekly sampling makes it a good surveillance tool.

Robert Short/CBC
Robert Short/CBC

"We can spot early changes that are created due to climate warming or even other types of human activities in the region. So we have the data to do this because of this extensive baseline that we have now, and we also have archived samples," said LaRoche.

"We can go back to that in decades later to see if things have changed."

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