Could a byproduct of green hydrogen breathe life into Gulf of St. Lawrence dead zone?
Low oxygen levels in deep water are now a permanent feature in parts of the Gulf
Oxygen created from the production of green hydrogen could help stem a growing dead zone at the bottom of the Gulf of St. Lawrence, according to new research by Canadian scientists.
Marine dead zones are occurring around the world, including in the Baltic Sea and off the coast of China.
The Gulf of St. Lawrence dead zone is the result of nutrients that consume oxygen and a shift in ocean currents carrying colder rich waters away from the Gulf.
Dead zones threaten marine species, which need oxygen to live, eliminating habitat for less mobile species like crab and mussels and shrinking habitat for others, making them more vulnerable to predators.
Hydrogen as a renewable fuel is produced when water is broken down into its component elements. Oxygen is a byproduct of the process.
Chemical oceanographer Doug Wallace says it could be pumped into the gulf to alleviate conditions that threaten marine biodiversity.
"The amount of oxygen that will be produced as a byproduct of hydrogen generation through electrolysis of water is more than enough, we've calculated, to compensate for the annual decrease in oxygen that's been going on now for some years," says Wallace, a professor at Dalhousie University in Halifax.
He proposed the strategy in a scientific paper co-authored with Quebec researchers and published in late 2023.
There are still many unanswered questions about the feasibility of injecting large amounts of oxygen into deep waters, but the authors say it's a potential solution to one of the most serious threats facing the Gulf of St. Lawrence.
Causes of the Gulf dead zone
Low- to zero-oxygen levels in deep water are now a permanent feature in parts of the gulf — a condition known as hypoxia.
The hypoxic zone is now 9,000 square kilometres — up from 1,300 in 2003 — and spreading from the western St. Lawrence to Anticosti Island and northward.
It's the result of nutrients flowing down the St. Lawrence River forming algae blooms that sink to the bottom and consume oxygen.
Climate change is also contributing, particularly because of a near total stoppage in the flow of cold, oxygen-rich water from the Labrador current into the gulf through the Cabot Strait between Nova Scotia and Newfoundland
"I don't know if we have right now a firm prediction of what the new steady state would be, but certainly we can expect the extent of hypoxia and the intensity of hypoxia to continue to increase," says Wallace.
Tracing possible oxygen flow
The oxygen-injection theory was tested in October 2021, when several hundred grams of an inert gas — that moves like dissolved oxygen and can be traced — was released at a depth of 250 metres in the Cabot Strait, 130 kilometres south of Stephenville, N.L.
When measured a year later, researchers say the tracer followed the mixing and spreading of sub-surface water within the Gulf and demonstrated that injected oxygen would reach threatened areas in 18 months to four years.
The research was funded by the Marine Environmental Observation, Prediction and Response Network and Reseau Quebec Maritime.
A Stephenville connection
Stephenville could be a likely source of the oxygen if plans proceed to build up to three wind-powered hydrogen and ammonia production projects.
In August 2022, Prime Minister Justin Trudeau and German Chancellor Olaf Scholz visited the town to sign an agreement to promote hydrogen fuel exports to Germany.
"The implication is that artificial addition of oxygen into subsurface waters close to where it is to be produced from hydrogen/ammonia plant(s) has potential to mitigate future deoxygenation throughout the Gulf of St Lawrence, including within the already hypoxic Lower St. Lawrence Estuary 700 kilometres 'downstream,'" the paper states.
Can it be done?
Engineering, scientific and financial questions remain. Who pays, can it be scaled up and done safely without creating negative side effects?
"I think those risks are minimal, but they need to be thought about and studied," says Wallace.
One potential testing ground is the Bedford Basin in Halifax.
It too is impacted by pollution and in recent years deep water in the basin has become seasonally hypoxic.
"Testing some aspects of this, especially effects on marine life and the feasibility of different injection methods could potentially be done in a small fjord like the Bedford Basin," Wallace says.
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