I’m heading a research project across the country, for Fisheries and Oceans Canada,
on low oxygen areas.
By low oxygen areas, we mean those areas of the ocean where oxygen is so low that some
fish are starting to have trouble breathing, which means in practice that they have to
escape to other areas where there is more oxygen.
There can be a loss of habitat for
fish, so some areas that were once good for living -- are no longer good for them to live
in and they have to go away.
The first way in which climate change can affect oxygen has to do with the fact that
the water is expected to warm at the surface.
In warm water, you have less possibility for
dissolving gases, so that means you dissolve less oxygen.
The second factor has to do with the fact that with climate change, we’re expecting
the surface water to warm faster than the waters that are beneath them, and that means
that this water at the surface is getting lighter and lighter, and it becomes harder
to mix this water with dense water at the bottom, and the fact that it becomes harder
to mix water, means you will also be injecting less oxygen into those deeper waters.
We’ve noticed the change in oxygen largely through long terms monitoring programs conducted
by Fisheries and Ocean Canada, both on the west coast in the Gulf of Alaska, and also
on the east coast at various sites off Nova Scotia, Newfoundland, Quebec, New Brunswick,
looking at how oxygen is changing.
Through the last decades, we’ve seen declining trends, a tendency for oxygen to go down over
the years.
Some of the impacts we have started to study for cod, range from swimming ability - when
there’s less oxygen, fish tend to swim less fast.
There’s also the issue of growth.
Some oxygen concentrations are not necessarily lethal in the sense that they will not kill
the cod, but they can nevertheless have an effect on the growth.
A cod that is three
years old with low oxygen, will be smaller that one that has lots of oxygen.
In Canada, there’s been two main areas where we’ve seen stress in terms of oxygen in
the marine waters.
One of those areas is off the coast of B.C.
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We’ve seen these (areas) creep up the continental slope and reach shallower depths, which presents
possibly a loss of habitat for certain ground fish species.
On the east coast, the deep
waters that are in the Gulf of St Lawrence, and in particular in the lower St Lawrence
Estuary, right in front of Rimouski, is a place where the levels of oxygen are considered
so low that they are now inhospitable to cod.
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So Fisheries and Oceans Canada is funding research at a number of labs across the country
to figure out how fish are changing their distribution patterns with respect to oxygen;
how those fish might redistribute in the future as oxygen is changing.
Through lab studies, we’ll try and figure out how certain species are reacting as a
function of oxygen.
On the international stage, Canada has been, and remains, one of the leaders in the research
on low oxygen areas, and we’re expecting that this will continue.