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EDITORIAL: Troubled waters ahead

Eric Oliver, assistant professor of physical oceanography at Dalhousie University, says as climate warms there will be more marine heat waves like what was experienced in 2012 when Maine lobsters were caught in record numbers three weeks earlier than normal causing a market glut and a price drop to $2 a pound.
Contributed

Dip into the future of one of the Atlantic provinces’ greatest renewable resources — the fishery — and it’s easy to get alarmed about the number of threats.

Overfishing is a regular concern: whether it’s disputes over the necessity for quota reductions, or weaknesses in the amount of consistent scientific work being done, setting the right level for catches is always fraught with risks. Then, there’s the problem of underreported or illegal catches, the unquantified damage done by lost or abandoned “ghost” nets that continue killing fish.

Then, there’s the question of protecting already-endangered species: changes in the crab fishery in the Gulf of St. Lawrence to protect right whales is one wrinkle, as are questions about adding formerly critical commercial fish populations to protections under species-at-risk legislation.

There are questions about the effects of oil exploration seismic testing on plankton and fish species, and about the long-term effects of microplastic fragments, particularly on filter-feeding shellfish.

On top of the direct fisheries concerns are larger climate issues: warmer waters are causing species to move north to colder waters, changing the composition of fish stocks and changing the predator-prey relationship. Species that can’t move fast enough are simply vanishing from their former ranges.

Oceanographers are seeing changes in oceans currents as the climate warms, changes that play out in unexpected ways, both in water temperature and salinity, as melting arctic ice adds considerably more fresh water to some parts of the ocean.

The oceans are so large that they sometimes appear more forgiving than they are: their size just means that cumulative impacts are slow in developing.

And then there’s the looming threat of ocean acidification; as carbon dioxide levels rise, that CO2 is expected to go into solution, raising the ocean’s acidity and making it harder for calcium carbonate based plankton to survive — there are also risks for a variety of shellfish, particular at early and larval stages in their development.

So there are threats enough already — yet there’s scarcely time to breathe before a new concern comes along.

And breathing’s important.

Turns out, breathing may be at risk, too.

Scientists are warning that the amount of oxygen in the ocean is falling as the seas warm and are less able to retain dissolved gases. And just as “fish gotta swim,” as singer Billie Holiday famously pointed out, fish gotta breathe, too.

In some tropical areas, oxygen levels have dropped by more than 40 per cent in the last 50 years, according to scientists at the Helmholtz Center for Ocean Research Kiel. Scientist Andreas Ochlies told the journal Scientific American, “We were surprised by the intensity of the changes we saw, how rapidly oxygen is going down in the ocean and how large the effects on marine ecosystems are.”

The oceans are so large that they sometimes appear more forgiving than they are: their size just means that cumulative impacts are slow in developing.

That sheer size means that they are equally slow, however, in returning to more normal conditions.

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