Warming weather could mean more anoxic events in P.E.I. waterways, biologist says

Unless you're standing at the very edge of P.E.I.'s Trout River, near Gunn's Bridge, seeing muchbelow the surface is probably out of the question.

The water looks like it's been mixed with a massive jug of milk. It smells funky too kind of like rotten eggs and little fish are swimming as close as they can to the top.

These are all strong indicators that this estuary is what's called anoxic.

"It is when there is low oxygen in the water," said Kyle Knysh, a surface water biologist with P.E.I.'s Department of Environment, Energy and Climate Action.

"When there's low oxygen, fish and invertebrates and mostly anything in the water that likes breathing oxygen doesn't do very well. So they avoid an area or, if they're trapped, [they] can die."

P.E.I. waters facing anoxic events, posing danger to marine life

2 months ago

Duration 1:35

The oxygen levels are low in some bodies of water on the Island, a phenomenon experts call an anoxic event. CBCs Sheehan Desjardins talked to Kyle Knysh, a service water biologist with the province, about how it happens, why it's dangerous to aquatic species and how to spot it.

The P.E.I. governmenthas been monitoring anoxic events like this for decades. For the past few years, numbers have fluctuated between 20 and28 cases annually.

There have been 10 so far in 2024. Knysh said that's on par with previous trends, but with temperatures reaching new heights on the Island, he expects to see an increase in the years to come.

"There's likely going to be more reports of this because of that," he said.

"It is concerning to aquatic life."

Knysh said lots of factors can cause an anoxic event. Oneis heat. Warm water is already at a disadvantage because it holds less oxygen to begin with.

Then, nutrients thrive in the heat, which attracts more organisms that breathe more oxygen anddeplete the water's supply.

"When it's warmer out we're going to be expecting that there is going to be less available oxygen," Knysh said."There is very, very little we can do."

'Adead zone'

But anoxic events can be short-lived. Depending on the conditions, Knysh said the situation can change quite rapidly.

"Within a day you can just have huge shifts.... going from, like, nearly no oxygen at night to really high oxygen during the day," he said."Many of these systems have low oxygen events every year. So there are organisms [that have] adapted to that, to an extent."

The province said two estuaries are monitored yearly, and 18 are checked about every three years.

The department also relies on reports from the public and encourages anyone who finds what could be an anoxic waterway to reach out.

"Eyes on the ground are important," said Knysh."It's really a dead zone for things that breathe oxygen."

Working with local farmers

Members of the P.E.I. Watershed Alliance also spenda lot oftime thinking about anoxic events.

The alliance is made up of 25 groupsrepresentinglocal watersheds across theprovince.

"We all do our best to work together to address these sorts of things," said Charlotte Large, a project manager with the alliance. "Because working in silos doesn't always get the best results, and so working together is often best for that."

The watershed groups also work withfarmers and the agriculture industry to findnew techniquesto prevent nutrient runoff into local watercourses.

That's important because when nutrients in the water increase, plant matter grows faster and that's bad news for aquatic organisms and fish.

"[Plants] take up [those]nutrients and essentially overgrow beyond the point where the estuary can reasonably sustain them, and they essentially take up too much space or too much oxygen," Large said.

"They also prevent sunlight from reaching further into the estuary, things like that. So too many plants are indeed a bad thing in the case of our estuaries."

While keeping up with the effects of climate change is a difficult race against time, Large said education and outreach by watershed groups has likely prevented even more anoxic events from happening.

"Progress doesn't necessarily mean reversal, just because looking at climate change, things are going to progress," she said. "There are techniques and things that we can do that help adapt to that or mitigate it or slow certain things."