Climate change

Low Oxygen Levels Along the Pacific Northwest a ‘Silent’ Climate Change Crisis


SEATTLE – Almost two decades ago, fishermen discovered a strange event off the coast of Oregon. They were collecting pots of dead or lethargic crabs.

At first they suspected a chemical spill or a red tide. But instead, they learned dangerously low levels of dissolved oxygen in ocean water were to blame.

The crabs had choked.

These bands of hypoxic areas have surfaced every summer on the coasts of the Pacific Northwest since they were first recorded in 2002. They are stimulated by natural coastal upwelling and algal blooms. , exacerbated by climate change, said Francis Chan, director of the Cooperative Institute for Marine Resources. Studied at Oregon State University.

Similar to fire season, hypoxia season arrived earlier this year – the earliest start in 20 years, according to Chan. But unlike forest fires or other visible climate emergencies, it is largely unrecognized.

“It’s kind of a silent problem going on over there,” Chan said. “This year, I can look outside and see trees with a burnt side from the heatwave. As I drive the McKenzie Highway I can see Mount Jefferson has no snow on it. But when you drive towards the ocean, it looks exactly like last summer. “

The coasts of Washington and Oregon are part of the large California Current marine ecosystem that stretches from Mexico to Canada. The ecosystem is very dynamic because every spring and summer the northerly wind systems blow south and push the upper layer of the ocean out to sea. It is replaced by water from deeper depths which is rich in nutrients and helps fuel the productivity of the West Coast. This process is known as coastal upwelling.

Rise water has lower dissolved oxygen levels because deep water has spent so long isolated from the atmosphere. The nutrient richness encourages strong blooms of phytoplankton, also known as marine algae, which eventually decompose – a process that consumes more oxygen from the water – leaving coastal waters with high levels of oxygen. even lower which can result in suffocation of sea creatures.

“How long can you hold your breath?” Asked Jenny Waddell, research coordinator at the Olympic Coast National Marine Sanctuary. “Aside from the marine mammals that breathe on the surface, just about everything else in the ocean uses dissolved oxygen for its life. “

Typically, hypoxic conditions did not arrive on the shoreline until mid-June or July. This year, hypoxic conditions were reported in April, with the upwelling season starting in March. To understand why an early start to the upwelling season is concerning, Chan compared it to the summer drought season. “Let’s say we expected rainfall until March, but the rain stops in February. That’s all the water we have. We have to hold out until next year.

Likewise, if the upwelling begins a month earlier than usual, the quantity of oxygen, already low, must last until the fall when thunderstorms favor the mixture which adds oxygen to the system.

Chan said that at the end of September this year, upwelling was still happening and low oxygen levels persisted.

Climate change plays a role in worsening oxygen levels. Simply put, warmer water contains less oxygen because oxygen molecules move faster and are more likely to escape from the surface. A little more complicated, climate change is altering the structure of the oceans, as the warmer top layer is more buoyant than the cooler, deeper and already oxygen-poor ocean layer. The warmer top layer prevents the deeper layer from “breathing,” Chan explained.

Globally, the oceans are already losing oxygen. Take this and add in local factors like coastal upwelling and the decomposition of phytoplankton blooms off the coasts of Washington and Oregon, and you have a system with extremely low oxygen levels.

While upwelling ecosystems like the CCLME were once considered resilient to climate change due to their dynamic nature, they have quickly and quietly become places that scientists say will be hit hard by changing conditions.

Scientists are busy monitoring the problem and collecting as much data as possible. But the death of sea creatures has alarmed not only scientists, but also coastal tribes, whose livelihoods depend on the ocean.

There is no record of recurring low oxygen levels as scientists have observed since 2002, despite more than 50 years of ocean monitoring. Joe Schumacker, a marine resources scientist from the Quinault Indian Nation, said there was nothing in Quinault traditional knowledge about large-scale marine mortalities that would suggest oxygen levels were as low as we can see it today. In 2017, the hypoxic event was so severe that Schumacker remembers the shores regularly lined with dead fish and crustaceans that summer. The International Pacific Halibut Commission also found that there was no or very little catch of Pacific halibut during this hypoxic event.

The marine sanctuary, where Waddell works, has been collecting ocean data through anchorages for 22 years. Moorings are like buoys with special instruments that collect data such as temperature, salinity, water direction, chlorophyll and oxygen levels off the coast of the Olympic Peninsula.

Anchorage data is one of the longest records scientists have in this region of the world documenting many oceanic features. This dataset is one of many models used to verify two regional forecast models, J-SCOPE and LiveOcean, for the coastal waters of Washington and Oregon that Samantha Siedlecki, a former researcher at the University of Washington and currently a professor at the University of Connecticut, played a central role. in development. Forecasts predict important ocean characteristics such as the timing of upwelling to the amount of dissolved oxygen in the ocean.

Waddell and Schumacker both said they saw forecasts predict an early rise and low oxygen levels this summer.

“When I think about hypoxia, it makes me really, really worried to be frank because it’s something we’re still not sure about all the dynamics that go with it,” Waddell said. “We are trying to figure this out.”

She said she saw coastal treaty tribes like the Quinaults on the front lines of climate change. “There is no part of the marine sanctuary that is outside of the tribal fishing areas protected by treaty,” Waddell explained.

Schumacker said Indigenous ocean fishing rights in Washington do not exist anywhere else in the United States.

“These treaty rights to harvest 50% of the exploitable fish and shellfish are legally defined in these certain boxes here,” Schumacker explained, referring to the boundaries of the tribal fishing area. “So it’s not like they can go somewhere else to fish. If things go wrong, they are immediately limited by this box which defines where the treaty exists. “

The people of Quinault, he said, take seriously not only understanding the impacts of climate change, but also adapting.

To illustrate the direct link between the health of the ocean and the tribe’s livelihoods, the Quinaults organize a summer clam dig each year to harvest clams for sale. The clam dig is also called the “school clothes dig” because families usually buy clothes and school supplies for their children with the money earned from collecting the clams.

“They are fishermen. All of the tribes here in the Pacific Northwest are fishermen. They have to keep fishing, ”said Schumacker.

Waddell said she was encouraged by the number of concerned young people and undergraduates who have reached out to investigate the matter.

“I don’t want to be negative or depressing. But yes, it will take all of us to make an effort to solve this problem in a meaningful way, ”she said.


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