Dr. Sam Starko and collaborators performing intertidal biodiversity surveys in Barkley Sound, B.C., in 2021.Supplied
The summer that the ocean fell silent stays with Mike Reid.
“It looked like a dead zone. There were no birds, no seals, no otters. When you looked into the water column, there was no urchin, there was no [sea] cucumber, no fish swimming about.”
Mr. Reid, the aquatics manager for the Heiltsuk Integrated Resource Management Department in Bella Bella, B.C., was seeing the impact of an abnormally warm mass of water that clung to the Pacific coast from 2014 to 2016. Nicknamed “the Blob,” the unexpected episode would become the largest, longest, and most severe marine heat wave ever recorded.
This manifestation of global warming wreaked havoc on the marine ecosystems of British Columbia – closing fisheries, driving species from their homes, and providing a window into the oceans of a climate-changed future.
In research published earlier this summer, scientists released a complete look at the effects of the Blob on every part of the ocean, from the smallest plankton to humpback whales.
Beyond how the higher temperatures changed which species could survive where, the team of researchers at the University of Victoria found that some of the most significant impact came from the knock-on effects of the Blob rippling across the entire aquatic world. As the ocean continues to warm and the chatter of oil pipelines and fossil fuel investment returns to Ottawa, the systematic review shows a sobering picture of the future of life in a warmer ocean.
“By looking back on this event, we can have a sense as to what the future might look like as we see more and more of these events unfold in our oceans,” said Dr. Sam Starko, the lead author of the paper.
2019 Analysis: Return of the Blob, and other climate calamities
From 2023: Pacific Ocean temperatures, already warmer than usual, face looming El Niño
Pulling together more than 300 peer-reviewed articles and government reports, the team of researchers took a deep dive into the chaos of an ecosystem pushed to the edge.
Unlike gradual warming – the steady uptick in yearly ocean temperatures that climate change often brings to mind – marine heat waves are relatively short spikes of a few degrees Celsius, driven by global cycles such as El Niño years and oceanic currents. As climate change disrupts the usual atmospheric rhythms, these natural cycles are becoming less predictable and more intense.
In 2023, another round of heat waves struck around the world, setting global records for their extent and intensity, with 96 per cent of the world’s oceans affected. Yet, the Blob remains the largest and longest single marine heat wave ever, and increased temperatures by up to six degrees.
Most life in the ocean already lives close to the thermal limit, said Dr. Starko. At a few degrees beyond this threshold, life can survive for weeks or even months, but the duration of the Blob pushed far beyond this limit for many species.
“When we’re talking about being warmer than usual for say three years, as we saw with this event, that can have really, really big effects on things like survival,” he said.
These warmer temperatures also allowed species to expand their range, pushing some populations northwards, bringing dolphins, pygmy killer whales, and the giant tropical sunfish into B.C. waters.
Some species thrived in these new conditions. Populations of gelata – jellyfish-like organisms – exploded, as did those of anchovies and a toxic species of algae. These harmful algal blooms produced record levels of domoic acid, a neurotoxin, and were responsible for mass die-offs of marine mammals and seabirds off the coast of California.
These direct effects of warming on an organism’s life are notable enough, but because the ocean is so well connected, changes for one species often have cascading effects up and down the food chain.
A dead ocean sunfish in Bamfield, B.C., during the Blob, in 2016.Kristina Tietjen
Perhaps no ecosystem embodies this better than a kelp forest. A temperature increase of just three degrees can doom the towering seaweeds that make up these subaquatic woods, which normally thrive in the cool, steady temperatures of the Pacific.
The kelps themselves, however, were not the only organisms affected. The sea stars that live in the kelp forests also suffered, with their populations decimated by a recently discovered bacterium that spread faster in the warm water of the Blob.
With no predatory sea stars to keep their numbers under control, sea urchins grazed down entire forests, leaving behind what has become known as an “urchin barren,” an underwater moonscape blanketed with purple spines and not a seaweed to be seen.
This double whammy of high temperatures and out-of-control sea urchins led to unprecedented losses of kelp forests, many of which still have not returned since the Blob.
In every ecosystem studied, from the deep sea to tide pools, these large-scale, knock-on effects were found.
The open ocean, as another example, saw a complete reorganization of the food web. The high temperatures altered the way nutrients flow through the currents, leaving less food at the surface of the water.
The plankton that thrive in these new conditions are smaller and less nutritious, meaning that the fish that eat them miss out on the food they need to survive – the oceanic equivalent of having your healthy salmon dinner swapped for a handful of fishy crackers.
From 2023: B.C’s pink sea urchins are on the move to shallower waters thanks to climate change
As a result, many salmon that grew up in the Blob years were pressed to find enough food. When those fish were old enough to be caught, around 2019-2021, the B.C. coast saw some of the worst salmon fishing ever, leading to coastwide closings of commercial salmon fisheries in 2021.
For communities that rely on the coast for income and sustenance, these oceanic changes have a big impact. Mr. Reid, in Bella Bella, had one word to describe the impact of the Blob on his small fishing community: “Devastating.”
Beyond the fisheries’ closings that grounded many of the town’s fishing boats, Mr. Reid saw many of the effects discussed in the paper, and more. Foods that his community traditionally relies on, such as fish and seaweed, suddenly disappeared from the places they had been harvested for generations and have been slow to return.
While the Blob itself is now long gone, sea temperatures have not quite returned to normal. Temperatures in some areas remain higher than they used to be, and marine and atmospheric heat waves, such as the heat dome that smothered the Pacific Northwest in 2021, have continued to wreak havoc, causing droughts in rivers and elevating surface temperatures further.
“One of the things that we’re thinking about after the ocean Blob and the droughts that we were experiencing is that we actually need to think ahead further than that,” Mr. Reid said.
His organization is already working toward climate adaptation, establishing an “emergency salmon enhancement plan” to mobilize the transplant of salmon in the event of future heat waves that dry up the streams where they spawn.
These extreme weather events will only become more common as countries delay commitments to the Paris Accord, and the ideal 1.5-degree limit to global warming grows steadily out of reach.
“Climate change is happening now,” said Dr. Julia Baum, a professor of marine biology at the University of Victoria and the senior author of the paper.
“It’s already impacting all ocean life, which means it’s already impacting all coastal communities,” she added. “It really underscores that no organism, no species, no community can escape climate change.”
Special to The Globe and Mail