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ALBION, CALIFORNIA Early on a cloudy summer Saturday, an unusual group – commercial fishermen, recreational boaters and scuba divers – gathered at the cove of Albion Cove to accomplish a mission: drive for three hours north of San Francisco.
“Our goal today is the purple sea urchin,” said Josh Russo, sports fishing advocate and organizer of the event. “The evil purple hedgehog.”
Five years ago, describing the sea urchin as a villain, a mollusk that looks like a plum with spikes of 6.3 millimetres, would have been ridiculous.
That was before it wiped out the kelp forests of California.
In many ways, underwater forests-huge mazes growing in brown algae, or kelp-have the same importance for the oceans as trees do for the land. Like trees, they absorb carbon emissions and provide the habitat and food essential for a wide variety of species. However, when climate change helped trigger the population size of sea urchins on the coast of northern California to multiply by 60, these creatures rampaged in a feeding frenzy and devoured seaweed.
“It would be as if one of those beautiful deciduous forests became a desert,” said Gretchen Hofmann, professor of marine ecology at the University of California, Santa Barbara campus. “But in a matter of five years.”
The risks spread beyond this bay: there are kelp forests on the coasts of coldest water on all continents, except Antarctica. In addition, they are under threat from rising ocean temperatures and from what they bring with them warmer waters.
The forests of Maine sugar kelp, a source of mannitol sweetener, have already experienced declines related to temperatures. In Tasmania, kelp forests have perished in the presence of an outbreak of purple urchins. Here in Albion, we try to avoid the same thing happening.
WITHOUT THE CHELPOS, MANY MEANS OF SUBSISTENCE WILL BE LOST
The divers went to work, pulling out the purple urchins from the bottom of the inlet, hoping that this would allow the brown seaweed to grow back, having declined by 93 percent in northern California.
Cynthia Catton, an environmental scientist at the California Department of Fish and Wildlife, and a small group of interns were sitting on a boat counting the hedgehogs that divers brought to the surface to get an idea of how they were doing.
The history of the disappearance of the kelp is also that of an interwoven food system on the verge of collapse that is threatening the livelihood of people. Among the first to sound the alarm about purple urchins, said Catton, were the commercial fishermen of red sea urchins.
One of them is Gary Trumper, who has collected red hedgehogs for more than 30 years. You can trade with these hedgehogs, which are bigger than purples because people eat them (they eat their genital glands, to be more specific). This delicacy is best known among sushi fans as “uni”.
However, the growing population of purple urchins outnumbered that of the reds in their competition for available brown algae. Without the kelp, the red hedgehogs died of hunger.
That reduced the commercial fishing value of the red sea urchin in Northern California from $ 3.6 million in 2013 to less than $ 600,000 in 2016. Many collectors have switched to other businesses. “It’s probably ten or fifteen who keep doing that at the port,” said Trumper, sitting in a bar near Fort Bragg, where his boat docks. “But there used to be about a hundred.”
The problem started with the starfish. The sunflower star, whose appendix can expand more than 90 centimetres, normally feeds on purple urchins, which helps limit their populations.
However, in 2013, starfish began to die mysteriously. There is no scientific consensus on the reason behind this event, but Drew Harvell, professor of Ecology and Evolutionary Biology at Cornell University, said she believed that the culprit, at least partially, had been a virus and that the warmer waters exacerbated their effects.
Sea otters, another predator of purple urchins, were hunted to the brink of extinction by fur traders in the 19th century. The density of its population has not yet recovered.
Around the same time that starfish began to disappear, a warm body of water appeared hundreds of thousands of kilometres from Alaska, British Columbia, Washington, and Oregon. By 2014, the hot water had moved toward the land, extending from southeast Alaska to Mexico.
This marine heat was the warmest one registered since the late 1800s. Researchers and locals called it “La Mancha”. It remained until 2016.
“The global warming caused by humans made this extreme situation possible,” said Nathan Mantua, a physical scientist of the National Oceanic and Atmospheric Administration and author of a study linking La Mancha to climate change. More than 90 percent of the heat trapped on the planet due to the greenhouse gases emitted by humans has been absorbed by the ocean, which has increased its temperature.
However, kelp prefers cooler waters. Giant seaweeds found in northern California release spores in the fall; during the winter, the spores grow to become alfalfa-like plants, which according to Hofmann look a bit like Baby Groot’s character in “Guardians of the Galaxy”.
“We do not know much about them because they are very mysterious,” admitted Hofmann. “But with what little we’ve researched about it, we know they do not like high temperatures.”
La Mancha also slowed down the upwelling process, in which colder waters and nutrients rise from the deepest areas of the ocean to the surface.
That eliminated a critical supply for kelp nutrition.
“It’s as if your garden will run out of fertilizer,” said Mantua.
“A hot ocean is generally not as productive,” said Sonke Mastrup, program manager in the California Department of Fish and Wildlife. “It cannot hold so much oxygen.”
With the combination of higher temperatures and fewer nutrients, the brown seaweed began to perish.
CHANGE OF BEHAVIORS
In the absence of predators and dwindling food supplies, purple hedgehogs have become rampant, said Mark Carr, a population ecologist at the University of California, Santa Barbara campus.
“They line up like a horde of demented individuals and move like a whirlwind all over the reef, literally tearing out all the algae,” he said. This year, they have eaten hard pink seaweed and embedded in the surface of rocks, something that scientists did not expect to see, said Laura Rogers-Bennett, marine ecologist who works in the Marine Laboratory of Bodega.
“The underwater impact this year has been more devastating than any we have seen in the past,” he said. “The perfect storm of events has worsened over time, and those of 2018 have been the worst we’ve seen.”
It is not likely that purple urchins will disappear.
“They are like marine cockroaches,” said Mastrup. “They can endure starvation conditions for much longer than most other creatures.”
Even the remaining red hedgehogs have begun to adapt. Although they are regularly vegetarians, at greater depths they are becoming carnivores and eating barnacles. “Which is a very crazy event,” said Catton.
In an attempt to recover the kelp, Russo has raised more than $ 120,000 in subsidies and donations from independent divers to organize selective elimination activities such as Albion Cove.
The goal, said Catton, is to create oases of kelp that can recover safely, away from the purple hedgehogs. The concern is that if too much time elapses there will be no more quelpo to plant future generations.
“There is a group of people who believe that it can change the trajectory of what is happening in nature,” Mastrup said. “I hope so, but I have my doubts about what can be achieved.”
Source: El Nuevo Herald