The purple sea urchin is a shellfish about the size of a plum, and these tiny animals are causing massive problems.
Purple urchins live in the waters along the Pacific Coast, from British Columbia all the way down to Mexico. Recently, rising ocean temperatures led to a population boom off the coast of Northern California. According to the New York Times, the population of purple urchins is now 60 times bigger than it was.
The purple urchins have decimated California's kelp forests — 93 percent is gone. The kelp forests are critical to maintaining healthy marine ecosystems, because they absorb carbon dioxide, provide a habitat for many animals and also provide food. To make matters worse, kelp prefer cooler temperatures, so they're suffering from both the urchins and the heat.
Purple urchins are "the cockroaches of the ocean."
Sonke Mastrup, a program manager at the California Department of Fish and Wildlife, called purple urchins "the cockroaches of the ocean" because "they can endure starvation conditions much longer than most of the other critters." So even though 93 percent of the kelp is gone, the urchins won't necessarily start dying off.
Purple urchins also eat more than kelp. They chow down on many different kinds of algae (kelp are just one kind of algae). Scientists were surprised to find that the urchins even ate pink algae that had attached to rocks and formed a hard crust.
To save the kelp, civilians are organizing urchin dives.
Josh Russo, a recreational fishing advocate, has raised over $120,000 to organize dives where the goal is to clear purple urchins out of a habitat so that kelp can regrow. The events have been attended by recreational boaters, divers and commercial fishermen.
Commercial red urchin fishermen have an interest in eliminating purple urchins, because the purples are currently out-competing the reds, forcing many to starve.
Simply pulling the purple urchins out is not a long-term solution. In order for the kelp forests to thrive again, ocean temperatures have to come down. Figuring out how to make that happen is the true challenge.