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Invasive Sea Urchins Eating Kelp Forest, Stunting Growth Of Edible Ones

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Guacamole topped with uni at Petty Cash Taqueria (Photo by Krista Simmons/LAist)
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Uni has undoubtedly become the object of food lovers' obsession as of late, which is kind of strange considering that the delicacy is actually the gonads of a prickly-looking sea urchin. The bright orange, tongue-ish looking seafood may come off as entirely too fishy for some. (We thought the same until we tried the live version at the Hollywood Farmers Market.) But at sushi restaurants and gourmet eateries, it's a hot ticket item.

Seafood restaurants like Fishing With Dynamite, Connie & Ted's, and the Water Grill are known for their ultra-fresh, live Santa Barbara urchin. A restaurant called Maruhide Uni Club in Torrance has based their entire business on the cultlike following of the seafood. Heck, they even add it dollops of uni to a bowl of guacamole at Petty Cash Taqueria, turning a pedestrian Super Bowl snack into a truly decadent treat. What might come as a surprise to diners, though, is that the population of uni off the coast of Palos Verdes is in danger.

Oddly enough, this is because another type of urchin, an non-edible purple species, is proliferating. They're gobbling up all the nutrients underwater and stunting the growth of the red, edible sea urchins, as well as the giant kelp forests that help keep the coastal ecosystem in balance.

Local conservation groups are trying to get things back in order. They're heading underwater and puncturing the exoskeletons of the urchins -- an estimated 4.8 million of them -- to reduce their density and give the giant kelp a place to latch on to.

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The L.A. Times explains:

A fast-growing alga, giant kelp is the backbone of a rich coastal ecosystem. Its translucent green blades, held afloat with gas-filled bladders, tower up from the seafloor to form canopies that provide shelter and nutrients for a diverse marine community. Yet over the last century, kelp declined steeply off the California coast as storm runoff, erosion and other shore-based pollution clouded the water and made it harder for sunlight to penetrate. As kelp struggled — and predators like sheephead, lobsters and sea otters declined — sea urchins moved in.

A similar problem is occurring off the coast of Australia's East Coast, where hoards of long-spine urchins have created what are called "urchin barrens." Explains ABC:
"The equivalent is that you take a bulldozer into a rainforest and razing it back to bare earth," says Professor Craig Johnson, marine scientist with University of Tasmania and one of the principal research scientists involved with ABC Science's Explore the Seafloor citizen science research project. "Primary production drops by about 100-fold, and the habitat changes massively with a crash in biodiversity and a crash in local fisheries production, so it's a very significant issue." Sea urchins are typically just one of the species living in a seaweed bed. They're herbivores that use their five massive teeth to scrape away at kelp and other types of seaweed.

Many scientists the overpopulation in both areas has a great deal to do with human factors. In Australia, the commercial fishing of rock lobsters, the natural predators of sea urchins, plays a big part. And here in California, researchers believe it has to do with a temperature and nutrient fluctuation in the water.

Conservationist divers in Palos Verdes aren't the only ones getting involved. Commercial divers based out of San Pedro are also pitching in in hopes that they're clearing the way for more viable harvesting grounds. But if the ecosystem as a whole doesn't get sorted out, their efforts could be fruitless.

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Perhaps some day we might be able to have more local uni coming from Palos Verdes instead of up in Santa Barbara. Not that we don't love their sweet, creamy sea urchin, but the closer the better. Especially if it means restoring the order of our oceans.