Urchins Here, Urchins There…Urchins Everywhere!
By Johnson Yu
Sea urchins have long been one of the ocean’s delicacies. Divers venture out into the water depths in search of these spikey creatures, selling their harvest for a hefty price. Within the culinary world, sea urchins (otherwise known as ‘uni’) are treated as a highly delectable and expensive treat for connoisseurs around the globe. Their rich, creamy texture leaves a savory taste as the ‘uni’ seemingly melts in your mouth. So how can something so delicious, leave such a bad taste in the ocean?
The Most Fine Along the Coastline
Organisms in the hierarchical food chain are normally kept in check by predators. For sea urchins, their natural predators are humans, eels, otters, starfish, and triggerfish on the vast ocean floor. When the balance between predator and prey becomes unstable, a myriad of consequences can arise. This is most evidently seen in California's coastal waters where mass populations of purple sea urchins have begun destroying the ecosystem’s natural order.
In 2014, the Pacific Ocean experienced a large mass of warming waters — “the Blob” — which wreaked havoc on Sunflower Sea Star populations. Not only did water temperatures experience an abnormal increase, but also were nutrient deficient and gave rise to a festering virus that affected the sea stars specifically. This shifted the overall dynamics between starfish (predator) and sea urchin (prey) where urchin populations became unregulated, allowing them to freely expand in numbers.
The question to be asked is why “the Blob” did not directly affect sea urchins as severely as it did starfish. Aside from the disease that spread through the Pacific coast, studies have shown inverse results of warmer temperatures on the two organisms. For the Sunflower Sea Star, temperature shifts had a more drastic effect where optimal water conditions were crucial to their survival. in cold waters, these predators became slower and unable to catch prey as efficiently. In warmer waters, their mortality rate increased as their vital organs failed to function properly which made them more susceptible to diseases. On the contrary, sea urchins seemed to thrive in warmer environments where embryotic cells divided at a faster rate than in cold waters. Essentially, warm waters allowed sea urchin embryos to develop quicker, leading to an influx in urchin population growth.
So what’s the Issue…?
Although the rise in purple sea urchin populations may seem like an overall win for the culinary world, restaurants only buy red urchins due to their larger diameter. In other words, purple sea urchins really have no predators to regulate their growth.
The issue at hand stems from the lack of predation on these purple sea urchins. Sea urchins feed on kelp forests, eating the roots of the plant; however, the allotment of the population boom has led to overgrazing and the destruction of kelp forests entirely. According to satellite images, approximately 95 percent of kelp forests along California’s coastline have been destroyed. This is due to kelp plants being hindered in their ability to spread spores across ocean floors. As soon as a plant disperses its spores, purple sea urchins are waiting to feast on the seeds before they can even cultivate into a full-grown stalk.
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The onslaught of kelp forests is of severe gravity where an entire ecosystem could potentially be lost forever. Kelp plants are crucial for marine life as they offer not only a source of food but also a natural habitat for smaller fish, provide nursery shelter for developing organisms, and protect shorelines from erosion by mitigating wave energy. Without the presence of these forests, negative consequences will not be limited to just marine life. Human civilizations along California’s coast could literally collapse as the shorelines erode away. Furthermore, the severity of the kelp forest food chain’s destruction could lead to a mass catastrophe in the grand marine food web. Already, organisms such as snails, abalone, and sea birds have experienced these consequences as there is not enough food and fish to prey on.
A Desperate Solution to a Precarious Predicament
The only viable methods of solving this issue are in the hands of humans. By taking initiative, there is promise in seeing a regrowth of kelp forests which gives hope for marine ecosystems to thrive again.
The first solution is to physically remove purple sea urchins off the sea bed. Commercial divers have already begun scooping up purple sea urchins in an attempt to mollify the outrageous population number. Teaming up with the Reef Check California organization, divers have been able to remove over 10 tons of purple sea urchins in the past year. With more Americans being aware of this issue, a mass collective attempt could help to restabilize the kelp ecosystem. With purple sea urchin numbers being mitigated, there is hope that floating kelp spores from nearby waters may seed a new forest.
Another option would be to reintroduce sea otters into purple sea urchin-infested waters. Sea otters are one of the urchin species’ natural predators. However, California's sea otter populations were extensively hunted for their fur in the 1800s. In modern-day, aquariums have habitated sea otter communities and aided them from going extinct. Introducing them back into natural waters where purple sea urchin communities flourish could potentially be promising for both species. Sea otters are able to predate on the urchins, allowing them to repopulate waters. Sea urchin communities now have a natural predator that keeps their growth in regulation. This is the most natural solution to solving the kelp forest loss problem.
Overall, a solution must be derived in order to see a regrowth of kelp forests and marine ecosystems that thrive in the environment. Purple sea urchins have become more than a threat to just these ecosystems and are now stemming a myriad of problematic issues. Regardless of which solution is taken, it cannot be denied that the spreading of awareness will be the most viable route in inciting change in a positive direction.
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