Alaska has plenty of marine predators, including orcas, Steller sea lions and salmon sharks. In the last few years, researchers have discovered a predator that is not well-known which could play an important part in keeping Alaska’s kelp forests in good health.
A third-year student in the fourth year of graduate school Nikita Sridhar digs deep into a tank within the basement laboratory in the Sitka Sound Science Center in search for the “underappreciated prey.” These animals are extremely effective hunters that when they come into an area, you can hear the screams of underwater,” Sridhar says. “Everyone’s trying to get out of the area.”
Sridhar wrestles the sea creature out from the tank, and then holds it in front of the light source — an enormous dinner-plate-sized purple sea urchin.
Sunflower stars are the main focus of Sridhar’s study this summer as she works with Professor Kristy Kroeker from the University of California, Santa Cruz. Sridhar plans to build upon her her previous work to understand how sunflower stars can be used to keep the coastal kelp forests safe.
Sea stars might not frighten us but to a gang of sea urchins, they’re terrifying predator.
“They typically throw their stomachs in the air, raise their arms and then a portion of their stomach from their underneath is thrown out,” Sridhar said. “And then they consume the stomach.”
The sea star on her hands is a recent sign of these grisly incidents -the stomach extends out of its body and a shard of urchin’s spines that have been crushed are its arms.
While it’s unfortunate for the urchin, this type of predation can be beneficial to the ecosystem. Urchins consume kelp and the presence of too many urchins may ruin kelp forests, which trap carbon that helps to mitigate the impact of climate change. They also offer shelter to numerous creatures.
“They’re like skyscrapers, which provide shelters for all the different species of animals,” Sridhar said.
To keep kelp forests healthy, it is necessary to maintain the balance of ‘grazers’ that eat kelp such as urchins and abalones, and predators like sea stars, which consume grasshoppers.
“If you are unable to complete one piece of this puzzle, for example, you’re losing one of the predators that is important, then there could be excessive grazers” Sridhar stated.
It’s been done before: a decrease in the number of sea orcas which is a well-known predator of urchins, as well as other kelp-eating creatures that led to the emergence the development of ” urchin barrens” across the Pacific coast in which urchins cut through entire kelp forests.
Researchers are currently trying to determine whether, and in what way, other predators like sunflower stars can be a part of protecting the forests of kelp.
Sunflower stars are a source of food for urchins but Sridhar is of the opinion that they can also impact the behavior of urchins in different ways. As part of her research this summer, she’s trying to determine whether the mere presence of sea stars can trigger that urchins eat less kelp.
“Just being aware of this predator could result in the urchins becoming terrified to eat less than kelp” Sridhar told the AP. “They could be putting their energy in running away from the predator, or getting into tiny crevices instead of merely wandering around the ocean floor and eating kelp whenever they like.”
In one of her experiments Sridhar places the sunflower star, which is caged, in the middle of a tank stuffed with urchins. She would like to determine how far the urchins go towards the cage or consume less kelp, if they are aware that the sea star is near. Outside in Sitka Sound, her team is conducting similar research following the course that a sunflower star follows, and studying the length of time they take for the sea urchins as well as abalones to return to their respective areas or “whether the slime trail left by the sea star is so large that they’re afraid to return, basically.”
If sunflower stars function as guardians for kelps this is a great good news for the forests of kelp in particular when the population of sea stars increases. Sea star disease has ravaged all of West Coast over the past decade, causing massive dissolution of vast swaths of sea star. Sunflower stars were particularly hit severely by the disease.
Sridhar reported that they’ve seen more mature sunflowers around Sitka Sound this summer than they had expected. At least, it’s at first, a reason to celebrate.
“It’s amazing that we’re seeing them this season and we hope that they will be around for a long the season,” Sridhar said. “We’ll see.”
Sridhar isn’t able to report results as of yet, but she’s keen to discover how the sunflower stars can aid in protecting the kelp forests making what she describes as”a “landscape of terror” for the populations of urchins.
