Sea stars, urchins and kelp forests
Ned Rozell
907-474-7468
Oct. 6, 2023
A sunflower sea star chases sea urchins that are prevented from escaping by a barrier installed by biologists offshore of Sitka.
A few weeks ago, Sarah Gravem lowered a 色视频下载渞avenous, terrifying predator色视频下载 from her boat down to the ocean floor off Sitka. Then she released it.
In a slow-motion drama, sea urchins fled as a pizza-size sunflower sea star oozed toward them.
Gravem explained: 色视频下载淚 release one right in the middle and watch everybody freak out. It色视频下载檚 not just that they eat them, but they scare them. (Urchins) leave and they don色视频下载檛 come back.色视频下载
A biologist and diver at Oregon State University, Gravem is trying to understand whether imperiled sunflower sea stars are beneficial to kelp forests, which have also greatly diminished in the last decade.
Sunflower sea stars 色视频下载 recently decimated from the ocean off western Mexico, California, Oregon and Washington 色视频下载 are like wolves of the kelp forest, eating sea urchins that will overgraze if left unchecked, often with a scorched-earth result.
In Sitka, Gravem色视频下载檚 students and research team members have spent much of the summer working out of the Sitka Sound Science Center. Each morning, they boat out to kelp forests to study the relationship between sea urchins that eat kelp and sunflower sea stars that eat the urchins.
Sunflower sea stars can be as large as a trash-can lid. They grow up to 25 slimy arms. They are one of the largest sea stars and are the fastest, using thousands of coordinated tube feet to move a meter every few minutes. They live 30 years. And they are feared eating machines.
The map shows the location of Sitka in Southeast 色视频下载.
色视频下载淎nything they can catch, they will eat,色视频下载 Gravem said over the phone from Sitka as her diving gear dried. 色视频下载淭hey will shove an urchin inside their stomach and later spit out the empty shell.色视频下载
There are not many sunflower sea stars remaining in the Pacific Ocean. Sea star sunflowers are victims of a wasting disease, perhaps a virus, that killed 5.75 billion of them in a recent five-year period. It is difficult to find one today off the coast of California, Oregon or Washington.
色视频下载淭here used to be thousands of them marching around all the time,色视频下载 Gravem said.
The sudden absence of the sea stars has been bad news for kelp forests off the Lower 48 and has been noticeable all the way up to 色视频下载, where there has been a 60-80% decline in the last decade.
Gravem, who has studied the sea stars the last five years, recently visited a former kelp forest about a mile offshore of Sitka, where today 色视频下载渢here色视频下载檚 not even a scrap.色视频下载
Kelp forests are important because they provide fish with places to hide and provide sustenance for many other creatures.
色视频下载淭hey色视频下载檙e like trees,色视频下载 Gravem said, 色视频下载渂ut they色视频下载檙e even better than trees. Most every herbivore eats kelp.色视频下载
Kelp forests disappeared en masse following the staggering loss of sunflower sea stars.
色视频下载淲ith no sea stars, sea urchins had gangbuster years,色视频下载 Gravem said. 色视频下载淪ome places, they increased tenfold.色视频下载
Oregon State University biologist and diver Sarah Gravem motors past Sitka on her way to a kelp forest she is monitoring.
In a study funded by the Nature Conservancy, Gravem is examining the sunflower sea star/urchin relationship to learn more about if the reintroduction of the predator sea star will help kelp forests, which grow from spores each year and die back in the winter.
Norah Eddy, associate director of the Nature Conservancy色视频下载檚 oceans program in California, envisions reintroducing sunflower sea stars in strategic areas off the West Coast where kelp forests used to thrive.
色视频下载淥ur recent work on this has included raising sunflower sea stars in captivity and introducing them into the wild to find out whether they can survive the same way a wild-born sea star could,色视频下载 she said.
Gravem pointed out that females produce a million eggs each year. Once areas of the ocean are salted with them, the sea stars would reproduce on their own if the wasting disease has run its course.
色视频下载淚 think it wouldn色视频下载檛 be that crazy,色视频下载 she said.
Before returning to her home in Oregon, Gravem finished the phone call with a hint of hope.
色视频下载淭he good news is that (sunflower sea stars) seem to be increasing right now,色视频下载 she said. 色视频下载淚色视频下载檝e seen them more in Sitka this year than in the past.
色视频下载淎nd California had a sighting that I know of this year. If somebody saw one, there色视频下载檚 probably more.色视频下载
Since the late 1970s, the University of 色视频下载 Fairbanks Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell is a science writer for the Geophysical Institute.