My least favorite sushi
By Will Collette
Two unrelated articles that appeared the same week caught my eye. One was a URI piece on research to try to figure out a good way to raise sea urchins through aquaculture. The second was a report on Israeli research on the global die-off of sea urchins and its disruption of the marine ecology.
Although sea urchin (Uni) are the only variety of sushi I've encountered and really hated, I wondered what was the fuss. As the articles detail, sea urchins aren't just a food source, but a valuable part of ocean environment.
I begin with first with the URI story below, followed by the report from Tel Aviv University.
URI aquaculture professor and scientists worldwide look for solutions
By Hugh Markey.
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| Green sea urchin brood stock at the University of Maine’s Center for Cooperative Aquaculture Research. (Photo courtesy of Coleen Suckling) |
The eggs are commonly called uni, and Coleen Suckling, a
marine eco-physiologist and associate professor of aquaculture and fisheries at
the University of Rhode Island, is convinced that raising these animals and
harvesting the uni is part of a viable industry.
“If you think about what a clean ocean smells like, and translate that to taste, you’ll have an idea of what they taste like,” Suckling said.
In a recent Coastal State Discussion on Sea Urchin Farming in New England, Suckling and Dana Morse of Maine Sea Grant/University of Maine discussed the latest research and initiatives to advance sea urchin aquaculture in New England–specifically purple and green sea urchin species. During the discussion, Suckling dared the audience to taste the uni, which is normally in season from October/November until March/April. Suckling said their use can extend beyond sushi to create sources for pasta dishes or new dining experiences such as serving it on a seaweed bed. “These are lovely, beautiful animals, and Grade A uni from them can fetch $40 to $50 per 3 to 4 ounce tray,” she said.
Green sea urchins (Strongylocentrotus
droebachiensis) are the only commercially viable species of sea
urchin in New England. Most often found grazing along the seabed preferring
temperatures of around 53 to 59 F, the animals have a cluster of five teeth on
the bottom side that scrape their food as they wander along. They are sometimes
regarded as a nuisance species when their populations expand and the creatures
begin grazing on valuable kelp ecosystems, a problem which has arisen on the
West Coast.
Suckling says there are many projects related to urchin
farming taking place both on and off the URI campus, including optimizing
hatchery production. Suckling partnered with the region’s only urchin hatchery
in Maine, hosted by the University of Maine’s Center for Cooperative
Aquaculture Research, where Steve Eddy is the director. 
Large green urchin seed being deployed at a farm.
(photo: Coleen Suckling)
Together they have been working to find the right conditions for producing juveniles, called seed, which can be provided to coastal farmers for growth for the market.
The two institutions
received funding from the Northeast Regional Aquaculture Center to enhance
settlement success and post-settlement survival to optimize how they produce
these seed.
“It’s a nice partnership because this is where universities
are ready to offer tools such as space for the research,” said Suckling. “With
these tools available, we can investigate many different avenues, and let
industry know what worked best.”
Most of the fisheries on the East Coast are in Maine, although the urchin population has been declining despite management efforts. Suckling says sea urchins have long been considered a pest that would interfere with lobster traps.
Traps would need cleaning several times a season because
they would be clogged with animals like sea squirts (a translucent animal
resembling a blister; they cluster together and choke off the water circulation
in the farming baskets). Because of this assumption, efforts were directed
to simply harvest the animals first, with management coming later.
Experiments indicate that pests that often clog nets and
baskets reduce the productivity of desirable fisheries like scallops.
However, when sea urchins are introduced, they naturally clean out the
biofouling, leaving space for more shellfish production and reducing the need
for the equipment to undergo time consuming cleanings.
Suckling has been devoting some of her time to creating
awareness about this industry. Since the overharvesting years of the 1980s, a
new generation has begun working in various aquaculture fields and may not be
aware of the potential of urchin farming.
Aquaculture farmers have been given both free seed from
urchins raised in a hatchery, as well as free consulting expertise, to
encourage new interest in raising urchins. This type of help encourages growers
to see whether adding urchin farming to their businesses is something they’d be
interested in.
“What’s most exciting is the possibility of using urchins as
a tool to help with biofouling issues that we see aquaculture faces,” Suckling
said. “Biological fouling, which accumulates on all surfaces in the ocean and
aquaculture gear, is routinely removed by farmers to maintain optimal water
flow and ensure an adequate supply of planktonic food for their shellfish.
Integrating sea urchins with shellfish farming introduces a natural solution,
as the urchins can graze on this. This approach has the potential to reduce the
labor and effort required by growers to maintain their oyster farms.”
“We have had some good success so far. I was just talking to
the permitting agency in Maine, and they said they were seeing more and more
people adding sea urchins into their applications just in case they decide to
engage in sea urchin production. People are talking about it, people are
interested, which is really motivating,” Suckling said.
Another research project includes one of Suckling’s graduate
students who is researching “stress priming,” a relatively new process of
exposing an urchin to some sort of controlled stress such as lower temperature
or PH levels, in order to solicit a kind of memory for the animal to cope with
more stressful events later in life.
“We’ve also had several decades of climate change,” Suckling
said. “The Gulf of Maine is normally a subarctic system but it’s getting very,
very warm. It’s one of the five fastest warming regions in the world.”
“My only goal is to see how I can help build resilience for
the industry moving forward. I talk with industry representatives a lot to
understand some of the needs, where the gaps are, and to understand what may be
feasible.
“I hope to help the industry build their resilience, maintaining livelihoods, and produce seafoods that keep people healthy, and that people can get access to without a high environmental cost.”
“An Extremely Violent Global Pandemic” – Mysterious
Disease Wipes Out Sea Urchins Worldwide
By Tel-Aviv University
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| Sea urchin mortalities on Reunion Island. Credit: Jean-Pascal Quod |
This discovery raises concerns that the waterborne ciliate
could spread to the Pacific Ocean. Researchers warn that the outbreak is a
highly aggressive global pandemic and are leading an international initiative
to monitor the disease and protect sea urchins, which are essential for
maintaining healthy coral reef ecosystems.
The study, led by Dr. Omri Bronstein from the School of
Zoology at Tel Aviv University’s Wise Faculty of Life Sciences and the
Steinhardt Museum of Natural History, was published in the prestigious
journal Ecology.
“This is a first-rate ecological disaster,” explains Dr.
Bronstein. “Sea urchins are vital to the health of coral reefs. They act as the
‘gardeners’ of the reef by feeding on algae, preventing it from overgrowing and
suffocating the coral, which competes with algae for sunlight. In 1983, a
mysterious disease wiped out most of the Diadema sea urchins
in the Caribbean. Unchecked, the algae there proliferated, blocking sunlight
from the coral, and the region shifted from a coral reef ecosystem to an
algae-dominated one. Even 40 years later, the sea urchin population — and
consequently the reef — has not recovered.”
A Recurring Threat: Caribbean and Red Sea Outbreaks
In 2022, the disease reemerged in the Caribbean, targeting
the surviving sea urchin populations and individuals. This time, armed with
advanced scientific and technological tools to collect and interpret the
forensic evidence, researchers at Cornell University successfully identified
the pathogen as a ciliate Scuticociliate parasite.
A year later, in early 2023, Dr. Bronstein was the first to
identify mass mortality events among long-spined sea urchins, a close relative
of the Caribbean Sea urchins, in the Red Sea.
“Until recently, this was one of the most common sea urchins
in Eilat’s coral reefs — the familiar black urchins with long spines,” says Dr.
Bronstein. “Today, this species no longer exists in significant
numbers in the Red Sea. The event was extremely violent: within less than 48
hours, a healthy population of sea urchins turned into crumbling skeletons. In
some locations in Eilat and the Sinai, mortality rates reached 100 percent. In
follow-up research, we demonstrated that the Caribbean pathogen was the same
one affecting populations in the Red Sea.”
Now, using genetic tools, Dr. Bronstein and his
international colleagues have shown that the same ciliate parasite is
responsible for similar mortality events off the coast of Réunion Island in the
Indian Ocean.
“This is the first genetic confirmation that the same
pathogen is present in all these locations,” he says. “Now it’s a global event,
a pandemic. The Caribbean, Red Sea, and the Indian Ocean are critical regions
for the world’s coral reefs, and mortality rates for sea urchins in these areas
are very high — over 90 percent. As of now, we have no evidence of this
pathogen in Pacific Ocean sea urchins, but this is something we are actively
investigating. Although we’ve developed genetic tools for the specific identification
of the pathogen, it’s difficult to monitor such rapid extinction events in the
vast underwater environment. We are terrestrial creatures, and some reefs are
located in deep or remote areas. If we miss the mortality event by even a
couple of days, we might find no trace of the extinct population.”
Tracking the Pandemic’s Spread
To track the progression of the pandemic, Dr. Bronstein has
established an international network of collaborators. He provides them with
alerts about the likelihood of mortality events in their regions and sends them
the necessary equipment to sample and preserve affected sea urchins for
comparison with samples from other locations. These kits are then sent back to
the laboratory at Tel Aviv University.
“For populations that are already infected, we really have
no tools to help them,” says Dr. Bronstein with regret. “There is no Pfizer or
Moderna for sea urchins — not because we don’t want one, but because we simply
can’t treat them underwater. Our focus must be on two entirely different
tracks. The first is prevention. To prevent further spread of the pandemic, we
need to understand why it erupted here and now. We’ve developed two hypotheses
for this. The first is the transportation hypothesis — that the pathogen from
the Caribbean was transported by humans to new and distant regions after being
carried in the ballast water of ships, infecting sea urchins in the Red Sea
before spreading to the Western Indian Ocean. Incidentally, if this hypothesis
is correct, we would expect to see mortality events in West Africa as well — as
many cargo ships from the Caribbean stop there on their way to the
Mediterranean and then through the Suez Canal to the Red Sea.”
He continues, “Indeed, just in the past few weeks, we’ve
discovered widespread mortality events in West Africa, as we predicted, and
we’ve managed to obtain a limited number of samples collected during these
events, which we are currently analyzing in the lab. If ships are indeed the
source of the spread, then we could think of mitigation strategies. It’s not
simple, and ships will never be completely sterile, but there are measures we
can take. The second possibility is even more concerning: that the pathogen has
always been present, and climatic changes have triggered its virulence and
outbreak. That’s a challenge of an entirely different magnitude, one that we,
as marine biologists, have very limited means to address.”
In parallel with global efforts, Dr. Bronstein has recently
established a breeding nucleus for the affected sea urchins at the Israel
Aquarium in Jerusalem, in collaboration with the Biblical Zoo and the Israel
Nature and Parks Authority. This breeding population will serve as a reserve to
restore affected populations and advance research into infection mechanisms and
possible treatments.
“The pathogen is transmitted through water, so even sea
urchins raised for research purposes in aquariums at the Interuniversity
Institute for Marine Sciences and the Underwater Observatory in Eilat became
infected and died. That is why we established a breeding nucleus with the
Israel Aquarium, whose aquariums are completely disconnected from seawater. We
genetically test the urchins transferred to the nucleus to ensure they are not
carriers of the disease and that they genetically belong to the Red Sea population,
enabling us to rehabilitate the population in the future. At the same time, we
are using them to develop sensitive genetic tools for early disease detection
from seawater samples — essentially creating ‘underwater COVID tests’ for sea
urchins.”
Reference: “Spread of a sea urchin disease to the Indian
Ocean causes widespread mortalities—Evidence from Réunion Island” by
Jean-Pascal Quod, Mathieu Séré, Ian Hewson, Lachan Roth and Omri Bronstein, 20
November 2024, Ecology.
DOI:
10.1002/ecy.4476
