[Coral-List] Scientists Solve a Sea Urchin Murder Mystery!

Tue May 9 00:04:57 UTC 2023

good evening Douglas

I just read today this interesting and important article on the Smithsonian
Magazine. I am not sure if this topic has been already mentioned in your
Reef letters. Just in case here it is!

here also the PDF copy of the original article

https://www.science.org/doi/pdf/10.1126/sciadv.adg3200?download=true

Enjoy the rest of the day,

André

Scientists Solve a Sea Urchin Murder Mystery

https://www.smithsonianmag.com/smart-news/scientists-solve-a-sea-urchin-murder-mystery-180982096/

A microscopic parasite that has been killing the Caribbean creatures since
last year might also be at fault for a population collapse four decades ago

Carolyn Hagler <https://www.smithsonianmag.com/author/carolyn-hagler/>

Staff Contributor

May 8, 2023 10:36 a.m.

[image: sea_urchin_photo.jpg]

Diadema antillarum sea urchins in the Caribbean Sea Reinhard Dirscherl /
ullstein bild via Getty Images

Since last year, long-spined sea urchins in the Caribbean Sea have been
dropping dead with no known cause. Now, scientists may finally have found
the culprit.

The species, called Diadema antillarum, has faced dire times before:
Between 1983 and 1984, roughly 98 percent of them mysteriously died
<https://www.flseagrant.org/scientists-discover-cause-of-sea-urchin-die-offs-in-the-caribbean-a-protozoan-parasite/#:~:text=The%20most%20recent%20sea%20urchin,from%20future%20events%20like%20it.>.
Their defensive needles that shield their bodies fell off completely,
leaving them easy prey for surrounding predators.

Then, the negative effects cascaded: Without as many sea urchins, coral
reefs became more vulnerable to algae take-overs and deterioration.
Typically, the urchins eat algae, which competes with coral and grows all
over it, blocking sunlight. Since that mass urchin die-off, only 12 percent
of the original population has been restored—and urchins and coral reefs
alike have suffered as a result.

So, in 2022, when the sea urchins suddenly began dying at rapid rates
<https://news.cornell.edu/stories/2023/04/massive-caribbean-sea-urchin-die-caused-parasite>
once
again, researchers quickly searched for an explanation for the
collapse—which could hold serious consequences for the whole aquatic
ecosystem.

After four months of sleuthing, scientists reported in Science Advances
<https://www.science.org/doi/10.1126/sciadv.adg3200> in April that they
successfully solved the sea urchin murder mystery. The killer: a
microscopic parasite that appears “cute,” says Mya Breitbart
<https://www.usf.edu/marine-science/faculty/faculty-directory/biological-oceanography/mya-breitbart.aspx>,
the team’s lead researcher, to Matt Cohen of the Tampa Bay Times
<https://www.tampabay.com/news/environment/2023/04/19/usf-professor-st-petersburg-discovery-killing-sea-urchin-florida-caribbean/>
.

“I never thought I would be able to solve a mystery like this in my
career,” Breitbart, a biological oceanographer at the University of South
Florida, tells the Tampa Bay Times. “We so rarely actually figure out the
cause. So just being a part of that was really incredible.”

When Breitbart started seeing the sea urchin deaths increase, she put
together a team of 48 scientists from 12 different countries. They worked
together tirelessly to crack the case, which happened much faster than
they’d anticipated.

“Science never works like this,” says Breitbart to the Times.

Massive Caribbean sea urchin die-off caused by parasite

By Krishna Ramanujan <ksr32 at cornell.edu>

April 19, 2023

https://news.cornell.edu/stories/2023/04/massive-caribbean-sea-urchin-die-caused-parasite

https://youtu.be/y5JJrQiCyVI

The culprit—a parasite known as a ciliate—is a single-celled, fuzzy-looking
amoeba that uses its many hairs to swim. Ciliates can commonly be found
inside living organisms, including sea urchins, but they are usually
harmless to the spiny creatures. This particular type of ciliate, however,
called a scuticociliate, has caused mass die-offs of other marine species
before, according to a statement
<https://www.usf.edu/marine-science/news/2023/scientists-identify-2022-sea-urchin-killer.aspx>
.

While the ciliate’s involvement was unexpected, after scientists studied
urchins from 23 sites in the Caribbean, there was no denying what had been
the murderer. They collected urchins from sites where illness had struck,
picking up animals that looked sick and some that looked healthy. For
comparison, they also collected healthy urchins from sites that had not
seen die-offs. When researchers noticed the parasite was present in the
sick urchins’ muscles, they tested whether adding it into a tank would make
healthy sea urchins sick. Sure enough, the ciliate infected the animals in
the lab, and within just days, they had lost their spines and become weak.

Researchers speculate that this amoeba could be the same parasite that
drove the steep sea urchin decline 40 years ago, but because they do not
have sea urchin samples from that time period, they can’t confirm this idea.

In the future, climate change could play a role in the parasite-driven
demise of other species, Ian Hewson <https://cals.cornell.edu/ian-hewson>,
lead author of the study and a marine ecologist at Cornell University,
tells the Atlantic
<https://www.theatlantic.com/science/archive/2023/04/sea-urchin-die-off-source-ciliate/673817/>’s
Ed Yong. It has put creatures under additional stresses, lowering the
strength of their immune systems. Organisms that never interacted before
are crossing paths due to climate change forcing them into new areas,
resulting in an exchange of pathogens
<https://www.theatlantic.com/science/archive/2022/04/how-climate-change-impacts-pandemics/629699/>
.

“Things that maybe weren’t related to mass mortality in the past will start
to cause new diseases,” says Hewson to the Atlantic. “I’d fully expect us
to see more of this kind of thing in the future.”

While pinpointing the sea urchins’ killer is essential in the process of
halting their death, scientists are still trying to figure out the best way
forward to save them, and in turn, save the suffering coral reefs
<https://www.smithsonianmag.com/science-nature/the-planet-has-lost-half-of-coral-reefs-since-1950-180978701/>
.

“Coral reefs in the Caribbean are in trouble,” Don Levitan
<https://www.bio.fsu.edu/faculty.php?faculty-id=levitan>, a marine
biologist at Florida State University who was not involved in the study,
tells the Associated Press
<https://apnews.com/article/sea-urchin-caribbean-deaths-e328a797c9eedd725384dacc81a5e460>’
Maddie Burakoff. He remembers a time before the sea urchin die-off, when
coral reefs were thriving and the spiky creatures had a large presence in
Caribbean waters. “We’re at a different place than we were 30, 40 years
ago.”

Although scientists are not yet sure how to solve this parasitic problem,
the quick turnaround of the new study has put them ahead of the game for
the next step: figuring out solutions.

“This time,” Don Behringer
<https://ffgs.ifas.ufl.edu/faculty/behringer-donald/>, a co-author and
marine ecologist at the University of Florida, says in the statement, “we
know the culprit.”