\n<\/p>\n
It started in the summer of 2013. Sea stars were dying in huge numbers in Washington State\u2019s Olympic National Park: They became covered in white lesions. Then their limbs contorted and fell off, leaving their bodies to disintegrate into a pile of white goo. \u201cThey looked like they were melting,\u201d says Pete Raimondi, an ecologist at the University of California, Santa Cruz and head of the Multi-Agency Rocky Intertidal Network, a consortium of research groups.\u00a0<\/p>\n
The problem spread to sites as far south as Baja California and north to Alaska. Sea stars from more than 20 species were affected, including common five-armed ochre stars in tide pools and sunflower stars \u2014 beasts the size of a hula hoop with up to 24 arms \u2014 that live mostly in the subtidal zone. It hit aquariums, too: The Vancouver and Seattle aquariums lost almost all their sea stars, some of which were 40 years old. Over a dozen years, billions of sea stars perished, with 90 percent of some local populations wiped out.<\/p>\n
\u201cSea star wasting disease\u201d has been called the largest wild marine epidemic of all time. More than a decade since the syndrome was first identified, sunflower sea stars are still critically endangered. While other sea star species are recovering in some places, wasting persists at low levels around the world. And researchers are worried that wasting could come back, hard.\u00a0<\/p>\n
Sea stars were the inspiration for the \u201ckeystone species\u201d concept: creatures without which healthy ecosystems collapse.<\/p>\n
When sea stars are threatened, their whole environment is imperiled. Sea stars were the original inspiration for the \u201ckeystone species\u201d concept: creatures without which healthy ecosystems collapse. In the 1960s, experiments showed that thriving tide pools became overrun by mussels if ochre stars were removed. Sunflower stars are so good at keeping voracious sea urchins in check that, without them, regions can transform to \u201curchin barrens\u201d \u2014 rocky wastelands devoid of any life, including the kelp forests that provide food and shelter for many fish.\u00a0<\/p>\n
Subscribe to the E360 Newsletter for weekly updates delivered to your inbox. Sign Up.<\/p>\n
The rise of environmental stressors \u2014 including pollution, lowered ocean oxygen levels and warming water temperatures \u2014 is thought to be making marine life in general more vulnerable to disease. \u201cIt\u2019s like us, when we\u2019re not sleeping, we\u2019re way more likely to get a cold,\u201d says Melissa Miner, an ecologist who works with Raimondi. The oceans have warmed about 1 degree Celsius since preindustrial times, and that uptick may lie behind an\u00a0increase in reported diseases in urchins and corals. It\u2019s surely stressing sea stars, too, says Miner.\u00a0<\/p>\n
To tackle future outbreaks of sea star wasting, researchers need to know its etiology. But the hunt for the cause has been like a winding murder mystery, with dead ends, red herrings, a suspect fingered then exonerated. This summer, researchers put another suspect in their sights: a bacterium with a long rap sheet for causing illness in both people and marine life. But the case, they say, is still far from closed.\u00a0<\/p>\n
Left: A cookie sea star near Calvert Island, British Columbia, with signs of wasting disease. Right: An afflicted purple ochre sea star near Vancouver Island, British Columbia.<\/span> Chasing down the cause of a marine epidemic is often tricky. Seawater is swimming with all kinds of bacteria and other microbes. During an outbreak, there is often a lack of healthy or unexposed creatures to use as comparisons. Viruses can\u2019t be bred in isolation, making it hard to do cleanly controlled experiments. And oftentimes, little is known about the biology of noncommercial species, such as sea stars, including which bacteria normally live on healthy specimens.\u00a0<\/p>\n Back in 2013, Raimondi, with Ian Hewson at the Cornell Marine Mass Mortality Lab, in Ithaca, New York, and colleagues, began investigating the cause of sea star wasting. When they examined slices of flesh from symptomatic stars under the microscope, they saw no specific bacterial infection. Genomic analysis, on the other hand, turned up a type of virus called a densovirus, which had been detected in Hawaiian sea urchins the year before. Hewson ground up diseased tissue and filtered out anything bigger than a virus, then injected the viral broth into healthy stars: They wasted away. The whodunnit seemed solved.<\/p>\n The research team\u00a0published its results in November 2014, drawing much attention from the scientific community, the press, and the public. But niggling\u00a0questions remained. Tests found more and more densoviruses in normal sea stars, and further experiments trying to infect sea stars were inconsistent \u2014 some got sick, others didn\u2019t. They had done good science, says Raimondi, but the team eventually realized \u201cwe were wrong.\u201d\u00a0<\/p>\n As scientists probed for causes, more outbreaks were popping up, including in China, Australia, and even Antarctica.<\/p>\n What else could it be, they wondered. Protists, or fungi? Maybe it was more than one disease, or not an infectious disease at all. The pattern of spread was odd: Infectious diseases don\u2019t normally hit so many species all at once, nor jump distances of thousands of miles. Maybe the lesions were caused by something environmental. There had been no regional marine heat wave when wasting was first seen, in the summer of 2013, but a particularly epic\u00a0heat wave did begin that October and grew in size and scope in 2014 as the disease continued.\u00a0<\/p>\n Hewson and his colleagues tried drying out stars in the sun for an hour, lowering water flow rates in tanks, and even rubbing the stars to replicate overcrowding. Everything seemed to cause wasting. Meanwhile, more outbreaks were popping up, including in China, Australia, and even McMurdo Sound, Antarctica.\u00a0<\/p>\n With funding from The Nature Conservancy, Alyssa-Lois Gehman, a marine disease ecologist with the Hakai Institute in Vancouver, and Melanie Prentice, an evolutionary ecologist at the University of British Columbia, picked up the case with colleagues in 2020. They worked on it for years, primarily with hard-hit sunflower stars. The hunt, they knew, wasn\u2019t hopeless: Other marine epidemic cases were being solved. Withering abalone syndrome, for example, was traced to a bacteria called Candidatus Xenohaliotis californiensis. And, in 2022, Hewson\u2019s lab pinned a massive die-off of long-spined sea urchins in the Caribbean on a eukaryote called\u00a0Philaster.\u00a0<\/p>\n Cornell microbiologist Ian Hewson\u00a0examining a sea star.<\/span> Prentice and colleagues started by grinding up sick sunflower stars, filtering the slurry, and isolating the part that would contain any tiny viruses. But introducing those viruses to healthy stars, they found, did not make them sick. Genomic analyses of tissue samples were complicated and unclear, but when they looked specifically at coelomic fluid \u2014 the \u201cblood\u201d of sea stars \u2014 a clear difference between sick and healthy stars\u00a0leapt out: a strain of the bacterium Vibrio pectenicida called FHCF-3. When they grew this bacterium and introduced it to healthy stars, they died.\u00a0<\/p>\n As ocean oxygen levels dip, fish face an uncertain future. Read more.<\/p>\n For many, this was a slap-on-the-forehead moment. The Vibrio group contains well-known bad actors, including the bacterium that causes cholera in people and others that cause die-offs in shellfish and fish. The pathogenic members of the group also, generally, thrive in warmer water. \u201cI think the evidence they have is pretty compelling,\u201d says Lauren Schiebelhut, an evolutionary ecologist affiliated with the University of California, Merced, who was not involved with the study.<\/p>\n But while this Vibrio appears to be involved, not all researchers are convinced it\u2019s the key. Hewson, who didn\u2019t respond to interview requests for this article, published a\u00a0response paper noting that this particular strain wasn\u2019t detected in other species of sick stars, so it \u201ccannot be the cause of all\u201d wasting. Plenty of researchers would like to see the work replicated in other species; Gehman says that is ongoing.<\/p>\n Sunflower stars are failing to grow to their previous sizes, and some tiny six-armed stars are completely gone in some areas.<\/p>\n Hewson and Raimondi also think the Vibrio might be a secondary infection rather than the cause of disease. Think of AIDS, explains Raimondi: People who die from this syndrome often succumb to a bacterial infection, but it\u2019s the HIV virus that\u2019s ultimately to blame. Hewson had seen Vibrio bacteria in both his\u00a0urchin study and his work on\u00a0sea stars but largely viewed them as opportunistic bugs feasting on compromised tissue. What lets the bacteria take over, says Raimondi, is as yet unknown.\u00a0<\/p>\n It is a chicken-or-the-egg situation, agrees Melissa Pespeni, who studies the ecology and genomics of marine invertebrates at the University of Vermont. What we need to figure out, she says, is what\u2019s \u201cthe additional stressor that is now allowing these Vibrio to become so pathogenic.\u201d<\/p>\n \u201cThere\u2019s still a lot of questions,\u201d says Schiebelhut. \u201cWas it there in the environment before? Is there some mutation involved? I\u2019d like to see a lot more analysis of the pathogen itself and experiments in other species. But right now, this is the strongest evidence that we have for a pathogen.\u201d<\/p>\n Ecologist Alyssa Gehman studies sunflower sea stars in Burke Channel, British Columbia.<\/span> Today, ochre sea stars have largely bounced back from wasting. In fact, they went into a baby-making frenzy when the epidemic struck in 2013, says Schiebelhut,\u00a0<\/strong>at up to\u00a0300 times their previous rate of reproduction. The post-epidemic babies\u2019 genetics are more similar, she says, to adults that survived the onslaught, hinting that they\u2019re now more resistant.\u00a0<\/p>\n Miner says there\u2019s no concern about ochre stars going extinct, though there are far fewer now than before 2013.\u00a0<\/strong>Sunflower stars, however, are failing to grow to their previous large sizes, she says. And some tiny six-armed stars are completely gone from some areas. \u201cWho knows when or if they\u2019ll ever come back,\u201d Miner says.<\/p>\n Marine treatments are possible, if tricky. Some corals, for example, are being experimentally treated with probiotics to fight off suspect bacteria behind stony coral tissue loss disease \u2013 either by putting a bag around a coral and injecting the probiotic into the contained water or by smearing probiotic paste onto coral lesions \u2013 with\u00a0variable\u00a0levels of success. Something similar could in theory be done for, say, a critical patch of sea stars in an important kelp forest. Researchers are also hunting for a phage \u2014 a virus that affects bacteria \u2014 that might tackle this Vibrio. (Biologists have found one that naturally helps wild\u00a0abalone\u00a0resist withering from Candidatus bacteria.) \u00a0<\/p>\n Researchers are trying to pin down genes that protect sea stars from wasting so breeding programs can select for them.<\/p>\n A parallel idea is to make sure that aquarium specimens are as robust as possible, to serve as a backup in case of disaster. Several facilities, including the nonprofit Sunflower Star Laboratory in Moss Landing, California, are breeding sea stars with the hope of transplanting them to help suffering populations recover. Sea stars in aquariums are now treated with antibiotics or probiotics, cool water baths, and extra oxygen when they show signs of stress or disease, says Martin Haulena, director of animal health at the Vancouver Aquarium.<\/p>\n Others, including Schiebelhut, are trying to pin down genes that help protect sea stars from wasting so targeted breeding programs can intentionally select for them. But that can be a risky game, says Pespeni, since overcoming the next assault could require a different genetic makeup.\u00a0<\/p>\n Shrinking Cod: How Humans Are Impacting the Evolution of Species. Read more.<\/p>\n In general, cooler waters seem to keep disease at bay. There are cool fjords in British Columbia, for example, says Gehman, where sunflower stars are still thriving. We need to do \u201cwhatever we can do to slow global climate change and slow pollution,\u201d says Pespeni. \u201cYou can treat locally and hopefully help in an acute situation. But if it happens again the next week, or if whatever the stressor or pollutant is that\u2019s causing it doesn\u2019t go away, then it\u2019s a lot of time and energy and money for treatment that\u2019s not a long-term solution.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" It started in the summer of 2013. Sea stars were dying in huge numbers in Washington State\u2019s Olympic National Park: They became covered in white lesions. Then their limbs contorted and fell off, leaving their bodies to disintegrate into a pile of white goo. \u201cThey looked like they were melting,\u201d says Pete Raimondi, an ecologist<\/p>\n","protected":false},"author":1,"featured_media":41334,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[50],"tags":[788,363,4646,1956,11002,464,5004,622,264],"class_list":{"0":"post-41333","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-key","9":"tag-killing","10":"tag-murder","11":"tag-mystery","12":"tag-ocean","13":"tag-sea","14":"tag-species","15":"tag-star","16":"tag-whats"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/41333","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=41333"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/41333\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/41334"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41333"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41333"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41333"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n Grant Callegari \/ Hakai Institute; Steve Rumrill \/\u00a0Oregon Department of Fish and Wildlife<\/span><\/p>\n
\n Cornell University<\/span><\/p>\n
\n Bennett Whitnell \/ Hakai Institute<\/span><\/p>\n