A sea of troubles: Marine ecosystems send an SOS

Harvell’s lab at Cornell is devoted to studying the health and sustainability of coral reefs and seagrass beds, particularly how they’re affected by outbreaks of infectious disease fueled by climate change. A leading figure in the worldwide movement to safeguard marine ecology, Harvell has led a World Bank-funded project to study the sustainability of coral reefs as an economic resource, co-authored a chapter of the U.S. government’s 2014 report on climate change, and helped craft federal legislation (introduced in 2015, but not yet passed) that would provide emergency funding to study marine disease outbreaks. In February 2018, her work got a shout-out from none other than the U.K.’s Prince Charles, who noted the findings of a recent paper of which Harvell was senior author. In an address in London’s Fishmonger’s Hall marking the International Year of the Reef, the prince decried such problems as bleaching, destructive fishing, and land-based pollution.

“If that were not enough, ladies and gentlemen,” said Prince Charles, “we now understand that the scourge of plastic in the ocean is causing the rapid increase of lethal coral diseases.”

That work, and more, is the subject of Harvell’s most recent book, Ocean Outbreak: Confronting the Rising Tide of Marine Disease, published last spring by the University of California Press. In it, she describes how disease has struck four types of ocean life: abalone, coral, salmon, and starfish. As she explains it, human-driven factors like plastic pollution and rising water temperatures have enabled microbes—what she calls “these tiny monsters in the sea”—to proliferate, putting not only marine creatures but whole industries (such as fishing and tourism) and even human lives at risk. “The battle between hosts and pathogens is age-old—it’s a normal process—but this warming, coupled with a lot of other things that have been going on in the ocean is giving the edge to the microbes, who can evolve and grow so much faster in warmer waters,” Harvell says. “So we’re tipping the balance—and man, are these microorganisms capable of taking advantage of it. Almost all the outbreaks we’ve studied are accelerated or fueled by warming.”

Harvell is talking with CAM via videoconference from the western shore of Washington State’s San Juan Island, where the view from her house stretches across the Haro Straight to Canada. Harvell spends part of each year on the island, located two hours north of Seattle; she’s on the Hill for fall semester, and in the spring leads a program that takes Cornell undergrads to the Big Island of Hawaii and to San Juan Island’s Friday Harbor Marine Laboratories for courses and field work in oceanography and the biology of marine invertebrates. Much of each summer is spent conducting research in the waters off North America’s Pacific coast—the day before, she was out with a Smithsonian team using drones to map and assess the health of local seagrass beds, in decline since a marine heat wave spurred disease outbreaks several years ago—which she has been studying since her grad student days.

A devastating epidemic in Pacific waters kicks off Ocean Outbreak: a massive die-off of starfish that began in fall 2013 and resulted in heavy losses of at least twenty species. Affecting stars along their entire habitat range—as Harvell puts it, “from the Mexican border all the way up to the Aleutian Islands in Alaska,” as well as populations of captive stars in three major public aquariums—the outbreak became the single largest of its kind in history. (The losses so upset one class of sixth graders in Arkansas, they sent Harvell’s lab a $400 check to help fund research.) As Harvell describes in the book—in a chapter that a Forbes review likened to a suspense thriller—she was attending a conference in California when a colleague called to report a gruesome scene on Seattle’s Alki Beach. Harvell and her husband (oceanographer Charles Greene, a professor of earth and atmospheric sciences at Cornell) quickly hopped on a plane and made their way to the site. “We saw four purple stars clustered together, half in the water, with twisted arms and small lesions; we would come to recognize these as telltale signs of the wasting disease,” Harvell writes. “As we walked along the water’s edge, we found more and more arms and parts of stars. I realized, with a sick feeling, that the beach was littered with them. Many were clearly dead, but occasionally, we would find one with moving tube feet, or a star in the process of having its arm tear away from the body and walk off on its own. It was so unreal and unnerving.”

As Harvell goes on to describe, lab experiments and field studies eventually identified a virus as the likely culprit—and established that the casualties were much heavier in warmer waters. While some starfish species have developed resistance and their numbers are beginning to rebound, one important kind—the sunflower star, which can grow to the size of a manhole cover and have up to two dozen arms—has all but vanished in the region. And because sunflower stars are major predators that keep prey like sea urchins under control, their absence has had significant consequences. “In California, where it’s warmer, there are no sunflower stars in many sites, and huge numbers of sea urchins have been mowing down the kelp beds, which are important habitats,” Harvell explains. “So it’s a system out of balance, driven by one of these tiny monsters—a microbe in the ocean.”

The results of the starfish study were published in Science Advances in January 2019—a year after another major paper by Harvell and colleagues, about the connection between plastic waste and marine disease, had similarly generated headlines. While environmentalists and laypeople alike were already concerned about plastic’s harm to marine animals—due, in part, to poignant images like a viral video of a sea turtle with a straw jammed in its nostril—the January 2018 paper, published in Science, demonstrated that it also damages oceans in more insidious ways. In that study of more than 124,000 corals in Southeast Asia—the work that Prince Charles cited—researchers detected disease in 89 percent of corals that came into contact with plastic waste, compared with just 4 percent of those that did not. “Potato chip bags, single-use plastic bags, plastic bottles—things that got wedged and crammed on the reef,” Harvell says, “they created little abrasions in the coral that allowed infections to get in. Or they were even conveying infections; a lot of this plastic was really dirty.”

As distressing as those findings were, Harvell says there’s some reason for optimism.

While tackling the underlying causes of climate change is a herculean task, the harm caused by plastic can be mitigated through the straightforward means of proper waste management. (As she notes in the book, the researchers found more than fifty times as much plastic in the waters around Indonesia than around Australia, which has far superior waste disposal practices.) And just the fact that the paper got so much coverage—in news outlets from the New York Times to the BBC to NPR—was a positive sign. “We were pleased that ocean health was finally getting the attention it needed,” she writes. “While crafting ocean policy is not currently our job, doing the relatable, strong science that creates a foundation for policy change is, and we had hit a home run.”

Another potentially promising way to improve ocean health that Harvell espouses in the book: the protection and expansion of seagrass beds, which she and her colleagues have found serve as a natural filter that removes pathogens from the water. That work was inspired by a research trip to Indonesia during which Harvell and her teammates fell severely ill from dysentery and had to cut the visit short. They later returned, determined to learn what had made them sick, and found that the water they’d been diving in was contaminated with human sewage—but that levels of harmful bacteria (including those that cause diarrhea, meningitis, tetanus, and cholera) were dramatically reduced in seagrass meadows. Furthermore, corals located among seagrass were less likely to be diseased, establishing what Harvell calls a “critical link between human and coral health.” As she writes:

“This gave us a positive and practical way forward. If we conserved and protected seagrass beds . . . we could slow deterioration of ocean health and possibly prevent some human disease, even in remote places like these sewage-polluted islands.”

Ocean Outbreak is Harvell’s second book; her first, 2016’s A Sea of Glass, explored her work as curator of the Cornell Collection of Blaschka Invertebrate Models—a menagerie of some 570 intricate, highly accurate sculptures of marine creatures. Crafted by a father-son team of Dresden glassmakers in the nineteenth century, they were purchased by the University as teaching tools at the behest of founding president Andrew Dickson White. The book—which Smithsonian called one of the year’s top “art-meets-science” releases—details not only the collection and its history but Harvell’s attempts to find living examples of the animals the sculptures depict, in an era when climate change and other factors have put habitats at risk.

That ongoing effort is also the subject of Fragile Legacy, a 2015 short film narrated by actor and activist Ted Danson and directed by David Brown ’83, a longtime environmental videographer and Harvell collaborator. The thirty-minute movie, which Harvell and Brown ultimately hope to expand into a full-length film, includes footage of Harvell searching for real-life versions of Blaschka creatures—for example, looking for a common octopus (Octopus vulgaris) in waters off Hawaii while chronicling the effort to restore the damaged Blaschka sculpture of the creature.

The film also details threats to ocean life, noting that the models—made before the Industrial Revolution ushered in the use of fossil fuels, leading to increased carbon dioxide levels and therefore higher water temperatures—offer a time capsule of life in a more pristine ecosystem. Among the film’s most distressing images: footage of a beach strewn with plastic garbage, and haunting shots of Indonesian reefs destroyed by a devastating practice in which fishermen drop dynamite into the water to stun their prey. “The last international coral reef meeting I went to, there were people in tears, and I was one of them,” Harvell says, reflecting on the overall state of reefs worldwide. “Talk about disheartening—to see these cathedrals of the ocean with the most beautiful, inspiring, exciting foundations of biodiversity being killed, largely by climate change. But we can’t just sit around and be disheartened. We need to move forward—to do what we can to make things better.”

This article originally appeared in Cornell Alumni Magazine.