Review: June 2019

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In the fall of 2013, photos and videos, began to appear on the web documenting a marine die-off in British Columbia that turned starfish into walking dead. “The animals seemed to waste away, ‘deflate’ a little, and then just . . . disintegrate,” wrote a horrified dive blogger. Afflicted starfish would rapidly weaken and lose their grip on sheltering rocks; their arms would detach from their bodies and crawl away, and their entrails would fall out, turning stretches of Northwest coastline into charnel house floors. The outbreak rapidly spread south to California, decimating not only wild starfish in intertidal zones, but captive specimens in the Vancouver, Seattle, and Monterey aquariums.

To Drew Harvell, a professor of marine ecology at Cornell University who specializes in infectious diseas-es, the grim news felt like a “lightning strike hammering the entire guild of West Coast starfish,” and an urgent call to save a beloved species from extinction. Localized wast-ing events like this had been seen before, but nothing as widespread or as fast-moving, and biologists had no idea what the infectious agent was, or whether microorganisms were involved at all. No obvious environ-mental triggers could be identified—the epidemic didn’t occur during an episode of extreme warm or cold water, low oxygen level, or unusually high pollution. And so, to unravel the mystery, Harvell assembled an A-team of specialists: a Cornell colleague who specializes in read-ing the DNA of viruses; a pathologist from the Wildlife Conservation Society (Bronx Zoo), who scrutinized thousands of histological slides looking for bacteria, fungi, and other parasites; and a large supporting cast of graduate students, National Park Service rangers, and amateur divers who collected and dissected specimens from various sites.

The search for the starfish-bane is a gripping tale that offers valuable insight into how scientists can mobilize to deal with an environmental crisis. The infectious agent, named the “sea star-associated densovirus,” was eventually identified, and some—though not all—West Coast starfish are beginning to make a comeback on their own. Harvell presents other cases of infections that affect corals, abalone, and salmon, some with less happy endings. But her broader message is that marine disease is an environmental threat needing far more serious at-tention. Some infections, like those in salmon, directly threaten our food supply; others, like those in starfish and coral, destroy iconic creatures of the sea, and can have disastrous consequences for the complex web of shoreline and reef creatures that depend on them.

Disease is one element of ocean health, which Harvell lucidly de-scribes in this book, but she con-cludes that it is intimately tied to all the others. “Limiting carbon emissions, doing a better job of managing fisheries and marine protected areas, changing the economic pressures that lead to despoiling of marine environments, and managing population growth will all reduce the risk of infectious disease outbreaks.”