The domino effect of an underwater disease outbreak

Drew Harvell

Disease outbreaks are a challenge because they are like lightning strikes — occurring unpredictably and rapidly. To identify their causative microorganisms or stop them from spreading requires significant scientific investigations on short notice, but traditional government funding sources are slow. This leads to a dangerous gap in support when we should be moving into high gear to respond to emergent diseases.

Imagine how the challenge intensifies when the outbreak is underwater, in the ocean, where it can reach a large scale before we even notice.

This past summer, I worked in the Pacific Northwest and we had no tools to manage the spread of starfish-wasting disease. It was an unprecedented disease outbreak, the largest marine wildlife outbreak ever recorded in terms of number of species, and spread from Alaska to Mexico. An outbreak that has big implications for humans, including fisheries upon which local economies are built.

This week, a new bill is being introduced by Rep. Denny HeckDenny HeckHeck enjoys second political wind Incoming lawmaker feeling a bit overwhelmed MORE (D-Wash.), the Marine Disease Emergency Act, which would provide emergency funding to help mount a rapid response to outbreaks such as the one that is causing starfish by the millions to shrivel, lose limbs and die. With marine diseases projected by the National Climate Change Assessment to increase in warming ocean conditions, this bill is timely. It will allow scientists like me to leverage rapid funding and come up with proactive measures to protect our valuable marine fisheries and biodiversity.

Not all marine disease outbreaks constitute emergencies, but this bill would help us in extreme cases, when there is ecological, economic or social disruption.

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An emergency causing ecological disruption can include immediate losses of biodiversity, local extirpation or extinction, or disruption of ecosystem services. Massive seagrass epidemics, occurring first in the 1930s and, more recently, in the 1980s in Florida, are an example of this. Each outbreak extirpated an entire ecosystem that had provided valuable ecosystem services and habitat for important species.

An emergency that threatens large economic losses can include disruptions to wild fisheries, aqua-cultured species or threats to essential marine habitats. In a recent study, Kevin Lafferty of the University of California, Santa Barbara catalogued 67 different pathogens that can impact the economy of marine resources. The most costly epidemics have been those affecting commercial species. A shrimp white spot outbreak cost billions globally following a global pandemic that started in the 1980s. Disruptions to biodiversity can also threaten tourism revenue. For example, large-scale coral bleaching and disease can close marine parks and destroy vast areas of coral reefs, which are essential fish nurseries.

An emergency that threatens social or cultural values may jeopardize public safety and health. This includes unsafe seafood and beaches. The seafood-borne bacterium Vibrio parahaemolyticus causes human gastroenteritis, usually associated with the consumption of raw oysters. One serotype of this species is more unsafe and appears to be spreading.

In the starfish epidemic, we are seeing animals literally disintegrate on both coasts, from Maine to Mexico. The West Coast outbreak was first noticed by park rangers in Olympic National Park in June 2013. Soon after, thousands of sunflower stars began falling off underwater rocks north of Vancouver. It spread rapidly. In November 2013, there was a massive hit in Monterey, Calif., with over eight species dying in catastrophically high numbers over the course of weeks. At about the same time, all the captive stars in the three major West Coast aquariums died in their tanks, including some that had made their homes there for over 25 years.

This summer, the outbreak worsened in Oregon and Washington state and the most common species are now very rare from Southern California to Washington. Alaska remains the final frontier and this points to its vital placement as a refuge and potential reservoir for some marine resources on the entire West Coast.

Why would a bunch of starfish dying be an emergency? Even mass mortalities are not an emergency if the die-off is localized, the outbreak is self-limiting, the system is resilient to the loss of the host or the infectious agent does not put human health at risk.

There are three reasons this epidemic is an emergency. It is the biggest marine disease outbreak of non-commercial species. Several of the species are "keystone," meaning that when they die, the ecosystem is radically altered, which can ultimately impact humans. This domino effect can cause cascading change under the ocean. Lastly, most of the starfish are species that are natives in their tidal homes. If they disappear from their entire range on the U.S. West Coast, we cannot repopulate them from anywhere else on the planet.

While we scientists haven't yet solved all the parts of this mysterious disease, one thing we have learned is that warming oceans are contributing to the spread and the death rate. Earlier this summer, coastal waters along much of the West Coast were warmer than at any other point in the last 25 years. On both land and in the sea, many disease-causing microorganisms do better under warming conditions. These are the kinds of events we expect in warming waters.

Passing the Marine Disease Emergency Act will provide a much-needed source of rapid response funds for marine disease outbreaks. Battling this particular starfish die-off has been challenging, with funds cobbled together from foundations, the Nature Conservancy, private citizens and even a donation raised by schoolchildren from Arkansas. The potential for ecological, economic and social consequences demands that resources be available when outbreaks occur. Ocean health has benefited greatly from Secretary of State John Kerry's recent launch of Our Ocean 2014 to dial back pollution and ocean acidification and improve fisheries management. Combined with swift passage of Rep. Heck's Marine Disease Emergency Act, we can prevent disease in our oceans from evolving into a global disaster.

Harvell is a professor of ecology and evolutionary biology at Cornell University and faculty fellow  at Cornell's Atkinson Center for a Sustainable Future.

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