By Becky Hoag

As carbon dioxide gets released into the atmosphere, the planet warms by trapping in the sun’s heat. Most of that heat gets absorbed by the ocean, lucky for us, but unlucky for ocean organisms. A small change in ocean temperature is a large change for those species and larger ecosystems and, because of this, these organisms get easily stressed out by the warmer waters.

 

The beginning of summer 2013 was met with a phenomenon that left many scientists shocked: sea stars started dying along the West Coast of North America in greater amounts than ever recorded. Initially, the disturbance started in Washington, but by that summer, the phenomenon was recorded as far south as Mexico and as far north as British Columbia. Sea stars’ tissue decayed, leading to death in a manner of days. The decaying occurred faster than the sea star could regenerate its limbs and seemed to spread quickly from one sea star to the next. The symptoms they seemed to be experiencing became known as the sea star wasting syndrome (SSWS).

 

One sea star species hit hardest was the ochre star or Pisaster sp. This star is considered a keystone species, meaning the species can effectively shape an ecosystem at a greater proportion than their abundance would expect. Therefore, the ochre star population’s decline was detrimental to the environments in which they lived. Less of them meant less predators for mussels, which outcompeted surrounding algae for space. And without a diverse number of algae, less organisms can survive in those ecosystems.

 

Another major sea star species that experienced massive die-offs was the sunflower star (Pycnopodia helianthoides), one of the largest sea star species and a major predator of sea urchins and other sea stars. According to UC Santa Cruz’s ecology and evolutionary biology department, sunflower stars were one of the first sea stars to be effected by SSWS. Soon after, other species would succumb to the wasting syndrome.

 

Sea star wasting syndrome began to slow down towards the end of 2014; however, it left disaster in its wake. Three years later, the coastal ecosystems affected are still picking up the pieces.

 

This summer Mackenzie Moran and Gretchen Rude, two undergraduates from UO’s Oregon Institute of Marine Biology (OIMB) Invertebrate Zoology class, catalogued the percent of ochre stars with SSWS by a Charleston, Oregon boathouse. Mimicking the same descriptive study conducted by OIMB Education Program Assistant & Senior Research Associate Maya Watts when she was a graduate student, they found that 10% of sea stars in that area were wasting. However, this was good news: Watts recorded that 80% of sea stars were wasting in that same location just three years before.

 

While the sea star population has shown remarkable resilience, there is still the concern that SSWS will return soon with a vengeance. Scientists moved quickly to find out what caused it and why the syndrome was so much stronger than it ever had been. They soon discovered that SSWS is caused by a densovirus (SSaDV), which can be spread very easily, especially when its victims are stressed. With that knowledge, scientists looked back at previous cases of echinoderm mass mortality to see what made the sea stars so stressed.

 

Sea stars, basket stars, brittle stars, sea urchins, sea cucumbers and sand dollars are all considered to be echinoderms. They share many biological features including tube feet, body symmetry and the same larvae type.

 

There have been many recorded instances of echinoderm mass mortality, such as sea urchin “balding;” however, these instances were due to a bacterium, not a virus. The last two instances of a virus-caused echinoderm wasting epidemic was 1983 to 1984 and 1997 to 1998. Both were sea stars wasting and associated with an El Niño ocean warming, according to National Geographic.

 

The connection between warmer waters and an increase in epidemic size makes sense; warmer waters stress organisms like sea stars, making them more susceptible to syndromes. While there wasn’t an El Niño in 2013 but an influx of warm water along the West Coast, named “The Blob” flowed in around that time. Scientists believe that The Blob formed thanks to an increase of glacial melt, which scrambled the natural ocean currents.

 

In other words, these disturbances in ecosystems and species connect to the realities of global climate change. If ocean waters continue to warm, epidemics like the Sea Star Wasting Syndrome will be more commonplace.

 

Sea Star Wasting Disease
Tidal Pools

Photographs by Topacio Beerhalter, Ty Boespflug, Pam Cressall, Jeff Dean, Jessica Douglas, Justin Hartney,

Anna Rath, Naomi Shao, Jake Smith, Cheyenne Thorpe, Tim Vandehey

Tidal Pools
By Becky Hoag Sea Star Wasting Disease