Amateur naturalists are monitoring the sea star die-off in Oregon.

Before the densovirus was identified, in late 2014, as the physical cause of sea star wasting disease, two theories were frequently advanced as to its cause: warmer waters due to the El Nino current (which occurs every two to seven years off the West Coast), and radiation effects from the March 11, 2011 Fukushima nuclear facility disaster.

The University of California, Santa Cruz, has assured researchers that the onset of the wasting disease has pre-dated the Fukushima disaster. That is, there have been other instances of wasting disease, affecting various forms of sea life. While the current outbreak has a start date after the Fukushima event, no connection to the Fukushima radioactive polllution of seawater has been made.

El Nino continued to be a contender explanation, as die-offs of plankton and fish were sometimes associated with El Nino’s warming of surface waters.

But without any concrete knowledge, the most that nature enthusiasts could do was to track the progress of the disease by monitoring the tidepools and becoming as knowledgeable as possible.

Dr. Lisa Gardiner, in August, 2014, reported to Scientific American readers on the problem:

People woke early to greet the low tide at Cannon Beach, Oregon, in late July. They wandered through sand to a pillar of stone at the edge of the Pacific called Haystack Rock. Some were looking up at birds, but most of us were looking down into the tide pools. We were saying hello to the invertebrates that cover boulders. And we were saying goodbye to the sea stars.

Sea stars have been dying of sea star wasting syndrome along the Pacific coast in large numbers during the past year. Recently the plague has made its way to Oregon. At Haystack Rock, the stars started dying in June – first the larger sunflower stars, then the ochre sea stars.

A group of volunteer naturalists called the Friends of Haystack Rock was on hand to field questions. One volunteer pointed out a sick sea star. It had a white spot on one of its arms but otherwise looked fine to the untrained eye. “That one will be dead in a week,” she said sadly. A visitor asked her why this was happening. We don’t know, she responded.

She is right that there is a lot that we don’t know about this specific event. However there is also a lot we do know about what causes sea star die-off in general.

The afflicted sea stars disintegrate after getting one or more white spots, lesions that mark the early stage of the syndrome. As the lesions grow, arms break off the body and the rigid plates of the star’s skeleton turn to mush. This is most likely due to a virus or bacteria according to epidemiological studies. We also know that the seawater has been warmer than usual and that pathogens tend to thrive in warmer water.

Sea star wasting syndrome has struck before on the West Coast – during El Niño events when ocean temperatures are warmer than usual in the eastern Pacific. This time around, the pattern of sea star die-offs hasn’t been like it was during previous El Niño events. Sea stars are turning to mush at a much higher rate.

El Niño isn’t following the pattern this year that it has in the past either. During a typical El Niño, weaker upwelling off the coast of South America leads to a tongue of warm water stretching across the surface of the tropical Pacific. This was projected to occur this year. But there has been unusually warm water throughout the Pacific this year. Scientists at NOAA speculate that El Niño has not kicked in yet because the atmospheric side of El Niño relies on a temperature gradient across the Pacific, which we are not seeing, at least not yet. (See the National Oceanic and Atmospheric Administration’s (NOAA’s) ENSO (El Nino Southern Oscillation) Blog for the latest El Niño updates.)

The rest of Dr. Gardiner’s article may be read here.

Another example of how marine scientists are monitoring the catastrophic die-off is seen in Monterey Bay, California. Click the next page number for that update.