The core argument of the recently published paper it links to (http://www.pnas.org/content/early/2014/11/12/1416625111.full...) is this:
1) No non-viral cause can be found
2) Viral load is higher in symptomatic animals
3) Animals inoculated with homogenized tissue from symptomatic animals almost all become symptomatic.
This argues strongly for a viral cause. The argument for the specific virus in question is much less strong, although it does look like a plausible candidate. The reason it is less strong is that the testing is entirely non-specific, and a plausible alternative explanation is that the symptomatic animals are having a tough time of it, immunologically, so an endemic but harmless virus is opportunistically going hog wild.
The thing that puts this article into junk science reporting territory is its ritual invocation of climate change, which others have pointed out. Let me be specific about what I see as the issues.
The article says flat-out that temperature is not an issue, because the animals don't get better when the temperature drops: "But the current die-off is different. Not only is it bigger, it doesn’t seem to be linked to water temperature. Where other die-offs had slowed down when the waters cooled, this time, the sea stars kept dying through the winter of 2013-2014."
Then it contradicts itself and insinuates that maybe it's climate change after all!:
The virus probably isn’t the whole story, both Lahner and Raimondi say. Lahner took sea stars that were disintegrating at 54 degrees Fahrenheit and cooled their water to 50 degrees. "They all went from falling apart, having their viscera hanging out, to pretty healthy in a day," she says. "I came back, and they were like, ready for the cover of Vogue. They were perfect." So temperature may play a role in the animals’ ability to recover as well.
The north Pacific basin, on average, has warmed by about half a degree centigrade from 1955 to 2013, according to data from the National Oceanic and Atmospheric Administration. "That’s kind of a scary number," says Andy Allegra, a NOAA data specialist. "It’s very large."
There is likely something interesting going on here, but this is a pretty big "hmm... that's odd" moment that just goes by un-noticed.
Water temperatures around Vancouver are in the 60's in the summer, and drop to the low 40's or even into the 30's in the winter, so you would expect a huge seasonal effect if a change from 54 to 50 resulted in unhealthy animals suddenly being ready for the cover of Vogue". And yet--as quoted above--we are assured that the die-off continued in winter (even as far south as San Diego water temperatures can dip below 50 in January).
So this article contains a contradiction of Biblical proportions, the kind of junk reasoning you see in the gibberish of 9/11 conspiracy theorists and climate change denialists (the real kind, who think it's a hoax, not people like me who think nuclear power is a good option for dealing with it, although I often get accused of denialism on that basis.)
Science is the discipline of publicly testing ideas by systematic observation, controlled experiment and Bayesian inference. One way we test ideas is by testing as much of their deductive closure as possible: that is, all the things that would be true if the idea was true. If that "big scary number" was in any way significant, we'd expect a huge seasonal effect in the die-off, which is not observed.
Furthermore, if temperature has a huge effect in the laboratory and none in the field, there is something missing. Maybe that missing thing is pH, as the article suggests, but note how the otherwise data-heavy account gives no actual numbers on ocean acidification, merely telling us coyly that the oceans have become less basic, not how big the change is? That's because the story is really complicated and quite local--ocean pH varies a lot between locales, and yet seafood manages to grow everywhere: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjourna...
There is also curiously little mention of the effects of sea-star over-population on this outbreak of (likely) disease. Times were good for West Coast sea-stars in the mid-2000's. I saw species I'd never observed in the '80's or '90's. Population crashes, often due to disease, are not uncommon in nature following population booms. This natural boom/crash cycle is mentioned in passing, but not really given the attention it deserves. Deer populations on Vancouver Island are booming right now too, and when they crash in a few years it won't be due to climate change, although the specific causes may remain mysterious.
So this could have been an interesting story on the difficulties of doing good science in a complex natural setting. Instead it invoked the "climate change scary!" meme that has infected virtually every story that has anything to do with anything that happens on a scale larger than a single urban neighbourhood. It does no particularly good service to science to say, "I'm sure climate change is the cause but I can't prove it!" If you're sure, you're not doing science: Bayesian reasoning does not produce certainty.
And being "sure" of something you don't have anything like sufficient evidence for is not a good attitude for a scientist to have, and putting it on display like this emboldens those who believe that rather than being an alternative to faith, science is just another kind of faith (which it is not: http://www.tjradcliffe.com/?p=1331)