Saving sea stars

An unhealthy sea star

Photo by Melissa Miner

An unhealthy sea star

Angie Colman, Feature writer

The marine ecosystem of the West American Coastline was devastated in 2013 to 2015 by a massive disease epidemic that killed off thousands of starfish. The worst of it seems to be over but scientists are still puzzling over what happened.

It spanned from near Vancouver, all the way down to San Diego, affecting some of our favourite aquatic animals starfish, in particular, the Ochre Sea Star.

There is speculation about the cause of the disease and a mountain of research has been done on the epidemic known as Sea Star Wasting Disease (SSWD), to understand why it happened, what it did to the environment, and how future outbreaks can be avoided.

One study published earlier this year in PLoS was conducted by MARINe  – the Multi-Agency Rocky Intertidal Network.

In their paper the researchers explained the horrors of what this disease does:  Typically a star fish will get little sores on the top of its body, then around these wounds the disease will decay the flesh of the living animal, leaving it “melting” into it’s rocky habitat. This only takes three days.

After literally melting away, the starfish has an internal organ failure, signalling the end of its life. Considering some Ochre stars can live for around 20 years, this disease is sinister and swift for such an important predator.

According to Melissa Miner, one of the MARINe researchers, the Ochre starfish has been defined as a “keystone” species (and was the original animal the term was coined from), meaning the predatory starfish is crucial in controlling the environment around it.

Researchers from the University of Puget Sound explained how Ochre Sea Stars predominantly eat mussels – an animal that can
quickly take over rocky and intertidal habitats – and how this in turn helps the rest of the marine ecosystem. Mussels are competitors for space and may take over the rocky substrate over a large area, but sea stars eat the mussels and allow other animals to use the space.

Sea stars make a tasty snack for gulls and otters, which makes them important prey in a wider ecosystem that is beyond their usual tidal residence.

Melissa Miner explained that “The Ochre Star has a disproportionate influence on the [marine] community because they alter the presence of other species through their actions.

“The ochre sea star has been a species that we have monitored as a network; I would say over 20 years in a lot of areas. Not all of our sites have been monitored for that long, but again it was chosen because it is a key player in the system and can shape what the community looks like.”

How devastating was this disease? How did it come to be?

According to the MARINe researchers’ article the death toll reached a peak in 2013-2015, higher than any other time over the 20 years they have been sampling the stars. At over half of the 39 sites surveyed, they recorded a decline of 99% of adult Ochre Sea Stars between 2000 and 2016.

Miner said, at the moment, it’s too early to tell why the disease epidemic happened in such high numbers, hence the researchers’ interest.

Theories under discussion include a pathogen, which has been named sea star-associated densovirus (SSaDV), or extreme population density. Other speculation has been slightly more sinister, pointing to human involvement, such as rising temperatures accelerating the disease, or pollution working in a similar way.

Although there is disagreement in the marine science world about whether it’s natural or human made, Miner explained that the evidence is too inconclusive to start pointing fingers at global warming.

“The problem is that the scale at which we sample the sea stars doesn’t align well with how you would go about [finding] whether the decline was related to water temperature,” she said, explaining that understanding this disease and it’s causes are just not as simple as that.

“In an ideal world you’d be out there in every low tide, then you would catch when the stars started to get sick, when they started to die. Then you could go back and look and see whether those observations aligned with changes in the water temperature. We just don’t have that level of sampling frequency.”

But this is not an ideal world unfortunately, so all we can do is understand that it’s more complicated than we care to think. But this poses another question…

Where is the funding for environmental disasters like this?

Such environmental disasters can be compared to ones a little bit closer to home. The White Spot disease ailing the Brisbane prawn population in December last year sent the $25 million Australian prawn market plummeting.

It affected farmed and wild animals, such as prawns, crabs, and other crustaceans.

While researchers furiously tried to uncover the beginning of the devastating disease outbreak (unmasking potential human interference with local prawn populations), the Australian government pumped an estimated $20 million into compensation for prawn farmers in the Queensland region.

But there is no such funding for the researchers. In fact, the Australian government disregarded public funded research, done by the University of Sunshine Coast, suggesting the disease started from prawn imports, with Agricultural Minister, Barnaby Joyce, telling the Australian Prawn Farmers Association:

“They [researchers] have come up with a hypothesis that this is a Commonwealth biosecurity issue. There’s no proof of that whatsoever.”

Miner complained that part of the problem with responding to the Sea Star Wasting Disease was funding. “It’s really variable where the funding comes from and I think that’s pretty typical for a long-term monitoring project like this that there just isn’t that continuous funding that’s available to groups that makes it available to do this work [respond to environmental crisis],” she said.

She went on to explain that mostly groups who do this type of research get funded for a certain amount of time to investigate a particular question or proposition.

By the time enough money is gathered to help the situation at hand, such as the SSWD epidemic, the effects of such a devastating environmental issue have already begun to set in, such as increased mussel populations, leaving many rocky environments uninhabitable for other marine creatures.

This is why she argues that access to immediate funding without going through regular grant approval methods (which have long wait times) would be extremely beneficial to the environment.

“You see that sea stars are dying, and you need to get out there and sample them immediately.

“It would be really valuable to have something like [an emergency fund] in place for when these emergency situations
arise. There would be a source of funding for researchers to use in that initial response period … but as far as I know this doesn’t exist anywhere.”

So where are we now?

For now the Ochre Sea Star population has begun to climb back up into stable numbers, with many long-term monitored sites hosting over 300 times as many stars in Spring 2015 as at the start of the epidemic in 2013.

Although it has not recovered entirely, Miner explained to PLoS that she believes current trends show the North-American coastline will most likely see a better return of the Ochre Sea Star population in cooler areas, whereas places like Southern California, which were hit with the most devastating depletion of the starfish, will have much more of a rough time building up the numbers.