Now You See Me, Now You Don’t



Wondering what the icky goo is in the picture above? What if I told you that was a sea star, would you believe me? I didn’t think you would. The sea stars we’ve seen basking in the sun along the coast of beaches are soon to become a rare sight. You might be wondering what does goo have to do with sea stars disappearing. But the connection is stronger than you think. The goo is actually a wasted sea star. And no I don’t mean ‘wasted’ as in a sea star that partied too hard. Rather it refers to sea stars that are infected by the sea star wasting syndrome. Once infected the sea stars begin to lose their limbs and slowly disintegrate into mush like in the picture above.

 Next, you might ask what is causing this tragedy. The spiralling down of these sea stars is due to a virus. This deadly virus has caused many sea star populations to decline such as the Pisaster ochraceus and Pycnopodia helianthoides. As of now, there is no stopping this virus as it is spreading its range, from Alaska to California.

So, what causes this outbreak? Some have said that temperature is key as it facilitates the virus. Others, say it is salinity as lower levels of salinity impair the sea star immune system, making them more likely to be affected. In our Biology 326 lab, we decided take to matters into our own hands and investigated the effect of temperature and salinity on sea stars. For our experiments, we used healthy sea stars, Evasterias troschelii, which had been collected from Stanley Park in January.

In our experiment, we exposed the sea star to lower salinity levels and warmer temperatures and then observed their behaviour. For instance, we noticed how long it took the sea star to turn itself over completely when flipped and how long it took the sea star to find a mussel in the tank.


Evasterias troschelii flipping over. (Photo Credit: Manjot Sandhu)

In the first part, we tested the effect of salinity. One sea star was placed in the two tanks. Although, we would predict that the sea stars in the higher salinity tank will move faster, not much of a difference was found between the two tanks.

When testing the effect of temperature, we placed a sea star in the warmer tank and another sear star in the cooler tank.  Once again, we didn’t see a difference between the two.

It seems our sea stars did not like us much as they did not want to talk to us. They gave us no clues to what might be affecting them. It is possible that the climate change may be a game changer in the way sea stars react to the ever changing environment.

Here’s a link to a larger scale study that seems to have had better luck in communicating with the sea stars.


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