What if I told you there was a disease that caused lesions, followed by your limbs literally crawling away from your body, and disintegrating, until your body was a pile of gunk? Pretty dark, no? Well this REAL disease is causing mass mortalities in the sea star community. That’s right, looking at you Patrick. Readers, prepare to familiarize yourselves with “sea star wasting disease”.
There is research happening in the science community as to what might be triggering the sudden and rapid spread of this horror-movie-esque disease. A couple of ideas floating around are that changes in temperature or salinity caused an otherwise dormant virus (or bacteria… or protist…) to start wreaking havoc within the sea star.
We set up three different treatment tanks to see how sea star health was affected over the course of 10 days. One tank was cold (10.9) with salty water (31 ppt), the second had cold and dilute (18 ppt) water, and the third had warm (17.5) and salty water. When we went to observe the stars, we were greeted with a smell that could only mean bad news for our little sea stars. Sure enough, the warm and salty tank was filled with murky water, and had a mushy goop along the bottom. This goop was the remnants of our sea stars. Unfortunately they ALL met a gruesome demise over the weekend. We had better results the other treatments, with 6/10 in the cold and dilute tank, and 9/10 in the cold and salty tank remaining in healthy condition.
What this told us is that in our experiment, high temperatures had a more negative effect on sea stars than low salinities. So perhaps local spikes in water temperatures were more important in triggering sea star wasting disease thank salinity changes, as an otherwise dormant virus was altered or activated in a way to cause mass devastation.
Another interesting trend I noticed between these three conditions was differences in the “movability” of the sea stars. Healthy sea stars, when placed in warm and salty water, were the easiest to pick up and move, while those placed in cold and salty water were the most difficult to pry from the glass tank. Sea stars hold on to substrate using little “suction cups” called tube feet, that function to help them crawl around the ocean, move food towards their mouth, and also BREATHE! Talk about a triple threat. Presumably, poor suction is an indicator of poor health, as these little tube feet aren’t doing their job. Thus, the trend of deteriorating health with increasing temperature persisted.
National Geographic gives a really great introductory video to sea star wasting disease in under four minutes… check out the link below for a more in-depth, visual description!