Even though we don’t know yet what’s causing the sea star wasting syndrome, we do know that we can expect to see changes in the ecosystem as a result. Laura Borden, research diver and analyst at the Aquarium, is starting her master’s research at the University of British Columbia on the effects of sea star wasting on sea urchin numbers and the threats to juvenile spot prawns (Pandalus platyceros).
Laura says it’s all about the cascade effect – a chain of events that alter the balance of the ecosystem at each trophic level. Like dominos falling one on top of the other, one variable affects the next and so on.
The sunflower star (Pycnopodia helianthoides) is a top predator that eats almost anything in its path, including green sea urchins (Strongylocentrotus droebachiensis). But this sea star species was the hardest hit last fall when the outbreak first occurred, meaning that its population has greatly diminished. Without the sunflower stars to keep the sea urchins in check (mostly greens but some reds too), the urchin population has exploded. Laura has seen thousands of them congregating on different reef sites in Howe Sound.
This brings us to the next “domino.” The sea urchins eat fringed sea colander kelp (Agarum fimbriatum) beds, which provide habitat for juvenile spot prawns. These spot prawns rely on the kelp for shelter and food. So the question is… what is going to happen to the spot prawns when the kelp beds disappear? And in addition, can these kelp-less sea urchin “barrens” ever recover after losing the kelp and the other animals that rely on it?
The cascade effect has been studied before in ecosystems devoid of sea otters, but this is the first time it’s being looked at in the context of the sea star wasting syndrome.
This research will most likely take years of meticulous study but the results will help paint a more holistic picture of the consequences of the sea star wasting syndrome. In addition, the findings may yield some useful info for the spot prawn fishery. Laura says ultimately, “It’s all about balance in the ecosystem.”
Have you seen anything unusual regarding the sea star wasting syndrome? Submit your data here and help contribute to the knowledge the researchers are gaining on the phenomenon.
Written by Karen Horak, writer-editor, content and digital experience at the Vancouver Aquarium.