The starfish in this picture may or may not still be alive (my guess is not), but it looks very much like a starfish in the early stages of Sea Star Wasting Syndrome (SSWS), minus a few legs. (It isn’t sick – I photographed it at Long Beach a few years ago – and it is actually an invasive species on South Africa’s coast.) Sea stars on the Pacific coast of North America began sickening – suppurating and disintegrating – in mid-2013, and scientists have been scrambling to find the cause. Initially it was not clear what was causing the sea stars to die in such grisly ways: pollution, warming oceans, large storms and other possibilities were considered. The clue that told scientists that the cause was “microscopic and biological” (in the words of National Geographic Phenomena blogger Ed Yong, who covers the subject with admirable clarity) was that starfish in aquaria, who were bathed in water pumped from the ocean and filtered, were also dying.
Yong’s post explains how scientists isolated the virus (a process involving blending, filtering, and genetic sequencing), and what scientists are hoping to learn from the work they have done on this subject. Potential parallels between SSWS and viruses that periodically flare up in human populations (Ebola being a recent example) are interesting.
At The Verge, Elizabeth Lopatto writes in more detail about SSWS, its discovery, and consequences. She points out that sea stars are a “keystone species”, and that
Keystone species help maintain an ecosystem by eating quickly-reproducing prey species like urchins and mussels — keeping populations low. Without the sea stars, the urchin population explodes; bad news for the kelp forests and everything in them. Giant kelp can grow to 150 feet underwater at a speed of two feet a day, but their weaknesses are their holdfasts, which are sort of like tree roots. The holdfasts are home to brittle stars, prawns and snails, among other creatures. Urchins like to eat the kelp holdfasts. Without them, the rest of the kelp drifts off in the tides. In this way, urchins can devour forests, which, higher up, are also home to fish, including several types of commercially-important rockfish, according to the National Oceanic and Atmospheric Administration.
Lopatto’s article is an excellent read – find it here.
(As an aside, the ocean is full – full to the gills – of viruses. This was revealed to me by the Palumbis in The Extreme Life of the Sea.)
