Sea Star Wasting Disease Update 2019
Over 20 species of sea stars succumbed to Sea Star Wasting Disease (SSWD) up and down the coast starting 2013. What’s the situation today? Gary Luhm reports.
It’s early August, and we’re paddling the NE Vancouver Island coast at Johnstone Strait. A minus tide allows a slow, intimate exploration of the intertidal, an exploration that only kayakers know. I take advantage of the minus tides to note intertidal changes since the Sea Star Wasting Disease (SSWD) hit the Pacific coast in 2013. It doesn’t look good. I’m disappointed to find very few colorful Ochre and Sunflower stars, and many urchins. Without predation from the carnivorous sunflower stars, here and elsewhere urchin populations have exploded, sometimes creating an “urchin barren” ̶̶̶̶̶ rocks scraped of algae and kelp. And because the herbivorous urchins eat bull kelp, they destroy protective fish habitat and the fisheries suffer. At Johnstone, while I wouldn’t call it barren, a wide swath of rocky intertidal, perhaps five vertical feet, appears scraped clean except for sponges. Large red urchins are everywhere.
Sea Star Wasting Disease was first reported in BC in 2013, and by 2015 had spread up and down the coast from Baja to Alaska. As sea kayakers, many of us directly witnessed sea stars decomposed into mushy goo. Over 20 species of sea stars were affected, including the keystone Ochre Stars (Pisaster ochraceus) . The enormous 24-arm Sunflower Stars took a huge hit. While similar SSWD outbreaks were documented in southern California in the 1970s, ’80s, and ’90s, this most recent epidemic is unprecedented in its extent. And with the sea star demise, coastal near shore life has scrambled. California purple urchin population exploded 60-fold.
Two weeks after Johnstone, another minus tide cycle and we’re paddling Chuckanut Bay near Bellingham. We immediately see ochre sea stars, many purple ones, crammed in rock crevices, and no sign of wasting. Anecdotally, intertidal life here looks back-to-normal, even though it was hit hard in 2014.
In June of 2018, Oregon Public Broadcasting (OPB) reported that a massive sea star baby boom was helping the devastated population to recover. Southern California recovery, however, is poor to spotty. In Northern California, abalone (also kelp eaters) are now scarce and starving, and the fishery was closed in 2018. A bag limit increase on harvesting California urchins supports kelp recovery.
Researchers say the culprit for SSWD could be a viral pathogen, and warm water may contribute, but evidence is inconclusive. One finding is that genetics plays a role, so surviving sea stars may be better prepared for future outbreaks. Additionally, new information came out of BC in 2018. The microbial balance of a sea star has a huge effect on outcomes. Healthy sea, healthy stars. BC researchers have also found a significant interplay of sea otters and sunflower stars with urchin numbers. We’ve known for a long time the keystone role sea otters play. Without the otter, urchin numbers climb and kelp and fisheries suffer. Turns out sunflower stars help maintain balance by eating the smaller urchins that sea otters tend to avoid. The sea is a complex place; we have much to learn.
For more info, have a look at these BC-produced videos: https://vimeo.com/281691144