Today is a "report from the field" by Jonathan Martin, a research associate at Simon Fraser University, who is among other things, an ROV pilot, diver and photographer. His pictures can be found at this Flickr stream here.
Martin has recently sent me a series of images and video that show a massive die off of the sunflower
star, Pycnopodia helianthoides in the waters of British Columbia in 20-50 feet of water.
A picture of the sunflower star in a healthy state is above. Pycnopodia is a prominent member of the Pacific northwest intertidal/subtidal marine fauna. It boasts about 20-25 rays and can get to be quite large (about 2 to 2.5 feet across).
A couple of years ago I wrote about a huge Pycnopodia population explosion in British Columbia waters.
ALL pictures in today's post were provided by Jonathan (except where noted otherwise).
The Evidence: Images & Video
Here's a video transect made by Jonathan
See all that white stuff on the bottom?? Those are decaying, white tissues and ossicles from sunflower stars. You can see the fleshy remains all around the bottoms.
His direct observations (dated August/September 2013):
I just got back from a dive out in West Vancouver though, and there seems to be a huge mortality event of some kind with the animals, where they seem to waste away, 'deflate' a little, and then just... disintegrate. The arms just detach, and the central disc falls apart. It seems to happen rapidly, and not just dead animals undergoing decomposition, as I observed single arms clinging to the rock faces, tube feet still moving, with the skin split, gills flapping in the current. I've seen single animals in the past looking like this, and the first dive this morning I thought it might be crabbers chopping them up and tossing them off the rocks. Then we did our second dive in an area closed to fishing, and in absolutely amazing numbers. The bottom from about 20 to 50 feet was absolutely littered with arms, oral discs, tube feet, gonads and gills, the the extent where it was kind of creepy.More pictures of Pycnopodia in various states of decay..
Partial remains of a disk and white, dead starfish tissues..
What makes this such a concern? OTHER starfish species in completely different lineages also seem to be affected. The sea star predator, Solaster dawsoni was also observed in various states of distress..
Solaster feeds on other starfish and does feed on Pycnopodia, so is there a connection?? Especially with the recent population explosion??
So What's Going On?
So, there were a number of different ideas that buzzed through my head. Again, this is all SPECULATION on my part...
1. Is this related to the population explosion, observed almost 3 years ago?? Could the huge populations from 2010 be suddenly dying off? Famine? Disease? (see below) This would be an unusual (or at least poorly known) phenomena. I've seen Pycnopodia in aquaria live out long lives, so I don't think this is some kind of "natural causes" thing...
2. Could this be a disease? Jonathan has mentioned the ciliate (Protist) parasite which inhabits sea stars in the Pacific Northwest. The ciliate effectively castrates the host, but has never been observed to actually cause much more damage than that. And accounts of the ciliate suggest that it occurs in a very small % of the overall population.
There are accounts of many sea urchins being decimated by various bacterial infections, such as Bald Sea Urchin disease but my skim of the literature suggests that there isn't anything known about similar diseases in sea stars. Most mass-mortalities of seastars have been associated with environmental changes- freshwater from rains, storm and wind, toxicity in the water from geological events and so on...
Could this be related to what has been observed on the East coast with Asterias? See also this report. Where populations of the well-known intertidal starfish (and btw, SAME family as Pycnopodia) have been undergoing population declines for unknown reasons.
|Image by lifeboy252|