It’s a good time to check in on the rocky intertidal. All along the west coast, sea star wasting syndrome has, to varying degrees, reduced Pisaster ochraceus, a potent predator and organizing force in rocky intertidal communities. Generations of intertidal ecologists, students, fisherpeople and other harvesters, tide poolers, and beachcombers have grown to count on the familiar rocky intertidal progression from red algal turf on the low side, to a zone of kelp right around mean lower low water, to mussels and barnacles on the high side. We now understand that predation, competition and disturbance, along with a bunch of other factors, help maintain these zones and characteristic intertidal communities.
This photo appeared previously in Sea Stars and Sand Dollars. It was taken in April, 2013 and it shows the progression of lower intertidal zones visible from shore at very low tide. These are the zones we might expect to see changes in if keystone species, like Pisaster, are taken out of commission, as they presumably have been, for the last couple of years under sea star wasting syndrome. If this bout of sea star wasting syndrome sustains itself, it could be a grand natural experiment – a redo of Paine’s and other experimental works, on a fantastic scale. I’m excited to see how things are going to unfold. So are a lot of other people, and lots of ecological studies, new and ongoing, and a bunch of new collaborations are presently underway. I haven’t heard many reports of new ecological results yet, but they’ll be coming out soon because things happen quickly in the rocky intertidal. In the mean time, by way of organizing a couple years worth of my own fairly random and unorganized thoughts about wasting syndrome, here is a little recent history from a single site in northern Oregon, aided by a few, mostly add hoc, comparative photos to stimulate the imagination while researchers discover, measure, and describe the ecological consequences of sea star reductions.
Some Recent History
In early 2013, only a few people were thinking about sea star wasting syndrome. This photo, from spring of that year, gives a sense of abundant, seemingly flourishing, Pisaster ochraceus.
In midsummer of 2013, Pisaster were abundant and healthy looking, as in the top photo. What about the individual in the bottom photo? A healthy spawner – or diseased and wasting? Check out the photos on the Pacific Rocky Intertidal Monitoring Site and decide for yourself.
In the spring of 2014, the ebb revealed an orgiastic scene. Pretty much every nook and cranny was a sight of purple and orange. But trouble was brewing.
These look like they could be wasting syndrome symptoms. There were a few other examples of poor looking Pisater, but they were in the minority.
By June 2014, there were still plenty of Pisaster, but they were less abundant, apparently, than just a month earlier. The unmistakeable signature of the wasting syndrome wasn’t hard to find.
April 20, 2015
After a long dark winter I couldn’t wait to find out how Pisaster was doing. Less than a month ago, in April, I was finally able to go see for myself. I found plenty of Pisaster and a most of them were looking good; but not all of them.
I gave at least a glance to lots of Pisaster and this one was the only one showing obvious symptoms, presumably wasting symptoms. I didn’t see any baby Pisaster, but I was concentrating on adult condition and abundance. A few small individuals, about 3 inches across, did catch my eye however.
That’s pretty much the progression of the most recent bout of sea star wasting syndrome, from April 2013, up to April 2015, at a single northern Oregon site. It seems consistent with what I’ve seen at other rocky areas in northern Oregon. I think I’m safe saying the wasting syndrome is still killing adult Pisaster, and that a good proportion of survivors to date seem, superficially, to be in pretty good shape. I also believe it’s safe to say that the syndrome has noticeably knocked back the intertidal abundance of Pisaster ochreaceus compared to the spring of 2013 – but by how much? I think the following sequence of photos gives a realistic impression of relative abundance over time.
With no counts I can’t estimate abundance, but maybe I can take a stab at relative abundance. To do this, I’ll take advantage of my natural tendency to notice and photograph dense accumulations of intertidal organisms. It’s a good bet I didn’t leave the water on April 26, 2013 without a shot of the most gaudy display of Pisaster I saw. By June 2014 thoughts of the wasting syndrome and comparative abundance were unavoidable, so I think I got a good shot of the biggest, densest aggregation I saw. By low tide on April 20, 2015, I was definitely planning for a maximum density shot, for comparative purposes. Since they’re all I’ve got, I’ll use counts in the photos above to estimate relative abundance. Accounting for scale and image quality, I estimate there are about a third as many adult Pisaster now, as there were back in the spring of 2013. I guess you could say there are some serious methodological shortcomings here, and I agree, but even so, the estimate seems in line with the general impression I get just wandering around on the rocks. By any measure, there are still a lot of Pisaster in the intertidal, but there has been a a big drop off in abundance. I can’t wait to find out if the drop off is big enough to have ecological consequences, and to learn whether the drop off is going to grow, or shrink in the future.
When I’m poking around the rocky intertidal, I’m mostly just taking photos and trying to identify marine algae and invertebrates. Now, with wasting syndrome, I’m curious to find out if I’m going to see any changes. Will this diverse ecosystem become more homogeneous – a world of mussels, perhaps? Will I start to see some changes in abundance, or maybe even some different species?
The tide pool above has seen little starfish action over the last year. Do you see any changes? At small scales like this, it will be interesting to see who moves out and who moves in under sea star wasting syndrome. Somebody has moved in, it seems.
See that purple, spiny creature just above and to the right of center? That’s the purple sea urchin, Strongylocentrotus purpuratus. I pretty much never saw them on the rocks featured here, until this year. An effect of wasting syndrome, or just a coincidence? If it’s an effect of the wasting syndrome, is it a Pisaster effect? In this neck of the woods people always say the sunflower star, Pycnopodia helianthoides is an urchin predator. If Pycnopodia have been reduced by wasting syndrome, as most accounts suggest, then maybe what I’m seeing is a result of predator-prey relations in the subtidal, where Pycnopodia rules.
On scales bigger than the tide pool, what can we expect under a sustained period of starfish suppression?
If wasting syndrome runs it’s course quickly, it’s effects will probably be subtle and short-lived. On the other hand, if Pisaster and other starfish are reduced for a long time, innumerable questions arise. Will the mussel zone creep down? What’s in store for the red algal turf? What species replacements and homogenization might occur? If, after a period of reduction, Pisaster returns, will the familiar zones return, or will the ecosystem be altered forever? I couldn’t be more excited about the months ahead. In each month from now ’til August there will be some great early morning low tides and ample opportunity to learn a whole lot about the course of wasting syndrome and how Pisaster and the communities that make up the familiar intertidal zones respond.
If you love Pisaster and all echinoderms, and think perhaps radial symmetry is for you, check out Christopher Mah’s The Echinoblog.
If you like all the zonation and keystone species stuff, here are a few foundational references:
Dayton, P. K. 1971. Competition, disturbance, and community organization: the provision and subsequent utilization of space in a rocky intertidal community. Ecological Monographs, 41 (4): 351-389.
Menge, B. A., E. L. Berlow, C. A. Blanchette, S. A. Navarrete, and S. B. Yamada. 1994. The keystone species concept: variation in interaction strength in a rocky intertidal habitat. Ecological Monographs 64 (3): 249-286.
Paine, R. T. 1966. Food web complexity and species diversity. The American Naturalist, 100 (910): 65-75.
Ricketts, E. W. and J. Calvin. 1968. Between Pacific Tides. 4th ed., revised by J. W. Hedgpeth. Stanford University Press.