The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
June 9, 2015
Salish Sea, Pacific Northwest
Remember the devastating epidemic that wiped out most seastars along the west coast of North America last year? Called SeaStar Wasting Syndrome (SSWS), the proximate cause was tentatively identified by a team of researchers last fall as a virus, one that has been present in the marine environment for at least 70 years, but which has been killing seastars at an unprecedented rate over the past two years. The spread of infection is exacerbated by warm summer water, but there are probably several factors working together to cause this current extreme event in our rapidly changing marine environment. This epidemic is unusual in that it is geographically widespread, has high mortality, and affects all species of seastars. Research is ongoing and has been greatly assisted by citizen science efforts reporting cases to central clearinghouses, primarily at UC Santa Cruz. I've been making observations at sites around the island where I live in the San Juan archipelago, in the Salish Sea. I am not far from the Washington coast where SSWS was first identified in June 2013.
All of my observations have been at rocky intertidal sites like this, usually on foot but sometimes by kayak. There's one purple Ochre Star (Pisaster ochraceus) on the rock in the foreground - I have to be within arm's reach to see them.
The most common seastar along the west coast is (was) the Ochre Star.
Healthy Pisaster vs. a sick one:
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In this early summer update from the Salish Sea there is bad news but also good news. My report follows, below the fold.
(All photos by me. In Lightbox...click to enlarge)
I'm never able to count ALL seastars at a given site because I can't see far into the water, and seaweed covers much of the rock surface, not to mention logistical limitations like tide, weather and my personal schedule that limit when I go out. But my numbers can be useful for making relative comparisons. Two factors prevented me from making observations over the winter: (1) the tides are very high during daylight hours so I can't see seastars, which are low-intertidal/sub-tidal creatures by their nature, and (2) seastars become inactive in winter, and are more visible now foraging in the upper zone where their preferred prey live (mussels, barnacles and whelks).
The bad news:
1. There are far fewer seastars, comparing the same time of year and sites. Roughly speaking, I'm seeing 10% the usual number of seastars. And the few I have seen are mostly solitary, which can be a problem: since seastars spawn into the water, the chances of fertilization are much higher when a lot of seastars are in close proximity. On the other hand, loner seastars are less likely to pick up a communicable disease.
2. I'm not seeing big numbers of baby seastars, the recruits that are essential in rebuilding these decimated populations. Nor have I seen any seastar larvae in the plankton.
The good news (so far at least...the caveat being that the warm water season has not begun yet, which is when they will face their greatest stress):
1. All the seastars I've seen are healthy. yay! Since most are adults, this means all these individuals survived the disease last summer.
2. I've observed most of the common seastar species this year. SSWS hits all kinds of seastars, so individuals in many populations have survived.
Some other common species I photographed in the last month -
Henricia, the Bloodstar:
Dermasterias, the Leather Star:
Solaster stimpsoni, the Striped Sunstar:
3. I saw some juveniles, at one site.
A baby Leptasterias (6-armed seastar)
and one of two possible baby Pisaster (I didn't pull them out of their hidey holes to be certain)
Researchers at other sites in Washington and California have been seeing large numbers of juveniles. There is a lot of variabilty in recruitment. I believe Ron K has seen juveniles up in Bellingham, to the north of me.
4. The usual prey of Pisaster has not exploded in numbers. This has been the major ecological concern. Pisaster is considered a key factor in rocky marine ecosystems, a predator that keeps other populations in balance.
Pisaster feeds primarily on mussels and barnacles. Since these animals are fixed to their substrate, it's pretty easy to see whether they are being eaten or not. As you can see from these photos of a log resting in the water and a rocky wall, both taken from a kayak when the tide is at approximately 0 feet, there are no mussels below the water level, and dense populations above. To be sure, the tide will rise and cover these mussels, but Pisaster can withstand only short intervals out of the water and will leave prey high in the intertidal alone. Usually they feed somewhat higher than this; perhaps the fewer predators are finding enough to eat lower down.
Other observations
> All the Pisaster I've seen have been hiding under ledges, in cracks, in the shade, even under water. This behavior is more skittish than usual.
Typical 2015:
(Pisaster comes in orange as well as purple)
Typical 2013:
> No seastar larvae in the plankton so far this spring. After quietly building up their gonads all winter, seastars come up near the surface to spawn into the water in spring. If eggs are fertilized, planktonic larvae will drift in surface currents for a month or so feeding on phytoplankton before settling to a surface and taking up seastar life. I have seen sea urchin larvae, which is a good sign. There are reports of urchins - close relatives of seastars - affected by the same pathogen.
Urchin larva and adult urchins:
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What you can do!
If you live on the west coast, or visit there this summer, please consider contributing to the citizen science effort monitoring seastar survival and juvenile recruitment. The Santa Cruz site is easy to navigate for entering data, and includes photo guides to help with identifying healthy/sick seastars and juvenile species.
Raw data in the this box. A key for abbreviations is at the end.
Agate Rock
6/15/14:
P=17, ok
-----> 2015:
5/18/15:
P=4, ok + 2 possible juveniles
L=6, ok + 3 definite juveniles
Hm=2
Richardson dock
6/16/14:
P=10, ok
L=several, ok
7/11/14:
P= 12, 30% sick
H=3, ok
Py=1, ok
8/12/14:
P=1, sick
-----> 2015:
5/20/15:
P=2, ok
H=3, ok
D=1,ok
S=1,ok
Odlin Park boulders
6/18/14:
none
7/13/14:
P=18, 6% sick
H=2, ok
Py=1, ok
-----> 2015:
6/4/15:
P=1, ok
H=1, ok
Landau’s wall@Barlow Bay (E)
6/19/14:
P=24, 20% sick
6/21/14:
P=32, ok
6/29/14:
P=24, 50% sick
7/5/14:
P=10, 50% sick
8/11/14:
P=1, ok
9/17/14:
P=6, ok
-----> 2015:
5/7/15:
P=5, ok
Sinibaldi/Olson wall@Barlow Bay (W)
6/21/14:
P=64, ok
Py=1, ok
7/13/14:
P=40, 20% sick
8/12/14:
none
9/17/14:
none
-----> 2015:
6/5/15:
P=7, ok
Pb=1, ok
Shark Reef
6/29/14:
none
Upright head, both sides ferry dock
7/1/14
P=8
Aleck Bay
7/14/14
P=8, ok
---> 2015
6/6/15
P=1, ok
KEY:
P = Pisaster ochraceus (Ochre Star)
L = Leptasterias hexactis (6-armed Seastar)
H = Henricia leviuscula (Bloodstar)
Hm = Henricia leviuscula (Mottled Bloodstar)
Py = Pycnopodia helianthoides (Sunflower Star)
D = Dermasterias imbricata (Leather Star)
S = Solaster stimpsoni (Striped Sunstar)
Pb = Pisaster brevispinus (Spiny Pink Seastar)
ok = no sign of disease
none = no seastars seen
Some info sites:
Seastars of the Pacific Northwest
Biogeography of Ochre Seastar
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The bucket is now open for your nature observations. What are you seeing or hearing in your natural backyard?
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