Light, sweet, orange goo crude.

Last fall the small Alaskan coastal village of Kivalina was inundated by a mysterious orange "goo"(click for photo). Locals and others suspected a toxic algal bloom (see here for image), or perhaps some sort of chemical release, or millions of microscopic "crustacean eggs".

Yet just a month later the mystery substance was identified as none other than a plant-parasitic fungus called a rust -- completely harmless to humans and aquatic life, and probably not bad plankton food. I covered this at length in my follow-up post. But the mystery remained: what plant disease epidemic had this rust come from? And to produce a bloom of spores that huge, how could no one have noticed?

Now, the identity of the rust has been revealed at last. It is the Spruce-Labrador Tea Needle Rust, Chrysomyxa ledicola, a parasite of both spruce trees and a rhododendron -- a flowering woody shrub common to conifer understories the world over -- called Labrador Tea. I had never heard of a rhododendron you could drink, but my old friend, mycologist, and ex-pat Canadian Kathie Hodge at Cornell assured me it makes quite a delicious tea. Apparently, C. ledicola agrees with her Labrador -Tea deliciousness assessment.

A scanning electron micrograph of unidentified rust spores from Alaska. Note the gorgeous projections that look like they've been turned on a lathe.

The USDA Forest Service and the Canadian Forest Service performed the identification and announced it in early February, since plant parasites are not exactly NOAA's bag. They identified the Kivalina goo as urediniospores, the form of the rust that is produced only on Labrador Tea (see my post from last fall for a refresher on the exciting and bewildering variety of rust spores), that may be where the epidemic occurred.

Spruce-Labrador Tea Rust on Labrador Tea. Notice the fungus spore settled on a leaf, grew outward in a concentric circle, and has made its fruiting bodies at the edge of the piece of leaf it ate. Natural Resources Canada, Canadian Forestry Service. Click image for link.

Perhaps since rhododendrons are not exactly -- how do they put it? -- economically important, it's not out of the realm of possibility no one noticed they were eaten up with rust in remote northern Alaska last year.

But to produce that many spores, I'm slightly skeptical that what the scientists were looking at weren't the spores produced on spruce, which as giant trees are probably sitting on more biomass per unit area (and thus rust-producing capacity) up there.

C. ledicola aecia (spore chambers) on spruce needles. Natural Resources Canada, Canadian Forestry Service. Click image for link.

Spruce-Labrador Tea Rust aeciospores bursting, Alien-style, from a spruce needle. Natural Resources Canada, Canadian Forestry Service. Click for link.

According to Kathie, the spores produced on each plant look similar. But in either case, to get quantities of spores massive enough to turn Kivalina's port orange, there had to be one heck of a blistering rust epidemic going on last summer. How did no one notice? Perhaps someone did.

A light micrograph closeup of the Kivalina rust spores. Bar at lower right is 50 micrometers in 10 micrometer increments. NOAA, Courtesy Steve Morton

Last October, David Wartinbee, a professor of aquatic biology at Kenai Peninsula College in Alaska's south-central Kenai Peninsula, emailed me to say he'd seen something strange, and wondered if it might be the same thing that hit Kivalina. Though his neck of the woods is over 600 miles southeast from Kivalina as the snow goose flies, it's not inconceivable they could be one in the same in a place so far north.

In early September, Wartinbee traveled 70 miles west to a place called the Twin Lakes by float plane (reputedly the SUV of Alaska). He saw an orange film on the water, and the spruce needles on nearby trees were clearly poxed with something.

Orange film on upper Twin Lake. Courtesy David Wartinbee; used with permission.

Those needles aren't supposed to be brown. David Wartinbee; used with permission.

At the Lower Twin Lake, it was the same story.

Isn't Alaska (in summer) beautiful? But note unhappy tree in foreground. David Wartinbee; used with permission.

Strong circumstantial evidence of Chrysomyxa ledicola at Lower Twin Lake. Note stringy projections from dead needles. David Wartinbee; used with permission.

Wartinbee wrote to me in October:

During this visit to Upper Twin Lakes, and also during a couple previous visits in August, I noticed that almost every white spruce tree showed infestations of what I believe was a rust or some fungal disease. The rust, or whatever was causing the infestation, had caused almost all the tips of the branches to become light orange/yellow. These tips were obviously being infected with something and there were small projections coming out from many of the impacted needles. I took a number of pictures of these limb tips and was surprised how wide spread this infection really was. A couple employees of the Lake Clark National Park ( surrounds Twin Lakes ) told me that white spruce everywhere in the surrounding valleys seemed to be infected.

So, I believe that the mass of spores may have come from a huge terrestrial infection of spruce trees. Local winds may have then concentrated the spores into a visible mass on the lake. I am betting that this is the reason Kivalina experienced a similar appearance of the orange mass on their shores.

How prescient he was! If you compare the needles in this photo with the needles in Figs. 29a and 29b here infected with Spruce-Labrador Tea Rust, or the photos of infected needles above, I think you'll agree there's a striking similarity, right down to the "small projections" on the needles. Strong circumstantial evidence.

So perhaps it was the spruces near Kivalina, and not the Labrador Tea, that produced Kivalina's goo. NOAA noted that both black spruce and Labrador tea are common along the rivers in the greater Kivalina area, such as it is. Regardless, right about now, I bet the residents of that fine burg are wishing for the return of orange goo sooner rather than later. It's a long, dark winter at 67N.