Mite concerning — Red mass on East Mackey Lake leaves biologists scratching heads

By Dr. David Wartinbee, for the Redoubt Reporter

Alaskans have been seeing red quite a lot lately.

Photos courtesy of Dr. David Wartinbee. A mysterious red mass drifts to the shore of East Mackey Lake on Aug. 4. The mass is thought to be a massive hatch of larval mites, though it’s not known for sure why so many ended up on the surface at the same time.

We recently heard about reddish-colored fungal spores that were found en masse in Kivalina. Then there was red-colored water in Kachemak Bay, similar to a red tide, though not harmful. Apparently it’s now the central Kenai Peninsula’s turn.

I was taxiing my plane to the dock at the northern end of East Mackey Lake on Aug. 4 when I spotted a 100-yard streak, between 10 and 30 feet wide, of bright red stuff in the water. As I tied up the plane, the wind shifted and this fire-engine red material drifted toward the plane.

As an aquatic biologist for 40 years, I had never seen anything like this and was way beyond curious. I took photographs as it approached and got out a jar to collect a small sample. Yes, as a geeky biologist, I almost always carry a few jars for collecting bugs or other interesting things.

The red stuff was on the surface of the water and was made up of very small particles.

A bright-red string tangles around grass in East Mackey Lake on Aug. 4.

They were so small that I could not make out what they were, nor could I tell if they were moving. This red mass seemed to get hung up on grasses and other floating plants, but in places it spread out and completely covered large areas of the water surface. I have seen large masses of yellow spruce pollen floating on lakes and thought, could this be a mass of red pollen grains? I really didn’t know whether I was seeing something that was plant or animal.

I took the sample back to the lab for a look under the microscope. As soon as I did I

One of the mites, seen under 400x magnification.

gasped, “Wow! What the …?” At six times magnification the sample became visible as a seething mass of tiny, bright-red creatures wiggling and crawling around on the surface of the water. There were literally hundreds within the field of view, and they were all moving on top of and around each other. It was similar to how we describe “Brownian Movement” of small molecules.

At first I thought they were insects, since they had six legs, but they really looked like aquatic mites. I showed this mass of moving critters to several folks around the lab and each were astounded when they looked through the eyepieces. Dr. Paula Martin, an aquatic biologist who is an administrator at Kenai Peninsula College, came to see the mass and had a very similar reaction, “Wow!” She had never seen anything like this either. Dr. Martin was fairly certain that some young mites have only six legs, so perhaps this was a huge mass of larval mites.

We had both seen aquatic mites in various habitats, but nothing like this huge mass —

A mass of mites crowd a sample jar, seen under 6x magnification. The dark creature to the right is a zooplankter. Each of the mites are about one-tenth of a millimeter wide.

literally millions upon millions of individuals. Mites are often found as parasites on some aquatic insects, or free-living mites can be found feeding on detritus on the lake bottom. We both wondered how this congregation occurred, and why? What happened to cause this amazing event? What were these mites and what role did they play in the community?

I started researching mites and sent out an email with pictures and a description of the situation to researchers in the United States and Canada. I asked for possible identifications and explanations of what we were seeing. Several of these researchers wrote back immediately and were as curious as I was about the huge mass. Apparently, they have no records of such a massive flotilla of larval mites. This was an unusual event for all of us.

Dr. Heather Proctor, from the University of Alberta, believes the mites are in the family Eylaidae, perhaps within the genus Eylais. These mites are particularly good at reproducing, and female adult mites can produce around a thousand eggs each. If lots of females laid their eggs and they all hatched synchronously, we could conceivably have a huge event the likes of which I witnessed. And if the winds were just right, the mass of newly hatched mites could have been gently blown into a massive congregation.

One other piece of this puzzle is why would the mites be on the surface of the water, since they are normally found closer to the bottom? Dr. Proctor tells me that these larval mites often find their host by waiting for a particular aquatic insect to come to the surface for air. Then the mites hop on-board and become tiny parasites on the hapless insect.

The Eylais genera of mites favor insects like the Corixidae, commonly called water boatmen, and East Mackey Lake has large number of them swimming just below the surface. She commented that any Corixid coming to the surface within this mass probably had “a very bad day.”

Several hours after seeing and photographing this mass of mites, I returned to the site to show the mass to Kenai National Wildlife Refuge entomologist Matt Bowser. During that time gap there had been a couple hours of steady rain and constant breezes. The mass was gone. We were able to collect a few smaller, bright-red floating collections of mites, but the large blanketing mass had apparently dissipated.

I still don’t know definitively the species identity and can only speculate about why this event occurred. The researchers I contacted have asked to use some of these pictures in an upcoming book, since this is the first time such a large mass of larval mites has been documented. I have freely shared the images and have also sent them a number of specimens for their examination and, hopefully, identification, as it is often very difficult to identify mite species when they are in their larval stages. I will also send a number of specimens and copies of the pictures to the Entomological Museum at the University of Alaska Fairbanks.

Like the other red-colored spores or red-colored alga that have been seen elsewhere, the question always comes up — are these dangerous? To the best of my knowledge, these mites do not present a danger to anyone around the lake. Mites tend to be fairly specific as to the insects they choose as hosts and the tiny invertebrates upon which they feed. Humans most likely don’t fall into their “acceptable” category. If they could possibly parasitize us, perhaps like chiggers embedding into the skin, we surely would have heard about these mites a long time ago.

I spoke with someone who lives on East Mackey Lake and have been told that

Photo by Matt Bowser, courtesy of Dr. David Wartinbee. Dr. David Wartinbee collects samples of red particles on the surface of East Mackey Lake. The red streaks turned out to be a massive hatch of mites.

residents have seen smaller, bright red-colored masses drifting on the lake surface in the past. They have indicated that the distinctly red masses previously seemed to stay mostly along the edges of the lake and were short-lived.

So perhaps this event is somewhat common, but has simply never been documented on such a grand scale. If you live along a lake or have ever seen anything like this before, I sure would like to hear about it.

David Wartinbee, Ph.D, J.D., is a biology professor at Kenai Peninsula College’s Kenai River Campus. He is writing a series of columns on the ecology of the Kenai River and Cook Inlet watershed. He can be reached at


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Filed under ecology, insects, science of the seasons

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