Mosquito netting, vacuum power, and bug science
Laura Nielsen for Frontier Scientists –
Vacuuming at home isn’t too edifying. How about vacuuming the Alaska tundra to snag a bag full of bugs? That's an entirely different story. Ashley Asmus, graduate research assistant at the University of Texas at Arlington, is using a huge reverse leaf blower to collect the bugs she'll study. It’s called vacuum sampling.
”It seems like a lot of entomologists have their own version of it. But mine is just a leaf blower with an insect net inserted in the front of it to catch the bugs.” “I’ll sort them usually down to family which is a handy group to characterize the community of insects. Measure them to get some idea of how big they are and how much biomass they contribute.” ~Asmus
Entomologists, scientists who study insects, use a special microscope that’s able to measure a bug’s size digitally. Then, they apply special equations that relate a specific species’ size to its mass.
Besides vacuum sampling, Ashley also uses using pitfall traps and sweep netting to snag Alaskan bugs, all while braving a ferocious cloud of mosquitoes and midges.
”Those are all methods that we are using to track how much bug biomass is available to eat [by predators] such as birds and also what kind of bug community lives on the tundra, especially on different types of tundra habitats.” ~Asmus
Sorting through piles of dead insects wasn’t always on Ashley’s to-do list. Often, science takes people somewhere a little unexpected. So what sparked her passion for bugs?
”I study bugs on the tundra. I used to think I wouldn’t study bugs; I thought maybe I would study birds or something cute like that. And I remember I had an entomology class as an undergraduate. My entomology teacher would make fun of me and ask what bugs those birds were eating as if that was the real, important question. And he turned out to be right.”
“And now he rubs it into my face whenever I go back to see him.” “Because bugs are actually really important. Arthropods in any given system make up a huge proportion of the biomass, the animal biomass of a system (so just what’s there). So they themselves are part of a larger food web that other animals depend upon.” ~Asmus
Insects are essential pollinators – just look at the problems caused by declining honeybee populations, and you’ll get an idea of what an important role they play.
In the Arctic, annually frozen ground called permafrost experiences thaw only in the very top layer of the soil (called the active layer). Tundra thaws enough for lichens and mosses and other shallow-rooted plants to grow. Yet warmer temperatures are thawing out more of the permafrost, leading to a deeper active layer. Thawing permafrost can also result in thermokarst events, tundra failures that lead to landslides, a slippery-slope of decay which releases ancient carbon dioxide and methane into an already-strained atmosphere. Where the active layer has thawed more deeply than normal, plant communities are changing.
”As the permafrost thaws one type of plant, the dwarf birch, is being favored over all of the other types of plants and is crowding out a lot of other plant diversity. And along with that we are seeing a change in the community composition of insects. So an entirely different community of insects is associated with these shrubs that we don’t see in the regular open tundra ... that used to be more dominant before climate change.” ~Asmus
She says: “The dwarf birch wins every time.”
Indeed, many Northern Hemisphere plant species’ ranges are pushing north, growing and thriving more heartily in the temperature regimes which they favor. Insect communities are often tied to the plant species they eat, so bugs – and the birds which eat those bugs – are beginning to be found further north as well.
Insects serve a vital role as prey. They can also serve as an indicator of the health of an ecosystem.
”Biomass is kind of a measure of energy in some ways; we can track not only movements of nutriments in a system but energy in general. Energy that starts with the Sun and is captured by plants or produced by fungi and other stuff like that [is] eventually taken up by animals which eat each other.” “Insects are a great indicator of what’s happening in the environment. Not just whether or not they are there, but what types, can tell you a lot about what’s happening to the plant community or what might happen to the animals that might consume those insects.” ~Asmus
A protein rich food source
While Ashley collects and analyzes bugs, other researchers at Toolik Field Station are studying species of migratory sparrows and longspurs. Small songbirds which migrate to the Arctic every spring to breed rely on the insect population to feed their young. Chicks hatch mid-June, and winter storms begin in August, so chicks need to grow swiftly in order to make the return flight before Arctic winter hits.
Jesse Krause, PhD student, is part of the University of California Davis’ Birds and Seasonality project. He says that the birds come to the Arctic specifically to take advantage of the summertime insect explosion – “This huge arthropod biomass,” which currently tends to peak during the last week of June or the first week in July.
“With warming global temperatures the Arctic is seeing increases in temperature which is greater than anywhere else so we’re interested in how those warmer springs may affect earlier snow melt and with earlier snow melt, you would expect earlier geening and earlier arthropod emergence.”
“We separate bugs out from the vegetation that ultimately comes with it. Then we dry down that biomass and we weigh it. So, we can look across the growing season. When does that peak biomass occur? Because when the eggs hatch the parents are feeding their nestlings almost exclusively on arthropods. And part of that is probably related to the really high growth rates you see in the nestlings. So you really need protein rich food sources.” ~Krause
The scientists look closely into the birds’ diets… by collecting droppings. They collect fecal samples, and then look through them in the lab for pieces of insects: legs, wings, or mandibles. Ashley explains:
”One of the ways you can decipher what an animal is eating is to just physically dissect a fecal pellet. So when we capture birds on the tundra, they usually poop on us at some point. And we carefully collect that poop, freeze it and then later in the lab when you dissect that fecal pellet you can find tiny tiny parts of different insects that aren’t digested.” "[After birds] eat an insect the exoskeleton is left behind for you to look at later. And just based on those pieces of exoskeleton we can get an idea of what types of insects they are eating whether they are beetles or bees or flies.” ~Asmus
She goes on to say that modern molecular methods (i.e. “PCR to sequence the DNA”) performed in the lab can also tell a scientist what the birds are eating, but I’m astonished that she can identify a type of bug based solely off a tiny mandible or leg that’s already traveled a bird’s digestive track.
Spiders, oh my!
I can tell Ashley Asmus is really into studying these six-legged protein packs by the way she talks about spiders, a topic that can make many people squirm.
“Last year it was really fun to see the community change over the course of the season. So, to see the bumble bees and spiders get an early start.” … “Spiders are active in the winter, they live under a thick layer of snow (it is a little bit warmer under there). And they can still forage for food. So right away when the snow melts they have a head start and start mating and reproducing.” ~Asmus
So… full-grown spiders are crawling around all winter under the snowpack?! There’s something I might not mind forgetting.
Still, it’s a fascinating world. And as the Arctic changes rapidly – warming two times faster than any other region of the globe – the scientists who visit Toolik Field Station are witnessing and documenting changes across the Arctic environment, so that we may better understand and forecast the future.
Frontier Scientists: presenting scientific discovery in the Arctic and beyond
- FrontierScientists interviews with the quoted scientists during their 2013 research season at Toolik Field Station