Midge Madness!

Midge madness?

Yes, and Briggs beckons.

"Midge madness" will occur from 12:10 to 1 p.m. Wednesday, Feb. 25 in 122 Briggs Hall on the University of California, Davis, campus.

That's when Claudio Gratton of the Department of Entomology, University of Wisconsin, Madison, will discuss "Midge Madness! Quantifying Linkages Between Lake and Land" during the eighth of  10 winter seminars sponsored by the UC Davis Department of Entomology.

You've probably heard of the billions of midges--small two-winged flies--that swarm periodically at Lake Myvatn, Iceland. An article published last March in Science Daily indicated that at their peak, "it is difficult to breathe without inhaling the bugs, which hatch and emerge from the lake in blizzard-like proportions. After their short adult life, their carcasses blanket the lake, and the dead flies confer so much nutrient on the surrounding landscape that the enhanced productivity can be measured by Earth-observing satellites."

Enter Claudio Gratton, who studies food web ecology, insect-plant-virus interactions, herbivore-natural enemy interactions, invasive species, biological control, and soil food webs. "Recent empirical and theoretical models," he says, "indicate that the dynamics within food webs are often influenced by resources coming from outside of the focal food web, also termed a 'spatial subsidy.' "

Gratton describes Lake Mývatn as "a eutrophic lake in Northern Iceland with an exceptional natural phenomenon of large-scale chironomid midge (aquatic insect) outbreaks that occur every 5-7 years. The densities increase over four orders of magnitude."

By the way, Lake Myvatn means "midge lake" in Icelandic.

"We used this lake and the surrounding landscape to examine the effect that large-scale spatial subsidies have on terrestrial arthropod food webs," said Gratton, who received his doctorate in entomology from UC Berkeley in 1997.   "Our studies have shown that by moving from lake onto land, the midges act as two types of subsidies."

"First, they can transfer as much as 70 kg N and 10 kg P ha^-1 yr^-1 to a 100-200m wide area surrounding the lake, resulting in increased plant quality, biomass and increased detritivore and herbivore abundance."

"Second, they subsidize the food base of the natural enemies (mainly spiders) on the terrestrial shoreline.  As a result, food web interactions on land are significantly affected by the adjacent lake ecosystem, effects that have the potential to propagate over the long-term, even after midge abundances subside."

Want to learn more about the mighty midges of Myvatn? Attend Gratton's presentation next Wednesday. UC Davis Department of Entomology hosts are Peter Epanchin of the Graduate Group in Ecology (he's in professor Sharon Lawler's lab), and professor and insect ecologist Jay Rosenheim.