Chironomids Give a Whole New Meaning to the Phrase ‘Life is Short’
Contact: Joe Carr at (207) 581-3571
ORONO — Commonly known as midge flies, chironomids begin their lives as larvae in lake sediment. It’s cozy down there — a nice place to build a home, or a tube as the case may be. As they grow, they shed their skin four times, then pupate. All at once, they emerge as a swarm of adults, mate, lay eggs and die.
Their entire adult lives take place over the course of a few days. But the lessons they can teach us about climate change endure, according to UMaine researcher Ann Dieffenbacher-Krall. She has spent the last several years extracting and classifying chironomid head capsules — the only part of the insect that preserves — from cores of lake sediment in New Zealand.
“We’re using them as a thermometer, basically,” Dieffenbacher-Krall says.
This thermometer will help researchers determine what was going on in the Southern Hemisphere at the end of the last ice age. In the northern hemisphere, ice core samples have shown extremely abrupt climate change — temperatures rose 7 degrees Celsius over a 10-year period; with global warming, the rate is a degree or two over 50 years.
“Did this occur down there or not? Was it focused on the North Atlantic or was it a climate event for the whole world?” Dieffenbacher-Krall asks. “If we know this, it can give us clues about what the cause might have been.”
And these insect remains — each as small as a speck of dust — may hold the key. Different types of chironomids exist under different ecological conditions, but the dominant variable is a lake’s mean summer temperature. Comparing chironomid data with pollen-based studies of temperature change, Dieffenbacher-Krall and her colleagues George Denton of UMaine’s Climate Change Institute and Marcus Vandergoes, who splits his time between UMaine and Wellington, New Zealand, have painted a more complete picture of climate change during the Lateglacial period. Their findings, published in Quaternary Science Reviews, indicate stronger seasonality, which could in turn have broader implications for understanding differences between proxy records for abrupt climate change.