Researchers created a history of changing midge communities for six remote mountain lakes in the western United States. Midges, which resemble mosquitoes but usually don't bite, can live nearly anywhere in the world where there is fresh water.
The insect remains revealed a dramatic shift in the types of midges inhabiting these lakes in the last three decades, said David Porinchu, the study's lead author and an assistant professor of geography at Ohio State University.
“Climate change has had an overriding influence on the composition of the midge communities within these lakes,” he said. “The data suggest that the rate of warming seen in the last two decades is greater than any other time in the previous century.”
The data suggest that, starting around 25 years ago, warmer-water midges began to edge out cooler-water midge species around these remote lakes.
“People would like to believe that these mountainous environments may be immune to climate change, but these are some of the first areas to feel the impact of warmer temperatures,” Porinchu said.
He and his colleagues presented their findings December 15 in San Francisco at the annual meeting of the American Geophysical Union.
The researchers gathered sediment from six small lakes in the Great Basin of the western United States – a vast watershed bounded roughly by the Sierra Nevada and Rocky Mountain ranges. Since the lakes are accessible only by foot trail, the researchers carried in an inflatable raft during the summer months in order to collect sediment samples from the middle of the lakes. The lakes range from 8.2 feet (2.5 meters) to 34.5 feet (10.5 meters) deep.
The scientists collected sediment in cylindrical plastic tubes, gathering several samples from each lake. They didn't need much sediment – just four inches (10 cm) of lake-bottom residue can represent nearly 100 years' worth of sedimentation, Porinchu said.
“The amount of sediment that trickles out of the water column to the bottom of these lakes every year is so low because these lakes are at such high elevations – few, if any, trees grow at these elevations,” he said. “There just isn't much material entering the lakes.”
Once they were back in the laboratory, the researchers sliced the sediment cores into thin slivers about 0.2 inches (0.5 cm) thick. Each sliver represents a five or 10-year span, Porinchu said. They calculated the age of single sediment layers by using lead-210, an isotope of lead that decays at a constant rate and, therefore, can serve as a chronological aid.
Using a microscope, the researchers then searched the sediment for larval remains of the midges. Specifically, they were looking for larval head capsules, which are made of a hard, semi-transparent material called chitin. These head capsules become embedded in sediment once they are shed. Chitin, also a component of insect exoskeletons and the shells of crustaceans, doesn't readily degrade in the sediment of these lakes.
The researchers determined the type of midges that lived in the lakes based on specific variations in certain head capsule structures, such as differences in the number, size, shape and orientation of teeth.
“In the upper layers of most of the sediment samples – those representing the last 25 to 30 years – we see head capsules from midges that normally thrive in slightly warmer water temperatures,” Porinchu said. “And the cooler-water midges have nearly, or completely, disappeared.”
Surface water temperatures in these lakes have risen anywhere from 0.5 to 1 degree since the 1980s.
“Although that doesn't seem to be a huge increase, just a slight fluctuation in water temperatures can significantly affect the rate of egg and larval development,” Porinchu said.
And the majority of midge species living in these six lakes in the last 30 years thrive in temperatures ranging from 58.8 to 60 degrees F (14.9 to 15.6C), while cooler-water midges prefer temperatures in the 57 to 58.1F (13.9 to 14.5C) range.
“Above-average surface water temperatures typified the late 20th century in all of the lakes that we studied,” Porinchu said. “It's clearly an indication that something is happening that is already affecting aquatic ecosystems in these fragile, high-elevation lakes.”
Porinchu conducted the study with researchers from the National University of Ireland in Galway; the University of California, Los Angeles; the University of Western Ontario in London, Ontario; and Middlebury College in Middlebury, Vt.
David Porinchu | EurekAlert!
Six-decade-old space mystery solved with shoebox-sized satellite called a CubeSat
15.12.2017 | National Science Foundation
NSF-funded researchers find that ice sheet is dynamic and has repeatedly grown and shrunk
15.12.2017 | National Science Foundation
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences