Glacial stream insect may tolerate warmer waters

Date:
July 27, 2020
Source:
Washington State University
Summary:
An endangered aquatic insect that lives in icy streams fed by
glaciers might not mind if the water grows warmer due to climate. A
new study found that mountain stoneflies can tolerate warmer water
temperatures at least temporarily. In fact, they might even be
stressed in their current extremely cold environments.



FULL STORY ==========================================================================
An endangered aquatic insect that lives in icy streams fed by glaciers
might not mind if the water grows warmer due to climate change.


==========================================================================
A study published in Global Change Biology on July 22 found that
mountain stoneflies can tolerate warmer water temperatures at least temporarily. In fact, they might even be stressed in their current
extremely cold environments.

While the study goes against the prevailing theory that rising water temperatures will be devastating for the glacial stream insects, Scott Hotaling, co-lead author on the study, said this does not mean that
global warming will be a win for mountain stoneflies.

"These species are likely still very much in peril," said Hotaling,
a Washington State University post-doctoral researcher. "They live
in these extreme areas for a reason. The problem is we don't fully
understand what that reason is yet. The threats from warming and the
loss of glaciers are likely more complicated, and potentially, it is not
about physical factors. It might be about ecological factors." In the
study, Hotaling and his colleagues tested the thermal tolerance levels
of several species of mountain stoneflies found in the Rocky Mountains, including Lednia tumana, which was listed under the U.S. Endangered
Species Act in November 2019 due to the rapid loss of its glacial habitat.

The researchers collected larval specimens of the stoneflies from streams
in Glacier and Grand Teton national parks. They then subjected some of
the flies to increasingly warmer water temperatures.



==========================================================================
All of the species had a maximum tolerance of more than 20 degrees Celsius
(68 Fahrenheit), which is well above their normal range of below 10
degrees Celsius (50 Fahrenheit).

They found that the stoneflies that experienced warmer temperatures
expressed "heat shock proteins" at the cellular level. These proteins
are named because they were first described in relation to exposure to
high temperatures, but heat shock proteins are also related to other
stressful events including exposure to cold.

In this study, the researchers found these same proteins were expressed
not only by stoneflies exposed to heat but also by those that were held
at 3 degrees Celsius (37.4 Fahrenheit), a similar temperature to their
normal conditions, indicating mountain stoneflies might be stressed in
their usual cold temperature environments.

The study's findings raise a lot of questions, including why these insects
are not found in warmer waters currently, said co-lead author Alisha Shah,
a post- doctoral researcher from University of Montana.

"It is possible that these mountain stoneflies are just bad competitors,
and they are pushed up to these higher elevations by stronger competitors
who prefer somewhat warmer temperatures," said Shah.

The researchers tested the flies' ability to tolerate short-term spikes of temperature, imitating what might happen to a stream on a hot summer day.

Hotaling and Shah are now investigating how stoneflies respond to living
in warmer water for longer periods. So far, the stonefly nymphs appear
to develop faster. Shah said it was hard to tell yet if that was good or
bad for the stoneflies overall since faster development might mean they
have more deformities or fewer eggs. Hotaling and Shah are investigating
these variables in a race to better understand the cold communities that
live downstream of glaciers before they disappear.

"We're stuck between having so little knowledge about the ecology and physiology of what lives on or downstream of glaciers and having so
little time," Hotaling said. "These are some of the most rapidly changing places on the planet, so the time we have to understand them is ticking
by very quickly."

========================================================================== Story Source: Materials provided by Washington_State_University. Original written by Sara Zaske. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Scott Hotaling, Alisha A. Shah, Kerry L. McGowan, Lusha M. Tronstad,
J.

Joseph Giersch, Debra S. Finn, H. Arthur Woods, Michael E. Dillon,
Joanna L. Kelley. Mountain stoneflies may tolerate warming streams:
evidence from organismal physiology and gene expression. Global
Change Biology, 2020; DOI: 10.1111/gcb.15294 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200727114720.htm

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