Microbes, algae, freshwater plants and
animals are all part of an active ecosystem and take their nourishment
from and return waste to the atmosphere. Healthy plants take carbon
dioxide from the atmosphere with photosynthesis. Most of the methane in
freshwater systems is produced by an important group of microbes called
Archaea that live in waterlogged, oxygen-free sediments and play an
important role in decay.
Plant uptake of carbon dioxide is affected
by temperature, and so is microbial methane production. Respiration also
releases carbon dioxide. The questions the researchers set out to answer
were: which gas is more likely to be released in greater quantities as
temperatures rise? And is the outcome the same whether they examine the
Archaea only, or all the microbes in an ecosystem, or the entire package
of submerged freshwater life?
More heat, more methane
The answer is, the scientists say, that
methane emissions go up with the mercury, and that the ratio of methane
to carbon dioxide also goes up in step with temperature. And the result
is the same whether you consider the microbes or the whole ecosystem.
“The discovery that methane fluxes are
much more responsive to temperature than the processes that produce and
consume carbon dioxide highlights another mechanism by which the global
carbon cycle may serve to accelerate rather than mitigate future climate
change,” says Dr Yvon-Durocher.
This is not the end of the story. All such
studies raise as many questions as they answer, and more research is
necessary. The next puzzle is how to fit such findings into models of
climate change. However, the researchers feel they have cleared up one
point. Dr Yvon-Durocher says: “Our research provides scientists with an
important clue about the mechanisms that may control the response of
methane emissions from ecosystems to global warming.”