[Science Centric 8 December 2010] -- While Asian carp, gypsy moths and
zebra mussels hog invasive-species headlines, many invisible invaders are
altering ecosystems and flourishing outside of the limelight. A study by Elena
Litchman, Michigan State University associate professor of ecology, sheds light
on why invasive microbial invaders shouldn't be overlooked or underestimated.
'Invasive microbes have many of the same traits as their larger, 'macro'
counterparts and have the potential to significantly impact terrestrial and
aquatic ecosystems,' said Litchman, whose research appears in the December issue
of Ecology Letters. 'Global change can exacerbate microbial invasions, so they
will likely increase in the future.'
The public and scientists seem to be well-informed of the spread of Asian
carp, zebra mussels and gypsy moths - all invasive macroorganisms. But what
about exotic cyanobacteria, also called 'blue-green algae,' which have found
their way into North American and European lakes? Or a nitrogen-fixing
rhizobium, a soil microorganism that has emigrated from Australia to
Portugal?
In the Great Lakes, a brackish diatom (a microscopic alga), has colonised
Lake Michigan probably via ballast-water discharge and is now the largest diatom
in the waterways. How will it change the ecosystem? What changes has it caused
already?
While many people have a working knowledge of the American chestnut blight,
which was caused by a pathogenic parasitic fungus, most invasive microbes fly
beneath the radar of the public and scientists alike. Virtually nothing has been
published on the potential of nonpathogenic microbes on a large scale, according
to Litchman.
'From scientific research, we know that the chestnut blight dramatically
altered forests and how the spread of West Nile virus is associated with
significant bird die-offs,' she said. 'Currently, there are no published
examples of the impacts of invasive nonpathogenic microbes, but there is growing
evidence that they could change ecosystems in equally dramatic fashion.'
The lack of attention to microbial invasions compared to macroorganisms is
due, in part, to their cryptic nature and the difficulty of detection. Lack of
detection combined with climate change could potentially increase these
microbial invasions, which could continue to grow as the earth's weather
patterns change, Litchman said.
'Increasing air temperatures have been implicated in the spread of malaria
and other pathogenic microbes into higher altitudes and latitudes,' she said.
'Likewise, climate change could stimulate invasions by tropical and subtropical
nonpathogenic microbes into temperate latitudes.'