Image Source :
Wikimedia Commons
Author
Brocken Inaglory
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Live Science
By Laura Poppick, Staff Writer | August 05, 2013 09:07am ET
Seaweed could smother polar underwater ecosystems as melting sea ice exposes the seafloor to more sunlight, new research shows.
Animals that dwell on the seafloor of the Arctic and Antarctic spend most of their lives in total darkness:
Sea ice
blocks rays during the spring and early summer, and the sun sets
completely in the winter. Late summer and early fall — when the ocean
warms up enough to thaw the ice — often marks the only time these
critters see light.
But as climate change causes
sea ice to begin melting
earlier and earlier in the summer, shallow-water ecosystems will soak
up increasingly more rays. New research from a team of Australian
biologists suggests this could cause a major shift in the seafloor
communities along the coast of Antarctica, where invertebrates like
sponges, worms and tunicates — globular organisms that anchor to rocks
on the seafloor — currently dominate. A manuscript of the report is
currently in press at the journal Global Change Biology. [
6 Unexpected Effects of Climate Change]
"Some
areas where ice breaks out early in summer are already shifting to
algal domination," said Graeme Clark, a biologist at the University of
New South Wales who was involved in the study.
Seasons and tipping points
Early-summer ice melt not only lengthens the amount of time photosynthesizing organisms like
macroalgae (or seaweed) can thrive
under the sun during the summer, but it also increases the intensity of
that exposure. The sun sits highest in the sky during the summer
solstice — the period when Earth tilts most directly toward the sun —
that occurs between June 20 and 23 in the Northern Hemisphere and Dec.
20 and 23 in the Southern Hemisphere, depending on the phase of the
Earth's orbit. Rays travel directly to the seafloor during this time.
During spring and fall, however, low-angle rays reflect off the sea
surface and often never make it to the seafloor.
This compounding
effect of a longer sunlit season and higher-intensity rays could
exponentially increase the amount of sunlight hitting benthic, or
seafloor, communities in the coming decades and cause major tipping
points for those invertebrate-dominated ecosystems, Clark said.
Tipping
points occur when relatively minor environmental changes — like sea ice
melting several days earlier than usual — cause rapid and significant
ecological transformation. In this case, the tipping point would push
ecosystems from invertebrate-dominated to algae-dominated.
Read More and Watch Video Here
A satellite image of Arctic sea ice snapped on Sept. 12, 2013.
: NASA's Goddard Space Flight Center Scientific Visualization Studio
