Seaweeds Escape Warming Oceans, Still Face Extinction

Yet another grim reminder of the disastrous effects of global warming. Huge swathes of Australia's seaweed are shifting south to escape warming oceans.  From the frying pan to the fire, it looks like. "Temperate species are moving to cooler environments," says marine ecologist Dr Thomas Wernberg of the University of Western Australia.

"In Australia there are no cooler environments beyond the south coast, so if they are pushed to go beyond that they basically go extinct."

While a lot of attention has been paid to the impact of climate change on corals, Wernberg says the impact on seaweed has been neglected.

He says while seaweeds might seem mundane they are an important habitat and food resource for underwater animals and plants.

Seaweed act as “trees of the ocean,” providing food, shelter and habitat for many other living things. As a result, changes in the seaweed community could have cascading affects.

Drawing on electronic records of seaweed from Australia's Virtual Herbarium, Wernberg and colleagues looked at how seaweed communities comprising up to 300 species had changed over time.

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They also compared the distribution of 52 species of seaweed along the east and west coasts of Australia during the period 1940 to 1960, with seaweed distribution during the period 1990 to 2009.

Wernberg says between the two 20-year time periods, the ocean warmed by a couple of degrees in southeast Australia and by a degree on the west coast.

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"What we saw is that the seaweed communities migrated south towards the cooler environments," says Wernberg.

The projected warming of between 1.8 degrees F (1.0 degrees C) by 2030 and 5.2 degrees F (3 degrees C) by 2070 — plus the rates of seaweed shift they calculated could mean the potential loss of 100 to 350 species over the next 60 years as the seaweeds' suitable habitat too far south. These represent about a quarter of all southern Australian seaweed flora.

Seaweeds can live anywhere between the high tide mark and about 262 feet (80 meters) deep. Past the edge of the continental shelf, the water's depths drop down to more than 0.6 miles (1 kilometer), water far to deep for seaweeds to inhabit. The width of the continental shelf along southern Australia varies, according to Wernberg.

Of the species that could be pushed over the edge, most live elsewhere in the world, meaning these extinctions would be local, but about a quarter face complete extinction if warming has the expected effect.

"Even if our simple, back-of-the-envelope calculation is an overestimate, it implies a considerable risk of substantial loss of global species diversity," the researchers write in a study published online on Oct. 27 in the journal Current Biology.



Source-Medindia