Monday, November 15, 2010

Beach Spores Help Seed Clouds




This is a bit of the not so obvious.  I had always had a little interest in the mechanics of the production of atmospheric dust.  It seemed a bit too tidy and unexplored in terms of the science.  It was far too easy to blame it all on arid clays and glacial silts which all sound pretty sterile.

Living spores flying up out of sands and beach sands in particular certainly has the potential to produce a vast ocean of airborne particulate.  So does everything else, but wind blown sand sounds like a great machine for releasing them

So perhaps it is time to evaluate spore types everywhere to learn the effect of different regimes.

Sandy spores help seed clouds
Nov 2, 2010


For most of us sandy beaches are associated with sandcastles and sunbathing, but now it turns out that these golden stretches of coastline could also play an important role in the kind of weather that we receive. New research shows that bacterial and fungal spores in windblown sand may be influencing the amount and type of clouds in the sky.

Brian Palenik from the Scripps Institution of Oceanography, US, and colleagues collected air samples from the end of the Scripps Institution of Oceanography pier – located around 300 m from the shore. An analysis of the aerosols in the samples showed that two types of fungi – Basidiomycota and Ascomycota – and two types of bacteria – Firmicutes and Proteobacteria – were common constituents of the mix.

"This wasn't what we expected," said Palenik. "These did not appear to be coming from the ocean water since we know a lot about the species living in coastal seawater. However, these bacteria and fungi appear to be 'marine', so we think they are coming from beach sand."

Previous research has shown that aerosols of biological origin – plant debris, pollen, fungi, bacteria and viruses, for example – can act as seeds for ice crystals to grow on, hence helping to create clouds. "This can impact precipitation and cloud radiative properties," explained Cassandra Gaston, another member on the research team.

A biological aerosol's effectiveness at seeding cloud droplets and crystals may also depend on the shape, size and state of the cell, with some species or cell stages providing better nucleation surfaces than others.

Biological aerosols, thrown into the air by ocean spray and hurled into the atmosphere from winds blowing across Earth's deserts, are already known to play an important role in cloud formation, but until now, no-one had considered microbes emanating from sandy beaches.

Palenik and colleagues' data suggest that sandy beaches could be a significant source of biological aerosols with the potential to affect cloud formation. Since sandy beaches are found all over the world they may be an important provider of biological aerosols and hence play a previously unappreciated role in our weather.

And as our climate changes the role that some of these biological aerosols play could alter too. Warmer temperatures could increase productivity and increase the proportion of biological aerosols, stronger winds could throw more sand into the air and whip up more spray from the ocean or heavier and more persistent rain could dampen things down. As yet the outcomes are not at all clear.

But first Palenik and his colleagues want to better understand the current sources and sinks of sandy beach aerosols, and try to define the importance of their role in atmospheric processes. Time to head back to the beach…

About the author
Kate Ravilious is a contributing editor toenvironmentalresearchweb.

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