The eco guide to algae

[USA] Toxic bloom is terrible for acquatic life – the good news is, we may be able to harness the sludge as a carbon-neutral biofuel.

Ideally, in these days of busy news cycles, an eco problem needs to be visible from space to gain traction. Algae has obliged again this summer.

At Florida’s largest freshwater lake, Okeechobee, the cyano-bacteria blue-green algae bloom, covering 33 miles, has been clearly captured in Nasa satellite imagery.

Ecologists are fond of describing the Okeechobee as the perfect nursery for toxic blooms. There’s been a history of dredging, a heavy presence of nitrogen and phosphorus fertilisers from industrial agriculture draining into the lake, large quantities of water withdrawn for agricultural use (this can also be a factor) and warmer and wetter weather. It is hard to prove the exact causes of toxic algal blooms, but activists pose this formula: climate change + political inertia = cyanobacteria.

As the bloom dies off, algae decomposes and creates hypoxia (deficiency in oxygen). The less-mobile animals near the floor of the waterway are the first to die, but the algal choke continues through the food chain. I’ve seen heart-breaking footage of Florida residents hosing down and feeding manatees fresh water after they’ve battled through the algal scum.

But the upside of algal blooms also represents a big green story. Could algae be a long-dreamed-of carbon-negative biofuel? If algae can be harvested and used as a source of power, then it represents what geo-hackers like to call a “twofer”: a free source of biofuel using nutrients that would otherwise require an energy-intensive treatment process in order to be removed.

But to farm anything at scale we like predictability, while algal blooms are anything but. So the rise of algae as a green fuel means the rise of algal farms – which use yet more water and more energy.


Photo: Swimmers beware: toxic blue-green algae in Shadwell Basin, east London. Photograph: Michael Kemp/Alamy

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