Didmyo invades Patagonian rivers

A leathery brown slime is slowly creeping across what are widely considered to be the world’s most pristine rivers. Discovered first by William Horvath, a Patagonian kayaking guide, Didymosphenia geminata, or Didmyo, is a highly invasive alga that has mucked up numerous freshwater bodies across the world.  Didmyo forms large algal mats, secreting a thick layer of muck for which the popular nickname “rock snot” was given.

Aesthetics aside, Didmyo can be ecologically devastating. By coating river surfaces, it prevents sunlight from penetrating, thus killing off other photosynthetic organisms. Thick colonies rapidly deplete both river nutrients and oxygen; in much the same was that algal blooms have devastated the Gulf Coast and led to a massive anoxic dead zone.

Didmyo has appeared in numerous northern hemisphere rivers, and its first southern hemisphere appearance was in New Zealand five years ago. Researchers at the National Fisheries Service have identified several common factors in Didmyo blooms. Didmyo apparently thrive in stable water bodies, downstream of nutrient sources such as farming operations and wastewater treatment plants. Why it spreads so rapidly, and particularly in remote, unpolluted regions of southern Chile and New Zealand, remains a mystery.

Though scientists are not necessarily optimistic, the Chilean government is now launching a huge effort to stop the spread of the algae.


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