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A Nuisance Algae: The Spread of Didymo in Crestone

An invasive alga, commonly known as didymo or “rock snot,” was observed blooming in South Crestone Creek in early May. Its spread is linked to climate change.

Didymo (Didymosphenia geminate) is a freshwater diatom alga native to North America, with small quantities of the cells documented in the fossil record for thousands of years. However, over the last few decades, didymo has been observed spreading rapidly within its native range and throughout the world. Warmer, drier conditions associated with climate change are likely responsible for the widespread didymo blooms, including the one observed in South Crestone Creek.


Fibrous mats of didymo bloom in South Crestone Creek, leaving certain insects and local fish at risk.
Fibrous mats of didymo bloom in South Crestone Creek, leaving certain insects and local fish at risk. Credit: Zaylah Pearson

Blooming Events

Didymo cells form dense, fibrous stalks that mesh together during blooming events, potentially entangling and displacing certain aquatic insects, such as mayflies. The blooms coat stream bottoms in slime, which may inhibit local fish productivity. It is unclear what the impact of this alga will have on the sensitive Rio Grande sucker and Rio Grande chub that live just downstream of South Crestone Creek in the Baca National Wildlife Refuge.


Smaller larval insects are unaffected and can even benefit from didymo blooms. Once didymo blooms in a creek, it is nearly impossible to remove. It is also extremely transmissible: a single drop of water carried by humans, pets, or wildlife from an infested stream can cause infestation of neighboring waterways.


Stop Didymo Spread

Efforts to control didymo prioritize prevention strategies, such as posting warning signs along infested portions of the creek and educating the public not to move between South Crestone Creek and other nearby waterways.


You can help stop the spread of this invasive algae:

  1. Keep dogs and other pets out of South Crestone Creek

  2. Clean equipment before entering a new waterway

    1. Dry completely for at least 10 days

    2. Sanitize with dish soap, boiling water, or a bleach solution

  3. Educate your neighbors about the spread of Didymo


Local biologists, environmental leaders, and concerned citizens are currently working on these preventative actions and determining the full extent of the infestation, including whether other local drainages may be affected.


The Baca Wildlife Refuge, Colorado Parks and Wildlife, and the POA have been notified.



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