Native algae species to blame for 'rock snot' blooms in rivers worldwide

May 07, 2014

The recent blooms of the freshwater algae known as "rock snot" on river bottoms worldwide are caused by a native species responding to changing environmental conditions rather than by accidental introductions by fishermen or the emergence of a new genetic strain as widely believed, a Dartmouth College-led study suggests.

In fact, the algae have been native to much of the world for thousands of years, but conditions promoting visible growths were absent or rare. The study, which includes researchers from Dartmouth and Environment Canada, appears in the journal BioScience.

Didymosphenia geminata, also known in the scientific vernacular as "didymo," is especially worrisome in salmon and trout rivers because it affects the insects they eat. The study suggests multimillion-dollar eradication efforts with chemicals and fishing restrictions are misguided, and that resources should be redirected at understanding and mitigating the environmental factors that trigger the .

"Correctly identifying an invasive species as either native or nonnative is important for developing sound policy, management and scientific research programs because effective responses depend on knowing whether the species' dominance is caused by ecological or evolutionary novelty, changes in that facilitate it, or both," said Professor Brad Taylor, the study's lead author.

This video is not supported by your browser at this time.
The recent appearance of the freshwater algae known as "rock snot" on river bottoms worldwide is caused by a native species responding to changing environmental conditions rather than by accidental introductions by fishermen or the emergence of a new genetic strain as widely believed, a Dartmouth College-led study suggests. Credit: Credit Brad Taylor

Didymo blooms were hastily attributed to human introductions or the emergence of new genetic strain because the absence of evidence was used as evidence of absence in many locations. "Even in locations where rock snot had been recorded a century ago, this information was either ignored or the idea of a new genetic strain was adopted," Taylor says.

Algal blooms are often caused by excessive phosphorus and other nutrient inputs, but didymo blooms occur because phosphorus is low. Rock snot lives on and obtains nutrients from the water above. When nutrients are rare, the algae produce long stalks that extend the cell into the water above to access nutrients. The result of this stalk growth is thick mats covering the river bottom. "The paradox of didymo blooms in low-nutrient rivers is not really a paradox at all. However, the idea that low phosphorus can cause an algal bloom is hard for people to accept because we are all taught that more nutrients equal more algae," Taylor says. The study explains that other algae and bacteria respond similarly to low nutrients, but rock snot blooms are unprecedented, making this organism a good sentinel of what could be the new norm in many pristine rivers worldwide.

The new research suggests rock snot blooms have become more common because of climate change and other human-caused environmental changes that are decreasing phosphorus to levels that promote the formation of didymo blooms in many remote, otherwise pristine rivers worldwide.

Explore further: Researchers debunk argument of an invasive algal species in rivers and lakes

add to favorites email to friend print save as pdf

Related Stories

River mystery solved

Jun 03, 2011

The pristine state of unpolluted waterways may be their downfall, according to research results published in a paper this week in the journal Geophysical Research Letters.

Study pinpoints nutrient behind fresh water algae blooms

Aug 22, 2012

University of Alberta ecologist David Schindler has reviewed data from studies of controlling human-caused algae blooms in lakes and says controlling the input of the nutrient phosphorus is the key to fighting the problem.

When hungry, Gulf of Mexico algae go toxic

Mar 12, 2013

When Gulf of Mexico algae don't get enough nutrients, they focus their remaining energy on becoming more and more poisonous to ensure their survival, according to a new study by scientists from North Carolina ...

Recommended for you

Rising anger as Nicaragua canal to break ground

31 minutes ago

As a conscripted soldier during the Contra War of the 1980s, Esteban Ruiz used to flee from battles because he didn't want to have to kill anyone. But now, as the 47-year-old farmer prepares to fight for ...

Hopes, fears, doubts surround Cuba's oil future

Dec 20, 2014

One of the most prolific oil and gas basins on the planet sits just off Cuba's northwest coast, and the thaw in relations with the United States is giving rise to hopes that Cuba can now get in on the action.

New challenges for ocean acidification research

Dec 19, 2014

Over the past decade, ocean acidification has received growing recognition not only in the scientific area. Decision-makers, stakeholders, and the general public are becoming increasingly aware of "the other carbon dioxide ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.