Ecological Impacts of Dreissenids on Cyanobacteria-Producing Toxins in Western Reservoirs
Zebra/quagga mussels have been linked to improving water clarity, changing the composition of foodwebs, and altering nutrients in lakes. Most recently, attention has also focused on the association between dreissenids and increased cyanobacteria (blue-green algae) blooms, and cyanobacteria producing algal toxins.
Algal toxins can be detrimental to human health and cause animal deaths, including cattle and dogs. Ingestion of significant levels of the algal toxin Microcystin can cause liver damage and dysfunction in humans and animals. As a result, lakes and reservoirs have been closed because of Microcystins exceeding World Health Organization guidelines for drinking water (1 microgram per liter [µg/L]) and recreation (20 µg/L).
In the mid-1990s, cyanobacteria producing algal toxins were on the rise in the Great Lakes, following dreissenid mussel introductions, explained by a number of different theories that involve altered nutrient concentrations and recycling, as well as filtering selectivity of plankton.
Over 300 reservoirs will be surveyed for both zebra/quagga mussels and cyanobacteria producing algal toxins. This research will focus on the question, "Do zebra/quagga mussel infestations in western Reclamation reservoirs result in increased cyanobacteria (blue-green algae) blooms, as well as increased cyanobacteria producing algal toxins?"
Need and Benefit
Algal toxins produced by cyanobacteria in reservoirs are on the increase and caused by eutrophication, weather modifications, and, most importantly, infestations by dreissenids. Most of Reclamation reservoirs have never been examined for algal toxins. Now, with zebra/quagga mussels infesting our reservoirs, there is a real need to investigate the influence of dreissenids on cyanobacteria producing algal toxins. Increased algal toxins in a reservoir have closed reservoirs/lakes due to human health risks. The association between zebra/quagga mussels and increased cyanobacteria producing algal toxins is not well understood, although in the Great Lakes, it appears that an increase in algal toxins has been present since the infestation of dreissenids.
The benefit of reporting algal toxin data could be preventing serious health risks, as well as possibly preventing the closure of a Reclamation reservoir.
If an infestation by zebra/quagga mussels is reported, then is it possible to predict greater cyanobacteria producing algal toxins in a watershed?
The following documents were not reviewed. Statements made in these documents are those of the authors. The findings have not been verified.
ARRA Toxin Data (final, PDF,
By Chris Holdren
Report completed on June 03, 2014
This information was last updated on March 3, 2015
Contact the Research and Development Office with questions or comments about this page