Ryerson University

Ryerson University

January 18, 2007 11:02 ET

Ryerson University: Zebra Mussels May Cause Potentially Toxic Blooms In Lakes

TORONTO, ONTARIO--(CCNMatthews - Jan. 18, 2007) - Zebra mussels may be changing the chemistry of lake water in Canada, spurring the growth of potentially toxic blooms, reveals a study by Ryerson University environmental scientists.

Blooms, a mass of cyanobacteria mostly caused by phosphorus (a product found in household detergents), were very common in the 60s and 70s, says Andew Laursen, co-author of the study and a professor in the Department of Chemistry and Biology. When the chemical was banned from detergents in the 70s, the blooms lessened.

"However over the last decade we're starting to see these blooms of cyanobacteria re-emerging again, and we believe it's due to zebra mussels altering the lakes' water chemistry."

Some species of cyanobacteria are secreting chemicals that alter the taste of our drinking water and create a foul odour, and some species emit toxins that can be potentially harmful to humans, says Laursen.

Olga Bykova, the study's lead author when she was a masters student at Ryerson, and her co-authors including Laursen, Vadim Bostan, Joseph Bautista and Lynda McCarthy, simulated the ecosystem of lakes by constructing 12 nine-foot water columns, some with zebra mussels and others without. Fresh water was pumped from the bottom to the top of each column so the tubes containing mussels would receive fresh oxygenated water and food (a mix of cyanobacteria and algae). Mussels extract organic particles, containing nitrogen and phosphorus, from the water. When they deposit this organic matter on the sediment, the nitrogen converts to a gas form while the phosphorus remains.

The researchers found when mussels were present, the levels of nitrogen decreased while phosphorus levels were not affected, creating favourable conditions for blooms to grow. Even when they altered the ratios of nitrogen and phosphorus in the tubes without mussels to simulate the presence of the shellfish, the cyanobacteria grew faster than the algae.

Laursen says this supports the idea that changes in the water chemistry may explain the increase in blooms in lakes invaded by zebra mussels. "What this and other studies suggest is that there is a strong correlation between zebra mussels and cyanobacteria. Where you get these mussels, you get more frequent blooms, which affects the quality and taste of our drinking water."

The study was published in the December issue of the journal Science of the Total Environment.

Contact Information

  • Ryerson University
    Andrew Laursen
    Department of Chemistry and Biology
    (416) 979-5000 x 4059
    Email: alaursen@ryerson.ca
    or
    Ryerson University
    Suelan Toye
    Public Affairs
    (416) 979-5000 x 7161
    Email: stoye@ryerson.ca