An algal bloom in a lake near Parry Sound, Ontario, located on the Canadian Shield, another region of Canada experiencing lakewater calcium decline. Image courtesy of Andrew Paterson. (Credit: Ontario Ministry of the Environment)

ScienceDaily (Sep. 28, 2011) — Unprecedented algae growth in some lakes could be linked to the decline of water calcium levels and the subsequent loss of an important algae-grazing organism that helps keep blooms at bay.

Daphnia – also known as water fleas — act like microscopic lawnmowers in lakes, feeding on algae and keeping it in check. However, without sufficient calcium, these water fleas cannot reproduce.

"When water calcium levels get low and Daphnia populations decrease in any lake, algal growth goes unchecked and blooms can occur," says lead author and biology doctoral student Jennifer Korosi. "Losing an important grazer like these water fleas has a domino effect that leads to other water quality problems."

Declining calcium concentrations in some lakes, which is linked to acid deposition and logging, has only recently been identified as a serious environmental problem in North America and Europe.