Boreal Shield lakes resemble prehistoric oceans, researchers say

Lakes that dot Canada's Boreal Shield region offer important information about greenhouse gases and early life forms, their numbers potentially revolutionizing studies into Earth's early life forms.
Lake Laurentian Conservation Area near Sudbury, Ont., is pictured above. Canada's boreal lakes may hold the key to finding more about how life developed in ancient, oxygen-free oceans. (Olivia Stefanovich/CBC)

The lakes that dot Canada's Boreal Shield region are similar to the ancient oceans of the Archean Eon, a period over 2½ billion years ago, and offer important information about early life on Earth, according to researchers from the University of Waterloo.

Scientists have used what are called analogue lakes, or lakes that share important properties with Archean oceans, to learn about how early microbial life began — and how those tiny life forms began to thrive.

The discovery means research into this era can be done in more accessible and less-threatened regions. 

Previously there were only four analogue lakes that scientists relied upon for their studies, most of them in remote, environmentally sensitive areas. But the new research published in the journal Scientific Reports shows there are plenty more of the lakes in Canada, opening up the potential for more research to be done.

"With so many lakes to study, this discovery changes how we approach this field of research," said co-author Jackson Tsuji, a doctoral student in the department of biology, in a news release on Thursday.

Less oxygen, more iron

Early life forms on Earth grew out of oxygen-free oceans, which were low in sulphur and high in iron. Researchers found that lakes in the Boreal Shield region are also low in sulphur and high in iron, and in the summer they can develop oxygen-free layers.

Although the lake water layers do mix in the spring and fall, the oxygen-free layers re-establish themselves, said the researchers.

Not only that, but microbes that grow in the oxygen-free areas are "robust," according to biology professor Josh Neufeld.

"We used to think finding a suitable Archean ocean analogue meant that you had to find a lake that didn't mix. For example, current analogues are hundreds of metres deep and completely stratified," said Neufeld. To imagine a stratified lake, picture different layers of liquids, like oil floating on top of vinegar in your salad dressing.

The microbes that live in the lakes are thought to metabolize iron compounds with the help of sunlight, and may be useful in controlling harmful algal blooms. Other microbes that live at the bottom of lakes consume methane gas, which would be useful in controlling greenhouse gas emissions. 

Boreal lakes are numerous in the Boreal Shield region, which makes up more than 20 per cent of Canada's land mass.