Frozen Fingers in Crawford Lake: A World Water Day Celebration

Written By: Karlee May, Digital Media Coordinator

The frozen finger pushes into the sediment and bores down into the lake basin. A researcher injects liquid nitrogen into the finger to freeze the sediment, and preserve the sample for examination. During careful analysis of the sediment, researchers discover corn pollen, but this corn pollen is hundreds of years old.

Why is there ancient corn pollen at the bottom of a lake in an area where corn, a farmed vegetable, hasn’t grown? Where did it come from? Who grew the corn close to six centuries ago?

Crawford Lake

The corn pollen has lain in the sediment at the bottom of Crawford Lake, a Meromictic lake. In a meromictic lake, the water does not completely circulate through the basin at any time of the year, because of the chemical composition of the water or because the deep water is inaccessible to the churning power of the wind. Picture a cone-shape, where the surface area of the lake isn’t large enough to allow the wind to mix the top layers of water with the very bottom layers.


A Meromictic lake is permanently separated into three layers: mixolimnion, chemocline, and the monimolimnion. The mixolimnion is the top layer of the lake, and, like the name suggests, the wind ‘mixes’ this layer. The chemocline is the middle zone between the circulating water on top, the  mixolimnion, and the still water of the bottom, the monimolimnion. The chemocline acts like a bordering belt between the warm layer on top and the cold deep water of the bottom. The bottom layer of the lake, the monimolimnion, is too deep for the wind to cycle the water, and the water is too cold to mix with the warmer layers above it. Because of this, the sediment that collects at the bottom, remains there due to lack of circulation. The monimolimnion layer is why the Pollen Corer, nicknamed the Frozen Finger, found centuries old samples of corn pollen left by Iroquoians. The bottom layer consequently has very little dissolved oxygen and this can create ideal conditions for preserving whatever happens to settle along the bottom of a meromictic lake.

The Layers of a Meromictic Lake

The Layers of a Meromictic Lake

Without protection and careful monitoring, this precious discovery, a discovery that lead to a fuller understanding of the history, and the heritage of Halton Region, wouldn’t have occurred. Our water sources not only provide nutrients, but also provide insights into our past; and, conservation areas, such as Crawford Lake preserve, enhance, and share this cultural heritage.

This week, March 17th-March 22nd,2014, is Canada Water Week: a period of education and celebration about the world’s most precious resource—fresh water and the watersheds. We use water for nourishment, enjoyment, and energy. Canada Water Week activities encourage Canadians to learn more about our watersheds and to drive discussion about good policy choices and water preservation management.

CWW-Banners-Supporter-Masthead (1)

Canada Water Week ends with the United Nations International World Water Day on March 22nd, 2014. One of the five key messages of the day is “saving water is saving energy; saving energy is saving water”. Talking about the symbiotic relationship between water and energy–with key players in regard to supply, distribution, price, and conservation–informs policy choices that will better serve the ‘bottom billion’- the impoverished 2.5 billion people without access to electricity or improved sanitation and water sources. Through education and awareness of policy for conservation practices, we protect the environment and serve the global community. We’re all in this together.

Conservation Halton will host its own World Water Day Celebration. On March 22nd, 2014, Halton Membership holders can register for an exclusive members-only event. Please join us in the Auditorium in the Crawford Lake Visitor Centre for a short presentation and a guided hike to the site’s stunning, and rare, Meromictic Lake. You will learn more about our local water and the ways you can conserve this water at home and in your daily activities. Space is limited so register your spots quickly using the link below:

For more information on the World Water Day Celebration at Conservation Halton, Please Click Here.


UN World Water Day – March 22nd, 2014 – for more information about World Water Day

Benefits of Healthy Watersheds – for more information from Conservation Ontario about Watersheds

Meromictic Lake – Wikipedia Entry – for a basic summary of a Meromictic Lake

Canada Water Week – for more information about Canada Water Week

Protecting Your Watershed – for more information about protecting your watershed from Canadian Geographic

Halton Parks Members World Water Day Celebration – for the Conservation Halton Event Listing


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