A man poses in front of a building and fountain.
Joe Holmes in front of Rideau Hall. The Canadian flag flies on the roof when the Governor General is out of town. Otherwise, his Royal flag (purple with a lion) is flown.
Image: Joe Holmes © Canadian Museum of Nature

As a volunteer with the Canadian Museum of Nature, I have been involved since spring 2016 in a project to collect diatom samples from more than 80 sites around Ottawa.

We visit lakes, rivers, canals and ponds to collect diatoms that will then be processed, photographed and added to the museum’s collection of 120 000 samples.

Preparing the samples, identifying the species and entering related data and photos into the museum’s phycology database are ongoing.

Visiting Rideau Hall
Our diatom project has involved looking for interesting places around the city from which to collect diatom samples. In June, I visited Rideau Hall, the principal residence of the Governor General, His Excellency the Right Honourable David Johnston, and his wife, Her Excellency Sharon Johnston.

An open gate in an iron fence beside a road.
At Rideau Hall, the south entrance off MacKay Street provides public access to the grounds.
Image: Joe Holmes © Canadian Museum of Nature

While touring the grounds (Rideau Hall is on a 31.6 hectare property), I found out from a staffer that there is a pond on the premises. However, it is located on the private grounds, requiring special permission to visit. Because Rideau Hall is an interesting place of national significance, I decided to go ahead and ask at the Visitor Centre for approval to access the pond and collect diatoms there.

A diatom viewed under a microscope.
This diatom was collected at Rideau Hall. It is a Caloneis silicula (size: 47 µm × 7 µm). Image: Joe Holmes © Canadian Museum of Nature

Diatoms are microscopic one-celled algae that have a silica shell and come in many different species, shapes and sizes. They are found in all bodies of water, in the mud on the bottom.

At the bottom of the food web, diatoms convert sunlight into energy and CO2 into oxygen. They are a primary food source for small creatures, which pass the energy further through the food web.

Scientists and botany students use diatoms to study DNA, climate change, evolution, water quality and the environment.

Not long after my request, the Rideau Hall maintenance staff contacted me and graciously arranged a visit to the pond. In July, I was escorted there by a helpful staff member to collect mud samples. The pond is horseshoe-shaped and in a wooded area called the Sugar Bush. It is just west of where the Governor General’s outdoor skating rink is placed each winter. The pond appears to be isolated, so its water likely comes from rain or the water table.

A pond.
The Rideau Hall pond, located in the woods in the private area of the grounds.
Image: Joe Holmes © Canadian Museum of Nature

Sampling Results

Back at the lab, I processed the mud samples, made microscope slides and photographed the diatoms using a camera-mounted light microscope with magnification of up to 1600 times. Overall, our results were very good; some diatoms even matched species that I found in Ireland and in Vancouver, British Columbia.

Composite of diatoms viewed through a microscope.
Some additional interesting diatoms found in the Rideau Hall pond (1 µm = 1 micron = 1 millionth of a metre):
1. Diploneis ovalis (17 µm × 7 µm)
2. Gomphonema acuminatum (51 µm × 10 µm)
3. Gomphonema insigne (44 µm × 10 µm)
4. Pinnularia viridis (73 µm × 15 µm)
5. Rhopalodia gibba (65 µm × 7 µm)
6. Placoneis abiskoensis (44 µm × 10 µm)
7. Reimeria sinuata (36 µm × 7 µm) 8. Frustulia rhomboides (59 µm × 15 µm).
Images: Joe Holmes © Canadian Museum of Nature

Because the Governor General is the representative of Queen Elizabeth II in Canada, the Rideau Hall diatoms will add a “Royal Canadian touch” to our Ottawa diatom project, which includes locations such as the Rideau Canal, the Ottawa and Rideau Rivers, Mud and MacKay Lakes, Mer Bleue and many other sites.

Overall, our venture will benefit students and scientists worldwide who are interested in diatoms from the Ottawa area and North America. The museum frequently works with botany students who are researching diatoms from Carleton University, the University of Ottawa and other universities and research institutions.