Canadian Library of Drifted Material

 copied from Schueler, Fred . 2026. The Canadian Library of Drifted Material. North Grenville Times 14(5):8, 12 Feb 2026 (1 watercolour by Luna Lopez-Andrews)

Fred Schueler – Fragile Inheritance Natural History <bckcdb@istar.ca>

Like many pretentious-sounding names, this tries to express what it really is. It originates in our collections of drifted material from shores all across Canada (and the adjacent USA), and its purpose is to serve as a library from which information about conditions along streams and lakes can be extracted.

The shells of land snails and aquatic Molluscs are the obvious content of these samples, but we anticipate that in time they and the bits of plants, insects, and even feathers and bones, will serve as references for the occurrence or absence of species, habitat features, and climate changes. Through the 1970s and 1980s we collected drifted samples from the shores of lakes and streams and deposited them in the national museum, but it wasn't until 1993, when we undertook a local survey of aquatic animals, and a sudden spring snow-melt provided us with a freshet, that we started to systematically look for drifted shells as a way of quickly summarizing the snail fauna of a drainage basin.

Then in 1997 we collected a sample of drifted snail shells from the shore of the the South Nation River at High Falls, and three years later, when Zebra Mussels made up most of a subsequent sample, we realized that repeated samples from the same site could help to trace the ecological history of the watershed (in 2019 the shores here were 10 cm deep in Zebra shells, and by 2025 there were many fewer Zebras and some native mussels).

Fragile Inheritance now has 1515 collections of drift, identified out into 4575 records of species. Robert Forsyth had identified many land snails, including the first record of a European species in Canada, and this past summer our intern, Luna Lopez-Andrews, provided me with a whole February of work in entering the species she sorted from many samples. Once the snail shells are removed from the sample, the residue is preserved so it can be examined for plant seeds & parts, microplastics, or other indications of conditions when & where it was collected.

The most diverse drift is found at the highest level of flooding, hung up among sticks and leaves or skimmed off through natural filters of grass from the current or eddies. Collecting is best after the water level has fallen about 30 cm from the crest, but before subsequent rain or trampling has dispersed the concentrations of water-sorted shells. We now have three decades of samples from numerous local sites, including the tailrace of the old Bishops’ mills at Mill Street, the overflow between the branches of the creek NE of Bishops Mills, the rocks near the dock below the Prescott Street bridge in Kemptville, and the main stream of the Rideau at Andrewsville – many of these samples document substantial changes in the streams’ molluscan fauna.

This year we’re going to be getting the Canadian of Drifted Material organized for a transition – to the Canadian Museum of Nature, or to a municipal museum. We can provide samples for students or volunteers to sort through, who would want to learn about the many species of a little-known Class of animals, and for study of the history of a site, here or as far away as Alberta.

Painting of shells sorted from a collection of drift, by Luna Lopez-Andrews.