at the Bishops Mills Natural History Centre

[Drift collection]

The Canadian Library of Drifted Material (CLDM)

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 as they become older they will serve as references for the occurrence or absence of other taxa and other conditions. We collected drifted samples from the shores of lakes and streams and deposited them in the NMNS through the 1970s and 1980s, but it wasn't until 1993, when we had support for a local survey of aquatic animals, and a sudden spring snowmelt provided us with a freshet, that we started to systematically look for drifted shells as a way of quickly summarizing the land snail fauna of a drainage basin. Since then we have collected drift wherever we find it, and some of the surveying is described in our book A Place to Walk (Karstad, et al, 1995), our methods in Schueler (1997), and some artistic by-products at Drifted! http://www.pinicola.ca/drifted.htm

Methods: The most diverse drift is at the uppermost line of highest tide or flooding, or skimmed off by 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 disrupted the concentrations of water-sorted shells. You want to gather these top handsfulls of shell-rich drift, and you'll soon learn to recognize them by their uniformly fine texture - whether you can see the shells of Molluscs in the handsfulls or not. In ditches, streams, and rivers such concentrations are often found after floods or spates above or below bridges or culverts. They may be filtered out of passing water by seive-like vegetation, or winnowed by the circular movement of whirlpools or eddies. Sometimes very concentrated deposits are formed under the overhanging lip of sod on the top of a abnk. In lakes or marine shores shells may be concentrated in gaps in shoreline vegetation or where waves turn on themselves at the ends of docks, breakwaters, or logs. On some marine or lake shores you'll also want to pick up the sunken drift that accumulates just at the foot of the beach slope, either underwater or revealed at low tides. The best concentrations often occur a few tens of metres beyond where you've thought of giving up because the drift, while voluminous, doesn't include any concentrations of shells. Scoop the richest handsfulls into a plastic bag, insert a tag bearing a unique identifier, and tie it closed.

Record the locality, to museum standards of labeling, ideally within 100 m, by a distance/direction location name (e.g. Hwy56/Mickle Crk, 2.3kmSSE Whimseyville, Bracken Twp., Bracebridge Land District), and if possible in the UTM grid notation explained on topographic maps (e.g. Map 31Q/14 grid 17TXE 347 893), the latitude and longitude from a GPS unit (being sure to specify the map datum in each case), or an e-mail of the position from an internet mapping service. Record the date, type and size of water body, the surrounding habitat, what kind of water-level event deposited the sample, and the length of shore that was searched to obtain the sample.

Freeze the sample at -20C or so for a couple of days to kill any living Animals that may be present (this both prevents the spread of pests, and immobilizes any entomologial specimens that might otherwise leave the sample during drying). Thaw the sample in the closed bag, spread it out to dry thoroughly on newspaper (artificial heat may be required in humid climates - but the idea is that these specimens are already dried out, so don't include any fresh flesh in the sample), and store it in paper bags or cardboard boxes. You can discard coarse debris, sift the sample with compost sieves to concentrate the shells, and sort out shells, seeds, and insects into small containers or vials, but keep a record of any such manipulations so that future users of the sample know what's been done with it. Include some of the mineral substrate (fine gravel, sand, mud, etc.). Be sure that every sub-division of a sample always includes a label that uniquely identifies it.

Package the samples carefully (if there are both delicate plants or shells and gravel, rocks, or heavy shells, separate each kind, and pack separately in such a way that the containers can't shift around. On the other hand, light plant chaff can serve as packing, and if there's no heavy chunks, the sample can just be shaken down into a double plastic bag, and packed into a box. Clearly label different samples in plastic bags in a strong box), and ship to Bishops Mills Natural History Centre, RR#2 Bishops Mills, Ontario, Canada K0G 1T0 (613)258-3107 or from the USA to Aleta Karstad in care of Finlayson-Schuelers, 118 Shirley Road, Syracuse, New York, 13224.

Data and numbering: Data for CLDM samples are stored in the EOBase database. Formal cataloguing is beginning in October 2004, with each sample assigned an integer CLDM number, in the SPEC_NUM field of the database. When specimens are extracted each species receives a sequential lot number, which can be further subdivided by letters if different samples of the same species receive different treatment - "CLDM00034/001/a" When a sample is catalogued in a museum collection, or assigned specimens numbers by an identifier, this number replaces the CLDM number in the SPEC_NUM field, and the CLDM number is placed in the REMARKS field and in the CURATION field prefixed by "Canadian Library of Drifted Material number:"

Loans of material: It is anticipated that CLDM material will be sorted by specialists, and the extracted specimens either retained for their collections or returned to us. Borrowers will be requested to report on the effort expended and the methods used in sorting the sample, fill out an electronic sorting form (the species found, the number of each extracted, and a verbal estimate of the species' abundance in the sample, any measurements taken, and the disposition and collection number of the specimens), and return the residue to us.

The most assimilable form for the sorting form would be a *.dbf table with these fields:

NAME - species

COUNT - the number extracted + "/" + verbal estimate of the species' abundance in the sample, e.g, "23/abundant" or "6/few"

REMARKS - any measurements taken or other comments (up to 57 characters, or TEXT memo field if longer), or MEASURE - measurements listed in a memo field

SPEC_NUM - collection number of specimens extracted

...but any format that contains these data would be okay.
Literature cited:

Karstad, Aleta, Frederick W. Schueler, and Lee Ann Locker. 1995.
A place to walk: A naturalist's journal of the Lake Ontario Waterfront Trail.
Natural Heritage/Natural History, Toronto. 159 pp.

Schueler, Frederick W. 1997. Collecting Land Snails: After the floods surveys for biodiversity.
Watershed Sentinel 7(1):25-27.

APPENDIX I: An example of a residue label:

Canadian Library of Drifted Material

Mollusca. shell, drift, specimen. CLDM00004


Canada: Ontario: Grenville County: Augusta: Diamond Rd/Kempville Crk, S of Co 18/Branch Rds. MAP:31B/13, UTM 18TVE 465 638. 44.82760N 75.67638W

20 October 2004 TIME: 1719-1752. AIR TEMP: 11.5, cloudy, breezy

COLLECTED BY: Frederick W. Schueler, Ben & Joel Chrysler Field#: 2004/168/a

HABITAT: pasture along slow creek through crkside meadows, Ash forest, adj.farms; drift on sheets of algae 3-5 m from the creek.

Subject: drift
Date: Tue, 5 Oct 2004 00:01:45 -0400
From: "Bob Woolham" <woolham at ripnet.com>
To: "Frederick W. Schueler" <bckcdb at istar.ca>

Hi Fred - if you're still looking for "drift", as in washed up snail shells and such like following recent flood, shout me up. There are lots along the fence (electric, which is off) line on the creek pasture, which I noticed while checking the fence today. They are piled up on the now dry grass on the creek side of the fence, probably for about 100 yards or so. - bob


This was from the heavy rain of 9 September - but there hasn't been much rain since, and the shells are still pretty well undisturbed. The sample was made by picking up big shells from a sheet of dried algae over Myriophyllum and Elodea over the grass, and scooping concentrated handsfulls at the upper (inland) margin of this sheet along the electric fence on the north bank upstream from the bridge.


This is coarse residue from preliminary sorting by FWS and Joel Chrysler, 27 October 2004. The big species and dried vegetation were extracted, leaving smaller snails that should be catalogued as CLDM00004/005 et seq. The smaller species included a moderate number of small planorbids, and very few Succineids and Physa, comprising a very impoverished sample - the absence or rareity of Helisoma anceps and Stagnicola elodes was particularly striking.
Determined by: F.W.Schueler; Site accuracy: 150m upstream fr bridge; Coordinates from: map reference location, datum UTM NAD 27 Canada & Lat-long WGS 84; EOBase entry: FWSOBS FWS/2004Oct25/1436:35; source: FWS/biography/as entered/EOBase; record last modified: FWS/2004Oct28/1139:32.
Bishops Mills Natural History Centre

back to Umbra main page

back to Bishops Mills Natural History Centre

back to Collections