How to Safely Ship Zooplankton Samples in Preservative
Notes on Formalin and Shipping Constraints
For long-term storage (greater than one year), 2–5% sweetened and buffered formaldehyde (i.e., 5.4–13.5% formalin) is the only permanent preservative routinely used for zooplankton. These two terms are frequently confused: formaldehyde is the chemical compound (HCHO); formalin is a saturated aqueous solution of formaldehyde gas, specifically 37–40% formaldehyde by weight. This means that 37% formaldehyde and 100% formalin describe the same solution. Confusing the two when preparing preservative leads to serious errors in concentration.
The preservative should be buffered with sodium borate or hexamine to prevent acidification over time, which can dissolve zooplankton carapaces. Glycerol or sucrose is added to stabilize specimen morphology and further protect carapace integrity during long-term storage. Samples submitted to IdentaZoop should be preserved at 5.4–13.5% formalin using a buffered and sweetened solution.
Under Canadian WHMIS (Workplace Hazardous Materials Information System) regulations, formaldehyde is classified as a confirmed human carcinogen. Preparation and handling require fume hood ventilation, appropriate respirators, and chemical-resistant gloves. Refer to the current SDS (Safety Data Sheet) for formalin for full handling requirements before preparing preservative in the field or lab.
Formalin is classified as a Hazardous Material per current Transport Canada regulations; however, since the sample bottles contain under 1 litre of formalin, shipments fall under the Limited Quantities classification (Section 1.17). The shipment must indicate this on the waybill and the approved Limited Quantities symbol label must be affixed on one side. Text notation of "Limited Quantities" or variations are no longer accepted.
⚠️ Important Note: Formalin creates artifacts in fixed tissue when frozen, damaging fragile zooplankton bodies. To prevent this during transit, samples must be received at IdentaZoop's location in Northeastern Ontario by late October. Please plan your collection and shipping schedules accordingly and get in touch as early as possible to secure your spot in the processing queue.
If shipping during colder months is unavoidable, expedited courier service is required. It is also strongly recommended to line the cooler with Styrofoam and to add hot packs — as shown in this picture of a cooler, set up for winter shipping.
The following shipping guidelines are strongly encouraged due to the hazardous nature of formalin.
Containment Requirements
Level 1: Sample Leakage Prevention
This is the most critical component: if your sample bottles are properly sealed, the other levels only serve as precautions.
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Use 125 mL wide-mouth HDPE bottles with leak-proof polypropylene lids for both field collection and shipping.
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The alternative is to use electrical tape on the outside of the sample bottle lids, to tightly cover the seams. This is easy to apply and forms a very effective seal.
⚠️ Important Note: Regardless of the type of shipping bottles used, it is strongly recommended to avoid handling samples after field collection. Freshwater zooplankton typically measure less than 3 mm so transferring field samples to smaller bottles for shipping will inevitably result in loss of bodies.
Level 2: Sample Leakage Containment
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Enclose samples in a thick plastic bag with spill-absorbing pads, as seen in this picture showing a packaged set of samples.
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Alternatively, enclose samples in securely closed Ziploc-type bags or thick plastic bags taped shut, as shown in this picture. It is recommended to line the bottom of the shipping container with spill-absorbing pads, in case of leakage.
Level 3: Shipment Leakage Containment
If the above 2 steps are implemented, this level should not be necessary but is still recommended to mitigate any major leakages.
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Use a hard cooler or heavy-duty plastic tote taped shut with duct tape as your shipping container. Cardboard boxes containing leaked samples may not be delivered by the courier service, so please do not run the risk.
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Please do not use jumbo size containers/coolers (i.e., over ~25" long; the ones pictured are 32" long) and limit the weight per container to a maximum of 50 lbs. This is added incentive to use plastic versus glass sampling jars. Cooler size and weight limits are both a safety and practical necessity.
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Plenty of padding is recommended to keep the bottles upright and secure, especially if using more fragile glass jars.
Shipments must be sent via courier ground service due to the "Limited Quantities" designation of these samples. Clients typically use Purolator, UPS, or FedEx. A completed Sample Submission Form must be included in the shipment, form to be supplied by IdentaZoop upon project booking.
Upon project completion, coolers, sampling jars (rinsed but not sterilized), and processed samples in final storage vials will be returned via Purolator ground service, at no added cost. Returns occur once outside temperatures are consistently above 10°C. All client materials will be safely stored until shipped.
Notes on Sample Waste
Excess sample preservative from each client's samples is re-used for final storage of that same client's samples. Generally, only 30 mL is needed, though denser samples may require 60 mL. Any excess must be treated for safe disposal. Please minimize your field sample bottle size to reduce the amount of waste generated. See above under Level 1 for the highly recommended bottles, in a 125 mL size. The bonus with those is that they are reusable, reducing the amount of plastic waste. A surcharge may apply for samples that generate an excessive amount of plastic/preservative waste. Your cooperation in minimizing waste is greatly appreciated.