S-1 SOIL FIELD SAMPLING

Field sampling of eDNA sediment samples involves two people. One person serves as the ‘sampler’ and the other person serves as a ‘helper’. The helper can look up details in these instructions when needed, keep track of samples, handle objects that are contamination risks, serve as a second set of eyes for potential contamination, and ensure safety of the sampler in potentially hazardous field conditions.

Find two suitable sampling locations within the water body representing different ecological systems, if possible.

At each sampling location, soil samples should be taken from two points, one at the edge of the waterhole and the second one meter in from the edge. Sediment collection at each sampling location should be done in triplicate.

Because ‘the edge’ of the water body may change due to precipitation changes, the edge should be defined at each month's sampling.

If the water body has a "drop off" (embankment of more than 20 cm), the soil and water samples should be taken where the water "meets" the soil. Aim to collect at locations where finer sediment is present, if possible.

At each sampling location, the helper opens the bag containing the vials to have one open and ready for the sampler. The helper will open and close the bags containing the collection materials. This is to prevent potential contamination of samples.

Collect sediment using a suitable and appropriately labeled sampling device (such as a clean dipper head or corer). The Sampler takes the appropriately labeled sampling device (for example, SL1-edge would be the device for sampling location 1 at the edge).

If using a dipper head, scrape the surface of the bottom of the water body. Gently pour off any water within the dipper head over bare ground (not over the water body) taking care to minimize loss of fine surface sediments.

If using a corer, sample from the first 1-3 cm depth of the bottom of the water body. Cut the exposed sediment with a stainless steel or plastic (HDPE or PTFE) cutter.

The Sampler takes the appropriately labeled spoon or scoop (for example, SL1-edge would be the spoon or scoop for sampling location 1 at the edge) from the Helper and fills an appropriately labeled 50 mL falcon® tube with 10 mL of sediment. Do NOT place rocks in the tube. Cover sediment with water from the collection site leaving no airspace.

Close the Falcon® tube and dry it using paper towels.

Label the Falcon® tube.

Place the Falcon® tube into the cooler box filled with ice for storage.

Repeat the sediment sampling 3 times per sampling location point (for example, three times at the edge and three times at the 1 m point).

Record sediment quality characteristics and information relating to samples collected.

Repeat steps 7 to 13, 1 m away from the edge of the waterhole.

Clean boots thoroughly between sampling location sites.

Repeat steps 7 to 15 at the second sampling location until all the samples are collected.

Keep freshly collected sediment in labeled, sealed vials at 4°C cold chain (cooler box) until return to laboratory. Soil samples are not recommended to be stored for long periods of time at 4°C.

Once at the laboratory, samples can be stored at -20°C for up to 2 weeks or -80°C for longer periods of time.