Sediment sampling protocol

During sediment sampling, precautionary (anti-contamination) measures include the use of two pairs of medical gloves (nitrile over latex), surgical (FFP-3-rated) respirators, a face-mask or visor, clean shoe-covers and biologically-impervious full-body suites (Class 3). Soil samples should be retrieved via sterile (DNA- and RNA-free) 15 ml centrifuge tubes (e.g. Greiner Bio-OneGmbH) from ˃6.0cm inside vertically exposed stratigraphic sections. This is achieved by clearing a ~1.0cm deep by 5.0cm wide vertical trench along the exposed surface and then coring, using a triangular stainless steel spatula matching the diameter (i.e. 2.0cm) of the sample tubes, into the exposed surface for 5.0cm. Sediment samples are extracted from respective stratigraphic units in situ (i.e. by inserting the sampling tube into the cored cylindrical cavity) and must be immediately sealed and frozen (at c. 4°C). Samples are taken from the bottom of the cleared trench towards the uppermost units as this limits contamination (by falling sediments and debris) from younger sediments. All the equipment used (stainless steel picks and spatulas) must be routinely decontaminated with ethanol swabs and a surface decontaminant such as DNA Away. Ideally, samples should be recovered from newly -excavated sections as this precludes the impact of microbial activity brought about by long-term environmental exposure.