Like a gold miner crouched on the bank of a stream, shoveling sediment into his pan and hoping for a golden glint to catch his eye, we stood at the edge of a washing table, placing scoops of reef sediment onto our stack of sieves. However, we’re interested in something far more minuscule. Our collection of five sieves, with mesh sizes ranging from 63µm to 2mm, helps narrow the search by partitioning the sediment by particle size. Large pieces of dead coral and shell remain on the top mesh screen, while the smaller particles fall through and are caught by the finer mesh. Denticles are approximately 100µm to a little over 1mm across, so we process the 106µm-2mm size fractions to find them, saving both time and acetic acid. The very largest (>2mm) and smallest (63-106µm) fractions are stored in the lab for future use.
With two people working simultaneously, each 8-10kg sediment sample takes around two hours to sieve. After sieving, each size fraction is placed on a separate tray and deposited in our ‘drying bubble’ for a day or two until completely dry. It is then either digested with acid or stored. With one to two samples sieved per day, our mountain of bulk bags is gradually dwindling.