When marine animals, plants and algae pass through seawater, they leave a trail of environmental DNA (eDNA) such as fluid, scales, skin and other bits and pieces that slowly break down. Our project includes eDNA analysis of seawater samples from different locations and depths to generate a snapshot of life in the ocean.
Rob Ogden at the Roslin Institute (where Dolly the sheep was cloned) provided the kit and protocol and will lead the genomic analysis when our samples arrive back in Edinburgh – this will be the first study of its kind for the Pitcairn Islands Marine Reserve.
So far, we’ve sampled the waters over Adams Seamount (40-Mile Reef) and off Henderson Island. In a few days, we plan to take more samples at Oeno. Each day begins with us on a RHIB skidding across the Pacific swell to a random sample site. We have a GPS so we can return to the same area and sample at different depths, a Niskin bottle to collect our water samples, and a sensor that measures water depth, temperature and salinity.
We fix the bottle and sensor to a line and drop them off the boat-side until they reach the right depth. We then drop a weight down the line to hit a trigger that closes the bottle and captures the seawater, then we haul the line to the surface and safely store the water.
Images: eDNA sampling with a Niskin bottle from a RHIB. Photo by Murray Roberts
We take the samples back to the ship and pass the water through ultra-fine filtration columns that trap fragments containing DNA.
Images: eDNA filtration. Photo by Murray Roberts
The filters are frozen and will be taken back to the lab in Edinburgh, where DNA barcoding will reveal the identity of marine species recently present in each area. This pilot study will target different groups of vertebrate, invertebrate, plant and algal species. This cutting-edge genomic analysis will help us build a picture of the marine biodiversity around the Pitcairn Islands.