DNA in seawater can reveal the diversity of fish in the deep ocean

A new study demonstrates the effectiveness of a new method for using DNA in seawater samples to determine which species of fish are present in a given part of the deep sea. A team of scientists from eDNAtec Inc. and colleagues from Fisheries and Oceans Canada and Memorial University present these findings in the open access journal PLOS ONE on November 4th.

The ability to monitor the diversity of deep-sea fish is needed to implement sustainable management efforts and understand the impacts of commercial fishing and climate change. However, existing methods such as bait camera traps, trawling and acoustic tracking have limited detection capabilities and are difficult to use across much of the ocean.

A new method called eDNA metabarcoding reveals which fish are present in a particular habitat by analyzing environmental DNA (eDNA), the DNA that is released by organisms into the surrounding environment as they go about their normal activities.

To evaluate the effectiveness of eDNA metabarcoding for detecting deep-sea fish, McClenaghan and colleagues applied it to seawater samples collected from the Labrador Sea at depths of up to 2,500 meters. In deep sea water samples (depths of 1,400 meters or greater), eDNA coding identified 11 families of fish, 11 genera and 8 species. The researchers compared their eDNA metabarcoding results with those obtained with conventional methods and found that they provided wider coverage of fish and other taxa diversity using significantly less logistical effort. These advantages make eDNA techniques a major advance for large-scale monitoring applications.

The research team also explored the encoding of eDNA using various volumes of deep ocean seawater samples and different DNA primers – short strands of DNA applied in laboratory analysis of eDNA to determine which species are present. Their findings suggest that the deep ocean environment requires some adjustments to methods used in shallower water, such as using larger volumes of water and using more primers to maximize species detection.

While the authors intend to further refine the eDNA metabarcoding procedures for the unique nature of the deep-sea environment, they note that this method may already provide important information for monitoring fish diversity in the deep ocean.

The authors add: “Advances in genomics and computational tools are rapidly expanding our ability to study and monitor biodiversity, a much needed task in the face of rapid and vast environmental changes. Our study demonstrates the usefulness of eDNA analysis. for the challenging effort of monitoring fish species in the deep ocean and lays the groundwork for the adoption of this approach by various stakeholders. ”