Drones can help coral
Scientists are uncovering the mysteries of deep coral reefs with underwater drones and eDNA
Researchers are using underwater drones to learn about mysterious mesophotic coral ecosystems (MCEs) – low-light habitats in tropical and subtropical regions made up of coral, sponges and algae. Because MCEs are found at depths of 30-150m, which is beyond recreational scuba-diving limits, they are very hard to study. So, Noriyuki Satoh and his team at Okinawa Institute of Science and Technology and NTT Communications in Japan have trialled the use of underwater drones to collect seawater samples and analyse their environmental DNA (eDNA). The aim is to find out which types of stony coral are present.
As organisms shed cells, mucus or faeces, they leave traces of eDNA behind. By analysing these, scientists can identify what creatures are present, even if they haven’t observed them. eDNa is already used to study marine animals in shallow coral reefs.
The researchers collected samples at 24 sites in the Okinawa Archipelago – a region known for its clear waters and diversity of stony corals. Initial findings have identified coral at genus level and shown that the reef composition varies according to depth. Acropora corals, for instance, were more common in shallower reefs; Porites were more common in the MCEs.
Satoh hopes the use of underwater drones will help researchers learn more about MCEs. These reefs are home to a higher proportion of endemic species than their shallow counterparts, so knowing how they function is vital to keep the ocean healthy. Melissa Hobson