Knowledge gaps in deep sea habitats.
The deep sea is the largest habitat in the world and, due to logistical challenges, most of this area remains to be mapped and sampled for biodiversity. This means we have limited knowledge about seafloor geomorphology, what the various seafloor features are made of, and what species live in these habitats and how far their ranges extend. What we do know is that the seafloor and the species that live within this habitat are threatened by human activities, such as extraction of fossil fuels, trawling, and burning of fossil fuels leading to changes in ocean chemistry.

Recently mapped Lexington Seamount that is 40 km in length and from 1,000 m to 4,000 m in depth

Why is it important to overcome these knowledge gaps?
There are important reasons for improving our understanding of the deep sea. Firstly, understanding biodiversity allows us to identify the ecological and evolutionary processes that maintain biodiversity patterns in this vast habitat. These are the processes that conservation actions need to target to make a difference in the face of increasing detrimental human activities. Therefore, biodiversity data are required to make informed conservation decisions. Secondly, although humans as a society are moving towards using more renewable energy sources, it is a misconception that renewable energy will release us from our dependency on mined resources. Although wind, sun, and water energy are renewable, the mechanisms that convert them into stored energy require specific elements derived from mineral resources like ferromanganese crust, polymetallic nodules, and polymetallic sulfides. These metal resources are found in some of the highest concentrations in, you guessed it, the deep sea. Different deep sea habitats contain different amounts and types of resources, with advanced 3D mapping and sampling being the only ways to identify what deep sea features consist of. Expecting an increased demand for these resources, more information about the deep sea will allow us to manage mining activities in the ocean to minimise their adverse impacts.

Azooxanthellae scleractinian coral

On board the RV Investigator.
These are two of many aims of the RV Investigator Voyage ‘Hotspot dynamics in the Coral Sea: connections between the Australian plate and deep Earth’. We are two weeks into our one-month voyage, and we have already obtained new information about deep sea habitats and what lives within them. We have swath mapped ten seamounts that were known but never mapped in such detail before, and have sampled rocks from these seamounts to determine the quantity and type of precipitated elements. Additionally, we are collecting, sorting, identifying, and preserving the biological life, which has already led to the identification of dominant deep sea benthos like gooseneck barnacles, diverse gorgonian sea fans and precious corals. Additionally, we found a fresh brachiopod shell, which is considered a ‘living fossil’ of a once common mollusk in the Paleozoic Era. We have also found at least one likely undescribed species of glass sponge that is dense as a rock and made of pure glass. With two weeks more to go, there is no telling what new information we might collect. What we do know is that this new information will be used to update our knowledge of deep-sea species and better prepare ourselves for the sustainable management of future resources of interest in areas where mining activities are permissible.

This research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Special thanks to Dr. Karin Orth and Dr. Rob Beaman for their insights on this topic.

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