An exciting discovery in the depths of the Kimberley Marine Park

Where

Along the Ancient Coastline, a Key Ecological Feature (KEF) within the Kimberley Marine Park, North-west Marine Parks Network.

Who

Researchers from the Australian Institute of Marine Science (AIMS) as part of the North West Shoals to Shore Research Program.

When

April 2019

Why

Little is known about the Ancient Coastline, a Key Ecological Feature (AC KEF) in the North-west Marine Parks Network. At the 125m depth contour, this feature represents the drowned coastline from ~17,000 years ago.

As part of the North West Shoals to Shore Research Program, AIMS is undertaking a study to better understand the nature of the AC KEF, and understand the biodiversity value of the feature. The current designation as a KEF is based largely on sediment data and some information on fish assemblages.

The AC KEF is considered of regional biodiversity value and is also important because it spans areas of interest for oil and gas operations, important commercial fishing grounds, and overlaps two Australian Marine Parks (Kimberley and Montebello).

The AC KEF is thought to provide crucial habitat for sessile benthic taxa (e.g. sponges, corals, crinoids, molluscs, echinoderms and other invertebrates), particularly where it emerges as rocky outcrops in a surrounding environment dominated by soft sediments. It may also be associated with upwelling, important for linking benthic and pelagic communities, and potentially a migratory route for megafauna.

How

Towed video surveys from the AIMS research vessel Solander to characterise the seabed biodiversity on the Ancient Coastline Key Ecological Feature in the Kimberley Marine Park.

What did we learn?

While undertaking routine towed video surveys in the marine park, we noticed lots of what looked like “pom poms” seemingly floating just above the seabed. On closer inspection of high resolution images taken with the towed video, we realised that what we were seeing were fields of benthic siphonopores.

Siphonopores are cnidarians – related to corals and jellyfish – and are usually pelagic. Benthic siphonopores are unique because they anchor themselves to the seafloor with their tentacles, and their bodies float above the surface – hence why they look a little like floating pom poms!

They are generally found in deep water (down to 3000m) and rarely seen; hence why our observation in ~100-150m is so exciting. We think our siphonophore is most likely to be a species of Archangelopsis, although they are very hard to identify from pictures alone.

As far as we know, there have been no other benthic siphonopores recorded in Western Australian waters, and the only other reported observation in Australia was from the Great Australian Bight. This discovery emphasises how little we know about our deep-water ecosystems, and the importance of marine parks for protecting our undiscovered biodiversity.

What next?

To properly identify our species of benthic siphonophore we will need to collect specimens and work with international taxonomists to determine if it was a new species or one that was known from other oceans. This will be a challenge since collecting samples of such fragile animals from depths >100m would require very specialised equipment. In the meantime, we will certainly be looking for more benthic siphonophores on the northwest shelf and in our marine parks.

Our discovery of these rare creatures in the Kimberly Marine Park emphasises how much more we still have to learn about our marine ecosystems, and particularly our marine parks. Given that less than 25% of Australia’s EEZ has been mapped, and considerably less than that properly described in terms of biodiversity, there is a great need for further baseline biodiversity surveys so that we can better understand the values within our marine parks and put in place adequate measures to protect their unique features.

Publications

Read more about the North West Shoals to Shore Seabed Biodiversity and Habitats project.