The Deep Sea: Australia’s largest yet least understood environment

The net is winched on board. Corals, crabs, sea cucumbers, sea urchins, starfish and worms are bundled up inside the netting, all trawled up from around 1000 m deep.


In November last year (2018) I was onboard the Research Vessel Investigator with a team of other researchers from across Australia, processing deep-sea trawl samples in the Southern Ocean. We were sampling fauna from seamounts and associated cold-water coral communities. The aim was to map cold-water corals and their associated marine life on Tasmanian seamounts. The sites sampled were in two of Australia’s sixty Marine Parks, the Huon and Tasman Fracture Marine Parks, under a day's boat journey south of Tasmania.


Trawl catch collected from Tasmanian seamounts (1000 m depth) on RV Investigator. Image: Ingo Burghardt

Australia is a big country, with an even larger marine territory. Indeed, Australia has the third largest marine territory in the world, covering an area 2.5 larger than the Australian land mass. Marine Parks cover 36% of the marine territory, 3.3 million square km. Under the UN Convention on the Law of the Sea, Australia has the obligation to manage its offshore territories, from shallow waters to deep seas. Failure to manage its area could mean ownership is revoked. Australian Marine Parks were established to protect and manage the biological diversity within these habitats.


But – how much do we know about what lives in the deeper areas of Marine Parks?


Answer…not very much!


The deeper areas of Australia’s marine territory including Marine Parks have been poorly sampled for fauna and lack wide-covering, taxonomically consistent datasets. The current boundaries of Marine Parks beyond shelf depths are based mainly on physical surrogates, such as seabed geomorphology or depth. Distribution data on fishes, and limited data on sponges, were the only biological data available when Marine Parks were being established.


Recent research on deep-water octocorals indicates that Marine Parks appear not to encompass areas of significantly higher biodiversity compared with areas outside the reserves (Althaus et al. 2017). This suggests that Australian Marine Parks may not adequately protect our deep-sea biological diversity.


Map of Australian Marine Parks. Image: Parks Australia

The large gap in our taxonomic knowledge of Australia’s deep-sea fauna is especially evident for marine invertebrate groups. Poore et al. (2015) noted that around 95% of crustacean species and 72% of polychaete (segmented worms) species from the deep waters (50 - 1073 m) off the western Australian continental margin were undescribed. Preliminary investigations on deep-sea material from the eastern Australian lower bathyal and abyss (2500 - 4000 m), ranging from Tasmania to Southern Queensland, indicate that at least 80% of polychaete species may be new to science (Gunton et al. 2018).


Many of the samples in the nets we hauled from seamounts in the Huon and Tasman Fracture Marine Parks will be species new to science. At the Australian Museum, Museums Victoria, Tasmanian Museum and Art Gallery, University of Tasmania and CSIRO we are working on describing these new species, knowledge that will help us to better manage and protect these communities for the future.


Watch this space for new species descriptions from the deep.


References


Althaus, F., Williams, A., Alderslade P., Schlacher, T.A. 2017. Conservation of marine biodiversity on a very large deep continental margin: how representative is a very large offshore reserve network for deep-water octocorals? Diversity and Distributions, 23, 90-103.


Gunton, L. M., Kupriyanova, E., Hutchings, P., Wilson, R., Murray, A., Paxton, H., Burghardt, I., Zhang, J. & O’Hara, T. D. 2018. Polychaetes from Australia's Eastern Abyss. 15th Deep-Sea Biology Symposium. Monterey, California.


Poore, G. C. B., Avery, L., Blazewicz-Paszkowycz, M., Browne, J., Bruce, N. L., Gerken, S., Glasby, C., Greaves, E., McCallum, A. W., Staples, D., Syme, A., Taylor, J., Walker-Smith, G., Warne, M., Watson, C., Williams, A., Wilson, R. S. & Woolley, S. 2015. Invertebrate diversity of the unexplored marine western margin of Australia: taxonomy and implications for global biodiversity. Marine Biodiversity, 45, 271-286.

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