Shedding the full spectrum of light on sea ice communities at Cape Evans, Antarctica

The view looking up from the seafloor to the underside of the sea ice shows a landscape that has been experienced in real time by only a few people on the planet.

Broad meadows of sea ice algae span as far as the camera on the remotely operated vehicle can see.

An IMAS team of researchers - Dr Vanessa Lucieer, (pictured, right, with algae-covered sea ice. Photo: Emiliano Cimoli)Dr Andrew Martin, PhD student Emiliano Cimoli, Fraser Kennedy and engineer Richard Ballard - spent twenty-two days at Cape Evans on the Ross Ice Shelf in Antarctica during November investigating these meadows.

The project jointly funded by the New Zealand Antarctic Research Initiative (NZARI) and the Australian Research Council funded Antarctic Gateway Partnership (AGP) aimed to deploy state of the art under-ice surveillance systems to track the abundance and physiological status of sea-ice microbial communities.

The team’s fundamental goal was to assess the current state of this key Antarctic community and contribute baseline knowledge against which future change in ecosystem structure and function can be measured using new fine scale long range techniques.

Emiliano Cimoli & Vanessa LucieerOver the past two years Mr Cimoli and Dr Lucieer (pictured, left, photo: Michael Bollen) have been working towards the world’s first deployment of a Hyperspectral Imaging (HI) camera under sea ice in Antarctica.

As with all ambitious projects it was accomplished with the support of larger team, involving Arko Lucieer (UTAS), Klaus Meiners (AAD), Lars Christian Lund-Hansen (Aarhus University, Denmark), Ken Ryan (Victoria University of Wellington), and Ian Hawes (University of Waikato).

Mr Cimoli said the HI camera is designed to compose an image that comprises the full spectrum of light and goes beyond the range visible to the human eye.

“These dense data “cubes” composed from the scans can tell us about the chlorophyll content on sea ice and therefore ice algal abundance at very finite, millimetre-scale resolution,” Mr Cimoli said.

“Current techniques to collect this data involve collecting sea ice cores at point locations and interpolating these data to create area estimates.

“The width of the HI camera scan is around 5 cores which, when run along ~20 m transects, can collect the equivalent of thousands of ice cores remotely, without having to “touch” the sea-ice.

“These data “cubes” information can be also be baselined with other techniques such as HPLC (High-performance liquid chromatography) and pigment absorption for further understanding whether the algal cells are happily photosynthesising or experiencing light associated stress,” he said.

Dr Lucieer said that in the preliminary field campaign of 2018 the hyperspectral camera system was tested in two separate experiments.

Underwater camera on sea ice“The first experiment was a replication of lab techniques of scanning the bottom 3-centimetres of an ice core freshly harvested from the field site,” Dr Lucieer said.

“Using a second camera, the ice surface microstructure was captured using a technique called structure from motion, which creates a 3D surface of the ice crystal surface.

“Using this technique, we can examine the relationships between the ice structure and algal biomass.

“The second experiment involved enclosing the camera system, along with the company of a standard RGB camera and TRIOS light sensor into an underwater housing.

“Using an ROV to establish a tow line beneath the sea-ice, we created a sort of underwater cable car (pictured, above, photo: Vanessa Lucieer).

“This design was crucial for full control of the system to understand the speed and settings the camera required to be moved along the sea ice capturing accurately georeferenced images.

“All this information will be implemented in the engineering design for the second field trial in 2019,” Dr Lucieer said.

Click to watch a video of the Cape Evans research.

The team is working towards a rapid deployment system that can be mounted on a remotely operated vehicle to be deployed through a small 1x1 metre ice hole with the capability to capture transects over tens of metres.

This new remote sensing method will revolutionise our understanding of sea ice communities, which are fundamental to the base of the Antarctic food web.

Through the collaborations between international institutes spanning multiple disciplines such as Antarctic biology, remote sensing, polar engineering and spatial analyses, IMAS is becoming the epicentre for teams to come together to improve global knowledge of these vital Antarctic communities.

Authorised by the Executive Director, Institute for Marine and Antarctic Studies
28 October, 2022