Summer Series #8 - Spectacular Scenes Under The Ice

In October a team of scientists from New Zealand and Finland travelled to Antarctica for a scientific diving expedition under the ice.

Led by NIWA marine ecologist Dr Drew Lohrer, the aim of the expedition was to explore how climate change is affecting the marine biodiversity in Antarctica. A unique combination of species and isolation has provided an area largely unaffected by human activity.

The divers found that there have been surprisingly big changes in the coastal seafloor communities in just a few years.

“What used to be a very stable, sparse and food-deprived animal community on the seafloor under the thick ice in New Harbour is now much richer with more species and higher densities of animals,” Dr Lohrer said.

New Harbour sea ice can go for years without breaking out, and this multiyear ice can grow up to 4.5 meters thick. When the ice is thick, very little light can penetrate the ice to fuel primary production (for example algae) and therefore food supply to the animals on the seafloor is limited.

The rich community now observed is most likely a rapid response to the sea ice breaking out two years in a row, resulting in more light and higher productivity in the ecosystem.

While under the ice divers captured spectacular images of the creatures they saw which they will use for further study.

University of Auckland PhD student Jen Hillman with a small catchbag and PVC barrel contain samples. Her tether (attached to her and an above-ice anchor point) extends upward to the main hole. An alternate or “safety” hole (upper left) is about 25m away. The sea ice at this site (Explorer’s Cove, New Harbour) was 3.5m thick, and the depth of the seafloor about 19m. PHOTO CREDIT: Peter Marriott.

Divers Drew Lohrer, left, and Peter Marriott (right), both of NIWA. In the foreground is an array of benthic incubation chambers used for assessing seafloor organic matter remineralisation rates, along with scallops, brittle stars, sponges and other species. PHOTO CREDIT: Science Under the Ice team (screen shot from BoxFish 360 underwater VR camera).

Water samples were collected from the benthic incubation chambers twice and day, after which they were processed in the “laboratory”. Drew Lohrer and Jen Hillman make measurements, record data, and filter samples. About 300 filtered seawater samples were frozen and brought back to NIWA Hamilton’s analytical chemistry laboratory for analysis. PHOTO CREDIT: Patrick Degerman.

Brittle stars living at the freezing point atop “anchor ice”. Anchor ice is relatively common in the shallow areas of New Harbour near where the sea ice meets dry land. Anchor ice sometimes envelopes and kills seafloor organisms that cannot or do not move away in time. PHOTO CREDIT: Peter Marriott.

A large Polar Haven tent, used for eating and meal preparation. A team of nine camping for 20 days requires a lot of food. Red food boxes with dry goods, chilly bins of frozen meats and veg, and LPG bottles for the stoves are lined up outside the tent in an orderly fashion. This was one of three heated huts at camp. The team slept in unheated tents atop the sea ice. PHOTO CREDIT: Patrick Degerman

Brittle star partially encased in anchor ice crystal in the shallow marine environment of New Harbour. PHOTO CREDIT: Patrick Degerman

A pencil urchin covered in epibionts including a large sea squirt (left) and several varieties of sponge. The image was captured at about 15m depth at New Harbour. PHOTO CREDIT: Peter Marriott.

The team called this shell-less snail friend Doris, after its scientific name, Doris kergulensis. The image was captured at approximately 15m depth at New Harbour. Photographer Peter Marriott

The urchin Sterechinus neumayeri encased in anchor ice crystal in the shallow marine environment of New Harbour. This species of urchin is very common at many sites in McMurdo Sound and in fact has a circum-Antarctic distribution, but it was relatively uncommon at the sampling site. PHOTO CREDIT: Peter Marriott.

The extraordinarily large (more than a metre long!) nemertean worm, Parborlasia corrugatus. It is a hungry scavenger and predator, and has probably found something tasty to eat (perhaps a scallop, to which the feathery-looking bryozoan is attached). PHOTO CREDIT: Peter Marriott.

© Scoop Media