“It has always been our ambition to get inside that white space, and now we are there the space can no longer be blank,” wrote the polar explorer Captain Scott, on crossing the 80th parallel of the Antarctic continent for the primary time in 1902. Fast-forward greater than a century – and the deep ocean flooring round Antarctica nonetheless affords a “white space”, past the attain of scuba divers, solely partially mapped intimately by sonar from ships and rarely surveyed by robotic autos.
So I jumped on the likelihood to hitch a crew from the BBC on an expedition to the Antarctic Peninsula for Blue Planet II, to badist them as a scientific information. Thanks to the crew of the badysis ship Alucia, we dived in minisubmarines to 1km deep within the Antarctic for the primary time. And whereas we did not face something just like the bodily hardships endured by early polar explorers on land, these dives did give us the chance for some distinctive science.
The deep ocean round Antarctica is a particular place for a number of causes. Because Antarctica is pushed down by the load of its ice sheets, the submerged continental shelf round it’s deeper than regular, round 500-600m deep at its edge somewhat than 100-200m deep. It’s additionally reduce by even deeper channels shut inshore, some plunging greater than 1km, scoured out by bigger ice sheets up to now. So though the continent itself is distant, we will attain the deep ocean shut inshore right here – useful for us diving in minisubmarines, regardless of the necessity to dodge icebergs.
There’s a gateway to the deep for marine life right here too. Some deep-sea animals come into a lot shallower depths than regular round Antarctica, as a result of the water temperature close to the floor is much like the chilly temperatures elsewhere within the deep ocean. And up to now, shallow-living ancestors of some deep-sea animals unfold out throughout the deep oceans from the Antarctic, by way of this chilly gateway between the shallows and the deep.
One of my favorite animals that we noticed on dives was the octopus Graneledone antarctica, whose ancestor ventured down from the shallows round 15m years in the past, when the water temperature on the floor cooled to the identical chilly temperature because the deep. Her descendants then unfold out throughout the abyss like wagon-train pioneers, giving rise to a number of totally different species of deep-sea octopus discovered around the globe as we speak. Some stayed behind, nonetheless, changing into the species that we noticed.
The ocean round Antarctica can also be the lungs of the deep. Much of the life-giving oxygen in deep waters the world over begins its journey from the ambiance right here. As seawater freezes across the white continent in winter, it leaves behind very chilly and salty water that sinks and flows into the depths of the Atlantic, Indian and Pacific Oceans – even the deepest water within the ocean, on the backside of the Marianas Trench 14,000km away, got here from right here. As this deep water flows out from the Antarctic, it carries oxygen, dissolved from the ambiance on the floor. So the Antarctic is the place the world’s deep oceans breathe in – and its waters are among the many most oxygen-rich on our planet.
Another of my favorite animals from our dives takes benefit of these oxygen-rich waters: big sea-spiders, with legspans as much as 40cm throughout. Sea spiders lack a respiratory system, which often limits their dimension, however can develop a lot bigger within the oxygen-rich situations right here.
‘Ancient ocean ecosystems’
Diving within the Antarctic can also be a journey again in time, to glimpse what historic ocean ecosystems have been as soon as like. Fish dominate as predators in most marine ecosystems as we speak, however few fish species can deal with the -1.5℃ situations the place we have been diving. The “ice dragonfish”, Cryodraco antarcticus, is a notable exception, nonetheless, and one other of my favorite animals – with antifreeze proteins that cease its blood from icing up. Its blood can also be clear, with none of the oxygen-carrying haemoglobin that provides ours its crimson color – within the chilly waters, sufficient oxygen dissolves instantly within the fluid of the fish’s blood to maintain it alive.
But there are few fish with exceptional variations just like the ice dragon, and so invertebrates have diversified to dominate as predators within the deep ocean right here, simply as they did all through the oceans greater than 350m years in the past. A remaining favorite from our dives epitomises that: the Antarctic sunstar Labidiaster annulatus, which is a relative of the acquainted five-armed starfish. Nicknamed “the Death Star” by these contained in the subs who watched its behaviour, it has as much as 50 arms and grows bigger than a dinner plate. It makes use of these arms like fishing rods, holding them up off the seabed to snag pbading krill, due to tiny pincers on its pores and skin that snap shut when something brushes previous them. Unlike different starfish, Labidiaster can wave its arms to catch prey right here as a result of there are comparatively few predatory fish to chew them off.
Overall, seeing the deep Antarctic sea flooring close-up from our minisubs ought to badist us to grasp how “dropstones” form the sample of life right here. “Dropstones” are car-sized boulders that fall from pbading icebergs – they supply “islands” of rocky habitat for filter-feeding species which in any other case do not get a look-in on the tender mud of the Antarctic seafloor. But the place the dropstones settle will depend on the undersea terrain. As we discovered on our dives, they slide down steeper undersea slopes, truly scraping off marine life. But in the event you’re on the backside of a gully, then numerous dropstones find yourself there, giving a significant increase to native biodiversity. That sample of life is tough to see from samples collected by nets or trawls up to now, so our first minisub dives to 1km deep within the Antarctic ought to badist to make that “white space” not such a clean.
Jon Copley, Associate Professor in Ocean Exploration & Public Engagement, University of Southampton
This article was initially revealed on The Conversation. Read the unique article.