Aliens

500 metres beneath Antarctica’s Ross Sea lurks a strange and largely undescribed variety of life.

Written by James Frankham Photographed by Darren Stevens, David Bowden, Stefano Schiaparelli and Peter Marriot

Viewed from the radar mast of the NIWA research vessel Tangaroa, the Ross Sea is a patchwork of shattered floes. Covered for nine months of the year in a crust of ice up to two metres thick, channels form in summer triggering an explosion of phytoplankton that rains detritus and nutrients through the water column into the depths beneath. These depths are a cold and unusual environment for life, an alien universe of creatures dependent on this hail of food in the summer, and devouring one another when the ice returns. On this voyage, the Tangaroa carried a multibeam echosounder, towed video and still cameras, trawl nets, a specialised benthic sled for sampling creatures living just above the seafloor, and a slew of equipment to collect plankton and measure salinity, temperature and chlorophyll levels

As the remote camera gear slipped through the thrashing surface of the Ross Sea on the first tow of the first survey day in February 2008, scientists could only speculate as to what they might find—it is probably the most remote and least understood tract of ocean on the planet, and this was deeper and farther south than they had ever surveyed before. They had a formidable arsenal of tools at their disposal—new imaging technologies and state-of-the-art collection sleds to reveal the clearest picture of this environment yet. The expedition was a collaborative effort between NIWA and Te Papa and also part of a massive international effort, the Census of Antarctic Marine Life (CAML), described as one of the most important pieces of research currently being undertaken in the world.

The monitors flashed to life in the small lab on the main deck of the Tangaroa, and the lights on the camera tethered 500 m beneath illuminated the gloom. A dozen scientists, packed like sardines in a tin, leaned forward, squinting at the unremarkable darkness on the closed-circuit television screen. A vast bed of sponges appeared, and then life in profusion. Life, but not as we know it.

Reef-building Bryozoans and gorgonian corals, huge glass sponges and swimming feather stars filled the lens, interspersed with bizarre-looking sea cucumbers and giant starfish—all quietly, diligently going about their business.

As the scientists moved further north to the Scott seamounts, the sea life changed. There were fields of half-metre-tall sea lilies bent like date palms in the wind—these were abundant in the world’s oceans during the Palaeozoic period, and crinoids of this size and density are not known to exist anywhere else on the planet today. Delicate hydroids spun in the current like whirling dervishes, their satin tentacles fishing for nutrients in the darkness like a million sticky fingers.

“All of us were gobsmacked,” says Stuart Hanchet, lead scientist on the project. “It was the first time we had used video of that quality and seen such an amazing array of benthic fauna just drifting under the camera.”

Plunderfish belong to a larger group of antifreeze-bearing fishes that first appeared in the Southern Ocean 25 million years ago. The plunderfish family (Artedidraconidae) comprises 26 species found only in Antarctic waters. None have scales, or a swim bladder—common in most other fish—and instead live sedentary lives on the seafloor. They attract prey using a chin barbel. This particular species is found at a depth of 200–700 m around the coast of Antarctica and is considered rare in collections. During the voyage, 13 specimens were caught, including one over 20 cm long, which is the biggest known.

When the climate of Antartica and the Southern Ocean dramatically changed 40 million years ago to create the conditions we see today, most of the fish species living in the region became extinct. Skates, however, were survivors because they are not fussy about their diet and habitat. They are also extremely cold-tolerant. This skate species, previously unknown to science, is endemic to the shelf and upper slope around Antarctica, and is very large, growing to nearly 1.2 m. Divers in the Ross Sea have observed it in shallow water, but it occurs down to depths beyond 1400 m

Within days, NIWA researchers had scooped up a species of deepwater octopus new to science, a chiton more like a military tank than a crustacean, and a brilliant pink amphipod that had never been seen before. “It was the sheer abundance of invertebrate life that was most exciting,” says Hanchet. “You had the feeling that you were looking at a pristine environment.”

Much of the Ross Sea is a shelf 400–600 m deep, but there are shallow banks as well as profound troughs that descend 1200 m into the blackness. Further north lies the steep continental slope dropping down to abyssal depths interspersed with seamounts. It is this diversity of habitat that generates the diversity of marine fauna.

A deep-sea slater, striated by brown ridges like a flounder caught in a panini grill, brittle stars with 400 “arms” instead of five, and grotesque lumps of goop called sea pigs reminiscent of inflated surgical gloves were plucked from the depths by a benthic sled and delivered, still flapping, to the on-board lab. This was spine-tingling science, as close to the frontier as the work of Joseph Banks 240 years ago and, arguably, just as important.

Many of the new species are small crustaceans, which are abundant in the Antarctic marine environment and are such a large component of the food chain that they determine the health of the entire ecosystem.

As one of only two “embayments” on the continent (the other being the Weddell Sea), and with unique underwater features, the Ross Sea is an important habitat for Antarctic marine life and “exports” large quantities of biomass into the surrounding Southern Ocean either by natural dispersal or as food for baleen whales, seals and penguins. The cold, saline waters of Antarctica literally fall down the continental slope, creating deep currents of oxygenated water which flow north to feed the largest oceans of the world, passing on the nutrient wealth of the Ross Sea and adjoining regions to the benefit of the marine ecosystems of the entire planet.

AMPHIPODS: Small crustaceans known as amphipods are among the most abundant animals found under the ice. Devoured in the billions by all manner of marine species, amphipods are also prolific carnivores in their own right. Living below the depth of algae or in the eternal twilight under the ice, they rely on scavenging, tearing chunks off larger animals or predating on critters smaller than themselves. Who would think hot pink was an appropriate colour for a deep-sea critter? Well as it happens, no one, until NIWA fished up a new micropredator, Epimeria larsi, from the Ross Sea. ISOPODS: Just as the land hosts woodlice, the marine environment hosts isopods as well—some 4500 species found mostly on the seafloor. Caecognathia calva is a blood-sucking parasite that lurks in anemones and attaches itself to the heads of bottom-dwelling fish. CRABS AND SEA SPIDERS: Three species of king crab are known to inhabit the Ross Sea and two of these were only recently discovered. Neolithodes yaldwyni has a massive 80 cm leg span and straw-like mouth parts which it inserts into prey so it can suck out their juices. The smaller-bodied sea spiders have such a large surface area-to-volume ratio that they don’t need gills at all, absorbing oxygen directly through their bodies. Ostracods are also crustaceans which are enclosed within two shells. Gigantocypris is one of the largest and, living in mid-water, is equipped with a leg which it uses to swim.

MOLLUSCA — CEPHALOPODS: Nearly a quarter of all named marine organisms are molluscs—around 93,000 species. Cephalopods such as octopus, squid and cuttlefish are easily the most intelligent of this group and among the most neurologically advanced of all animal species—they display distinct emotions, use tools and can recognise individuals. The Ross Sea region is also famous for the largest of the group, the colossal squid, which is preyed on by sperm whales, and is also home to very deep-dwelling octopi in two groups—the incirrate octopus, which is the type that most people are familiar with (such as Benthoctopus), and the cirrate, or dumbo octopus, which has finger-like “cirri” along the underside of all the arms, a gelatinous body and webbed arms. Stauroteuthis gilchristi is a very rare dumbo octopus found in waters 900–3000 m deep—a range not often sampled. Like other octopi, it has three hearts, blue blood and is relatively short lived, dying soon after reproduction.

CNIDARIA & WORMS — ANTHOZOA, SCYPHOZOA, CUBOZOA, HYDROZOA: Despite their floral appearance, all cnidarians—corals, jelly-fish, anemones and hydroids—are equipped with stinging cells called nematocysts that inject paralysing venom into prey. Some cells are so potent they are even dangerous to humans. Hydroids like Siphonophora orderare colonial cnidarians, composed of many “zooids” that look and behave differently—some act as swimming bells, others are dedicated to food collection or reproduction—but all benefit the whole colony. The Pennatulacean is an organism that lives half-buried in the mud, leaving just the feather protruding. This rotates according to the current, while polyps at the tips intercept food particles. ANELLIDA AND NEMERTEA: Worms are seabed scavengers, depending on food transported from the surface where there is enough light to support photo-synthesis by phytoplankton. Paleonemerteans are voracious micropredators of other invertebrates and may form large aggregations to feed on carcasses of animals on the seafloor. Both the body and mucus of Chaetopterus are luminescent, a biological peculiarity that remains a mystery.

ECHINODERMATA — SEA STARS: Sea stars are composed of a central disc from which arms sprout in perfect radial symmetry. Macroptychaster sea stars astonished researchers when they were hauled onto out of the benthic sled—they were the size of a manhole cover! Like all sea stars, they possess two stomaches, one for digestion, the other to extend outside its body to engulf and digest prey too big for its mouth. BRITTLE STARS, BASKET STARS: Unlike sea stars, brittle stars move rapidly by wriggling their arms, which are highly flexible and enable the animals to make sinuous or rowing movements. Echinoderms (including sea urchins and sea cucumbers) have skeletons of calcium carbonate that make them sensitive to oceanic acidification resulting from climate change. Basket stars (like Gorgonocephalus) crawl up rocky promontories and form a basket with their arms to catch zooplankton and larger particles.

Three years of analysis is yet to come, which will make sense of the apparent madness beneath the ice. The research is focused on finding regions of exceptional biodiversity, on trying to understand which eats what, and on establishing baseline data so we have some idea of the abundance of species. These are the very first steps in understanding the basic functioning of the Antarctic marine environment and will help scientists with more complex tasks such as predicting the impact of climate change or the effect of fishing—such as the now well-established fishery for Antarctic toothfish, which is reaching its catch limits of 3000 tonnes a year from the Ross Sea.

“If you remove a predator from an ecosystem, or at least reduce the population, what’s the effect on the rest of the ecosystem? Until we understand the basics we can’t know,” says Hanchet. “The more we know about biological processes, what lives where and why, the more we can identify the important areas and protect them.”

The voyage of NIWA’s Tangaroa into the Ross Sea in 2008, and subsequent research into the bounty it retrieved, cost the New Zealand taxpayer $6.6 million.

Of the 16,000 species of marine life identified in New Zealand waters, we commercially harvest just 130 of them, a total fishery worth $3.8 billion every year. So what’s the discovery of a new species of amphipod worth to New Zealanders? Probably nothing. But what value do you put on understanding the biodiversity of Antarctica, one of the most important hubs of marine biomass on our blue planet? Pick a number; millions, perhaps billions. And if you believe the ecologists, it may be priceless.