Marine biologist Joe Marlow spent a year working as a research diver at the British Antarctic Survey station at Rothera. In this featured from our Winter 2020 print issue, Joe recounts the unique lifestyle in a wilderness few will ever visit, with a stunning set of the photographs he captured.
Antarctica, the final continent to be discovered by humankind, is one of the last wildernesses to exist in our rapidly changing world. The continent has no permanent inhabitants, and very few of us will ever visit the place, let alone peek beneath its freezing sea.
Perhaps unsurprisingly to many, the idea of submerging yourself in the icy continent’s frigid waters is tantamount to insanity. However, as a marine biologist, I have been fascinated by the polar regions for years. I specialise in benthic ecology, the study of life on the seabed (rather than the water column), and nowhere else on the planet does life on the seabed face such seasonal extremes. Summer is characterised by open seas, relatively warm water, 24 hours of sunlight and intense phytoplankton blooms. Conversely, in winter, the ocean is frozen, barren and shrouded in darkness.
Climate change is altering a lot of these norms. Both winter sea ice extent, and summer phytoplankton bloom intensity, are decreasing on the Antarctic peninsula. To understand how these changes will affect life on the seabed, I have spent the past year living and working at Rothera, the British Antarctic Survey’s (BAS) research station. It is the only research base to conduct diving operations year-round in the Antarctic. Or, rather, to attempt to dive year-round, because as I quickly discovered, getting into the water in Antarctica is not always a straightforward matter.
I arrived at Rothera in early December 2019. By this point, much of the winter sea ice had disappeared and the sun was not due to drop below the horizon for another six weeks. The sea was a perfect blue, almost impossibly clear and looked incredibly inviting. However, it was also minus-one degree Celsius, which requires a hell of a lot of gear just to keep you from freezing to death. Consequently, my first dive was a bit of a learning curve. Wearing a thick undersuit, a crushed neoprene drysuit, two tanks, 18 kg of weight and full-face mask with communication cables running to the surface, I felt more like the Michelin Man than a svelte diver.
As I clumsily descended towards the seabed, the first thing that struck me (apart from the piercing cold) was how barren it was. The water column was devoid of fish, and at ten metres’ depth, the rock bottom was desolate with except for the occasional limpet or sea urchin. It turns out that existence is not easy for marine life in Antarctica; very few fish have evolved the antifreeze-like proteins needed to stop their blood from freezing. For life on the seabed, only the highly mobile are able to survive in a zone constantly scoured by immense icebergs.
However, as I descended deeper, more life started to appear – the odd sea anemone here and there, carpets of red algae playing host to numerous sea cucumbers and eventually, large sponges festooned with sea squirts and predatory nudibranchs. At these depths (usually beyond 25 metres), iceberg strikes are less common, and more immobile and slow-growing flora and fauna can flourish. In December, this was the middle of the Antarctic spring, and although water visibility was still good, we were in the early stages of the summer bloom, with phytoplankton beginning to grow in the water column. As a consequence, many of the animals that feed only in the summer had come out of their winter dormancy. Soft corals, sea cucumbers and tube worms all had their tentacles projecting into the water, ingesting some of their first food for nearly six months.
All too soon, my first dive was coming to an end, not due to bottom time nor air, but because of the cold. Our suits and hoods do a good job of keeping us warm, but even with 7mm neoprene mitts, my hands were numb to the point of being almost useless after 40 minutes underwater. On the surface, I experienced for the first time the joys of ‘rewarming pains’ and the nausea that can accompany this. Keeping my hands warm was to become a new mission in life, and something that I am still working on, almost a year later.
Summer in Antarctica is a hectic period, both for the native wildlife and human visitors. For us scientists, the most reliable time to get in the water is during a short period from January to March. Either side of that, weather and ice make diving (or even leaving the comfort of your building) somewhat tricky. The station swells to more than 160 people, and the research laboratory hums with the various visiting scientists who hope to collect all their data during their short stint on the ice.
This is also a very busy season for the ocean, and in a few short weeks, the spectacular visibility that I experienced on my first dive has given way to a murky green soup, in what is one of the most intense phytoplankton blooms on the planet. Visibility drops to near zero and, with a dense carpet of phytoplankton above your head, any dive below about 25m feels more like a night dive and requires a torch. The water temperature also rises to a balmy 1.8 °C, which now feels positively toasty. However, this is probably due to the fact that I’ve become fanatical about keeping my hands and gloves as warm as I can before a dive. It is amazing how cosy neoprene can feel if it’s sandwiched between two hot-water bottles.
Not only does the phytoplankton bloom make scientific diving a little more complicated, but the abundance of food does also bring in some unwelcome guests. As the local bay teems with wildlife, the Antarctic’s top predators, orcas and leopard seals, also begin to become common sights. Seeing one of these animals in the flesh is a fantastic experience, but the safety of divers is taken very seriously by BAS, and the sighting of these predators puts an immediate stop to all diving activities. This can be frustrating – leopard seals, in particular, have an uncanny ability to be found lounging on an iceberg just adjacent to your dive site.
The summer season flies by, and although I became accustomed to the 24 hours of sunlight surprisingly quickly, it is a welcome sight to see the sun finally set for the first time in almost two months. By mid-March, the reduction in daylight hours and intense grazing by krill has finally started to influence the phytoplankton bloom. The water slowly begins to return to its former blue self, and with the increased visibility I find myself spotting critters that I hadn’t previously been able to see in the gloom, such as small isopods that cling to whip corals, and tiny colourful nudibranchs among the algae. Not all the critters are small, though. I am shocked when I see my first Antarctic sea spider marching across the seabed, as it’s almost 20cm across! Elsewhere, I would expect them to be no bigger than my fingernail, but here the cold, oxygen-rich water and their slow metabolism allow them to grow to gigantic proportions.
With some dive sites, it is the first chance I have had to see them without looking down the beam of my dive torch. Dark wall sites that were previously cloaked in shadows come alive – overhangs on these walls offer shelter from the destructive forces of passing icebergs and are encrusted with sponges and sea squirts, that are larger than can be found anywhere else at diveable depths. The water temperature is also beginning to drop, and for the first time, we start to see ice form on the water surface on cold days. This ‘grease ice’ resembles more of an oil slick than thick ice and doesn’t stop us from getting out on the water. That is not to say that ice isn’t a problem at this time. Even in summer, southerly winds can bring in flotillas of ‘brash ice’ (fragments of ice that are the wreckage of old sea ice or glaciers), which can choke the local bays and prevent us from putting a boat in the water.
Winter begins in early May. For those of us who are staying on base during this period, it is a huge transition; the personnel numbers on the station slowly dwindle from the summer high to just twenty-seven of us when the final ship leaves. We won’t see another person for at least another six months, and in the heart of winter, we won’t be able to see the sun for eight weeks.
For the marine science team, it’s an exciting yet difficult time of the year. As both water and air temperatures drop, grease ice becomes increasingly prominent. Given the right conditions of prolonged low temperatures and wind, it can form ‘fast ice’, which we can travel on and dive through. In reality, it takes weeks to get to this point, as the ice-forming process is interrupted by spikes of high temperatures or high wind, and the ice is broken into little ‘pancakes’, or blown away altogether. During this period, the ice is neither solidified enough for us to walk on nor soft enough to drive a boat through, so most of June and July is spent onshore, waiting.
It is a frustrating time, but when the wait is finally over, the first trip out on the sea ice is an incredibly rewarding experience. To be standing above what you know to be 20-plus metres of seawater and seeing the base from an orientation that you have only ever previously encountered from a boat is peculiar beyond words. These first trips are to check the ice thickness and assess whether it is safe to drive our Ski-doos over it – if we’re going to go through the ice, it will only be on our terms.
When we finally cut our first ice holes in late July, the sun has barely reappeared above the horizon, and the holes look like inky black wells on the ice surface. Descending through the holes, it doesn’t get any lighter – we have 50cm of ice and snow above our heads, and despite the crystal-clear visibility, it is so dark that we can barely see a thing. After our eyes have adjusted to the darkness, it becomes very apparent that we have cut our ice holes next to an immense iceberg. At the surface, we barely registered it as a small lump in the sea ice, but underwater we estimate it to be 30-metres wide and grounded on the seabed 12 metres below.
In the summer we would never normally approach an iceberg underwater, as they can collapse or roll with no notice. However, locked in the sea ice, this one was safe to approach. Diving an ice wall is like no other wall dive. Up close, the ice is pitted with rocks where it has previously made contact with the seabed, and there’s a surprising number of small fish living on the surface.
The seabed has also changed considerably since our last dives in the autumn. Previously it was covered with thousands of feeding sea cucumbers, all with their tentacles splayed out into the water column. Now, with almost no plankton to feed on, they have entered a kind of winter dormancy and have retreated under rocks and algae, waiting for the arrival of the summer phytoplankton bloom when they can begin feeding again.
We’ve been in the water for less than half an hour, and it is already time to return to the surface. The water is almost at minus 2°C, and if we stay any longer, our frozen hands will become completely useless. Back at the surface, we learn another lesson of Antarctic diving: it is minus 20°C and, unbeknown to us, the water on our drysuits immediately begins to freeze. I have never known discomfort quite like being frozen into my dive hood and having to pour a hot-water bottle over my head to break free. I look down at my first stage and am alarmed to see that it is also encased in solid ice!
The sea ice persists throughout the rest of the winter, and we become accustomed to the peculiarities of ice diving. It no longer feels odd to be taking a Ski-doo to dive sites where we once went by boat, and we grow to appreciate the extra space for kitting up that the ice affords us. As the only research station to consistently dive throughout the year in Antarctica, the science we can achieve during this time provides a unique insight into the seasonality of Antarctic marine life. Consequently, we have little time to really take in the majesty of diving under the ice and spend most of our dives head-down at work. However, as winter progresses, the sun starts to return in force to the sky, and it is hard not to marvel at the glowing blue ice above our heads.
In October, the ice finally blows out. We have had a very warm year, and to lose the ice this early is unusual. While it is a shame to be no longer diving through the ice, the open sea allows us to visit sites that we could never have travelled to on Ski-doos. I check on experiments that I haven’t visited in nearly six months and am relieved to find that they haven’t been destroyed by iceberg groundings. The sea is still cold and clear, but tiny nano-phytoplankton are beginning to grow in the water column, and the seabed in turn responds; soft corals which have been leathery-smooth for months are now fuzzy with extended feeding polyps, and the seafloor is slowly starting to return to being a mass of protruding sea cucumber tentacles.
It is also bizarrely enjoyable to hear the sea again. I had barely noticed it, but a frozen sea is an entirely silent one, and now we can hear the crashing of waves once more. The return of the sea also brings back many of the larger animals – the first penguin is spotted on the station, and a large elephant seal has hauled up onto a local beach. By summertime, these animals will be so numerous that they become part of the fabric of station life, but for now, they are an exciting novelty.
I have had the privilege of calling Antarctica home for almost a year now. Stuck on a small research station with an unchanging horizon, you might think that by this point I would be eager to leave. However, the reality is that the horizon does change; icebergs come and go, the sea freezes and unfreezes, wildlife booms and busts, and the sky is an ever-changing tapestry of sun, cloud, moon and stars. You might also think that living on a monotone continent dominated by snow, ice and rock, I would be desperate to see some greenery. To an extent this is true, I really miss trees! But I have only to dip beneath the waves (or ice) to encounter all the colours and vibrancy that I could ask for.
Antarctica may not be the easiest place to dive, but the underwater realm is so unique that the rewards are worth all the effort and limitations. To dive here at all has been a privilege, but to dive here in the winter, when very few others have ever done so, is something that will stay with me forever.