Getting to the bottom of the deep sea

Getting to the bottom of the deep sea

The ocean is her passion, the seabed her lab bench. Antje Boetius from the Max Planck Institute for Marine Microbiology in Bremen always has multiple objectives in her sights: from discovery and precautionary research to technological development and scientific communication. 

Lectures abroad, preparatory paperwork for expeditions, team meetings, committees: “If you want to meet up soon, it would be best if you come by immediately – otherwise, it won’t be possible for another two weeks,” says Antje Boetius on the phone. “How about five o’clock?” Friday, 5 p.m. – the weekend has already started for a lot of people, but she squeezes in the interview before calling it a day because she believes in the importance of scientific communication, and she has resolved to deal with inquiries about her work immediately.


Boetius studied deep-sea mud volcanoes on an expedition to the Mediterranean with the L’Atalante research vessel in 2003.

“Yes, I work quite a lot,” she says later, “around 14 hours a day. And on the weekend I like to work on my manuscripts – really.” Boetius stresses the “really” as though she wants to leave no doubt about the fact that she enjoys her work. But that’s obvious anyway. It’s approaching evening and she comes across as energetic and fresh, as if the week had just begun. There’s no doubt about it, Antje Boetius is passionate about her research.

The marine biologist’s to-do list is endless. She is head of the Joint Research Group for Deep-Sea Ecology and Technology at the Max Planck Institute for Marine Microbiology in Bremen and the Alfred Wegener Institute (Helmholtz Centre for Polar and Marine Research) in Bremerhaven. She is also Professor of Geomicrobiology at the University of Bremen and Vice Director of The Oceans in the Earth System excellence cluster at the MARUM Center for Marine Environmental Sciences in Bremen. She has at least three balls in the air at all times – and juggles them all successfully.

Species diversity on the seabed

The main topic of her research is the role of the seabed and its inhabitants within the Earth system – a very broad topic, as the seabed accounts for two-thirds of the Earth’s surface, and its biodiversity exceeds that of the terrestrial habitats. The issues Boetius tackles are equally diverse. “Around every five years, I change the focus of my work – sometimes I work on a particular biogeochemical process, such as the consumption of the climate gas methane; sometimes on the biodiversity on the seabed; and sometimes on the reaction of marine ecosystems to the melting of the sea ice and human interventions.”

Irrespective of what she is working on, Boetius aims to spend as much time as possible at sea, observing nature directly. In total, she has spent several years of her life on research ships. When she talks about this, she sounds like an old sea dog who longs to be back on the high seas again. “I make sure that I go on an expedition at least once a year,” she says.

Boetius is a deep-sea researcher and has plunged to the remote ocean depths with diving boats many times – in the Atlantic, Indian, and Pacific Oceans and in the Mediterranean and Polar Seas. Aided by spotlights, she has observed pale deep-sea fish, vividly colored sea cucumbers, bizarre giant worms and delicate brittle stars. What she is most interested in, however, are the smallest of life forms: bacteria. They may be microscopic, but they are extremely important, as they metabolize an enormous volume of substances and even influence the Earth’s climate in the process.

Boetius was born in Frankfurt am Main and grew up in Darmstadt, far from the sea, but she made up for this distance from the water with her imagination. She is the first-born child in her family. Her mother is a teacher who taught her to read at an early age – she started reading when she was three and her favorite activity as a child was to bury herself in a book. Pirate novels, Treasure Island, Moby Dick, and everything by Jules Verne. She loved them all.

She watched little or no television, and when she did, it was the diving films of Hans Hass and his wife Lotte and the adventures of Jacques-Yves Cousteau that attracted her attention. “It was amazing. To go on expeditions as a career, live on yachts, do research in a bikini, have all kinds of underwater adventures – all of that inspired me.” During this period of her life, her parents separated, but the family reunited for holidays. Antje, her siblings, her mother, her father and his new partner travelled to the sea together, usually to the Atlantic coast in Ireland, France or Norway. They camped in the open country, paddled along the shore in rubber dinghies and trawled the crystal-clear water for animals.

When she was 12, her father gave her a small set of equipment for nature exploration: a weather station, binoculars, stereo magnifying glasses and a small centrifuge. She knew what she wanted to do from an early age: to study in Hamburg, where there are a lot of ships and the sea on the doorstep. She wanted to experience the sea as a researcher.

Boetius has certainly fulfilled that early career wish. Today, she is often out and about on the high seas, particularly in the Arctic, with the German research icebreaker Polarstern, which enables her to explore the ice-covered waters of the North Atlantic. She wants to understand how climate change is altering life: the composition of the microorganisms in the ice, the production of algae in the water and thus also the food for deep-sea communities, and the deposits in the seafloor sediments.

Ice melt in the Arctic

The marine alga Melosira arctica grows on the underside of the sea ice.

During the time she was travelling in the Arctic in 2012, the sea ice was melting at a faster rate than ever before. It was thin and littered with melt ponds, making it particularly bright below the ice. The marine alga Melosira arctica was able to grow particularly well under these conditions and form dense, seaweed-like forests under the ice. Due to the intense warming, however, the ice melted and the algae sank into the depths of the ocean in fist-sized clumps.

Boetius and her colleagues sent cameras down to the seabed, which provided them with astonishing images: the otherwise desert-like floor of the central Arctic was covered with a green algal carpet. Only a few sea cucumbers and brittle stars could make anything of the Melosira clumps. The deep-sea measurements carried out by the Max Planck researchers showed that the new food supply is being exploited mainly by bacteria that consume the oxygen in the seafloor on site. The researchers were able to report and describe this unexpected reaction of the Arctic ecosystem to the ice melt in a report they produced on board the research vessel.

The next Arctic expedition took place in 2014 and tackled a completely different topic. This time, Boetius and her team were at sea to explore the Gakkel Ridge north of Greenland. It was suspected that there were hot springs and special biocoenoses at a sea mount on the seafloor here, four kilometers below the ice. Such springs are known to exist at mid-ocean ridges, where new Earth crust is formed and the ocean plates drift apart. The seawater penetrates deep into the mantle there, is heated by magma chambers, reacts with the rock and spews back up into the ocean full of energy and minerals. This is how hot springs provide a nutritional basis for bacteria, which, in turn, provide sustenance for higher life forms. Life flourishes there in a way that is found almost nowhere else in the deep sea.

No one had previously observed life at the hot springs in the Arctic, though, because the sea ice was blocking the way. Since 2001, there had been indications of surprisingly strong heat emissions and smoke plumes in the sea, but no images had yet been obtained of these extreme habitats in the ice-cold Polar Sea. Boetius and her team had a plan – and a great deal of luck: even with full ice cover, they were able to deploy underwater vehicles from the Polarstern and search the sea floor. On the last day of the expedition, they struck gold: small vents, known as black smokers, surrounded by unfamiliar gardens of white glass sponges appeared on the images they recorded. The international team is currently working through these findings. They want to prove that the spreading of the Arctic Ocean functions differently than predicted. This is the kind of discovery that fills Antje Boetius with enthusiasm.

In the Black Sea, bacteria populate gas sources at a depth of 260 meters and form towers standing several meters tall. These are supported internally by lime.

Antje Boetius took her first steps into the world of science at an early age. Despite being bored by biology lessons at school, with their focus on the description of plants and animals, upon completing her German school-leaving examination in 1986, she moved to Hamburg to study marine biology. A relative suggested that she enroll to study with deep-sea researcher Hjalmar Thiel at the Institute for Hydrobiology and Fisheries Science there.

At that time, Thiel was among the scientists who were studying life on the manganese nodule fields at the bottom of the Pacific Ocean. Back then, the large-scale mining of the nodules was being considered for the first time. As part of the international DISCOL project, the team of scientists headed by Hjalmar Thiel and Gerd Schriever ploughed a few square kilometers of the seabed in order to investigate how life in the deep sea would react to such an intervention. It appeared that the mining of the manganese nodules was about to become a reality, but no ecological studies had been carried out on the consequences.

Thiel invited the young student to meet with him. He began by advising her to study all aspects of biology and not to specialize too early. But Antje Boetius already knew that she only wanted to focus on the sea. “He told me to get back to him when I had completed my intermediate undergraduate diploma.” Antje Boetius was born in 1967, so she’s a baby boomer. The university lecture halls and labs were overflowing with students, and the waiting lists for the most interesting courses were long. She had to earn money to finance her studies, so she worked part-time as a waitress in a pizzeria and as a secretary in an insurance company – “a very strange world,” she says, “where everything is about money.” The highlight of her undergraduate studies was her first short ship expedition, which finally convinced her that she belonged on a research vessel.

When she started her main undergraduate studies in 1989, she was finally able to concentrate on marine research. She attended every lecture that had anything to do with water, including Thiel’s deep-sea lectures. At one point, he was looking for assistants for a large-scale expedition on the Meteor research vessel in the northeast Atlantic, and to her delight, she was selected to participate. Before the trip started, however, Thiel put forward a surprise offer. He asked whether she would like to participate in an exchange program – there was a spot available at the Scripps Institution of Oceanography in the US. Scripps in La Jolla, one of the best-known marine research institutes in the world, directly on the surf beach! Give up her part-time jobs and interrupt her studies immediately after her first big expedition with the Meteor? What to do. But she didn’t spend a lot of time deliberating, and started packing her bags for the trip to the US.

Antje Boetius has never regretted the decision. She is very enthusiastic about the direct contact between the researchers and students there, and the considerable attention paid to the students. She completed so many internships and courses at Scripps that the time she spent there was fully counted toward her degree coursework; all that remained for her to do on her return was to write her degree thesis. To that end, she immediately participated in several research expeditions. And it was on one of these that she met her future partner, a crew member from Bremerhaven. Boetius packed the insights she gained from over four months of expedition into her thesis. “It was all very tightly calculated, but I learned so much in the process.”

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