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Diving for life in the darkness: a survey of the deep

By Camila Negrão Signori

Just being involved in a scientific expedition aboard the R/V Atlantis (managed by the prestigious Woods Hole Oceanographic Institution, WHOI) was itself an enriching experience. I was no stranger to ship research, having crossed the South Atlantic from Africa to Brazil, been to the continental shelf of the southern and southeastern coasts of Brazil, and sailed three times in the waters of the Southern Ocean surrounding the Antarctic Peninsula, but my experience on the Atlantis with the submersible Alvin was quite a different experience. 

Photo 1: Alvin being prepared for its decent, with two divers on top and a boat in the water to offer support. (Photo by Camila)

This experience was only possible by an invitation by my collaborator Dr. Stefan Sievert who had helped develop part of my PhD research with polar samples in Woods Hole (funded by CAPES-Training Coordination of Higher Education Personnel). Stefan was the scientific coordinator of this cruise with a project funded by the US National Science Foundation (NSF) entitled “Integrated Study: metabolic energy, carbon sequestration, and colonization mechanisms in chemosynthetic microbial communities in deep hydrothermal vents.” My job was to help Stefan and Jesse McNichol (my friend and doctoral student in the MIT-WHOI joint program) in all on-board tasks. 

There are many reasons this was such a different experience from my other times at sea. This was my first time in the Pacific Ocean. It was my first time aboard a ship run by a research institute, and it had a greatly reduced crew of about 25 (the other ships I have been on have been run by the Navy of Brazil, manned by 50-60). This was an international ship, with 23 researchers from countries including the United States, Canada, Germany, Italy, Spain, Japan, China, and myself from Brazil. 

Instead of navigating to different oceanographic stations (to spatially explore physical, chemical, biological, and geographical oceanographic features), we remained in the same sample area of 9 degrees N for almost an entire month. Our landscape was an expansive ocean without an end in sight, and we were a 4-5 days steam from the nearest land. The objectives of the project were all related to the deep ocean, at hydrothermal vent sites. 

Photo 2: Camila Negrão Signori observing life in the deep ocean through one of Alvin’s five portholes (Photo by Stefan Sievert).

Typically, water is collected from different depths, selected according to differences in water mass through the layers of the ocean, using a Niskin bottle, usually coupled to a CTD-rosette system. However, for this journey, we used the famous submersible Alvin, diving daily to more than 2500 m deep to collect our samples. With the help of two robotic arms and a “biological basket” able to carry more than 180 kg of bottom material, we collected samples such as fluid from the vents, microorganisms associated with the sources, invertebrate worms, and near-vent settlers. 

Instead of using water collected by Niskin bottles on board the ship, we collected fluids for chemical and microbiological analysis with a special piece of equipment known as an Isobaric Gas Tight sampler (IGTs). These IGTs were developed by WHOI to maintain pressure and environmental conditions of the deep when brought to the surface. 

Photo 3: A “IGT” sampler collecting fluid with the help of a robotic arm. The fluid here was 25C at 2500 m depth, collected at the “Crab Spa” location. Crabs, bivalves, annelids, and microbial mats can be seen here. (Photo by Camila, C WHOI).

Despite calm seas, work in the ship’s lab with the samples was not a trivial task. When removing fluids from the IGTs, we needed to be extremely careful with the high-pressure samples when opening and closing the system. Work was done with tools I had not seen before, and this was often morning and night work (after the Alvin returned to the ship). It was very difficult to draw out 150 mL of hydrothermal fluid and then continue with traditional laboratory protocols such as DNA extraction of microorganisms, gas measurement (such as Hydrogen sulfide), measurements of chemosynthesis processes, counts and cultivation of microorganisms, and incubation experiments using different temperatures and nutrient additions. 

Having the chance to dive so deep was one of my dreams (I thought impossible), but it became a reality on November 14th, 2014. 

Once the Alvin was released into the water from the giant cable it had been suspended from off of the Atlantis, we felt a slight swing in the surface waters of the Pacific. After a last check by two divers on top of the submersible and a brief goodbye and good luck wave through the portholes, we started our descent to the deep sea. 

The first 100 m of the water column were a beautiful turquoise color, but shortly after crossing the 300 m depth, everything became completely dark and quiet. As we passed the Oxygen Minimum Zone (300-800 m), bioluminescent organisms appeared floating in contrast to the black water. After a very gentle hour and a half descent (it felt like I was sitting on a sofa!), the pilot, Phil Forte, turned on the Alvin LED spotlight and a new world appeared under my eyes. 

Photo 4: Hydrothermal source with black smokers in full swing, under the sea. 2514 m deep, observed through the Alvin porthole. (Photo by Camila, C WHOI)

We landed on the seafloor, which was made up of ocean bottom ~200 million years old and some basaltic rock that shone brighter, indicating a more recent formation of a typically more active area. And so, with the help of our GPS, we began to explore the study area for six hours. After another hour, we had returned to the surface.

From all of the scientific papers, pictures, videos on the internet, and stories from those who have plunged to these hydrothermal vents in the Pacific, I expected I would find a bounty of life. But deep down, we always have that nagging in our heads…is this real, did these people actually see these things? 

And yes! We did see an abundance of life in the deep ocean: many small white crabs that justify the name “Crab Spa”; invertebrates including the annelid Tube worm, a species of giant tube worm that can reach nearly 2 meters in height with reddish color at the tips from the hemoglobin complex adapted to the sulfides present, toxic for us humans; 30 cm long, blind, albino fish swimming about resembling eels with their lack of scales (called Eel pout). We also saw yellow bivalves, small shrimp, and lobsters in the area in addition to the famous microbial mats. 

Photo 5: Dr Stefan Sievert (left), pilot Phil Forte (center), and Camila Negrao Signori (right) in Alvin’s sphere 2514 m deep. (Photo by Camila).

I must confess however, that, although a researcher of microbial oceanography, what impressed me the most was the geological structure that seemed artistically carved, surrounded by black smokers rich in metal sulfides. It was simply stunning to see this “step” in the ocean crust, where the Earth was being newly formed, and life abounded.


How did I feel after the dive? Well, aside from my amazement at the excess of life and beauty, appreciation for the technology we have developed to explore these new frontiers, and how blessed I felt to have experienced this opportunity with such a great international group of competent people, I felt very little. As small as a drop of water in the vast ocean or a tiny bacterium shining under the microscope! We still have much to learn about the mysteries of the sea. 

Photo 6: A group of scientists embarking on the R/V Atlantis, opposite the Alvin garage. (Photo by Camila).

Dive 4769: an experience I will never forget! Sometimes when I find myself thinking about this dive, it pains me to believe that I was there at one time. I am extremely grateful to Dr. Stefan Sievert, who trusted in my work and gave me this chance to ride and learn on board the Atlantis and Alvin. I also thank all of my fellow scientists and competent crew, for sharing this experience with me and for all of the efforts and hard work put in to break into life in the dark. 

For more information, check out the links below:

Expedition blog “Dark Life” to the hydrothemal vents of the East Pacific Rise:

About Woods Hole Oceanographic Institution:

An overview of my research career:


About Camila Negrão Signori:

Oceanographer, Master in Biological Sciences/Zoology, and PhD in Sciences/Microbiology, with periods of comings and goings to WHOI (USA). Born in Campinas (Sao Paulo), but has been enchanted by the sea since a childhood spent in Ubatuba Bay. In her spare time, she loves sports and dance, is always surrounded by family, her boyfriend, and wonderful friends. Today she is a Post Doctoral researcher at the Oceanographic Institute at Sao Paulo (USP) and a member of the microbial ecology laboratory where she researches the effects of climate change on microbial communities of the Southern Ocean. 


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