Cryospheric Sciences | Cryosphere Caps: PhD hats and the researchers that wear them

A group of people standing around a person holding a decorated hat in their hand.

Figure 1. Tina and her colleagues investigating the PhD Hat, on the day of her PhD defense [Credit: Tommi Odenthal]

This miniseries features the tradition of ‘PhD hat’ making in German research institutes and universities. For those of you unfamiliar with this idea (as I once was), this is one of the final milestones a graduate student has before they are officially a “Dr.”. Upon the successful defense of a thesis, the labmates of the PhD student craft a graduation hat from a mishmash of scrap cardboard and memorabilia. Hours of work go into these beloved pieces, and you can often find these hand-made creations fondly perched on a shelf in faculty’s offices. Here, we talk with several researchers who work within the cryosphere sciences about the stories that shaped their PhD hats. Last month, we ‘herd’ about Torben’s arctic herbivore hat. This month, we explore the Nitrogen cycle through the permafrost soils of Siberia with Tina and her PhD hat.

For the second post in this series, we hear from Dr. Tina Sanders (she / her). Tina received her PhD (and ‘PhD Hat’) in 2011 from the University of Hamburg’s Institute of Soil Sciences. Her thesis research focused on questions about microbial community functions within Siberia’s permafrost soils, and how these small organisms could have big impacts to the entire food-web in the Arctic.

Today, she investigates nutrient cycling in a variety of ecosystems, though she always ‘keeps one foot in the Arctic’. As the Deputy-Head of the Department of Aquatic Nutrient Cycles at the Helmholtz-Zentrum Hereon in Hamburg, she keeps her other foot in the Elbe River. There, Tina and the team study how the Elbe’s estuary filters nutrients and carbon from the river water as it flows into the North Sea. As a self-professed ‘Nitrogen nerd’, Tina’s current projects center around investigating the role of Nitrogen in increasing (or limiting) microbial productivity within arctic and temperate aquatic systems.

Hi Tina, can you tell us what your original thesis research question was? Did it change over time?

Originally, I wanted to find out what kind of ammonia-oxidizing bacteria existed, and were active in permafrost soils in Siberia. In permafrost soils, a huge amount of organic matter (including nitrogen) might become available to microbes as permafrost thaws. Ammonia-oxidizing bacteria are microbes that can carry out the first step of nitrification. This is an important part of the nitrogen cycle, and is crucial to transform nitrogen into a form that primary producers (such as vegetation) can use.
My thesis changed direction in two ways. (1) As it turns out, it’s not just bacteria but also archaea that are responsible for the ammonia oxidation, so for my thesis I was looking at both of these organisms in Siberia’s permafrost soils. This is significant because although both bacteria and archaea are single-celled organisms, they are in two different domains of life. (2) In the beginning, we thought that working in the polygonal tundra soils would be interesting. After I was actually in Siberia (Samoylov Island) for the first time in 2007, I realized that the floodplains and beaches could also be really interesting for nitrogen turnover. So, we decided to include the floodplain soils in our search for ammonia-oxidizing organisms.

Could you give us a tour of your PhD Hat?

Pipette Tips Sculpture

In remote field stations like Samoylov (a research station based on a remote island within the Lena River Delta), it can be difficult to maintain sterile conditions to carry out the microbial sampling, as you often don’t have the specialized equipment of a full laboratory. In the old field lab on Samoylov we had used a pressure cooker to sterilize the plastic pipette tips, and one day I had left the pressure cooker on too long…

[Tina’s supervisor kept the resulting half-melted mass of pipette tips as a souvenir, and returned it to her as the centerpiece for her PhD hat, in Figure 1]

Photos of Microbial Organisms

A person with a hat on top and a bottle in the hand sits on a trolley decorated with green twigs.

Figure 2. Riding in style. The ‘Nitrotoga arctica’ (the black plush animal that Tina is holding) rode back to the Institute of Soil Science with Tina after the successful defense of her PhD at Uni Hamburg defense. The photos Tina took of the microbes are the grey ovals that ‘grow’ around the pillar of the hat. [Credit: Tommi Odenthal]

With enrichment cultures of my ammonia oxidizers I have conducted some experiments to understand their behavior, e.g. how much ammonia they eat at low temperatures. However, I also used an electronic microscope to take photos of my microbial cultures, which allowed me to really visualize the bacteria that I had isolated.

Doing this, we found a new genus – Nitrotoga arctica. This microorganism had a thermal optimum of 15°C but it was still growing around freezing (0°C) temperatures, which tells us that it is well adapted to the colder temperatures of the Siberian arctic soils [Figure 2].

The “Bollerwagen” back to the Institute of Soil Science

At Uni Hamburg, usually the PhD defense takes place in the ‘Geomatikum’ building, but our Institute of Soil Science is about 2km away. So, the other PhDs students from the Institute of Soil Science had prepared the Bollerwagen [a type of trolly] and brought me back to the Institute for a celebration after the defense. This was a long-standing tradition of the Institute of Soil Science in Hamburg. [Figure 2]

Figure 3. Tina’s search for ammonia-oxidizing bacteria took her to the permafrost soils of Siberia (Russia) in 2007 and 2008. [Credit: Claudia Fiencke]

For those who just joined a lab group in Germany, or maybe want to bring this to their own lab group: What is essential to include in a labmate’s PhD hat?

I would suggest not to just put ‘scientific things’ on the hat, because next to the scientific work, life as a PhD student is also really interesting. Maybe you don’t see it at the time, but I think the PhD thesis is the most enjoyable work you do as a scientist. The ‘PhD hat’ also should represent the memories made with your labmates and the other PhD students. These interactions are really important for your own development in both the scientific and personal sense. So, something on the hat should represent these relationships, and of course something from the memories of expeditions too [Figure 3].

Thank you for your time Tina, and for taking us on a tour of your PhD hat.

To the reader, stay tuned next month for another installment of this miniseries as we tour the cryosphere through the PhD hats of those who study our icy planet.