Finally, it's summer in Bremerhaven, on the coast of Northern Germany. It's one of those rare days when the sun is shining and the temperature is about 30°C. Everybody at the Alfred Wegener Institute for Polar and Marine Research ( AWI ) is wearing T-shirts and shorts. Except me. I am dressed in long trousers, a wool sweater, and a long jacket. I am on my way to the cold room, where I keep live copepods at 0°C.
Copepods are small crustaceans, often less than 2 mm long, that are distributed worldwide and dominate marine zooplankton communities in terms of abundance and biomass. Despite their small size, copepods play a vital role in marine ecosystems. Dominant groups are herbivorous and are an important link between primary production (algae) and consumers of higher tropical levels such as fishes and whales. The life cycle of copepods is genuinely fascinating in polar regions. Many species spend the long winter period without food at depths of more than 1000 m and return to the surface to reproduce and grow once phytoplankton becomes available in spring.
Zooplankton biology deals with ecological issues, individual and population-based models, and broader topics, such as climate change and fisheries management. My research focuses on various aspects of the life history traits of zooplankton organisms and their population dynamics in relation to physical and biotic environmental conditions. One research project, for example, studies the reproductive activity of Arctic and Antarctic species in response to changing food conditions. To obtain the large picture of the mechanisms of reproduction, I use a combination of field observations, ecophysiological experiments, and histology.
Field observation means going on cruises, where we take net samples from the water column to catch zooplankton organisms. Expeditions are one highlight of working as a polar biologist, and the polar regions are the most fascinating areas I have ever seen. The ecology of zooplankton organisms is closely related to hydrographic features and water-column processes, and thus my work requires close cooperation with researchers in other disciplines, such as physical oceanography, phytoplanktology, and chemistry. I have always enjoyed the interdisciplinary and international approach during cruises.
I am lucky, though, that I don't get seasick. When the weather is rough, working is difficult due to heavy ship movements. However, I have been to the Arctic three times, and to the Antarctic once, with the German Research Vessel Polarstern , which is managed by AWI, and this vessel provides excellent facilities for working under these conditions. Seagoing expeditions to polar environments take at least several weeks and can last up to 3 months. Living and working on a ship with about 100 people for such a long time requires good communication skills, tolerance, and cooperation. As time is limited, the ship operates 24 hours a day, meaning that sometimes you take samples at 3 a.m. in wind and snow. In return you get unique data, scientific inspiration, and friends from all over the world.
Some experiments are conducted on board; for others I take live copepods back to the laboratory at AWI. During reproduction experiments, I expose females to different algal concentrations and species and check their egg production at 24-hour intervals. Sometimes I have to work at 0°C for 4 to 6 hours every day for several weeks, taking care of algae cultures, changing water in incubation chambers, and counting copepod eggs.
My career path to the cold room required the usual blend of perseverance and luck. I studied zoology, limnology, and microbiology at the University of Göttingen, and I did my master's thesis at the Biological Institute on Helgoland  on flat worms (Platyhelminthes), which fix their egg capsules on shells of the bivalve Macoma balthica. Just by chance, I heard about an opening at AWI for a Ph.D. thesis on gonad development and egg production of three Calanus species (copepods). After my Ph.D., I got a postdoc position at AWI within the E.U. research project, "TransAtlantic Studies of Calanus finmarchicus," which studied the ecology of this dominant species in the North Atlantic. During these exciting 6 years, I participated in expeditions to the Arctic and the North Atlantic, and I spent several months in Norway at the universities of Tromsö  and Bergen . Simultaneously, collaborations developed with scientists from the United Kingdom, Denmark, Canada, and the United States.
As I had wanted to work abroad for some time, I applied at the Deutsche Forschungsgemeinschaft , which funded a 1-year research fellowship at the Woods Hole Oceanographic Institution  in Massachusetts. There I was involved in a U.S. GLOBEC project  that focuses on the factors controlling the population dynamics of key zooplankton species on Georges Bank, an underwater mountain off the East Coast of the United States. It was a wonderful and inspiring experience, and I came back to AWI with even more enthusiasm and fascination for the copepod world. Currently, I am working on my Habilitation, which includes scientific work and teaching at the University of Bremen . Working as a polar researcher affords me a great opportunity to develop and use my capabilities in science, teaching, teamwork, and creativity.