Members

Björn Rost - Being small and yet so mighty, phytoplankton are the true rulers over ecosystems, elemental cycles and climate. I therefore felt very privileged to start my career studying the remarkable group of coccolithophores and their responses to changes in carbonate chemistry (end of the 90’s, the term ocean acidification did not yet exist). Even though my work has often been motivated by biogeochemical questions, I dug myself into algal physiology, focusing on those mechanisms phytoplankton use to overcome limitations in central pathways like carbon assimilation. Setting up several techniques, e.g. Membrane-Inlet Mass Spectrometry (MIMS), we were then able to assess cellular carbon and energy fluxes in real-time. This way we could not only identify certain processes, we could also put numbers to them, which allowed us to directly compare species and their responses to environmental drivers. If this process-understanding is combined with ecology, I believe we will be able to explain the species- or group-specific sensitivities towards multiple stressors and make thorough predictions for the future.

Sebastian Rokitta - Global Change will have many consequences on planetary scales; however, the origins of these consequences are to be sought on the molecular scale, i.e., within the cells of the organisms. Being a molecular biologist, photosynthesis physiologist and biochemist, I explore how phytoplankton responds to various environmental drivers on the sub-cellular basis, and how these drivers modulate each other. Besides standard elemental analyses, I use in-vivo measurements, transcriptomics and HPLC-based metabolite detection techniques to explain what happens inside cells when they respond to environmental change. The alterations of gas-fluxes, biochemical pathways and molecular machinery help me to draw conclusions about the underlying mechanisms that cells apply to maintain homeostasis in changing environments.

Clara Hoppe - In the past two decades, a lot of research on phytoplankton responses to global change has been conducted. Most of it has been based on single strain experiments in highly controlled stable lab conditions. My goal is to integrate approaches from classical ecology and biological oceanography into this field of research. We will only gain a holistic picture if we investigate both the complex interactions occurring in the natural environment as well as the underlying cellular physiological mechanisms, which together determine phytoplankton responses to global change. My current main interests are how ecosystem structure (i.e. composition) and functioning (e.g. primary productivity, strength of the biological carbon pump) are linked in the present-day and future Arctic ocean, as well as to which extent this relationship is driven by differences between functional groups (i.e. species shifts) and intraspecific plasticity (i.e. sorting between strains of one species). To investigate this relationship, I conduct experiments with natural phytoplankton assemblages as well as isolated strains under different multiple driver matrices.

Sinhue Torres-Valdes - Nitrogen, phosphorus, silicon and carbon are elements essential for life that exist dissolved in seawater. Phytoplankton use them to produce organic matter and oxygen (that we eventually breathe, by the way) through photosynthesis (i.e., primary production). A proportion of organic matter (and the energy it contains) is transferred up the food webs. Another proportion is lost as biogenic particles that sink to depth, and yet, another proportion is converted to dissolved organic matter (DOM). Some of the DOM and sinking organic matter are then used by bacteria, which in turn transform it back into nutrients and dissolved CO2. Particles and DOM escaping bacterial degradation end up locking carbon for hundreds or thousands of years. This way, life is sustained in the ocean and in the process, Earth’s Climate is regulated. Amazing!

The transformations described above are known as “Biogeochemical Cycles” and occur within large masses of water circulating around the world´s oceans. “Physical processes”, for example, changes in temperature, fresh water content, formation and melting of ice, evaporation/precipitation and interaction with other water masses also exert control on how and where nutrients and CO2 are distributed in the ocean, which has implications for primary and bacterial production, and CO2 uptake by the ocean.

In order to understand how such biogeochemical cycles function, I make observations, ranging from shipboard and on-ice observations (via the collection of seawater samples and subsequent chemical analyses), to observations generated via the deployment of state-of-the-art and emerging techno- logies (sensors, remote access samplers). I then use the information to diagnose the imprint of biogeochemical processes in the ocean and how these might be affected by climate change.

Klara Wolf – How life always finds a way never ceases to amaze me. Take arctic phytoplankton for an example: At temperatures close to the freezing point of water they manage to use the few sunlit weeks there are to lay the basis for a complex ecosystem. But how are these specialists going to cope with a rapidly changing environment? In my Master’s thesis I already started to investigate this question in arctic diatoms, which had been floating along in an icy fjord of Spitzbergen not long before coming to the lab. I found that we have to be careful with generalized assumptions about a whole taxon but may have to give more credit to the diverse traits of individuals if we want to understand and predict future developments. In PhD project, I hope to further elucidate how physiological, ecological and evolutionary processes help certain microalgae to stay in the game and thus shape the ecosystem they thrive in.

Laura Wischnewski - During my apprenticeship and work as a chemical laboratory assistant at the AWI, I learned many analytical techniques. Through my studies in forensic science at the Bonn-Rhein-Sieg University of Applied Sciences, I have gained a lot of additional experience in analytical techniques and also developed skills in various chemical and biological methods. Now I work as technician in the Section Marine Biogeoscience in the context of the FRAM project. At the AWI, I take care of the analytical equipment, carry out measurements (nutrient AutoAnalyzer, Sensors, pH, TA, DIC) and optimize methods. On Expeditions in the Fram Strait and in the central Arctic, I help implementing facilities for in-situ monitoring of nutrients and carbonate parameters and measure different parameters of the water column biogeochemistry.

Daniel Scholz - Within the FRAM project (Frontiers in Arctic Monitoring), my responsibilities are the development, deployment, calibration and data validation of in-situ sensor platforms that are used to monitor nutrients and carbonate chemistry parameters in the Fram Strait and the Central Arctic Ocean. To monitor such parameters in the ocean, it is common practice to analyze discrete water samples obtained e.g. by rosette water samplers, usually deployed from research vessels. In the Arctic, this procedure is only feasible in summer. During winter, accessibility is limited due to ice cover. An established alternative to obtain data during this period is the deployment of in-situ measuring sensor platforms, such as moorings and "ice tethered profilers". However, most in-situ sensors are designed and calibrated to perform in temperate oceans and thus, the Arctic represents a challenging  environment that lies outside the configuaration of most sensors. Hence, in order to determine sensor stability and performance, e.g. temperature influences or drift during long-term deployments, we use conventionally analyzed water samples for comparison. During my Bachelor studies in "Maritime Technologies" at the University of Applied Sciences Bremerhaven, I focused on maritime measurement devices, their application and data processing. A long-term position as student assistant in the "Marine Geochemistry" section at the AWI provided the opportunity to participate in developments and field tests of marine measurement platforms. With these interesting insights, I decided to gain more detailed knowledge about the inner life of sensor devices during my Master studies in "Embedded Systems Design". During these studies, I focused on "System on Chip" (SoC) design, which incorporates the programming and combination of FPGAs and micro-processors, digital signal processing, discrete controls as well as the design of analog sensor interfaces.