Membrane-Inlet Mass Spectrometer (MIMS) for the monitoring of gas exchange processes of phytoplankton on the cellular level and in real-time. Our MIMS system consists of a custom-made, temperature-stabilized cuvette and inlet system combined with a sectorfield multicollector mass spectrometer (IsoPrime). Dissolved gas molecules like CO2 or O2 permeate through the membrane, are ionised and detected only seconds later in the mass spectrometer. The advantage of this approach is that several processes, e.g. cellular fluxes of carbon, oxygen and electrons, can be observed and quantified simultaneously.
A second,ship-going Membrane-inlet mass spectrometer (MIMS) was built for field and ship-based applications on expeditions. Being designed for standalone operation, the system has its own energy-backup, gas compressor and low-temperature (-100°C) generator, requiring only common 220V electricity input. This system is based on a quadrupole mass spectrometer (Pfeiffer) and was optimized for continuous measurements of CO2, O2 and Argon. With this approach, also community production can be assessed with high temporal and spatial resolution.
Chlorophyll a-fluorescence based approaches such as Fast repetition rate fluorometry (FRRF)provide a unique analytical insight into photosynthesis. Our FastOcean-FRRF (Chelsea Industries) is used to characterize changes in electron transport efficiencies as well as for the estimation of energy transfer efficiencies from photochemistry to (14C-based) biomass buildup. Furthermore, the FRRF technique derives the functional absorption cross section, the extent of excitation transfer between PSII reactions centres (connectivity factor), the yield of charge separation (efficiency of energy capture), and kinetics of photosynthetic electron transport. In addition to these, we operate aFluorescence-Induction Relaxation system (FIRe; Satlantic) that is directly connected to the MIMS. This allow real-time assessment of both ‘ends of photosynthesis’ , so that electron transport can be directly compared with oxygen and carbon fluxes.
For our research we need to culture microalgae in appropriate vessel, that suffice high demands regarding optimal volume, irrandiance, mixing, aeration etc.. Therefore we operate several different designs of incubators serving different needs, e.g.open- and closed-system dilute batch approaches orchemostats. To supply our laboratories with aeration, we constructed agas-mixing system that creates air with CO2 partial pressures adjusted to our needs.
For measuring particulate C and N including their isotopic signatures in samples, we use anANCA-SL 20–20 (Sercon) mass spectrometer. Next to determining the elemental quotas, stoichiometry and fractionation, MS measurements are also used for tracer studies with stable isotopes (e.g. 13C, 15N).
For the detection of amino acids and small metabolites, we applyHigh-performance liquid chromatography (HPLC). Our HPLC method is based on the derivatization of target molecules with fluorescent dyes (OPA, FMOC), followed by gradient reversed-phase-separation of analytes, a method that yields high specificity and low detection thresholds.
With the help offlow cytometry (Accuri C6, BD Biosciences), we can investigate the composition of the smaller fractions of natural or experimental phytoplankton assemblages, which are otherwise difficult to resolve. Furthermore, the flow cytometer is a powerful tool for the enumeration and physiological characterization of single-celled phytoplankton species, e.g. after staining with specific dyes.
Our section runs a fully equipped wet-chemistry laboratory. Here we are able to determine properties of seawater like Total Alkalinity, Dissolved inorganic carbon (DIC) and pH with high precision and accuracy using automated burette systems, colorimetric DIC analyzer and a spectrophotometer for most exact pH measurements. Nutrient analyzers and procedures to determine biogenic silica are also available for our research.
In support of AWI´s FRAM Ocean observatory, we increasingly operate submersed in-situ sensors to measure year-long profiles and time series. These sensors are less precise compared to lab-based chemical analyses and thus require comparisons with conventionally analyzed water samples. Besides new innovations likeADCPsthat monitor currents based on the movement of particles in the water column, we also apply sensors like CTDs to obtain conductivity and temperature data. To get information about biological and chemical parameters, we deploy pH, pCO2 and nitrate sensors. A water sampler deployed close to these sensors provides up to 48 reference water samples for sensor calibration and further chemical analyses back in the institute.