Culturing facilities
For our research, we cultivate microalgae in climate-controlled culture rooms whose temperature can be individually adjusted. The organisms are kept in special incubation setups that have to meet the highest requirements in terms of contained volumes, illumination, aeration, etc.. We therefore operate several different incubator designs in parallel for a wide range of requirements, e.g. for 'open' and 'closed' dilute-batch approaches, or for experiments in chemostats. To supply our algae cultures and media with air, we use a specially developed gas mixing system that delivers air mixtures with precisely adjusted CO2 concentrations to our laboratories.
High-pressure aquaria for the cultivation of deep-sea foraminifers
We work with high-pressure aquaria of 3L, 10mL and 0.3mL to simulate deep sea conditions for the cultivation of deep-dwelling foraminifers. The smaller volume aquaria allow a visual connection with the confocal and as well as our Axiozoom microscope. For the microscope observations, special cooling-tables, ventilations and illumination equipment was customized.
Coulter Counter
The Coulter Counter is an instrument for counting particles in an electrically conducting fluid. Originally developed for analyzing blood cells this method also allows the determination of unicellular algae in a culturing medium with respect to number and size.
With the help of flow cytometry (Accuri C6, BD Biosciences), we can investigate the composition of 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.
Alkalinity
Alkalinity is an important parameter in the marine carbonate system. It is determined via titration. For this we run a TW Alpha Plus device from SI Analytics. The instrument has 21 sample holders. A minimum volume of 60 ml is needed for a duplicate determination.
Dissolved Inorganic Carbon (DIC)
Using "Continuous Flow Analyzers" (CFAs) manufactured by Seal, we are able to assess the concentrations of dissolved inorganic carbon (DIC) in sewater in a high throughput fashion. We also provide these analytics to our colleagues from other AWI sections.
VINDTA
The VINDTA (Versatile INstrument for the Determination of Total inorganic carbon and titration Alkalinity) combines the concept of an alkalinity titrator with an additional extraction stage that removes CO2 from seawater and enables a simultaneous coulometric titration to assess dissolved inorganic carbon in the sample (DIC).
Nutrient analysis
For analyzing nutrients we use a Quaatro 39 Autoanalyzer from Seal Analytics. The device has 39 pump tube positions. A sample volume of approx. 6 ml is needed for one measurement determining ammonium, nitrite, nitrate, phosphate, and silicate, simultaneously.
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 sector field 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 a pulse-amplitude-modulating fluorometer (Mini PAM II, Walz) that can be directly connected to the MIMS cuvette. This allows real-time assessment of both ‘ends of photosynthesis’, so that electron transport can be directly compared with oxygen and carbon fluxes.
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 like ADCPs that 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.