Optical detection & microsensor development

The Eddy correlation technique will be exploited to measure interfacial fluxes of the plates during tidal cycles, to confirm the phenomenon of 'breathing plates'. Focus of the extension of the WATT project will be the microbiology and transport phenomena of the seeps found in the first period of the WATT project. We will investigate why these sites are inhabited by flagellates (and not diatoms), what are the main sulfide and methane oxidizers. Also what are the main e-acceptors for oxidation processes in these seeps.
Two projects are submitted to funding agencies, awaiting the decision of reviewers. We plan to investigate the difference in microbial processes and community structure in carbonate and silicate sediments, and to study microbial processes in a large shallow carbonate plateau South of Cuba, in which freshwater seeps are found. Interestingly, these seeps follow cracks made by the impact of the large meteoroid 65 million years ago.
Peter Stief will finish with the kairomone project to study the indirect effects of fish on microbial processes in C. riparius-inhabited sediments. Furthermore, he is interested in the microbial processes of the N-cycle in the chimneys constructed during hypoxia. The Tinodes project will be completed by microbial community research along the age gradient of the burrows and nutrient measurements within the burrows of T. rostocki.

Björn Grunwald, Lubos Polerecky, Nikolaus Vlachopoulos

In the project Raeid Abed will characterize the aerobic heterotrophic populations of hypersaline microbial mats. He will use a combination of molecular and microbiological techniques to study diversity and species physiology, with emphasis on the resistance to extreme salinity and temperature fluctuations. The substrate spectrum will be determined, including the capacity to degrade oil-components. The community activities will be studied by microsensors. The project is a DFG funded, back-to-back with a Saoudi project. The sampling site is on the Persian Gulf.
Furthermore, two new PhD projects started on filamentous bacteria in hypersaline mats. One will study the physiology and ecology of Chloroflexus in Lake Chiprana mats. Another will study the ecophysiology of Beggiatoa in hypersaline and freshwater environments, in a collaboration with Lars-Peter Nielsen (Aarhus).

Björn Grunwald, Lubos Polerecky, Nikolaus Vlachopoulos, Raeid Abed

The adaptation of common nitrifiers to low pH is proven. However, the adaptation mechanisms are unknown. An approach combining proteomics and molecular analysis of functional genes and their expression in situ is currently planned (Technion, Haifa; Ralf Rabus, Dept. Microbiology; Rudolf Amann, Dept. Molecular Ecology).
In the mariculture project the focus will be on revealing key players in the anaerobic digester. This core subsystem can be considered as a model system for eutrophic marine sites (estuaries, upwelling areas). Future research will especially focus on dynamics and stability, and will include experimental manipulation of the system (e.g., inoculation with nitrate-storing sulfide oxidizing bacteria).
A large IP is submitted (BIOPOL) where we propose to study transport of pollutants in biofilms corvering sediments, and the effect of pollutants on microbial processes. Also we plan to develop PAM imaging of several photosynthetic communties as early warning system for pollution.
In a participation with a ForscherGruppe ‚Biomineralization' we plan to study mineralization of forminifera with microsensors. Most contributions towards the ForscherGruppe were approved, including ours. But due to inconsistancies of the integration, a final decision of the DFG on the ForscherGruppe as a whole is postponed.

Björn Grunwald, Lubos Polerecky, Nikolaus Vlachopoulos

The effect of environmental stresses on corals will be investigated with microsensors. Miriam Weber will study the effect of silt. We plan a project on the effect of pH/CO2 stress on the calcification and photosynthesis in corals, to be investigated with pH, calcium and oxygen microsensors, as well as classical alkalinity studies.
A project was submitted to the EU (CRAFT) by Dr. Friederieke Hoffmann that aims to study microbiology, microenvironments and transport inside sponges.

Björn Grunwald, Lubos Polerecky, Nikolaus Vlachopoulos

The development of a low-temperaure methane sensor is of considerable interest to deep-sea oceanographic investigations. Attempts to implement an existing biosensor have failed. The principle works but the sensor is too unstable and cannot be made pressure resistant. An amperometic sensor based on the electrosorption of methane on platinum is under development. The operation is based on methane adsorption on a Pt microelectrode prepolarized at a potential value within the double layer domain, where partial oxidation of CH4 occurs. Subsequently a linear potential scan towards more positive values is applied and methane is futher oxidized thereby giving rise in the current vs potential diagram to a peak. The signal can be further amplified by platinizing the platinum surface to enhance the surface area. Preliminary results indicate a response time in the order of minutes with a good signal-to-background ratio. The work up to now was done with large electrodes, with concomittant large Faraday currents. Miniaturization is expected to improve the signal to noise and response time. The working electrode compartment will be separated from the analyte solution by a hydrophobic gas-permeable membrane preventing organic water-soluble compounds to come into contact with the reactive electrode surface.
Within the MUMM project the microsensor group had the task to develop a methane microsensor for deep sea use and to characterize methane rich sediments with microsensors. The implementation of the methane biosensor was given up, as the microbiological component appeared too unstable. In two cruises we could collect data using sulfide, oxygen, T and pH microsensors. In the shallow Kielerbucht and in the 1200 m deep Haakon-Mosby Mud Volcano sulfide peaks coincided with the anaerobic methane oxidation zones. The produced sulfide was anaerobically oxidized by dense Beggiatoa communities. The data correspond very well with istope data from Helge Niemann and flux data obtained by chambers from Ursula Witte. In the outer areas the profiles reflect pumping activity of Pogonofora worms with sulfidogenic or methanogenic symbionts. Oxygen penetrates deep, sulfide and pH are irregular and the T-profile shows deep penetration of cooling surface water. In hindsight, the workshould have been more focused on research, even when overlapping with project partners, than on development.

Björn Grunwald, Lubos Polerecky, Nikolaus Vlachopoulos

Various software units were developed to support research with planar optodes and microsensors.

Look@O2: A stand-alone application providing a quick view at the oxygen images measured by the MOLLI system. In addition to the basic functionality of displaying oxygen images, the program allows extraction of horizontal/vertical profiles, export of images into EPS/PNG graphics formats.

O2dyn: A set of scripts and GUIs (graphical user interface) for analysis, visualisation and quantification of anything associated with the measurement of oxygen dynamics in two dimensions using planar oxygen optodes. It is used for the measurements of oxygen consumption rates with planar optodes, of a spatial variability of oxygen consumption rate in sediment with ripples, and two-dimensional distribution of photosynthetic activity of microbial mats.

INSIGHT: This is a stand-alone program for microprofile measurements to replace the existing LabView program. It is used for the positioning and data acquisition during the microprofile measurements. The program has become our standard.

L@MP: This is a GUI for rapid analysis and visualisation of large numbers of microprofiles, e.g. as obtained during long-term lander measurements. The program saves a considerable amount of time and effort and has been successfully.

Fit-Profile: A simple stand-alone application for fitting microsensor profiles in order to calculate spatial distribution of production/consumption rates. The program is a substitute for the program PROFILE that has proved to be difficult to operate and is very sensitive to boundary conditions. The commercialization of INSIGHT, L@MP and Fit-Profile, as a tool-box for microprofile measurements, is under consideration.
Using the existing planar optode equipment a system for imaging PAM (Pulse Amplified Modulation of chlorophyll fluorescence) is build. Essentially the same components for the planar optodes were used, but the software was adapted. PAM allows calculation of the electron flow through PSII, and is thus a measure for photosynthesis. The exitation is done by a similar diode array, but the wavelength determines the population exited: cyanobacteria, flagelates, green algae or diatoms. The system developed is flexible. It can be used on cell level by mounting the camera and exitation light on a microscope or scan larger surfaces by using the normal camera optics. The maximum size of the imaged surface is deternmiend by the illumination intensity of the lightsource. The relation between PAM signals and oxygenic photosynthesis will be investigated by microsensors in various systems. Raphaela has started with the ameboids from foraminifera, as a simple model system. Later she will study also diatoms and cyanobacterial mats.

Björn Grunwald, Lubos Polerecky, Nikolaus Vlachopoulos