Skills

Principle of PAM fluorometry:

Briefly, PAM fluorometry measures the fluorescence emitted by chlorophyll in photosynthetic organisms to evaluate the efficiency and dynamics of photosynthesis. When chlorophyll absorbs light, it can use the energy for photosynthesis, dissipate it as heat, or emit it as fluorescence. The fluorescence signal reflects photosynthetic activity, as more energy is used for photochemical reactions, less fluorescence is emitted. By measuring the baseline level of fluorescence when all photosystem II reaction centers are open, and the maximum fluorescence when all PSII reaction centers are closed, we can determine how efficiently the photosynthetic apparatus converts light energy into chemical energy. This provides crucial insights into the health and performance of photosynthetic organisms. Additionally, by gradually increasing the intensity of actinic light, which drives photosynthesis, PAM fluorometry provides a comprehensive view of photosynthetic efficiency and adaptability under varying light conditions. However, for a detailed understanding of PAM fluorometry, I encourage readers to explore the extensive range of literature available on this topic.

Advantages of PAM fluorometry:

Overall, PAM fluorometers are powerful tools offering significant advantages for advancing our understanding of photosynthetic processes and ecosystem dynamics. This technology is rapid, highly sensitive, non-destructive, and non-invasive. It can be applied to a diverse range of photosynthetic organisms, from microalgae to terrestrial plants. Additionally, PAM fluorometry allows for real-time monitoring and data collection under natural conditions, providing valuable insights into the dynamics of organisms within their natural environments. These features make PAM fluorometry an invaluable asset for both laboratory and field research. 

Models used in my research to date:

Although all PAM fluorometers rely on the same fundamental principle, enabling me to proficiently use almost all products based on this technology, I have primarily utilized the following models in my research to date:

• WALZ Models (company website):

  • 1. • Water-PAM (Flow-through version, cuvette version): Used for assessing photosynthesis in liquid environments, such as phytoplankton in water samples or microalgae cultures

       • Water-PAM (Fiber version): Used for assessing photosynthesis on surfaces, such as microphytobenthic biofilms

       • Imaging PAM (MAXI version): Used for assessing fluorescence at high spatial resolution on sediment surfaces

       • Imaging PAM (Microscopy version): Used for assessing fluorescence at high spatial resolution at the cellular level

       • Multi-color-PAM: Used for assessing fluorescence from different photosynthetic pigments

       • PAM2500: Used for high-performance field measurements of chlorophyll fluorescence 

• PSI Model (company website):

  • 1. • Open FluorCam: Used for assessing fluorescence at high spatial resolution on sediment surfaces

For more information on my research and scientific contributions related to this technology, please visit the pages included in the sections Research and Productions. 

In addition to the core areas of skills previously described, I possess a range of other specialized skills and knowledge with various advanced analytical tools and techniques. This section provides a non-exhaustive overview of some additional experimental tools and methods I used, highlighting the extent of my technical and laboratory expertise.

• Experimental systems and setups

• Microcosms/Mesocosms: Employed to simulate conditions while controlling various factors such as light, temperature, tidal cycles, consumer densities, and sediment quality. These systems enable comprehensive monitoring of ecological interactions and responses in a controlled environment. See Related Work 

• Photosynthétron: Used to incubate cells under controlled light gradients and temperature conditions, allowing for detailed studies of photosynthetic processes. See Related Work

• Flow Through Reactors: Allows for continuous monitoring of microbial processes, such as the nitrogen cycle, and their interactions with different environmental conditions, including substrates, influx solutions, organic matter, and temperature. See Related Work 

• Sample preparation

• Extraction Techniques: Methods for isolating specific compounds from samples, including the use of solvents and reagents (e.g., for the extraction of exopolysaccharides or chlorophyll).

• Encapsulation for Isotopic Analysis: This process includes decarbonation to remove carbonates and ensure accurate carbon measurements. Samples are placed into tin capsules and prepared for mass spectrometry or other isotopic analysis techniques.

• Molecular Biology Analysis: Preparation of samples for genetic and molecular analyses involves steps such as homogenization, nucleic acid extraction, and purification. These procedures ensure sample integrity for PCR, sequencing, and other molecular biology techniques by removing contaminants and making them suitable for downstream applications.

• Spectroscopic Analysis

• Chlorophyll: Determined through spectrophotometric measurements, typically at 665 nm for chlorophyll a and 750 nm for chlorophyll b. The absorption values obtained are used to calculate chlorophyll concentration (e.g., using the Lorenzen method).

• Optical Density (OD): Determined through spectrophotometric measurements, typically at wavelengths such as 600 nm or 700 nm, to assess the optical density of samples. The absorption values obtained are used to estimate cell density or turbidity (e.g., following standard calibration curves).

• Exopolysaccharides (EPS): Determined through spectrophotometric measurements, typically at wavelengths of 490 nm for carbohydrate quantification (using the Dubois method) and 595 nm for protein quantification (using the Bradford method). The absorption values obtained are used to calculate EPS concentration, following specific calibration curves for each method.

• Nutrient Concentration: Measured using the Gallery Automated Multi-Parameter Analyzer, which employs spectrophotometric techniques to provide precise and efficient analysis of nutrient concentrations in samples. This analyzer can assess various nutrients such as nitrates, phosphates, and ammonium. The concentration values obtained are used to evaluate nutrient levels and dynamics within the samples.

• Bacterial Enzymatic Activities: Measured through spectrophotometric techniques that assess enzymatic activity by detecting changes in absorbance and emission at specific wavelengths. This method typically involves substrates that produce a colorimetric or fluorescent response upon enzymatic action. The spectrophotometer measures changes in absorbance (for colorimetric substrates) or emission (for fluorescent substrates), allowing for the quantification of enzymatic activity.

• NDVI (Normalized Difference Vegetation Index): Measured using spectroscopic techniques to assess the health and density of photosynthetic organisms. The NDVI is calculated by comparing reflectance values in the red (typically around 665 nm) and near-infrared (NIR, typically around 850 nm) spectra.

• Other specific analysis

• Light Measurement: Involves measuring light attenuation in sediments and assessing light microgradients in aquatic environments using PAR sensors and light sensors. 

• Plankton Diversity (Phytoplankton and Zoobenthos): Identification and quantification of plankton species using taxonomic determination keys.

• Behavioral Analysis of Cells: Observation and analysis of cellular behavior under various experimental conditions.