M. Eichinger

Address:	Oceanology Centre of Marseille (COM) Laboratory of Microbiology Geochemistry and Marine Ecology (LMGEM) Campus de Luminy Case 901 13288 MARSEILLE Cedex 09
Phone:	0033-0491829126
Email:	eichinger@univmed.fr
Specialization:	Marine ecology
Project:	DOC degradation by marine bacteria in the water column
Publications:

DOC degradation by marine bacteria in the water column

an experimental and modelling approach

Introduction

Dissolved organic carbon (DOC) is recongnised as one of the largest pools of reduced carbon on the Planet. This DOC is almost exclusively consumed by bacteria, which represent the most important biomass in aquatic systems. Despite of this importance in oceans, only a few aquatic biogeochemical studies describe the performance of bacteria, and they do so in simplistic ways. To improve this situation, we first need to better understand the interactions between bacteria and DOC.

Objectives

We want to demonstrate (1) that classical empirical models are not suitable to describe bacterial dynamics in realistic environmental situations, and (2) that we have to turn to more mechanistic models. As experiments with bacteria and DOC are generally done in steady state situations, we first have to obtain data sets under more realistic environmental conditions. Consequently, this study will be based on a modelling and an experimental approach.

Methods

A first study, based on biodegradation data from natural seawater, demonstrated that classical degradation kinetics, as Monod-like models, are not sufficient to describe DOC - bacteria interactions (Eichinger et al. 2006). We have then decided to put our attention to more mechanistic models by using DEB theory. To test a mechanistic model and estimate its parameters we need data sets obtained in variable environments. Consequently, we have carried out some experiments by measuring multiple variables: DOC (substrate), particulate organic carbone (POC) (bacterial biomass), respiration, abundance (microscopy and flow cytometry counts), optical density and biovolume. These experiments have been conducted with only one bacterial species and one limiting carbon substrate. This substrate has been put in several batches, in the same quantity, in two ways: either in the beginning of the experiments, or by pulses in during the experiment. These data sets will be used to test the model, estimate the parameters, and adapt the model, if necessary.

This is the symposium that closed my project

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