From a traditional definition "metabolomics" measures the concentrations of the large numbers of naturally occurring small molecules (called metabolites), that are produced as intermediates and end-products of all metabolic processes in living systems. They are analyzed from biological samples and body fluids such as urine, saliva, blood plasma, tissue sample or complex endogen microbiota; even the simple breath (exhaled breath condensates) can carry the information about the state of health of the considered organisms or holobionts. In environmental samples the information retrieved from small molecule analysis cover the residual biosignatures of various (micro)biomes active in the analyzed geo-samples in addition to the signature of their relatively transformed biomolecules in decay and biotic/abiotic geochemical processes. The total number of different metabolites is still unknown; some estimation range from few ten thousands to about one million, but even this latter estimate may be conservative; including plant and bacterial metabolites that are not necessary to keep the organism alive, also referred to as secondary metabolites, the number is enormously larger. The probable number of metabolites is also considerably larger than the number of corresponding genes, so it seems that the currently available databases cover at best 5% of the total number of existing metabolites. With our integrated analytical approaches (LC-MS, NMR and ICR-FT/MS) data we annotate from databases around 10% of the experimental signals.

Environmental metabolomic, as the comprehensive study of metabolic reactions in the environment (e.g. soil sediments, surface and marine waters), is growing very rapidly and integrates the knowledge of earlier developed Omics-branches including the metagenome information. Especially ICR-FT/MS describes highly complex mixtures in complex systems on the level of the elementary composition distribution and is shown in this presentation as an dedicated and innovative mass spectrometry tool to understand the composition and processes on a molecular level in various environmental systems with a a focus on marine systems .