Metaproteomics is a new field within the 'omics' science which investigates 
protein expression from a complex biological system and provides direct evidence 
of physiological and metabolic activities. Characterization of the metaproteome 
will enhance our understanding of the microbial world and link microbial 
communities to ecological functions. Recently, the availability of extensive 
metagenomic sequences from various marine microbial communities has extended the 
postgenomic era to the field of oceanography. Although still in its infancy, 
metaproteomics has shown its powerful potential with regard to functional gene 
expression within microbial habitats and their interactions with the ambient 
environment as well as their biogeochemical functions. However, the application 
of metaproteomic approaches to complex marine samples still faces considerable 
challenges. This review summarizes the recent progress in marine metaproteomics 
and discusses the limitations of and perspectives for this approach in the study 
of the marine ecosystem. This article is part of a Special Issue entitled: 
Trends in Microbial Proteomics.