Microbial mat research: The recent past and new perspectives

Abstract

Scientists of diverse interests, and even laymen, are beginning to understand what is meant by a “microbial mat”. But this knowledge is still superficial even for the specialist, both figuratively and literally. Most of what we know of microbial mats up to this point is still relegated to the superficial upper layer or layers which are usually composed mainly of photosynthetic prokaryotes. It is these that are responsible for the accretion and for the conversion of atmospheric and aqueous CO2 into reduced energy-rich compounds on which the rest of the community is dependent. It is also these superficial layers that define most of the Precambrian remnants of microbial mats, the lithified mats or stromatolites which also contain the microfossils that are often recognizable as morphotypes of cyanobacteria. The laminae or underzones of even living mats are still “black boxes” for the most part, with little known of the actual microbial makeup, the matrix of exopolymers, and of the species interactions and metabolic activities. Although the microbial mat community may be regarded as an ecosystem characterized by primarily a molecular flow of carbon and chemical energy (since grazing invertebrates and even smaller phagotrophs are generally rare or absent), most mat communities are now known to be of considerable taxonomic and biochemical complexity, and a great diversity of communities exists.