Buried in the sedimentary layers blanketing our planet lies compelling evidence that microbial communities called microbial mats function as Gaia's foundation - ensuring the continuity of life on Earth despite repeated catastrophes...

Buried in the sedimentary layers blanketing our planet lies compelling evidence that microbial communities called microbial mats function as Gaia's foundation - ensuring the continuity of life on Earth despite repeated catastrophes. These living laminae weave the biochemistries of ancient microbial life into modern ecosystems, embodying both the resiliency and interdependence required for self-regulated biospheres.

Mats arise wherever physical, chemical and light gradients intersect - at hydrothermal vents, evaporative lagoons, arctic ice sheets. Diverse yet stratified, they comprise the complete metabolic toolkit in one stable, miniature ecosystem. Through tight recycling of elements like carbon, nitrogen and sulfur, microbial consortia modulate surrounding environments, sculpting habitable zones.

This local stabilization scales up. Models reveal how vast interconnected mat ecosystems could regulate global temperatures and atmospheres.¹ On the early anoxic Earth, versions rich in methanogens and anoxygenic phototrophs likely maintained greenhouse warming. Later mats fixed and fine-tuned atmospheric oxygen levels.

The mat microcosm also demonstrates how cooperation and division of labor between microbes emerges from competition for resources. Different species consume others' byproducts, closing element cycles. This builds robust, resilient ecosystems where sudden losses of some members scarcely affect the whole.

And when the whole is disrupted, mats retain the seeds. Half the history of complex life lurks latent within their minute menagerie: the genes, spores and cysts to reboot. However severely damaged, mats recover. At Laguna Figueroa, after burial under five meters of sediment, cyanobacteria, purple phototrophs and sulfide oxidizers reclaimed their light-bathed locus in under a decade - and resumed depositing laminations.² Such resilience over almost four billion years of continuous existence makes microbial mats Earth's most enduring communities.³

What cataclysms might have been weathered this way over the mats' vast lifespan? Their very antiquity testifies to fortitude. In ocean shallows circumscribing early continents, mats likely served as refugia during meteoric bombardment, sustaining habitats between sterilizing strikes. Photosynthetic films would swiftly regrow across new lava flows and craters.

Later, complex multicellular organisms evolved from and alongside mats, inheriting their transcendence of catastrophe. Plants and animals emerged bearing fully-developed detoxifying, stress-managing toolkits perfected by aeons of microbial mats enduring extreme, unstable environments. Handed down not through generations but through lateral gene sharing, mat-honed genomic resilience empowers all complexity that followed, right up to humans.  

Seen in this light, microbial mats anchor the self-regulating systems that maintain planetary conditions favorable for life over geological spans - despite external shocks. These immortal living laminae continue to rebuild tattered webs, replenish depleted chemical pools and reseed scorched earth, ensuring Gaia's habitability. They accomplish as integrated communities what no individual species can, communicating in gases, nutrients and wavelength-coded signals. Here, in the densely participatory pavement between geology and biology, lies the fountainhead of homeostatic planets.

Reference

1. Downing, K. and Zvirinsky, P. 1999. Simulated evolution of biochemical guilds: reconciling Gaia theory and natural selection. Artificial Life. 5: 291-318

2. Stolz, J.F. 1984. Effects of catastrophic inundation on microbial mat community structure. PhD Thesis. Boston University.

3. Awramik, S.M. and Barghoorn, E.S. 1977. The Gunflint microbiota. Precambrian Research. 5: 121-142.