… But don’t panic. Apparently, this is normal.
It turns out that bacteria living at the bottom of the sea are far more abundant and diverse than scientists had previously thought. These bacteria appear to be consuming the planet’s oceanic crust. This raises several interesting questions regarding the interaction and co evolution of life on Earth and the Earth itself.
A 60,000 kilometer seam of basalt is exposed along the mid-ocean ridge spreading system, representing potentially the largest surface area for microbes to colonize on Earth
This is not the first time sea floor microbes have been detected, but it is the first time that the abundance and diversity of microbes living on the hard basaltic substrate have been quantified. This paper reports thousands of times more bacteria on the sea floor than in the water above, at more than one study site. The sea floor has equivalent levels of bacterial diversity as farm dirt, which was previously believed to be the richest bacterial habitat.
According to David Garrison of the NSF:
These scientists used modern molecular methods to quantify the diversity of microbes in remote deep-sea environments… As a result, we now know that there are many more such microbes than anyone had guessed
From the study in Nature:
a, Species richness of Bacteria inhabiting EPR seafloor lavas (cumulative results) is compared with that of other ocean environments, such as the Sargasso Sea6 (partial curve), a MAR hydrothermal vent in situ growth chamber7, an EPR hydrothermal white smoker spire5, Nankai Trough deep-sea sediments8, and EPR deep sea water. The bacterial richness of the EPR basalts is also compared to a basalt-hosted community from Hawaii and other known high-richness environments (b), such as a farm soil9 (partial curve) and a hypersaline microbial mat from the Guerrero Negro10 (partial curve). Partial rarefaction curves are shown for visualization purposes; however, complete data sets were used in calculating curve projections. c, Rarefaction curves for the individual EPR and Hawaii basalt clone libraries. A partial curve is shown for HI-LPP (total clones = 246). Comparative studies in a and b are based on near full-length 16S rRNA gene sequences, and most studies are the sum of several environmental samples. OTUs are defined at a sequence similarity of greater than or equal to 97%. FG, fresh glass; LSR, Loihi seamount South Rift; LPP, Loihi seamount Pisces Peak; SP1 & SP2, South Point samples.
Statistical modeling of the total amount of energy that could be obtained from bacterial interaction with the exposed basalt at the sea floor ridges indicates that these bacteria are getting about as much energy from this source as they can.
Our calculations suggest that alteration reactions in the upper ocean crust may fuel microbial ecosystems at the sea floor and contribute to biomass production and diversity in these systems. This hypothesis supports the understanding of the phylogenetically rich and distinct nature of the basalt biotope, otherwise it may be anticipated that the basalt-hosted community would more closely match that of the surrounding environment(s), that is, sea water in the case of unsedimented mid-ocean ridges like the EPR. Enrichment of taxa from diverse metabolic groups may result from the establishment of micro-environments within or on rock cavities and surfaces during alteration, secondary mineral precipitation and biofilm formation. Niche creation would allow for a greater variety of redox reactions and metabolic pathways (for example, heterotrophic, anaerobic, or reductive) within small spatial scales, including those supporting organotrophic and mixotrophic communities. The observed microbial biomass and phylogenetic diversity may consequently be an expression of the range of diverse chemical microenvironments that develop during basalt alteration.
This lends support to the growing idea that live may have originated along sea floor ridges rather than in shallow pools on the earth’s surface, or elsewhere. It would also seem that this is potential source of energy for a widespread tropic system.
Here’s a link to a video of the scientists talking and some shots of the deep sea.
Santeli, C., Orcutt, B., Banning, E., Wolfgang, B., Moyer, C., Sogin, M., Staudigel, H., Edwards, K.Abundance and diversity of microbial life in ocean crust. Nature, 453, 653-656.