|Bernhard, J. M., Buck, K. R., Farmer, M. A., Bowser, S. S., The Santa Barbara Basin is a symbiosis oasis, Nature, 403: 77-80, 2000|
It is generally agreed that the origin and early diversification of Eucarya occurred in the late Archaean or Proterozoic Eons when atmospheric oxygen levels were low and the risk of DNA damage due to UV radiation was high. Because deep water provides refuge against UV radiation, and early eukaryotes may have been aerotolerant anaerobes, deep-water dysoxic environments are likely settings for primeval eukaryotic diversification. Fossil evidence demonstrates that deep-sea microbial mats, possibly of sulfur bacteria similar to Beggiatoa, existed during that time. Here we report on the eukaryotic community of a modern analog, the Santa Barbara Basin (SBB; California, USA). The Beggiatoa mats of these severely dysoxic and sulfidic sediments support a surprisingly abundant protistan and metazoan meiofaunal community, most members of which harbor prokaryotic symbionts. Numerous SBB taxa are new to science, and both microaerophilic and anaerobic taxa appear to be represented. Compared to nearby aerated sites, the Santa Barbara Basin is a "symbiosis oasis" offering a new source of organisms for testing symbiosis hypotheses of eukaryogenesis.