I have just composed and submitted the abstract below to the organizers of the 26th Gathering in Biosemiotics, which will be held in Sheffield, UK, July July 27-31st.
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Life in Earth – a new look at the nature of life
Morten Tønnessen
The global survey of biomass by Bar-On, Phillips and Milo (2018) has shown that subterranean life occurs at far greater depths, and is more abundant, than previously assumed. Life in the marine deep subsurface, i.e., subterranean life under the oceans, is actually more abundant than life in the oceans (ibid., see also Ruff et al. 2024). The existence of microbial, fungal and animal subterranean lifeforms raises ethical and political questions about the consequences of human activities in the marine deep subsurface and other subterranean environments.
As Dunn (2021) narrates, human beings are biased towards the organisms that look the most like us and inhabit a similar environment, while we habitually ignore the majority of odd and unfamiliar lifeforms. We know relatively little about the life that dwells in deep-sea environments – and even less about life in the deep subsurface. As is well known, photosynthesis is the dominant source of oxygen for most organisms. However, recent research documenting the assembly of ‘dark oxygen’ in deep-sea environments in the Pacific Ocean has revealed that photosynthesis is not the only source of oxygen on Earth (Sweatman et al. 2024). A further source appears to be ‘geo-batteries’ related to seawater electrolysis in seafloor areas covered by polymetallic nodules, i.e. multimetallic lumps. This discovery might change our outlook on how life has developed, and particularly our understanding of life in deep-sea and seafloor environments.
Recent research has further established that subseafloor cavities beneath hydrothermal vents are inhabited not only by microbes and viruses, but also by animals such as tubeworms and mussels (Bright, Gollner et al. 2024). Three tubeworm species included in the study of Bright, Gollner et al. (2024) uniquely rely entirely on a bacterial symbiont, which in turn “live off the chemicals released by the vents” for nutrition (The Economist, 2024). These tubeworms living in a subsurface environment below the seabed do not rely on nutrition originating from the surface – and ultimately photosynthesis drawn from energy from the sun – but rather on nutrients originating from deep inside Earth. This recent discovery of animal habitats in the subseafloor “expands the known macrofaunal biosphere” to new depths that was entirely unknown until a couple of years ago (Bright, Gollner et al. 2024: 2).
Based on these recent scientific findings, I will briefly discuss these core questions: To the best of our current knowledge, what is the full range of liveable environments on Earth, and the full spectrum of lifeforms on Earth? How do these discoveries change our outlook on the lifeworlds and biosemiosis of animals and other organisms, and how can they inform our efforts to develop more representative lifeworld models in biosemiotics?
REFERENCES
Bar-On, Y. M., R. Phillips and R. Milo (2018). The biomass distribution on Earth. Proceedings of the National Academy of Sciences (PNAS), 115 (25): 6506–11. https://doi.org/10.1073/pnas.1711842115. Includes Supplementary Information Appendix, https://www.pnas.org/doi/10.1073/pnas.1711842115#supplementary-materials.
Bright, M., S. Gollner et al. (2024), ‘Animal life in the shallow subseafloor crust at deep-sea hydrothermal vents’, Nature Communications, 15: 8466. https://doi.org/10.1038/s41467-024-52631-9
Dunn, Rob (2021). A Natural History of the Future: What the Laws of Biology Tell Us About the Destiny of the Human Species. Basic Books.
The Economist (2024), ‘Life finds a way: Tubeworms live beneath the planetary crust around deep-sea vents’. Available online: https://www.economist.com/science-and-technology/2024/10/16/tubeworms-live-beneath-the-planetary-crust-around-deep-sea-vents
Ruff, S. E. et al. (2024), ‘A global comparison of surface and subsurface microbiomes reveals large-scale biodiversity gradients, and a marine-terrestrial divide’, Science Advances, 10 (51): eadq0645.
Sweatman, A. K. et al. (2024), ‘Evidence of dark oxygen production at the abyssal seafloor’, Nature Geoscience, 17: 737–9. https://doi.org/10.1038/s41561-024-01480-8
