Tuesday, January 28, 2020

The deep-sea under global change
2017Roberto Danovaro
Cinzia Corinaldesi
Antonio Dell’Anno
Paul V.R. Snelgrove

Open Archive DOI: https://doi.org/10.1016/j.cub.2017.02.046

Previous ArticlePolar oceans in a changing climate

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Summary
The deep ocean encompasses 95% of the oceans’ volume and is the largest and least explored biome of Earth’s Biosphere. New life forms are continuously being discovered. The physiological mechanisms allowing organisms to adapt to extreme conditions of the deep ocean (high pressures, from very low to very high temperatures, food shortage, lack of solar light) are still largely unknown. Some deep-sea species have very long life-spans, whereas others can tolerate toxic compounds at high concentrations; these characteristics offer an opportunity to explore the specialized biochemical and physiological mechanisms associated with these responses. Widespread symbiotic relationships play fundamental roles in driving host functions, nutrition, health, and evolution. Deep-sea organisms communicate and interact through sound emissions, chemical signals and bioluminescence. Several giants of the oceans hunt exclusively at depth, and new studies reveal a tight connection between processes in the shallow water and some deep-sea species. Limited biological knowledge of the deep-sea limits our capacity to predict future response of deep-sea organisms subject to increasing human pressure and changing global environmental conditions. Molecular tools, sensor-tagged animals, in situ and laboratory experiments, and new technologies can enable unprecedented advancement of deep-sea biology, and facilitate the sustainable management of deep ocean use under global change.



Biology of extremes

Less than 0.0001% of the deep ocean’s area (over 200 meters depth) has been investigated so far, making it the least explored biome of Earth. Indeed, we know the moon’s surface better than the deep sea floor. Deep-sea ecosystems encompass a wide range of habitats and environmental conditions, unlike any others on Earth (Figure 1). The effective absence of light beyond 200–500 meters depth precludes photosynthesis and thus greatly limits food availability. Pressures range from 20 to >1100 atmospheres, and temperatures range from –1.8 to 2°C, though fluids emitted at hydrothermal vents may reach 450°C. Compounds toxic to most animals occur in high concentrations in hydrothermal vent fluids (see the Quick guide by William Brazelton in this issue). Some deep-sea habitats can be hypoxic or anoxic.

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