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An Empire Lacking Food

Once viewed as a barren expanse, the deep seafloor is a biologically elaborate ecosystem whose fate is tied to life above, near the sea surface

Craig McClain

An Uncertain Future

I write about our growing insight into the deep sea as Earth is entering another period of momentous fluctuation. As the emission of greenhouse gases changes our planet’s climate, evidence is growing that we have already altered the production and movement of carbon in the oceans. Recent work demonstrates that some areas in the oceans have seen 50-percent reductions in phytoplankton production, whereas others have experienced 50-percent increases. Daniel Boyce of Dalhousie University and his colleagues recently reported that phytoplankton production globally has declined over the last century. This redistribution and reduction of carbon at the ocean surface could alter the deep sea in profound ways in the near decades. Yet, changes in carbon cycling are just one of many daunting threats facing the oceans. A combination of overfishing, pollution, mining, warming and acidification may prove a dangerous cocktail.

Deep-sea organisms exist at environmental extremes of temperature, pressure and, of course, food availability. Across levels of biological organization, from individuals to the ecosystem, extraordinary ecological and evolutionary transformations have taken place in lockstep with those limits. As human activity further alters the deep sea, will its species adapt or perish?


  • Bambach, R. K. 1993. Seafood through time: changes in biomass, energetics, and productivity in the marine ecosystem. Paleobiology 19:372–397.
  • Boyce, D. G., M. R. Lewis and B. Worm. 2010. Global phytoplankton decline over the past century. Nature 466:591–596.
  • Finnegan, S., C. R. McClain, M. A. Kosnik and J. L. Payne. In press. Escargot through time: An energetic comparison of marine gastropod assemblages before and after the Mesozoic Marine Revolution. Paleobiology
  • Foster, J. B. 1964. The evolution of mammals on islands. Nature 202:234–235.
  • Herring, P. J. 2007. Review. Sex with the lights on? A review of bioluminescent sexual dimorphism in the sea. Journal of the Marine Biological Association of the UK 87:829–842.
  • Haddock, S. H. D., C. W. Dunn, P. R. Pugh and C. E. Schnitzler. 2005. Bioluminescent and red-fluorescent lures in a deep-sea siphonophore. Science 309:263.
  • Grassle, J. F. 1989. Species diversity in deep-sea communities. Trends in Ecology and Evolution 4:12–15.
  • Grassle, J. F., and H. L. Sanders. 1973. Life histories and the role of disturbance. Deep-Sea Research 34:313–341.
  • McClain, C. R., A. Boyer and G. Rosenberg. 2006. The island rule and the evolution of body size in the deep sea. Journal of Biogeography 33:1578–1584.
  • McClain, C. R., and J. Barry. 2010. Habitat heterogeneity, biogenic disturbance, and resource availability work in concert to regulate biodiversity in deep submarine canyons. Ecology 91:964–976
  • Mosely, H. N. 1880. Deep-sea dredging and life in the deep sea. Nature 21:591-593.
  • Rex, M. A. 1973. Deep-sea species diversity: Decreased gastropod diversity at abyssal depths. Science 181:1051–1053.
  • Rex, M. A., C. T. Stuart, R. R. Hessler, J. A. Allen, H. L. Sanders and G. D. F. Wilson. 1993. Global-scale latitudinal patterns of species diversity in the deep-sea benthos. Nature 365:636–639.
  • Robison, B. H., K. R. Reisenbichler and R. E. Sherlock. 2005. Giant larvacean houses: Rapid carbon transport to the deep seafloor. Science 308:1609–1611.
  • Ruhl, H. A., and K. L. Smith. 2004. Shifts in deep-sea community structure linked to climate and food supply. Science 305:513–515.
  • Thiel, H. 1975. The size structure of the deep-sea benthos. Internationale Revue des Gesamten Hyrdobiologie 60:575–606.
  • Yasuhara, M., and T. M. Cronin. 2008. Climatic influences on deep-sea ostracode (Crustacea) diversity for the last three million years. Ecology 89:S53–S65.

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