Organic Falls

When a whale dies or a tree is washed out to sea, it will eventually sink to the deep seafloor. The carcass or piece of wood prompts a feeding bonanza with animals coming from near and far for a meal or shelter. This is what is termed an organic fall. Organic-falls support specialized communities within the deep sea, yet large-scale patterns of connectivity and biodiversity between these ecosystems have remained largely unexplored. Bone-eating Osedax polychaete worms and the wood-boring Xylophaga bivalves, play an important role as ‘ecosystem engineers’; driving the decomposition of the substrates whilst increasing the organic matter and habitat availability to a wider community of deep-sea organisms. There have also been hundreds of new species discovered at organic falls.

My Ph.D. research focused on the ecology of organic falls, Osedax worms and Xylophaga clams and the biogeography of these habitats in our world’s oceans. My fieldwork has led me to wrangle with smelly whale bones and wood in Antarctica, the Bahamas, the Cayman Trench, Hawaii, Washington and Oregon. I’ve also helped dissect a sperm whale, described several new species of Osedax, micro-CT scanned wood recovered from the deep-sea, and analysed the first natural whale fall found in the Southern Ocean. I still try to work on organic-fall projects in my limited spare time and hope that in my future deep-sea career, I can resume this type of research!

Here are some of my research papers on organic falls:

  1. Amon, D.J., A.G. Glover, H. Wiklund, L. Marsh, K. Linse, A.D. Rogers and J.T. Copley, 2013. The discovery of a natural whale fall in the Antarctic deep sea. Deep Sea Research Part II: Topical Studies in Oceanography 92(0): 87-96.
  2. Macpherson, E., D.J. Amon and P.F. Clark, 2014. A new species of Munidopsis from a seamount of the Southwest Indian Ocean Ridge (Decapoda: Munidopsidae). Zootaxa 3753(3): 291-296.
  3. Amon, D.J., H. Wiklund, T. Dahlgren, C.R. Smith, K.M. Kemp, J.T. Copley, A. Jamieson and A.G. Glover, 2014. Three new species and two new records of the siboglinid genus Osedax from the deep Antarctic. Zoologica Scripta 43(4): 405-417.
  4. Smith, C.R., A.G. Glover, T. Truede, N.D. Higgs and D.J. Amon, 2015. Whale-fall ecosystems: recent insights into ecology, paleoecology and evolution. Annual Review of Marine Science 7: 571-596.
  5. Amon, D.J., D. Sykes, F. Ahmed, J.T. Copley, K.M. Kemp, P.A. Tyler, C.M. Young and A.G. Glover, 2015. Seeing in the dark: Ecosystem functions of the wood-boring genus, Xylophaga revealed by micro-computed-tomography. Frontiers in Marine Science 2:10. doi: 10.3389/fmars.2015.00010
  6. Amon, D.J., J.T. Copley, T.G. Dahlgren, T. Horton, K.M. Kemp, A.D. Rogers and A.G. Glover, 2015. Observations of fauna attending wood and bone deployments from two seamounts on the Southwest Indian Ridge. Deep-sea Research Part II: Topical studies in Oceanography doi:10.1016/j.dsr2.2015.07.003
  7. Amon, D.J., A. Hilario, P. Martinez Arbizu, C.R. Smith, 2016. Observations of organic falls in the abyssal Clarion-Clipperton Zone, tropical eastern Pacific Ocean. Marine Biodiversity. doi: 10.1007/s12526-016-0572-4
  8. Smith, C.R., D.J. Amon, N.D. Higgs, A.G. Glover, E.L. Young, 2017. Data are inadequate to test whale falls as chemosynthetic stepping-stones using network analysis: faunal overlaps do support a stepping-stone role. Proceedings of the Royal Society B 20171281.
Dissecting a porpoise found dead on a UK beach at the Natural History Museum, London. Photo credit: Diva Amon.
Figure 4
Micro-CT scan of a block of wood showing the burrows of Xylophaga murrayi, a wood-boring mollusc. Photo credit: Diva Amon.
Still clean prior to dissecting a sperm whale that had stranded and died in Kent, UK. Photo credit: Diva Amon.
fauna combined
Eight new species found living on the first natural whale fall to be discovered in the Southern Ocean. Photo credit: Diva Amon.

Below is a video of a micro-CT scanned piece of wood recovered from 500m depth in the Bahamas. The brown is wood, grey are the burrows (air), and green are the wood boring Xylophaga molluscs.