ARCHIVE: 25 Things You Should Know About the Deep Sea: #3 The Vast Majority of the Deep-Sea Remains Completely Unexplored

Although the earliest interest and sampling in the deep sea occurred in the late 1800’s, a majority of deep-sea exploration did not occur until after the 1960’s. The current amount of sampling and exploration of this great environment is without precedent. Despite this, new species and new habitats are constantly being found (e.g. Roxanne…You Don’t Have to Put on the Red Light!). Hydrothermal vents were not discovered until 1976. So how much of the deep sea has actually been explored or sampled? This is indeed a tough question to answer. To derive an exact answer we would have to know of every single sample of every deep-sea expedition taken plus all the submersible and ROV dives and how much area they have covered. Of course this is extremely unreasonable, but an exercise in estimation…

ROVS and Submersibles
Total Number of ROVS and Submersibles 20
Total Number of Operational Years 30
Total Number of Dives Per Day 1
Total Number of Lifetime Dives 153600
Total Distance Covered in Each Dive (km) 1
Effective Viewing Distance (m) 10
Area Covered Per Dive (km2) 0.01
Total Area Covered by ROV and Submersibles (km2) 1536

Trawls and Sledges
Average Trawl Distance (km) 1
Average Trawl Opening (m) 5
Total Area Sampled Per Trawl (km2) 0.005
Number of Total Trawls 20000
Total Area Covered by Trawls and Sledges 100

Core Size (m2) 1
Total Number of Cores 20000
Total Area Covered by Cores (km2) 0.02

Benthic Landers
Total Number of Benthic Landers 20
Total Visual Field (km2) 1
Total Area Covered by Landers (km2) 20

Total Area of Deep Sea Sampled (km2) 1656.02
Earths Surface Area (km2) 150000000
Percentage of Surface Covered by Deep Sea 70.8%
Area of Deep Sea (km2) 106200000
Percentage of Deep Sea Area Covered 0.0016%

The above estimate is likely to be unreasonably high for several reasons. The assumption that all the ROV’s/submersibles dive every day is unreasonable and does not take into account downtime for travel to sampling sites or maintenance. Likewise, although the total number of ROV’s/submersibles is near the current total estimate not all of these have been in operation since 1975, although the Alvin was commissioned in 1964. I also feel that the total distance covered per dive is high, especially when dives visit specific features such as hydrothermal vents or methane seeps. Perhaps more importantly, the assumption that each of the above samples/dives were taken in a unique location is unlikely has ROV’s/submersibles dives frequently return to specific sites. I can adjust these parameters (reduce the operational years to 20, dives occur every other day, and limit travel distance to 0.75km) the estimate falls to 504.03 km2 or 0.0005% of the deep-sea floor. In addition, the trawl distance, average trawl opening, total number of trawls and cores, and field of few for the benthic landers are likely to be high as well.

Because these are rough calculations, I encourage any comments or revisions to these estimates.

Dr. M (1768 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

7 comments on “ARCHIVE: 25 Things You Should Know About the Deep Sea: #3 The Vast Majority of the Deep-Sea Remains Completely Unexplored
  1. Not a relevant comment to the post, but just wanted to say that this is a really nice addition to ScienceBlogs. Good stuff, and long me it continue.

  2. Thanks for calculating that…i’ve always assumed it was gonna be an extremely low number…just never sat down to figure it out.

    As multibeam bathymetry mapping gets better and better I think it will drive more and more drilling/sampling…I hope.

    In case you don’t already have it, download GeoMapApp…it’s a Java program for exploring the world’s sea floor bathymetry. Not as slick and cool as GoogleEarth, but it’s getting there.

  3. Remember of course that the number is always going to be small because of the shear magnitude of the deep sea. And of course its just a ballpark but most estimates I hear are closer to 5 which is obviously no right. Thanks for the link to GeoMapApp will take a look at it.

  4. I think this depends on what you mean by “explored”, more specifically at what level of detail. As a kind of straw man example – how much of the deep sea has been sounded for depth at a 100 square meter level. If we don’t think there is anything interesting smaller than that (Say the whole deep sea was mostly dead), then we could say we have “explored” all those areas. As you go to smaller and smaller areas of interest the size of the explored areas would be smaller, but again depending of how representative these things are, statistically it could be we are exploring a larger area. It seems like from your articles though that the exciting thing is that there is still opportunity to find wholly new ecosystems or new types of material deposits.

    As another example from the deep see – how much of the 3-d ocean have we explored and does that matter – is that part much more uniform so that looking at one part is a lot like looking at another? I would bet there are whole systems (that is, multiple interacting species of different sizes) at levels in the body of the oceans we don’t even know about yet.

  5. Your right Markk in suggesting that how much of an area can we characterize with a single sample, the window if you will. If for example a box core adequately characterizes the organisms in 100m2 then this estimate goes up. The problem though is this may not be the case. The pelagic system also appears to be quite patchy and explore even less than the bottom. Efforts by Bruce Robinson and Steve Haddock at MBARI are trying to change this.

  6. Great post and series. I do have one possible erroneous quibble, and that would be the number of cores.

    As best I understand it, the major petroleum companies have been doing a lot of core sampling for years. Unfortunately, they consider this to be among their most confidential of assets, and are loath to share the results with researchers outside of their company.

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