Editor's Note: The bottom of the deep sea is dark and cold and a very old habitat by most terrestrial standards. Dr. Grassle and his colleagues have shown that the benthos contains an extraordinary diversity of life with different life histories and adaptations to habitat. A combined sample from 1,500 m to 2,500 m off New Jersey that covered a mere 21m2 yielded 798 species, a diversity that approaches the upper limits of what can be found on land anywhere. Another sampling off the East Coast of North America yielded nearly 600 species. Most deep-sea species are rare, and species once recognized as “cosmopolitan” are now seen as groups of species with restricted distributions. Experience in study of this extraordinary diversity remains minuscule in proportion to the area, and estimates of the total number of species in the oceans now exceed by many orders of magnitude the earlier estimate of 160,000. The experience is similar to that in tropical forests where access to the crowns of trees has recently revealed not only new populations of birds, but thousands of new insect populations. The knowledge has caused estimates of the total number of species on earth to soar to 10 million or more. Experience with the benthos may push this number higher still.

Chronic disturbance of either the benthos or the water column increases the abundance of a few species.