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Defining "Deep sea"

Jack Musick jmusick at vims.edu
Tue Aug 10 07:40:42 EST 2004

"The deep sea" is an ambiguous term.If you are talking about demersal
habitats, the edge of the continental shelf is usually taken as the upper
boudary(=~ 200m) with the Bathyal Zone extending down to 2000m. The Bathyal
can be further divided into upper(<1000m) and lower( > 1000m).Below 2000m,
you have the Abyssal, which again has been arbitrarily divided into
upper(2-3000m)and lower(>3000m).Habitats in the deep-sea trenches are in the
"Hadal" Zone.
 In the Pelagic Realm,using the 200m isobath as the usual dividing point
between coastal and oceanic water masses, you have the Epipelagic Zone which
corresponds to the euphotic zone(the area of active photosynthesis) whch
extends from the surface to 50-200m depending on productivity and water
clarity. Then the Mesopelagic from the bottom of the Epipelagic to 1000m,
the the Bathypelagic from 1000m to within tens of meters of the bottom
wherein the Benthopelagic Zone is located.
Brad Buran wrote:

> Dear colleagues,
> I am currently preparing a manuscript that examines the structure of the
> inner ears in several deep-sea species.  In the introduction, I am
> attempting to define, or at least describe, what the deep sea is (as
> contrasted with shallower waters). Since this manuscript is for a
> general morphology journal rather than an oceanography journal, I feel
> that it is essential to give the readers some background on the deep
> sea.
> Older books appear to define the deep sea as anything below 1,000 m
> beneath the surface.  However, at several recent conferences I have been
> at, people appear to refer to shallower depths (such as 250 m) as the
> deep sea.  Is anyone aware of a standard definition or a conventional
> description that is used by deep sea researchers?
> Thank you for your time,
> Bradley Buran
> ---

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