aphotic zone

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aphotic zone:

see oceanocean,
interconnected mass of saltwater covering 70.78% of the surface of the earth, often called the world ocean. It is subdivided into four (or five) major units that are separated from each other in most cases by the continental masses. See also oceanography.
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aphotic zone

[a′fäd·ik ‚zōn]
(oceanography)
The deeper part of the ocean where sunlight is absent.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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[L.sup.-1] for PC and 1.51 [+ or -] 2.0 [mm.sup.3].[L.sup.-1] for PD) and aphotic (0.53 [+ or -] 0.7 [mm.sup.3].[L.sup.-1] for PC and 0.29 [+ or -] 0.5 [mm.sup.3].
The 36 % reduction in P agardhii biomass in the aphotic zone at PC (October 2007) favored increases in coccoid cyanobacteria biomass in the functional groups M and K.
Organismal transparency (rather than simply ocular) is extremely rare on land, rare in the aquatic benthos, uncommon in aphotic regions, somewhat more common in dysphotic and neustonic habitats, and ubiquitous at euphotic depths in clear water.
As mentioned above, transparent species are rare at aphotic depths, generally being replaced by species with whole-body red or black pigmentation (Hardy, 1956; Herring and Roe, 1988; McFall-Ngai, 1990).
This observation is analogous to the relationship between the photic and aphotic zones in the open ocean; however, there are significant differences between coastal systems and the open ocean.
A vertical division of the ocean would divide it into an upper illuminated (photic zone) and a lower dark aphotic zone.
In oplophorid shrimps, sensitivity to polarized light may be present in animals from the upper mesopelagic zone, but absent in those active under aphotic conditions (Gaten et al, 1992).
Thus, transport of organic materials, nutrients, and prey can sustain communities of abundant consumers even in places with little or no primary productivity, e.g., caves, mountaintops, snowfields, other terrestrial areas devoid of vegetation (e.g., polar areas, new volcanic zones, some barren deserts and islands), marine aphotic zones, central oceanic gyres, and phytotelmata (see references in Polls et al.
Seasonal /1985 and sampling June-July 1999-2000; /1987 monthly sampling 2001-2006 Depths 2; 5; 10; 2; 5; 10; 100; 15; 1% 15; 20; 15; 20; 25; of incident 25; 30 m 30 m light and aphotic zone (Secchi) Total-P -- -- Mackereth et al.
This is perhaps most easily seen if one recognizes the fact that the formulation is mathematically equivalent to the steady-state description of an idealized two-layer model of the ocean with a perfectly mixed photic zone, no sedimentary loss, and all mineral nutrients from organisms transported into the aphotic zone by turbulent diffusion being immediately remineralized.
aphotic zones, and under isolated and grouped conditions.