Aphotic zone

Aphotic zone The deeper part of lakes, sea, and ocean where light does not penetrate. 

Antigen A foreign substance that provokes immune response when introduced into the body the body reacts by making antibodies Anthropogenic Effects produced as a result of human activities Aphotic zone The deeper parts of lakes, seas, or oceans where light does not penetrate... 

Below about 200 m, PON concentrations tend to asymptote to similar levels of about 0.1 to 0.3 pmol kg", irrespective of the large differences in PON in the euphotic zone. Overall, PON dynamics in the aphotic zone tends to follow that of particulate organic carbon (POC), with a stoichiometric C N ratio of about 7.1 0.1 (equivalent to 16 114 2) for the particles sinking out of the euphotic zone (Schneider et al, 2003) (see also Hebei and Karl (2001) for long-term observations of the POC and PON dynamics in an oligotrophic environment). In their analysis of sediment trap samples and particles collected by in situ pumps, Schneider et al (2003) also noticed a slight increase of this ratio with depth of about 0.2 per 1000 m, so that particles sinking across 1000 m have a C N ratio very close to the 117 16 ratio proposed by Anderson and Sarmiento (1994). 

Yakushev, E. V., and Neretin, L. N. (1997). One-dimensional modeling of nitrogen and sulfur cycles in the aphotic zones of the Black and Arabian Seas. Global Biogeochem. Cycles 11(3), 401-414, doi 10.1029/97GB00782. 

Aphotic zone oxygen consumption rates that, when vertically integrated, provide a net water column oxygen demand that can then be related stoichiometrically to a carbon export flux. 

Figure 2 Aphotic zone oxygen consumption rates as a function of depfh for fwo locales in fhe subfropical North Atlantic. These consumption rates are based on tritium- He dating and other tracer techniques.

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