Respiration below the euphotic zone

Seawater concentrations are the mean values of dissolved P, N and C in the deep ocean and the atmospheric saturation value in the atmosphere. Availability ratio refers to the concentrations of dissolved N, C and O2 relative to P. Use ratio refers to the relative stoichiometry of P, N, C, and O2 during respiration. 

Dissolved bioactive element Seawater concentration (Mmol kg-y Availability ratio Use ratio Availability/use 

The other major trend in ocean chemistry that results from deep respiration and large-scale ocean circulation is the general 

Surface water dissolved phosphate distribution, illustrating the relatively high concentrations (in j,mol kg ) in the Southern Ocean. From Ocean Data View (Schlitzer, 2002). 

Oxygen profiles in the ocean do not continually decrease with depth (Fig. 1.4). A typical dissolved O2 profile exhibits a minimum that is positioned above 1000 m. The main processes that contribute to this profile are the rapid and efficient respiration of settling organic matter (with more than half being degraded between 100 and 

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Fig. 10-13. The links between the cycling of C, N, and O2 are indicated. Total primary production is composed of two parts. The production driven by new nutrient input to the euphotic zone is called new production (Dugdale and Goering, 1967). New production is mainly in the form of the upward flux of nitrate from below but river and atmospheric input and nitrogen fixation (Karl et al, 1997) are other possible sources. Other forms of nitrogen such as nitrite, ammonia, and urea may also be important under certain situations. The "new" nitrate is used to produce plankton protoplasm and oxygen according to the RKR equation. Some of the plant material produced is respired in the euphotic zone due to the combined efforts...

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