Redfield Richards ratio

One important determinant in setting the Redfield-Richards ratio is the species composition of the plankton. For example, green algae on average tend to have much higher N-to-P ratios (27) than the red algae (10). Even within a species, these ratios are somewhat variable as they depend on nutrient availability and physiological... 

Deviations from the Redfield-Richards ratio can also be caused by remineralization that proceeds by processes other than aerobic respiration. As shown in Figure 10.6, water samples obtained from depths where denitrification has occurred have lower dissolved inorganic nitrogen concentrations ([NOj ] + [NOH) than would be predicted from their AOU. During denitrification, nitrate is first reduced to nitrite and then to N2,... 

These formulations also include an update to the original Redfield-Richards ratio in the carbon content. Mn is omitted due to its variable stoichiometry.)... 

After considering the Redfield-Ketchum-Richards ratio (see Chapter 10) for C N P consider the analog for sulfur in land and marine biota. What key biochemical species are the major determinants of the C S relationship in biota ... 

Because phosphate is released during remineralization with no decrease in O2, the A02/AP0 produced via denitrification should be lower than that predicted by the aerobic respiration of Redfield-Richards planktonic detritus. To reach the suboxic conditions required for denitrification requires the aerobic respiration of a considerable amount of POM and, hence, release of phosphate. Thus, A02/AP0 ratios less than 138 are most likely to be found in waters with high phosphate concentrations. The prevalence of denitrification in deep waters is suggested by their low (14.7) average N-to-P ratio (Figure 8.3). Areas where the OMZ are pronoimced, such as coastal upwelling areas, have particularly low N-to-P ratios as shown in Figure 10.7. 

Trace metals are resolubilized from the biogenic hard and soft parts in much the same way as the macronutrients. Thus, the depth profiles of the trace metals with high EFs tend to be similar in shape to those of the nutrients. Efforts have been made to develop a Redfield-Richards type ratio far the trace metals in marine plankton. Surprisingly, field and lab work suggests that a relatively constant composition can be defined for whole... 

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