Preformed nutrients

Krom M. D., Brenner S., Isradlov L. and Krumgalz B. (1991) Dissolved nutrients, preformed nutrients and calculated elemental ratios in the south-east Mediterranean Sea. Oceanol. Acta 14, 189 194. 

After seeding the nutrient medium with the preformed inoculum previously described, the mixture was subjected to agitation and aeration under aseptic conditions for 72 hours at 27°C to 28°C for the first 24 hours, then at 25°C to 26°C for the next 48 hours during this period, the pH was in the range of 6.4 to 6.8. Aeration was accomplished by cultivation under submerged conditions at an air flow rate of one volume of air per volume of medium per minute. After termination of the process, the mycelium was removed by filtration and the filtered broth found to contain 450 7of oleandomycin per ml of solution. 

Microbial insecticides are very complex materials in their final formulation, because they are produced by fermentation of a variety of natural products. For growth, the bacteria must be provided with a source of carbon, nitrogen, and mineral salts. Sufficient nutrient is provided to take the strain of choice through its life cycle to complete sporulation with concomitant parasporal body formation. Certain crystalliferous bacilli require sources of preformed vitamins and/or amino acids for growth. Media for growing these bacilli may vary from completely soluble, defined formulations, usable for bench scale work, to rich media containing insoluble constituents for production situations (10,27). Complex natural materials such as cottonseed, soybean, and fish meal are commonly used. In fact, one such commercial production method (25) is based on use of a semisolid medium, a bran, which becomes part of the final product. 

It follows that deep seawater contains nutrients from two sources. First, it may contain nutrients that were present with the water when it sank from the surface. These are called preformed nutrients." Second, it may contain nutrients derived by the in situ remineralization of organic particles. These are called oxidative nutrients. 

The preformed nutrients are obtained by subtracting the oxidized nutrient from total nutrient (for N and P). 

For silica an additional component of silicic acid generated by inorganic dissolution also occurs. One can estimate oxidized" Si as being 23/138 AOU, but discrimination between preformed Si and inorganic Si is not possible. Representative profiles of PO4, NO3, and Si are given in Fig. 10-19. Note that after subtracting the oxidative nutrients the preformed values are relatively constant. 

Niacin was discovered as a nutrient during studies of pellagra. It is not strictly a vitamin since it can be synthesized in the body from the essential amino acid tryptophan. Two compounds, nicotinic acid and nicotinamide, have the biologic activity of niacin its metabolic function is as the nicotinamide ring of the coenzymes NAD and NADP in oxidation-reduction reactions (Figure 45-11). About 60 mg of tryptophan is equivalent to 1 mg of dietary niacin. The niacin content of foods is expressed as mg niacin equivalents = mg preformed niacin + 1/60 X mg tryptophan. Because most of the niacin in cereals is biologically unavailable, this is discounted. 

The global efficiency of the biological pump can be evaluated in terms of a global mean preformed nutrient concentration for surface water that is folded into the ocean interior. In the calculation of this mean preformed nutrient concentration, each subsurface water formation... 

Within the polar oceans involved in deep water formation, certain regions are more important than others. The Antarctic Zone, the most polar region in the Southern Ocean, is involved in the formation of both deep and intermediate-depth waters, making this region important to the atmosphere/ocean CO2 balance. The quantitative effect of the Subantarctic Zone on atmospheric CO2 is less certain, depending on the degree to which the nutrient status of the Subantarctic surface influences the preformed nutrient concentration of newly formed subsurface water (Antarctic Intermediate Water and Subantarctic mode water), but its significance is probably much less than that of the Antarctic. 

The concept of nutrient and O2 change along a surface of constant density in the upper ocean is illustrated in Fig. 6.18. When waters subduct (surface waters flow along density horizons into the thermo-cline) it is assumed that they carry with them O2 concentrations near saturation equilibrium with the atmosphere and preformed nutrient concentrations. The assumption of saturation equihbrium is not exactly correct but in most cases this is probably not a serious error because surface oxygen measurements indicate near-saturation equilibrium everywhere except in the Southern Ocean south of the polar front, where concentrations can be up to 10% undersaturated. As a water parcel moves along a constant-density surface into the upper thermocline, respiration consumes the O2 concentration while creating nutrients and AOU in the water mass. At any point in the ocean interior, preformed nutrient concentrations can be calculated if one knows the temperature, salinity (for determining [02 ), nutrient and O2 concentrations. 

A useful apphcation of preformed nutrient concentrations is that they are intrinsic to different water masses and sometimes can be used as conservative tracers. For example, the main sources of deep water in the Pacific Ocean are North Atlantic Deep Water (NADW), Antarctic Intermediate Water (AAIW) and Antarctic Bottom Water (AABW), all of which are at least partly homogenized in the Antarctic Circumpolar Water (AACW). It is not possible to determine how much of each of these sources contributes to Pacific deep water by using end member mixing of the conservative properties temperature and salinity because salinities of the end members are not sufficiently different. Since concentrations of DIP are well above detection limits in... 

A) A schematic cross section of the upper ocean, illustrating surface water values and trends on subsurface isopycnals for O2, AOU, preformed nutrients, P , and time since the water mass was at the surface, t. (B) Schematic plots of O2, P, AOU and t versus locations 1,2,3 and 4 in (A) and a plot of AOU versus t used to derive oxygen utilization rates (OUR). 

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