Nutrient concentrations cycling

False. Pressure cycle bioreactors do not give even distribution of nutrients. If air and nutrients are introduced at a single point then O2, CO2 and nutrient concentration, as well as hydrostatic pressure, change in a cyclic manner as the medium flows around the reactor. 

Fig. 3. Measurements and simulation results for nutrient concentrations in a SBR cycle...

One of the difficulties in getting information on research already carried out in Brazil is that the dissertations of graduate students in the universities are seldom published in indexed journals. There has been no attempt to compare the cerrados with other savannas in South America, other continents, or Amazon forests because the information available from the cerrados on quantitative aspects of nutrient cycling in natural ecosystems is very meager (Baruch et al. 1996). There are several important studies reported from the Amazon region on nutrient concentrations in plants, litter decomposition, and hydrological cycles over the last couple of... 

Full-fat soybean meal is an excellent source of energy and protein with special value in diets for poultry when high nutrient concentration is required. This is the case for all turkey diets, most broiler diets, and feeds for laying hens early in the production cycle, as raw bean contain antinutrients. 

An especially important gap in the present knowledge of processes changing the characteristics of water masses within the Southern Ocean centers on the effect of the seasonal cycle, the formation and dissolution of pack ice and its associated biological processes. One aim must be to explain the paradox of the mismatch of dissolved nutrient concentration and the primary production in the pelagic ecosystems (9). One important hypothesis that needs further testing is the possibility of Fe limitation of nutrient uptake (10). 

Other models have been proposed which follow the outlines of the equations already discussed. Equations with parameters that vary as a function of temperature, sunlight, and nutrient concentration have been presented by Davidson and Clymer (9) and simulated by Cole (10). A set of equations which model the population of phytoplankton, zooplankton, and a species of fish in a large lake have been presented by Parker (II). The application of the techniques of phytoplankton modeling to the problem of eutrophication in rivers and estuaries has been proposed by Chen (12). The interrelations between the nitrogen cycle and the phytoplankton population in the Potomac Estuary has been investigated using a feed-forward-feed-back model of the dependent variables, which interact linearly following first order kinetics (13). 

There have been no studies measuring both carbon and nutrient fluxes in different morphological zones, nor studies relating net carbon sources and sinks to nutrient fluxes. For many reefs, errors in gross production and respiration are too high (10-15%) to get reliable estimates of net community production (Crossland etal, 1991) while changes in nutrient concentrations are nearly undetectable. Such experimental restrictions have limited our ability to understand the relationship between carbon and nutrient cycles in coral reefs. 

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