Nutrient-limitation is defined as an increasE in the rate of a metabolic response with an increase in nutrient flux or concentration. There is increasing evidence that plants, animals with zooxanthelise, and communities of coral reefs exhibit nutrient-limited responses for photosynthesis and net productivity. In this way aspects of community productivity of coral reefs can be nutrient-limited. The term nutrient-regulation is introduced to describe changes in characterimitics of communities brought about by nutrient additions that are not rate processes i.e trophic structure.
Comparisons between the rate of nutrient uptake and the rates of nutrient supply are discussed on several different spatial scales to introduce new ways of approaching the study of nutrient recycling. The maximal rate of phosphorus (P) uptake by reef communities appears to be slow compared to the rate of P supply by flowing water. There are no adequate measurements of the maximal rate of N uptake so it is difficult to make this analysis for N compounds. Also, an example is presented in comparing the ratios of the rates of nutrient uptake (i.e. in this case C and P) to the C and P ratios in the biomams. The results of this analysis indicates that reef communities do not recycle P tightly relative to C. This approach can be applied to different spatial and temporal scales, giving us a more unified direction in studying the problems of nutrient utilization in coral reef ecosystems.
Three areas of research are suggested; 1) measurements of the maximal exchange rates of nutrients between water and organisms and comparing those rates with rates of supply; 2) determination of the mechanisms controlling nutrient uptake at the community scale; 3) determination of the variability in C, N and P in biomass.