Mathematical modeling of biogenic substance transformations and recycling in a subtropical coastal marine ecosystem

Abstract

A mathematical model describing the biotransformations of organic and mineral compounds of biogenic elements (P, N, and Si) and dissolved organic carbon was applied for a theoretical analysis of the recycling of nutrients in the coastal zone of the Canary water upwelling. The aim of this study was to quantitatively estimate the effect of nutrient recycling on the dynamics of the biomasses of microorganisms as a matter basis for the biological productivity of the marine environment. Model calculations were carried out for four near-shore areas off the Moroccan Sahara using the morphometric data (mean depths, water volumes, and areas) and longterm monthly mean values of the parameters of the marine environment (temperature, light intensity, water transparency, and depth of the thermocline). In the calculations, no account was taken for the flow rates across the boundaries between the areas and only indirect account for the vertical exchange was taken. At the absence of nutrient transfer, the model reproduces particular features of the dynamics of nutrient and detritus concentrations and the biomasses of microorganisms resulting from the internal recycling of organic and mineral substances only. In order to characterize the processes of the biotransformation, the internal fluxes and turnover times of organic and mineral components were estimated together with the biomasses and biological productivities of microorganisms.