Sensitivity analysis of a mathematical model of phytoplankton growth and nutrient distribution in the Pacific Ocean off the northwestern U.S. coast

In a recent publication (Jamart el al., Deep-Sea Research, 24,753–773, 1977) we describe a numerical two-dimensional(time and depth) model of phytoplankton growth and nutrientdistribution in the Pacific Ocean off the northwestern U.S.coast. The numerical model consists of coupled integro-partialdifferential equations expressing conservation of chlorophyll, nitrate, and ammonium. The relevant physical and biologicalprocesses are represented by conventional functions and parameters.The system is "closed" by specification of grazing pressureand light intensity. A long-term simulation ova spring and summermonths (for convenience, called the "standard run") representswell the main features of observed chemical data and biologicalvariables, including the formation and deepening of a subsurfacechlorophyll maximum. In this paper, a sensitivity analysis of the system is carriedout by comparing the "standard run" with the results of twentynumerical experiments, in each of which a single function orparameter in the model is modified. The formation of the subsurfacechlorophyll maximum is simulated, more or less realistically,in all experiments. Moreover, the results suggest that the chlorophylldistribution adjusts in time and depth so as to optimize thetransfer of carbon to secondary producers. The level of thecarbon output is determined mainly by the resources availableto the primary producers.