Geographical Faculty, M.V.Lomonosov Moscow University, Vorob'evy Gory, Moscow 119899, Russia

* Computation Centre, Russian Academy of Science, Vavilova ul. 42, Moscow 117966, Russia

Abstract

The mathematical model is proposed to study the seasonal fluctuation of phyto- and zooplankton biomass in the ocean at different latitudes. It is assumed that relation between particular trophic levels are of "predator - prey" type. The analysis of the results shows that in temperate and high latitudes biomass dynamic is characterized by clearly distinct pick in spring and early summer, moderate second pick and stationary state in winter when there is no predation. The fluctuations of biomass are not very large in tropics, while closer to the equator they become more harmonical. The model under study can be considered as a part of the model of global nitrogen and phosphorus cycles in the ocean. The changes of phyto- and zooplankton biomass as well as in N and P concentration are presented as three-dimensional pictures. The model shows that the decrease in total N and P results in the generation of 2, 3 and 4-years cycles in temperate and high latitudes.