Seasonal variations of zooplankton biomass vertical distributions in the mesopelagial of the Indian Ocean

Seasonal variations of zooplankton biomass vertical distributions at the depths between 100 and 1000 m in four latitudinal zones - 0-15 degrees N and 0-15, 15-45, 45-65 degrees S in the Indian Ocean was studied. The function lgB = lgB(0) + klg(100/g) was used for description of biomass distribution in this depths interval, where lgB is the decimal logarithm of biomass at the depth z; lgB(0) is the same at z = 100 m; k is the parameter describing the rate of biomass alterations with depth. At all latitudinal zones the amplitude of biomass oscillations declines with depth, this effect is feebly pronounced at the latitudes of 0-15 degrees N. The formulas that determines the dependence of lgB(0) and k on the latitude and time were developed and appropriate graphs are presented. In the northern part of the ocean the biomass in the period of summer SW monsoon is greater than during the period of the winter NE monsoon, and its decrease with depth is more abrupt. Biomass oscillations in the ocean south of 40 degrees S and in the northern regions are in opposite phases.