PHYTOPLANKTON in the SEA of OKHOTSK along WESTERN KAMCHATKA: WARM vs COLD YEARS

Abstract The paper discusses phytoplankton distribution on the West Kamchatka shelf of the Sea of Okhotsk by comparing phytoplankton in spring-summer-autumn seasons of warm 2015 and cold 2016. Mathematical models are used to estimate the phytoplankton abundance in the water column. A model with an adaptation function is proposed. Satellite data on a sea surface are used as initial condition for solving a system of equations in a mathematical model. Satellite measurements contain chlorophyll “a” concentration, temperature and illumination for the surface water layer. Depth illumination is calculated by differential equation. Models tested on the basis of in situ data show an adequate display of the dynamics of integrated biomass depending on external conditions. The integrated use of satellites and information in situ makes it possible to estimate the phytoplankton abundance over a large area. To compare phytoplankton distributions in warm 2015 and cold 2016, a model with an adaptation function is used. The shelf of Western Kamchatka with its warm and cold year alternations shows the dynamics of the species composition vs the year type. Species composition changes to make the phytoplankton community be better adapted to changing environmental conditions.