The major principles, current methods, and approaches to solving optimization problems in assessing parameters for simulation models of aquatic ecosystems and their sensitivity to changes in the values of model parameters are considered. Analysis of the practical application of different methods to model calibration shows that no method of global optimization for complex hydrological models and models of aquatic ecosystems can guarantee obtaining a unique and best solution. Some results are shown, which have been obtained in solving the problem of the choice of parameters for the biohydrochemical block of a simulation model of Neva Bay (NB), the Gulf of Finland. The process of solving the optimization problem is formalized in the form of a two-stage direct-search algorithm: a random search algorithm (global search in the entire parameter space), followed by a local search by a modified Nelder-Mead simplex method.

Методами статистического моделирования (ГИС «Сахалинский шельф») восстановлен годовой ход температуры и солености воды на стандартных горизонтах на сети океанографических станций юго-восточного шельфа Сахалина (общая продолжительность наблюдений ~40 лет). Методами численного моделирования с помощью океанической модели Бергенского университета выполнено пространственное восстановление полей температуры и солености воды на стандартных горизонтах в узлах регулярной сетки. В результате анализа расчетных данных выявлены новые черты гидрологического режима и впервые получены максимально детализированные термохалинные характеристики полного годового цикла, по которым рассчитана среднемесячная трехмерная циркуляция вод, включая ледовый период.

The data collected for model calculations is systematized for natural and design conditions. The natural conditions did not take into account the effect of the complex of water-protection structures on the hydrological regime of Neva Bay and on the biogenic load onto this water area, while the design conditions, conversely, reflected the possible impact of those structures on the hydrology and ecology of the area. Numerical experiments were used to study the processes of transformation of N and P compounds and the dynamics of dissolved O₂ in Neva Bay water area. In the comparison of the calculated and observed concentrations of biogenic substances, Theil criterion was evaluated to assess the adequacy of the model in reproducing the concentration fields of the distribution of biogenic substances over Neva Bay water area. The major qualitative and quantitative features of the formation of the spatial heterogeneity and the time variations in the concentrations of biogenic element compounds over Neva Bay water area are identified. Possible improvements of the model in the reproduction of the complex of processes that are of particular importance for the development of substance transformations in shallow ecosystems are considered.

A spatially heterogeneous simulation model of the Neva Bay ecosystem (the Gulf of Finland) is considered; its major blocks and the numerical methods used are characterized. Formulations are given for the major concepts used in the development of the biohydrochemical block of the mathematical model for adequate description of the processes of joint transformation of forms of N and P—key biogenic elements for Neva Bay, and the variation regime of dissolved O₂ in water environment. Model formalization of the key regulatory mechanisms that ensure the structural and functional stability of the ecosystem is presented. The development of the model of an open aquatic system was focused on the joint simulation of the dynamics of biological system components and its functioning environment basing on the synthesis of hydrobiological, hydrochemical, and hydrophysical knowledge on Neva Bay ecosystem.

The available observational data on variations of oil hydrocarbon concentrations in White Sea tributaries and in individual parts of the sea are analyzed, and the contributions of different external sources to marine environment pollution are evaluated. The results of calculations are used to determine the possible total input of hydrocarbons from additional potential sources—internal natural (production by microorganisms) and external anthropogenic (navigation and sea shipping), which are most active in the summer and autumn. The hydroecological CNPSi-model is used to reproduce the processes of pollution of nine areas in the White Sea by oil hydrocarbons and their subsequent biodegradation in the marine environment. The annual dynamics of hydrocarbon concentrations was calculated using the long-term annual observations of monthly variations of the temperature, light intensity, and transparency of water, data on the morphometry of sea areas (the squares, mean depths, and water volumes) and water exchange between the chosen areas, calculated by a hydrodynamic model. For large bays (Dvina, Kandalaksha), the calculated concentrations of oil hydrocarbons are shown to be in agreement with the available estimates (the mean and maximal concentrations). The annual variations of oil hydrocarbon concentrations; the biomasses, oxidation activity and bioproduction characteristics of oil hydrocarbon-oxidizing bacteria are characterized. The calculated internal fluxes of oil hydrocarbons (the inputs from different sources, horizontal transport, and biotransformation) were used to calculate their annual balances for individual areas and the sea as a whole, showing the balanced character of their fluxes with the total balance discrepancies for individual areas varying within 0.3–4.1%.