INTRODUCTION The growth of population of the Earth and the scientific and technological progress resulted in the escalation of anthropogenic impact on the environment. At present, the anthropogenic load on the biosphere is not only commensurable with natural processes and cycles, but, in many cases, excel them and exceed the self-restoring capabilities and properties of natural ecosystems. This leads to irreversible consequences for natural and anthropogenic systems. The most important component of natural environment is the hydrosphere, more than 97% of it being the World Ocean. In the nearest future, the mankind will have to solve problems related to the exhaustion of reserves of many natural resources of dry land, and, therefore, the significance of the World Ocean as a source of huge reserves of mineral, energy, and biological resources will grow. The expansion of the sphere of human activity in the oceans and seas occurs, first of all, in the shelf regions, which are the most productive area of the World Ocean. The ca- pacity of the biomass of littoral regions of the ocean exceeds the capacity of dry land by more than two orders of magnitude [61]. At present, the most part of biological and min- eral resources of the sea is extracted exactly in the shelf areas. The development of these resources is accompanied by an increase in the anthropogenic impact on marine ecosys- tems, which threatens their existence itself. The anthropogenic impact on the ecosystems of sea shelf areas is not limited by the use of their resources. As a result of industrial and household human activity, a huge amount of various pollutants gets into the littoral areas of the sea with river waters and sewage. Numerous substances that are used or manufactured on dry land as a result of human activity are eventually discharged to the sea and accumulated in its shelf area. The increasing anthropogenic load on the littoral areas of the sea leads to the violation of the existing balance of processes and degradation, and overrange of admissible ecolog- ical niches of shelf ecosystems, which, in turn, leads to stable changes in the structure and functioning of marine biocenoses and, in some cases, to their complete disappearance. In this connection, the problem of control of the quality of littoral sea waters by means of the regulation and optimization of the discharge of pollutants, the realization of various eco- logically oriented waterworks projects, etc., becomes especially urgent. The objective scientifically substantiated prediction of ecological consequences of the impact of existing and planned economic objects on the marine medium and the evalua- tion of the efficiency of various administrative decisions in the field of rational use, pro- tection, and restoration of resources of the sea shelf area are impossible without using ix x Introduction mathematical models, combined under the common name of “water-quality models.” The development and verification of such mathematical models intended for using as a tool of ecological prediction in the course of scenario modeling of natural processes is one of the main aims of ecological monitoring of littoral sea areas. The appropriateness and necessity of the application of mathematical models to the solution of problems related to the development of a strategy for control of the quality of water medium are explained by the fact that such models enable one to take into account, in decision making, the correlation of the components of an ecosystem and the possible “counterintuitiveness” of its behavior under changes in external loads, thus moving eco- logical predictions from the category of intuitive predictions into the category of objective ones. Due to the active development and utilization of resources of the Ukrainian sea shelf, of special importance is the problem of preservation and improvement of quality of ma- rine medium, guaranteeing of ecological safety, and minimization of damage caused by human economic activity to the ecosystems of littoral and shelf areas of the Black and Azov Seas. The solution of these problems requires applied water-quality models that combining such properties as complexity, informativeness, and adequacy to natural ana- logs with the minimization of costs for their adaptation, calibration, and practical realiza- tion. The broad application of these models to the solution of applied problems of sea ecology is impossible without their information support, calibration, and practical use for the development of scientifically substantiated recommendations on the preservation and improvement of quality of water medium and its resources. In the present work, we generalize our experience in the development and use of nu- merical mathematical water-quality models for the solution of applied ecological prob- lems and the determination of optimal strategy of control of water quality in shelf marine ecosystems at tropical and temperate latitudes subject to strong anthropogenic impact. The objects of investigation in this work are shelf marine ecosystems of littoral sea basins of the Colombian coast of the Caribbean Sea and the northwest part of the Black Sea, or, more specifically, the quality of water in these ecosystems. On the basis of data of monitoring, we carry out an ecosystem analysis of the present-day ecological state of tropical sea basins of the Colombian coast of the Caribbean Sea. We obtain new informa- tion on operating hydrochemical characteristics of Odessa region of the northwest part of the Black Sea and their relation to river discharge, hydrological conditions and phenom- ena, and the operation of anthropogenic pollution sources in the littoral area. We also de- scribe the ecological consequences of anthropogenic action on the ecosystems of the in- vestigated marine water areas. On the basis of investigations of specific features of eutrophication of waters in the sea shelf areas at temperate and tropical latitudes, we develop a new nonstationary ap- plied numerical water-quality model and its different modifications. We propose original schemes and methods for the calibration of eutrophication blocks of the water-quality model, which were successfully tested and showed their efficiency in the solution of ap- plied problems for marine water areas and basins belonging to different climatic zones and having different morphological, hydrological, hydrochemical, and hydrobiological characteristics. Introduction xi We develop requirements to the organization and structure of ecological monitoring of marine medium, including specialized experiments motivated by the necessity of infor- mation support of the development, adaptation, calibration, and use of water-quality mod- els for the solution of practical problems of sea ecology. We determine, generalize, and systematize methodological approaches to the determination of parameters of water-qual- ity models on the basis of results of ecological monitoring. We also generalize and sys- tematize the results of different investigations for the the determination of the characteris- tic values of the rates of chemical and biological processes, which are taken into account in water-quality models for marine and fresh-water ecosystems, the ranges of their varia- bility, and dependences on characteristics of water medium. The proposed model is used as a tool for the prediction of ecological consequences and the evaluation of the appropriateness and efficiency of various administrative deci- sions aimed at the preservation and improvement of water quality of the investigated water objects. We develop and improve the methodology of application of numerical mathematical models to the determination of the optimal strategy of control of water quality in shelf marine ecosystems subject to strong anthropogenic load. For the investi- gated marine water areas, using results of numerical simulation experiments with modifi- cations of the model, we determine optimal strategies for the realization of nature-conser- vation measures aimed at the improvement of water quality in these basins. The results that form the basis of this work were obtained within the framework of 11 national and international projects that were carried out at the Odessa Branch of the Insti- tute of Biology of Southern Seas of the Ukrainian National Academy of Sciences, the Centro de Investigaciones Oceanográficas e Hidrográficas (Colombia), and the Odessa State Ecological University. We are grateful for fruitful cooperation to all our colleagues—the coauthors of publi- cations from the Marine Hydrophysical Institute of the Ukrainian National Academy of Sciences, the Odessa Branch of the Institute of Biology of Southern Seas of the Ukrainian National Academy of Sciences, the Odessa State Ecological University, and the Centro de Investigaciones Oceanográficas e Hidrográficas (Colombia). We want to especially ac- knowledge our many-year collaboration with S. A. Lonin, a Candidate of Physical and Mathematical Sciences, who now continues his scientific work in Colombia, and O. Yu. Sapko, an assistant-lecturer of the Department of Ecological Law at the Odessa State Ecological University, whose materials were used in the preparation of Sections 2.2.1 and 7.3. 1. ROLE OF MATHEMATICAL MODELING IN THE SOLUTION OF THE PROBLEMS OF QUALITY CONTROL FOR WATERS OF THE ECOSYSTEMS OF SEA SHELF In what follows, the quality of seawater is regarded as a characteristic of its compo- sition and properties specifying the turnover of substances, bioproductivity, structure and regularities