Modeling of Marine Ecosystems: Experience, Modern Approaches, Directions of Development (Review). Part 1: End-to-End Models

Purpose. Despite of a relatively short history of marine systems modeling, which started in late 1960s – early 1970s, this discipline is developing quite intensively. Publications on marine system modeling number in the thousands. The purpose of the article is to review the achievements accumulated in this field. The main attention is paid to the general principles in marine systems modeling, and to the spectrum of the applied modern approaches. The results of analysis of more than 200 sources, i.e. research papers, monographs, sections in books, internet-resources, are summarized in the paper of two parts published separately. Methods and Results. Over the past decades, our understanding of the patterns of marine ecosystems functioning has increased significantly, as well as the possibilities of ecological monitoring and information technologies. At the same time, the increasing number of global and regional environmental programs and projects in the field of rational use of marine resources, protection of marine ecosystems, and assessment of the climate change impacts has resulted in growth of demands for quantitative tools providing the ecosystem-based support of the initiatives in rational management of sea resources. This, in its turn, has required more complex multi-component models and led to significant increase in the number of such models. The first part of this review is focused on the end-to-end models which represent the complex integrative tools assisting in taking correct decisions for rational management of marine resource. Conclusions. Providing testing of scenarios “what, if”, the end-to-end models are the effective modeling instruments for assessing the consequences of climatic and anthropogenic impacts on all the trophic levels of marine ecosystems including bio-geo-chemical cycle, microbial loop, and various kinds of detritus. These models are not intended for taking tactical decisions (in such cases, local object-oriented sub-models should be used), but they are indispensable instruments in strategic planning and complex assessing of the management strategies

Modeling of Marine Ecosystems: Experience, Modern Approaches, Directions of Development (Review). Part 2. Population and Trophodynamic Models

Purpose. The paper presents the second part of the review of the publications devoted to the problems of marine ecosystem modeling. In this part, major attention is paid to modern approaches to the management of marine biological resources which implement the ecosystem principles of modeling and monitoring the spatiotemporal dynamics of water objects. Methods and Results. The review consists of three sections. The first one deals with the models for forecasting dynamics of the exploited populations and for optimizing fishery. The second section considers the trophodynamic models used to study the structure, productivity, and functional role of marine biota interacting with other species and environment at various trophic levels. The trophodynamic models are often applied both for assessing the impact of fishery on marine ecosystems, and for analyzing the influence of the factors directly or indirectly related to climatic variability and anthropogenic activity (eutrophication, salinity, environmental changes). The third section of the review is devoted to a relatively recent direction in marine ecosystem modeling which is based on the geo-information systems. The onrush of the geo-information technologies permitting to connect the data both of the field observations and simulations with their geolocation had an impact on the achievements in the field of ecological modeling. Conclusions. In the coming years, the role of mathematical modeling in study and management of marine ecosystems will grow. The most important areas of research seem to be as follows: perfection of a model description of primary links in the marine ecosystem food webs (NPZD-models); the flows of matter and energy in the marine food chains; eutrophication and oxygen regime in the sea bays; distribution and transformations of pollutants, and their impact on ecosystems; functioning of marine reserves; the means of taking into account climatic factors in the ecosystem models; and application of satellite monitoring data for identifying and verifying the ecosystem individual components (chlorophyll, oil slicks, suspensions)

Multitrophic Interactions in the Sea: Assessing the Effect of Infochemical-Mediated Foraging in a 1-d Spatial Model

The release of chemicals following herbivore grazing on primary producers may provide feeding cues to carnivorous predators, thereby promoting multitrophic interactions. In particular, chemicals released following grazing on phytoplankton by microzooplankton herbivores have been shown to elicit a behavioural foraging response in carnivorous copepods, which may use this chemical information as a mechanism to locate and remain within biologically productive patches of the ocean. In this paper, we use a 1D spatial reaction-diffusion model to simulate a tri-trophic planktonic system in the water column, where predation at the top trophic level (copepods) is affected by infochemicals released by the primary producers forming the bottom trophic level. The effect of the infochemical-mediated predation is investigated by comparing the case where copepods forage randomly to the case where copepods adjust their vertical position to follow the distribution of grazing-induced chemicals. Results indicate that utilization of infochemicals for foraging provides fitness benefits to copepods and stabilizes the system at high nutrient load, whilst also forming a possible mechanism for phytoplankton bloom formation. We also investigate how the copepod efficiency to respond to infochemicals affects the results, and show that small increases (2%) in the ability of copepods to sense infochemicals can promote their persistence in the system. Finally we argue that effectively employing infochemicals for foraging can be an evolutionarily stable strategy for copepods

Spatial Demogenetic Model for Studying Phenomena Observed upon Introduction of the Ragweed Leaf Beetle in the South of Russia

The introduction of the ragweed leaf beetle in the South of Russia in 1978–1989 was accompanied by a number of spectacular phenomena that determined the general success of the ragweed control and further dispersal and acclimatization of the beetles: (i) formation of solitary population waves (SPW), characterized by an extremely high density of the phytophage population at the narrow band of the front of a moving wave defoliating nearly all ragweed plants, and (ii) rapid, within 5-6 generations, development of flight in the leaf beetle species that in its homeland lost the ability to fly. We present here a demogenetic model capable of reproducing both these phenomena, assuming that the flight ability of a phytophage population is governed by a single diallelic locus with flight and flightless alleles that determine three genotypes of the ragweed leaf beetle. Simulation results agree well with the practical recommendation of retaining a high density of common ragweed in the release area in order to provide the necessary conditions for the initial increase of the leaf beetle population and the formation of the wave. The model confirms the earlier hypothesis that the SPW is the key factor that determines efficiency of weed biocontrol program. We demonstrate also that the formation of the wave has crucially accelerated the development of the beetles’ ability to fly