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This chapter focuses on the distinction between ecosystem function and ecosystem dynamics. Ecosystem function refers to the manner in which the ecosystem of interest works, and interactions among its component parts and fluxes, including biotic and abiotic compartments. Meanwhile, ecosystem dynamics refers to variation in ecosystem function through time in response to perturbations that are continuous or stochastic in nature, or in relation to changes in ecosystem components. Therefore, the study of ecosystem dynamics derives from an understanding of ecosystem function, and this, in turn, depends critically on successful identification of the important drivers within the ecosystem. Inevitably, a discussion of ecosystem function and dynamics boils down to the factors that influence and contribute to variation in net ecosystem production—the result of net primary productivity and ecosystem respiration.

Available evidence of recent climate‐induced physical and chemical changes in the oceans is summarized, including changes in sea temperatures, nutrient supply, mixing and circulation, trace element supply, acidification, and sea‐level rise. The biological responses in the marine environment to these documented physical changes are then presented by trophic level. Our ability to project ecosystem responses to likely future global change is discussed, including numerous examples of existing projections for several regions of the world's oceans. This chapter concludes with a discussion of a vision of the next steps that are needed to develop better models capable of improving our projections of ecosystem responses to global change.

This chapter examines some of the potential empirical signatures of instability in complex adaptive food webs. It first considers the role of adaptive behavior on food web topology, ecosystem size, and interaction strength before discussing the implications of this behavior for ecosystem dynamics and stability. It then analyzes the results of empirical investigations of Canadian Shield lake trout food webs and how human influences and ecosystems coupled in space may drive biomass pyramids, potentially leading to species loss. It also explores the tendency of subsidies, through human impacts, to homogenize natural ecosytems and concludes by assessing some of the changing conditions that are being driven by humans and how these may change ecosystems.

The Eastern Bering Sea (EBS), the Gulf of Alaska (GOA), and the Barents Sea (BS) share key features: they are dominated by gadoids populations, they are heavily fished, and they are under the influence of large-scale climatic fluctuations. Previous studies have shown that climate forcing can impact the species composition and the food webs in each of these ecosystems. However, food webs and species interactions can mediate the relative impact of climatic perturbation on community. For example, a relatively small increase in SST over the western GOA region during the mid-1970s led to a spectacular change in the local species community, but a reverse in climatic conditions that occurred during the late 1980s did not result in similar biological changes. This chapter reviews the food webs of the GOA, EBS, and BS, and relates them to prevailing large-scale climatic phases. The comparative approach adopted in this review is aimed at increasing the understanding of the mechanisms linking climate change and food web dynamics in marine ecosystems.

Recent advances in the theory of complexity have engendered a shift away from ‘physicalism’, where all nature is reducible to fundamental physical laws towards ‘naturalism’, where natural phenomena are considered within a circumscribed domain of time and space. The study of ecological networks has led the way in this shift, because it can be demonstrated that ecological dynamics are incompatible with the fundamental assumptions that have supported science since Newton. The direction in which causality operates in ecosystems proves more likely to come from the larger configurations of processes (networks) towards their more ephemeral and complicated constituents and their attendant mechanisms. This focus on the macroscopic makes possible a self-consistent description of ecosystem dynamics based solely on the attributes of the network of processes.

This concluding chapter argues that Earth's climate is warming at a pace that may very well be unprecedented, and it is doing so from a higher baseline average temperature than that which was the starting point for the most recent episode of rapid warming, which signaled the end of the Pleistocene and the demise of most of its large mammals. That most recent warming episode also coincided with geographically widespread biome shifts. Perhaps more tellingly, current warming, still in its early stages, has already heralded similarly geographically widespread and taxonomically broad shifts in phenological dynamics, population dynamics, species distributions, and ecosystem carbon dynamics. Indeed, some have asserted that Earth may be on the threshold of the sixth major extinction event.

This chapter assesses the consequences of individual nutrition for populations and the assemblages of species that comprise ecological communities. However, the ecological consequences of nutrition are not restricted to the effects of diet on individual organisms but include as well the direct and indirect interactions occurring among individuals within populations and between species. Understanding the complex network of interactions that produce food webs and structure ecosystem dynamics requires the understanding of the participants' differing nutritional requirements, priorities, and regulatory capacities. Geometric Framework analyses have shown that these features differ between species and across trophic levels. Nutritional space is one part of the fundamental niche of an organism, and there is a need to integrate nutrition with the biophysical ecology of organisms. Evolutionary processes also need to be taken into account, and agent-based models offer promise toward development of a new understanding of the evolutionary ecology of nutrition.

This chapter reviews how marine ecosystems respond to parasites. Evidence from several marine ecosystems shows that parasites can wield control over ecosystem structure, function, and dynamics by regulating host density and phenotype. Like predators, parasites can generate or modify trophic cascades, regulate important foundational species and ecosystem engineers, and mediate species coexistence by affecting competitive outcomes. Sometimes the parasites have clear positive impacts within ecosystems, such as increasing species diversity or maintaining ecosystem stability. Other times, parasites may have destabilizing effects that signal an ecosystem out of balance. But it is now clear that some (but not all) parasites can have strong and, at times, predictable effects, and should thus be incorporated into food web and ecosystem models

Porcupine Cave has produced an astounding number of fossils. More than 20,000 identified specimens of fossil vertebrates were distributed over more than 200,000 years, spanning at least two glacial–interglacial transitions as well as smaller-scale climatic fluctuations within glacials and interglacials. This book discusses the role paleontology plays in understanding ecosystem dynamics, such as the maintenance of biodiversity, the effects of climate change on biodiversity, and how biodiversity relates to the health of ecosystems. The faunal dynamics that characterize Porcupine Cave climatic transitions typify how ecosystems respond to climatic warming episodes. The book suggests that faunal responses to climate change may be useful as an ecological baseline against which future changes can be measured.

This book explores the ecosystem dynamics of the Klamath Mountains, with their complex geologic history and diverse flora and fauna. It describes the natural disturbances and human activities that have affected the ecosystems of the Klamaths in various ways. The chapter also emphasizes the principles of sustainable management to effectively steward the land.

Among the large cetaceans, gray whales (Eschrichtius robustus) are unique in three important ways: They are benthic feeders; they undertake one of the longest migrations of any mammal; and they may be fully recovered from overharvesting by commercial whaling. The eastern gray whales migrate annually between the mating regions and calving lagoons on the west coast of Baja California, Mexico, to summer feeding grounds in the northern Bering Sea and the Chukchi Sea. This chapter explores the arctic ecosystem dynamics that justify such a migration and the impacts of the whales upon the system. It concludes with an oceanographic production model that both explains the current location of major gray whale feeding sites and can be used for predictive purposes.