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This chapter examines recent case studies of marine food webs to evaluate the applicability of food web theories for the marine environment. Classical macrodescriptors and recent network metrics are evaluated for each marine food web example. Food webs are defined as those which are non-estuarine, non-coastal, and larger in scale than food webs typically and classically studied (i.e., not a bay, not a river-ocean mixing zone, not a rocky inter-tidal zone, etc.). There are clear distinctions for marine food webs when compared to all terrestrial and other aquatic food webs, yet there are also clear distinctions among different types of marine food webs. The chapter notes that there are three categories of food web theories: (i) those factors and models which apply categorically to all food webs; (ii) those factors and models which can be split into simple, lowly connected, strongly interacting, clearly defined localized food webs versus complex, highly connected, weakly interacting, broader, more extensive food webs; and (iii) those factors and models which are uniquely and distinctly marine. Understanding the qualitative properties of food webs can provide further evaluation of which theories are appropriate, which are not, when each is true, and why. Finally, the chapter discusses the applications and implications of these theories for ecosystem-based natural resource management.

The advances made by the GLOBEC programme are summarized in terms of what was learned from GLOBEC science, the science themes now emerging from GLOBEC results, and the implications of these for future interdisciplinary marine ecosystem research programmes. The fundamental changes in understanding of scales of interactions of marine ecosystems, alternative views of food webs, and the appreciation of the role of humans in marine ecosystem processes that have come from GLOBEC science are highlighted. Emerging themes related to scales and thresholds, human interactions with ecosystem change, and advances in modelling marine ecosystems provide the basis for future research that builds on the GLOBEC programme. The lessons learned from the GLOBEC programme highlight, and provide direction for, the many challenges that will have to be overcome to develop the integrative research programmes between the natural, social, and economic sciences that are needed to understand and sustain the world's ocean in an era of increasing change and uncertainty.

Ultraviolet B radiation (UVBR, 280–320 nm), the most biologically damaging portion of the solar spectra reaching the Earth’s ground, received considerable scientific attention after the discovery of the spring stratospheric ‘ozone hole’ formation in the late 1970s over Antarctica. Recently, similar low ozone conditions were observed over the Arctic and occasionally at lower latitudes. Furthermore, expected ocean acidification, increased surface water temperatures, and modifications in the structure of the water column due to global change expanded the concerns regarding the potential damage of global change to the structure of marine food webs. This chapter reviews the effects of UVBR on various marine ecosystems. Introduction of the chapter gives a description of factors that influence the UVBR intensities that reach these ecosystems such as latitude, season, stratospheric ozone layer thickness, and penetration within the water column. Then, the chapter depicts the effects of UVBR on the food webs of some important marine ecosystems, such as polar oceans, coastal waters, fronts and upwellings, oceanic gyres, and benthic ecosystems including coral reefs. Finally, this chapter investigates the potential interactions of enhanced UVBR along with other climate change stressors such as global warming and ocean acidification.