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Concern that the rapid anthropogenic erosion of biodiversity may undermine the delivery of ecosystem services has prompted a synthesis of community and ecosystem ecology over the last decade. Biodiversity-ecosystem functioning (BEF) research is central to this emerging synthesis, asking how biodiversity is related to the magnitude and stability of ecosystem processes. Isolating species richness effects from species composition has been a chief goal of BEF research. This BEF perspective recognized that fluctuating abundances of component species may not produce instability at the community or ecosystem level because compensatory reactions among species dampen fluctuations of aggregate abundance. Within the BEF framework, experiments and theory explicitly relating to the effect of species richness on community-level aggregate properties (mainly biomass) have focused on variability through time in relation to background environmental variation (temporal stability) as well as on the impact (resistance) and recovery (resilience) of such properties to discrete, and often extreme, perturbations. This chapter reviews recent empirical studies examining the links between species richness and these three facets of stability.

This chapter examines the significance of marine biodiversity in relation to marine ecosystem functioning. It proposes a biodiversity-ecosystem function (BEF) framework for marine systems and how it relates to current understanding of marine biodiversity and marine ecosystem functioning. It then discusses three possibilities for marine biodiversity and its relationship to marine ecosystem functioning: the complete extinction of all marine species, the extinction of most marine species such that further loss accelerates change in ecosystem functioning, and restoration of marine biodiversity to its pre-industrial levels. It also considers two other features to make this three-point framework useful: an upper and lower boundary known as the Promethean trajectory and the Arcadian trajectory, respectively. Finally, it looks at the decline of marine biota and its consequences.

This chapter discusses biodiversity-ecosystem function studies in aquatic ecosystems in which additional biotic or abiotic drivers have been taken into account as mediators of ecosystem responses. It examines the impact of species richness relative to abiotic or biotic drivers of change or other biodiversity measures, including species composition and species evenness. It assesses the influence of model systems and ecosystem type of the experimental study on the strength of the relationship between species richness and ecosystem properties, as well as other drivers of change and ecosystem properties. Finally, it illustrates how ecosystem properties are mediated across aquatic ecosystems by analysing the effects of abiotic, biodiversity, and other biotic drivers of change combined.

This chapter describes some approaches for understanding biodiversity-ecosystem function at larger spatial and at longer temporal scales. It first considers the importance of building a credible evidence base of biodiversity change effects on ecosystem functioning at seascape scales. It then explores the different aspects of biodiversity change, compositional and species richness, within contrasting bottom-up controlled and top-down controlled systems, namely, estuaries and coral reefs. The two systems are affected by eutrophication and overfishing.

This chapter examines how observational studies can help in the design, execution, and interpretation of biodiversity-ecosystem function relationships. It first analyses the heterogeneous nature of seafloor landscapes and how interactions between processes occurring on different temporal and spatial scales give rise to complex and interesting dynamics that characterise many benthic marine ecosystems. It then explores the role of observations in studying ecosystem functioning, assesses the relevance of scaling laws to BEF, and considers a more integrative approach to empirical research in BEF studies.

This chapter looks at the links between biodiversity and ecosystem function in soft sediments to help understand the implications of biodiversity loss on ecosystem services. The chapter contains a focus on the challenges in developing real-world tests of biodiversity–ecosystem function (BEF) relationships. The various forms of BEF relationships, their implications and the different elements of biodiversity that link to function are described. Given the multiple functions that occur in soft-sediment ecosystems, this has important implications for the assessment and implications of BEF relationships and functional performance in the up-scaling of BEF relationships. The role of BEF in underpinning many ecosystem services and the interconnections in biodiversity and ecosystem service relationships close out the chapter.

This chapter examines the impact of global change stressors on biodiversity — with an emphasis on the number, composition, and trait distribution of species in communities — and the functioning of multitrophic ocean and estuarine ecosystems. More specifically, it considers how ecological and biogeochemical processes, particularly benthic and pelagic marine ecosystems, are influenced by changes in composition and diversity in multilevel food webs. It first outlines how diversity is changing in oceans and estuaries and how such changes might affect ecosystem functioning. It then discusses experimental and observational studies on biodiversity-ecosystem function (BEF) in multitrophic systems, reviews several methodological and philosophical issues involved in transferring BEF academic research to applied conservation problems, and the link between biodiversity and ecosystem functioning in the Anthropocene.

This chapter examines a biodiversity-ecosystem function experiment, which includes the manipulation of algal richness and abundance in factorial combinations, using mixed-effect models. It also analyses the magnitude of richness effects relative to the strength of density-dependent processes. It illustrates the procedure of partitioning species abundance (density-dependent) and species richness effects using data from a biodiversity experiment performed on the rocky shores south of Livorno in Italy. It also discusses treatment effects on Simpson diversity.

This chapter examines the nature of biodiversity-ecosystem function (BEF) research undertaken to date in marine systems and compares it with that done in terrestrial systems. It discusses gaps in current knowledge and considers the relative merits of different approaches to overcoming limitations of BEF studies. It also explores important ecological processes or patterns that may be lost in abstracting BEF experimental systems from natural ecosystems, asks whether the reduced temporal/spatial scale or compromised ecological realism of marine BEF studies affects the ability to extrapolate results to other systems, and offers some suggestions for future research.

Hundreds of plant and animal species co-exist in marine ecosystems. More than 150 years ago, Charles Darwin recognised explicitly the importance of species interactions by invoking the concept of a ‘tangled bank’ of species. These interactions play an important role in the maintenance of ecological stability in the face of natural and anthropogenic disturbances. However, the mechanisms underlying ecosystem stability in the face of environmental change remain poorly understood. This chapter examines the importance of body size, abundance, and food-web structure for ecosystem functioning. It considers the building blocks of food webs, body mass, species abundance, and predator-prey interactions, as well as the interrelationships between body mass and trophic position. It presents examples that are not restricted to marine ecosystems in order to understand the drivers and consequences of biodiversity change in a wide range of ecosystems. It also discusses the relevance of body mass to biodiversity-ecosystem function research.

The relationships between marine biodiversity and ecosystem functioning raise the possibility that the loss of biodiversity will have serious consequences for humans, who obtain a variety of important goods and services from marine systems. To avert this scenario, it is necessary to sustain ecosystems that are resilient to change while continuing to provide important services. This chapter explores the emergence of the ecosystem approach to environmental management, with an emphasis on the concept of ecosystem services. It emphasises the importance of biodiversity-ecosystem function research in implementing an ecosystem approach to marine management and considers the link between ecology and economics in relation to ecosystem services and biodiversity. It also suggests a general framework that integrates ecological and socio-economic knowledge and approaches to ensure sustainable biodiversity and human well-being in the future. The chapter concludes by looking at future challenges involved in the implementation of an ecosystem approach.

Biodiversity is a measure of variety of life forms, and can be assessed at the genetic, species, and landscape levels. Species diversity can be partitioned into its basic components of richness (number of species) and evenness, and into spatial components (alpha, beta, gamma). Local extinction rates are often higher in situations where evenness is low due to low abundances in rare species. Many experimental and observational studies have been done on how ecosystem process rates will be impacted by reductions in biodiversity. The mechanism behind observed positive relationships between diversity and ecosystem process rates can be due to at least four processes: 1) the species sampling effect, 2) the selection effect, 3) complementary resource use, or 4) pest outbreaks in low-diversity plots. Biodiversity is sometimes positively related to biomass stability and resistance to extreme events. The stability of dominant species can also be important in grasslands.