Marine ecosystems are experiencing rapid and pervasive loss of species.Understanding the consequences of species loss is critical to effectively managing these systems. Over the last several years, numerous experimental manipulations of 25 species richness have been performed, yet existing quantitative syntheses have focused on a just a subset of processes measured in experiments and, as such, have not summarized the full data available from marine systems. Here, we present the results of a meta-analysis of 174 marine experiments from 42 studies that have manipulated the species richness of organisms across a range of taxa and trophic 30 levels and analysed the consequences for various ecosystem processes (categorised as production, consumption or biogeochemical fluxes).Our results show that, generally, mixtures of species tend to enhance levels of ecosystem function relative to the average component species in monoculture, but have no or negative effect on functioning relative to the 'highest-performing' species. 35These results are largely consistent with those from other syntheses, and extend conclusions to ecological functions that are most commonly measured in the marine realm (e.g. nutrient release from sediment bioturbation). For experiments that manipulated three or more levels of richness, we attempted to discern the functional form of the BEF relationship. We found that, for response variables categorised as 40 consumption, a power-function best described the relationship, which is also consistent with previous findings. However, we identified a linear relationship between richness and production. Combined, our results suggest that losses of species will, on average, tend to alter the functioning of marine ecosystems. We outline several research frontiers that will allow us to more fully understand how, why, and 45 when diversity may drive the functioning of marine ecosystems.

The use of functional traits to explain biodiversity effects on ecosystem functioning has attracted intense recent interest, yet very few a priori manipulations of functional diversity have been attempted to date, especially from a food web perspective. Here, we simultaneously manipulated multiple functional traits of estuarine grazers and predators within multiple levels of species richness to test whether species richness or functional diversity is a better predictor of ecosystem functioning in multitrophic estuarine food webs. Community functional diversity better predicted the majority of ecosystem responses based on results from generalized linear mixed effects models. Structural equation modeling revealed that this outcome was independently attributable to functional diversity of both trophic levels, with stronger effects observed for predators. Functional complementarity was also important, as species with different combinations of traits influenced different ecosystem functions. Our study is the first to extend experimental investigations of functional diversity to a multilevel food web, and demonstrates that functional diversity is more effective than species richness in predicting ecosystem functioning in a food web context.

16The use of functional traits to explain how biodiversity affects ecosystem functioning has

Marine ecosystems are experiencing rapid and pervasive loss of species.Understanding the consequences of species loss is critical to effectively managing these systems. Over the last several years, numerous experimental manipulations of 25 species richness have been performed, yet existing quantitative syntheses have focused on a just a subset of processes measured in experiments and, as such, have not summarized the full data available from marine systems. Here, we present the results of a meta-analysis of 174 marine experiments from 42 studies that have manipulated the species richness of organisms across a range of taxa and trophic 30 levels and analysed the consequences for various ecosystem processes (categorised as production, consumption or biogeochemical fluxes).Our results show that, generally, mixtures of species tend to enhance levels of ecosystem function relative to the average component species in monoculture, but have no or negative effect on functioning relative to the 'highest-performing' species. 35These results are largely consistent with those from other syntheses, and extend conclusions to ecological functions that are most commonly measured in the marine realm (e.g. nutrient release from sediment bioturbation). For experiments that manipulated three or more levels of richness, we attempted to discern the functional form of the BEF relationship. We found that, for response variables categorised as 40 consumption, a power-function best described the relationship, which is also consistent with previous findings. However, we identified a linear relationship between richness and production. Combined, our results suggest that losses of species will, on average, tend to alter the functioning of marine ecosystems. We outline several research frontiers that will allow us to more fully understand how, why, and 45 when diversity may drive the functioning of marine ecosystems.

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