Abstract
Coastal ecosystems are vulnerable to anthropogenic disturbances which can cause loss of benthic macrofauna and their ecosystem functioning. Despite the importance of functional assessments for conservation and management, knowledge gaps persist on the generality of how the diversity and functional traits of benthic communities influence ecosystem functioning. We investigated eight sites in three different habitats across ~1,260 km of coastline, to evaluate patterns between taxonomic and functional diversity of benthic macrofauna, and the relationship between benthic macrofauna, functional traits and environmental conditions. A total of 74 benthic macrofauna taxa were identified. Significant differences across sites and season were found for metrics based on taxonomic and functional traits. Multivariate analysis revealed spatial-temporal differences, which were more evident based on taxa than functional traits. Functional diversity also showed spatial and temporal differences and was positively correlated with the number of taxa. The dominant functional traits modalities were deposit feeders, with large (>20 mm) body size, burrowers, bioirrigators, deeper than 3 cm in sediments, and irregular morphology. Novel Generalized Linear Latent Variable Models (GLLVM) uncovered several site-dependent relationships between taxa, traits and environmental conditions. Functional redundancy was lowest in a highly modified lagoon, and highest in a more pristine embayment. The outcomes from this study showed site-dependent patterns of benthic communities based on either taxonomic or functional metrics, highlighting that both perspectives are complementary to obtain a holistic understanding of the functioning in marine sediments under environmental change.
Highlights
Benthic macrofauna are major providers of ecosystem functioning in marine habitats
This study identified spatial and temporal patterns of benthic communities, based on both taxonomic and functional metrics
Functional diversity and expression of functional traits were site-dependent and different across habitats, which could be explained by the benthic community at each site, the influence of environmental conditions and habitat complexity
Summary
Benthic macrofauna are major providers of ecosystem functioning in marine habitats. They modify soft-sediment habitats through biological processes such as ingestion, digestion, excretion, and bioturbation, which facilitates microbial recycling of nutrients, detoxification of pollutants, and organic matter remineralization (Snelgrove et al, 2014; Shojaei et al, 2015; Caswell et al, 2018; Wyness et al, 2021). Descriptive and experimental approaches have highlighted that benthic communities are structured by environmental factors (e.g., temperature, water depth, salinity, sediment type, habitat complexity), biological processes (e.g., competition, predation, bioturbation), and ecosystem engineering by benthic macrofauna (e.g., Reise, 1985; Honkoop et al, 2006; Meadows et al, 2012) These traditional taxonomic-based studies laid the base for functional assessments of benthic fauna (Snelgrove, 1997; Thrush et al, 2006; Snelgrove et al, 2014), which allow the understanding of how changes in benthic biodiversity influence the functioning of an ecosystem. The use of functional approaches is a powerful tool to investigate Biodiversity and Ecosystem Functioning relationships (BEF), and how these relationships vary spatially and temporally, or under specific environmental conditions (Baldrighi et al, 2017; Beauchard et al, 2017)
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