I am interested the causes and consequences of patterns of marine biodiversity across diverse taxa from microbes to algae to invertebrates. I’m particularly interested in how multiple dimensions of diversity: genetic or trait-based diversity within species, phylogenetic diversity among species, or simply species richness vary in both their spatial distribution and in their impact on the functioning (productivity, stability) of ecological communities. In this talk I’ll focus on the “hidden” biodiversity within (relatively speaking) homogenous looking beds of seagrass— marine angiosperms that provide structure and primary production in shallow coastal environments worldwide. I’ll consider different dimensions of diversity from genetic variation within seagrasses to the species, trait and phylogenetic diversity of invertebrates, microbes, and other taxa associated with them. I’ll describe local-scale, intensive field and mesocosm experiments, distributed experiments across locations, and global scale surveys to address a range of questions in ecology: Do similar patterns arise in the diversity of diverse taxa across latitudinal (or other) gradients? Are these patterns controlled by similar processes in different groups? What dimensions of diversity (richness vs evenness, phenotypic vs phylogenetic) are most predictive of ecological functioning? Or do different dimensions offer complementary information? Can we use patterns in traits and phylogenies to infer how assembly processes vary at different scales from local to regional to global?