Marine foundation species such as seagrasses structure coastal ecosystems not only through their physical architecture but through the metabolic activities of their associated microbiomes. The holobiont framework predicts that intimate multi-species associations may give rise to emergent properties: collective functions that exceed the sum of individual contributions and cannot be predicted from the partners in isolation. Seagrass meadows are particularly relevant in this context, as they harbor diverse assemblages of invertebrates — including sponges, bivalves, and other benthic fauna — each carrying their own microbiomes and potentially contributing to ecosystem-scale biogeochemical cycling.
Here, I present evidence for emergent biogeochemical function in seagrass-associated multi-species systems in the Mediterranean Sea. Using stable isotope tracer incubations, nutrient flux measurements, and metagenomic profiling, my group characterized key elemental cycling processes — including nitrogen and sulfur transformations — across the individual partners and their associations. In these systems, the association expresses a suite of biogeochemical functions that cannot be predicted from the partners in isolation, and that have measurable consequences for nutrient availability and primary productivity at the holobiont scale. Metagenomic data provide independent genomic support for the functional breadth of these associations.
Collectively, these results suggest that seagrass meadows should be understood not merely as monospecific holobionts but as multi-partner biogeochemical units, where emergent functions arising from species co-occurrence contribute to nutrient retention and ecosystem resilience. These findings have implications for how we model elemental cycling in coastal ecosystems and for conservation strategies targeting seagrass meadow integrity under increasing environmental pressure.