Linking marine ecosystems with the services they supply: what are the relevant service providing units?

Marine ecosystems support supply of ecosystem services (ESs) through processes and functions carried out by diverse biological elements. Managing sustainability of ES use requires linking services to the parts of ecosystems supplying them. We specified marine service providing units (SPUs) as plausible combinations of a biotic group (e.g., bacteria, seabirds) with an associated major habitat (e.g., sublittoral sediment). We developed a network model for large marine ecosystems, documenting 2,916 links between 153 SPUs with 31 services. Coastal habitats and their taxa accounted for 48% of links, but all habitats with their taxa contribute to at least 20 ESs. Through network analysis, we showed some services link to certain key habitats, while others are less clearly defined in space, being supported by a variety of habitats and their taxa. Analysis highlighted large-scale flows across marine habitats that are essential in underpinning continued supply of certain ESs, for example, seed dispersal. If we only protect habitats where services are used, we will not fully protect the supply of services reliant on mobile taxa moving between habitats. This emerged because we considered habitats and their taxa together. We recommend using combinations of habitats and taxa as SPUs when informing marine ecosystem management and conservation.