Reassessing the nursery role of seagrass habitats from temperate to tropical regions: a meta-analysis

Identifying and protecting coastal nursery habitats is imperative as human impacts to these areas accelerate. Nursery habitats support higher juvenile (1) density, (2) growth, or (3) survival (hereafter nursery role metrics) than other habitats, resulting in a greater contribution to adult populations. Seagrass habitat is commonly referred to as a nursery, but its contribution to each nursery role metric across geographic regions and in comparison to other nursery habitats (e.g. mangroves, coral reefs, salt marshes) remains unclear. We conducted a global meta-analysis of juvenile fish and macro-invertebrate performance in seagrass relative to other habitats to assess the nursery role metric, geographic region, and taxonomic group for which seagrass is most beneficial. We compiled data from 51 papers, spanning temperate, subtropical, and tropical regions and including unstructured and structured comparative habitats. We found that, overall, seagrass provided better nursery habitat than other habitats, particularly for supporting high juvenile density and growth. Seagrass habitat was generally more beneficial in temperate and subtropical regions than in the tropics, and more important for juvenile invertebrates than for fishes. Seagrass appears to be highly valuable for provision of food, but supplies equivalent or less adequate refuge than other nursery habitats. Management efforts may benefit from prioritizing conservation of seagrass habitats as food sources for juveniles in combination with other structured habitats for refuge in temperate regions; in tropical regions, seagrass may be a less important nursery habitat to target for conservation, though the value of nursery habitats may shift with ongoing climate change.