Are coastal habitats important nurseries? A meta‐analysis

Jonathan S Lefcheck,Brent B Hughes,Michael W Beck,Bruce W Pfirrmann,Robert J Orth,Andrew J Johnson,Douglas B Rasher,Ashley R Smyth,Bethany L Williams

doi:10.1111/conl.12645

Abstract

AbstractNearshore‐structured habitats—including underwater grasses, mangroves, coral, and other biogenic reefs, marshes, and complex abiotic substrates—have long been postulated to function as important nurseries for juvenile fishes and invertebrates. Here, we review the evolution of the “nursery habitat hypothesis” and use >11,000 comparisons from 160 peer‐reviewed studies to test whether and which structured habitats increase juvenile density, growth, and survival. In general, almost all structured habitats significantly enhanced juvenile density—and in some cases growth and survival—relative to unstructured habitats. Underwater grasses and mangroves also promoted juvenile density and growth beyond what was observed in other structured habitats. These conclusions were robust to variation among studies, although there were significant differences with latitude and among some phyla. Our results confirm the basic nursery function of certain structured habitats, which lends further support to their conservation, restoration, and management at a time when our coastal environments are becoming increasingly impacted. They also reveal a dearth of evidence from many other systems (e.g., kelp forests) and for responses other than density. Although recent studies have advocated for increasingly complex approaches to evaluating nurseries, we recommend a renewed emphasis on more straightforward assessments of juvenile growth, survival, reproduction, and recruitment.

Highlights

A defining feature of all shallow waters of coastal and estuarine regions throughout the world is the presence of one or more structured habitats. These habitats range from foundational autotrophs to coral reefs and other animal-derived structures to abiotic substrates
Studies overwhelmingly reported on juvenile density, a smaller number reported on growth and survival (Figure 1B)
In our meta-analysis of 160 published articles, we found substantial evidence for the role of structured habitats in enhancing the density, growth, and survival of juvenile fishes and invertebrates

Summary

Introduction

A defining feature of all shallow waters of coastal and estuarine regions throughout the world is the presence of one or more structured habitats These habitats range from foundational autotrophs (seagrasses, mangroves, marshes, other submersed vegetation—including tidal freshwater plants— and macroalgae/kelps) to coral reefs and other animal-derived structures (oysters, mussels, sponges) to abiotic substrates (rock crevices, shell hash, cobble). They are considered “structured” because they have complex three-dimensional shapes that protrude above the benthos compared to unstructured habitats, such as sand and mud, which provide only a relatively flat, two-dimensional surface. Perhaps the most cited function of all is as a nursery in which juveniles of numerous species of vertebrates and invertebrates can grow and mature before migrating elsewhere as adults

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