Are coastal habitats important nurseries? A meta‐analysis

Abstract

Nearshore‐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.

Positive Ecological Interactions and the Success of Seagrass Restoration

“…Seagrasses are present on the coasts of all continents except Antarctica and are among the most productive ecosystems on Earth (Hemminga and Duarte, 2000;Green and Short, 2003). They provide habitat for multiple life stages of many commercially-and recreationally-important fishes, shellfish, and crustaceans, improve water quality, sequester carbon, stabilize sediment, and reduce coastal erosion (Nagelkerken et al, 2000;Jackson et al, 2001;Heck et al, 2003;Orth et al, 2006;Fourqurean et al, 2012;Duarte et al, 2013;James et al, 2019;Lefcheck et al, 2019). However, the total area covered by seagrass is estimated to have declined by 30-60%, including total loss in some places (Evans et al, 2018).…”

Do beds of subtidal estuarine seagrass constitute a refuge for macrobenthic biodiversity threatened intertidally?

“…Amongst other services (Barbier et al 2011;Dewsbury et al 2016), seagrasses (i) stabilise coastal sediments and prevent erosion, (ii) reduce water velocities, (iii) trap nutrients and organic molecules, (iv) shelter and feed juvenile nektonic prawns and fish of commercial importance and the adults of iconic but vulnerable dugong, green turtles and syngnathid fish; and (v) sequester carbon. Indeed, per annum, 1 ha of seagrass can sequester carbon equivalent to that emitted by a car travelling 3350 km, making it a globally significant carbon stock with an average of some 14 kg buried C m -2 , and it can absorb the nutrients released in the treated effluent of 200 people (McKenzie and Yoshida 2013;Adams 2016;Lefcheck et al 2019;Githaiga et al 2019). In spite of these known benefits, however, anthropogenic destruction of seagrass beds continues at a very high rate, i.e.…”

Toward a Coordinated Global Observing System for Seagrasses and Marine Macroalgae

“…Seagrasses support biotic communities that are often considerably more diverse and productive than in surrounding unvegetated sediments as a result of the physical structure of seagrass meadows and the high productivity of associated algae (Orth and Van Montfrans, 1984;Duffy et al, 2013b). Seagrass meadows are especially important as nursery habitats for juvenile life stages of fishes and larger invertebrates (Beck et al, 2001;Heck et al, 2003;Lefcheck et al, 2019) and provide feeding and breeding habitats for several threatened species, including sea turtles and sirenians (dugongs and manatees). However, much seagrass production is ungrazed and flows into detritus food webs or is buried in sediments, making seagrass meadows important sites of blue carbon burial (Fourqurean et al, 2012;Duarte et al, 2013).…”

“…Seagrasses and macroalgae (macrophytes) are the foundation of submerged vegetated ecosystems in shallow coastal waters throughout the world. They are among the most productive habitats on land or sea, provide critical habitat for a diverse range of animals, including commercial, and subsistence fisheries and species of concern (Heck et al, 2003;Hamilton and Konar, 2007;Hughes et al, 2009;Lefcheck et al, 2019), and provide coastal protection, uptake of terrestrial nutrient runoff, and carbon storage. These habitats and the services they provide are threatened by a range of interacting human activities, notably coastal development, declining water quality, invasive species, climate warming, sea level rise, and storms (Carpenter et al, 2008;Waycott et al, 2009;Polidoro et al, 2010;Filbee-Dexter and Wernberg, 2018).…”