Coastwide
Mangrove habitat: Mangroves, like these shown at low tide, provide important nursery habitat for juveniles of many marine species. Photo by D. Malmquist/VIMS

Study confirms and ranks nursery value of coastal habitats

A comprehensive analysis of more than 11,000 previous coastal-habitat measurements suggests that mangroves and seagrasses provide the greatest value as “nurseries” for young fishes and invertebrates, providing key guidance for managers of threatened marine resources.

Findings will help resource managers with difficult conservation decisions

Published last week in Conservation Letters, the analysis began as a class project at William & Mary’s Virginia Institute of Marine Science.

Jonathan Lefcheck conducts fieldwork in the seagrass meadows of Virginia's Eastern Shore during his time as a graduate student at the Virginia Institute of Marine Science. (Photo by P. Richardson/VIMS)
Jonathan Lefcheck conducts fieldwork in the seagrass meadows of Virginia's Eastern Shore during his time as a graduate student at the Virginia Institute of Marine Science. (Photo by P. Richardson/VIMS)

Lead author Jonathan Lefcheck, now the coordinating scientist for the Smithsonian’s Tennenbaum Marine Observatories Network, says, “Our results confirm the nursery function of a range of structured habitats, which supports their conservation, restoration, and management at a time when our coastal environments are increasingly impacted by human activities.”

In addition to mangroves and seagrasses, “structured” marine habitats include marshes, coral and oyster reefs and patches of rock or rubble. Scientists have long considered these habitats better nursery grounds than flat stretches of seafloor sand or mud because of their many elevated nooks and crannies; the team’s analysis was designed to test this idea and determine the relative value of different structured habitats for juveniles of marine species.

“Given how often the word 'nursery’ is used to justify marine conservation and management, we thought it was critical to see what the huge body of evidence out there had to say,” says Lefcheck. “The good news is we found that most structured habitats often translate to greater abundance, growth, and survival of juvenile fishes, crabs, and shrimps. That means more fish for fisheries and stronger coastal economies, and more protection for endangered species.”

In an increasingly common approach called a meta-analysis, the team began by searching the published scientific literature using a long string of terms including “nursery” or “habitat complexity” and “marine” or “estuary.” They used additional criteria to winnow their search results to a core group of 160 studies that had compared the performance of juvenile organisms in structured and unstructured habitats. These studies, conducted worldwide between 1986 and 2016, included 11,236 statistical comparisons of juvenile success. The team then analyzed these comparisons for both general conclusions and specific nuances.

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