Virginia Institute of Marine Science
MARINE ECOLOGY PROGRESS SERIES
Exotic species often reduce the abundance or diversity of species in marine ecosystems, but some exotics may benefit native species, such as when habitat is enhanced. In Chesapeake Bay, the exotic macroalga Gracilaria vermiculophylla (Rhodophyta) has flourished and dispersed widely, yet the consequences for native species diversity and abundance are not well known. We experimentally examined the capacity of the structurally complex G. vermiculophylla to provide nursery habitat for the blue crab Callinectes sapidus in Chesapeake Bay, where native eelgrass nursery habitat has dwindled. We also examined ontogenetic shifts in survival across alternative nursery habitats. In field surveys, juvenile density was similar in macroalgae and eelgrass, but lower in unvegetated mud habitat. In field experiments, juvenile survival was positively related to crab size in mud but negatively in eelgrass, confirming the paradigm of a predation-induced ontogenetic shift from seagrass to unvegetated habitat. In contrast, irrespective of crab size, survival was higher in macroalgae than in either native habitat. Thus, exotic habitat-forming macroalgae can compensate for severe declines in seagrass nurseries, and facilitate the emergence of a novel ecosystem.
Exotic species; Ontogenetic habitat shift; Predation; Prey size refuge; Novel ecosystem; Emerging ecosystem; Macroalgae; Seagrass
Johnston, Cora Ann and Lipcius, Rom, Exotic macroalga Gracilaria vermiculophylla provides superior nursery habitat for native blue crab in Chesapeake Bay (2012). MARINE ECOLOGY PROGRESS SERIES, 467, 137-146.