MEPS 306:233-246 (2006)  -  doi:10.3354/meps306233

Effects of habitat fragmentation per se on decapods and fishes inhabiting seagrass meadows in the northern Gulf of Mexico

Matthew W. Johnson1,2,*, Kenneth L. Heck Jr.1,2

1Dauphin Island Sea Laboratory, 101 Bienville Boulevard, Dauphin Island, Alabama 36528, USA
2Department of Marine Sciences, University of South Alabama, Mobile, Alabama 36688, USA

ABSTRACT: The role of habitat fragmentation per se on ecological processes is incompletely understood in marine environments. Previous work in fragmented habitats has concentrated on growth of bivalve species, faunal abundances and predation of tethered crabs. Unlike other studies, in the present study we measured abundances of decapods and fishes and estimated secondary production from in situ sampling of multiple sized, naturally occurring seagrass beds and artificial seagrass units (ASUs). In 2 locations (Thalassia testudinum meadows in Big Lagoon, Florida, and Halodule wrightii meadows in Grand Bay, Alabama), we sampled 7 to 10 seagrass patches ranging in size from <1 to >100 m2 at 2 mo intervals between June and October 2001. We also sampled 10 replicate ASUs of 2 shapes (stellate and circular) and 2 sizes (0.2036 and 0.0487 m2) that were colonized for 4 wk at both locations in June, August and October. Our results indicated that patch size, patch shape, intra-patch location, and degree of isolation can each influence macrofaunal community structure and secondary production estimates; however, their overall impact was inconsistent. Our data suggest that the effects of habitat fragmentation are location-, time- and species-specific, and that fragmentation at this scale may have little impact on faunal assemblages of seagrass meadows.


KEY WORDS: Halodule wrightii · Artificial seagrass units · Secondary production · Thalassia testudinum · Abundance


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