Colonization and Predation in Isolated Seagrass Beds: An Experimental Assessment From the Northern Gulf of Mexico

We tested the effects of habitat fragmentation on the structure (community composition and biomass) and function (predation rates as assessed by tethering) of circular artificial seagrass units (ASUs) located in an area removed from the influence of immigrants from established seagrass meadows. ASUs varied by size (0.1-10 m2), perimeter, and perimeter:area ratios (P/A). Blue crabs and hermit crabs accounted for the greatest number of individuals and biomass present on the ASUs, but amphipods, shrimps, fishes, and gastropods were also present. We detected few significant relationships between abundance or biomass and patch size, perimeter, or P/A ratios. In tethering experiments, there were no significant differences in mortality among the different sized ASUs in any of the three tethering locations, but there was significantly less pinfish mortality in the ASU center as compared to the patch edge and unstructured sand habitats. Our results suggest that although community composition may be dissimilar to areas with established seagrass meadows, the ecological responses to habitat fragmentation remain constant. These data can provide a better understanding of faunal assemblages that can be expected for restored seagrass beds in areas without established seagrass populations