ASSESSMENT OF MANGROVE AND SALT MARSH MESOCOSM FUNCTIONAL VALUE USING PERIWINKLE SNAILS, LITTORARIA ANGULIFERA AND LITTORARIA IRRORATA, AS AN INDICATOR

摘要

Although much research has been conducted on restoration techniques, questions about the functional value of restored and constructed ecosystems remain. Gastropods are a particularly useful indicator organism because they play a vital role at the detrital interface. The first phase of this study addresses the question of whether the age structure, population density, and distribution of the mangrove tree periwinkle snail, Littoraria angulifera, in the Smithsonian Institution's Florida Everglades mesocosm in Washington, DC is analogous to that of wild specimens. Research was conducted at from 1997 to 2000 and reference site data was collected in 1999. The population fell to zero, with no reproduction leading to recruitment of juveniles. Reference site populations were found at significantly higher densities and greater average heights than the mesocosm population. The second phase investigates the same factors, as well as survival, in populations of the salt marsh periwinkle, Littoraria irrorata at a reference site on Slaughter Creek near Smithville, Maryland and six mesocosm replicates at Horn Point Laboratory in Cambridge, Maryland. During the two-year study period, the captive populations steadily declined. There was no sign of juvenile recruitment. Survival rates were low overall, although some individuals did recruit to higher size classes, resulting in populations dominated by individuals over 15 mm in length. Neither the mangrove nor the salt marsh mesocosms provided habitat suitable for reproduction or long-term survival of periwinkle snail populations.