Nested spatiotemporal scales of variation in sandy-shore macrobenthic community structure

We considered the relative importance of several spatiotemporal scales of v ariability in sandy-shore macrobenthic community structure from a comprehen sive inventory of the Gulf Islands National Seashore in 1993, including bot h Mississippi and Florida districts. Historical variation also was consider ed through the comparison of macrobenthic data taken previously, in 1986-19 87, from the same region. Macrobenthic community metrics, including species richness, diversity, total density, and community dissimilarity varied on several spatiotemporal scales, including landscape, regional, historic, and seasonal levels. Community metrics all conveyed greater faunal complexity with decreasing exposure to wave disturbance, as effected by both seaward d istance/depth and shore side. The nesting of macrobenthic variation did not directly parallel the hierarchy of spatiotemporal scales. Rather, multivar iate analyses showed hierarchically inclusive levels of community variation headed by the landscape scale, and successively followed by the regional s cale, the historical scale, the habitat scale, and the seasonal scale. Macr obenthic assemblages were relatively similar between historical and contemp orary collections from the same district. Moderate seasonal variability in community metrics usually revealed greater faunal complexity in summer and autumn. Variability in total density across seasons, seaward distances, and sites was not driven by particular dominant tars; and dominant taxa occurr ed more consistently across seasons at individual locations than across sta tions within any given season. However, distinctive distribution patterns f or the 23 selected common sandy-shore macrobenthic taxa used in multivariat e analyses helped explain the observed scales of variation. This study will have lasting value to the extent that it provides a multi-year regional co mparative reference for future biodiversity assessments.