Dynamics of Hard Substratum Communiities Inside and Outside of a Fisheries Habitat Closed Area in Stellwagen Bank. National Marine Sanctuary (Gulf of Maine, NW Atlantic)

摘要

The dynamics of gravel and boulder reef invertebrate community structure in areas inside and outside a closed fisheries habitat that overlaps Stellwagen Bank National Marine Sanctuary were analyzed based on time-series photographic transects from 1998-2005. The effectiveness of this protected area was evaluated based on three common predictions that emerge from previous studies of fishing impacts and the performance of temperate marine protected areas. We determined if: (1) gravel and boulder habitats have similar community composition, (2) community structure diverged between fished and unfished sites attributable to chronic fishing impacts, (3) structure forming invertebrates increased in abundance within the protected area, and (4) diversity increased within the protected area. Overall our results demonstrate that community structure over the seven years since closure in 1998 has been dynamic across both habitat types as well as within and outside the Western Gulf of Maine Closure (WGOMC) despite a high degree of similarity between paired habitat stations at the time of closure. Comparisons of each habitat type inside and outside the closure across years in regards to community structure, populations of component taxa, and patterns of diversity all demonstrated a response to the closure but not in ways that are normally predicted from previous closed areas studies. Despite the presence of hard substratum resources in both boulder and gravel habitats, community structure was different between habitat types across all years. Community structure changed across time both inside and outside the WGOMC suggesting, at least to-date, recovery without resilience. While community composition tended to be more similar within each station than between each year, the pattern of similarity from 2005 transects suggest a greater degree of difference in composition between replicates from inside gravel and boulder stations than those paired stations outside. This pattern suggests the dominance of local processes, such as predation and competition, may be driving community composition inside the closed areas (i.e., contributing to greater variation in the distributions of taxa within stations). This is in contrast to larger spatial scale disturbance processes, produced either by natural events or by fishing activities that dominate at outside stations. Species populations and community structure within the closed area have yet to reach any stable configuration.