Subtidal resource inventories at Assateague Island: resolving Hurricane Sandy's impact on benthic assemblages and habitats

Miller, Douglas C.As part of a benthic habitat mapping project for the National Park Service, I aim to characterize the subtidal habitats and invertebrate communities of the nearshore zone of Assateague Island National Seashore (ASIS), providing an updated assessment to inform management decisions at ASIS. I will also outline any changes in benthic assemblages between previous and current surveys, to determine if I can resolve any impacts of Hurricane Sandy. In October 2014 and 2015, I sampled the benthic zone with modified Young grabs, taking subsamples to determine grain size distributions and total organic carbon of sediments. Both pre-storm and post-storm, benthos assemblages significantly differ between sediment classes (ANOSIM R=0.677, 0.263 respectively, p<0.01). Assemblages are unchanged at class level, but the opportunistic Mediomastus ambiseta increasingly dominates across all sediments from 2011 to 2015 (SIMPER). Post-storm samples are more interspersed (nMDS) and show less similarity within sediment class groupings (SIMPER) than pre-storm samples. Shannon and Simpson diversity consistently decrease across the shared sediment classes. Distance-based RDA ordinations (DistLM) relating environmental variables to assemblage patterns show that sediment classification explains the greatest proportion of assemblage variation both pre-storm (17.8%, p<0.01) and post-storm (39%, p<0.01). Dominant sediment classes at the grab level show a considerable shift towards finer grain sizes from 2011 to 2015. Assemblage composition is significantly different between post-storm sampling years (ANOSIM R=0.093, p