Sandy shorelines present a first line of defense against the catastrophic effects of storms and oil spills within the coastal zone of the northern Gulf of Mexico. Immediately following the DwH oil spill prior to any spill related impacts, we conducted a rapid response survey of the sandy shoreline benthic macrofauna from throughout the National Park Service - Gulf Islands National Seashore (GINS) in Mississippi and Florida. To characterize pre-spill macrofaunal assemblages, we surveyed seven barrier island or peninsular areas comprising nine exposed and 12 protected shoreline sites. A comparable benthic macrofaunal inventory had been conducted 17 years earlier using a parallel study design. The primary objective of this study was to distinguish hierarchical spatiotemporal scales of macrofaunal variation within the 1993 and 2010 GINS data. We hypothesized that the 1993 GINS macrofaunal inventory baseline was stable, despite multiple disturbances by large storms within the intervening 17-year period. Additionally, the relative importance of hierarchical spatial scales of macrofaunal dissimilarity was examined so suitable scales of macrofaunal variation could be identified for assessments of stressor effects at commensurate scales. An Implicit Nested Mixed Model PERMANOVA using Type 1 sequential Sum of Squares delineated variation components of nested scales which ranked Station > Shore Side > Site > Habitat > District > Year. The Year main factor had the smallest effect on macrofaunal variation, confirming that the 1993 GINS macrofaunal inventory can serve as the foundation for a robust baseline including both the 1993 and the 2010 macrofaunal data for the GINS. A literal Hierarchical Nested Mixed Model PERMANOVA using Type 1 sequential Sum of Squares (SS) partitioned effects among nested factors and their interactions. Definitive macrofaunal variation was expressed for all combinations of two levels for each of the three spatially nested fixed factors, District, Shore Side, and Habitat. Variation in macrofaunal dissimilarity for combined levels of fixed factors reflected corresponding differences in the macrofauna. The use of sandy shoreline macrofaunal assemblages as ecological indicators would fulfill the need to focus on cumulative effects of oil spills and should be eminently tractable when responses and impacts are considered on commensurate scales.

Production by macrofauna associated with oyster reefs offers a multi-purpose indicator of ecosystem function, ecological integrity, and restoration success. We examined responses by oyster-reef-associated macrofauna to a hypoxic event across three subtidal oyster-reef complexes in western Mississippi Sound as part of a large-scale restoration program. Four hypotheses within the context of a Linear mixed model examined differences in the following: (1) the macrofauna relative to the hypoxic event; (2) subregions relative to the severity of hypoxia; (3) responses by key macrofaunal taxa; and (4) short-term macrofaunal recovery. Densities and production potential of the entire oyster-reef macrofaunal community as well as for six key taxa all abruptly decreased in connection with the hypoxic event. Overall, total production potential and total density were four-fold lower in the summer of 2015 during the hypoxic event than in the summer of 2014. The degree of macrofaunal impact corresponded with the severity of hypoxia on the landscape scale. Total density and total production averaged nearly three-fold lower and more than eight-fold lower respectively across two critically hypoxic reef complexes compared to the least affected reef complex. Taxon-specific responses depended on tolerances to hypoxia as well as modes of reproduction and dispersal. Short-term macrofaunal recovery indicated surprising ecological resilience relative to the hypoxic interruption. Detrimental macrofaunal effects ameliorated substantially within several months when total production potential was comparable to that of the previous year. However, the short-term recovery of key taxa varied with respect to the hypoxic event. Hypoxia-induced seasonal directionality reversed between summer 2015 and fall 2015, as evidenced by lower values for total density, total production, and the density and production of the larger-bodied crustaceans, Eurypanopeus and Palaemonetes. Secondary production offers a key functional indicator of multiple ecosystem services and an informative gauge of ecological disturbance. Associated macrofauna should be used more widely to assess the ecological function and recovery of oyster reefs. This study expands our understanding of a productive oyster reef ecosystem that is threatened by multiple environmental challenges.