Oyster Reef Restoration in the Northern Gulf of Mexico: Effect of Artificial Substrate and Age on Nekton and Benthic Macroinvertebrate Assemblage Use

Abstract

In the northern Gulf of Mexico (GOM), reefs built by eastern oysters, Crassostrea virginica, provide critical habitat within shallow estuaries, and recent efforts have focused on restoring reefs to benefit nekton and benthic macroinvertebrates. We compared nekton and benthic macroinvertebrate assemblages at historic, newly created (<5 years) and old (>6 years) shell and rock substrate reefs. Using crab traps, gill‐nets, otter trawls, cast nets, and benthic macroinvertebrate collectors, 20 shallow reefs (<5 m) in the northern GOM were sampled throughout the summer of 2011. We compared nekton and benthic assemblage abundance, diversity and composition across reef types. Except for benthic macroinvertebrate abundance, which was significantly higher on old rock reefs as compared to historic reefs, all reefs were similar to historic reefs, suggesting created reefs provide similar support of nekton and benthic assemblages as historic reefs. To determine refuge value of oyster structure for benthic macroinvertebrates compared to bare bottom, we tested preferences of juvenile crabs across depth and refuge complexity in the presence and absence of adult blue crabs (Callinectes sapidus). Juveniles were more likely to use deep water with predators present only when provided oyster structure. Provision of structural material to support and sustain development of benthic and mobile reef communities may be the most important factor in determining reef value to these assemblages, with biophysical characteristics related to reef location influencing assemblage patterns in areas with structure; if so, appropriately locating created reefs is critical.

Oyster reef restoration: substrate suitability may depend on specific restoration goals

“…The change in community composition from a suspected early to later stage community development between April and July 2014 occurred because of an increase in species richness, and a much larger increase in faunal density. A shift from early to later stage community development is consistent with other studies, indicating that the age of a reef affects oyster development and associated faunal community characteristics (Burt et al ; Quan et al ; Brown et al ). Diversity of motile fauna was greatest in early reef development, and least in the summer (driven by higher densities), indicating when dominant organisms colonized the reef.…”

“…Reefs formed by Crassostrea virginica (eastern oysters) add complexity to otherwise soft-bottom estuaries in the Gulf of Mexico, increasing species diversity of associated organisms (Harding & Mann 2000, Gutiérrez et al 2003. Therefore, reductions of reef habitat may also lead to losses of biodiversity (Lotze et al 2006;Airoldi et al 2008;Brown et al 2014).…”

Influence of the artificial reef size configuration on transient ichthyofauna – Southeastern Brazil

“…Artificial reefs are increasingly being used as tools for habitat recovery, mainly due to their growing use in the increase of biodiversity and recovery of fish stocks (Caddy, 1999;Fabi et al, 2011;Feary et al, 2011;Polovina, 1991;Brown et al, 2014;Walker and Schlacher, 2014). Such use is due, in part, to the greater facility with which artificial reefs can be managed in terms of their architecture (e.g., material, size, complexity and arrangement of the reef modules) in comparison to natural habitats.…”

Natural cultch type influences habitat preference and predation, but not survival, in reef‐associated species

“…By forming complex structures that provide spaces for feeding, nesting, and refuge from predators and other environmental stressors (Bartol et al , p 199; Bartholomew et al ; Gutiérrez et al ; Coen et al ), oysters play a crucial role as ecosystem engineers. The complex habitat created by oyster reefs supports a suite of species not found in nearby habitats (Coen & Luckenbach ; Tolley & Volety ; Scyphers et al ; Brown et al ) and variation in complexity impacts survival and interactions among species (Lenihan ; Grabowski ; Grabowski et al ). Reefs also serve important roles in the protection of shorelines (Coen et al ; Furlong ) and the stabilization of marsh areas (Meyer et al ; Piazza et al ; Scyphers et al ).…”

“…The smaller, more uniform pieces of fossil cultch visually appear to form reefs that are more compact and dense compared to reefs constructed of whole‐shell cultch due to the wide range in size and shape of fresh cultch pieces. For these reasons, reefs formed of fossil cultch may differ from reefs formed of whole‐shell natural or dredged cultch in habitat structure, including interstitial space, which is an important habitat characteristic in determining reef outcomes (Schulte et al ; Brown et al ). Interstitial spaces and the habitat heterogeneity they create across tidal gradients are crucial for recruitment and survival of oysters and benthic macroinvertebrates (Bartol et al ; Soniat et al ; Tolley & Volety ; Gregalis et al ; Brown et al ) and influence local sedimentation and hydrodynamics (Soniat et al ; Schulte et al ).…”