A hybrid shoreline stabilization technique: Impact of modified intertidal reefs on marsh expansion and nekton habitat in the northern Gulf of Mexico

To mitigate shoreline erosion numerous armoring techniques have been employed extensively along the degrading shores of the Gulf of Mexico (GoM). Shoreline armoring strategies incorporating built vertical structures have resulted in numerous undesired ecological consequences. Bioengineering hybrid techniques consisting of “living shorelines” are emerging as an alternative option to mitigating shoreline loss and overcoming ecological shortcomings of hardened structures. Hitherto, only a few studies have assessed efficacy of hybrid techniques on shoreline stabilization and adjacent habitat enhancement. In this study, we integrated permeable intertidal reef-breakwaters (also known as wave attenuation units or WAUs) and predominantly restored native Spartina alterniflora marsh vegetation to mitigate erosion along severely degrading shores of a narrow peninsula in the northern GoM. Particularly, we evaluated impacts of a large-scale WAU reef deployment on a range of physical and biological parameters including erosion mitigation (shoreline stabilization), facilitation of created marsh expansion and habitat provision to marsh-utilizing nekton. We compared WAU reefs to adjacent gap areas without WAUs to evaluate the effects of tidal openings on the metrics measured. Our results of over 3 years suggest that, intertidal WAU reefs facilitate in created marsh expansion and the tidal openings between the reef complexes allow free movement of marsh-utilizing nekton fauna. Based on our results, we conclude that hybrid restoration technique is highly efficacious on erosion mitigation, adjacent marsh expansion and habitat creation. However, more works in other coastal systems are required to confirm the impacts of hybrid techniques on erosion mitigation and consequently on marshes and marsh-utilizing nekton.