Reef restoration facilitates habitat provisioning for oysters and motile epifauna

Abstract

Severe degradation of oyster reef habitat over the past century has led to associated losses in ecological and economic benefits. Common oyster reef restoration goals target replacement of lost ecosystem services, including habitat provision, by replacing the ecological functions of lost reef habitats. The goal of this study was to monitor development of faunal communities on a restored oyster reef in the Gulf of Mexico. In July 2017, more than 1 M tons of reclaimed oyster shell were used to restore 1.83 ha of oyster reef complex (~610 linear m) in St. Charles Bay, Texas. Oysters, epifauna, and infauna were sampled monthly for the first three months after construction, and then were sampled quarterly for a total of 19 months at the restored reef and nearby reference sites. Within the first three months after construction, mean oyster densities increased by more than three times, growth rates peaked at 0.41 mm d-1 , and the restored oyster population shifted from 100 % spat to more than 90 % submarket size oysters. Although Perkinsus marinus infection was detected on every sampling date on the reference reef, only a single infected oyster was observed on the restored reef. Reef location—away from infected source populations— and other hydrological factors such as current speed and direction, may have impeded disease development. Epifaunal density, biomass, and diversity, became similar to that of the reference reef within four months after construction, but a shift in epifaunal community assemblages occurred between the first and the second year after construction, indicating monitoring periods of more than one year are necessary to capture faunal community development on a restored reef. The structure provided by the restored reef was conducive to oyster and epifaunal community development and may have supported ecological resistance since minimal impacts to reef structure were observed in the wake of Hurricane Harvey. Infaunal density, diversity, and biomass did not differ between sites adjacent (less than 5 m) versus distant (~30 m) from the restored reef and were governed more by salinity than presence of the restored reef. The recruitment and densities of oysters indicate that the restored reef met proposed success metrics within 19 months after construction, and that restored reefs can successfully replace ecosystem services, such as habitat provision, lost due to degradation.