Evaluating Habitat Provisioning and Restoration Potential of a Subtropical Seagrass Species in a Temperate Estuary

Accelerating human-induced losses of biogenic coastal ecosystems has prompted restoration of these critical habitats. In North Carolina, seagrass restoration has predominantly focused on Zostera marina, a temperate species, despite the potential for anthropogenic climate change to cause environmental shifts that favor Halodule wrightii, a tropical/subtropical species. We investigated how water depth and seasonality influenced H. wrightii distribution, restoration potential, and associated faunal community by (i) surveying North Carolina seagrass meadows to characterize their spatiotemporal distribution and morphology and (ii) conducting a restoration experiment testing the effect of transplantation depth (intertidal vs. subtidal) on H. wrightii restoration success and associated faunal communities. Surveyed meadows were increasingly dominated by H. wrightii from April to September. Seagrass within-species morphology differed across months, but only H. wrightii morphology and canopy height differed across depths, with canopy height increasing with bed depth. Intertidal H. wrightii transplants persisted > 18 months post-restoration, whereas nearly all subtidal transplants were lost within 6 months. We found no difference in faunal community abundance or structure between transplanted and control plots across depths. However, communities in the restored bed were less abundant and less species rich than those of a nearby reference bed. Although H. wrightii is widely distributed in estuarine waters of North Carolina, our results suggest small-scale transplantation does not lead to successful restoration or host communities equivalent to natural beds. Greater understanding of the role of H. wrightii as faunal habitat and identification of best restoration practices are critical to sustain and enhance ecosystem functioning in changing estuaries.