Hydrodynamic and biogeochemical evolution of a restored intertidal oyster (Crassostrea virginica) reef

David Cannon; Kelly Kibler; Linda Walters; Lisa Chambers

doi:10.1016/j.scitotenv.2022.154879

Hydrodynamic and biogeochemical evolution of a restored intertidal oyster (Crassostrea virginica) reef

Sci Total Environ. 2022 Jul 20:831:154879. doi: 10.1016/j.scitotenv.2022.154879. Epub 2022 Mar 29.

Authors

David Cannon¹, Kelly Kibler², Linda Walters³, Lisa Chambers³

Affiliations

¹ Department of Civil, Environmental, and Construction Engineering and National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL 32816, USA. Electronic address: David.Cannon@ucf.edu.
² Department of Civil, Environmental, and Construction Engineering and National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL 32816, USA.
³ Department of Biology and National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL 32816, USA.

PMID: 35358524
DOI: 10.1016/j.scitotenv.2022.154879

Abstract

Oyster reef restoration is increasingly used as a tool for restoring lost ecosystem services in degraded aquatic systems, but questions remain about the efficacy of the practice and when/if restored reefs may behave similarly to intact natural reefs. In this case study, field observations highlighted short- (<1 month post-restoration) and longer-term (30 months; 3 recruitment cycles) transformations in canopy, hydrodynamic, and biogeochemical characteristics of a restored intertidal oyster reef relative to nearby intact and degraded reefs. Within 12 months of restoration, live oyster density (326 oysters/m²), mean shell length (47 mm), and mean canopy height (76 mm) did not differ significantly from those observed on a reference reef. Lowering of the reef crest during restoration reestablished over-reef flow and periodic tidal inundation, improving hydraulic connectivity between the channel and the reef surface. This immediately restored much of the reef's hydrodynamic function and eliminated the irregular flow patterns observed on the previously degraded reef. Results showed that mean flow (channel-to-reef flow attenuation: 98% / 62%; within/above canopy) and velocity normalized turbulence (w^'2¯/U²: 10^-1/10^-2; ϵ/U³: 10⁰/10^-2 m^-1) characteristics were similar across the restored and reference reefs within 1 year of restoration, with temporal changes in mixing within the canopy attributed to increases in live oyster density. Nutrient pools (mean total carbon, total nitrogen) on reference and restored reefs had similar magnitudes within 1 year (C: 39 & 33 g/kg, N: 1.5 & 1.8 g/kg), while increases in DOC and NH₄⁺ were correlated with the presence of live oysters. Most changes that occurred on the restored reef were linked to oyster recruitment and canopy growth, which modulated hydrodynamics through direct flow interactions and controlled sediment nutrient and organic matter content through waste deposition and burial.

Keywords: Carbon; Ecohydraulics; Estuary; Nitrogen; Restoration; Turbulence.

MeSH terms

Animals
Carbon
Crassostrea*
Ecosystem
Hydrodynamics
Nitrogen

Substances

Carbon
Nitrogen