Correlation of the Structural Characteristics of an Artificial Oyster Reef with Its Wake Region

Abstract

Oyster reefs are currently at risk of severe decline due to dangerous human interference and its aftermath; hence, artificial oyster reefs (AORs) have been utilized for their restoration. AORs with high vertical reliefs interact with the surrounding flow, constitute a reverse flow, and create a wake region in which concentrated nutrients and food organisms exist. However, the correlations of the structural characteristics of an AOR with its wake regions have not been studied. Thus, we established 96 AOR models, carried out flow analyses, and obtained their wake volumes, considering shell orientation, composition, penetration depth, and growth stage. We found that the growth stage is the most critical parameter for establishing a normalized wake volume. This implies that the number of oyster shells (N) is the most critical factor in securing a normalized wake volume, in which their correlation was linear and significant (R2=0.89). We also found that the correlations of the normalized wake volume with blocking and surface complexity indices were linearly significant, respectively. Additionally, wake volume efficiency increased with the number of oyster shells; specifically, the criterion for wake volume efficiency of EI (efficiency index) ≥ 2.0 was satisfied when N≥50 per 900 cm2.