ALTERNATIVE SUBSTRATES FOR RESTORATION OF THE CHESAPEAKE BAY’S EASTERN OYSTER, CRASSOSTREA VIRGINICA: AN EVALUATION USING ADDITIVE MANUFACTURING AND ELECTROLYSIS MINERAL ACCRETION

Abstract

Over the past century, the population of the Chesapeake Bay’s eastern oyster, Crassostrea virginica, has collapsed dramatically, endangering the ecology of the bay and economy of the surrounding area. Declining shell numbers limit the growth of current oyster populations and have led to the use of alternative substrate material as a method for oyster restoration. Motivated by successful coral reef restoration efforts and the emerging field of additive manufacturing, we tested the use of electrolysis mineral accretion and Fused Deposition Modeling (FDM) to create artificial substrate for oyster spat settlement and survival. To start, we employed electrolysis mineral accretion with the goal of creating a sustainable and adequate amount of calcium carbonate (CaCO3) substrate. Mineral accretion rates were restrictive in our closed system, and we were unable to create sufficient substrate to test settlement. Second, we used 3D scanning and FDM to print artificial oyster shells identical to their natural counterparts, using a filament containing CaCO3. Using 3D printed oyster shells, we tested the importance of physical structure versus the presence of intrinsic biochemical cues in oyster settlement rates. Our results indicated that the oyster spat did not achieve significant survival on the printed material. Similarly, the use of the biochemical cue L-DOPA was insufficient in encouraging larval settlement on printed shells, indicating the significant role played by the underlying shell composition. The results indicate that the biochemical properties of the substrate take precedence over the geometric similarity to natural shells, a finding which should guide future methodology in oyster restoration.