Chesapeake Bay is home to one of the largest oyster (Crassostrea virginica) restoration efforts in North America, as well as flourishing commercial fishing and aquaculture sectors. The shortage of fresh shell substrate has become a major barrier to all these activities, leading to the consideration of alternative substrates for large-scale use across all sectors. A laboratory experiment was performed at the UMCES Horn Point Laboratory in June 2024 to determine the biological and chemical suitability of alternative substrates for spat recruitment. In this project, alternative substrate was defined as anything other than fresh shells of C. virginica, including both natural (shell) and artificial (non-shell) substrates.
Nine different substrates were tested (dredged C. virginica shell, clam shell, whelk shell, C. gigas shell, recycled concrete, limestone marl, granite, river rock, and amphibolite) with fresh shells of C. virginica used as a control. Composition and diversity of the microbial communities associated with each substrate were characterised after 72h of conditioning to assess any differences in biofilm formation. Spat recruitment on each substrate was assessed after 6 weeks from settlement to determine larval preferences. The leaching of toxic chemicals and water quality were measured and monitored throughout the duration of the experiment to evaluate the impact of alternative substrates on water chemistry. The results of this study have the potential to improve public perception and facilitate the design of regulatory permits, both of which are considered crucial hurdles associated with the use of alternative substrates in restoration and harvest areas.