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Oyster reef fauna counts and lengths were sampled at natural "reference" reefs and restored shell plant reefs located in the Virginia Coast Reserve. Overfishing and disease decimated oyster reefs in the Virginia Coast Reserve in the 1900s. Reference reefs were defined as remnant reefs that naturally recovered in the early 2000s to develop the pronounced vertical structure and multiple oyster size classes that represent the desired endpoint of restoration efforts. Nearly every year since 2003, The Nature Conservancy and Virginia Marine Resource Commission have constructed oyster reefs in intertidal areas in the VCR. To construct the restored reefs, practitioners launched dredged, fossilized oyster shell from barges to intertidal locations chosen for their bottom stability and accessibility (locations lacked oysters prior to construction). Whelk shell supplemented the oyster shell at some of the restored reefs. TNC practitioners monitor select restored and reference reefs annually for adult and spat live oysters, adult and spat box oysters, mud crabs, mud snails, oyster drills, live clams, and mussels.
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Success of concrete and crab traps in facilitating Eastern oyster recruitment and reef development
Background Abundance of the commercially and ecologically important Eastern oyster, Crassostrea virginica , has declined across the US Eastern and Gulf coasts in recent decades, spurring substantial efforts to restore oyster reefs. These efforts are widely constrained by the availability, cost, and suitability of substrates to support oyster settlement and reef establishment. In particular, oyster shell is often the preferred substrate but is relatively scarce and increasingly expensive. Thus, there is a need for alternative oyster restoration materials that are cost-effective, abundant, and durable. Methods We tested the viability of two low-cost substrates—concrete and recycled blue crab ( Callinectes sapidus ) traps—in facilitating oyster recovery in a replicated 22-month field experiment at historically productive but now degraded intertidal oyster grounds on northwestern Florida’s Nature Coast. Throughout the trial, we monitored areal oyster cover on each substrate; at the end of the trial, we measured the densities of oysters by size class (spat, juvenile, and market-size) and the biomass and volume of each reef. Results Oysters colonized the concrete structures more quickly than the crab traps, as evidenced by significantly higher oyster cover during the first year of the experiment. By the end of the experiment, the concrete structures hosted higher densities of spat and juveniles, while the density of market-size oysters was relatively low and similar between treatments. The open structure of the crab traps led to the development of larger-volume reefs, while oyster biomass per unit area was similar between treatments. In addition, substrates positioned at lower elevations (relative to mean sea level) supported higher oyster abundance, size, and biomass than those less frequently inundated at higher elevations. Discussion Together, these findings indicate that both concrete and crab traps are viable substrates for oyster reef restoration, especially when placed at lower intertidal elevations conducive to oyster settlement and reef development.
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- Award ID(s):
- 1652628
- PAR ID:
- 10087032
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 7
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e6488
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Oysters,Crassostrea virginica, are economically and ecologically valuable but have severely declined, and restoration is needed. As with the restoration and aquaculture of many shellfish species, restored oyster reefs are often impeded by predation losses, reducing restoration success and restricting locations where restored reefs are viable. Like many organisms, shellfish can modify their morphology to reduce predation risk by detecting and responding to chemical signals emanating from predators and injured prey. Oysters grow heavier, stronger shells in response to predation risk cues, which improves their survival. We tested if using predator cues to trigger shell hardening in oysters could be performed over a scale suitable for oyster reef restoration and improve oyster survival long‐term. We constructed an intertidal oyster reef using oysters grown in a nursery for 4 weeks while exposed to either exudates from Blue crab (Callinectes sapidus) predators or grown in controls without predator cues. Oysters grown with predators were 65% harder than those grown in controls, and after 1 year in the field, had a 60% increase in survival. Predation losses on the restored reef were significant, and the benefit of predator induction for survival was highest at intermediate tidal elevations, presumably due to intermediate levels of predation and abiotic stress. Our results suggest that manipulating the morphology of cultivated or restored species can be an effective tool to improve survival in habitats where consumers impede restoration success.more » « less
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Oyster reefs provide crucial ecosystem services, but their populations are declining worldwide. Oyster reef restoration efforts are underway in many regions, including the Gulf Coast of the United States, where the intertidal oyster populations of the eastern oyster, Crassostrea virginica, have experienced significant declines. A novel method of restoration aimed at decreasing oyster mortality from predators through induction of predatory defenses has been implemented in coastal Alabama. The first step in this novel oyster reef restoration method is the deployment of a base layer of uninhabited oyster shells directly on the sediment prior to the introduction of live oysters. This study evaluated the impacts of the first step of this novel method of restoration, construction of the reef structure, on local sediment physicochemical characteristics. Results indicate that the vertical structure of the oyster reef affects sediment grain size and physicochemical properties. After 47 days, sediment pH increased from 8.29 ± 0.04 to 8.86 ± 0.03 with a concomitant increase in calcium carbonate from 0.509 ± 0.021 % to 0.818 ± 0.112 %. Despite many positive geochemical effects of oyster reef restoration being mediated by the presence of live oysters, the increased pH and calcium carbonate demonstrated herein represent more ideal conditions for oyster growth and survivability, potentially increasing the long-term efficacy of oyster reef restoration via this method.more » « less
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This dataset has been superceded by Lusk, B., R. Smith, and M.C.N. Castorani. 2024. Oyster fauna lengths, counts, and biomass from restored and reference reefs in Virginia coastal bays, 2005-2023 ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/d68de69f29cee5f737313a07f813f245 (Accessed 2024-02-22). which includes additional years and parameters. Oyster and associated reef fauna counts and lengths were sampled at 16 natural reference reefs and 61 restored shell plant reefs located at 18 sites in the Virginia Coast Reserve. Overfishing and disease decimated oyster reefs in the Virginia Coast Reserve in the 1900s. Reference reefs were defined as remnant reefs that naturally recovered in the early 2000s to develop the pronounced vertical structure and multiple oyster size classes that represent the desired endpoint of restoration efforts. Nearly every year since 2003, The Nature Conservancy and Virginia Marine Resource Commission have constructed oyster reefs in intertidal areas in the VCR. To construct the restored reefs, practitioners applied dredged, fossilized oyster shell to intertidal locations chosen for their bottom stability and accessibility (locations lacked oysters prior to construction). Whelk shell supplemented the oyster shell at 9 of the restored reefs.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.7717/peerj.6488
