Abstract
Restoration strategies for native oyster populations rely on multiple sources of information, which often conflict due to time- and space-varying patterns in abundance and distribution. For instance, strategies based on population connectivity and disease resistance can differ, and extant and historical records of abundance and distribution are often at odds, such that the optimal strategy is unclear and valuable restoration sites may be excluded from consideration. This was the case for the Lynnhaven River subestuary of lower Chesapeake Bay, which was deemed unsuitable for Eastern Oyster restoration based on physical conditions, disease challenge, and extant oyster abundance. Consequently, we (i) evaluated previously unknown historical data from the 1800s, (ii) quantified extant oyster recruitment and abundance, physical conditions, and disease presence on constructed restoration reefs and alternative substrates, and (iii) assessed simulations from biophysical models to identify potential restoration sites in the metapopulation. The collective data distinguished numerous restoration sites (i) in the polyhaline zone (salinity 18.4-22.2) where disease resistance is evolving, (ii) where oysters were abundant in the late 1800s-early 1900s, (iii) of recent high recruitment, abundance and survival, despite consistent and elevated disease challenge, and (iv) interconnected as a metapopulation via larval dispersal. Moreover, a network of constructed restoration reefs met size structure, abundance and biomass standards of restoration success. These findings demonstrate that assumptions about the suitability of sites for oyster restoration based on individual processes can be severely flawed, and that in-depth examination of multiple processes and sources of information are required for oyster reef restoration plans to maximize success. We use these findings and previous information to recommend a strategy for successful restoration of subtidal oyster reefs throughout the range of the Eastern Oyster.
Highlights
Novel restoration approaches led to persisting populations of native C. virginica on constructed natural and alternative oyster reefs protected from exploitation in Delaware Bay (Taylor and Bushek, 2008), North Carolina sounds (Powers et al, 2009), and Chesapeake Bay (Lipcius and Burke, 2006; Schulte et al, 2009), indicating that restoration of C. virginica was feasible and that introduction of a non-native species was not necessary
In this study we describe a field experiment in which restoration oyster reefs were constructed and succeeded at sites selected using historical data and information on metapopulation connectivity, rather than relying solely on extant oyster abundance and disease challenge, in the Lynnhaven River system of Chesapeake Bay for which it was previously concluded that restoration was unfeasible due to disease, sedimentation, low substrate availability, and unsuitable hydrodynamics (Berman et al, 2002; Mann and Powell, 2007)
The largest oyster beds and highest abundances occurred in Broad Bay and Linkhorn Bay, where most of our restoration reefs were located (Figures 3, 4)
Summary
Native oyster species of the family Ostreidae were once dominant ecosystem engineers worldwide, including the Olympia oyster Ostrea lurida along the northeast Pacific coast (Ruesink et al, 2005), the European flat oyster Ostrea edulis of the northeastern Atlantic (Airoldi and Beck, 2007), the Sydney rock oyster Saccostrea glomerata of the Pacific coasts of Australia and New Zealand (Ogburn et al, 2007), and the eastern oyster Crassostrea virginica of the western Atlantic and Gulf of Mexico (Winslow, 1881; Baylor, 1895). Novel restoration approaches led to persisting populations of native C. virginica on constructed natural and alternative oyster reefs protected from exploitation in Delaware Bay (Taylor and Bushek, 2008), North Carolina sounds (Powers et al, 2009), and Chesapeake Bay (Lipcius and Burke, 2006; Schulte et al, 2009), indicating that restoration of C. virginica was feasible and that introduction of a non-native species was not necessary Despite these apparent successes, the scientific community has not reached consensus either on the major barriers for restoration efforts or on the most effective approaches to achieve success (Kennedy et al, 2011). We integrate our results with prior findings to alter the existing paradigm on key factors necessary to achieve successful native oyster restoration, and to devise a restoration strategy that integrates multiple, interacting processes
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