Reef height drives threshold dynamics of restored oyster reefs

Colden, Allison; Latour, Robert J.; Lipcius, Romuald N.

doi:10.3354/meps12362

Cited by 51 publications

(61 citation statements)

References 61 publications

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“…While there is some data on the relationship between substrate and recruitment (Colden et al. ), much is still unknown, and oyster restoration efforts would likely benefit from additional studies investigating this relationship.…”

Section: Discussionmentioning

confidence: 99%

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Restoration of eastern oyster populations with positive density dependence

Moore

Puckett

Schreiber

2018

Ecological Applications

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Positive density dependence (i.e., Allee effects) can create a threshold of population states below which extinction of the population occurs. The existence of this threshold, which can often be a complex, multi-dimensional surface, rather than a single point, is of particular importance in degraded populations for which there is a desire for successful restoration. Here, we incorporated positive density dependence into a closed, size- and age-structured integral projection model parameterized with empirical data from an eastern oyster, Crassostrea virginica, population in Pamlico Sound, North Carolina, USA. To understand the properties of the threshold surface, and implications for restoration, we introduced a general method based on a linearization of the threshold surface at its unique, unstable equilibrium. We estimated the number of oysters of a particular age (i.e., stock enhancement), or the surface area of dead shell substrate required (i.e., habitat enhancement) to move a population from an extinction trajectory to a persistence trajectory. The location of the threshold surface was strongly affected by changes in the amount of local larval retention. Traditional stock enhancement with oysters <1 yr old (i.e., spat) required three times as many oysters relative to stock enhancement with oysters between ages 3 and 7 yr old, while the success of habitat enhancement depended upon the initial size distribution of the population. The methodology described here demonstrates the importance of considering positive density dependence in oyster populations, and also provides insights into effective management and restoration strategies when dealing with a high dimensional threshold separating extinction and persistence.

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Section: Discussionmentioning

confidence: 99%

“…In field experiments, Colden et al. () demonstrated a threshold reef height above which oyster reefs persisted and below which the reefs degraded to local extinction. These results indicate that a critical threshold of reef height is required for persistence.…”

Section: Introductionmentioning

confidence: 99%

Restoration of eastern oyster populations with positive density dependence

Moore

Puckett

Schreiber

2018

Ecological Applications

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“…, Colden et al. ). The overarching aim of the present paper is to improve current understanding of the role of spatial and temporal variable biogenic substrata on the establishment thresholds of ecosystem engineers, using the establishment of reef‐forming mussels at soft‐bottom environments as an ideal model species.…”

Section: Introductionmentioning

confidence: 99%

Creating a window of opportunity for establishing ecosystem engineers by adding substratum: a case study on mussels

et al. 2019

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Ecosystem engineers typically exert positive feedback on their environment, which enhances their performance. Such positive feedback is lacking in the establishment phase, when densities are too low and/or patches are too small. There is a strong need to unravel the mechanisms for overcoming the resulting establishment thresholds, both for ecological restoration purposes and to be able to use their services. In the present study, we question whether providing a transient substratum can be used as tool to overcome establishment thresholds, by creating a window of opportunity for initial settlement, using mussels (Mytilus edulis) as a model system. Combining field and flume experiments, we study how biogenic substratum enrichment in the form of a shell layer on a soft mudflat affects the critical dislodgement thresholds and, thus, the chances of mussel establishment at different mussel densities and aggregation states. Flume results showed that the presence of a shell layer reduced dislodgement of mussel patches in low‐energy environments but was conditional for establishment in high‐energy environments. That is, in high‐energy environments with shells, aggregation into clumps enhanced dislodgement, while dislodgement was reduced with increasing overall mussel biomass and overall mussel patch weight. Without shells, dislodgement was always 100%. These findings agreed with our field studies, which showed that coarse shell material reduced mussel losses (by a factor of 3), reduced aggregation (by a factor of 2.4), and increased attachment strength (by a factor of 2.4). Overall, our results show that the local presence of biogenic substratum increases the chance of mussel establishment by enhancing the critical hydrodynamic dislodgement threshold. Thus, the local addition of a biogenic substratum may create a window of opportunity to initiate settlement in more dynamic environments, to shift at a local scale from a bare mudflat state into an established biogenic reef state. Our findings have clear implications for how to approach restoration and management of ecosystem engineers dominated systems. For instance, when positive feedback of ecosystem engineers is lacking, (1) the transient offering of suitable settling substratum may be a necessary step to overcome establishment thresholds, and (2) this becomes increasingly important with increasing abiotic stress.

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“…Empirical data, field experiments, and restoration efforts also support the concept of alternative stable states and the importance of reef height on persistence (Powell et al 2009a, b, Schulte et al 2009, Colden et al 2017). For example, Powell et al (2009b) analyzed a time series of C. virginica populations in Delaware Bay from 1953 to 2006 and found that the population persisted for extended periods of time in two distinct states, one of high abundance, and one of low abundance.…”

Section: Introductionmentioning

confidence: 92%

“…Locations restored with high vertical reefs had greater oyster densities and were likely to persist, while populations restored with low vertical reefs had low oyster densities and were predicted to decline to extinction within a handful of years. In field experiments, Colden et al (2017) demonstrated a threshold reef height above which oyster reefs persisted and below which the reefs degraded to local extinction. These results indicate that a critical threshold of reef height is required for persistence.…”

Section: Introductionmentioning

confidence: 99%

Restoration of Eastern oyster populations with positive density dependence

Moore

Puckett

Schreiber

2017

Preprint

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Positive density dependence can create a threshold of population states below which extinction of the population occurs. The existence of this threshold, which can often be a complex, multi-dimensional surface, rather than a single point, is of particular importance in degraded populations for which there is a desire for successful restoration. Here, we incorporated positive density dependence into a closed, size-and age-structured integral projection model parameterized with empirical data from an Eastern oyster, Crassostrea virginica, population in Pamlico Sound, North Carolina. To understand the properties of the threshold surface, and implications for restoration, we introduced a general method based on a linearization of the threshold surface at its unique, unstable equilibrium. We estimated the number of oysters of a particular age (i.e. stock enhancement), or the surface area of hard substrate required (i.e. habitat enhancement), to move a population from an extinction trajectory to a persistent trajectory. The location of the threshold surface was strongly affected by changes in the amount of local larval retention. Traditional stock enhancement with oysters less than a year old (i.e. spat) required three times as many oysters relative to stock enhancement with oysters between ages three and seven, while the success of habitat enhancement depended upon the initial size distribution of the population. The methodology described here demonstrates the importance of considering positive density dependence in oyster populations, and also provides insights into effective management and restoration strategies when dealing with a high dimensional threshold separating extinction and persistence. KEYWORDSCrassostrea virginia, oyster demography, oyster restoration, integral-projection model, positive density dependence, stock enhancement, habitat enhancement 2 peer-reviewed)

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Reef height drives threshold dynamics of restored oyster reefs

Cited by 51 publications

References 61 publications

Restoration of eastern oyster populations with positive density dependence

Restoration of eastern oyster populations with positive density dependence

Creating a window of opportunity for establishing ecosystem engineers by adding substratum: a case study on mussels

Restoration of Eastern oyster populations with positive density dependence

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