Article

Oyster reefs can outpace sea-level rise

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Abstract

In the high-salinity seaward portions of estuaries, oysters seek refuge from predation, competition and disease in intertidal areas1,2, but this sanctuary will be lost if vertical reef accretion cannot keep pace with sea-level rise (SLR). Oyster-reef abundance has already declined ⇠85% globally over the past 100 years, mainly from over harvesting3,4 , making any additional losses due to SLR cause for concern. Before any assessment of reef response to accelerated SLR can be made, direct measures of reef growth are necessary. Here, we present direct measurements of intertidal oyster-reef growth from cores and terrestrial lidar-derived digital elevation models. On the basis of our measurements collected within a mid-Atlantic estuary over a 15-year period, we developed a globally testable empirical model of intertidal oyster-reef accretion. We show that previous estimates of vertical reef growth, based on radiocarbon dates and bathymetric maps5,6, may be greater than one order of magnitude too slow. The intertidal reefs we studied should be able to keep up with any future accelerated rate of SLR (ref. 7) and may even benefit from the additional subaqueous space allowing extended vertical accretion.

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... However, SfM photogrammetry has been effective at gathering basic structural information in intertidal habitats using unoccupied aircraft systems (UAS, or drones), like emergent oyster reefs, that can be imaged at low tide (Windle et al., , 2022. Previously, oyster reef structure has been measured using conventional methods like the chain technique (Margiotta et al., 2016;Rodney & Paynter, 2006) or 3D surface models created from closerange LiDAR using a terrestrial laser scanner (TLS, Ridge et al., 2017;Rodriguez et al., 2014). These methods can provide structural resolution that is relevant to the oyster population at the individual-to-cluster scale-as opposed to reef scale metrics that would be surveyed from higher altitude data from occupied aircraft and satellites. ...
... To compare different 3D survey methods, we mapped all seven study reefs (including the reef located in Back Sound used for the Replicability study) using both UAS imagery and a terrestrial laser scanner (TLS). TLS surveys followed the same process as previously demonstrated on oyster reefs (Ridge et al., 2015;Rodriguez et al., 2014) relying on exposure of the reef during low tide to image the oysters. This is crucial because the near-infrared laser of the scanner cannot penetrate the water but has performed well even on the wet surfaces of the recently exposed oysters. ...
... This work examined two pathways for imaging oyster reefs and obtaining structural metrics, which provide key insights into these habitats and the surrounding ecosystem. TLS has been used to effectively monitor minute changes to structure in a number of circumstances (see review in Mukupa et al., 2017), and has been shown to be consistent across iterative surveys of the same structure (Rodriguez et al., 2014). The consecutive UAS surveys conducted here showed similar consistency in the derived 3D products of an oyster reef (Fig. 2), further establishing the reliability of the method. ...
Article
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Physical structures generated from ecosystem engineers can have a cascade of impacts on the ecological community and the surrounding landscape. The Eastern oyster Crassostrea virginica can form extensive intertidal reefs, whose three‐dimensional structures provide ecosystem services like nursery and foraging habitat for fishes and invertebrates and shoreline stabilization. Measurements of the structural properties of these reefs provide opportunities to quantitatively assess associated services. There is a growing variety of tools available for measuring three‐dimensional (3D) properties of intertidal habitats, including two remote sensing methods that capture 3D structural metrics in a number of environments. We surveyed reefs using a terrestrial laser scanner (TLS, LiDAR) and imagery from unoccupied aircraft systems (UAS, or drones) processed through Structure from Motion photogrammetry. Comparisons of digital elevation models from repetitive flights over an oyster reef to checkpoints yielded mean horizontal and vertical root mean square errors (RMSE) of −0.54 ± 0.47 cm and 0.97 ± 1.0 cm (Mean ± SD), respectively, indicating high accuracy among UAS surveys. Compared to TLS products, point cloud densities from UAS‐derived products were more consistent across the reef elevation gradient and much denser overall except in the low reef zone, which was proximal to most of the TLS scan locations. Comparisons of structural metrics between UAS and TLS showed similarities in metrics like profile and planform curvatures, yet indicated UAS surveys produced higher values of surface complexity and slope. Results indicate that UAS photogrammetry can produce robust oyster reef structural metrics that can be highly useful in oyster conservation and restoration. Structural metrics of oyster reefs were compared from surveys using unoccupied aircraft systems, UAS or drones and ground‐based LiDAR. Three‐dimensional point clouds generated from UAS surveys were denser and more uniform across the oyster reefs, appearing to capture greater structural variability than the ground‐based LiDAR.
... Oyster reef-based living shorelines are becoming increasingly popular because they can provide both wave attenuation and suitable habitats for oysters, fish, and other species (Rodriguez et al., 2014;Morris et al., 2019;Wang et al., 2021). They can artificially be built by stacking concrete blocks and letting the oysters grow on these blocks (Theuerkauf et al., 2015;Wang et al., 2021). ...
... This alternative COR base is completely within the OGZ. According to Rodriguez et al. (2014), this alternative COR base would be an ideal location for the larval settlement and will allow the oysters to grow and flourish by itself. This COR base is designed to imitate the low-lying wide natural reefs. ...
... The water level and the new COR segment's height and width increase each year in 100 years in the new bathymetry configuration. It is believed that the proposed oyster reef configuration would grow fast with a vertical growth rate of 9 cm/year in the initial year of construction and would reach the MSL in about 8 years (Rodriguez et al., 2014). Then, COR would vertically grow at the rate of the SLR (Rodriguez et al., 2014). ...
Article
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In densely populated coastal areas with sea-level rise (SLR), protecting the shorelines against erosion due to the wave impact is crucial. Along with many engineered structures like seawalls and breakwaters, there are also green structures like constructed oyster reefs (CORs) that can not only attenuate the incident waves but also grow and maintain pace with SLR. However, there is a lack of data and understanding of the long-term wave attenuation capacity of the living shoreline structures under SLR. In this study, we used the phase-resolving Boussinesq model, FUNWAVE-TVD, to examine the hydrodynamics including wave height and wave-induced currents around the CORs in the Gandys Beach living shoreline project area in the upper Delaware Bay, United States. Waves were measured at six locations (offshore to onshore, with and without CORs) in the Gandys Beach living shoreline project area for two winter months, during which four nor’easters occurred. We selected three cases that represent prevailing wind, wave, and tide conditions to examine the fine spatial and temporal changes in wave height and current velocity by the construction of the reefs. Wave heights and wave energy spectra generated from FUNWAVE-TVD were then validated with field observations. It is found that FUNWAVE-TVD is capable of simulating waves and associated hydrodynamic processes that interact with CORs. The model results show that wave attenuation rates vary with the incident wave properties and water depth, and wave-induced circulation patterns are affected by the CORs. The wave attenuation capacity of CORs over the next 100 years was simulated with the incorporation of the oyster reef optimal growth zone. Our study found that sustainable wave attenuation capacity can only be achieved when suitable habitat for COR is provided, thus it can vertically grow with SLR. Suitable habitat includes optimal intertidal inundation duration, current velocity for larval transport and settlement, on-reef oyster survival and growth, and other environmental conditions including salinity, temperature, and nutrient availability. Furthermore, the model results suggest that it would take CORs approximately 9 years after construction to reach and maintain the maximum wave attenuation capacity in sustainable living shorelines.
... However, vertical growth is limited by the aerial exposure time at low tides as upper threshold. Rodriguez et al. (2014) and Ridge et al. (2017) found a threshold of a growth ceiling of 50-60% of the time during a tidal cycle. Several studies suggest classifications of oyster reefs in two or three reef types [e.g., highrelief or low-relief (Schulte et al., 2009;Lipcius et al., 2015); high reef density or low reef density (Mann et al., 2009;Wagner et al., 2012); high or low complexity (Grabowski, 2004;Grabowski and Powers, 2004;Markert, 2020)]. ...
... A comprehensive analysis of oyster-settled surfaces in the shallow marine environment using high-resolution DEMs has not yet been conducted to date. It is worth mentioning that DEMs of natural and constructed C. virginica reefs were analyzed by Rodriguez et al. (2014) and Ridge et al. (2015) to investigate vertical, areal, and hence volumetric reef growth, over time as well as impact factors such as aerial exposure time and sea-level rise. Parameters describing the roughness of the reef, e.g., topographical roughness lengths, have not been identified in these studies. ...
... The differences in position and elevation further confirm the similarity between structural classes and growth stages. Transitional Zone and Central Reef are located toward the center of the reef with elevations corresponding to the aerial exposure times during a tidal cycle of 50-60%, which is the vertical growth threshold reported by Rodriguez et al. (2014) and Ridge et al. (2017). Further, Cluster, Patches, and Garlands are located at the margins of the reef at lower elevations, where the oyster coverage keeps expanding horizontally and vertically. ...
Article
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The Pacific oyster ( Magallana gigas ) is an invasive species in the Wadden Sea transforming parts of it permanently. M. gigas , as an ecosystem engineer, builds reef structures that are characterized by highly complex and variable surfaces consisting of densely packed, sharp-edged individuals connected with cement-like bonds. To investigate the interactions between reef structure, shape and formation and wave as well as tidal currents, an understanding of the surface roughness is essential. This work reports on observations of oyster reefs for which seven new structural classes ( Central Reef , Transitional Zone , Cluster I , Cluster II , Patch I , Patch II , and Garland ) are proposed. For each class, high resolution Digital Elevation Models (DEMs) have been elaborated based on Structure-from-Motion (SfM) photogrammetry and analyzed using spatial statistics. By determining probability density functions (PDFs), vertical porosity distributions, abundances, orientations and second-order structure functions (SSFs), topographical parameters that influence the hydraulic bed roughness have been determined. The results suggest, that by applying the structural classification and their distinct topographical roughness parameters, the oyster reef surfaces can be described appropriately accounting for their complexity. The roughness accounts to a total roughness height k t = 103 ± 15 mm and root-mean-square roughness height k rms = 23 ± 5 mm. These values were found similar across all structural classes, yet the shape of the PDFs reveal differences. With decreasing abundance, the distributions become more positively skewed and are characterized by more extreme outliers. This is reflected in the higher statistical moments, as the skewness ranges between Sk = 0.4–2.1 and the kurtosis between Ku = 2.2–11.5. The analysis of the orientations and the SSFs confirms anisotropic behavior across all structural classes. Further, the SSFs reveal the oyster shells as significant roughness elements with exception of Cluster I and II , where the clusters are identified as significant roughness elements. The provided set of topographical roughness parameters enhances the knowledge of oyster reef surfaces and gives insights into the interactions between biogenic structure and surrounding hydrodynamics. The new intra-reef classification allows for more accurate determination of the overall roughness as well as the population dynamics of the habitat forming oyster. Combined with hydraulic measurements, the results can be used to estimate the hydraulic bed roughness induced by the oyster reef surfaces.
... The fact that oysters, and the reefs they create are generally resilient to major storm events (Arkema et al., 2013;Livingston et al., 1999;Walters et al., 2007), and that reefs can grow vertically thus keeping pace with SLR, makes them ideal for nature-based coastal defence (Ridge et al., 2015;Rodriguez et al., 2014;Walles et al., 2015aWalles et al., , 2015b. Moreover, oysters have the ability to adapt to varying environmental conditions by regulating their physiological activity, and building their own hard substrate, and thus are able to be self-sustaining, even under stressful (i.e. ...
... Better understanding of possible thresholds under which sediment deposition or erosion occur, along with the impacts of sediment type on these processes, would help better identify the range of sedimentary and hydrodynamic environments in which these eco-engineered reefs would be most effective. Reef burial by sediment at the reef margins due to high suspended sediment loads in the water column can cause failure of eco-engineered oyster reefs efforts (ECOBAS, 2014;Powers et al., 2009;Rodriguez et al., 2014). Increasing reef substrate heights while ensuring adequate inundation of the oysters themselves can help minimize these impacts (Colden et al., 2017;Jordan-Cooley et al., 2011;Schulte et al., 2009). ...
... La Peyre et al. (2013) found that oyster recruitment onto deployed ReefBLKs™ (see Fig. 2d) in Louisiana, U.S. was not similar at all sites, with one in three sites having little or no recruitment. Thus, selection of appropriate sites and substrates is crucial (Baggett et al., 2014;Brumbaugh and Coen, 2009;Coen and Humphries, 2017;Coen and Grizzle, 2007;Coen and Luckenbach, 2000;NRC, 2017;Powers et al., 2009;Rodriguez et al., 2014;Schulte et al., 2009). In this aspect, Habitat Suitability Indices (HSI) (Chowdhury et al., 2019b;Pollack et al., 2012;Theuerkauf and Lipcius, 2016) and/or use of similar types of oyster models (Zu Ermgassen et al., 2016a can be effective tools aiding an initial first approximation for identifying potential sites for reef construction. ...
Article
Coastal areas are especially vulnerable to habitat loss, sea-level rise, and other climate change effects. Oyster-dominated eco-engineered reefs have been promoted as integral components of engineered habitats enhancing coastal resilience through provision of numerous ecological, morphological, and socio-economic services. However, the assessed ‘success’ of these eco-engineered oyster reefs remains variable across projects and locations, with their general efficacy in promoting coastal resilience, along with related services, often mixed at best. Understanding factors influencing the success of these eco-engineered habitats as valuable coastal management tools could greatly inform related future efforts. Here, we review past studies incorporating reef-building oysters for coastal resilience and enhanced ecosystem services. Our aims are to better understand their utility and limitations, along with critical knowledge gaps to better advance future applicability. Success depends largely on site selection, informed by physical, chemical and biological factors, and adjacent habitats and bottom types. Better understanding of oyster metapopulation dynamics, tolerance and adaptation to changing conditions, and interactions with adjacent habitats will help to better identify suitable locations, and design more effective eco-engineered reefs. These eco-engineered reefs provide a useful tool to assist in developing coastal resilience in the face of climate change and sea level rise.
... Model simulations often posit reef-accretion rates that are lower than SLR, but these rates have not been verified with direct measures of growth and are estimated using bathymetry and radiocarbon dating. A recent study using direct measurements from intertidal reef cores and lidarderived digital-elevation models concluded that vertical growth is fastest in underwater portions of the reef and slower at the reef crest (Rodriguez et al. 2014). Vertical growth of the whole reef is an order of magnitude faster than previously reported and can keep pace with predicted rates of SLR (Rodriguez et al. 2014). ...
... A recent study using direct measurements from intertidal reef cores and lidarderived digital-elevation models concluded that vertical growth is fastest in underwater portions of the reef and slower at the reef crest (Rodriguez et al. 2014). Vertical growth of the whole reef is an order of magnitude faster than previously reported and can keep pace with predicted rates of SLR (Rodriguez et al. 2014). Although the vertical growth rate of intertidal reefs is faster than subtidal reefs (Bishop and Peterson 2006), the effect of spatial aggregation of reef systems is unclear. ...
Technical Report
Full-text available
Oyster Reef Connectivity: Ecological Benefits and Associated Vulnerabilities
... Each experimental reef contained approximately 750 gallons (2836 L,~60 bushels) of oyster shell and was 5 m long  3 m wide  0.3 m tall in total size. Restored reefs extended almost completely out of the water at low tide,~0.1 m above the mean low tide, which is within the optimal growth zone for intertidal oyster reefs (Rodriguez et al., 2014). Reefs were positioned in each of the three intertidal landscapes (the spatial configurations of seagrass, salt marsh, and mudflat habitats) where intertidal reefs are commonly found in the South Atlantic Bight (Bahr & Lanier, 1981): on the fringes of salt marshes and bordered by seagrass beds on the opposite side (referred to throughout as the "seagrass landscape"); on the sandy points that extend outward from salt marshes not near seagrass habitat ("salt marsh landscape"); and on tidal flats isolated from vegetated habitat ("mudflat landscape"). ...
... However, Ziegler et al. (2018) revisited these reefs in 2010 and found that the mudflat 1997 reef augmentation of juvenile fish relative to controls was less than directly after reef restoration. This finding occurred perhaps because the reefs had continued to grow upward (Rodriguez et al., 2014), thereby leaving less vertical space above the reef during flood tide for juvenile fish. This difference could also be a function of Ziegler et al. (2018) sampling juvenile fishes at night, whereas Grabowski et al. (2005) analyzed catches during the day when they were highest. ...
Article
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Coastal marine habitats continue to be degraded, thereby compelling large‐scale restoration in many parts of the world. Whether restored habitats function similarly to natural habitats and fully recover lost ecosystem services is unclear. In estuaries, oyster reefs have been degraded by multiple anthropogenic activities including destructive fishing practices and reduced water quality, motivating restoration to maintain oyster fisheries and other ecosystem services, often at relatively high cost. We compared fish and invertebrate communities on recently restored (0–1 year post‐restoration), older restored (3–4 years post‐restoration), and natural oyster reefs to determine if and when restored reefs support functionally similar faunal communities. To test the influence of landscape setting on the faunal communities, the restored and natural reefs, as well as a control without reef present, were distributed among three landscapes (on the edge of salt marsh away from seagrass [salt marsh landscape], on mudflats [mudflat landscape], and near to seagrass and salt marsh [seagrass landscape]). Oyster density and biomass were greatest on restored reef habitat, as were those of non‐oyster bivalve species. Total abundance of invertebrates was much greater on oyster reefs than in control plots, regardless of reef or landscape type, yet were frequently highest on older restored reefs. Meanwhile, juvenile fish densities were greatest on natural reefs, at intermediate densities on older restored reefs, and least abundant on controls. When comparing the effects of reef age and landscape setting, juvenile fish densities were greatest on younger reefs within the mudflat landscape. Collectively, these results indicate that oyster reefs harbor higher densities of resident invertebrate prey, which may explain why reef habitat is also important for juvenile fish. Laboratory and field experiments supported the notion that gag grouper (a predatory demersal fish) forage more effectively on oyster reefs than on unstructured mud bottom, whereas our experiments suggest that flounders that utilize oyster reefs likely forage on adjacent mud bottom. Because landscape setting influenced fish and invertebrate communities on restored reefs, the ecological consequences of landscape setting should be incorporated into restoration decision making and site selection to enhance the recovery of ecosystem goods and services.
... A growing number of studies show successful examples of oyster and coral reef restoration Young, Schopmeyer, and Lirman 2012;. Oyster reefs have the potential to keep pace with present rates of sea-level rise (Rodriguez et al. 2014), and some corals have been observed to thrive in extreme conditions (e.g., extreme temperatures [Palumbi et al. 2014;Dandan et al. 2015]) and low pH waters (Shamberger et al. 2014). These observations provide hope that corals in some locations may have some capacity to adapt to certain future environmental changes when adequately managed. ...
... In contrast to engineered coastal structures, natural and artificial reefs can be self-sustaining ecosystems, meaning that healthy reefs can, in many cases, continue to grow and maintain a structure that can protect shorelines without human intervention (as observed in using a coastline stability model). For example, research indicates that the vertical growth rates of unharvested oyster reefs are faster than predicted rates of sea-level rise (Rodriguez et al. 2014), meaning that they could maintain their coastal protection benefits in the face of climate change and adapt to sea-level rise in contrast to conventional engineering structures . However, reef degradation may reduce their ability to keep up with sea-level rise (Perry et al. 2018); for example, for coral reefs to maintain their coastal protection benefits, they must continue to accrete calcium carbonate structures by maintaining the health of calcifying reef organisms that build reefs. ...
Chapter
Islands in estuaries, major river deltas, and open-coast environments reduce the severity of hazards, including erosion and flooding from wind-driven waves and extreme water levels, on the nearby habitats and shorelines. Islands may also provide critical ecosystem function for threatened and endangered species and migratory birds while providing access to recreational opportunities and navigation co-benefits. This chapter (Chapter 11) of the International Guidelines on Natural and Nature-Based Features (NNBF) for Flood Risk Management focusses on islands as NNBFs that support coastal resilience. Three types of islands are discussed—barrier islands, deltaic islands (including spits), and in-bay or in-lake islands. These islands may be new construction or, as in most cases, the restoration of island remnants. The degradation and loss of islands through combined processes such as sea-level rise, subsidence, and inadequate sediment input (e.g., upstream impoundments, navigation channels, evolving natural processes) are reducing the coastal resilience benefits of these features.
... Reef thickness is a metric used on low-relief intertidal oyster reefs in Mosquito Lagoon to track fine-scale, vertical accretion above the sediment over time (Chambers et al. 2017), with the expectation that reefs will continue to increase in height via oyster growth and recruitment until they reach the maximum for growth enabled by the local tidal range (Rodriguez et al. 2014). On each of ten haphazardly selected quadrats per reef, the height of five haphazardly selected points was recorded with a metal rod (rod diameter: 1 mm) and ruler and then averaged. ...
... Reef thickness, however, should have increased throughout the 13 years of monitoring to track Mosquito Lagoon sea level rise of 2 cm/yr (Rodriguez et al. 2014, IRL NEP 2020, but on our reefs thickness only increased from 2010 -2016, with a large decline in 2017 that remained unchanged through 2020. The reduction in the thickness of reefs after 2016 was likely the result of boring sponge infections facilitating breakage of the tallest clusters, but not oyster density. ...
Article
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In Mosquito Lagoon, Florida, there has been a 24% loss of intertidal oyster (Crassostrea virginica) habitat since 1943; many live reefs have been replaced by steep piles of disarticulated shell. To understand the relationship between boating and reef loss, we determined boating intensity and numbers of boat wakes contacting reefs. We then asked if oyster restoration could be successfully undertaken in areas where disarticulated shell had accumulated. We documented 1290 boats passing near Mosquito Lagoon reefs, with 0-51.4 boats producing wakes each hour. Maximizing boating distances to limit wakes would help protect oyster reefs. Community-based restoration began in 2007 and was tracked through 2020. Restoration footprint (density, shell height, profile, thickness, bridges) and off-footprint (density, seagrass) data documented success, suggesting that stabilizing oyster shell was all that was needed in the region. These results provide guidance for boating management and future oyster restoration efforts in microtidal estuaries.
... In addition, CGI has the ability to self-maintain (Gedan et al., 2011), and possesses the potential to self-repair after major storm events (Ferrario et al., 2014;Spalding et al., 2014). Furthermore, when it comes to SLR, some types of CGI such as oyster reefs are able to grow and keep pace with rising sea levels (Rodriguez et al., 2014). In some cases, CGI can perform similar functions to that of grey infrastructure, but will generally be cheaper to build and maintain (Sutton-Grier et al., 2015). ...
Preprint
With the undoubted acceleration of climate change impacts in recent times, climate change adaptation is no longer a matter of choice for numerous communities, especially those located on low-lying coastal areas such as those on small island developing states (SIDS). As the potential for rise in sea level and storm surges, there has been increased interest in coastal green infrastructure (CGI) in aiding with climate change adaptation strategies and protection of critical coastal infrastructure (CCI). This is because of CGI's role in flood and erosion protection, as well as the numerous environmental, social and economic benefits that they bring to areas they are implemented in. However, unlike typical hard engineering strategies that have clearly defined approaches and implementation methods, CGI is considered a rather novel approach to improving coastal resilience with varying systems being trialled around the world. From literature searches, a knowledge gap was identified when it came to recommendations on potential CGI strategies tailored for island nations. This study aims to investigate the potential of various coastal green infrastructure strategies to support climate adaptation to sea-level rise and storm surges on small island developing states (SIDS) in order to improve their coastal infrastructure resilience. The study area chosen for the project is Mahé, the largest island of the Seychelles. From literature reviews, it was discovered that a couple of literary sources had produced insightful results on critical infrastructure exposure to sea-level rise and storm surges. However, these sources did not provide great detail on the types of CGI coastal adaptations strategies that could be adopted. Identifying this as a knowledge gap, this individual research project further attempt to provide CGI based climate adaptation solutions for Mahé island. This was done by carrying a thorough review of critical coastal infrastructure on Mahé, identifying any barriers to climate change adaptations, and conducting a spatial analysis of Mahé. Spatial analysis was done by utilising mapping data from previous research studies and available online mapping tools, in turn identifying potential locations of and types of CGI strategies that could be adopted by the Seychelles to enhance coastal infrastructure resilience of Mahé in the future.
... Such structures pose maintenance costs that are impractical and therefore there is a demand for low-cost, resilient and sustainable solutions (Morris et al., 2018). Various forms of ecosystems in coastal environments (Kirwan and Megonigal, 2013;Rodriguez et al., 2014) such as seagrass meadows, salt marshes, dunes, biogenic reefs, etc. have a high capacity to protect the coasts against flooding and eroding via hydrodynamic energy dissipation, owing to the characteristics of the submerged vegetation and its associated structural complexities (Temmerman et al., 2013;Hanley et al., 2014;Ondiviela et al., 2014;Boudouresque et al., 2021;Da Ros et al., 2021). Contrary to the "hard" engineering structures, nearshore vegetated ecosystems can amplify the soil elevation and soil vertical acceleration on account of biomass accumulation from below the ground and particle trapping via the water column (Duarte et al., 2013;Potouroglou et al., 2017). ...
Article
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Worldwide, climate change adaptation in coastal areas is a growing challenge. The most common solutions such as seawalls and breakwaters are expensive and often lead to unexpected disastrous effects on the neighboring unprotected areas. In recent years, this awareness has guided coastal managers to adopt alternative solutions with lower environmental impact to protect coastal areas, defined as Nature-Based Solutions (NBSs). NBS are quite popular around the world but are often analyzed and implemented individually at pilot sites. This contribution analyzes the effectiveness of two NBS to mitigate coastal impacts (coastal flooding and erosion) under three historical storms along the Emilia-Romagna coasts and the induced improvements due to their potential integration. Through numerical simulations with XBeach, this study demonstrated that the presence of seagrass meadows of Zostera marina produces an average attenuation of 32 % of the storm peak with a maximum attenuation of 89 % in incoming wave height. Seagrass also mitigates flooded areas and maximum inundation depths by 37 % and 58 % respectively. The artificial dune leads to higher mitigation in terms of inundation of the lagoon (up to 75 %), also avoiding any morphological variations behind it. Seagrass has also been shown to be able to reduce beach erosion volumes up to 55 %. The synergic effect of the two NBS improves the capacity to mitigate both inundation (with a benefit of up to 77 % for flooded area attenuation with respect to cases without any defenses) and coastal erosion. Results of the study suggest that the two NBS will work together to produce co-benefits in terms of preservation of their efficiency, development of habitats for organisms and vegetation species, and thereby offering an important social value in terms of possible tourism, recreation and research.
... Cross-Chapter Box NATURAL in Chapter 2). Successful nature-based adaptation draws from existing adaptation approaches (Borsje et al., 2011;Temmerman et al., 2013;Law et al., 2018;Reguero et al., 2018;Buotte et al., 2019) and is applied across ecological and human systems (high confidence) ( Through a capacity to evolve to keep pace with climate change, these approaches can impart self-sustaining and cost-efficient long-term protection in addition to serving as biodiverse, carbon sinks (Scyphers et al., 2011;Cheong et al., 2013;Temmerman et al., 2013;Rodriguez et al., 2014;Herr and Landis, 2016;Sasmito et al., 2016;Reguero et al., 2018). Nature-based adaptation is generally less expensive and strengthens over time, as compared with built infrastructure which erodes with time (medium confidence) (Narayan et al., 2016;Smith et al., 2017;Sutton-Grier et al., 2018). ...
Chapter
Since AR5, climate-change impacts have become more frequent, intense and have affected many millions of people from every region and sector across North America (Canada, USA and Mexico). Accelerating climate-change hazards pose significant risks to the well-being of North American populations and the natural, managed and human systems on which they depend (high confidence1). Addressing these risks has been made more urgent by delays due to misinformation about climate science that has sowed uncertainty and impeded recognition of risk (high confidence). {14.2, 14.3} Without limiting warming to 1.5°C, key risks to North America are expected to intensify rapidly by mid-century (high confidence). These risks will result in irreversible changes to ecosystems, mounting damages to infrastructure and housing, stress on economic sectors, disruption of livelihoods, and issues with mental and physical health, leisure and safety. Immediate, widespread and coordinated implementation of adaptation measures aimed at reducing risks and focused on equity have the greatest potential to maintain and improve the quality of life for North Americans, ensure sustainable livelihoods and protect the long-term biodiversity, and ecological and economic productivity, in North America (high confidence). Enhanced sharing of resources and tools for adaptation across economic, social, cultural and national entities enables more effective short- and long-term responses to climate change. {14.2, 14.4, 14.5, 14.6, 14.7}
... Advantages of natural protection structures include the ability to self-recover after storm events, the adaptive potential of these natural systems to build elevation in response to sea level rise (e.g. oysters: Rodriguez et al. 2014 or mangroves: Marx et al. 2020), and greater cost-efficiency (Alongi 2008;Narayan et al. 2016). Furthermore, these natural approaches come with a range of co-benefits or ecosystem services that maintain, restore or achieve additional societal, environmental, and economic objectives (Sutton-Grier et al. 2015;Powell et al. 2019). ...
Technical Report
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This report reviews large protective coastal infrastructure in intertidal and nearshore zones, including trained river entrances, armoured harbours, and groynes. This review finds support for a sustainable, more holistic concept of coastal management, where interdisciplinary groups (e.g. asset owners, engineers, scientists, stakeholders, and community groups) work together to ensure that coastal areas are safe for communities, without compromising social, cultural and environmental values. Case studies from New South Wales within Australia and around the world give examples of where coastal protection infrastructure has either been modified with ecological engineering techniques or adopted approaches to facilitate multiple uses and add social, cultural and economic value to maximise sustainable outcomes.
... Topographically complex coastal ecosystems that include dunes, saltmarshes, mangroves, seagrasses and shellfish and coral reefs provide natural coastal protection through wave attenuation, depth-induced wave breaking, and sediment stabilization (Duarte et al., 2013;Narayan et al., 2016;Walles et al., 2015b). These ecosystems can adapt to changes in climate by growing or accreting at the rate of sea level rise (Rodriguez et al., 2014;Sasmito et al., 2016;Walles et al., 2015a), and self-repair after storm events . Living shorelines can also provide multiple co-benefits such as supporting biodiversity and fisheries, water filtration, carbon sequestration, social amenity and cultural value (Guthrie et al., 2022;Moody et al., 2022;Smith et al., 2021;Tachas et al., 2021). ...
... The eastern oyster Crassostrea virginica Gmelin, 1791 creates structured habitat for decapod crustaceans, other reef-associated fauna, and mobile nekton within estuarine environments along the Atlantic coast of USA and the Gulf of Mexico (Posey et al., 1999;Tolley & Volety, 2005;Harding et al., 2012;Fodrie et al., 2015). Oyster reefs often vary in their physical attributes, such as tidal flux and reef height, type, and size (Soniat et al., 2004;Grabowski et al., 2005;Powers et al., 2009;Rodriguez et al., 2014;Byers et al., 2015;Hanke et al., 2017a) and these factors can differentially influence oyster recruitment success, growth, abundance, and population size structure (Lenihan et al., 1996;Lenihan, 1999;Grabowski et al., 2005;Baggett et al., 2015, Hanke et al., 2017a. These different oyster population characteristics can collectively increase the structural complexity within a reef through enhancement of oyster cluster formation with vertically oriented shell (culms) and additional interstitial space (Lenihan, 1999). ...
Article
Structurally complex biogenic habitats provide foraging grounds and predation refuges for a myriad of decapod crustaceans. Many of these habitats, such as reefs formed by the eastern oyster (Crassostrea virginica Gmelin, 1791), have been lost due to natural and anthropogenic reasons , leading to the construction of artificial reefs for habitat restoration. Previous studies have investigated the impacts of oyster reef restoration efforts on abundance patterns of decapod crustaceans, such as those of panopeid crabs, but largely ignored the influence of artificial, or created, habitat on other population characteristics such as reproductive output. We sampled five artificial reefs (constructed during 2014 or 2015) in Sweetwater Lake, Galveston Bay, Texas, USA in July-August 2016 to study the population characteristics of female panopeid mud crab Panopeus simpsoni Rathbun, 1930. We quantified carapace width, counted eggs and measured dry egg mass to estimate reproductive output and determine how reef-age treatment, live-oyster abundance, and live-oyster size predicted female P. simpsoni abundance and egg production. Oyster size varied significantly (P < 0.001) by age treatment, and oyster abundance and size varied significantly (P < 0.001) between the reefs within each age treatment. The abundance of female P. simpsoni varied significantly (P < 0.001) between the two age treatments and was positively correlated with oyster size and reef age. The percentage of gravid females, which varied significantly (P = 0.027) among the reefs, was positively correlated with oyster abundance, and egg production was positively correlated with body size. These results suggest that oyster development on artificial reefs may influence the abundance and reproductive output of associated crustaceans such as P. simpsoni. We demonstrate that monitoring programs should not only consider population characteristics of reef-building organisms, but also the development of complex habitat structure and its impact on associated crustacean populations when determining the success of artificial habitats.
... Vegetated ecosystems are able to enhance soil vertical accretion and soil elevation due to the accumulation of large belowground biomass and the trapping of particles from the water column (Duarte et al., 2013;Kirwan and Megonigal 2013;Potouroglou et al., 2017). Oyster reefs grow vertically through attracting oyster larvae that drift through the water and latch onto the existing wall, contributing to its growing (Rodriguez et al., 2014). In addition, coastal habitats provide multiple other ecosystem services relevant to coastal communities, such as fisheries support, biodiversity, water quality improvement, and recreational and cultural benefits . ...
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Momentum for sustainable and climate resilience solutions for coastal protection are growing globally given the pressing need to prevent further loss of biodiversity and ecosystems while meeting the climate change adaptation and mitigation goals. Nature-Based Solutions (NbS) represent an opportunity to align environmental and resilience goals, at a time of strained budgets in a global context and when short-term needs may run counter to long-term goals. In Europe, NbS fit the mandates of major EU environmental and climate change policies by restoring biodiversity and enhancing climate-resilience and carbon sequestration. Previous studies have compiled scientific evidence about hydro-meteorological hazards for the use of NbS. However, their implementation at scale is still lacking. As the knowledge and experience with NbS for adaptation to natural hazards and climate change increases, it becomes more important to draw lessons learned and insights for replicating and scaling up NbS, especially in coastal areas where their implementation is still limited compared to other environments. This study analyzed NbS case studies across European coastal and estuarine areas to draw key lessons, understand better the current status of implementation, and identify key challenges and gaps. From a total of 59 NbS case studies associated with flooding, erosion and biodiversity loss, results show an increase in NbS implementation since 1990s, but most rapidly between 2005 and 2015. Most of the case studies are hybrid solutions employing wetlands, predominantly located in the United Kingdom (UK) and the Netherlands. Funding of NbS is largely from public sources, and rarely come from a single or a private source. Three-quarters of the case studies reported monitoring activities, but more than half did not disclose quantitative results related to effectiveness against flooding and/or erosion. The need to improve coastal defenses was indicated as the main motivation for NbS implementation over traditional structures, while sustainability was the most mentioned additional reason. Although a variety of co-benefits and lessons learned was identified, clearer descriptions and enhanced details of such information are required. There is a need for tools and strategies to expand knowledge sharing of lessons learned to enable further replication of successful cases in other areas.
... For example, the reef-forming Pacific oyster (Magallana gigas) survives in both intertidal and subtidal environments (Diederich et al. 2005;Barrett et al. 2010). Shellfish reefs may also be resilient to SLR if their vertical growth rate is high enough to keep pace with rising water levels (Rodriguez et al. 2014). Other shellfish species that commonly occur in estuaries, like the cockle (Austrovenus stutchburyi) and the wedge shell (Macomona liliana), are largely restricted to intertidal areas (Ellis et al. 2006). ...
Article
Sea level rise (SLR) has been described as one of the greatest potential causes of ecosystem disruption, putting many coastal areas at risk of irreversible changes. However, the loss of intertidal areas from SLR and the associated ecological and social repercussions receive little attention. Within estuaries, extensive intertidal areas harbour a variety of habitats and communities and represent hotspots of ecosystem functions. Any changes to their distribution or extent are likely to have far reaching implications. Here we summarise the ecological consequences of a reduction in intertidal area from increasing SLR, and the implications for people, management and planning. To facilitate this discussion, changes in the occurrence and abundance of two ecologically and culturally important intertidal shellfish species (Austrovenus stutchburyi and Macomona liliana) were modelled under different SLR scenarios for Tauranga Harbour, Aotearoa New Zealand. We highlight how the squeezing of intertidal areas will likely alter the distribution and extent of key habitats and communities, and discuss the implications for coastal food webs, ecosystem functioning and service provision. Pre-emptive planning and adaptive management are needed that incorporate ecological losses in risk assessments and focuses on pro-active solutions to increase resilience to the effects of SLR.
... This requires some background knowledge of the features being mapped. In our example, intertidal oyster reefs can grow 10 to 13 cm yr −1 vertically [27], so one approach is to determine the required precision by dividing the minimum annual expected vertical change of 10 cm by two (10/2 = 5 cm). The required mean bias should be zero. ...
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Coastal environments are some of the most dynamic environments in the world. As they are constantly changing, so are the technologies and techniques we use to map and monitor them. The rapid advancement of sUAS-based remote sensing calls for rigorous field and processing workflows so that more reliable and consistent sUAS projects of coastal environments are carried out. Here, we synthesize the best practices to create sUAS photo-based surveying and processing workflows that can be used and modified by coastal scientists, depending on their project objective. While we aim to simplify the complexity of these workflows, we note that the nature of this work is a craft that carefully combines art, science, and technology. sUAS LiDAR is the next advancement in mapping and monitoring coastal environments. Therefore, future work should consider synthesizing best practices to develop rigorous field and data processing workflows used for sUAS LiDAR-based projects of coastal environments.
... Edge effects, and associated statistical noise in time series data, may have prevented the detection of clear restoration trends on reef margins. These edge effects, such as diminished oyster densities and prolonged tidal submergence, may influence macroinvertebrate assembly uniquely on reef margins 35,36 and thus lead to community-level differences between these two oyster reef zones. The effect of these environmental differences on oyster density have been documented 36 . ...
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Historic declines in oyster populations have resulted in diminished production of ecosystem services and habitat function in many estuaries. Due to the important role of oysters in ecosystem function, scientists and resource managers have employed oyster reef restoration to mitigate declines, recover essential ecosystem services, and better habitat function. Yet, there are knowledge gaps regarding the impact of restoration efforts on ecologically valuable mid-trophic level organisms inhabiting these systems. To address this knowledge gap, here we quantify macroinvertebrate species abundance, community diversity, and composition on experimental restored oyster reefs before and after restoration, and from live (positive control) and dead (negative control) reefs in the Indian River Lagoon, Florida. Species diversity and composition on restored reefs shifted towards states similar to live (positive control) reefs within 12 months of restoration. Recovery of species abundance occurred within 18 months of restoration. The results presented herein quantify the effect of restoration on resident macroinvertebrates and provide timelines of recovery for each attribute of these communities. Further, this study presents an actionable and transferable framework for identifying effective single-species metrics of restoration success across ecosystems. The application of this framework will provide managers and researchers with tools to improve the efficiency and efficacy of post-restoration monitoring. By doing so, this study contributes significantly to the improvement of broader restoration practices in an era of unprecedented habitat loss.
... The three-dimensional complexity of oyster reefs and mussel beds can reduce erosion by absorbing wave energy and trapping sediments (Bertness, 1984;Meyer et al., 1997;Piazza et al., 2005;Stricklin et al., 2009), and create or enhance habitat (Coen and Grizzle, 2007;Angelini et al., 2015;Isdell et al., 2018;Cole et al., 2022). Given these benefits and the capacity of oyster and mussel reefs to grow vertically with rising seas (Rodriguez et al., 2014;Ridge et al., 2017), there is increased interest in integrating shellfish into shoreline protection efforts (Mitsch, 2012;La Peyre et al., 2014) and quantifying the associated water quality benefits. ...
Article
Bivalve shellfish are common in coastal ecosystems where their aggregate structure attenuates wave energy and provides habitat, while delivering water quality benefits through their feeding activity. These factors make them appropriate candidates for inclusion in living shorelines to facilitate positive ecological outcomes. In 2014, a 61 m shellfish-based living shoreline was constructed along a salt marsh at the DuPont Nature Center in Milford, Delaware with the goal to maximize shellfish populations for water quality benefits. Monitoring was conducted to assess oyster and ribbed mussel population development and evaluate their relative contribution to cumulative filtration at three positions— on structures near mean low water (low), along the marsh edge (high), and on the untreated mudflat between (mid). Oyster and ribbed mussel counts and size demographics were converted to population and biomass densities to calculate filtration capacity in each position through 2020. Cumulatively, shellfish on the Mispillion living shoreline filtered 6763 kg of seston, but population and biomass development varied spatiotemporally between species. Between 2018 and 2020, oyster population and biomass densities declined at the low, but increased at the high positons, while ribbed mussel densities increased at both. Despite differences among species and position, the annual summed filtration of the low and high positions continually increased. These results indicate that a multi-species approach, across a variety of appropriate spatial niches, can help maintain or enhance overall filtration capacity through either complementary species contributions at a single positon, or spatial compensation by a single species across positons.
... An important component of these restoration activities involves the use of nature-based coastal defense composed of reefs created by the native eastern oyster (Crassostrea virginica, hereinafter "oyster"; CPRA, 2017; DWH NRDA, 2017). Eastern oysters are noted ecosystem engineers, and valued for coastal defense because they build and maintain their own habitat (reefs), and may grow vertically, thus potentially keeping pace with SLR (La Peyre et al., 2014;Rodriguez et al., 2014;Ridge et al., 2015). Further, fringing oyster reefs may support adjacent marsh stability through wave attenuation (Borjse et al., 2011;Walles et al., 2015a;Morris et al., 2018), and nutrient and sediment subsidies from oyster filtration and trapping and stabilization of sediments (Walles et al., 2015a;Chowdhury et al., 2019aChowdhury et al., , 2019b. ...
Article
Nature-based coastal defense using bivalve reefs provides a potentially self-sustaining approach for regions facing high coastal land loss, relative sea level rise and increasing frequency and intensity of storms. Success of such nature-based coastal defense depends on the reef-building species' life history, habitat requirements, and ability to thrive through short-term and longer-term environmental variation, yet few projects have reported on outcomes beyond the first few years. In coastal Louisiana, USA, Crassostrea virginica (oyster) is an ecosystem engineer, creating self-sustaining, vertically accreting reefs that also provide ecosystem services. Here, we examine the short (< 3 years) and medium (> 10 years) term outcomes of experimental reefs constructed in 2009 for nature-based coastal defense in a Louisiana, USA estuarine lake. Oyster reef density, demography, along with adjacent salt marsh, and shoreline movement were compared at six fringing shoreline reefs and paired reference sites over the first three years post-construction (2009–2011), and a decade later (2019–2020). Oyster density measured in 2019–2020 (< 60 ind m⁻²) was less than 10% of density measured during 2009–2011 (> 1000 ind m⁻²). This density difference largely reflected a lack of new recruits and small oysters (< 75 mm shell height) in later samples, with adult oyster densities similar between 2011, 2019 and 2020. Lack of smaller oysters in recent sampling likely reflected the impact of multiple extended low salinity events in this region in recent years, including the record-breaking low salinity in 2019. No differences in shoreline characteristics were detected in marsh vegetation, soil properties or nutrient concentrations between reef and reference sites during early and later years. Similarly, shoreline erosion at both reef and reference sites immediately post-construction, and 10 years later, was high (~1 m y⁻¹) indicating a lack of shoreline protection from these reefs. These findings highlight the need to consider both current and future conditions, including the effect of extreme years, when implementing nature-based coastal defense. On the other hand, the persistence of reproductive-sized oysters on the reef 10 years post creation, indicate reef resilience and potential for reef development and shoreline benefits, should better site conditions return in future years. Determining restoration success within variable and dynamic environments requires frequent monitoring which is required to understand responses to short and longer-term environmental variation.
... Various estuarine habitats including mangroves, seagrasses, saltmarshes, and oyster reefs increase the three-dimensional complexity of habitats and positively influence nearshore coastal ecosystem dynamics (Beck et al. 2001;Heck et al. 2003). Oyster reefs increase the dimensional complexity of nearshore sedimentary environments simply through recruitment, growth, and aggregation of individual oysters (Rodriguez et al. 2014;Ridge et al. 2017). Distinct from plant-based estuarine habitats, natural oyster reefs consist of rigid live and dead, attached and unattached calcium carbonate shells. ...
Article
Established, natural oyster reefs historically provide a three-dimensionally complex habitat utilized by a variety of resident and transient species, but newly created reefs designed to counter the loss of natural reefs initially may lack similar complexity. The loosely stacked shells of newly created reefs little resemble the vertically interconnected live and dead shell matrix typical of older reefs. Reduced complexity on created reefs may alter predator-prey dynamics and negatively affect ecological functions typically associated with natural reefs. We examined select physical characteristics (e.g., shell morphology) and short-term survival of reef-resident prey to determine if differences exist between newly created (<1 year old shell bags) and established natural intertidal reefs in South Carolina. Shell physical characteristics differed consistently between reefs, with greater numbers of smaller and lighter shells found on natural reefs. However, short-term survival of crabs (Panopeid sp.) and mussels (Geukensia demissa) generally was not dependent on reef type. The few instances of reef dependent prey survival were either inconsistent with expected results, assuming reduced complexity on created reefs, or not supported by effect size analyses. Evidence indicates that adding shell bags to create oyster reefs in intertidal environments almost immediately increases resident species survival similar to that on existing natural reefs and leads to the rapid return of a major ecosystem service associated with coastal oyster reefs. This article is protected by copyright. All rights reserved.
... The advantages of natural protective structures include the ability to self-recover after storm events, the adaptive potential of these natural systems to build elevation in response to sea-level rise (Rodriguez et al., 2014;Rogers et al., 2019, Marx et al., 2020, and greater cost-efficiency (Alongi, 2008;Narayan et al., 2016). Furthermore, these natural approaches come with a range of co-benefits (i.e., ecosystem services) that maintain, restore or achieve additional societal, environmental, and economic objectives (Sutton-Grier et al., 2015;Powell et al., 2018;Jones et al., 2020). ...
Article
Hard coastal protective infrastructure, such as breakwaters, are a common adaptation strategy to protect assets, increase safety and improve navigation by reducing erosion and flood risks along coastlines globally. However, protective structures can have pervasive impacts on use patterns, aesthetics and associated ecosystems, threatening ecosystem goods and services upon which humans depend. Guided by a recent Australian state Government strategy that aims to plan for “a healthy coast and sea managed for the greatest wellbeing of the community, now and into the future”, we present a decision-making support tool for practitioners to help achieve more sustainable solutions to coastal adaptation into the future. Sustainable coastal adaptation needs to consider the environmental and socio-economic consequences of hard protective infrastructure, as well as the increased vulnerability due to rising sea levels. To demonstrate our arguments, we introduce three different coastal scenarios. We also discuss alternatives to coastal protection and make scenario-specific recommendations to enhance environmental and socio-economic outcomes of coastal adaptation. In general, the implementation of hard protective infrastructure should probably be a last resort after retreat and soft approaches have been ruled out as viable options. Where protective infrastructure is the current best option, environmental and socio-economic outcomes can be enhanced using eco-engineering and multi-use features. In the long term, however, retreat from some coastal areas may be necessary and existing infrastructure might be removed or abandoned.
... Further, our results indicate a trajectory of increasing oyster densities associated with OC reefs, which will hopefully translate into increased structural footprint, and therefore protective efficacy, in coming years (sensu Morris et al. 2019a). Given the structural integrity of these reefs and recent findings that natural fringing reefs in the same system are growing at a rate exceeding local sea-level rise (Rodriguez et al. 2014), it is not unreasonable to expect that OC reef growth will continue. ...
Article
The detrimental ecological impacts of engineered shoreline protection methods (e.g. seawalls) and the need to protect the coastal zone have prompted calls for greater use of natural and nature‐based infrastructure (NNBI). To balance competing needs of structural stability and ecological functioning, managers require assessments of NNBI designs and materials for differing environmental settings (e.g., among wave‐energy regimes). To examine the effects of setting and oyster‐based NNBI design on the provision of shoreline protection, we constructed reefs from two substrates: a novel, biodegradable material (Oyster Catcher™, OC) and traditional oyster shell bags (SB) on low‐ and high‐energy eroding salt marsh shorelines, designated based on fetch and boat wake exposure. Both reef types buffered marsh elevation change on the high‐energy shoreline relative to unaltered controls, but only SB reefs were able to do so on the low‐energy shoreline. Additionally, both shorelines experienced high ambient rates of retreat and declines in marsh vegetation shoot density. Although constructed reefs did not mitigate marsh retreat on the low‐energy shoreline, novel OC reefs significantly reduced retreat relative to SB reefs and control sites (no reefs) on the high‐energy shoreline. Those SB reefs were severely damaged by storm events, increasing their areal footprints at the expense of vertical relief. Conversely, OC reefs on both shorelines exhibited steady oyster recruitment and growth and hosted higher densities of larger oysters. To successfully provide shoreline stabilization benefits, oyster‐based NNBI must be structurally stable and able to promote sustained oyster recruitment and growth. Our results indicate that deliberate decisions regarding NNBI substrate, siting, and configuration can produce resilient reefs, which reduce rates of erosion and, in some cases, enhance vertical accretion along salt marsh edges. The growth trajectory, structural stability, and co‐benefit provisioning of OC reefs demonstrate the potential of alternative restoration substrates to provide valuable oyster habitat along threatened marsh shorelines.
... Another important aspect to consider to improve the living shoreline configuration and make it more natural, while maintaining its efficiency, is the possibility of replacing the break walls constituting the rip-raps with oyster reefs. The advantage of integrating in-water infrastructure with oysters is that these reefs have the ability to grow with SLR (Rodriguez et al., 2014;Ridge et al., 2017), providing greater guarantees in terms of coastal protection even after the gray structure may become ineffective. ...
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Rising sea levels and the increased frequency of extreme events put coastal communities at serious risk. In response, shoreline armoring for stabilization has been widespread. However, this solution does not take the ecological aspects of the coasts into account. The "living shoreline" technique includes coastal ecology by incorporating natural habitat features, such as saltmarshes, into shoreline stabilization. However, the impacts of living shorelines on adjacent benthic communities, such as submersed aquatic vegetation (SAV), are not yet clear. In particular, while both marshes and SAV trap the sediment necessary for their resilience to environmental change, the synergies between the communities are not well-understood. To help quantify the ecological and protective (shoreline stabilization) aspects of living shorelines, we presented modeling results using the Delft3D-SWAN system on sediment transport between the created saltmarshes of the living shorelines and adjacent SAV in a subestuary of Chesapeake Bay. We used a double numerical approach to primarily validate deposition measurements made in the field and to further quantify the sediment balance between the two vegetation communities using an idealized model. This model used the same numerical domain with different wave heights, periods, and basin slopes and includes the presence of rip-rap, which is often used together with marsh plantings in living shorelines, to look at the influences of artificial structures on the sediment exchange between the plant communities. The results of this study indicated lower shear stress, lower erosion rates, and higher deposition rates within the SAV bed compared with the scenario with the marsh only, which helped stabilize bottom sediments by making the sediment balance positive in case of moderate wave climate (deposition within the two vegetations higher than the sediment loss). The presence of rip-rap resulted in a positive sediment balance, especially in the case of extreme events, where sediment balance was magnified. Overall, this study concluded that SAV helps stabilize bed level and shoreline, and rip-rap works better with extreme conditions, demonstrating how the right combination of natural and built solutions can work well in terms of ecology and coastal protection.
... A variety of associated industries, such as gear manufacturers and food-based tourism, are also predicated on healthy and marketable oysters. In addition, oyster reef restoration has become a priority for protecting developed areas along the Atlantic coast (Rodriguez et al., 2014). This is especially true in urban areas that have witnessed the rise of extreme storms like Sandy (2012) and Florence (2018) (Steiner, Simmons, Gallagher, Ranganathan, & Robertson, 2013). ...
Article
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Nature provides numerous ecosystem services to people, yet the prioritization of these services often depends on the goals of various stakeholder groups. The eastern oyster (Crassostrea virginica) is an ecologically important species along the Gulf and Atlantic coasts of the United States, where it provides essential fish habitat and may mitigate against climatic variations in urban areas. The eastern oyster also supports a multimillion dollar aquaculture industry in coastal communities. Recent declines in eastern oyster populations, however, have spurred widespread restoration activities. Here, we look at three expert stakeholder groups (academics, nongovernmental organizations, and governmental agencies) in Rhode Island (United States) to understand how stakeholder perceptions of oyster ecosystem services differ. Stakeholders' mental models showed differences among the groups' topologies and components, although the terms “Water Quality” and “Habitat/Structural Complexity” were prioritized in all the groups. Our results suggest that there is substantial intergroup variation, but that there are common threads around which future oyster restoration and management programs can be designed. By making these mental models of ecosystem services explicit, we illuminate tacit assumptions held by different stakeholders of the oyster stakeholder community in Rhode Island. In doing so, we highlight opportunities for more efficient collaboration around commonly shared goals for sustainable social and ecological management.
... However, reef crests that spend a greater proportion of their time exposed, while maximizing wave attenuation are not suitable habitat for oysters. Oyster reefs have the benefit over artificial structures in that they can vertically accrete, such that whereas revetments may be over-topped under scenarios of sea-level rise, oyster reefs can potentially keep pace (Grabowski et al., 2012;Rodriguez et al., 2014), serving as natural protection against intertidal habitat loss, shoreline erosion, and property damage (Syvitski et al., 2009;Lin et al., 2012;Temmerman et al., 2013). ...
Article
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Globally, there is growing interest in restoring previously widespread oyster reefs to reinstate key ecosystem services such as shoreline protection, fisheries productivity and water filtration. Yet, since peak expiration of oysters in the 1800s, significant and ongoing environmental change has occurred. Estuaries and coasts are undergoing some of the highest rates of urbanization, warming and ocean acidification on the planet, necessitating novel approaches to restoration. Here, we review key design considerations for oyster reef restoration projects that maximize the probability that they will meet biological and socio-economic goals not only under present-day conditions, but into the future. This includes selection of sites, and where required, substrates and oyster species and genotypes for seeding, not only on the basis of their present and future suitability in supporting oyster survival, growth and reproduction, but also based on their match to specific goals of ecosystem service delivery. Based on this review, we provide a road map of design considerations to maximize the success of future restoration projects.
... For instance, in Papua New Guinea, bright red isopods survive in conspicuous groups on surfaces of reef exposure to fish predators (Rodriguez et al. 2014). The cyano-bacteria casing their carapace have red shadow, and fish decline them as foodstuff. ...
... For instance, in Papua New Guinea, bright red isopods survive in conspicuous groups on surfaces of reef exposure to fish predators (Rodriguez et al. 2014). The cyano-bacteria casing their carapace have red shadow, and fish decline them as foodstuff. ...
... For instance, in Papua New Guinea, bright red isopods survive in conspicuous groups on surfaces of reef exposure to fish predators (Rodriguez et al. 2014). The cyano-bacteria casing their carapace have red shadow, and fish decline them as foodstuff. ...
... In a high energy environment, where boat wake or wave energy is high, plastic mesh oyster bags may not be an effective way to build sustainable constructed oyster reefs (Chowdhury et al. 2019). Rodriguez et al. (2014) showed that oysters in newly established reefs can grow at an astonishing 11.5 cm/yr, but that reef height, in turn, becomes constrained by sea level in mature reefs. Therefore, in some sense, the carbon and sediment trapping potential of reefs seems limited. ...
... Unlike static structures, the vertical reef building capacity of oysters makes them a candidate for creating dynamic structures (Mitchell and Bilkovic 2019). Oyster reefs exhibit a natural resilience and adaptive capacity to recover quickly from major storm events (Livingston et al. 1999) and are capable of accreting at a rate necessary to maintain elevation in areas facing sea-level rise (Rodriguez et al. 2014) or local subsidence (Casas et al. 2015). A key variable that affects the recruitment, survival, and growth of oyster reefs is the duration of inundation (Table 1), which is a function of the absolute elevation of the reef and the tidal range. ...
Article
One of the paramount goals of oyster reef living shorelines is to achieve sustained and adaptive coastal protection, which requires meeting ecological (i.e., develop a self‐sustaining oyster population) and engineering (i.e., provide coastal defense) targets. In a large‐scale comparison along the Atlantic and Gulf coasts of the United States, the efficacy of various designs of oyster reef living shorelines at providing wave attenuation was evaluated accounting for the ecological limitations of oysters with regards to inundation duration. A critical threshold for intertidal oyster reef establishment is 50% inundation duration. Living shorelines that spent less than half of the time (< 50%) inundated were not considered suitable habitat for oysters, however, were effective at wave attenuation (68% reduction in wave height). Reefs that experienced > 50% inundation were considered suitable habitat for oysters, but wave attenuation was similar to controls (no reef; ~5% reduction in wave height). Many of the oyster reef living shoreline approaches therefore failed to optimize the ecological and engineering goals. In both inundation regimes, wave transmission decreased with an increasing freeboard (difference between reef crest elevation and water level), supporting its importance in the wave attenuation capacity of oyster reef living shorelines. However, given that the reef crest elevation (and thus freeboard) should be determined by the inundation duration requirements of oysters, research needs to be re‐focused on understanding the implications of other reef parameters (e.g. width) for optimising wave attenuation. A broader understanding of the reef characteristics and seascape contexts that result in effective coastal defense by oyster reefs is needed to inform appropriate design and implementation of oyster‐based living shorelines globally.
... This ability to adapt to changing environmental drivers can be beneficial. NBS are capable of adjusting their position in the tidal frame in response to changes in sea-level rise and can self-repair after storms Rodriguez et al., 2014), whereas man-made structures can be rendered obsolete by changes in environmental conditions (Hinkel et al., 2014) and can require expensive repairs when storm related-damages are sustained. Despite the benefits of adaptability, the dynamic nature of NBS leads to uncertainty regarding how a given feature will perform. ...
Article
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The use of natural habitats for coastal protection (a.k.a. Nature Based Solutions or NBS) in place of engineered structures like breakwaters and seawalls can yield a wide range of ecological and economic benefits. Despite these advantages, NBS are not commonly implemented for shoreline protection due to uncertainty over the amount of protection afforded by each unique feature and how protective capacity and ecological benefits are likely to change over time as NBS mature and adapt to changing environmental drivers. Here we highlight the recent restoration of Swan Island in the Chesapeake Bay, and the collaborative approach used to evaluate post‐construction performance, as a framework for quantitative evaluation of NBS projects. At Swan Island, 60,000 cubic yards of dredged sediment were used to elevate and restore the island's footprint with an emphasis on increasing its protective and ecological benefits and long‐term resilience to sea level rise. Five entities have leveraged resources to quantify the benefits and efficacy of island restoration by conducting pre‐ and post‐restoration monitoring which supports development of an integrated, simulation model that includes three 'measured' system parameters: wave height, vegetation biomass and island profiles (i.e., elevations). The model will be used to predict island performance under a range of different system scenarios and used to inform adaptive management options. Results will demonstrate the efficacy of leveraging natural and engineered processes to restore island systems while providing a framework for quantifying NBS. This article is protected by copyright. All rights reserved.
... Reef building bivalves are regarded as ecosystem engineering organisms, in that they build structures that alter their physical environment. In terms of their utility for coastal protection, the rough vertical structure of bivalve reefs acts as a natural, rejuvenating break-water with potentially cost-saving characteristics due to its low maintenance requirements, ability to expand laterally over time and grow vertically alongside changing sea levels (Scyphers et al., 2011;Rodriguez et al., 2014;Walles et al., 2015b). However, a major weakness of pursuing nature-based coastal protection schemes that utilize bivalve reefs, is the inability to consistently incite reef-formation to optimize the impact of their services in key areas (as discussed in La Peyre et al., 2015, Walles et al., 2016a, Walles et al., 2016b. ...
Article
Nature-based coastal defense schemes commonly value bivalve reefs for i) reducing coastal erosion in the intertidal and for ii) forming fringing reefs near salt marsh edges to protect them against lateral retreat. The capacity for a reef to reduce erosion increases at a higher position in the tidal frame as the lower over-lying water level magnifies the influence of the reef on wave attenuation. Unfortunately, ecological constraints on reef development typically limit their practical application in coastal protection schemes to the lower intertidal, as bivalves grow best with long inundation times. In micro-tidal areas this is a lesser problem, given the close proximity of lower and upper intertidal ecosystems in space. By contrast, in meso- and macro-tidal estuaries, bivalve reefs tend to form hundreds of meters away from existing marshes, nullifying any wave-protective benefits. In this study, we produce evidence that with the assistance of management measures, widespread reef formation is possible on open mudflats, including bordering the marsh edge in meso- and macro-tidal estuaries, where natural reef formation is normally strongly limited. In four locations throughout the meso- to macro-tidal Dutch Scheldt estuary, we observed the presence of individuals of two major intertidal reef-forming bivalves, Pacific oysters (Crassostrea gigas) and blue mussels (Mytilus edulis), within low-lying Spartina anglica-dominated marshes. As these communities lie well outside of the expected range of reef formation, this observation suggests the existence of mechanisms that extend the habitable range of these bivalves. In a series of field experiments, we first demonstrate how the stabilization of shell-substrate within the marsh promotes successful establishment and adult survival. Secondly, by placing artificial stable substrate in transects from the subtidal up to the marsh edge, we demonstrate that bivalve establishment is possible throughout a much larger range of the intertidal than where natural reefs occur. The effectiveness of stable substrate in stimulating bivalve establishment is likely a consequence of bridging size-dependent thresholds that limit the effective range for natural reef formation on tidal flats. The success of this approach is tempered by a consistent decrease in reef size and growth at higher elevations, suggesting that the optimal reef position for utility in coastal defense lies at an intermediate tidal position, well above the observed range of natural occurrence, but below the maximum achievable upper limit of reef formation. Together this work provides a pathway forward concerning how artificial reefs may be fostered to increase their utility as a nature-based flood defense measure.
... Reef habitat complexity (the physical structure of an environment) is predicted to increase with reef age as oysters settle atop one another and grow vertically in the water column (Bahr and Lanier 1981;Grabowski et al. 2005;Rodriguez et al. 2014;Ziegler et al. 2018). Such habitat complexity has been linked to habitat quality for associated communities, with interstitial refuges that decrease interaction strengths (i.e., predation, Humphries et al. 2011) and increase rugosity, which alters water flow and enhances larval settlement opportunities (Breitburg et al. 1995). ...
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The rapid loss of coastal and estuarine biogenic habitats has reduced the delivery of valuable ecosystem services, resulting in calls for increased habitat restoration. Yet, a lack of information on how key habitat characteristics (e.g., area, vertical relief, age) influence the ability of restored habitats to deliver these ecosystem services hinders efforts to maximize the return on restoration investments. We conducted a meta‐analysis to assess the influence of reef type (natural or restored), taxa, and restored reef size, vertical relief, age, and tidal zone on the presence and magnitude of recruitment enhancement for nekton (i.e. fish and swimming crabs). Both intertidal and subtidal reefs, as well as restored and natural reefs, enhanced nekton recruitment, though there was variation among taxonomic groups with reef types. Recruitment enhancement was more common across taxa on restored (six families) than on natural (one family) reefs. Resident nekton families were more consistently enhanced than transient families. Nekton enhancement varied with a number of restored reef characteristics. Recruitment enhancement increased with greater reef size across taxa, decreased with higher vertical relief for two families, and showed maximum recruitment around a single intertidal reef age for one family, and minimum recruitment around a single subtidal reef age for three families. Understanding variation across species in response to key design elements will improve restoration success and enhance return on investment. Moving forward, we recommend studies that vary reef habitat characteristics independently and in combination to identify how variation in these characteristics interact to influence nekton recruitment enhancement by oyster reefs.
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Essential fish habitat is critical for foraging, breeding, or as refugia. As such, restoration of these habitats has the potential to increase the diversity and abundance of fishes. Here, we explored how fish communities responded in the first 12-24 mo following oyster reef restoration. Study sites included 8 restored reefs plus 4 live and 4 dead reefs as controls. Oyster reef metrics (e.g. density, height, thickness) and fish abundance and diversity metrics were quantified, including species richness, Shannon diversity, Simpson’s diversity, and Pielou’s evenness. Species composition was explored further to identify indicator species and assess habitat preferences. Patterns of fish community diversity and species composition were compared to oyster reef metrics to discern what oyster reef characteristics best predict fish diversity. Results showed that intertidal oyster reefs were structurally restored and shifted from resembling negative control reefs to positive control reefs within 12-24 mo. Across all treatment types, oyster shell height and reef thickness were the best predictors of fish diversity. However, at the fish community level, assemblages at restored reefs were similar to those at positive and negative controls. Species-level analyses suggest treatment types have unique indicator species, including Chilomycterus schoepfi (striped burrfish) for dead reefs, Lutjanus synagris (lane snapper) for restored reefs, and Gobiosoma robustum (code goby) for live reefs. This work suggests fishes can be used as higher trophic level indicators of restoration success, and ecosystem-based approaches, such as habitat restoration, can restore essential fish habitat, thus benefiting fish communities while moving coastal ecosystems toward sustainability.
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Within estuarine and coastal ecosystems globally, extensive habitat degradation and loss threaten critical ecosystem functions and necessitate widescale restoration efforts. There is abundant evidence that ecological processes and species interactions can vary with habitat characteristics, which has important implications for the design and implementation of restoration efforts aimed at enhancing specific ecosystem functions and services. We conducted an experiment examining how habitat characteristics (presence; edge vs. interior) influence the communities of resident fish and mobile invertebrates on restored oyster (Crassostrea virginica) reefs. Similar to previous studies, we found that restored reefs altered community composition and augmented total abundance and biomass relative to unstructured sand habitat. Community composition and biomass also differed between the edge and interior of individual reefs as a result of species‐specific patterns over small spatial scales. These patterns were only weakly linked to oyster density, suggesting that other factors that vary between edge and interior (e.g., predator access or species interactions) are likely more important for community structure on oyster reefs. Fine‐scale information on resident species’ use of oyster reefs will help facilitate restoration by allowing decision makers to optimize the amount of edge vs. interior habitat. To improve the prediction of faunal use and benefits from habitat restoration, we recommend investigations into the mechanisms shaping edge and interior preferences on oyster reefs. This article is protected by copyright. All rights reserved.
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Oyster reef restoration is increasingly used as a tool for restoring lost ecosystem services in degraded aquatic systems, but questions remain about the efficacy of the practice and when/if restored reefs may behave similarly to intact natural reefs. In this case study, field observations highlighted short- (<1 month post-restoration) and longer-term (30 months; 3 recruitment cycles) transformations in canopy, hydrodynamic, and biogeochemical characteristics of a restored intertidal oyster reef relative to nearby intact and degraded reefs. Within 12 months of restoration, live oyster density (326 oysters/m²), mean shell length (47 mm), and mean canopy height (76 mm) did not differ significantly from those observed on a reference reef. Lowering of the reef crest during restoration reestablished over-reef flow and periodic tidal inundation, improving hydraulic connectivity between the channel and the reef surface. This immediately restored much of the reef's hydrodynamic function and eliminated the irregular flow patterns observed on the previously degraded reef. Results showed that mean flow (channel-to-reef flow attenuation: 98% / 62%; within/above canopy) and velocity normalized turbulence (w'2¯/U2: 10⁻¹/10⁻²; ϵ/U³: 10⁰/10⁻² m⁻¹) characteristics were similar across the restored and reference reefs within 1 year of restoration, with temporal changes in mixing within the canopy attributed to increases in live oyster density. Nutrient pools (mean total carbon, total nitrogen) on reference and restored reefs had similar magnitudes within 1 year (C: 39 & 33 g/kg, N: 1.5 & 1.8 g/kg), while increases in DOC and NH4⁺ were correlated with the presence of live oysters. Most changes that occurred on the restored reef were linked to oyster recruitment and canopy growth, which modulated hydrodynamics through direct flow interactions and controlled sediment nutrient and organic matter content through waste deposition and burial.
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Given the global collapse of most oyster fisheries, we explored the conditions under which the interaction of oysters and fishers can lead to multiple system equilibria, and how those conditions might affect management strategies and recovery efforts. Using simple, but plausible, models of oyster fisheries, we identified tipping points, multiple equilibria, and hysteresis under a wide range of realistic model parameterizations. In collapsed systems with hysteresis, recovery of the system will require far less harvest than that which precipitated the collapse, and recovery times can be on decadal scales. We also derived optimal, non-equilibrium, state-dependent fishing policies and found that these policies can perform well, but are accompanied by high variation in the allowable harvest. Critically, these optimal policies also require constant monitoring of system state and frequent control of fishing effort. Finally, we examined habitat-enhancement scenarios that mimic proposed and ongoing restoration programs. We found that these efforts can increase the number of fishers the system can support and reduce otherwise long recovery times in collapsed systems.
Chapter
The rapid degradation of ecosystems jeopardizes the services they provide. Among the most valuable of these services is protection of coastlines by shoreline ecological communities, such as coral reefs, mangroves and salt marshes. Currently, coastal protection potential of ecosystems is estimated primarily as a function of their spatial extent and type. The degree to which coastal protection depends on aspects of biodiversity within and across these ecosystems is, however, much less explored. Here we synthesize evidence from multiple sources to evaluate whether aspects of biodiversity may influence the degree of coastal protection afforded by coastal ecosystems. We discuss relevant biodiversity theory and the few studies that have investigated how species identity affects shoreline protection, as a first attempt to identify the aspects of biodiversity that are likely to be important in enhancing coastal protection efforts. This synthesis should empower ecologists, conservation scientists and practitioners to test for and then harness the unrealized, but high yield potential, of incorporating biodiversity into coastal defense planning.
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To confront the myriad challenges posed by climate change, we present oysters as a nature-based solution with an abundance of environmental benefits and economic stimulus to coastal communities. We encourage the Biden administration to support international efforts to restore oyster reefs by presenting an “Oyster Restoration Initiative” to the World Economic Forum, mirroring recent actions on trees. On the domestic front, several legislative actions can be taken to sustain the current trajectory of restoration efforts. These efforts can be pursued in tandem, but we recommend that policy actions focus on expanding low carbon, oyster-based restorative aquaculture programs. This can revolutionize U.S. food production while reducing pollution from other forms of agriculture.
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Salt marshes are highly dynamic and important ecosystems that dampen impacts of coastal storms and are an integral part of tidal wetland systems, which sequester half of all global marine carbon. They are now being threatened due to sea-level rise, decreased sediment influx, and human encroachment. This book provides a comprehensive review of the latest salt marsh science, investigating their functions and how they are responding to stresses through formation of salt pannes and pools, headward erosion of tidal creeks, marsh-edge erosion, ice-fracturing, and ice-rafted sedimentation. Written by experts in marsh ecology, coastal geomorphology, wetland biology, estuarine hydrodynamics, and coastal sedimentation, it provides a multidisciplinary summary of recent advancements in our knowledge of salt marshes. The future of wetlands and potential deterioration of salt marshes is also considered, providing a go-to reference for graduate students and researchers studying these coastal systems, as well as marsh managers and restoration scientists.
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Nature-based methods use the creation or restoration of coastal habitats for hazard risk reduction. This can be done through restoring the habitat alone (“soft” approach), or in combination with hard structures that support habitat establishment (“hybrid” approaches). The need to develop, test and apply more sustainable techniques to mitigate the impacts of coastal hazards has been identified as a national priority. One reason that nature-based methods have been underutilised in Australia is that decision-makers need clearer guidelines for when a soft, hybrid or hard coastal defence approach is most appropriate. International exemplars in nature-based methods have started this process, which include Ecoshape’s Building with Nature in Europe and the Army Corps of Engineers’ Engineering-with-Nature® in the United States. Here we build on this international knowledge and national research efforts to provide an Australian context for nature-based methods, as wider adoption of these techniques nationally requires accounting for the environmental, economic and socio-political contexts specific to Australia. This guideline summarises the physical processes that underpin nature-based methods, and the ecological and engineering considerations for their application based on the major coastal ecosystems found in Australia. It also provides frameworks for implementing nature-based methods and conducting a benefit-cost analysis, and the policy landscape within which nature-based methods can be applied. The aim of this document is to translate the known global and Australian research into a practical tool that can be used to support decisions by coastal practitioners to use nature-based methods.
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Habitat structure influences a broad range of ecological interactions and ecosystem functions across biomes. To understand and effectively manage dynamic ecosystems, we need detailed information about habitat properties and how they vary across spatial and temporal scales. Measuring and monitoring variation in three‐dimensional (3D) habitat structure has traditionally been challenging, despite recognition of its importance to ecological processes. Modern 3D mapping technologies present opportunities to characterize spatial and temporal variation in habitat structure at a range of ecologically relevant scales. Biogenic reefs are structurally complex and dynamic habitats, in which structure has a pivotal influence on ecosystem biodiversity, function and resilience. For the first time, we characterized spatial and temporal dynamics in the 3D structure of intertidal Sabellaria alveolata biogenic reef across scales. We used drone‐derived structure‐from‐motion photogrammetry and terrestrial laser scanning to characterize reef structural variation at mm‐to‐cm resolutions at a habitat scale (~35 000 m2) over 1 year, and at a plot scale (2500 m2) over 5 years (2014–2019, 6‐month intervals). We found that most of the variation in reef emergence above the substrate, accretion rate and erosion rate was explained by a combination of systematic trends with shore height and positive spatial autocorrelation up to the scale of colonies (1.5 m) or small patches (up to 4 m). We identified previously undocumented temporal patterns in intertidal S. alveolata reef accretion and erosion, specifically groups of rapidly accreting, short‐lived colonies and slow‐accreting, long‐lived colonies. We showed that these highly dynamic colony‐scale structural changes compensate for each other, resulting in seemingly stable reef habitat structure over larger spatial and temporal scales. These patterns could only be detected with the use of modern 3D mapping technologies, demonstrating their potential to enhance our understanding of ecosystem dynamics across scales. Modern 3D mapping technologies present opportunities to investigate spatial and temporal variation in habitat structure across ecologically relevant scales. We used 3D mapping to characterize biogenic reef structural variation at mm‐to‐cm resolutions, at plot to habitat extents, over 1–5 years. We reveal previously undocumented spatial and temporal patterns in reef structure dynamics, providing insight into the ecology of these complex habitats.
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To investigate isotope fractionation between biogenic carbonates and modern seawater, we measured K concentration, phase, and isotopic composition in calcified skeletons from a variety of calcifying species. Samples included deep-sea corals, hermatypic corals, bivalves, gastropods, brachiopods, and planktonic foraminifera recovered globally over the past ten years in habitats with temperatures varying from 2 to 29 °C. The δ41K values of the calcified organisms vary significantly, ranging from −0.72 ± 0.11 to 0.94 ± 0.04‰. Deep-sea corals exhibit the largest isotopic variability and the lowest δ41K, ranging from −0.72 ± 0.11 to 0.28 ± 0.09‰. Hermatypic corals display a moderate δ41K, ranging from −0.20 ± 0.07 to 0.37 ± 0.10‰. Bivalves display widely variable δ41K values from 0.04 ± 0.05 to 0.94 ± 0.04‰, including the highest δ41K observed. Gastropods exhibit δ41K values between −0.42 ± 0.06 and −0.12 ± 0.06‰, while brachiopods have δ41K values from −0.30 ± 0.05 to 0.24 ± 0.06‰. Limited foraminifera samples (n = 2) reveal δ41K values of 0.15 ± 0.06 to 0.21 ± 0.06‰. Synchrotron-based atomic analyses show that K in biogenic carbonates is dominantly hosted in amorphous K2CO3, calcite-like and aragonite-like K phases, and intracrystalline organic matrices of varying proportions. The K isotopic composition of marine biogenic carbonates is not strongly temperature-dependent, in general, but correlates with skeletal K phases. This phase-control may indicate a first-order biological control on skeletal K incorporation, partitioning, and associated K isotope fractionation. This appears to reflect a substantial “vital effect”; i.e., physiological modification of the environmental information recorded in calcifying organisms. Substantial variations in δ41K call for additional scrutiny before using marine biogenic carbonates to interpret ancient seawater δ41K composition as physiological modulation substantially complicates the interpretation of marine carbonate δ41K records through time. Future studies should include species-specific calibration with complementary synchrotron data to refine K isotope applications for paleoceanography.
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Native oyster reefs once dominated many estuaries, ecologically and economically. Centuries of resource extraction exacerbated by coastal degradation have pushed oyster reefs to the brink of functional extinction worldwide. We examined the condition of oyster reefs across 144 bays and 44 ecoregions; our comparisons of past with present abundances indicate that more than 90% of them have been lost in bays (70%) and ecoregions (63%). In many bays, more than 99% of oyster reefs have been lost and are functionally extinct. Overall, we estimate that 85% of oyster reefs have been lost globally. Most of the world's remaining wild capture of native oysters (> 75%) comes from just five ecoregions in North America, yet the condition of reefs in these ecoregions is poor at best, except in the Gulf of Mexico. We identify many cost-effective solutions for conservation, restoration, and the management of fisheries and nonnative species that could reverse these oyster losses and restore reef ecosystem services.
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Valuation of ecosystem services can provide evidence of the importance of sustaining and enhancing those resources and the ecosystems that provide them. Long appreciated only as a commercial source of oysters, oyster reefs are now acknowledged for the other services they provide, such as enhancing water quality and stabilizing shorelines. We develop a framework to assess the value of these services. We conservatively estimate that the economic value of oyster reef services, excluding oyster harvesting, is between $5500 and $99,000 per hectare per year and that reefs recover their median restoration costs in 2–14 years. In contrast, when oyster reefs are subjected to destructive oyster harvesting, they do not recover the costs of restoration. Shoreline stabilization is the most valuable potential service, although this value varies greatly by reef location. Quantifying the economic values of ecosystem services provides guidance about when oyster reef restoration is a good use of funds.
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Integrating how habitat heterogeneity influences food web dynamics is critical to enhance our understanding of community structure. This study quantified resident (invertebrates) and transient (juvenile and piscivorous fish) fauna within restored intertidal oyster reefs and analogous control sites without reef habitat in each of three habitats (on the edge of salt marsh away from seagrass, on mudflats isolated from vegetated structures, and in between seagrass and salt marsh habitat). Reefs enhanced the abundance of resident invertebrates (e.g., polychaetes, nemerteans, epibenthic anemones, bivalves, and resident decapods) that comprise >90% of juvenile fish prey biomass. However, the increase in food availability due to reef presence did not affect abundance of juvenile fish in either of the vegetated habitats, suggesting that resources may not limit juvenile fish when restored in these habitats. Only mudflat reefs augmented juvenile fish abundances, most likely due to a combination of greater resource availability and relative isolation from functionally equivalent habitats. In addition, lower abundances of piscivorous fish in mudflat reefs relative to control areas likely contributed to this pattern. Thus, community structure and important ecosystem functions such as secondary production depend on the spatial configuration of surrounding habitats, in much the same way that species interactions can depend on their biotic and abiotic context.
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This chapter discusses how to quantify the economic value of each of the ecosystem services provided by oyster reefs. The chapter also provides quantitative estimates of the value of some specific functions (i.e., oyster harvests, water quality improvements, and recreational and commercial fishery benefits) where data are available to compare the value of harvesting oysters in a traditional fishery to the monetary value of providing other oyster reef services. Placing oyster reefs in the greater context of the estuary requires landscape-scale data with simultaneous evaluation of each habitat across multiple trophic levels, which is difficult to obtain. However, larger-scale restoration efforts to assess the recovery of ecosystem services are currently being conducted in the Gulf of Mexico and in several estuaries along the East Coast of the United States. These studies will greatly enhance one's ability to develop more holistic economic models that account for spatial variability in the provision of ecosystem goods and services by oyster reefs.
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Dramatic declines in populations of the eastern oyster Crassostrea virginica are a symptom of degradation in many US Atlantic and Gulf of Mexico estuaries. We sampled 94 oyster reefs (88 constructed, 6 natural) within 11 no-harvest sanctuaries in estuaries of central and northern North Carolina, USA, to evaluate the success of oyster sanctuaries as a conservation tool. The sanctuaries have been in existence from 3 to 30 yr; 10 sanctuaries protect constructed ('restored') oyster reefs and 1 sanctuary protects natural reefs. Measurements of vertical relief, live oyster density, recruitment, abundance of market-sized oysters, and biomass as well as disease prevalence and severity indicated that 7 of the 11 sanctuaries met criteria for minimal success by having vertical relief >20 cm in height, living oysters (>10 oysters m(-2)), and evidence of recent recruitment in 1. of 2 yr of the survey. Most reefs within the 7 sanctuaries far surpassed these relatively low benchmarks. For reefs that failed, burial by sedimentation appeared to be the primary cause in 2 sanctuaries, poor water quality (low dissolved oxygen) in 1, and poor oyster recruitment in another. All intertidal reefs were successful and had significantly higher densities of all size categories of live oysters (spat, adult, marketable size) than subtidal oyster reefs. Disease prevalence and severity were low in sanctuary reefs despite high oyster densities and increased longevity of oysters on these reefs. Pronouncements that restoration of the native eastern oyster is a failure prove incorrect when a decade-long history of oyster reef sanctuaries is evaluated. The proposed introduction of a non-native oyster into the US Atlantic coast estuaries cannot be justified by claiming failure of native oyster restoration in light of promising successes within sanctuaries.
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To assess the role of live oysters in providing habitat, community metrics of resident fishes and decapod crustaceans were compared among 3 habitat treatments: live oyster clusters; cleaned, articulated shell; and sand bottom. Samping was conducted during three seasonally wet and three seasonally dry months using 1-m2 lift nets deployed on an intertidal oyster reef in the Caloosahatchee estuary, Florida. Metrics used to assess relative habitat value included organism density, biomass and species richness. Species-specific comparisons were also made. Results indicate that organism density, biomass and richness were all greater for treatments with shell (live oyster clusters or cleaned, articulated shell) compared with the sand-bottom (no-shell) treatment. Two patterns emerged from species-specific comparisons: (1) species found in live and articulated shell (e.g., flatback mud crab, green porcelain crab) might requrie shelter; and (2) species found in associated with articulated, cleaned shell (i.e., frillfin goby) might use empty oyster boxes for spawning substrate. There was little evidence to suggest that any of the decapods or fishes present were specifically selecting habitat with living oysters present.
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Mangrove wetlands exist in the transition zone between terrestrial and marine environments and as such were historically overlooked in discussions of terrestrial and marine carbon cycling. In recent decades, mangroves have increasingly been credited with producing and burying large quantities of organic carbon (OC). The amount of available data regarding OC burial in mangrove soils has more than doubled since the last primary literature review (2003). This includes data from some of the largest, most developed mangrove forests in the world, providing an opportunity to strengthen the global estimate. First-time representation is now included for mangroves in Brazil, Colombia, Malaysia, Indonesia, China, Japan, Vietnam, and Thailand, along with additional data from Mexico and the United States. Our objective is to recalculate the centennial-scale burial rate ofOC at both the local and global scales. Quantification of this rate enables better understanding of the current carbon sink capacity of mangroves as well as helps to quantify and/or validate the other aspects of the mangrove carbon budget such as import, export, and remineralization. Statistical analysis of the data supports use of the geometric mean as the most reliable central tendency measurement. Our estimate is that mangrove systems bury 163 (+40; ?31) g OC m?2 yr?1 (95% C.I.). Globally, the 95% confidence interval for the annual burial rate is 26.1 (+6.3; ?5.1) Tg OC. This equates to a burial fraction that is 42% larger than that of the most recent mangrove carbon budget (2008), and represents 10–15% of estimated annual mangrove production. This global rate supports previous conclusions that, on a centennial time scale, 8–15% of all OC burial in marine settings occurs in mangrove systems.
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Data
1] Mangrove wetlands exist in the transition zone between terrestrial and marine environments and as such were historically overlooked in discussions of terrestrial and marine carbon cycling. In recent decades, mangroves have increasingly been credited with producing and burying large quantities of organic carbon (OC). The amount of available data regarding OC burial in mangrove soils has more than doubled since the last primary literature review (2003). This includes data from some of the largest, most developed mangrove forests in the world, providing an opportunity to strengthen the global estimate. First-time representation is now included for mangroves in and Thailand, along with additional data from Mexico and the United States. Our objective is to recalculate the centennial-scale burial rate of OC at both the local and global scales. Quantification of this rate enables better understanding of the current carbon sink capacity of mangroves as well as helps to quantify and/or validate the other aspects of the mangrove carbon budget such as import, export, and remineralization. Statistical analysis of the data supports use of the geometric mean as the most reliable central tendency measurement. Our estimate is that mangrove systems bury 163 (+40; À31) g OC m À2 yr À1 (95% C.I.). Globally, the 95% confidence interval for the annual burial rate is 26.1 (+6.3; À5.1) Tg OC. This equates to a burial fraction that is 42% larger than that of the most recent mangrove carbon budget (2008), and represents 10–15% of estimated annual mangrove production. This global rate supports previous conclusions that, on a centennial time scale, 8–15% of all OC burial in marine settings occurs in mangrove systems.
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Salt marshes are valuable yet fragile ecosystems, disappearing globally at an alarming rate. Facing this crisis, it becomes increasingly important to understand what forces drive their formation. Previous studies of marsh ontogeny relied on stratigraphy and physical monitoring, depending on inferences from multi-century and daily time scales, respectively. In this study, vertical accretion rates are evaluated at the same time resolution as a marsh’s lateral expansion, providing the fi rst comprehensive view of a laterally expanding marsh’s sedimentary trajectory. 210Pb-derived (half-life, t1/2, of 22.3 yr) accretion rates are examined in a marsh at the Newport River (North Carolina, United States), a location experiencing ongoing emergence of new marshland over the past century. Accretion rates at all marsh sampling sites begin with slow sedimentation characteristic of the bay bottom, then shift to rapid, persistent sedimentation, eventually progressing from submerged mudfl at to marsh table. Acceleration of vertical accretion occurs asynchronously across the marsh and prior to vegetative colonization, indicating a physical mechanism. We hypothesize that extant marsh tables act as promontories, effectively shielding adjacent mudfl ats from erosive forces, dictating the trajectory of marsh emergence, and yielding the pattern of alongshore marsh emergence at the Newport River.
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Cheniers and oyster reefs are two essential components of Holocene strata on the coast of Bohai Bay, China. The existing nonconventional14C dates, often with unsuitable sample positions, less-tested samples, and unreasonable data comparisons, limit the refined analysis of the local chronostratigraphy. On the basis of a number of pretreatment routines, including geological investigations, X-ray diffraction analysis (XRD), δ13C measurement of shells, selection of appropriate shell species (Umboniumsp. and Terebridae) for14C dating, and determination of the local mean δ13C value (−2.68‰ PDB) for the common shells, a set of samples was radiocarbon-dated by Accelerator Mass Spectrometry (AMS). These new ages, obtained from the lower part of cheniers, enable us to estimate the initiation of the cheniers, and confirm that the existing nonconventional dates are often questionable due to unsuitable sample positions. Another two AMS ages, dated for two different microgrowth layers, precipitated in a varying water body, of the sameCrassostrea gigasshell are statistically identical within 2σ error. This implies that the different water masses in the coastal environment would be rapidly in balance with the contemporaneous atmospheric CO2. Both MARINE93 and INTERCAL93 were used for calibration of radiocarbon dates. These amended the time frame of the local Holocene history.
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SEA-LEVEL records indicate that the coast of Louisiana and other parts of the Gulf Coast are rapidly subsiding1. Louisiana is now losing approximately 16 square miles of land per year, primarily to subsidence2; the rates of subsidence vary with location. Vertical marsh accretion is the process which counteracts subsidence and eustatic sea-level rise and prevents marsh deterioration, but, as in Louisiana's salt marshes, the pattern, rate and variability are sufficiently complicated to defy simple prediction. Conditions of marsh development vary throughout the coast, from the modern and Atchafalaya deltas through the abandoned deltas to the Chenier Plain3. In recent years, much of the coastal area such as Barataria Basin has been deprived of river-borne sediment through natural stream diversion and the construction of water-control embankments. In addition, dredging from petroleum operations has altered water flow and sedimentation patterns. The survival and productivity of Gulf Coast marshes depend on the influx and accumulation of sediment that offsets the effect of subsidence and maintains the marsh surface within the tidal range. To predict long-range trends in marsh stability, accurate measurements are needed of both subsidence and sedimentation rates. Information on subsidence is available from tide gauge measurements but no measurements have been made of sedimentation rates in marshland developed on Recent Mississippi alluvium. 137Cs, a fallout product of nuclear testing, has become a useful tool for dating recent sedimentary sequency in lakes4–8. We report here its use in the measurement of sedimentation rates in a Louisiana coastal marsh, the first report of such use in coastal marshes.
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Coastal protection remains a global priority. Protection and maintenance of shoreline integrity is often a goal of many coastal protection programs. Typically, shorelines are protected by armoring them with hard, non-native, and nonsustainable materials such as limestone. This study investigated the potential shoreline protection role of created, three-dimensional Eastern oyster (Crassostrea virginica) shell reefs fringing eroding marsh shorelines in Louisiana. Experimental reefs (25 × 1.0 × 0.7 m; intertidal) were created in June 2002 at both high and low wave energy shorelines. Six 25-m study sites (three cultched and three control noncultched) were established at each shoreline in June 2002, for a total of 12 sites. Shoreline retreat was reduced in cultched low-energy shorelines as compared to the control low-energy shorelines (analysis of variance; p < 0.001) but was not significantly different between cultched and noncultched sites in high-energy environments. Spat set increased from 0.5 ± 0.1 spat/shell in July 2002 to a peak of 9.5 ± 0.4 spat/shell in October 2002. On average, oyster spat grew at a rate of 0.05 mm/day through the duration of the study. Recruitment and growth rates of oyster spat suggested potential reef sustainability over time. Small fringing reefs may be a useful tool in protecting shorelines in low-energy environments. However, their usefulness may be limited in high-energy environments.
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Rates of shell production rarely exceed 500 g CaCO3.m-2yr-1 in clastic sediments. Loss of shell carbonate by dissolution greatly exceeds loss by bioerosion and abrasion in most habitats. Rates of shell dissolution in modern sediments, estimated from rates of organic carbon degradation or measured directly, usually exceed 1000 g CaCo3.M-2yr-1. This taphonomic loss is concentrated at or just below the sediment-water interface in the taphonomically-active zone (TAZ). Consequently, except where rates of shell production are very high or rates of organic carbon degradation very low, shells cannot permanently accumulate on the sea floor. Preservation requires rapid burial, usually by physical ‘event’ processes, to slow down taphonomic loss. Only near the base of the TAZ does the long-term sedimentation rate become an effective mediator of shell preservation as sediment accumulation gradually removes buried shell material from the taphonomically-active zone.
Article
Oyster cultch was added to the lower intertidal fringe of three created Spartina alterniflora marshes to examine its value in protecting the marsh from erosion. Twelve 5-m-wide plots were established at each site, with six randomly selected plots unaltered (non-cultched) and cultch added to the remaining (cultched) plots. Within each cultched plot, cultch was placed along the low tide fringe of the marsh during July 1992, in a band 1.5 m wide by 0.25 m deep. Marsh-edge vegetation stability and sediment erosion were measured for each plot from September 1992 to April 1994. Significant differences (p < 0.05) in marsh-edge vegetation change were detected at the only south-facing site after a major southwester storm. Significantly different rates of sediment erosion and accretion also were observed at this same site. Areas upland of the marsh edge in the cultched areas showed an average accretion of 6.3 cm, while noncultched treatment areas showed an average loss of 3.2 cm. A second site, with a northern orientation, also experienced differential sediment accretion and erosion between treatment type, caused instead by boat wakes that were magnified by the abutment of a dredge effluent pipe across the entire front fringe of the site. During this period we observed significant differences in sediment accumulation, with the areas upland of the marsh edge in the cultched treatment having an average accretion of 2.9 cm and the noncultched an average loss of 1.3 cm.
Article
Wreck Shoal is a subtidal oyster reef located in the James River estuary, Virginia. This estuary has moved upstream and landward in response to rising sea level. The recent geomorphic history of Wreck Shoal is analyzed based on bathymetric records from the 1850’s to the 1980’s. The data indicate that the shallow oyster reef areas have lost elevation in the last 130 yr. This is attributed to intense harvesting activity during the last century. The late Holocene evolution of Wreck Shoal is developed based on the results of sub-bottom profiles and coring data. These suggest that the Wreck Shoal oyster reef has developed on the ridge and swale topography of a point-bar formed during the late Pleistocene epoch. Contemporary biodeposition processes on Wreck Shoal are evaluated. The results indicate that sediments of biogenic origin (fecal and shell material) potentially accumulate at rates in excess of 50 cm 100 years−1. A model for subtidal oyster reef development is proposed that accounts for sea level rise, biodeposition, and the harvesting activity of man. The model is verified with field observations of reef elevation and radiocarbon dates of oyster shell material. The implications of these results are that oyster reefs should be considered a renewable natural resource, and therefore managed accordingly in concert with the oysters.
Article
The effects of location, salinity, and depth on recruitment and growth of the eastern oyster Crassostrea virginica in Pamlico and Core sounds, North Carolina, were investigated from 1988 to 1990. We measured length and density of spat settling on oyster cultch deployed at deep (∼3 m) and shallow (∼1 m) depths at six sites in areas with low salinity and six sites in areas with high salinity. These data were compared with similar data taken at some of these sites by the North Carolina Division of Marine Fisheries since 1981 as part of their cultch planting program. Recruitment was generally greater in the high salinity sites, compared to the low salinity sites. Recruitment was less at shallow depths compared to deeper depths. In all three years the highest recruitment occurred in August and September, corresponding to the months of maximum water temperature. Recruitment was highly variable in space and time, but appeared to diminish from 1988 to 1990. Recruitment was reduced by sedimentation and a variety of sessile organisms. All sites appeared to have a similar potential for growth.
Article
Recent estimates of growth and mortality rates in extant Chesapeake Bay, USA oyster (Crassostrea virginica) populations are used to quantify changes in both population abundance (dN/dT) and shell accretion (dS/dT) associated with modern population demographics. The demographics of oyster populations that would be required to maintain reef accretion rates commensurate with sea level rise over geological time frames are examined using estimates of oyster longevity in pre-colonial (pre -1600) times combined with parallel estimates of pre-disease endemic mortality. The analysis demonstrates that modern populations, with their disease related, age-truncated demographics, are generally not capable of maintaining and building biogenic reefs through accretion. Estimates of filtration rates associated with Chesapeake Bay oyster populations prior to 1600 considerably underestimate actual benthic-pelagic coupling during that period. Pristine oyster populations would have supported water column turnover rates on the order of minutes to hours. Thus, the spatial footprint of oyster reefs was limited by available productivity in the estuary. Accretion rate calculations for pristine (pre-1600) oyster reefs describe the intimate relationship between benthic-pelagic coupling and the presence or absence of oyster reefs and the associated communities.
Article
Estuarine ecosystems have changed dramatically from centuries of fishing, habitat disturbance, sedimentation, and nutrient loading. Degradation of oyster reefs by destructive fishing practices in particular has had a profound effect on estuarine ecology, yet the timing and magnitude of oyster-reef degradation in estuaries is poorly quantified. Here, I evaluate the expansion and collapse of oyster fisheries in 28 estuaries along three continental margins through the analysis of historical proxies derived from fishery records to infer when oyster reefs were degraded. Exploitation for oysters did not occur randomly along continental margins but followed a predictable pattern. Oyster fisheries expanded and collapsed in a linear sequence along eastern North America (Crassostrea virginica), western North America (Ostreola conchaphila), and eastern Australia (Saccostrea glomerata). Fishery collapse began in the estuaries that were nearest to a developing urban center before exploitation began to spread down the coast. As each successive fishery collapsed, oysters from more distant estuaries were fished and transported to restock exploited estuaries near the original urban center. This moving wave of exploitation traveled along each coastline until the most distant estuary had been reached and overfished.
Article
The paradigmatic gradient for intertidal marine organisms of increasing physical stress from low to high elevation has long served as the basis for using direct effects of duration of water coverage to predict many biological patterns. Accordingly, changes in potential feeding time may predict the direction and magnitude of differences between elevations in individual growth rates of sessile marine invertebrates. Oysters (triploid Crassostrea ariakensis) experimentally introduced at intertidal (MLW+0.05 m) and subtidal (MLW-0.25 m) elevations in racks provided a test of the ability to use duration of water coverage to predict changes in growth. During early-to-mid winter, a depression of 38-47% in shell growth of intertidal oysters matched the 36% reduction in available feeding time relative to subtidal oysters. In late winter as solar heating of exposed oysters increased, growth differences of 52-55% departed only slightly from the predicted 39%. In spring, however, duration of water coverage failed to predict even the correct direction of growth change with elevation as intertidal oysters grew 34% faster despite 39% less feeding time. Intense seasonal development of shell fouling by other suspension feeders like ascidians, mussels, and barnacles on subtidal (94% incidence) but not on aerially exposed intertidal (21-38% incidence) oysters may explain why duration of water cover failed to predict spring growth differences. Less intense fouling develops on intertidal oysters due to the physiological stress of aerial exposure on settlers, especially during higher temperatures and longer solar exposures of spring. Fouling by suspension feeders is known to reduce growth of the host through localized competition for food and added energetic costs. Thus, in springtime, indirect effects of aerial exposure providing a partial refuge from biological enemies overwhelmed direct effects of reduced duration of water coverage to reverse the expected pattern of slower intertidal growth of a marine invertebrate.
The ecology of intertidal oyster reefs in the South Atlantic: A community profile
  • L M Bahr
  • W P Lanier
Bahr, L. M. & Lanier, W. P. The ecology of intertidal oyster reefs in the South Atlantic: A community profile. 105 (US Fish and Wildlife Service, Office of Biological Services 1981).
  • M E White
  • E A Wilson
White, M. E. & Wilson, E. A. in The Eastern Oyster: Crassostrea virginica (eds Kennedy, V. S., Newell, R. I. E. & Eble, A. F.) Ch. 16, 559-579 (Maryland Sea Grant, 1996).