Monitoring Performance of Shallow, Subtidal Restoration Oyster Reefs Using Advanced Technologies: A Case Study of Felgates Creek Reef (York River, Va) (original) (raw)
2007
The decline of the Eastern oyster, Crassostrea virginica, once a dominant feature of most Atlantic and Gulf coast estuaries, has led to large-and small-scale restoration efforts throughout the oyster's range (Kirby 2004, National Research Council 2004). Successes and failures in reef restoration have varied throughout the region. Understanding why different restoration projects succeed or fail is critical to the future optimal use of limited resources (e.g., shells, manpower) and the deployment of cost-effective, successful reef restoration projects. Communicating the results of ongoing oyster reef construction and assessment efforts also is vital (Coen and Luckenbach 2000). Leading oyster reef restoration practitioners from throughout the Gulf of Mexico and eastern U.S. coastal states met to discuss restoration goals, site selection parameters, metrics to assess success, and associated monitoring methods at a South Carolina Sea Grant sponsored workshop held in Myrtle Beach in May, 2004. This document summarizes the results of that workshop, providing a concise and non-technical explanation of the current state of knowledge regarding the why, where, what, and how of oyster reef restoration. We also expand on the workshop results to include information and approaches developed since 2004. Restoration Project Goals Workshop participants identified six major goals of oyster reef restoration projects: habitat creation, shoreline stabilization, water quality improvement, harvesting enrichment, broodstock enhancement, and educational outreach. Any restoration project can include one or more of these goals. Habitat creation: Oyster reefs provide habitat for fish and invertebrates (e.g., crabs and shrimps) that require structural complexity for foraging, nesting and refuge from predators (reviewed in ASMFC 2007). Fish associated with oyster reefs range from residents that use the reef as a primary habitat to transient species that are wide ranging and may forage on or near the reef (Breitburg 1999, Coen et al. 1999b, ASMFC 2007). Some fish species, such as oyster toad fish, gobies, and blennies, attach eggs to the undersides of oyster shells, relying on reef architecture or microhabitat for reproductive success. Crabs commonly are found in greater densities on oyster reefs than on surrounding open-bottom habitat where vulnerability to predation is greater and prey resources are less abundant (Glancy et al. 2003, Grabowski 2004, Tolley and Volety 2005, Hosack et al. 2006). Bivalves including clams and mussels also may utilize reefs as a refuge from predators (e.g., Grabowski 2002, 2004) enabling populations within reefs to act as a source for mudflat and marsh populations that may be depleted more easily by predators.
Oyster Habitat Restoration Monitoring and Assessment Handbook
Oyster reefs or beds are a globally imperiled marine habitat, with degradation primarily driven by anthropogenic factors such as overharvest, changes to hydrology and salinity regimens, pollution and introduced disease. While oyster restoration efforts have historically focused on improving harvests, in recent decades there has been an increasing recognition and better quantitative description of a broader array of ecological services provided by oysters. This has prompted many agencies and conservation organizations to re-focus their attention on restoring oyster habitat for these broader ecological functions and societal benefits. Benefits include production of fish and invertebrates of commercial, recreational and ecological significance, water quality improvement, removal of excess nutrients from coastal ecosystems, and stabilization and/or creation of adjacent habitats such as seagrass beds and salt marshes. Increasingly, these ecosystem services are cited as the principal or exclusive goal(s) of oyster restoration projects. Despite increased restoration the restored reefs have often not been monitored to an extent that allows for comparison. A recent meta-analysis of oyster restoration projects in the Chesapeake Bay examined the available datasets from 1990 to 2007, analyzing over 78,0000 records from 1035 sites (Kramer and Sellner 2009, Kennedy et al. 2011). The analysis found that relatively few of the restoration activities were monitored, and that the restoration goals of many of the projects were not well-defined, with only 43% of the datasets including both a restoration and monitoring component. The authors concluded that the monitoring of this large body of work was inadequate, and they were unable to assess changes in oyster populations on the constructed reefs. Their recommendations were to implement all oyster restoration projects using experimental designs with robust sample size replication and quantitative pre-and post-restoration monitoring. Sufficient monitoring would allow for adaptive management during the post-construction phase, for assessing whether the project met its goals and related performance criteria or to determine whether restored reefs are achieving the stated ecosystem-based restoration goals. To address this critical gap, a working group was formed that consisted of restoration scientists and practitioners from the Atlantic, Pacific, and Gulf coasts of the US. The aim of the group was to recommend monitoring techniques and performance criteria for both the eastern oyster (Crassostrea virginica) and the Olympia oyster (Ostrea lurida) that would allow for more extensive and consistent post-restoration assessment between projects on varying geographic scales. With additional expert input, the working group developed recommendations for a set of Universal Metrics that should be monitored for all oyster restoration projects. The working group also developed guidelines for assessing optional Restoration Goal-based Metrics. The Goal-based Metrics were not meant to be monitored for all projects, but could be monitored as needed to measure project performance and to advance the science of oyster habitat restoration depending on the availability of the necessary funding, capacity, and expertise. The Universal Metrics allow for the systematic assessment of the basic performance of restoration projects, whereas the Restoration Goal-based Metrics would allow practitioners to assess the performance of the restored reefs in meeting the ecosystem service-based restoration goal(s) associated with a project. Together, these metrics allow for the comparison of projects across a variety of scales and restoration approaches. Monitoring of the Universal Environmental Variables will also aid in the interpretation of Universal and Restoration Goal-based Metrics data collected through both pre-and post-restoration monitoring. The Universal Metrics that should be monitored for every oyster restoration project include: (1) reef areal dimension; (2) reef height; (3) oyster density; and, (4) oyster size-frequency distributions. Performance criteria for the Universal Metrics are based on emergent structure (assessed as reef height), successful recruitment, and oyster density present at both shortand mid-term post-construction time frames. The following Universal Environmental Variables should also be monitored for every oyster restoration project to aid with interpretation of Universal Metrics data: (1) water temperature; (2) salinity; and, (3) dissolved oxygen (for subtidal reefs). Restoration practitioners that lack the equipment or capacity to conduct the minimum required monitoring should collaborate with others able to provide this capability such as local researchers from academic institutions and local, state or federal agencies. Along with the Universal Metrics, the Restoration Goal-based Metrics are an optional set of monitoring guidelines provided to enable project managers to assess the following ecosystem service-based restoration goals: (1) brood stock and oyster population enhancement; (2) habitat enhancement for resident and transient species; (3) enhancement of adjacent habitats; and (4) water clarity improvement. This handbook is meant to be a living document that allows for future updates as monitoring methodologies and the state of the science evolve, and as meta-analyses of comparable data are undertaken. Restoration practitioners and other interested parties may at any time submit their comments and any suggestions for improvement to the handbook to ormetrics@gmail.com for consideration in future editions. The establishment of standardized restoration metrics has been a priority within the oyster restoration community for many years, and this handbook is built upon previous work (e.g.,
Ecological Engineering, 2000
Habitat restoration encompasses a broad range of activities, emphasizing very different issues, goals, and approaches depending on the operational definition of 'restoration'. This is particularly true for many shellfish (molluscan) dominated systems (e.g. oyster reefs, mussel beds, vermetid gastropod reefs). In contrast to other well-studied biogenic habitats, such as seagrasses, mangroves, or salt marshes, bivalves are directly consumed as a resource. Hence resource extraction has direct consequences for habitat health. Restoration objectives have typically included reduction of public health risks through improved water quality to increase harvest. Restoration or enhancement of populations of commercially exploited shellfish depressed by overharvesting and/or reduced environmental quality remains the principal motivation behind most shellfish 'restoration' efforts. Direct and indirect ecosystem services (e.g. filtering capacity, benthic-pelagic coupling, nutrient dynamics, sediment stabilization, provision of habitat, etc.) derived from oyster habitat have been largely ignored or underestimated. Only recently, the restoration of lost ecological function associated with shellfish communities has been included in our discussions and related research examining habitat development and function through a scientific approach. The former area has been reviewed extensively and will not be our focus here. In this review, we examine some of the restoration efforts made in the name of fisheries enhancement, address their effectiveness, and discuss some of the issues associated with realizing the broader goal of ecological restoration. We note the importance of linking success criteria to specific goals and make the case for a greater need in clarifying the ecological functions of shellfish and shellfish habitats. We recognize the limitations of existing datasets and summarize ongoing attempts to address oyster habitat restoration throughout the broad geographic distribution of the American oyster, Crassostrea 6irginica (Gmelin). In many ways this topic parallels the ongoing debate over 'attraction versus production' associated with artificial reef management. We consider how local conditions (e.g. tidal range, bottom topography, turbidity, salinity) and resulting habitat traits affect restoration strategies. We also discuss the underappreciated value of shellfish populations from those areas
Environments
Intertidal reefs of Crassostrea virginica (eastern oyster) provide ecologically valuable habitat in estuaries along the Atlantic coast of North America. In Mosquito Lagoon, a shallow-water estuary on the east coast of central Florida, USA, historical aerial imagery was used to document a 24% decline in the live C. virginica reef area between 1943 and 2009. Using 2021 imagery, every living and dead reef in the same region was manually digitized to identify changes during the intervening 12 years. Positive impacts of C. virginica reef restoration that took place between 2007 and 2021 were also digitized to quantify long-term restoration impact. Natural, live C. virginica reef coverage throughout the system was found to have decreased by 50.6% between 2009 and 2021 and, thus, 62.6% between 1943 and 2021. This was attributed to reef fragmentation, reef footprint loss, boating activity, and mangrove expansion. Of the 2542 live reefs identified using 2009 imagery, 219 reefs fragmented, 98...
Evaluating Intertidal Oyster Reef Development in South Carolina Using Associated Faunal Indicators
Restoration Ecology, 2010
Eastern oyster (Crassostrea virginica) habitat is increasingly being restored for the ecosystem services it provides rather than solely as a fishery resource. Community-based projects with the goal of ecological restoration have successfully constructed oyster reefs; however, the habitat benefits of these restoration efforts are usually not assessed or reported. In this study, we examined oyster habitat development at five community-based oyster restoration sites in South Carolina using oyster population parameters, resident fauna densities, and sedimentation (percent sediment coverage) as assessment metrics. All sites included multiple-aged reefs (1-3 years old) at the time of the fall 2004 sampling. Resident crabs and mussels were abundant at all five sites and crab assemblages were related to the size structure of the oyster microhabitat. Scorched mussel (Brachidontes exustus) abundances were most frequently correlated with oyster and other resident species abundances. Associations among oysters and resident crabs and mussels were not evident when analyses were conducted with higher level taxonomic groupings (e.g., total number of crabs, mussels, or oysters), indicating that species-level identifications improve our understanding of interactions among reef inhabitants and oyster populations. Community-based restoration sites in South Carolina provide habitat for mussels and resident crabs, in some cases in the absence of dense populations of relatively large oysters. Monitoring programs that neglect species-level identifications and counts of mussels and crabs may underestimate the successful habitat provision that can arise independent of large, dense oyster assemblages.
Oyster reef restoration in the northern Gulf of Mexico: Extent, methods and outcomes
2014
Available online a b s t r a c t Shellfish reef restoration to support ecological services has become more common in recent decades, driven by increasing awareness of the functional decline of shellfish systems. Maximizing restoration benefits and increasing efficiency of shellfish restoration activities would greatly benefit from understanding and measurement of system responses to management activities. This project (1) compiles a database of northern Gulf of Mexico inshore artificial oyster reefs created for restoration purposes, and (2) quantitatively assesses a subset of reefs to determine project outcomes. We documented 259 artificial inshore reefs created for ecological restoration. Information on reef material, reef design and monitoring was located for 94, 43 and 20% of the reefs identified. To quantify restoration success, we used diver surveys to quantitatively sample oyster density and substrate volume of 11 created reefs across the coast (7 with rock; 4 with shell), paired with 7 historic reefs. Reefs were defined as fully successful if there were live oysters, and partially successful if there was hard substrate. Of these created reefs, 73% were fully successful, while 82% were partially successful. These data highlight that critical information related to reef design, cost, and success remain difficult to find and are generally inaccessible or lost, ultimately hindering efforts to maximize restoration success rates. Maintenance of reef creation information data, development of standard reef performance measures, and inclusion of material and reef design testing within reef creation projects would be highly beneficial in implementing adaptive management. Adaptive management protocols seek specifically to maximize short and long-term restoration success, but are critically dependent on tracking and measuring system responses to management activities.
Fish Utilization of Created vs. Natural Oyster Reefs (Crassostrea virginica)
Estuaries and Coasts, 2018
Once viewed as an inexhaustible fishery resource, eastern oyster reefs (Crassostrea virginica) have been dramatically depleted. In North Carolina alone, eastern oyster harvests have declined by 90% since the early 1900s. However, eastern oyster restoration and management efforts have substantially increased since the 1970s. Oyster reefs provide habitat and refuge for organisms, improve water quality, and decrease erosion. Oyster restoration projects aim to construct reefs that function similarly to their natural counterparts. Therefore, post-creation monitoring of these reefs is crucial in determining restoration success. However, monitoring is often lacking or focused only on oyster density and size rather than ecosystem functions such as nekton utilization. This study examines nekton utilization among created reefs compared to natural reefs in an estuary in Wilmington, North Carolina. The objective was to determine whether the created reefs function similarly to the natural reefs in abundance, species richness, and fish size. Using seine nets and Breder traps, reefs were sampled over a 5-month period. No significant difference was detected among reefs for nekton abundance, species richness, and standard length. This is a promising result for future management, indicating that created and natural reefs can support similar communities of fishes and shrimp.
Oyster reefs at risk and recommendations for conservation, restoration, and management
Bioscience, 2011
kay, hunteR s. lenihan, MaRk W. luckenBach, caitlyn l. toRopova, guofan zhang, anD XiMing guo 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.
Habitat assessment of a restored oyster reef in South Texas
Ecological Engineering, 2018
Oyster reefs are important foundational habitats and provide many ecosystem services. A century of habitat degradation has resulted in substantial reductions in the extent and quality of oyster reefs in many estuaries, thus spurring restoration efforts. In this study, a 1.5 ha oyster reef complex was constructed in Copano Bay, Texas to restore habitat for oysters and associated fauna. Oysters and resident and transient fishes and crustaceans were monitored at the restored reef as well as at nearby natural oyster reef and unrestored bottom (i.e., dense mud with shell hash) habitats for two years following reef construction. The restored reef had substantial oyster recruitment and growth, with oyster abundance and size comparable to nearby habitats within the first year. Resident and transient fauna communities recruited to the restored reef within six months post-construction, and abundance and diversity were comparable to nearby habitats. Significant changes observed in oyster densities between the first and second year post-restoration demonstrate the importance of monitoring over multiple years to capture multiple recruitment cycles and growth to market size. Nekton densities did not change significantly after the first year, but changes in community assemblages were observed through the end of the study. The high densities of oysters and resident nekton relative to other studies indicate that this restoration project was successful in restoring suitable habitat. The design of the reef complex, consisting of relatively high-relief reef mounds and deeper corridors, likely contributed to the relatively high oyster and nekton densities observed in this study. Overall, the restored reef in this study showed tremendous near-term success in providing important ecological functions associated with habitat provision and oyster production.
A Resident Fish Guild as a Higher Trophic Level Indicator of Oyster Reef Restoration Success
Sustainability
Eastern oysters (Crassostrea virginica) are critical foundation species in estuarine waters, but due to a combination of natural and anthropogenic pressures, oyster abundance has declined. Restoring oyster reefs and monitoring restoration success often focuses on oyster metrics, but relatively infrequently, responses of higher trophic level species and the production of related ecosystem services are accounted for. To address this, we compare the response of a resident reef fish guild (gobies, blennies, toadfish) to standard metrics of oyster restoration success. Using lift nets and seines, natural and restored reefs were monitored over a two-year period within Mosquito Lagoon, Florida, USA. Standard metrics are indicative of restoration success; live oyster density and reef thickness increased in restored reefs after 12 and 24 months. Combined, live oyster density and reef thickness were the best predictors of annual resident reef fish abundance compared to water quality metrics. T...
Oyster reef restoration: convergence of harvest and conservation strategies
2000
Oyster ceef restoration. protecLion. and cons1-ruc1ion are importanc 10 meecing harvesc. water quality. and fish habilaL goals. However. Lhe SLraiegies needed to achieve harvest and conservation goals have often been considered to be a1 odds. We argue that these goals are, in faci. co,npatible and that the same strategies wiU pro1uote a sus1ainable harves1 of Lhe resource, increased filtration of estuarioe waters, and increased provision of struccurcd habitat for fiofish. crabs. and other organisn1s that utilize oys1er reefs or receive benefit iodirectly from then1. Creation or designations of unharvested si tes (refuge si tes) are key components of these stra1egies. Unharvested reefs have the potential to provide vertica l relief, which is typically des1royed by harvest practices. to ac1 as a source of larvae. which potentially increases the supply of harves1able oysters. and to protect those individuals most likely 10 have some resistance to disease. Furthermore, proper monitoring and design of refuge and restoration efforts are critical to providing information needed to improve the success of ft,ture restoration efforcs, and will simultaneously enhance the basic in formation needed 10 understand the ecology of oys1ers and Lheir role in estuarine and coastal syscems.
Guidelines for evaluating performance of oyster habitat restoration
Restoration Ecology, 2015
Restoration of degraded ecosystems is an important societal goal, yet inadequate monitoring and the absence of clear performance metrics are common criticisms of many habitat restoration projects. Funding limitations can prevent adequate monitoring, but we suggest that the lack of accepted metrics to address the diversity of restoration objectives also presents a serious challenge to the monitoring of restoration projects. A working group with experience in designing and monitoring oyster reef projects was used to develop standardized monitoring metrics, units, and performance criteria that would allow for comparison among restoration sites and projects of various construction types. A set of four universal metrics (reef areal dimensions, reef height, oyster density, and oyster size-frequency distribution) and a set of three universal environmental variables (water temperature, salinity, and dissolved oxygen) are recommended to be monitored for all oyster habitat restoration projects regardless of their goal(s). In addition, restoration goal-based metrics specific to four commonly cited ecosystem service-based restoration goals are recommended, along with an optional set of seven supplemental ancillary metrics that could provide information useful to the interpretation of prerestoration and postrestoration monitoring data. Widespread adoption of a common set of metrics with standardized techniques and units to assess well-defined goals not only allows practitioners to gauge the performance of their own projects but also allows for comparison among projects, which is both essential to the advancement of the field of oyster restoration and can provide new knowledge about the structure and ecological function of oyster reef ecosystems.
Journal of Shellfish Research, 2015
Globally, 85% of shellfish reefs have been lost during the past century. The severe loss of the eastern oyster Crassostrea virginica has encouraged different types of restoration efforts in the United States. In Mosquito Lagoon (ML), a shallow-water estuary on the east coast of central Florida, restoration focuses on providing additional substrate for larval recruitment via deployment of stabilized oyster shell. To assess the current number and area of natural, dead, and restored oyster reefs within ML, aerial photographs from 2009 were digitized using ArcGIS software. All reefs were screen digitized using a reef ''signature'' to estimate the surface area of each reef type. The maps from 2009 were then used as a guide to digitizing the historical
Decadal changes in oyster reefs in the Big Bend of Florida's Gulf Coast
Ecosphere, 2011
Oyster reefs are among the world's most endangered marine habitats with an estimated 85% loss from historical levels worldwide. Because of diverse ecological and social services to people and natural environments, and their sensitivity to impairment from natural and humaninduced disasters, understanding the resilience of oyster reef communities to disturbance is key to developing effective conservation and restoration plans. Florida's Big Bend coastline (Gulf of Mexico coast from Crystal River to Apalachee Bay) supports large expanses of oyster reef habitat that have existed for thousands of years in a region that is generally one of the most pristine coastal zones in the continental US. We assessed trends in oyster habitat along the Big Bend region between 1982 and 2011, by examining changes in areal extent and distance of oyster bars from shore. During our study period, we found a 66% net loss of oyster bar area (124.05 ha) with losses concentrated on offshore (88%), followed by nearshore (61%), and inshore bars (50%). Marsh-oyster bars area were more resilient during this time than sand-oyster bars (32% and 74% loss respectively). We also found that all oyster bars were generally moving inland. This rapid loss is very likely to be a departure from historical norms, and stems from multiple factors. Several lines of evidence suggest that the primary mechanism is reduced survival and recruitment as a result of decreased freshwater inputs, acting to make existing bars vulnerable to wave action and sea level rise. Once bar substrate becomes unconsolidated, the breakdown of the bar may not be reversible through natural processes. To test these predictions, we recommend restoration-based experiments to elicit the mechanisms in order to foster longterm sustainability of these critical estuarine habitats.
PLoS ONE, 2012
Oyster reefs are one of the most threatened marine habitats on earth, with habitat loss resulting from water quality degradation, coastal development, destructive fishing practices, overfishing, and storm impacts. For successful and sustainable oyster reef restoration efforts, it is necessary to choose sites that support long-term growth and survival of oysters. Selection of suitable sites is critically important as it can greatly influence mortality factors and may largely determine the ultimate success of the restoration project. The application of Geographic Information Systems (GIS) provides an effective methodology for identifying suitable sites for oyster reef restoration and removes much of the uncertainty involved in the sometimes trial and error selection process. This approach also provides an objective and quantitative tool for planning future oyster reef restoration efforts. The aim of this study was to develop a restoration suitability index model and reef quality index model to characterize locations based on their potential for successful reef restoration within the Mission-Aransas Estuary, Texas, USA. The restoration suitability index model focuses on salinity, temperature, turbidity, dissolved oxygen, and depth, while the reef quality index model focuses on abundance of live oysters, dead shell, and spat. Size-specific Perkinsus marinus infection levels were mapped to illustrate general disease trends. This application was effective in identifying suitable sites for oyster reef restoration, is flexible in its use, and provides a mechanism for considering alternative approaches. The end product is a practical decision-support tool that can be used by coastal resource managers to improve oyster restoration efforts. As oyster reef restoration activities continue at small and largescales, site selection criteria are critical for assisting stakeholders and managers and for maximizing long-term sustainability of oyster resources.
Accounting for Multiple Foundation Species in Oyster Reef Restoration Benefits
Many coastal habitat restoration projects are focused on restoring the population of a single foundation species to recover an entire ecological community. Estimates of the ecosystem services provided by the restoration project are used to justify, prioritize, and evaluate such projects. However , estimates of ecosystem services provided by a single species may vastly under-represent true provisioning, as we demonstrate here with an example of oyster reefs, often restored to improve estuarine water quality. In the brackish Chesapeake Bay, the hooked mussel Ischadium recurvum can have greater abundance and biomass than the focal restoration species, the eastern oyster Crassostrea virginica. We measured the temperature-dependent phyto-plankton clearance rates of both bivalves and their filtration efficiency on three size classes of phytoplankton to param-eterize an annual model of oyster reef filtration, with and without hooked mussels, for monitored oyster reefs and restoration scenarios in the eastern Chesapeake Bay. The inclusion of filtration by hooked mussels increased the filtration capacity of the habitat greater than 2-fold. Hooked mussels were also twice as effective as oysters at filtering picoplankton (1.5–3 í µí»m), indicating that they fill a distinct ecological niche by controlling phytoplankton in this size class, which makes up a significant proportion of the phyto-plankton load in summer. When mussel and oyster filtration are accounted for in this, albeit simplistic, model, restoration of oyster reefs in a tributary scale restoration is predicted to control 100% of phytoplankton during the summer months.
2016
Using a regression design that encompassed the continuum of oyster reef biomass density in Harris Creek, MD, from unrestored reefs to those restored reefs with the greatest oyster biomass, we examined finfish and crustacean utilization of these habitats. Of the eight sites studied, three had not been subject to any restoration activities and five had been planted in 2012 with juvenile oysters set on oyster shell. All sites were sampled in April, June, August, and October 2015. During each sampling period, we assessed abundance, total length and biomass of finfish and examined gut contents to assess the diets of selected finfish species. Of the species collected that were likely to use reefs as habitat or a foraging ground, only striped bass and white perch were sufficiently abundant to support robust statistical analyses. Regression analyses found no clear relationship between oyster biomass density and catch per unit effort, total length or biomass for striped bass or white perch. Analyses of the effects of sampling period and restoration status (restored versus non-restored sites) on fish utilization frequently found an effect of sampling period but rarely found
Estuaries and Coasts, 2008
An important ecological role ascribed to oysters is the transfer of materials from the water column to the benthos as they feed on suspended particles (seston). This ecosystem service has been often touted as a major reason for many oyster restoration efforts, but empirical characterization and quantification of seston removal rates in the field have been lacking. Changes in chlorophyll a (chl a) concentrations in the water column were measured in May 2005 and June 2006 in South Carolina using in situ fluorometry and laboratory analysis of pumped water samples taken upstream and downstream as water flowed over natural and constructed intertidal oyster reefs. Both methods gave similar results overall, but with wide variability within individual reef datasets. In situ fluorometer data logged at 10 to 30-s intervals for up to 1.3 h over eight different reefs (three natural and five constructed) showed total removal (or uptake) expressed as % removal of chl a ranging from −9.8% to 27.9%, with a mean of 12.9%. Our data indicate that restored shellfish reefs should provide water-quality improvements soon after construction, and the overall impact is probably determined by the size and density of the resident filter feeder populations relative to water flow characteristics over the reef. The measured population-level chl a removal was converted to mean individual clearance rates to allow comparison with previous laboratory studies. Although direct comparisons could not be made due to the small size of oysters on the study reefs (mean shell height, 36.1 mm), our calculated rates (mean, 1.21 L h −1) were similar to published laboratory measured rates for oysters of this size. However, the wide variability in measured removal by the oyster reefs suggests that individual oyster feeding rates in nature may be much more variable than in the laboratory. The proliferation of ecosystem-level models that simulate the impacts of bivalves on water quality based only on laboratory-feeding measurements underscores the importance of further research aimed at determining ecologically realistic feeding rates for oysters in the field. Because in situ methods provide many replicate measurements quickly, they represent a potentially powerful tool for quantifying the effects of oyster reefs, including all suspension-feeding taxa present, on water quality.
Marine Ecology Progress Series, 2019
Restoration of oyster reefs in coastal ecosystems may enhance fish and fisheries by providing valuable refuge and foraging habitat, but understanding the effects of restoration requires an improved understanding of fish habitat use and trophic dynamics, coupled with longterm (> 5 yr) monitoring of restored habitats. We evaluated the relationship between large (3−5 ha) restored subtidal oyster reefs and mobile estuarine fishes in the Lynnhaven River System (LRS), Virginia, more than 8 yr following reef construction. We compared the (1) diversity, (2) abundance, (3) size, (4) stomach fullness, (5) diet composition, and (6) daily consumption rate of fishes collected from restored oyster reefs with those from an area of unstructured, unrestored bottom, via experimental gill nets. We sampled monthly from April to October 2016 and conducted 24 h sampling in July and September 2016. Community composition was similar between habitats, dominated by spot Leiostomus xanthurus, Atlantic menhaden Brevoortia tyrannus, silver perch Bairdiella chrysoura, and Atlantic croaker Micropogonias undulatus. Abundance in reef habitat was significantly reduced relative to unstructured bottom, but the mean length of fishes collected from reefs was significantly greater than that of unstructured bottom. In addition, the estimated consumption rate of silver perch foraging in reef habitat significantly exceeded that of silver perch foraging in unstructured bottom. Nearly a decade post-restoration, restored reefs in the LRS are used by a similar assemblage as unrestored areas, but the manner of use differs by species and size. Considering a broad range of responses is necessary to evaluate the impacts of oyster restoration on mobile fishes.