Publications are in order by date and then further alphabetized by first author last name.

Marshes with and without sills protect estuarine shorelines from erosion better than bulkheads during a Category 1 hurricane

2014 Ocean & Coastal Management • Gittman, et al., UNC-Chapel Hill

Abstract

Acting on the perception that they perform better for longer, most property owners in the United States choose hard engineered structures, such as bulkheads or riprap revetments, to protect estuarine shorelines from erosion. Less intrusive alternatives, specifically marsh plantings with and without sills, have the potential to better sustain marsh habitat and support its ecosystem services, yet their shoreline protection capabilities during storms have not been evaluated. In this study, the performances of alternative shoreline protection approaches during Hurricane Irene (Category 1 storm) were compared by 1) classifying resultant damage to shorelines with different types of shoreline protection in three NC coastal regions after Irene; and 2) quantifying shoreline erosion at marshes with and without sills in one NC region by using repeated measurements of marsh surface elevation and marsh vegetation stem density before and after Irene. In the central Outer Banks, NC, where the strongest sustained winds blew across the longest fetch; Irene damaged 76% of bulkheads surveyed, while no damage to other shoreline protection options was detected. Across marsh sites within 25 km of its landfall, Hurricane Irene had no effect on marsh surface elevations behind sills or along marsh shorelines without sills. Although Irene temporarily reduced marsh vegetation density at sites with and without sills, vegetation recovered to pre-hurricane levels within a year. Storm responses suggest that marshes with and without sills are more durable and may protect shorelines from erosion better than the bulkheads in a Category 1 storm. This study is the first to provide data on the shoreline protection capabilities of marshes with and without sills relative to bulkheads during a substantial storm event, and to articulate a research framework to assist in the development of comprehensive policies for climate change adaptation and sustainable management of estuarine shorelines and resources in U.S. and globally.

Guidelines for evaluating performance of oyster habitat restoration

2015 Restoration Ecology • Baggett, et al., University of South Alabama, Dauphin Island Sea Lab, The Nature Conservancy, NOAA, UNC, VIMS, ets.

Abstract

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.

Geographic variation in intertital oyster reef properties and the influence of tidal prism

2015 Oceanog. • Byers, et al., UNC-Chapel Hill, University of Georgia, Northwestern University

Abstract

Physical-biological coupling helps structure aquatic communities, yet physical factors can vary widely across large, biogeographic scales. The eastern oyster (Crassostrea virginica) is an ecosystem engineer that creates intertidal reefs, filters water, promotes denitrification, stabilizes shorelines, and provides habitat throughout the inner waters of the U.S. South Atlantic Bight (SAB). We quantified physical variables (temperature, salinity, duration and depth of water inundation), oyster reef properties (slope, vertical relief), and oyster
recruitment, density, and biomass over a 1500 km scale across the SAB for one year. All oyster-level and many reef-level variables exhibited unimodal patterns with latitude that peaked in Georgia and South Carolina estuaries. Of the physical variables, salinity and duration of water inundation over reefs were similar across all sites, and temperature declined linearly with increasing latitude, except during summer when it had no relationship with latitude. Depth of water inundation over reefs was the only physical variable with a
prominent unimodal distribution that may explain the oyster’s biological responses. Similar durations of water inundation across all reefs coupled with higher water depths in the mid-latitude sites collectively indicate
that these sites experience higher flow velocity, energy and net water volume delivery per unit time. The resultant higher accumulation of oyster biomass and heightened reef structure in areas of higher tidal
energy emphasize that the physical forcing of the SAB (especially large cross-shelf gradients in tidal amplification) affects the biology of the eastern oyster, including its reef properties, with potential implications for community structure and ecosystem service delivery across a biogeographic scale.

A field test of the effects of mesopredators and landscape setting on juvenile oyster Crassostrea virginica consumption on intertital reefs

2015 Marine Biology • Carroll J.M., Marion J.P., Finelli C.M., UNC-Wilmington

Abstract

Oyster populations are often structured by both biotic interactions and abiotic stresses. Juvenile oysters, i.e., those most vulnerable to predation, face a wide range of predatory characteristics (size, mobility) such that predator identity might exert a strong influence on oyster populations. Likewise, oyster reef location, either as isolated patch reefs or saltmarsh-fringing reefs, can strongly influence the ecological processes impacting oyster populations. Therefore, this study sought to quantify the contribution of predator identity, in particular mesopredators, to oyster survival in the field, while also examining the role of landscape setting in predation. Using a multiple mesh size cage design, oyster survival was measured by excluding access to different groups of predators at both patch and fringing reef and reference sites in Hewlett’s Creek, Wilmington, North Carolina, in August/September 2013, while also monitoring settlement and recruitment at both reef locations from May to August 2013. The results indicated a significant cage by location interaction, indicating that the predator identity or modality was not the same across all sites. Despite this, at either reef location, oyster survival did not differ between 37-mm mesh cages, which allowed access only by mesopredators, and no-cage treatments, which allowed access to all predators, while survival was reduced by >20 % on fringing reefs relative to patch reefs. This study demonstrates the significant contribution of mesopredators, likely xanthid crabs, to oyster predation in the field at ambient predator densities and suggests that the differences in oyster abundance between patch and fringing reef locations are likely due to differential predation

Ocean acidification impairs crab and oyster foraging behavior

2015 Proc. R. Soc. B. • Dodd, et al., UNC-Chapel Hill, Northewestern University

Abstract

Anthropogenic elevation of atmospheric CO2 is driving global-scale ocean acidification, which consequently influences calcification rates of many marine invertebrates and potentially alters their susceptibility to predation. Ocean acidification may also impair an organism’s ability to process environmental and biological cues. These counteracting impacts make it challenging to predict how acidification will alter species interactions and community structure. To examine effects of acidification on consumptive and behavioural interactions between mud crabs (Panopeus herbstii) and oysters (Crassostrea virginica), oysters were reared with and without caged crabs for 71 days at three pCO2 levels. During subsequent predation trials, acidification reduced prey consumption, handling time and duration of unsuccessful predation attempt. These negative effects of ocean acidification on crab foraging behaviour more than offset any benefit to crabs resulting from a reduction in the net rate of oyster calcification. These findings reveal that efforts to evaluate how acidification will alter marine food webs should include quantifying impacts on both calcification rates and animal behaviour.

Development of a Matrix Tool for the Prediction of Vibrio Species in Oyster Harvested from North Carolina

2015 Applied and Environmental Microbiology • Freolich, et al., UNC-Chapel Hill, The North Carolina Department of Environmental and Natural Resources, Duke University

Abstract

The United States has federal regulations in place to reduce the risk of seafood-related infection caused by the estuarine bacteria Vibrio vulnificus and Vibrio parahaemolyticus. However, data to support the development of regulations have been generated in a very few specific regions of the nation. More regionally specific data are needed to further understand the dynamics of human infection relating to shellfish-harvesting conditions in other areas. In this study, oysters and water were collected from four oyster harvest sites in North Carolina over an 11-month period. Samples were analyzed for the abundances of total Vibrio spp., V.vulnificus, and V. parahaemolyticus; environmental parameters, including salinity, water temperature, wind velocity, and precipitation,were also measured simultaneously. By utilizing these data, preliminary predictive management tools for estimating the abundance of V. vulnificus bacteria in shellfish were developed. This work highlights the need for further research to elucidate the full suite of factors that drive V. parahaemolyticus abundance.

Measuring individuality in habitat use across complex landscape approaches, contraints, and implications for assessing resource specialization

2015 Oecologica • Frodie, et al., UNC-Chapel Hill, National Socio-Environmental Synthesis Center, Martine Science Center, Northwestern University NC State University, Gulf of Maine Research Institute

Abstract

Many mobile marine species are presumed to utilize a broad spectrum of habitats, but this seemingly generalist life history may arise from conspecifics specializing on distinct habitat alternatives to exploit foraging, resting/refuge, or reproductive opportunities. We acoustically tagged 34 red drum, and mapped sand, seagrass, marsh, or oyster (across discrete landscape contexts) use by each uniquely coded individual. Using 144,000 acoustic detections, we recorded differences in habitat use among red drum: proportional use of seagrass habitat ranged from 0 to 100 %, and use of oyster-bottom types also varied among fish. WIC/TNW and IS metrics (previously applied vis-à-vis diet specialization) consistently indicated that a typical red drum overlapped >70 % with population-level niche exploitation. Monte Carlo permutations
showed these values were lower than expected had fish drawn from a common habitat-use distribution, but longitudinal comparisons did not provide evidence of temporally consistent individuality, suggesting that differences among individuals were plastic and not reflective of true specialization. Given the range of acoustic detections we captured (from tens to 1,000s per individual), which are substantially larger sample sizes than in many diet studies, we extended our findings by serially reducing or expanding our data in simulations to evaluate samplesize effects. We found that the results of null hypothesis testing for specialization were highly dependent on sample size, with thresholds in the relationship between sample size and associated P-values. These results highlight opportunities and potential caveats in exploring individuality in habitat use. More broadly, exploring individual specialization in fine-scale habitat use suggests that, for mobile marine species, movement behaviors over shorter (≤weeks), but not longer (≥months), timescales may serve as an underlying mechanism for other forms of resource specialization.

Engineering away our natural defenses: an analysis of shoreline hardening in the US

2015 Ocean & Coastal Management • Gittman, et al., UNC-Chapel Hill, NOAA

Abstract

Rapid population growth and coastal development are primary drivers of marine habitat degradation. Although shoreline hardening or armoring (the addition of concrete structures such as seawalls, jetties, and groins), a
byproduct of development, can accelerate erosion and loss of beaches and tidal wetlands, it is a common practice globally. Here, we provide the first estimate of shoreline hardening along US Pacific, Atlantic, and Gulf of Mexico coasts and predict where future armoring may result in tidal wetland loss if coastal management practices remain unchanged. Our analysis indicates that 22 842 km of continental US shoreline – approximately 14% of the total US coastline – has been armored. We also consider how socioeconomic and physical factors relate to the pervasiveness of shoreline armoring and show that housing density, gross domestic product, storms, and wave height are positively correlated with hardening. Over 50% of South Atlantic and Gulf of Mexico coasts are fringed with tidal wetlands that could be threatened by future hardening, based on projected population growth, storm frequency, and an absence of coastal development restrictions.

Oyster Larvae Settle in Response to Habitat-Associated Underwater Sounds

2015 Marine Biology • Lillis, A., Egglston, D.B., Bohenstiehl, D.R. • N.C. State University

Abstract

Following a planktonic dispersal period of days to months, the larvae of benthic marine organisms must locate suitable seafloor habitat in which to settle and metamorphose. For animals that are sessile or sedentary as adults, settlement onto substrates that are adequate for survival and reproduction is particularly critical, yet represents a challenge since patchily distributed settlement sites may be difficult to find along a coast or within an estuary. Recent studies have demonstrated that the underwater soundscape, the distinct sounds that emanate from habitats and contain information about their biological and physical characteristics, may serve as broad-scale environmental cue for marine larvae to find satisfactory settlement sites. Here, we contrast the acoustic characteristics of oyster reef and off-reef soft bottoms, and investigate the effect of habitat-associated estuarine sound on the settlement patterns of an economically and ecologically important reef-building bivalve, the Eastern oyster (Crassostrea virginica). Subtidal oyster reefs in coastal North Carolina, USA show distinct acoustic signatures compared to adjacent off-reef soft bottom habitats, characterized by consistently higher levels of sound in the 1.5–20 kHz range. Manipulative laboratory playback experiments found increased settlement in larval oyster cultures exposed to oyster reef sound compared to unstructured soft bottom sound or no sound treatments. In field experiments, ambient reef sound produced higher levels of oyster settlement in larval cultures than did off-reef sound treatments. The results suggest that oyster larvae have the ability to respond to sounds indicative of optimal settlement sites, and this is the first evidence that habitat-related differences in estuarine sounds influence the settlement of a mollusk. Habitat-specific sound characteristics may represent an important settlement and habitat selection cue for estuarine invertebrates and could play a role in driving settlement and recruitment patterns in marine communities.

Maximizing oyster-reef growth supports green infrastructure with accelerating sea-level rise

2015 Scientific Reports • Ridge, et al., UNC-Chapel Hill, Northeastern University, The Nature Conservancy

Abstract

Within intertidal communities, aerial exposure (emergence during the tidal cycle) generates strong vertical zonation patterns with distinct growth boundaries regulated by physiological and external stressors. Forecasted accelerations in sea-level rise (SLR) will shift the position of these critical boundaries in ways we cannot yet fully predict, but landward migration will be impaired by coastal development, amplifying the importance of foundation species’ ability to maintain their position relative to rising sea levels via vertical growth. Here we show the effects of emergence on vertical oyster-reef growth by determining the conditions at which intertidal reefs thrive and the sharp boundaries where reefs fail, which shift with changes in sea level. We found that oyster reef growth is unimodal relative to emergence, with greatest growth rates occurring between 20–40% exposure, and zero-growth boundaries at 10% and 55% exposures. Notably, along the lower growth boundary (10%), increased rates of SLR would outpace reef accretion, thereby reducing the depth range of substrate suitable for reef maintenance and formation, and exacerbating habitat loss along developed shorelines. Our results identify where, within intertidal areas, constructed or natural oyster reefs will persist and function best as green infrastructure to enhance coastal resiliency under conditions of accelerating SLR.

Habitat context influences nitrogen removal by restored oyster reefs

2015 Marine Biology • Smyth, et al., UNC, Northeastern University

Abstract

Like many ecosystem functions in marine and terrestrial environments, nutrient processing varies dramatically over small spatial scales, making efforts to apply findings within and across ecosystems challenging. In estuaries, information on the influence of habitat context on sediment nutrient cycling is lacking even though this is an important estuarine function with high societal value.2. We collected triplicate intact sediment cores from restored oyster reefs located in different habitat contexts (adjacent to salt marshes, seagrass beds and mudflats), as well as salt marshes, seagrass beds and mudflats without reefs (controls). Sediment denitrification and fluxes of dissolved inorganic nitrogen were measured under ambient and experimentally elevated water column nitrate levels. 3. Under ambient nitrate, oyster reefs enhanced sediment denitrification by 18–275% over the controls, with highest rates of denitrification in the mudflat context. With experimentally elevated nitrate, the rate of denitrification was higher for oyster reefs compared to the controls in all contexts. This suggests that oyster reefs prime sediments to denitrify nitrate pulses by providing a labile carbon source for denitrifying bacteria. 4. There was a weak positive relationship between oyster density and denitrification under ambient nitrate concentrations and a positive relationship with denitrification that became negative beyond _2400 individuals m_2 with elevated nitrate concentrations. The effect of the oyster reef on sediment denitrification was most pronounced in the mudflat context, due to the absence of other structured habitats and higher oyster density, compared to the other two habitat contexts investigated.
The consistency of denitrification efficiency across the habitats and lack of difference between habitats with reefs and those without (controls) suggest oyster-mediated denitrification is an effective sink for nitrogen in coastal systems.6. Synthesis and applications. Our study indicates that oyster-mediated denitrification is dependent on the habitat context of the oyster reef, and variation in oyster density and the relative functional redundancy of oyster reefs where other structured habitats exist (e.g. seagrass
and salt marshes) may explain this pattern. Efforts to model and predict ecosystem services provided through oyster reef restoration such as the removal of anthropogenically derived nitrogen should incorporate how habitat context influences ecosystem functions

Differences in Abundances of Total Vibrio spp., V. vulnificus, and V. parahaemolyticus in Clams and Oysters in North Carolina

2016 Appl Environ Microbiol • Freolich, et al., UNC-Chapel Hill, UNC-Charlotte, N.C. Division of Marine Fisheries

Abstract

Filter feeding shellfish can concentrate pathogenic bacteria, including Vibrio vulnificus and Vibrio parahaemolyticus, as much as 100-fold from the overlying water. These shellfish, especially clams and oysters, are often consumed raw, providing a route of entry for concentrated doses of pathogenic bacteria into the human body. The numbers of foodborne infections with these microbes are increasing, and a better understanding of the conditions that might trigger elevated concentrations of these bacteria in seafood is needed. In addition, if bacterial concentrations in water are correlated with those in shellfish, then sampling regimens could be simplified, as water samples can be more rapidly and easily obtained. After sampling of oysters and clams, either simultaneously or separately, for over 2 years, it was concluded that while Vibrio concentrations in oysters and water were related, this was not the case for levels in clams and water. When clams and oysters were collected simultaneously from the same site, the clams were found to have lower Vibrio levels than the oysters. Furthermore, the environmental parameters that were correlated with levels of Vibrio spp. in oysters and water were found to be quite different from those that were correlated with levels of Vibrio spp. in clams.

Environmental Effect on elemental signatures in the shells of the Eastern Oyster, Crassostrea virginica

2016 Marine Ecology Progress Series • Kroll, et al., NC State University, UNC-Chapel Hill

Abstract

We evaluated the utility of geochemical tagging methods to discern larval connectivity among an invertebrate metapopulation within a large (~5000 km2) temperate estuary. Specifically, we examined how estuarine-scale gradients in temperatures (21° to 26.5°C), salinities (12.5 to 20 ppt), and trace metal concentrations (ambient, +16 ppb Mn and 0.16 ppb Pb, or +32 ppb Mn and 0.32 ppb Pb) affect Crassostrea virginica larval-shell signatures of Mn, Sr, Ba, and Pb in controlled mesocosms. We also utilized field-collected, newly settled oysters across Pamlico Sound, NC, USA, to explore signature variability among natural temperature and salinity gradients and examine the spatial resolution at which geochemical signatures can be used to discriminate between collection regions. Mesocosm experiments revealed environmentally and statistically significant interactive effects between temperature and salinity on elemental ratios in larval oyster shells, favoring higher Sr concentrations in cooler, fresher water, but no effects of these factors on Ba signatures. Mesocosm trials also showed increased Mn signatures in larval shell following from spiking mesocosms with Mn solutions; however, this relationship did not hold for Pb following analogous elemental spikes. Our field collections of recent settlers showed similar patterns of high Sr at relatively low salinities and temperatures, without clear environmental gradients for Ba. Overall, we found that across regional (35 km) spatial scales, environmental variables, such as salinity and temperature, can generate distinct multi-elemental signatures between putative natal sites. However, if sites are close together or located in similar environments, discrimination among sites appears greatly reduced. We suggest that geochemical tagging provides a promising approach for characterizing larval connectivity among subpopulations within whole-estuarine systems.

Metapopulation dynamics guide marine reserve network design: importance of connectivity

2016 Ecosphere • Puckett B.J., Eggleston D.B., NC State University

Abstract

The concepts of metapopulation persistence and source-sink dynamics are central and often untested tenets of marine reserve networks. Effective application of these concepts to marine reserves is limited by data on demographic rates within reserves and larval connectivity among reserves. Using a network of reserves established to restore eastern oyster (Crassostrea virginica) in Pamlico Sound, North Carolina, USA as our model system, we integrated empirically based demographic rates and regional hydrodynamic-based connectivity estimates within a metapopulation model to (1) evaluate the potential for the reserve network to function as a self-persistent oyster metapopulation, (2) determine the relative importance of demographics vs. connectivity on reserve source-sink dynamics, (3) assess the efficacy of stock enhancement in promoting metapopulation persistence, and (4) evaluate whether application of a Few Large or Several Small reserves—a modification of the Single Large or Several Small concept—promoted greater metapopulation retention of larvae within the reserve network (i.e., local larval retention within reserves + larval connectivity among reserves). The reserve network failed to function as a self-persistent metapopulation, despite exceptional demographic rates within reserves. When considering only larval supply from reserves, local retention and connectivity were insufficient to provide annual replacement (≥~0.25 recruits per adult). Accordingly, reserves contributed to the metapopulation primarily via production, not dispersal, of larvae and reserve source-sink dynamics were influenced more by demographics within reserves, particularly adult growth and survival, than larval connectivity among reserves. Addressing recruitment limitation via stock enhancement was not effective at augmenting projected metapopulation declines. Several small reserves initially promoted greater metapopulation retention of larvae than a few large reserves, however, as the number or area of reserves increased, metapopulation retention was equivalent among designs, suggesting that Few Large and Several Small reserves may be the best network design. Marine reserves can be an effective restoration tool for improving demographic rates within reserve boundaries, but designation of multiple reserves does not guarantee a functional reserve network metapopulation. Both demographics and larval connectivity are important considerations to successful application of metapopulation concepts to the design of reserve networks.

Living Shorelines Enhance Habitat Use

2016 Ecological Applications • Ashley R. Smyth, Michael F. Piehler, Jonathan H. Grabowski, UNC-Chapel Hill, NOAA

Abstract

Coastal ecosystems provide numerous services, such as nutrient cycling, climate change amelioration, and habitat provision for commercially valuable organisms. Ecosystem functions and processes are modified by human activities locally and globally, with degradation of coastal ecosystems by development and climate change occurring at unprecedented rates. The demand for coastal defense strategies against storms and sea-level rise has increased with human population growth and development along coastlines worldwide, even while that population growth has reduced natural buffering of shorelines. Shoreline hardening, a common coastal defense strategy that includes the use of seawalls and bulkheads (vertical walls constructed of concrete, wood, vinyl, or steel), is resulting in a “coastal squeeze” on estuarine habitats. In contrast to hardening, living shorelines, which range from vegetation plantings to a combination of hard structures and plantings, can be deployed to restore or enhance multiple ecosystem services normally delivered by naturally vegetated shores. Although hundreds of living shoreline projects have been implemented in the U.S. alone, few studies have evaluated their effectiveness  in sustaining or enhancing ecosystem services relative to naturally vegetated shorelines and hardened shorelines. We quantified the effectiveness of (1) sills with landward marsh (a type of living shoreline that combines marsh plantings with an offshore low-profile breakwater), (2) natural salt marsh shorelines (control marshes), and (3) unvegetated bulkheaded shores in providing habitat for fish and crustaceans (nekton). Sills supported higher abundances and species diversity of fishes than unvegetated habitat adjacent to bulkheads and even control marshes. Sills also supported higher cover of filter-feeding bivalves (a food resource and refuge habitat for nekton) than bulkheads or control marshes. These ecosystem-service enhancements were detected on shores with sills three or more years after construction, but not before. Sills provide added structure and may provide better refuges from predation and 38 greater opportunity to use available food resources for nekton than unvegetated bulkheaded shores or control marshes. Our study shows that unlike shoreline hardening, living shorelines can enhance some ecosystem services provided by marshes, such as provision of nursery habitat.
Coastal ecosystems provide numerous services, such as nutrient cycling, climate change amelioration, and habitat provision for commercially valuable organisms. Ecosystem functions and processes are modified by human activities locally and globally, with degradation of coastal ecosystems by development and climate change occurring at unprecedented rates. The demand for coastal defense strategies against storms and sea-level rise has increased with human population growth and development along coastlines worldwide, even while that population growth has reduced natural buffering of shorelines. Shoreline hardening, a common coastal defense strategy that includes the use of seawalls and bulkheads (vertical walls constructed of concrete, wood, vinyl, or steel), is resulting in a “coastal squeeze” on estuarine habitats. In contrast to hardening, living shorelines, which range from vegetation plantings to a combination of hard structures and plantings, can be deployed to restore or enhance multiple ecosystem services normally delivered by naturally vegetated shores. Although hundreds of living shoreline projects have been implemented in the U.S. alone, few studies have evaluated their effectiveness  in sustaining or enhancing ecosystem services relative to naturally vegetated shorelines and hardened shorelines. We quantified the effectiveness of (1) sills with landward marsh (a type of living shoreline that combines marsh plantings with an offshore low-profile breakwater), (2) natural salt marsh shorelines (control marshes), and (3) unvegetated bulkheaded shores in providing habitat for fish and crustaceans (nekton). Sills supported higher abundances and species diversity of fishes than unvegetated habitat adjacent to bulkheads and even control marshes. Sills also supported higher cover of filter-feeding bivalves (a food resource and refuge habitat for nekton) than bulkheads or control marshes. These ecosystem-service enhancements were detected on shores with sills three or more years after construction, but not before. Sills provide added structure and may provide better refuges from predation and 38 greater opportunity to use available food resources for nekton than unvegetated bulkheaded shores or control marshes. Our study shows that unlike shoreline hardening, living shorelines can enhance some ecosystem services provided by marshes, such as provision of nursery habitat.

Analysis of Spatiotemporal Genetic Variability in Eastern Oyster Crassostrea virginica (Gmelin, 1791) Mtdna 16S Sequences Among North Carolina Populations

2016 Appl Environ Microbiol • R.L. Varney, R. L., Sackett, R.E., Wilbur, A.E. UNC-Wilmington, UNC-Charlotte, Naugatuck Valley Community College

Abstract

Spatial and temporal genetic structure of the eastern oyster Crassostrea virginica was examined along the coast of North Carolina (NC); utilizing a fragment of the mitochondrial large (16S) ribosomal subunit gene sequence known to distinguish three regional haplotypes in C. virginica—North Atlantic, South Atlantic, and Gulf of Mexico. Significant geographic genetic structure was identified among all populations studied, with little temporal genetic variation observed over the 9-y sampling period. The results are consistent with those of previous studies analyzing geographic variation in mitochondrial DNA16S sequence data, which revealed a genetic discontinuity between North and South Atlantic oyster assemblages along the NC Coast. The increased geographic resolution and duration of sampling in this study revealed a sustained significant shift in genetic composition between Pamlico Sound populations and southern NC populations of C. virginica. These results suggest that a prolonged or persistent barrier impacting larval dispersal or post settlement survival exists between these regions limiting gene flow between North and South Atlantic oyster assemblages.

Guidelines for evaluating performance of oyster habitat restoration should include tidal emersion: reply to Baggett et al.

2016 Society for Ecological Restoration • Walles, et al. • Royal Netherlands Institute for Sea Research, UNC-Chapel Hill

Abstract

Baggett et al. (2015) identified a set of three universal environmental variables to be monitored for evaluating all oyster habitat restoration projects: salinity, temperature, and dissolved oxygen. Perhaps evidencing a bias toward subtidal reefs, this set of parameters omits another first-order environmental factor, tidal emersion. Intertidal oyster reefs can be the dominant reef habitat in estuaries, with clear zonation in oyster performance across the intertidal exposure gradient. Therefore, we propose to include tidal emersion as a fourth universal environmental parameter when designing and evaluating oyster restoration projects to better encompass the whole environmental spectrum along which reefs occur.