The influence of resident adults on recruitment: a comparison to settlement

For species recruiting into established sessile communities, the adult colonies and individuals already present form a significant part of the environment and have the potential to alter both larval settlement rates and post-settlement mortality. Settlement rates can be reduced by predation on larvae, by the removal or addition of substratum space, or by stimulation or prohibition of larvae from settling on adjacent substratum. Once attached, the recruiting individual can still be influenced by predation or overgrowth by residents, by the added physical structure for firmer attachment, or by being camouflaged from motile predators. To examine those processes by which residents affect recruitment we exposed experimental substrata with three densities of adults of a single species at a site in eastern Long Island Sound, USA for a 1-wk period. Seven different species of common invertebrates were used in nine separate experiments. The major effect of most resident species was the usurpation of space and the restricting of recruitment to adjacent unoccupied areas. This was particularly true for resident ascidians and bryozoans, but less so for barnacles and oysters. In fact several species recruited in higher densities on or next to oysters and barnacles. Comparison to 1-day settlement experiments indicated that the encrusting ascidian species Diplosoma and possibly Botryllus reduced recruitment relative to settlement, probably by overgrowing newly-settled individuals. However, in the presence of most resident species, recruitment patterns were not greatly different from settlement patterns, indicating that the effects of the attached community on recruitment may result from influences on settlement.     

Oyster Reef Restoration in the Northern Gulf of Mexico: Effect of Artificial Substrate and Age on Nekton and Benthic Macroinvertebrate Assemblage Use

In the northern Gulf of Mexico (GOM), reefs built by eastern oysters, Crassostrea virginica, provide critical habitat within shallow estuaries, and recent efforts have focused on restoring reefs to benefit nekton and benthic macroinvertebrates. We compared nekton and benthic macroinvertebrate assemblages at historic, newly created (<5 years) and old (>6 years) shell and rock substrate reefs. Using crab traps, gill‐nets, otter trawls, cast nets, and benthic macroinvertebrate collectors, 20 shallow reefs (<5 m) in the northern GOM were sampled throughout the summer of 2011. We compared nekton and benthic assemblage abundance, diversity and composition across reef types. Except for benthic macroinvertebrate abundance, which was significantly higher on old rock reefs as compared to historic reefs, all reefs were similar to historic reefs, suggesting created reefs provide similar support of nekton and benthic assemblages as historic reefs. To determine refuge value of oyster structure for benthic macroinvertebrates compared to bare bottom, we tested preferences of juvenile crabs across depth and refuge complexity in the presence and absence of adult blue crabs (Callinectes sapidus). Juveniles were more likely to use deep water with predators present only when provided oyster structure. Provision of structural material to support and sustain development of benthic and mobile reef communities may be the most important factor in determining reef value to these assemblages, with biophysical characteristics related to reef location influencing assemblage patterns in areas with structure; if so, appropriately locating created reefs is critical.     

Predator-prey dynamics between recently established stone crabs (Menippe spp.) and oyster prey (Crassostrea virginica)

Range expansion and population establishment of individual species can have significant impacts on previously established food webs and predator-prey dynamics. The stone crab (Menippe spp.) is found throughout southwestern North Atlantic waters, from North Carolina through the Gulf of Mexico and the Central American Caribbean, including the Greater Antilles. Recent observations suggest that stone crabs have become better established on certain oyster reefs in North Carolina than in the early 1900s when they we first observed in NC. To assess the predatory impact of stone crabs on oysters, we (1) quantified stone crab densities on subtidal oyster reefs in Pamlico Sound, NC using scuba surveys, and (2) conducted laboratory predation experiments to assess the functional response of stone crabs to varying densities of oysters. We then (3) analyzed previously unpublished functional response data on another important oyster predator, the mud crab Panopeus herbstii. Finally, we (4) compared and contrasted potential predatory impacts of stone, mud and blue crabs (Callinectes sapidus). The functional response data and analyses for both stone crabs and mud crabs were consistent with a type II functional response. Mud crabs, on a m² basis, inflicted the highest proportional mortality on oysters over a 24 hour period, followed by stone and then blue crabs. Proportional mortality did not vary significantly with oyster size; however, relatively small and large oysters were consumed disproportionately less than medium-sized oysters, likely due to the mechanical inability of stone crabs to handle small oysters, and the inability to crush large oysters. Although stone crabs appear to be established in Pamlico Sound at densities equivalent to densities in other systems such as the U.S. Florida Panhandle, their predatory activities on oysters are not expected to have as significant a negative impact on oyster populations compared to other resident predators such as mud crabs.     

Salt marsh shoreline geomorphology influences the success of restored oyster reefs and use by associated fauna

Restoration is increasingly implemented as a strategy to mitigate global declines in biogenic habitats, such as salt marshes and oyster reefs. Restoration efforts could be improved if we knew how site characteristics at landscape scales affect the ecological success of these foundation species. In this study, we determined how salt marsh shoreline geomorphologies (e.g. with variable hydrodynamic energy, fetch, erosion rates, and slopes) affect the success of restored intertidal oyster reefs, as well as how fauna utilize restored reefs and forage along marsh habitats. We constructed oyster reefs along three marsh shoreline geomorphologies in May 2012: 1) “creek” (small‐fetch, gradual‐sloped shoreline), “ramp” (large‐fetch, gradual‐sloped shoreline), and “scarp” (large‐fetch, steep‐sloped shoreline). Following recruitment, oyster spat density was greatest on ramp reefs; however, 2 years later, the highest adult oyster densities were found on creek reefs. Total nekton and blue crab catch rates in trawl nets were highest in the creek, while piscivore catch rates in gill nets were highest along the scarp shoreline. We found no difference in predation on snails in the salt marsh behind constructed reef and nonconstructed reference sites, but there were more snails consumed in the creek shoreline, which corresponded with the distribution of their major predator—blue crabs. We conclude that oyster reef construction was most successful for oysters in small‐fetch, gradual‐sloped, creek environments. However, nekton abundance did not always follow the same trends as oyster density, which could suggest constructed reefs may offer similar habitat‐related functions (prey availability and refuge) already present along existing salt marsh borders.     

Effects of time and harvest on genetic diversity of natural and restored oyster reefs

Oysters serve as keystone species and ecosystem engineers in estuaries due to their fundamental role of providing services to the surrounding environment and to humans. Globally, however, oysters have precipitously declined in numbers over the last century. To remedy this drastic decrease, many coastal areas have initiated oyster restoration projects. In the Indian River Lagoon (IRL) of Florida, where oyster loss was primarily the result of recreational boat wake dislodgment, researchers have put in place a unique method to supplement natural recruitment of oysters. This method consists of deploying stabilized shell attached to mesh mats. Larval oysters thus have substrate on which to settle and three‐dimensional reef habitats have been reestablished in historical footprints. This restoration project has proven to be successful, shown by 9 years of data collection on growth, recruitment, and survivability. In this study, we sought to determine the length of time required for newly restored oyster reefs to reach equivalent levels of genetic diversity as undisturbed, natural (reference) oyster reefs. Additionally, we determined if recreational harvesting impacted the genetic diversity of these reference reefs. Using nine microsatellite loci, we found that restored oyster reefs accumulated as much genetic diversity as natural reefs as quickly as 1 month after stabilized shells were deployed. We likewise found that harvesting did not impact genetic diversity in oyster reefs in the IRL. These results are encouraging, and are a valuable addition to understanding the importance of oyster reef restoration on the ecosystem.     

Physical constraints on the foraging ecology of a predatory snail

We studied the effects of aerial exposure and high summer temperatures on the southern oyster drill ( Stramonita haemastoma ), feeding on the American oyster, Crassostrea virginica . In the laboratory, oyster drill feeding rates and growth were highest at 25 and 30°C, some mortality occurred at 35°C, all snails died at 40 and 45°C, and the 28-day LC 50 was 35.7°C. In a second experiment where both water temperature (25 vs . 33°C) and aerial exposure were varied, only simulated tidal exposure lowered oyster drill feeding and growth rates. In field cage experiments, oyster drills had reduced feeding rates and growth at intertidal sites, but snail growth rates increased in late summer with warmer water temperature. We therefore conclude that aerial exposure, not high temperature, is the major factor limiting oyster drill feeding and growth in intertidal oyster reefs. Field experiments with partial cages also suggested that ambient predation rates were much higher at a subtidal than at a nearby intertidal site. Because southern oyster drills have depressed feeding, growth, and possibly lower fitness in intertidal oyster reefs during the summer, this reduced predation risk may provide a refuge for intertidal oysters.     

Settlement Dynamics of the Encrusting Epibenthic Macrofauna in Two Creeks of the Caeté Mangrove Estuary (North Brazil)

The epibenthic encrusting fauna of 2 creeks of the Caeté mangrove estuary, northern Brazil, was studied over a 13 month period using collectors fixed at 2.5 and 3.5 m above the creek bottom and in which upper and lower sides of ceramic and wooden panels were used as settlement substrates. The number of individuals of the most abundant organisms (barnacles, oysters and mussels) settling per panel was determined each month, for each substrate type, panel orientation and height above creek bottom. The barnacle, Fistulobalanus citerosum has a peak settlement period during the wet season whereas both peaks in the numbers of settlers of the oyster Crassostrea rhizophorae were recorded during the dry season and such discrete temporal patterns in settlement have also been observed for barnacles and oysters in other mangroves and estuaries. In contrast to other studies, settlement of the mussel Mytella falcata was generally low during the study period and may be related to over-exploitation of stocks in the region. Overall, settler density was usually greater on the underside of ceramic panels close to the creek bottom, similar to results of other studies of epibenthic settlement in diverse habitats.     

Comparing the invasibility of experimental "reefs" with field observations of natural reefs and artificial structures

Natural systems are increasingly being modified by the addition of artificial habitats which may facilitate invasion. Where invaders are able to disperse from artificial habitats, their impact may spread to surrounding natural communities and therefore it is important to investigate potential factors that reduce or enhance invasibility. We surveyed the distribution of non-indigenous and native invertebrates and algae between artificial habitats and natural reefs in a marine subtidal system. We also deployed sandstone plates as experimental 'reefs' and manipulated the orientation, starting assemblage and degree of shading. Invertebrates (non-indigenous and native) appeared to be responding to similar environmental factors (e.g. orientation) and occupied most space on artificial structures and to a lesser extent reef walls. Non-indigenous invertebrates are less successful than native invertebrates on horizontal reefs despite functional similarities. Manipulative experiments revealed that even when non-indigenous invertebrates invade vertical "reefs", they are unlikely to gain a foothold and never exceed covers of native invertebrates (regardless of space availability). Community ecology suggests that invertebrates will dominate reef walls and algae horizontal reefs due to functional differences, however our surveys revealed that native algae dominate both vertical and horizontal reefs in shallow estuarine systems. Few non-indigenous algae were sampled in the study, however where invasive algal species are present in a system, they may present a threat to reef communities. Our findings suggest that non-indigenous species are less successful at occupying space on reef compared to artificial structures, and manipulations of biotic and abiotic conditions (primarily orientation and to a lesser extent biotic resistance) on experimental "reefs" explained a large portion of this variation, however they could not fully explain the magnitude of differences.     

Relative nursery function of oyster, vegetated marsh edge, and nonvegetated bottom habitats for juvenile white shrimp Litopenaeus setiferus

Shallow estuarine habitats, including vegetated marsh edge (VME), oyster reefs (oyster), and nonvegetated soft bottom (NVB), provide important functions for estuarine resident and estuarine-dependent species. A paucity of information exists concerning relative nursery value of these habitats for juvenile fishes and invertebrates. In Grand Bay, MS and Weeks Bay, AL, National Estuarine Research Reserves (NERR), this study evaluated the potential of the three habitats to serve as nurseries by quantifying habitat-specific density, size, growth, and survival of juvenile white shrimp Litopenaeus setiferus. Drop sampling in Oct 2003 and Jul 2004 indicated that white shrimp density was significantly greater in oyster and VME when compared with adjacent NVB. No significant difference occurred in density between oyster and VME. Significantly larger shrimp were collected in NVB, intermediate-sized shrimp were collected in oyster, and smaller shrimp were collected in VME. Using field enclosures to study growth of juvenile white shrimp we found significantly higher growth in oyster when compared with NVB and VME. Predator mesocosm experiments indicated that when blue crabs were used as predators, white shrimp juveniles experienced significantly higher survival rates in VME and NVB when compared with oyster. Our study suggests that juvenile white shrimp may select for oyster over NVB because of higher food availability and not necessarily for refuge needs from predation by blue crabs. In addition, juvenile habitat needs may shift with individual growth, indicating that the relative nursery value of a habitat is not inclusive for all juvenile sizes. Similar to VME, oyster provides an important function in the juvenile stages of white shrimp and should be examined further as a potential nursery habitat.     

Oyster reefs as natural breakwaters mitigate shoreline loss and facilitate fisheries

Shorelines at the interface of marine, estuarine and terrestrial biomes are among the most degraded and threatened habitats in the coastal zone because of their sensitivity to sea level rise, storms and increased human utilization. Previous efforts to protect shorelines have largely involved constructing bulkheads and seawalls which can detrimentally affect nearshore habitats. Recently, efforts have shifted towards "living shoreline" approaches that include biogenic breakwater reefs. Our study experimentally tested the efficacy of breakwater reefs constructed of oyster shell for protecting eroding coastal shorelines and their effect on nearshore fish and shellfish communities. Along two different stretches of eroding shoreline, we created replicated pairs of subtidal breakwater reefs and established unaltered reference areas as controls. At both sites we measured shoreline and bathymetric change and quantified oyster recruitment, fish and mobile macro-invertebrate abundances. Breakwater reef treatments mitigated shoreline retreat by more than 40% at one site, but overall vegetation retreat and erosion rates were high across all treatments and at both sites. Oyster settlement and subsequent survival were observed at both sites, with mean adult densities reaching more than eighty oysters m(-2) at one site. We found the corridor between intertidal marsh and oyster reef breakwaters supported higher abundances and different communities of fishes than control plots without oyster reef habitat. Among the fishes and mobile invertebrates that appeared to be strongly enhanced were several economically-important species. Blue crabs (Callinectes sapidus) were the most clearly enhanced (+297%) by the presence of breakwater reefs, while red drum (Sciaenops ocellatus) (+108%), spotted seatrout (Cynoscion nebulosus) (+88%) and flounder (Paralichthys sp.) (+79%) also benefited. Although the vertical relief of the breakwater reefs was reduced over the course of our study and this compromised the shoreline protection capacity, the observed habitat value demonstrates ecological justification for future, more robust shoreline protection projects.     

Inducible defenses in Olympia oysters in response to an invasive predator

The prey naiveté hypothesis suggests that native prey may be vulnerable to introduced predators because they have not evolved appropriate defenses. However, recent evidence suggests that native prey sometimes exhibit induced defenses to introduced predators, as a result of rapid evolution or other processes. We examined whether Olympia oysters (Ostrea lurida) display inducible defenses in the presence of an invasive predator, the Atlantic oyster drill (Urosalpinx cinerea), and whether these responses vary among oyster populations from estuaries with and without this predator. We spawned oysters from six populations distributed among three estuaries in northern California, USA, and raised their offspring through two generations under common conditions to minimize effects of environmental history. We exposed second-generation oysters to cue treatments: drills eating oysters, drills eating barnacles, or control seawater. Oysters from all populations grew smaller shells when exposed to drill cues, and grew thicker and harder shells when those drills were eating oysters. Oysters exposed to drills eating other oysters were subsequently preyed upon at a slower rate. Although all oyster populations exhibited inducible defenses, oysters from the estuary with the greatest exposure to drills grew the smallest shells suggesting that oyster populations have evolved adaptive differences in the strength of their responses to predators. Our findings add to a growing body of literature that suggests that marine prey may be less likely to exhibit naiveté in the face of invasive predators than prey in communities that are more isolated from native predators, such as many freshwater and terrestrial island ecosystems.     

THE EFFECT, ON OYSTER SPATFALL, OF CONTROLLING BARNACLE SETTLEMENT WITH DDT

During the summer of 1955 experiments were made with DDT to control barnacle fouling of oyster spat collectors. Results showed that effective control of barnacles on artificial collectors doubled the yield of oyster spat. Shell cultch treated in the same way gave less conclusive results, partly because of the poor spatfall experienced.
Oyster spat on treated artificial collectors were approximately 40% bigger, at the end of 2 1/2 months, than those on controls. Evidence from shells, however, indicated that DDT initially inhibited the growth of oyster spat. Apparently spat become stunted in natural conditions, because they are unable to compete effectively for food with the dense barnacle populations. Competition amongst barnacles themselves also causes stunting.
The dense population of Elminius modestus on the east coast oyster grounds may have a long-term effect on both the yield and growth of oysters.     

Predators reduce abundance and species richness of coral reef fish recruits via non-selective predation

Predators have important effects on coral reef fish populations, but their effects on community structure have only recently been investigated and are not yet well understood. Here, the effect of predation on the diversity and abundance of young coral reef fishes was experimentally examined in Moorea, French Polynesia. Effects of predators were quantified by monitoring recruitment of fishes onto standardized patch reefs in predator-exclosure cages or uncaged reefs. At the end of the 54-day experiment, recruits were 74% less abundant on reefs exposed to predators than on caged ones, and species richness was 42% lower on reefs exposed to predators. Effects of predators varied somewhat among families, however, rarefaction analysis indicated that predators foraged non-selectively among species. These results indicate that predation can alter diversity of reef fish communities by indiscriminately reducing the abundance of fishes soon after settlement, thereby reducing the number of species present on reefs.     

Barnacle reattachment: a tool for studying barnacle adhesion

Standard approaches for measuring adhesion strength of fouling organisms use barnacles, tubeworms or oysters settled and grown in the field or laboratory, to a measurable size. These approaches suffer from the vagaries of larval supply, settlement behavior, predation, disturbance and environmental stress. Procedures for reattaching barnacles to experimental surfaces are reported. When procedures are followed, adhesion strength measurements on silicone substrata after 2 weeks are comparable to those obtained using standard methods. Hydrophilic surfaces require reattachment for 2-4 weeks. The adhesion strength of barnacles in reattachment assays was positively correlated to results obtained from field testing a series of experimental polysiloxane fouling-release coatings (r = 0.89). The reattachment method allows for precise barnacle orientation, enabling the use of small surfaces and the potential for automation. The method enables down-selection of coatings from combinatorial approaches to manageable levels for definitive field testing. Reattachment can be used with coatings that combine antifouling and fouling-release technologies.     

Traces of Naticid Predation on the Gryphaeid Oyster Pycnodonte dissimilaris: Epifaunal Drilling of Prey in the Paleocene

Traces of drilling predation by naticid gastropods were observed on 51 valves of the free-lying, semi-infaunal oyster Pycnodonte dissimilaris (Gryphaeidae) from the Paleocene Hornerstown Formation, in New Jersey. Stereotypic behavior of the predator is indicated by the highly constrained placement of drill holes, 94% of which are centrally located on the oyster shells. Predator—prey mismatches in size, involving small predators that drilled through the upper valves of relatively large oysters, are documented by comparison of outer borehole diameter, as an index of predator size, with the sizes of the oyster shells. Results of this analysis suggest that at least some prey were drilled epifaunally, as they were too large to be manipulated and buried by the predator. This indicates, together with reports of epifaunal drilling by living naticids, that such behavior is geographically and stratigraphically more widespread in the Naticidae than has previously been acknowledged. This in turn suggests that epifaunal drilling of prey is a plesiomorphic, opportunistic mode of behavior, conserved in the evolution of the Naticidae, that has permitted subsequent escalation or expansion in range of naticid foraging from a more narrowly defined infaunal paradigm into exposed intertidal refugia.     

Habitat formation prevails over predation in influencing fouling communities

Coastal human‐made structures, such as marinas and harbors, are expanding worldwide. Species assemblages described from these artificial habitats are novel relative to natural reefs, particularly in terms of the abundance of nonindigenous species (NIS). Although these fouling assemblages are clearly distinctive, the ecosystem functioning and species interactions taking place there are little understood. For instance, large predators may influence the fouling community development either directly (feeding on sessile fauna) or indirectly (feeding on small predators associated with these assemblages). In addition, by providing refuges, habitat complexity may modify the outcome of species interactions and the extent of biotic resistance (e.g., by increasing the abundance of niche‐specific competitors and predators of NIS). Using experimental settlement panels deployed in the field for 2.5 months, we tested the influence of predation (i.e., caging experiment), artificial structural complexity (i.e., mimics of turf‐forming species), and their interactions (i.e., refuge effects) on the development of sessile and mobile fauna in two marinas. In addition, we tested the role of biotic complexity—arising from the habitat‐forming species that grew on the panels during the trial—on the richness and abundance of mobile fauna. The effect of predation and artificial habitat complexity was negligible, regardless of assemblage status (i.e., native, cryptogenic, and nonindigenous). Conversely, habitat‐forming species and associated epibionts, responsible for biotic complexity, had a significant effect on mobile invertebrates (richness, abundance, and community structure). In particular, the richness and abundance of mobile NIS were positively affected by biotic complexity, with site‐dependent relationships. Altogether, our results indicate that biotic complexity prevails over artificial habitat complexity in determining the distribution of mobile species under low predation pressure. Facilitation of native and non‐native species thus seems to act upon diversity and community development: This process deserves further consideration in models of biotic resistance to invasion in urban marine habitats.     

牡蛎礁生境：海岸带可持续发展的潜在碳汇

牡蛎礁生境是指由聚集的牡蛎和其他生物及环境堆积形成的复合生态系统,其固碳和储碳潜力巨大,在海岸带生态系统中发挥着重要的作用。然而,目前对牡蛎礁生境碳源与汇的认识仍存在不足,主要在于牡蛎钙化和呼吸作用都释放CO₂,而碳源与汇的评估忽视了钙化、同化和沉积过程带来的整体碳汇价值及牡蛎礁生态系统功能带来的碳汇效应。因此,有必要重新认识牡蛎礁生境的碳汇价值。一方面,牡蛎礁生境的碳源和碳汇需要从牡蛎礁自身的整体碳循环中进行评估,包括牡蛎礁系统中的沉积、钙化、呼吸作用及侵蚀、再悬浮和再矿化作用; 另一方面,牡蛎礁生态系统服务引起的碳汇效应需从牡蛎礁的生态系统服务价值角度进行评估,将生态系统服务价值及碳价值进行关联,从而纳入碳汇核算体系。从实现海岸带可持续增汇角度出发,综述了牡蛎礁生境中碳的源与汇;阐述了容易被人们忽视的微生物在牡蛎礁生境碳汇中的作用;以保护和生态修复为目的,进一步提出可实现牡蛎礁生境最大潜在碳汇的策略,以期为实现海洋负排放及践行"国家双碳战略"提供理论和技术支撑。     

Crab shell-crushing predation and gastropod architectural defense

The shell-breaking behavior of the crabs Ozius verreauxii Saussure 1853 and Eriphia squamata, Stimpson 1859 from the Bay of Panama is described. The master claws of both these crabs are well designed for breaking shells. Small shells, relative to the size of a crab predator, are crushed by progressively breaking off larger segments of a shell's apex, while larger shells are peeled by inserting a large dactyl molar into the aperture of a shell and progressively chipping away the lip of the shell.

Heavy gastropod shells are shown to be less vulnerable to crab predators than lighter shells, and narrow shell apertures and axial shell sculpture are demonstrated to be architectural features that deter crab predation. The incidence of architectural features which deter crab predation appears to be higher for smaller gastropod species than for larger gastropods which are too large for most crab predators. Large fish predators prey upon both gastropods and shell-crushing crabs. To avoid fish predators, both these prey groups seek refuge under rocks when covered by the tide. Fish predation thus appears to enforce a close sympatry between smaller gastropods and their crab predators.     

Natural cultch type influences habitat preference and predation,but not survival,in reef‐associated species

A shared origin with fresh and dredged cultch and availability via mining have made fossil cultch a commonly used reef restoration substrate. However, important differences in shape and size between whole‐shell cultch and fossil cultch may impact the complexity of reefs constructed from these materials. To determine if these differences may impact the development of restored reefs, we quantified the interstitial space each cultch type provides and constructed reef mesocosms to measure (1) the immediate effects of exposure to each cultch type on mortality of blue crab (Callinectes sapidus) and pink shrimp (Farfantepenaeus duorarum); (2) the tendency of crab, shrimp, and Florida crown conch (Melongena corona) to be found on habitats composed of each substrate type and their position within each in split‐substrate mesocosms; and (3) the influence of cultch type on predation of Eastern oysters (Crassostrea virginica) by crabs and conch. Aggregation of fossil cultch contains more shells and provides less interstitial space than an equivalent volume of whole‐shell cultch. Although immediate mortality following deployment was low and did not differ among cultch types, we found that all species were more likely to be found on fresh cultch over fossil cultch in choice experiments and used each habitat type differently. Cultch type also impacted the size of oysters consumed by crabs in short‐term feeding trials. The structure and traits of habitats created by various materials should be added to the growing list of issues considered when natural communities are to be restored in oyster reefs and other environments.     

Evaluating Intertidal Oyster Reef Development in South Carolina Using Associated Faunal Indicators

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.