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Localized contamination from research-related activities and its effects on macrofauna communities in the marine environment were investigated at Palmer Station, a medium-sized Antarctic research station. Relatively low concentrations of polycyclic aromatic hydrocarbons (PAHs; 32–302 ng g-1) and total petroleum hydrocarbons (TPHs; 0.9–8.9 μg g-1) were detected in sediments adjacent to the sewage outfall and pier, where most human activities were expected to have occurred, and at even lower concentrations at two seemingly reference areas (PAHs 6–30 ng g-1, TPHs 0.03–5.1 μg g-1). Elevated concentrations of PAHs in one sample taken in one reference area (816 ng g-1) and polychlorinated biphenyls (353 ng g-1) and dichloro-diphenyl-trichloroethane (3.2 and 25.3 ng g-1) in two samples taken adjacent to the sewage outfall indicate spatial heterogeneity of localized sediment contamination. Limpet (Nacella concinna) tissues collected adjacent to Palmer Station had high concentrations of PAHs, copper, lead, zinc and several other metals relative to outlying islands. Sediment and limpet tissue contaminant concentrations have decreased since the early 1990s following the Bahía Paraíso spill. Natural sediment characteristics affected macrofaunal community composition more than contamination adjacent to Palmer Station, presumably because of the low overall contamination levels.

The lower Rio Grande is a river-dominated estuary that serves as the border between Texas, USA, and Tamaulipas, Mexico. River estuaries encompass the section of the river influenced by tidal exchange with the Gulf of Mexico, but the connection with the Rio Grande is intermittent and can be temporarily open or closed. During the 4.8-year study period, the river mouth was closed 30% of the time, mostly during average or dry climatic conditions, with the temporary closing of the river mouth being linked to hydrology. When the Rio Grande estuary is closed, salinity is low (1.5 psu compared to 4.8 psu when open), nitrate plus nitrite are low (4.4 μM compared to 31.5 μM when open), and ammonium is high (9.6 μM compared to 4.3 μM when open), but chlorophyll is similar (20 μg/L compared to 21 μg/L when open). Benthic macrofaunal abundance and biomass are higher when the river mouth is closed: 16,700 individuals m−2 and 3.3 g m−2 compared to 8800 individuals m−2 and 2.4 g m−2 when the Rio Grande river mouth is open. Benthic macrofaunal community structure is divided into two groups: chironomid larvae and Oligochaeta dominated when the river mouth was closed, whereas polychaetes Mediomastus ambiseta and Streblospio benedicti dominated when the river mouth was open. The implications of these results for managing freshwater flows are that the open and closed conditions each have a characteristic benthic macrofaunal community that is strongly influenced by system hydrology.

International audience

Ten benthic fauna taxa in a polluted marine area adjacent to McMurdo Station, Antarctica were deemed to be potential biomonitors because PCBs, DDTs, PAHs, copper, lead and/or zinc in their tissues were significantly higher than in tissues of taxa living in reference areas (p 0.05). Concentrations of PCBs and DDT were highest in Trematomus (fish). Total PAH concentrations were highest in Alcyonium antarcticum (soft coral), Isotealia antarctica (anemone) and L. elliptica. Copper and lead concentrations were highest in Laternula elliptica (bivalve) and Flabegraviera mundata (polychaete), and lowest in Trematomus and Parbolasia corrugatus (nemertean). However, copper concentrations were even higher in the asteroids Perknaster fuscus antarcticus, Odontaster validus and Psilaster charcoti. Bioaccumulation factors for different species were highest for PCBs and DDT, and lowest for lead. Bioaccumulation of some contaminants are likely prevalent in benthic taxa at McMurdo Station, but concentrations are usually low relative to human consumption standards.

Assessments based on monetary valuation of ecosystem services have been increasingly used as a tool to highlight the connection between ecosystems and society. The dissemination of this approach is leading to difficulties and ambiguities related to the use of such assessments in the socio-political realm. Such limits can be stressed using the case study of intertidal bare mudflats. These coastal habitats indeed provide many ecological functions—several being related to the high production of benthic microalgae—but also remain poorly known for some other aspects. The major users of these habitats (i.e. oyster farmers) are still unaware about the trophic role of benthic microalgae, limiting contingent valuation survey methods. Moreover, economic valuation cannot take into account the potentials of mudflats (i.e. undescribed functions) like positive feedbacks related to shellfish farming and provision of bioactive compounds. The lack of physical boundaries in marine systems also strongly reduces the effectiveness of assessments. Lastly, there are concerns that monetary valuation can lead to a commodification of the nature or to the economization of the environment (e.g. appropriation of the environment by users, creation of artificial thresholds). The evaluation of the functions of a socio-ecosystem should not only be restricted to a monetary assessment of its ecosystem services, as this framework may be more reductive than integrative. Some other descriptors—not based on currencies—should be used for ecosystem description.

Oyster reef restoration has become a principal strategy for ameliorating the loss of natural Crassostrea virginica populations and increasing habitat provision. In 2014, a large‐scale, high‐relief, 23‐ha subtidal C. virginica reef was restored at the historically productive Half Moon Reef in Matagorda Bay, TX, using concrete and limestone substrates. Encrusting and motile fauna were sampled seasonally until 17 months postrestoration at the restored reef and at adjacent unrestored sites. Restored oysters developed rapidly and were most abundant 3 months postrestoration, with subsequent declines possibly due to interacting effects of larval settlement success on new substrate versus post‐settlement mortality due to competitors and predators. Oyster densities were 2× higher than in a restored oyster population in Chesapeake Bay that was reported to be the largest reestablished metapopulation of native oysters in the world. Resident fauna on the restored reef were 62% more diverse, had 433% greater biomass, and comprised a distinct faunal community compared to unrestored sites. The presence of three‐dimensional habitat was the most important factor determining resident faunal community composition, indicating that substrate limitation is a major hindrance for oyster reef community success in Texas and other parts of the Gulf of Mexico. There were only minor differences in density, biomass, and diversity of associated fauna located adjacent (13 m) versus distant (150 m) to the restored reef. The two substrate types compared had little influence on oyster recruitment or faunal habitat provision. Results support the use of reef restoration as a productive means to rebuild habitat and facilitate faunal enhancement.

Human activities and regional-scale climate variability drive changes in the ecology of coastal and marine ecosystems. Ecological restoration has emerged as a best-management practice to combat habitat degradation and restore lost ecological functions. However, relatively short project monitoring timeframes have limited our understanding of the effects of interannual climate cycles on water quality and restoration dynamics. We collected measurements on a 23-ha oyster reef constructed in the Gulf of Mexico to determine the relationship between El Niño Southern Oscillation (ENSO)-driven climate variability and local salinity patterns, and to evaluate the effects of this climate variability and salinity on oyster population dynamics and faunal community composition over a medium-term (five-year) timeframe. The role of ENSO-driven climate variability on local salinity patterns (primarily from changes in precipitation and evaporation) and faunal dynamics was investigated using the Oceanic Niño Index (ONI). Salinity was negatively correlated with ONI with an approximately 4-month lag. Higher ONI values (El Niño periods) were followed by reductions in salinity, increases in oyster recruitment and density, and reductions in resident motile fauna density and species richness. Lower ONI values (La Niña periods) had higher and less variable salinities, and higher areal coverage of restoration substrates by large oysters. ENSO-driven salinity reductions in the second year after reef construction coincided with a shift in resident motile faunal community composition that was maintained despite a second strong salinity reduction in year 5. Our results indicate that it is important to expand the typical monitoring timeframes to at least five years so that resource managers and restoration practitioners can better understand how both short-term environmental variability and longer-term climate cycles can affect the outcomes of restoration actions.

Biogenic reefs provide important ecological functions and services to coastal and marine environments, supplying high levels of biodiversity, providing refuge and foraging habitat, and supporting fisheries. Serpulid reefs are a relatively uncommon habitat in coastal ecosystems globally that provide habitat for a diverse community of organisms, and have become a target for conservation and management efforts due to habitat degradation and loss. Baffin Bay, Texas, USA, is known for exceptionally productive commercial and recreational fisheries that are thought to be supported by Serpulid reef benthic macrofauna, particularly during regular periods of hypersalinity. This study compared the functioning of Serpulid reef habitats with nearby soft sediment areas using quantitative faunal and food web analyses. Serpulid reefs support a unique benthic macrofaunal community with 191 times greater abundance, 97 times greater biomass, and twice the number of species than in soft sediments. In contrast to soft-sediment macrofauna, Serpulid reef macrofaunal abundance and biomass were not correlated with any measured water quality variables. Isotope compositions of both suspension and deposit-feeding macrofauna from both habitats (i.e., Serpulid reefs and soft sediments) were close to organic matter from the sediment, demonstrating connectivity and the importance of primary production in the sediment to both habitat types. Abundant macrofauna inhabiting Serpulid reefs likely serve as an important food source for sport fish and other higher trophic-level fauna, particularly in hypersaline periods when soft-sediment macrobenthic food resources are scarce. Given the substantial loss of Baffin Bay’s Serpulid reef habitat compared to historic levels, conservation actions may be warranted to protect and restore Serpulid habitat and food resources. The results of this study can be used to increase the success of such efforts.

The eastern oyster, Crassostrea virginica, is a foundation species within US Gulf of Mexico (GoM) estuaries that has experienced substantial population declines. As changes from management and climate are expected to continue to impact estuarine salinity, understanding how local oyster populations might respond and identifying populations with adaptations to more extreme changes in salinity could inform resource management, including restoration and aquaculture programs. Wild oysters were collected from four estuarine sites from Texas [Packery Channel (PC): 35.5, annual mean salinity, Aransas Bay (AB): 23.0] and Louisiana [Calcasieu Lake (CL): 16.2, Vermilion Bay (VB): 7.4] and spawned. The progeny were compared in field and laboratory studies under different salinity regimes. For the field study, F1 oysters were deployed at low (6.4) and intermediate (16.5) salinity sites in Alabama. Growth and mortality were measured monthly. Condition index and Perkinsus marinus infection intensity were measured quarterly. For the laboratory studies, mortality was recorded in F1 oysters that were exposed to salinities of 2.0, 4.0, 20.0/22.0, 38.0 and 44.0 with and without acclimation. The results of the field study and laboratory study with acclimation indicated that PC oysters are adapted to high-salinity conditions and do not tolerate very low salinities. The AB stock had the highest plasticity as it performed as well as the PC stock at high salinities and as well as Louisiana stocks at the lowest salinity. Louisiana stocks did not perform as well as the Texas stocks at high salinities. Results from the laboratory studies without salinity acclimation showed that all F1 stocks experiencing rapid mortality at low salinities when 3-month oysters collected at a salinity of 24 were used and at both low and high salinities when 7-month oysters collected at a salinity of 14.5 were used.

An increase in oyster aquaculture as a sustainable method of shellfish production is one response to overharvest and degradation of natural oyster reefs over the past century. Successful aquaculture production requires determining the environmental conditions optimal for oyster growth. In this study, the salinity, temperature, chlorophyll a concentration and the growth of Crassostrea virginica were monitored at four locations within the Mission-Aransas Estuary, Texas (USA), a shallow subtropical estuary influenced by relatively low freshwater inflow. Mean growth of the oyster shell (0.205 mm d–1 and 0.203 g d–1) and soft tissues (3.447 mg d–1) was highest when salinity was low (mean = 15.5) and chlorophyll a concentration was high (8.4 μg l–1). Oyster growth also varied temporally with periods of spawning. In low-inflow estuaries such as the Mission-Aransas Estuary, oyster farms should be sited close to river mouths so that oysters can benefit from freshwater inflows and lower salinities.

Using field and laboratory studies, we provide evidence of adaptation to local salinity regimes in the progenies of US Gulf of Mexico eastern oysters from estuaries differing substantially in annual mean salinity. Determining specific adaptations of oysters to local environmental conditions is important for conservation, restoration and the expanding aquaculture industry., The eastern oyster, Crassostrea virginica, is a foundation species within US Gulf of Mexico (GoM) estuaries that has experienced substantial population declines. As changes from management and climate are expected to continue to impact estuarine salinity, understanding how local oyster populations might respond and identifying populations with adaptations to more extreme changes in salinity could inform resource management, including restoration and aquaculture programs. Wild oysters were collected from four estuarine sites from Texas [Packery Channel (PC): 35.5, annual mean salinity, Aransas Bay (AB): 23.0] and Louisiana [Calcasieu Lake (CL): 16.2, Vermilion Bay (VB): 7.4] and spawned. The progeny were compared in field and laboratory studies under different salinity regimes. For the field study, F1 oysters were deployed at low (6.4) and intermediate (16.5) salinity sites in Alabama. Growth and mortality were measured monthly. Condition index and Perkinsus marinus infection intensity were measured quarterly. For the laboratory studies, mortality was recorded in F1 oysters that were exposed to salinities of 2.0, 4.0, 20.0/22.0, 38.0 and 44.0 with and without acclimation. The results of the field study and laboratory study with acclimation indicated that PC oysters are adapted to high-salinity conditions and do not tolerate very low salinities. The AB stock had the highest plasticity as it performed as well as the PC stock at high salinities and as well as Louisiana stocks at the lowest salinity. Louisiana stocks did not perform as well as the Texas stocks at high salinities. Results from the laboratory studies without salinity acclimation showed that all F1 stocks experiencing rapid mortality at low salinities when 3-month oysters collected at a salinity of 24 were used and at both low and high salinities when 7-month oysters collected at a salinity of 14.5 were used.

Quantifying and comparing stocks of oysters (Crassostrea virginica) within and among estuaries across the Gulf of Mexico is difficult because the sampling equipment used is either inconsistent among studies, or inefficient. In Texas, USA, stock assessments of oyster populations are made using an oyster dredge, which is an inefficient sampling tool. We compared sampling densities estimated by oyster dredges with more accurate estimates taken by diver-quadrat samples to determine a dredge efficiency rate. Our calculated efficiency rate (0.125) was negatively affected by the number of dead oysters, and the number and volume of total oysters in an area, but not affected by sediment grain size, water quality, and other oyster metrics. The dredge efficiency rate calculated in this study can be applied to past and future dredge-collected oyster quantity data to provide more realistic estimates of oyster densities and allow more accurate stock assessments and comparisons among studies and regions.

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.

The Baffin Bay estuary is a hypersaline system in the Gulf of Mexico that supports an important recreational and commercial fishery for black drum Pogonias cromis, a benthic predator. Seasonal measurements of water quality variables, benthic macrofauna densities and biomass, and determination of P. cromis food sources using stomach-content and stable-isotope analyses were carried out to determine how P. cromis food sources change with water quality and how this may affect P. cromis diet. Gut-content analysis indicated P. cromis selectively consumed bivalves Mulinia lateralis and Anomalocardia auberiana. Isotope compositions demonstrated that P. cromis relied on these benthic food resources produced in the Baffin Bay estuary year-round. Biomass and densities of these bivalves were influenced by changes in water quality variables, particularly salinity and dissolved oxygen. Thus, this paper demonstrates the relationship between water quality variables, benthic macrofauna, and their use as food resources by a carnivorous fish species, and emphasizes the need for integrated assessments when studying the effects of water quality on ecosystem function. Holistic approaches such as these can provide important information for management and conservation of fishery resources and can improve predictions of ecosystem response to climate variability.

Recently, greater interest in the resilience of coastal habitat ecosystem services in the northern Gulf of Mexico has emerged due in part to an expansion of mangroves into areas previously dominated by salt marshes. To operationalize coastal wetland ecosystem services for decision-making, there is a need to clarify how salt marshes and mangroves function in this region. The goal of this research is to operationalize blue carbon (carbon stored in coastal habitats) within the Mission-Aransas National Estuarine Research Reserve, TX by documenting what we know about blue carbon within the study area, identifying data gaps and future research needs, and using available knowledge to inform management and decision-making within the Reserve. Our research shows that there is a lack of data within the Reserve on mangrove aboveground biomass, belowground biomass and soil carbon and on salt marsh soil carbon. There is also a dearth of information on wetland carbon sequestration and emission rates within the Reserve, making it challenging to inform management and develop a market for blue carbon.

Recent research revealing the extent of marine habitat degradation has ignited a surge of restoration efforts globally. Restoration of estuarine habitats became a priority in the United States with the Estuary Restoration Act (ERA) of 2000. In the present study, a synthesis of data from the National Estuaries Restoration Inventory (NERI), developed in response to ERA requirements to track and disseminate project data, was conducted in order to analyze U.S. oyster reef restoration efforts. From 2000–2011, more than $45 million was invested in 187 projects to restore over 150 ha of oyster reef habitat, with projects most heavily concentrated in the Chesapeake Bay area and Florida Gulf coast. Trends over time indicate that projects are being implemented at larger scales, increasing from an average of less than 0.4 ha in 2000 to over 1 ha on average in 2011. Costs per unit decreased from an average of more than $2.1 million per ha in 2000 to just over $500,000 per ha in 2011. However, our analysis confirms one major problem hindering the field of restoration ecology: a lack of monitoring data or project-specific assessments of success. Habitat restoration has become an increasingly common effort in the policy sector, and gaps identified through this analysis can help inform future policy making and implementation. Better facilitation of data dissemination and further research on economies of scale in restoration projects are two key areas for improvement. As the field of restoration ecology continues to grow, it is critical that both new and current restoration practitioners, scientists, and decision-makers are able to learn from past projects and apply that collective knowledge to future restoration efforts.

Understanding the effects of freshwater inflow on estuarine fish habitat use is critical to the sustainable management of many coastal fisheries. The Baffin Bay Complex (BBC) of south Texas is typically a reverse estuary (i.e., salinity increases upstream) that has supported many recreational and commercial fisheries. In 2012, a large proportion of black drum (Pogonias cromis) landed by fishers were emaciated, leading to concerns about the health of this estuary. In response to this event and lacking data on black drum spatial dynamics, a 2-year acoustic telemetry study was implemented to monitor individual-based movement and seasonal distribution patterns. Coupled with simultaneous water quality monitoring, the relationship between environmental variables and fish movement was assessed under reverse and “classical” estuary conditions. Acoustic monitoring data suggested that the BBC represents an important habitat for black drum; individuals exhibited site fidelity to the system and were present for much of the year. However, under reverse estuary conditions, fish summertime distribution was constrained to the interior of the BBC, where food resources are limited (based on recent benthic sampling), with little evidence of movement across the system. Out of eight environmental variables used to model fish movement using multiple linear regression, the only significant variable was salinity, which exhibited a negative relationship with movement rate. These findings suggest that prolonged periods of hypersalinity, which are detrimental to other euryhaline species due to increased osmoregulatory costs, reduce black drum distribution patterns and can limit the species’ access to benthic habitats supporting abundant prey resources.

The eastern oyster, Crassostrea virginica, provides critical ecosystem services and supports valuable fishery and aquaculture industries in northern Gulf of Mexico (nGoM) subtropical estuaries where it is grown subtidally. Its upper critical thermal limit is not well defined, especially when combined with extreme salinities. The cumulative mortalities of the progenies of wild C. virginica from four nGoM estuaries differing in mean annual salinity, acclimated to low (4.0), moderate (20.0), and high (36.0) salinities at 28.9 °C (84 °F) and exposed to increasing target temperatures of 33.3 °C (92 °F), 35.6 °C (96 °F) or 37.8 °C (100 °F), were measured over a three-week period. Oysters of all stocks were the most sensitive to increasing temperatures at low salinity, dying quicker (i.e., lower median lethal time, LT50) than at the moderate and high salinities and resulting in high cumulative mortalities at all target temperatures. Oysters of all stocks at moderate salinity died the slowest with high cumulative mortalities only at the two highest temperatures. The F1 oysters from the more southern and hypersaline Upper Laguna Madre estuary were generally more tolerant to prolonged higher temperatures (higher LT50) than stocks originating from lower salinity estuaries, most notably at the highest salinity. Using the measured temperatures oysters were exposed to, 3-day median lethal Celsius degrees (LD50) were estimated for each stock at each salinity. The lowest 3-day LD50 (35.1–36.0 °C) for all stocks was calculated at a salinity of 4.0, while the highest 3-day LD50 (40.1–44.0 °C) was calculated at a salinity of 20.0.

Improved waste management at McMurdo Station, Antarctica beginning in the 1980s has been followed by decreases in polycyclic aromatic hydrocarbon (PAH) and metal contamination in the adjacent marine sediments. However, determining the effect of the decreased contamination on marine ecological indicators (macrobenthic fauna) is confounded by concurrent changes in climate cycles and other physical forces. Between 2000 and 2013, there was a decrease in concentrations of some contaminants including mercury, copper, organochlorines, and PAHs in marine sediments adjacent to McMurdo Station. PAH concentrations in Winter Quarters Bay decreased an order of magnitude from 2000/2003 to 2012/2013 and were within an order of magnitude of reference area concentrations by 2013. Macrobenthic communities did not indicate any sign of recovery and have not become more similar to reference communities over this same period of time. Temporal changes in macrobenthic community composition during the study period had higher correlations with climatic and sea ice dynamics than with changes in contaminant concentrations. The Interdecadal Pacific Oscillation climatic index had the highest correlation with macrobenthic community composition. The Antarctic Oscillation climatic index, maximum ice extent and other natural environmental factors also appear to influence macrobenthic community composition. Despite large improvements in environmental management at McMurdo Station, continuing environmental vigilance is necessary before any noticeable improvement in ecological systems is likely to occur. The effects of climate must be considered when determining temporal changes in anthropogenic effects in Antarctica. Maintaining long-term monitoring of both contaminants and ecological indicators is important for determining the localized and global influences of humans on Antarctica, which will have implications for the whole planet.

A limited supply of oyster shell for restoration practices has prompted investigations of alternative substrates used in construction of artificial oyster reefs. The success of oyster reef restoration projects is increasingly focused not only on oyster densities, but also on habitat provisioning for associated fauna. A subtidal oyster reef complex (0.24 km2) was restored in the Mission-Aransas Estuary, Texas, U.S.A., in July 2013 using replicated mounds of concrete, limestone, river rock, and oyster shell substrates. Oyster and reef-associated fauna characteristics were quantified quarterly for 15 months, using sampling trays that were deployed 3 months after construction. The highest densities of oyster spat occurred 9 months after tray deployment (July 2014, 1,264/m2), whereas juvenile oyster densities increased throughout the study period to 283/m2. Concrete (1,022/m2) and limestone (939/m2) supported the highest number of oysters over all dates. Oyster shell (1,533/m2) and concrete (1,047/m2) substrates supported the highest densities of associated motile fauna. Faunal diversity (Hill's N1) did not vary by substrate material, but did show seasonal variation. A simple benefit–cost ratio was used to indicate the localized monetary value for each of the substrates. Oyster shell and concrete substrates returned the highest benefit–cost ratio for motile fauna, while concrete yielded the highest benefit–cost ratio for oyster abundance. Incorporating benefit–cost ratios in restoration planning will allow practitioners to better integrate substrate-specific ecological values with economic considerations and project goals to maximize return on restoration investments.

The goal of the present study was to identify the potential changes in ecosystem service values provided by wetlands in Galveston Bay, Texas, USA, under the Intergovernmental Panel on Climate Change (IPCC) A1B max (0.69 m) sea level rise scenario. Built exclusively upon the output produced during the Sea Level Affecting Marshes Model 6 (SLAMM 6) exercise for the Galveston Bay region, this study showed that fresh marsh and salt marsh present a steady decline from 2009 (initial condition) to 2100. Fresh marsh was projected to undergo the biggest changes, with the loss of approximately 21% of its extent between 2009 and 2100 under the A1B max scenario. The percentages of change for salt marsh were less prominent at approximately 12%. This trend was also shown in the values of selected ecosystem services (disturbance regulation, waste regulation, recreation, and aesthetics) provided by these habitats. An ordinary least squares regression was used to calculate the monetary value of the selected ecosystem services provided by salt marsh and fresh marsh in 2009, and in 2050 and 2100 under the A1B max scenario. The value of the selected services showed potential monetary losses in excess of US$40 million annually in 2100, compared to 2009 for fresh marsh and more than $11 million for salt marsh. The estimates provided here are only small portions of what can be lost due to the decrease in habitat extent, and they highlight the need for protecting not only built infrastructure but also natural resources from sea level rise. Integr Environ Assess Manag 2017;13:431-443. © 2016 SETAC.

Fossil fuel extraction in the Gulf of Mexico currently involves the use of approximately 2000 active oil and gas production platforms. These artificial structures provide a number of ecological functions including habitat provision for epibenthic invertebrates and production of food and refuge for a variety of fish species. To mitigate the loss of habitat when active platforms are decommissioned, Rigs-to-Reefs programs maintain existing communities by removing the upper 26 m of platform structure and converting upper and lower portions into artificial reefs. We examined the epibenthic communities of two standing platforms at 5 m and 30 m depths and three reefed platforms at 30 m depths. A combination of stable isotope and community analysis was used to assess the structure and food web functioning of epibenthic communities among these site-types. Reefed platforms (30 m) supported communities with similar food web structure as 5 m and 30 m standing platform communities. However, community composition in standing platform and reefed platform sites at 30 m differed from those of standing platform sites at 5 m depths. Results indicate that, although loss of shallow water habitat associated with platform reefing may diminish some aspects of biodiversity, reefed platforms support similar fundamental ecological functions as standing platforms in the Gulf of Mexico. Thus, the current reefing practice of removal of the upper 26 m of the structure does not substantially influence the functionality of these systems, and the retained structure maintains beneficial habitat for epibenthic communities.

More than four decades of alkalinity and pH data (late 1960s to 2010) from coastal bays along the northwestern Gulf of Mexico were analyzed for temporal changes across a climatic gradient of decreasing rainfall and freshwater inflow, from northeast to southwest. The majority (16 out of 27) of these bays (including coastal waters) showed a long-term reduction in alkalinity at a rate of 3.0-21.6 μM yr(-1). Twenty-two bays exhibited pH decreases at a rate of 0.0014-0.0180 yr(-1). In contrast, a northernmost coastal bay exhibited increases in both alkalinity and pH. Overall, the two rates showed a significant positive correlation, indicating that most of these bays, especially those at lower latitudes, have been experiencing long-term acidification. The observed alkalinity decrease may be caused by reduced riverine alkalinity export, a result of precipitation decline under drought conditions, and freshwater diversion for human consumption, as well as calcification in these bays. A decrease in alkalinity inventory and accompanying acidification may have negative impacts on shellfish production in these waters. In addition, subsequent reduction in alkalinity export from these bays to the adjacent coastal ocean may also decrease the buffer capacity of the latter against future acidification.

Crassostrea virginica (the Eastern or American oyster) bioaccumulates pollutants from the water column, and therefore, its tissues can be used as bioindicators of past and present estuarine health. In this pilot project, we decided to investigate whether its tissues would be a suitable medium for toxicity testing using tissues from a variety of southern Texas locations of known and suspected anthropogenically impacted and unimpacted areas. We also conducted toxicity tests on sediments adjacent to oyster reefs using standard protocols for sediment toxicity. We tested the toxicity of tissues and sediments on the luminescent bacteria Vibrio fischeri, whose bioassays are commonly referred to by the trade name Microtox®. Microtox tests are quick, relatively inexpensive and sensitive to a range of contaminants. Evidence from this preliminary study suggests that conducting toxicity tests on oyster tissues may predict localized contamination better than when conducting toxicity tests on subtidal sediment. The refinement of these methods to use oyster tissues to detect contamination may be especially useful for environmental impact studies and/or studies where rapid and inexpensive information is needed.

Habitat reconstruction is commonly employed to restore degraded estuarine habitats and lost ecological functions. In this study, we use a combination of stable isotope analyses and macrofauna community analysis to compare the ecological structure and function between a recently constructed Spartina alterniflora salt marsh and a natural reference habitat over a 2-year period. The restored marsh was successful in providing habitat for economically and ecologically important macrofauna taxa; supporting similar or greater density, biomass, and species richness to the natural reference during all but one sampling period. Stable isotope analyses revealed that communities from the natural and the restored marshes relied on a similar diversity of food resources and that decapods had similar trophic levels. However, some generalist consumers (Palaemonetes spp. and Penaeus aztecus) were more 13C-enriched in the natural marsh, indicating a greater use of macrophyte derived organic matter relative to restored marsh counterparts. This difference was attributed to the higher quantities of macrophyte detritus and organic carbon in natural marsh sediments. Reduced marsh flooding frequency was associated with a reduction in macrofaunal biomass and decapod trophic levels. The restored marsh edge occurred at lower elevations than natural marsh edge, apparently due to reduced fetch and wind-wave exposure provided by the protective berm structures. The lower elevation of the restored marsh edge mitigated negative impacts in sampling periods with low tidal elevations that affected the natural marsh. The results of this study highlight the importance of considering sediment characteristics and elevation in salt marsh constructions.

Oyster reefs host complex food webs, as their three-dimensional biogenic structure provides habitat for a diverse range of invertebrates and fish. Oyster reefs have suffered severe degradation due to anthropogenic activities. Restoration projects aim to mitigate this habitat loss. We compared the development of a restored subtidal oyster reef to that of a natural reef for 29 months by assessing (1) community metrics (e.g., biomass, diversity), (2) the stable isotope composition of food sources and consumers, and (3) biomass-weighted isotopic diversity indices. A clear shift in restored reef community composition occurred 12–15 months after restoration, moving from a community dominated by opportunistic species to a more diverse and evenly distributed community, similar to that of the natural reef. Consumer stable isotope values indicated that the restored reef community was supported by similar food resources and had similar food chain length as the natural reef community by 5-month post-restoration. However, biomass-weighted isotopic diversity indices indicated that the magnitude of the main trophic pathways and characteristics of food web complexity in the restored reef did not recover to natural reef levels until 12–15 months after construction. The functional recovery of the restored reef community was driven by the homogenization of biomass distribution among trophic compartments as oysters and top predators increasingly colonized the reef. Results indicate that oyster reef restoration can support food web functions like those provided by natural reefs. We also demonstrate the importance of combining food web and community structure information in the study of ecological functioning.

Eastern oysters (Crassostrea virginica) in Gulf of Mexico estuaries create complex reefs and provide important habitat for fish and crustaceans. Oyster reefs have suffered historic losses due to overharvest, disease, and degraded water quality, and recent efforts have focused on restoring reefs to benefit nekton populations. Oyster shell is the preferred substrate for oyster reef restoration, but as a consequence of its limited supply, a variety of alternative substrates are being used. We used field experiments to quantify the effects of substrate type (concrete, porcelain, limestone, river rock, and oyster shell) on oyster recruitment, growth, and nekton habitat use in St. Charles Bay, TX. After 4 months, oyster spat recruitment density, nekton density and community structure were similar across substrate types—and analogous to those on natural reefs—but differed from samples collected on bare sediment. To determine refuge value of the alternative substrates, we tested mud crab (Panopeidae) prey mortality with and pinfish (Lagodon rhomboides) or blue crab (Callinectes sapidus) predators. Prey mortality was similar across substrate types for both predators, and was significantly lower than no substrate and bare sand controls. Alternative substrates can provide important structural materials to support the development of oyster populations and nekton assemblages, and may be used to promote sustainable management of oyster reef resources via restoration.

Characterizing density patterns of fish and crustaceans across estuarine habitat types can provide useful information regarding their relative value. The oyster reef complex within Sabine Lake Estuary is the largest known in the United States with no record of commercial harvest, and it presents a unique opportunity to understand the habitat value of an unfished reef system in comparison with adjacent estuarine habitats. High abundances of relatively large oysters with complex formations were observed throughout the 2-y study period. Average densities of fish and crustaceans were 6 times greater at the marsh edge than the nonvegetated shallow habitats, and 40 times greater than both the oyster reef and nonvegetated deep habitats. Low faunal densities observed in the oyster reef habitat may be the result of spatial configuration and connectivity to surrounding habitats, collection limitation resulting from its large vertical relief (>1 m) and complex 3-dimensional structure, or habitat selection resulting from water depth. Because the majority of crustaceans and resident and transient fish were observed within the marsh edge and nonvegetated shallow habitats, it is difficult to determine whether oyster reefs within Sabine Lake Estuary provide essential habitats for these species. Although low densities of organisms were observed in the oyster reef habitat, multivariate analysis indicates that the unfished reef supports a unique community of fish and crustaceans. Results provide a valuable baseline for future conservation, restoration, and management actions as we seek to understand more completely and to protect important estuarine habitat types.

Ecological restoration has become a widely recognized tool to ameliorate the effects of habitat loss. Half Moon Reef, once a highly-productive 2 km2 Crassostrea virginica oyster reef in Matagorda Bay, Texas, was harvested to depletion in the early 20th century. In 2014, a 0.23 km2 reef complex was created using limestone and concrete substrates to restore oyster populations—one of the largest contiguous oyster reef restoration efforts in the U.S. In the three years post-construction, two large freshwater inflow events provided a unique opportunity to determine the effects of prolonged salinity reductions (

International audience; South Texas has a semi-arid climate with a large interannual variability of freshwater inflows. This study sought to define how changes in freshwater inflow affect the composition, quantity and quality of suspended particulate organic matter (SPOM) in a South Texas estuary: the Mission-Aransas estuary. The study was implemented 1.5 months after a large rain event in September 2010 and continued for 10 months of drought conditions. The composition of SPOM originating from rivers, the Gulf of Mexico and the estuary were determined using stable isotopes (δ 13 C, δ 15 N and δ 34 S). The quantity and quality of SPOM were assessed using organic carbon content, chlorophyll a concentrations and C/chl a ratios. Our results demonstrated that autochthonous phytoplankton was the dominant component of SPOM in the Mission-Aransas estuary during droughts. Benthic organic matter from local primary producers (i.e., seagrass, salt marsh plants, benthic microalgae) did not influence SPOM composition, either as fresh material or as detritus. A comparison with a positive estuary (i.e., Sabine-Neches estuary, TX) indicates that decreases in freshwater inflow may lead to decreases of terrestrial organic matter inputs and to increase the ratio of autochtonous phytoplanktonic material in SPOM. Highlights-Phytoplankton dominate particulate organic matter in the Mission-Aransas estuary.-Benthic organic matter does not influence particulate organic matter composition.-Organic matter drained by rivers during minor rain events is of very poor quality.

The aim of this study was to compare the impact of different freshwater inflow volumes on benthic communities and water column dynamics in different estuary classes. Benthic and water column spatial dynamics were contrasted in lagoons (with no direct inflow sources), tidal rivers that empty directly into the Gulf of Mexico, and bar-built bay systems (with direct inflow sources) along the Texas (USA) coast to determine the role of inflow in regulating ecosystem structure and function. Chlorophyll-a and nutrient concentrations were inversely correlated with salinity and were thus highest in the river systems, but lowest in lagoons. All Texas estuary types studied have conservative mixing for silicate and ammonium but are sinks for nitrite plus nitrate and phosphate. Macrobenthic production (abundance and biomass) was lowest in rivers and highest in lagoons. Diversity was low in estuaries with salinities between 1 and 17, but increased with salinities of up to 30, before decreasing in hypersaline conditions. Macrofaunal community structure divided the estuaries into two groups. The first group represented polyhaline communities and contained lagoons (East Matagorda, Matagorda, Christmas, and South Bays). The second group represented oligo-mesohaline community characteristics and contained the secondary bays (Lavaca Bay and Cedar Lakes) and rivers (San Bernard River, Brazos River, and the Rio Grande). The implications of these results for managing freshwater flows is that altered hydrology can change the character of estuarine systems regardless of their classification as bays, lagoons, or tidal rivers.

A 2-year period with flood versus drought conditions provided the opportunity to examine the effects of flood disturbance on subtidal eastern oyster Crassostrea virginica biology and population dynamics in a south Texas estuary. Oysters were sampled monthly in 2007 and 2008 to examine the impacts of changing environmental conditions on oyster populations. Oysters were also examined quarterly for the presence of Perkinsus marinus. Filtration rates were calculated as a function of oyster size, temperature, salinity, and total suspended solids. Flood events in 2007 caused temporary reductions in salinity and were associated with reductions in oyster abundance, spat settlement, disease levels (weighted prevalence and percent infection), and filtration rates. Oyster populations had generally recovered within 1 year’s time—the oysters were younger and smaller but were just as abundant as pre-flood levels. The rapid return of oysters to pre-flood abundance levels is attributed in part to the ability of oysters in Gulf coast estuaries to spawn multiple times in a single season and in part to their relatively high growth rates. Although flood disturbance may temporarily reduce or destroy oyster populations, the ability of the Mission–Aransas Estuary to retain freshwater pulses within the system and maintain low salinities that are unfavorable for predators and disease can facilitate oyster population recovery. Episodic flood events appear to play a critical role in promoting long-term oyster population maintenance in the Mission–Aransas Estuary. The response of oysters to changing environmental conditions over the short term provides some insights into the potential long-term effects of changing climate.

Freshwater inflow is an important source of physical variability in estuaries. Effects of water flow are dynamic, and it is impossible to sample all conditions as they vary over space and time. Benthos, however, are fixed in place, continuously sample the overlying water conditions, and demonstrate a variety of consistent responses to multiple sources of stress. Benthic indices of biotic integrity (BIBIs) have been particularly useful for assessing aquatic systems. However most indices have focused on assessing effects related to changes in water quality rather than water quantity. This study develops a Freshwater Inflow Biotic Index (FIBI) to determine how changes in freshwater inflow affect benthic populations, which in turn reflect the ecological condition of an estuary. Based on benthic succession theory and long-term data, 12 biotic metrics were chosen that characterized benthic community structure in response to inflow regimes. The metrics were ranked and then reduced to one variable using principal...

The goal of the present study was to identify the potential changes in ecosystem service values provided by wetlands in Galveston Bay, Texas, USA, under the Intergovernmental Panel on Climate Change (IPCC) A1B max (0.69 m) sea level rise scenario. Built exclusively upon the output produced during the Sea Level Affecting Marshes Model 6 (SLAMM 6) exercise for the Galveston Bay region, this study showed that fresh marsh and salt marsh present a steady decline from 2009 (initial condition) to 2100. Fresh marsh was projected to undergo the biggest changes, with the loss of approximately 21% of its extent between 2009 and 2100 under the A1B max scenario. The percentages of change for salt marsh were less prominent at approximately 12%. This trend was also shown in the values of selected ecosystem services (disturbance regulation, waste regulation, recreation, and aesthetics) provided by these habitats. An ordinary least squares regression was used to calculate the monetary value of the selected ecosystem services provided by salt marsh and fresh marsh in 2009, and in 2050 and 2100 under the A1B max scenario. The value of the selected services showed potential monetary losses in excess of US$40 million annually in 2100, compared to 2009 for fresh marsh and more than $11 million for salt marsh. The estimates provided here are only small portions of what can be lost due to the decrease in habitat extent, and they highlight the need for protecting not only built infrastructure but also natural resources from sea level rise. Integr Environ Assess Manag 2017;13:431-443. © 2016 SETAC.

Suspension-feeding activities of oysters impart a potentially significant benefit to estuarine ecosystems via reduction of water column nutrients, plankton and seston biomass, and primary productivity which can have a significant impact on human well-being. This study considered nitrogen regulation by eastern oysters Crassostrea virginica in the Mission-Aransas Estuary, Texas, USA, as a function of denitrification, burial, and physical transport from the system via harvest. Oyster reefs were estimated to remove 502.5 kg N km(-2) through denitrification of biodeposits and 251.3 kg N km(-2) in burial of biodeposits to sediments. Nitrogen is also physically transported out of the estuary via harvest of oysters. Commercial harvest of oysters in the Mission-Aransas Estuary can remove approximately 21,665 kg N per year via physical transport from the system. We developed a transferable method to value the service of nitrogen regulation by oysters, where the potential cost equivalent value of nitrogen regulation is quantified via cost estimates for a constructed biological nutrient removal (BNR) supplement to a wastewater treatment plant. The potential annual engineered cost equivalent of the service of nitrogen regulation and removal provided by reefs in the Mission-Aransas Estuary is $293,993 yr(-1). Monetizing ecosystem services can help increase awareness at the stakeholder level of the importance of oysters beyond commercial fishery values alone.