National Estuarine Research Reserve Research Articles

Seasonal and Annual Dynamics in Seagrass Beds of the Grand Bay National Estuarine Research Reserve, Mississippi

Along the mainland coastline of eastern Mississippi Sound, the seagrass species Ruppia maritima (Wigeongrass) and Halodule wrightii (Shoalgrass) co-occur in persistent and sometimes extensive beds within Grand Bay. This paper presents seasonal and annual changes in those Ruppia-Halodule beds that are part of the Grand Bay National Estuarine Research Reserve in western Grand Bay using 2005–2011 transect survey data of percent cover and 2009–2013 biomass sampling data. The seagrass beds exhibited significant interannual variation in areal coverage and seasonal variations in biomass, with peak total aboveground biomass (up to 140 g dry wt/m2) in July and August. Intact R. maritima and H. wrightii seeds were found in the sediment, with densities as high as 4160 seeds/m2. The Ruppia-Halodule beds did not show any short-term declines in their growth or abundance following 2005 Hurricanes Katrina and Rita nor the 2010 Deepwater Horizon oil spill. Resumen: A lo largo de la costa continental del este del Mississippi Sound, las especies de pastos marinos Ruppia maritima (Wigeongrass) y Halodule wrightii (Shoalgrass) coexisten en camas persistentes ya veces extensas dentro de Grand Bay. Este articulo presenta cambios estacionales y anuales en los lechos de Ruppia-Halodule que forman parte de la Reserva de Investigacion Estuarina Nacional de Grand Bay en el oeste de Grand Bay usando datos de la encuesta de transectos de 2005–2011 de cobertura porcentual y datos de muestreo de biomasa 2009–2013. Los lechos de pastos marinos mostraron una variacion interanual significativa en la cobertura aerea y las variaciones estacionales en la biomasa, con el pico de biomasa total sobre el suelo (hasta 140 g de peso seco/m2) en julio y agosto. Se encontraron semillas intactas de R. maritima y H. wrightii en el sedimento, con densidades tan altas como 4160 semillas/m2. Las camas Ruppia-Halodule no mostraron disminuciones a corto plazo en su crecimiento o abundancia despues de los huracanes Katrina y Rita en el 2005 ni en el derrame de petroleo Deepwater Horizon del 2010.

BIODIVERSITY CONSERVATION PLANNING ADAPTIVE TO SEA LEVEL RISE: THE CASE OF THE GUANA TOLOMATO MATANZAS NATIONAL ESTUARINE RESEARCH RESERVE IN FLORIDA

Currently, sea level rise becomes one of the biggest threats to biodiversity conservation in low-lying coastal areas, and coastal conservation areas need to be optimized to the rising sea level. This paper introduces the case of the Guana Tolomato Matanzas National Estuarine Research Reserve in Florida, which shows that the key conservation areas adaptive to sea level rise can be identified by modeling with integrated protection planning. Combining the American case’s lessons, the paper further comes up with suggestions on biodiversity protection adaptive to sea level rise for China’s coastal cities and regions.

Introduction: Coastal Seagrass and Submerged Aquatic Vegetation Habitats in the Gulf of Mexico

IntroductionCoastal Seagrass and Submerged Aquatic Vegetation Habitats in the Gulf of Mexico Patrick Biber* and Hyun Jung Cho* This special issue compiles original research and reviews of previous research on an important geographic constitution at the water-land interface: the seagrass/Submerged Aquatic Vegetation (SAV) beds in the Gulf of Mexico (GoM) coastal zone. SAV are a group of vascular plants that grow underwater; and seagrass is a specialized subgroup of SAV that have adapted to live in the high salinity coastal and marine waters. Presence of, types of, and seasonality of SAV beds have substantial influences on geography, ecology, landscape, culture, and economy in the coastal zone. Healthy SAV beds help shape, maintain, and modify coastal landscapes by buffering wave energy, modifying water currents, protecting shorelines from erosion, aiding sediment deposition, consolidating substrate, and changing littoral profiles and water depth. Coastal seagrass resources are among the most productive ecosystems on Earth. Seagrass beds perform numerous vital ecological functions and provide food and shelter for commercially and ecologically important organisms, including blue crabs, shrimp, turtles, manatees, and waterfowl. Therefore, assessment of SAV distribution, composition, and abundance has been of particular interest to coastal environmental managers, scientists, developers, and recreationists as this information serves as an excellent indicator of estuarine environmental quality. Coastal areas containing seagrass and SAV beds carry geographical and historical importance in the Southeast, especially throughout the GoM. The GoM and its resources have immense ecological, economical, and historic values to the U.S. but have been going through several major environmental disturbances and disasters including, but not limited to, major hurricanes (e.g., 2005 Hurricane Katrina), the 2010 Deepwater Horizon Oil Spill, red tides, rapid subsidence, marsh erosion, threats from sea level rise, and river water diversions. Man-made levees [End Page 208] along major rivers (e.g., Mississippi River) prevent natural flooding from the rivers that historically used to deliver the necessary nutrients and sediments for coastal wetland growth and delta formation. This has resulted in coastal wetland retreat and subsidence. In addition, environmental quality has been significantly degraded, which in turn, results in the loss of ecological/economical services in the region. Loss of coastal land and environmental degradation are projected to be amplified with changing global climate, which is a growing threat to coastal SAV beds (Scavia et al. 2002, Doyle et al. 2010, Unsworth et al. 2014). The low-lying coastal areas of the GoM are particularly vulnerable to natural/anthropogenic disturbances due to the effects of sea-level rise, increases in population density, extensive landscape alternation, modification, and armoring of natural shorelines, as well as natural/man-made disasters. Documentation of habitat conditions, change over time, and interactions with the human environment are critical needs to better assess current status and predict future trends for SAV/seagrass habitats, a critical component of coastal geography. However, many regionally focused relevant studies on these habitats have not been addressed in the increasingly international scope of many pertinent scientific journals. We, the Guest Editors, agreed that compiling regional studies on a unifying topic would help enhance understanding of long-term and larger scale trends in SAV/seagrass beds of the GoM. In response, requests for manuscripts on sea-grass and other SAV occurring in tidally-influenced GoM coastal habitats were sent out to several regional seagrass/SAV scientists. In order to comply with the scope of Southeastern Geographer, the papers in this issue present studies on SAV/seagrass with a regional geography focus, particularly relating to issues of temporal variation and changes related to land use change, human alteration, and climate change. The five papers published in this special issue synergistically help to summarize change occurring across the GoM. Geographically, this special issue covers coastal habitats from Texas (the Coastal Bend and Laguna Madre), Louisiana (Terrebonne Bay, the Pontchartrain basin), areas around the borders of Mississippi and Alabama (Grand Bay National Estuarine Research Reserve), and west Florida (Tampa Bay). The topics of the papers extend from (1) evaluation of SAV for nekton habitat value in comparison to marshes during one season (Jerabek et al.), (2) test of a model to assess carbon stocks in seagrass meadows in a single year (Congdon & Dunton), (3) temporal...

Changes in Sediment Characteristics upon Oyster Reef Restoration, NE Florida, USA

As ecosystem engineers, oysters alter a host of physical and chemical characteristics of their environment. Oyster reef construction (or restoration) can therefore be expected to have wide ranging effects, from increased refuge for organisms, to lower turbidity. We measured changes in sediment characteristics and benthic nutrient fluxes near a constructed intertidal oyster reef in the Guana Tolomato Matanzas National Estuarine Research Reserve in NE Florida, USA. Within one year of reef construction, particle size distribution shifted towards finer sediment, and organic matter content increased to 7.3% ± 2.1 (standard error) compared to 2.9% ± 0.8 (standard error) at control sites, where oysters were absent. After three years, up to 15 cm of this fine, organic-rich sediment had accreted immediately shoreward of the reef. In benthic flux experiments performed under dark conditions, reef sediments released 167 μM/m2/hr NH4+ compared to –4 μM/m2/hr from control site sediments. Under light conditions both reef and control fluxes were insignificant. This was presumably due to uptake by benthic microalgae; chlorophyll a concentrations were 3 times higher in reef sediments compared to controls. Deposition of organic rich sediment near oyster reefs might render important ecosystem services from carbon burial and perhaps increased denitrification. However, burial of live oysters with excessive sediment accretion might threaten reef success in some cases. Our results highlight the complexity of physical-biological interactions and the need for complete assessment of ecosystem services in order to optimize design and thoroughly evaluate restoration outcomes.

Analysis of the Nearshore Fish Community in a Northeast Florida Estuary

Abstract The Guana Tolomato Matanzas National Estuarine Research Reserve (GTMNERR), located in Northeast Florida, serves as an ideal estuarine habitat for many economically and ecologically important species of fish and crabs. As climate change affects Florida ecosystems, the replacement of Spartina alterniflora (Smooth Cordgrass) marshes by northward-moving mangroves is possible. A change in the dominant vegetation has the potential to alter organic carbon inputs, which can lead to a shift in the primary and secondary consumers in the area. An assessment of the fish community is needed in the systems where the change from Smooth Cordgrass to mangrove is the most likely in order to determine which species and which breeding populations will be affected. We conducted a biodiversity survey over the course of 24 months to document the seasonal and spatial patterns in species richness, seasonal abundance, and size of species caught. From May 2013 to April 2015, we used a 15.24-m seine net to sample 8 sites wi...

Assessing tidal marsh resilience to sea-level rise at broad geographic scales with multi-metric indices

Tidal marshes and the ecosystem services they provide may be at risk from sea-level rise (SLR). Tidal marsh resilience to SLR can vary due to differences in local rates of SLR, geomorphology, sediment availability and other factors. Understanding differences in resilience is critical to inform coastal management and policy, but comparing resilience across marshes is hindered by a lack of simple, effective analysis tools. Quantitative, multi-metric indices are widely employed to inform management of benthic aquatic ecosystems, but not coastal wetlands. Here, we develop and apply tidal marsh resilience to sea-level rise (MARS) indices incorporating ten metrics that contribute to overall marsh resilience to SLR. We applied MARS indices to tidal marshes at 16 National Estuarine Research Reserves across the conterminous U.S. This assessment revealed moderate resilience overall, although nearly all marshes had some indication of risk. Pacific marshes were generally more resilient to SLR than Atlantic ones, with the least resilient marshes found in southern New England. We provide a calculation tool to facilitate application of the MARS indices to additional marshes. MARS index scores can inform the choice of the most appropriate coastal management strategy for a marsh: moderate scores call for actions to enhance resilience while low scores suggest investment may be better directed to adaptation strategies such as creating opportunities for marsh migration rather than attempting to save existing marshes. The MARS indices thus provide a powerful new approach to evaluate tidal marsh resilience and to inform development of adaptation strategies in the face of SLR.

Relationships Between Meteorological and Water Quality Variables and Fisheries-Independent White Shrimp (Litopenaeus setiferus) Catch in the ACE Basin NERR, South Carolina

White shrimp (Litopenaeus setiferus) fisheries-independent and fisheries-dependent landings can be highly variable and may be related to environmental factors that influence growth, mortality, and survival. We used linear regression analysis to look for potential relationships between environmental and white shrimp catch-per-unit-effort (CPUE) data collected from the Ashepoo-Combahee-Edisto (ACE) Basin National Estuarine Research Reserve (NERR) for four critical months in the shrimp life cycle. This analysis used data from white shrimp fisheries-independent CPUE (2002 to 2014) and water quality and meteorological variables for August (juvenile), December (sub-adult), March (adult), and April (spawning adult). The results showed that shrimp CPUE was mainly correlated with water temperature, salinity, and dissolved oxygen concentration collected through the ACE Basin NERR’s System-Wide Monitoring Program (SWMP), but offshore wind, precipitation, and intra-annual CPUEs also partially explained the variability in monthly CPUEs. Black gill prevalence was correlated with water temperature and salinity. Additionally, our analysis found that winter water temperatures of ≤11 °C were correlated with reduced shrimp abundance the following spring. Ultimately, managers would like to successfully predict white shrimp stock abundance throughout fishing seasons based on environmental conditions. This study is a first step in identifying the environmental variables that may be useful in predicting white shrimp CPUE in the South Atlantic Bight. The techniques employed here can serve as a basis for predicting and managing other wild annual fisheries stocks.

Effects of Hypoxia on Fish Survival and Oyster Growth in a Highly Eutrophic Estuary

Human land use activities around estuaries can result in high levels of eutrophication. At Elkhorn Slough estuary, a highly eutrophic California estuary, we investigated the effects of impaired water quality on two stress-tolerant estuarine species, a common fish, the staghorn sculpin, Leptocottus armatus and a foundational invertebrate, the Olympia oyster, Ostrea lurida. We caged the two indicator species at six wetlands with different levels of water quality impairment, four of which had restricted tidal flow. We also recorded water quality parameters simultaneously at all sites using YSI sondes, and sampled nutrients and chlorophyll-a monthly, building on the National Estuarine Research Reserve System-wide Monitoring Program. We found that the monitored environmental variables predicted ecological responses by the indicator species. In particular, we found that the duration and severity of hypoxia were negatively correlated with fish survival and oyster growth. Further, our results corroborate previous studies that artificial tidal restriction leads to increased hypoxia stress. We conclude that large diurnal fluctuations in dissolved oxygen and extended nighttime hypoxia can have lethal and sub-lethal effects even on stress-tolerant organisms in the estuary. While laboratory experiments have often shown such effects, it is relatively rare to demonstrate negative effects of oxygen variation with in situ experiments, which provide stakeholders with concrete evidence for impaired water quality at local wetlands. Tidally restricted sites, which experience the largest fluctuations in dissolved oxygen and longest periods of hypoxia, harbor conditions harmful to vertebrates and invertebrates in the estuary. Reversing the anthropogenically induced low oxygen levels, by restoring more natural tidal exchange and by decreasing agricultural runoff, could improve the survival and growth of important estuarine organisms.

Modeling Salt Panne Land-Cover Suitability under Sea-Level Rise

ABSTRACT Linhoss, A.C. and Underwood, W.V., 2016. Modeling salt panne land-cover suitability under sea-level rise. Salt pannes are an ecologically important but poorly understood feature of the salt marsh environments. Like all coastal marshes, salt pannes are threatened by sea-level rise; therefore, it is important to assess how they will be affected by rising seas. Because of a lack of understanding regarding salt panne formation and the possibly stochastic nature of their development, a traditional and purely deterministic modeling approach is unsuitable for assessing the impacts of sea-level rise on salt pannes. This research used a combination of deterministic and stochastic models to simulate the land-cover suitability for salt pannes in the Grand Bay National Estuarine Research Reserve, Mississippi, under five sea-level rise scenarios, including a rise of 0.25, 0.5, 1.0, 1.5, and 2.0 m by 2100. The Sea-Level Affecting Marshes Model (SLAMM) simulated general land-cover at the study site. However, SL...

Hurricane impacts on turbidity and sediment in the Rookery Bay National Estuarine Research Reserve, Florida, USA

The resuspension and transportation of sediments affect the nutrient or contaminants cycles in water column. Therefore, hurricane-induced sediment resuspension in coastal waters may cause environment impacts on coastal ecosystems. In this study, field observed data during a hurricane event from the Rookery Bay National Estuarine Research Reserve (Rookery Bay NERR), Florida, were studied. Based on the relationship between sediment and turbidity, variations of turbidity in the Rookery Bay NERR were discussed in this paper under the impact of the Hurricane Isaac in 2012. Time series analysis indicates that Hurricane Isaac causes the substantial increase of turbidity. Traditional direct regression analysis with raw data was found to result in poor correlation (R2<0.41) between wind speed and turbidity due to the impacts of multi-factors in coastal waters of study region during hurricane. Then Hanning Filter was used to remove tidal effect, which shows some improvement of correlations (R2>0.6) between wind speed and turbidity. Further improvement was made by introducing a phase factor to account for the lag time between the peak turbidity and peak wind speed, which lead to further improvement of the regression equation between wind speed and turbidity. By using Hanning Filter and phase factor, the regression equation between turbidity and wind speed fits well with observations (R2>0.96). Different lag time between wind speed and turbidity at different locations illustrated that wind had different effects on turbidity due to the locations and water depth. Based on the approximate empirical relationship between turbidity and sediment concentration, a regression equation between wind speed and sediment concentration was derived approximately. The equation could be applied to approximately estimate the sediment concentration using wind speed during hurricane, especially with the strong wind speed above 4m/s. It can be used to provide technical supports for sediment assessment and coastal zone research under extreme clime in the study region.

Atrazine Transport Within a Coastal Zone in Southeastern Puerto Rico: a Sensitivity Analysis of an Agricultural Field Model and Riparian Zone Management Model

Agrichemical runoff from farmland may adversely impact coastal water quality. Two models, the Agricultural Policy/Environmental eXtender (APEX) and the Riparian Ecosystem Management Model (REMM), were used to evaluate the movement of the herbicide atrazine to the Jobos Bay National Estuarine Research Reserve from adjacent fields. The reserve is located on Puerto Rico’s southeast coast. Edge-of-field atrazine outputs simulated with the APEX were routed through a grass-forest buffer using the REMM. Atrazine DT50 (half-life) values measured in both field and buffer soils indicated that accelerated degradation conditions had developed in the field soil due to repeated atrazine application. APEX simulations examined both the measured field and buffer soil atrazine DT50 and the model’s default value. The use of the measured field soil atrazine degradation rate in the APEX resulted in 33 % lower atrazine transport from the field. REMM simulations indicated that the buffer system had the potential to reduce dissolved atrazine transport in surface runoff by 77 % during non-tropical storm events by increasing infiltration, slowing transport, and increasing time for pesticide degradation. During a large runoff event due to a tropical storm that occurred close to the time of an atrazine application, the REMM simulated only a 37 % reduction in atrazine transport. The results indicate that large storm events soon after herbicide application likely dominate herbicide transport to coastal waters in the region. These results agree with water quality measurements in the reserve. This study demonstrated the sensitivity of these models to variations in DT50 values in evaluating atrazine fate and transport in the region and emphasizes that the use of measured DT50 values can improve model accuracy.

North Pacific Spiny Dogfish (Squalus suckleyi) Presence in Eelgrass Habitat in the Salish Sea, Washington

Eelgrass (Zostera marina) is the dominant seagrass along the Pacific North American Coast, providing complex physical structure, high trophic productivity, and protection from predators (Phillips 1984; Simenstad 1994). Because of these multiple functions, many fish species and life stages use Eelgrass beds more than other nearshore habitat types (Dean and others 2000; Murphy and others 2000; Johnson and Thedinga 2005). Currently, there is growing evidence identifying nearshore habitats as places that may be regularly inhabitated by large-bodied fish, including sharks (Tobin and others 2014), but it is not clear how much sharks use Eelgrass habitat. In other parts of North America, several sharks have been reported inhabiting Eelgrass habitat, including Sandbar Sharks (Carcharhinus milberti) in Chesapeake Bay, Maryland and Virginia (Orth and Heck 1980), Leopard Sharks (Triakis semifasciata) in Humboldt Bay, California (Ebert and Ebert 2005), and Gray Smooth-hound Sharks (Mustelus californicus) in Bolsa Chica, Orange County, California (Espinoza and others 2011). Conversely, reports of sharks are rare in Eelgrass beds in the Salish Sea region, which is located between the southwestern tip of British Columbia and the northwestern tip of Washington (Fig. 1; Farrer 2009). In this region, North Pacific Spiny Dogfish (Squalus suckleyi Girard 1854; Ebert and others 2010), hereafter Spiny Dogfish, are currently considered an abundant upper trophic level predator (Harvey and others 2010). Although Spiny Dogfish have been documented as making local movements along the nearshore in Puget Sound, Washington (Andrews and Harvey 2013), they have not generally been reported in Eelgrass habitat. Spiny Dogfish, however, have been captured in sand and Eelgrass habitat in Samish Bay, Washington, using overnight commercial gill net sets (Farrer 2009). Here we document the use of Eelgrass habitat by Spiny Dogfish. We conducted our study in Padilla Bay National Estuarine Research Reserve, Mount Vernon, Washington. Padilla Bay sustains one of the most extensive Eelgrass beds in the inner Salish Sea region (Berry and others 2003; Fig. 1). The shallow estuary covers nearly 4500 ha, of which .3200 ha is Eelgrass of both the native Z. marina and the non-native Z. japonica (Shull 1999). Padilla Bay differs from most estuaries in the region because it has become isolated from major rivers as it has filled with sediment from the Skagit River to the south, and the Eelgrass has thrived in the absence of a major freshwater input. However, drainage from adjacent agricultural lands enters via sloughs with tidegates. Other nearby sources of freshwater are the Samish River to the north and the Skagit River via the Swinomish Channel to the south. Tides in the region are mixed semidiurnal. We sampled 3 sites along major tidal channels in contiguous Z. marina habitats that were located over mud bottoms. These sites were located in the north (Short Channel), middle (Middle Channel), and south (Bayview Channel) portions of Padilla Bay (Fig. 1). At each site, we sampled 2 adjacent locations to have replicate samples, thereby completing 6 overnight gill-net sets for each month of May, June, and July of 2004. We trawled during the day to characterize the fish assemblage in the shallows (Penaluna 2006), and we set gill nets overnight in Eelgrass locations parallel to the adjacent tidal channel to document nocturnal movements of larger fishes. Each 15-m by 2-m experimental gill net was composed of five 3-m panels, with square mesh size increments of 12, 25, 38, 50, and 68 mm, with leadand foam-core lines. We sampled when tidal elevations ranged from –1.5to –3.0-m mean lower low water. Catch per unit of effort (CPUE) was measured as number of fish per net-hour. The highest CPUEs of Spiny Dogfish captured during overnight gill-net sets were recorded in June and July (Table 1; Fig. 2). Spiny GENERAL NOTES

Improving estimates of ecosystem metabolism by reducing effects of tidal advection on dissolved oxygen time series

AbstractIn aquatic systems, time series of dissolved oxygen (DO) have been used to compute estimates of ecosystem metabolism. Central to this open‐water method is the assumption that the DO time series is a Lagrangian specification of the flow field. However, most DO time series are collected at fixed locations, such that changes in DO are assumed to reflect metabolism and that effects of advection or mixing are negligible. A weighted regression model was applied to remove variability in DO time series from tides, thereby helping to partially relax this assumption and improve metabolism estimates. The method offers a distinct advantage over traditional deconvulution methods by targeting the periodicity of the tidal component while preserving the true biological signal. The model was first applied to simulated DO time series with specified biological and physical characteristics, and then applied to 1 yr of continuous monitoring data from four stations within the National Estuarine Research Reserve System. The correlation of DO and metabolism estimates with tides was greatly reduced after using weighted regression. The model was especially effective when the magnitude of tidal influence was high and correlations between tidal change and the solar cycle were low at the time scales of interest. The model was less robust when tides and the solar cycle were correlated for protracted periods. By reducing the effects of physical transport on metabolism estimates, there may be increased potential to empirically relate metabolic rates to causal factors on timescales of several days to several weeks.

Program Profile: The Georgia Coastal Ecosystems Long Term Ecological Research Project (GCE‐LTER)

Program Profile: The <scp>G</scp>eorgia Coastal Ecosystems Long Term Ecological Research Project (GCE‐LTER)

A spatial assessment of baseline nutrient and water quality values in the Ashepoo–Combahee–Edisto (ACE) Basin, South Carolina, USA

The Ashepoo–Combahee–Edisto (ACE) Basin (South Carolina, USA) National Estuarine Research Reserve System (NERRS) encompasses some of the least developed USA coastline. Yet, periodic sampling showed that certain regions have higher nutrient, fecal coliform, and chlorophyll a levels, often with lower dissolved oxygen, than other South Carolina estuaries. To evaluate the spatial extent of these issues, a summer (2008) baseline study was conducted. Physical water quality, total nitrogen and phosphorus, chlorophyll a, dissolved organic carbon, and suspended solids were measured from surface waters of 67 stations (30 tidal creek, 37 open water). Nutrient and chlorophyll a levels were significantly (p<0.01) and negatively correlated with the extent of open water (% land cover), and chlorophyll a and nitrogen levels were, at times, elevated relative to concentrations typical of other estuaries in the state, reinforcing previous findings. This survey also identified several creeks not previously monitored that exhibited elevated nutrients.

Carbon export from fringing saltmarsh shoreline erosion overwhelms carbon storage across a critical width threshold

Saltmarshes are carbon storage hotspots and help to offset anthropogenic carbon emissions; however, marshes are threatened by sea-level rise, erosion, and human development. Recent efforts to constrain the saltmarsh carbon cycle have focused on the processes of carbon burial and sequestration with respect to sea-level rise and global warming. Simultaneously, many marshes that fringe the margins of estuaries and barrier islands are eroding, which releases old carbon from the saltmarsh and transports it into the estuary, and that process should be included in marsh carbon budgets. Additionally, if marshes cannot transgress the upland at a rate that balances shoreline retreat, then the marsh will narrow, thus reducing the area available for carbon storage. Here, we present the development of a box model that incorporates both carbon storage and carbon export via shoreline erosion to estimate the annual carbon budget of saltmarsh sediments. We test the model using field data collected at a fringing marsh within the Rachel Carson National Estuarine Research Reserve in North Carolina. The shoreline erosion rates along the fringing marsh are variable and the model output shows that the stretch of marsh that is retreating 0.76 m yr−1 switched to a carbon source in 1930, while another portion of the marsh that is retreating more slowly (0.65 m yr−1) will switch to a source in 2021. The model indicates that the carbon budget of a saltmarsh is highly sensitive to the rate of shoreline retreat and that rapidly-eroding marshes may already be net sources of carbon. These results underscore the importance of conserving existing marshes, mitigating shoreline erosion, and considering shoreline erosion in the design of saltmarsh restoration projects.

Trace elements and heavy metals in the Grand Bay National Estuarine Reserve in the northern Gulf of Mexico

The objectives of this study are to investigate distribution of trace elements and heavy metals in the salt marsh and wetland soil and biogeochemical processes in the Grand Bay National Estuarine Research Reserve of the northern Gulf of Mexico. The results show that Hg, Cd and to some extent, As and Pb have been significantly accumulated in soils. The strongest correlations were found between concentrations of Ni and total organic matter contents. The correlations decreased in the order: Ni>Cr>Sr>Co>Zn, Cd>Cu>Cs. Strong correlations were also observed between total P and concentrations of Ni, Co, Cr, Sr, Zn, Cu, and Cd. This may be related to the P spilling accident in 2005 in the Bangs Lake site. Lead isotopic ratios in soils matched well those of North American coals, indicating the contribution of Pb through atmospheric fallout from coal power plants.

Permeable Reactive Barriers Designed To Mitigate Eutrophication Alter Bacterial Community Composition and Aquifer Redox Conditions.

Permeable reactive barriers (PRBs) consist of a labile carbon source that is positioned to intercept nitrate-laden groundwater to prevent eutrophication. Decomposition of carbon in the PRB drives groundwater anoxic, fostering microbial denitrification. Such PRBs are an ideal habitat to examine microbial community structure under high-nitrate, carbon-replete conditions in coastal aquifers. We examined a PRB installed at the Waquoit Bay National Estuarine Research Reserve in Falmouth, MA. Groundwater within and below the PRB was depleted in oxygen compared to groundwater at sites upgradient and at adjacent reference sites. Nitrate concentrations declined from a high of 25 μM upgradient and adjacent to the barrier to <0.1 μM within the PRB. We analyzed the total and active bacterial communities filtered from groundwater flowing through the PRB using amplicons of 16S rRNA and of the 16S rRNA genes. Analysis of the 16S rRNA genes collected from the PRB showed that the total bacterial community had high relative abundances of bacteria thought to have alternative metabolisms, such as fermentation, including candidate phyla OD1, OP3, TM7, and GN02. In contrast, the active bacteria had lower abundances of many of these bacteria, suggesting that the bacterial taxa that differentiate the PRB groundwater community were not actively growing. Among the environmental variables analyzed, dissolved oxygen concentration explained the largest proportion of total community structure. There was, however, no significant correlation between measured environmental parameters and the active microbial community, suggesting that controls on the active portion may differ from the community as a whole.

Evaluating nonindigenous species management in a Bayesian networks derived relative risk framework for Padilla Bay, WA, USA.

Many coastal regions are encountering issues with the spread of nonindigenous species (NIS). In this study, we conducted a regional risk assessment using a Bayesian network relative risk model (BN-RRM) to analyze multiple vectors of NIS introductions to Padilla Bay, Washington, a National Estuarine Research Reserve. We had 3 objectives in this study. The 1st objective was to determine whether the BN-RRM could be used to calculate risk from NIS introductions for Padilla Bay. Our 2nd objective was to determine which regions and endpoints were at greatest risk from NIS introductions. Our 3rd objective was to incorporate a management option into the model and predict endpoint risk if it were to be implemented. Eradication can occur at different stages of NIS invasions, such as the elimination of these species before being introduced to the habitat or removal of the species after settlement. We incorporated the ballast water treatment management scenario into the model, observed the risk to the endpoints, and compared this risk with the initial risk estimates. The model results indicated that the southern portion of the bay was at greatest risk because of NIS. Changes in community composition, Dungeness crab, and eelgrass were the endpoints most at risk from NIS introductions. The currents node, which controls the exposure of NIS to the bay from the surrounding marine environment, was the parameter that had the greatest influence on risk. The ballast water management scenario displayed an approximate 1% reduction in risk in this Padilla Bay case study. The models we developed provide an adaptable template for decision makers interested in managing NIS in other coastal regions and large bodies of water.

Does bird removal affect grasshopper grazing on Juncus roemerianus (black needlerush) marshes?

Grazing on J. roemerianus (black needlerush), grasshopper abundance, and black needlerush plants was examined in the presence and exclusion of marsh birds. Birds were excluded using a PVC framed exclosure wrapped with bird netting that allowed free passage of marsh grasshoppers. These measurements were taken bi-monthly from April to August 2011 in a black needlerush marsh within the Grand Bay National Estuarine Research Reserve (Moss Point, MS, USA). Grazing metrics, grasshopper abundance, and plant health metrics showed no effect of bird exclusions across all sampling dates. In contrast to other marsh systems with strong trophic cascades (e.g., Spartina alterniflora on US east coast), these results suggest that the primary consumer (grasshoppers) is not affected by the presence of their dominant predator (birds) which leads to no change in the health of the primary producer (black needlerush). Information derived from this study furthers our understanding of the trophic relationships within black needlerush marshes in the northern Gulf of Mexico.