Coastal Restoration Efforts Research Articles

Predicting Characteristic Length Scales of Barrier Island Segmentation in Microtidal Environments

AbstractSegmented barrier islands can be found in regions with small tidal ranges. In contrast to tidally dominated barriers, where inlet dynamics are thought to control island length scales, the controls on barrier island length scales in wave‐dominated environments have not been quantified. These microtidal barriers typically have a curved shoreline, suggesting the influence of wave‐driven alongshore sediment transport. Microtidal barriers are also typically hydrodynamically isolated from one another, as weak tidal flows limit interactions between adjoining barriers. To better understand the controls on and scales of barrier segmentation in the relative absence of tides, here we develop a theoretical framework to estimate the alongshore length scales at which a barrier will either breach or heal following a disturbance in the barrier morphology. The non‐dimensional framework compares the timescales of overwash (advective) and alongshore sediment transport (diffusive) processes along barrier island chains. We then apply this framework to modern barrier islands in the microtidal Gulf of Mexico using wave hindcast data and the lengths, widths, heights, and lagoon depths measured from remotely sensed geospatial data and topobathymetric data. We find that most of these barriers are currently longer than their critical length scale, often as a result of coastal restoration efforts. Our critical length scale analysis suggests that most of the Gulf of Mexico barriers are vulnerable to segmentation despite coastal restoration efforts intended to protect fisheries and the mainland coasts.

A PATH TOWARDS HOLISTIC COASTAL ZONE MANAGEMENT IN TEXAS LEVERAGING SIGNIFICANT INVESTMENTS IN DATA COLLECTION, PLANNING, AND IMPLEMENTATION

The Gulf of Mexico shorelines of Texas are in a largely regressive state due to an amalgamation of factors including but not limited to: sea level rise, subsidence, littoral drift, and riverine supply disruptions. In some areas the erosion rate is several meters annually, leading to significant loss of coastal barrier island area. The bulk of the coastal barrier systems in Texas is undeveloped. However, barrier island loss is no longer able to go unnoticed as there is ever-growing recognition of their intrinsic value to coastal habitat and economies and their role in coastal storm resilience. Projects with significant merit and sediment needs are being identified for funding, which could result in a firstcome- first-serve extraction of the easily available and less costly sediment resources. Without proper management, the complexity and cost of future projects will naturally escalate, leading to a reduction in investments due to lower returns. The following questions need to be addressed: how can lower returns be avoided to incentivize investment and maximize coastal restoration efforts in Texas? And what can be done to galvanize support for beneficial use (BU) placement of beach-quality dredge material to minimize its removal from the littoral system? What can be done now to inform and leverage the existing and future knowledge so that management decisions lead to better outcomes for the environment and Texas constituents? A well thought out and executed plan maximizing returns and coastal resilience will enable other regions to more easily replicate the success.

Fluvial Delivery and Wave Resuspension of Sediment in a Sheltered, Urbanized Pacific Northwest Estuary

The sequence and timing of sediment delivery and redistribution in coastal systems is important for shoreline stability, ecosystem services, and remediation planning. In temperate estuaries, understanding the role of fluvial sediment delivery and dispersal relative to wind and wave remobilization processes is particularly important to address the fate of contaminants, many of which adsorb to fine particles, and to assess changes in coastal systems under projected changes in climate. Here we present an integrated analysis of observations at multiple timescales to evaluate sediment dynamics and the sedimentary coupling between fluvial and oceanographic processes within Bellingham Bay, Washington, USA, an urban estuary. Time-series data of currents, waves, and turbidity at four moorings along with geochemical data from grab samples and cores of seabed sediment from across the bay are contrasted with the dynamics of the Nooksack River, its fluvial sediment source. Even during large (5-yr return interval) river-flood events, water-column suspended-sediment concentration (SSC) near the bed on the outer delta topset was not correlated with Nooksack River runoff and was instead closely correlated with local wind-wave height. In contrast, near-surface SSC was strongly correlated with fluvial discharge, suggesting intense water-column suspended-sediment stratification during flood events. Grain-size and geochemical (7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{7}$$\\end{document}Be and excess 210\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{210}$$\\end{document}Pb) results from seabed-sediment samples and historical bathymetric measurements of the subaqueous Nooksack River delta reveal spatial gradients of fluvial and wave influence and sediment-accumulation rates. Analysis of historical bathymetric surveys of the Nooksack River delta combined with the geochemical data reveal that about 75% of the fluvial sediment load can be accounted for in the Bellingham Bay receiving system. Studies of this type in urbanized coastal settings can help address ecological and geological questions regarding the risks from contaminants associated with fine-grained sediment, predict longer-term delta morphological evolution, and inform managers planning future coastal restoration efforts

Aragonite saturation states in estuaries along a climate gradient in the northwestern Gulf of Mexico

In the northwestern Gulf of Mexico (nwGOM), the coastal climate shifts abruptly from the humid northeast to the semiarid southwest within a narrow latitudinal range. The climate effect plays an important role in controlling freshwater discharge into the shallow estuaries in this region. In addition to diminishing freshwater runoff down the coast, evaporation also increases substantially. Hence, these estuaries show increasing salinity along the coastline due to the large difference in freshwater inflow balance (river runoff and precipitation minus evaporation and diversion). However, this spatial gradient can be disrupted by intense storm events as a copious amount of precipitation leads to river flooding, which can cause temporary freshening of these systems in extreme cases, in addition to freshwater-induced ephemeral stratification. We examined estuarine water aragonite saturation state (Ωarag) data collected between 2014 and 2018, covering a period of contrasting hydrological conditions, from the initial drought to multiple flooding events, including a brief period that was influenced by a category 4 hurricane. Based on freshwater availability, these estuaries exhibited a diminishing Ωarag fluctuation from the most freshwater enriched Guadalupe Estuary to the most freshwater-starved Nueces Estuary. While Ωarag values were usually much higher than the threshold level (Ωarag = 1), brief freshwater discharge events and subsequent low oxygen levels in the lower water column led to episodic corrosive conditions. Based on previously obtained Ωarag temporal trends and Ωarag values obtained in this study, we estimated the time of emergence (ToE) for Ωarag. Not only did estuaries show decreasing ToE with diminishing freshwater availability but the sub-embayments of individual estuaries that had a less freshwater influence also had shorter ToE. This spatial pattern suggests that planning coastal restoration efforts, especially for shellfish organisms, should emphasize areas with longer ToE.

Use of a wastewater recovery product (struvite) to enhance subtropical seagrass restoration.

Seagrasses are in decline worldwide, and their restoration is relatively expensive and unsuccessful compared to other coastal systems. Fertilization can improve seagrass growth in restoration but can also release nutrients and pollute the surrounding ecosystem. A slow-release fertilizer may reduce excessive nutrient discharge while still providing resources to the seagrass's rhizosphere. In this study, struvite (magnesium ammonium phosphate), a relatively insoluble, sustainable compound harvested in wastewater treatment plants, was compared to Osmocote™(14:14:14 Nitrogen: Phosphorus: Potassium, N:P:K), a popular polymer coated controlled release fertilizer commonly used in seagrass restoration. Two experiments compared the effectiveness of both fertilizers in a subtropical flow-through mesocosm setup. In the first experiment, single 0.5 mg of P per g dry weight (DW) doses of Osmocote™and struvite fertilizers were added to seagrass plots. Seagrass shoot counts were significantly higher in plots fertilized with struvite than both the Osmocote™and unfertilized controls (p< 0.0001). A significant difference in total P concentration was observed in porewater samples of Osmocote™vs struvite and controls (p< 0.0001), with struvite fertilized plots emitting more than controls (p ≤ 0.0001), but less than 2% of the total dissolved P (TDP) of Osmocote™fertilized plots (100+ mg/L versus x > 5 mg/L). A subsequent experiment, using smaller doses (0.01 and 0.025 mg of P per gram DW added), also found that the struvite treatments performed better than Osmocote™, with 16-114% more aboveground biomass (10-60% higher total biomass) while releasing less N and P. These results indicate the relatively rapid dissolution of Osmocote™may pose problems to restoration efforts, especially in concentrated doses and possibly leading to seagrass stress. In contrast, struvite may function as a slow-release fertilizer applicable in seagrass and other coastal restoration efforts.

Open SESAME: A Social-Ecological Systems framework for collaborative Adaptive Management and Engagement in coastal restoration and climate adaptation.

The successful implementation and sustainability of many marsh restoration efforts, including coastal adaptation to buffer inundation and mitigate sea level rise, often hinges upon support from surrounding human communities. Yet, stakeholder engagement in these projects remains relatively undervalued and underutilized. We present the Social-Ecological Systems, Adaptive Management, and Engagement (SESAME) framework that provides reciprocal connections between the human and ecological components of restoration efforts and the resulting management and engagement needs. We built and describe this framework through discussion of two case studies of coastal restoration efforts in southern New England salt marshes. The first case study focuses on the use of sediment placement to increase the elevation of the surface of a drowning marsh in Rhode Island as an interim measure to protect against sea level rise. The second case study describes the use of living shorelines for erosion mitigation on a salt marsh in Massachusetts. These cases included significant partner and stakeholder engagement and provided important lessons learned for practical implementation of the SESAME framework. Valuable lessons included the need for engagement throughout the entirety of the process, specific clarification of roles within the restoration efforts, and flexibility in implementation and goal setting.

The Vegetation of the United Arab Emirates Gulf Coast: Description and Analysis

Leandro, P.; Knuteson, S.L., and Bartholomew, A., 2022. The vegetation of the United Arab Emirates Gulf coast: Description and analysis. Journal of Coastal Research, 38(5), 951–967. Coconut Creek (Florida), ISSN 0749-0208. This geobotanical study describes the United Arab Emirates (UAE) mangrove and coastal halophyte plant communities in the intertidal areas and coastal salt flats along part of the UAE Arabian Gulf coast. Nine coastal vegetation association/community groups have been identified with TWINSPAN: Association 1, Avicennietum marinae Chapman, J. 1970.; Association 2, Salicornietum fruticosi Br. Bl. 1928; Association 3, Arthrocnemo macrostachi–Halocnemetum strobiliaci assoc. nova; Association 4, Suaedetum verae (fruticosae) Br. Bl. ex O. Bolós and Molinier 1958; Association 5, Tetraenetum qatarensis assoc. nova; Community 6, Calotropis procera; Community 7, Heliotropium bacciferum and Cornulaca monacantha; Community 8, Prosopis cineraria, and two new communities associated with anthropogenic disturbance; Community 9a, Avicennia marina with Sesuvium portulacastrum; and Community 9b, Avicennia marina with Salicornia fruticosa. Vegetation profiles of each community are presented. Canonical correspondence analysis revealed that the A. marina communities are associated with: higher salinity of the soil, higher soil CaCO3 content, and higher soil ion concentrations (K+, Mg++, Na+, Cl–). Coastal development has modified the UAE Gulf coast extensively in recent years, and this study describes the coastal plant association/communities, which will be useful for botanists, ecologists, and managers involved in coastal restoration efforts.

Floating along marsh edges: The impact of invasive water hyacinth (Eichornia crassipes) on estuarine species assemblages and predation risk

Estuaries are dynamic environments where the safety of habitat refuges can be altered by a variety of natural and anthropogenic disturbances. After tropical storms or other high water run off events, water hyacinth (Eichhornia crassipes), an invasive floating freshwater plant, can enter estuarine habitats where it can colonize marsh edges and may impact the abundance and distribution of estuarine species. In freshwater environments, hyacinth reduces water quality, increases habitat complexity, and alters freshwater aquatic invertebrate abundance and diversity. Yet, little is known about how this plant impacts estuarine species as it floats from freshwater tributaries to oceanic environments. To examine how water hyacinth impacts estuarine marsh fauna, we examined the effects of water hyacinth on nekton communities and fish predation risk using trapping and tethering techniques along a marsh edge that had been recently colonized by water hyacinth. We placed funnel traps under water hyacinth and in open water habitats to examine how water hyacinth impacted macrofaunal abundance and diversity. We also examined how water hyacinth impacted predation risk by tethering killifish at increasing distances from the marsh edge in open water and water hyacinth habitats. We found that shrimp, blue crabs, and killifish were generally more abundant under water hyacinth, but there was no difference in species richness or diversity between the two habitats. In tethering studies, killifish survival was generally similar between water hyacinth and open water likely due to the increased abundance of blue crabs underneath water hyacinth. This result suggests water hyacinth does not alter predation risk overall, but may alter the distribution of blue crabs and piscivorous fish predators. We did observe short term increases in killifish survival underneath small migrating hyacinth patches indicating patch size may further affect blue crab colonization and predation. Our results indicate that water hyacinth alters the safety of marsh edge habitats by increasing blue crab abundance, ultimately increasing their encounter rates with fish prey. Climate driven increases in tropical storms and coastal restoration efforts that alter salinity gradients will likely increase the abundance of water hyacinth in estuarine marshes offering important post-disturbance habitat structure to fish and invertebrates and increasing predation rates of blue crabs along marsh edges.

Sediment Distribution, Retention and Morphodynamic Analysis of a River-Dominated Deltaic System

River deltas have received considerable attention due to coastal land loss issues caused by subsidence, storms, and sea level rise. Improved understanding of deltaic processes and dynamics is vital to coastal restoration efforts. This paper describes the application of process-based morphodynamic models to a prograding river delta. The analysis focuses on the flow and sediment dynamics amongst the interconnected channel network of the delta. The models were validated against observations of velocity and sediment concentrations for the Wax Lake Delta (WLD) of the Atchafalaya River system in Louisiana, USA. The WLD provides an opportunity as a natural laboratory for studying the processes associated with river dominated deltaic growth. It includes a network of bifurcated channels that self-organize and dynamically adjust, as the delta grows seaward to the Gulf of Mexico. The model results for a flood event show that 47% of the flow exits the system as channelized flow and the remaining 53% exits as overbank flow. The fine sediment (silt and clay) distribution was proportional with water fluxes throughout the channel network, whereas sand distribution was influenced by geometric attributes (size, invert elevation, and alignment) of the distributary channels. The long-term deltaic growth predicted by the model compares well with the observations for the period 1998–2012. This paper provides insights on how the distribution of flow and sediment amongst the interconnected delta channels influences the morphodynamics of the delta to reach a dynamic equilibrium within this relatively young deltaic system.

Inoculating rhizome-propagated Sporobolus pumilus with a native mycorrhizal fungus increases salt marsh plant growth and survival

Salt marshes are ecosystems of significant ecological importance for coastal stability and fundamental roles in marine ecosystems. Salt marshes are declining due to anthropogenic and natural causes including sea level rise. Coastal restoration efforts have increased worldwide, but many fail in long-term coastal stability. We used a naturally occurring arbuscular mycorrhizal fungus (AMF) to test whether survival and early growth of the salt marsh grass Sporobolus pumilus (formerly Spartina patens) improved under simulated salt marsh conditions. Using a tidal mesocosm bench, we grew inoculated plants with varying AMF treatments under simulated tidal regimes to determine if AMF could aid in establishment of healthy Sporobolus communities. Rhizome-derived S. pumilus had greater survival and grew faster than seed-derived plants. Plants inoculated with propagated AMF consistently outperformed both sterile and native sediment controls in terms of plant survival and growth. Use of rhizome-derived Sporobolus inoculated with propagated Funneliformis geosporum showed the most promise in producing successful plant populations for salt marsh restoration. This may be due to plant life stage and improved plant nutrient status, allowing rhizome-derived plants to grow more quickly than seed-derived plants. Using these plants in future large-scale restoration may increase re-establishment of salt marsh ecosystems.

Frequency of extreme freeze events controls the distribution and structure of black mangroves (Avicennia germinans) near their northern range limit in coastal Louisiana

AbstractAimClimate change is expected to result in the tropicalization of coastal wetlands in the northern Gulf of Mexico, as warming winters allow tropical mangrove forests to expand their distribution poleward at the expense of temperate salt marshes. Data limitations near mangrove range limits have hindered understanding of the effects of winter temperature extremes on mangrove distribution and structure. Here, we investigated the influence of extreme freeze events on the abundance, height and coverage of black mangroves (Avicennia germinans) near their northern range limit in Louisiana.LocationCoastal Louisiana, USA.MethodsWe quantified the relationships between the frequency of extreme freeze events and A. germinans abundance, height and coverage using: (a) mangrove observation points recorded via aerial surveys from a fixed‐wing aircraft; (b) 30 years of temperature data; and (c) mangrove mortality and leaf damage temperature thresholds. We used freeze frequency data and mangrove–climate relationships to evaluate and spatially depict the risk of A. germinans freeze damage across Louisiana.ResultsWe identified strong negative relationships between the frequency of extreme freeze events and A. germinans abundance, height and coverage. Avicennia germinans is most abundant, tall and continuous along the south‐eastern outer coast of Louisiana, where the frequency of extreme freeze events is reduced (i.e., lower risk of mangrove freeze damage) by the buffering effects of comparatively warm Gulf of Mexico waters. Conversely, the risk of A. germinans freeze damage has historically been very high across Louisiana's Chenier Plain and within more inland wetlands in the Deltaic Plain.Main conclusionsOur analyses advance understanding of how the frequency of extreme freeze events controls the distribution, height and coverage of A. germinans near its northern range limit. In addition to informing climate‐smart coastal restoration efforts, our findings can be used to better anticipate and prepare for the tropicalization of temperate wetlands due to climate change.

Rapid peat development beneath created, maturing mangrove forests: ecosystem changes across a 25-yr chronosequence.

Mangrove forests are among the world's most productive and carbon-rich ecosystems. Despite growing understanding of factors controlling mangrove forest soil carbon stocks, there is a need to advance understanding of the speed of peat development beneath maturing mangrove forests, especially in created and restored mangrove forests that are intended to compensate for ecosystem functions lost during mangrove forest conversion to other land uses. To better quantify the rate of soil organic matter development beneath created, maturing mangrove forests, we measured ecosystem changes across a 25-yr chronosequence. We compared ecosystem properties in created, maturing mangrove forests to adjacent natural mangrove forests. We also quantified site-specific changes that occurred between 2010 and 2016. Soil organic matter accumulated rapidly beneath maturing mangrove forests as sandy soils transitioned to organic-rich soils (peat). Within 25yr, a 20-cm deep peat layer developed. The time required for created mangrove forests to reach equivalency with natural mangrove forests was estimated as (1) <15yr for herbaceous and juvenile vegetation, (2) ~55yr for adult trees, (3) ~25yr for the upper soil layer (0-10cm), and (4) ~45-80yr for the lower soil layer (10-30cm). For soil elevation change, the created mangrove forests were equivalent to or surpassed natural mangrove forests within the first 5 yr. A comparison to chronosequence studies from other ecosystems indicates that the rate of soil organic matter accumulation beneath maturing mangrove forests may be among the fastest globally. In most peatland ecosystems, soil organic matter formation occurs slowly (over centuries, millennia); however, these results show that mangrove peat formation can occur within decades. Peat development, primarily due to subsurface root accumulation, enables mangrove forests to sequester carbon, adjust their elevation relative to sea level, and adapt to changing conditions at the dynamic land-ocean interface. In the face of climate change and rising sea levels, coastal managers are increasingly concerned with the longevity and functionality of coastal restoration efforts. Our results advance understanding of the pace of ecosystem development in created, maturing mangrove forests, which can improve predictions of mangrove forest responses to global change and ecosystem restoration.

Nest site selection by reddish egrets in Florida

ABSTRACTUnderstanding nest site preferences for a species is a necessary component of conservation efforts because it allows managers to protect and create habitat that will promote population growth. We surveyed 305 sites with or near colonially nesting waterbirds for nesting reddish egrets (Egretta rufescens) during 2016 in Florida, USA, to identify factors that influenced the probability of occurrence and the abundance of nesting reddish egrets. Fifty‐eight of 150 (39%) sites with nesting waterbirds had ≥1 nesting pair of reddish egrets. Zero‐inflated Poisson models indicated that sites with a greater amount of foraging habitat within a 5‐km radius, with greater richness of nesting species, and, to a lesser extent, with shorter vegetation had a greater number of nesting reddish egrets. By contrast, the distance of an island from the mainland, an island's size, and an island's proximity to deep water did not influence the probability of occurrence or abundance of nesting reddish egrets. Our results suggest that effective management of large, speciose coastal rookeries are likely to benefit reddish egrets. Coastal restoration efforts that tightly link nest site management with high‐quality foraging habitat will be most likely to prove beneficial to reddish egrets. Long‐term management of reddish egrets will benefit from better knowledge of how sea level rise will alter the location and extent of foraging habitat. © 2018 The Wildlife Society.

SERUM CHEMISTRY OF FREE-RANGING NAZCA BOOBIES ( SULA GRANTI).

This study reports body mass and serum chemistry reference values of 121 male and 57 female Nazca boobies (Sulidae: Sula granti) from a colony on Isla Española, Galápagos Islands, Ecuador. Circulating aspartate aminotransferase, creatine kinase, lactate dehydrogenase, total protein, immunoglobulin Y, uric acid, blood urea nitrogen, triglycerides, cholesterol, and creatinine were quantified and analyzed by sex. Sex explained little variance in all examined variables except mass; females were heavier than males, as expected for sulids. Uric acid values had a bimodal distribution, likely reflecting differences in recent foraging success. Aspartate aminotransferase and creatine kinase values were similar to those reported in other sulids. Clinical health reference values are critical for practitioners investigating responses of seabirds to oil spills, coastal restoration efforts, or emerging diseases. These data from a species living in a relatively isolated and pristine area provide a valuable baseline for future health evaluations.

Wind Wave Behavior in Fetch and Depth Limited Estuaries

Wetland dominated estuaries serve as one of the most productive natural ecosystems through their ecological, economic and cultural services, such as nursery grounds for fisheries, nutrient sequestration, and ecotourism. The ongoing deterioration of wetland ecosystems in many shallow estuaries raises concerns about the contributing erosive processes and their roles in restraining coastal restoration efforts. Given the combination of wetlands and shallow bays as landscape components that determine the function of estuaries, successful restoration strategies require knowledge of wind wave behavior in fetch and depth limited water as a critical design feature. We experimentally evaluate physics of wind wave growth in fetch and depth limited estuaries. We demonstrate that wave growth rate in shallow estuaries is a function of wind fetch to water depth ratio, which helps to develop a new set of parametric wave growth equations. We find that the final stage of wave growth in shallow estuaries can be presented by a product of water depth and wave number, whereby their product approaches 1.363 as either depth or wave energy increases. Suggested wave growth equations and their asymptotic constraints establish the magnitude of wave forces acting on wetland erosion that must be included in ecosystem restoration design.

Facilitation shifts paradigms and can amplify coastal restoration efforts

Restoration has been elevated as an important strategy to reverse the decline of coastal wetlands worldwide. Current practice in restoration science emphasizes minimizing competition between out-planted propagules to maximize planting success. This paradigm persists despite the fact that foundational theory in ecology demonstrates that positive species interactions are key to organism success under high physical stress, such as recolonization of bare substrate. As evidence of how entrenched this restoration paradigm is, our survey of 25 restoration organizations in 14 states in the United States revealed that >95% of these agencies assume minimizing negative interactions (i.e., competition) between outplants will maximize propagule growth. Restoration experiments in both Western and Eastern Atlantic salt marshes demonstrate, however, that a simple change in planting configuration (placing propagules next to, rather than at a distance from, each other) results in harnessing facilitation and increased yields by 107% on average. Thus, small adjustments in restoration design may catalyze untapped positive species interactions, resulting in significantly higher restoration success with no added cost. As positive interactions between organisms commonly occur in coastal ecosystems (especially in more physically stressful areas like uncolonized substrate) and conservation resources are limited, transformation of the coastal restoration paradigm to incorporate facilitation theory may enhance conservation efforts, shoreline defense, and provisioning of ecosystem services such as fisheries production.

Dynamics of dissolved organic carbon and total dissolved nitrogen in Maryland's coastal bays

Dissolved organic matter (DOM) provides nutrients and energy subsidies for harmful algal blooms in Maryland's Coastal Bays (MCBs, USA). The composition, sources and dynamics of DOM in MCBs are not well known. In this study, dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were monitored monthly over a period of one year (July 2011 to June 2012) at 13 stations in the MCBs. Absorption and fluorescence spectroscopy were used to characterize DOM composition and track terrestrial inputs versus aquatic sources of DOM. Results show that DOC and TDN concentrations in the MCBs (187–501 μM and 19.4–40.6 μM) were comparable to eutrophic coastal waters in the United States but much higher than the mid-Atlantic Bight. This suggests that the MCBs are a DOM source for the coastal ocean. Spatially, nearshore sites had relatively higher DOC and TDN concentrations and terrestrially-derived aromatic DOM (indicated by high humification index) than the bays that were directly connected to the Atlantic Ocean. Seasonally, DOC from the main body of the MCBs (Chincoteague and Assawoman Bays) displayed a pronounced seasonal pattern with the highest values occurring in summer. Protein-like DOM from algal/bacterial inputs (indicated by high biological freshness index or fluorescence index) was also highest in summer but then decreased gradually until April. DOC concentrations at the nearshore site were highest in later spring, probably due to terrestrial inputs. Conversely, TDN concentrations in smaller bays with faster flushing rates (Newport, Sinepuxent and Isle of Wight Bays) were highest in April, probably due to watershed nitrogen inputs. This spring TDN peak was not apparent in the main body of the MCBs, which have longer flushing times (indicating stronger biological nitrogen uptake). This study suggests that DOM in eutrophic, shallow coastal bays such as the MCBs consists of a large fraction of protein-like components from local algal/microbial sources during summer. This enhanced primary productivity is likely fueled by watershed nitrogen inputs from agricultural and urban land use during spring. Further insights regarding spatiotemporal variations and controls of DOM abundance, composition and sources in the MCBs can be helpful in guiding and prioritizing coastal restoration efforts for reducing eutrophication and water quality degradation.

The Protective Value of Estuarine and Coastal Ecosystem Services in a Wealth Accounting Framework

Recent concern over the loss of estuarine and coastal ecosystems (ECEs) often focuses on an important service provided by these ecosystems, their role in protecting coastal communities from storms that damage property and cause deaths and injury. Certain ECEs, especially mangroves, marshes, seagrasses and near-shore coral reefs, may significantly reduce storm surges through attenuating waves. This function is key to the protective value of ECEs, which is used as a basis for coastal restoration efforts worldwide. In a wealth accounting framework, net domestic product (NDP) should be adjusted for the direct benefits provided by the current stock of this restored ecological capital but not for their indirect contributions in terms of protecting or supporting economic activity, property and human livelihoods. If ecosystem restoration leads to the creation of new ecological landscape, including transforming developed land back to ecological capital, then NDP must be further modified to reflect any capital revaluation that occurs. Both the current benefits of restoration and any capitalized land values must be adjusted if there is a risk of restoration failure. These issues encountered in a wealth accounting approach to the protective value of ECEs is illustrated with reference to the case of marsh creation in Louisiana, USA, in light of the 2012 Louisiana Coastal Master Plan.

The influence of grain size, grain color, and suspended-sediment concentration on light attenuation: Why fine-grained terrestrial sediment is bad for coral reef ecosystems

Sediment has been shown to be a major stressor to coral reefs globally. Although many researchers have tested the impact of sedimentation on coral reef ecosystems in both the laboratory and the field and some have measured the impact of suspended sediment on the photosynthetic response of corals, there has yet to be a detailed investigation on how properties of the sediment itself can affect light availability for photosynthesis. We show that finer-grained and darker-colored sediment at higher suspended-sediment concentrations attenuates photosynthetically active radiation (PAR) significantly more than coarser, lighter-colored sediment at lower concentrations and provide PAR attenuation coefficients for various grain sizes, colors, and suspended-sediment concentrations that are needed for biophysical modeling. Because finer-grained sediment particles settle more slowly and are more susceptible to resuspension, they remain in the water column longer, thus causing greater net impact by reducing light essential for photosynthesis over a greater duration. This indicates that coral reef monitoring studies investigating sediment impacts should concentrate on measuring fine-grained lateritic and volcanic soils, as opposed to coarser-grained siliceous and carbonate sediment. Similarly, coastal restoration efforts and engineering solutions addressing long-term coral reef ecosystem health should focus on preferentially retaining those fine-grained soils rather than coarse silt and sand particles.

Sex-Specific Movement Response of an Estuarine Sciaenid (Cynoscion nebulosus) to Freshets

During a 2.5-year acoustic telemetry study in a Louisiana estuary (Calcasieu Lake), two major freshets occurred (peak river flows >350 m3 s−1) in separate years and seasons, which provided an opportunity to evaluate the movement response of adult spotted seatrout (Cynoscion nebulosus) to large pulses of freshwater entering the estuary. A total of 172 spotted seatrout (101 females, 49 males, and 22 fish whose sex was unknown) were implanted with acoustic transmitters (battery life ~1 year) and released across four separate tagging events in the spring and fall of both 2007 and 2008; the movements of these fish were monitored by an estuarine-wide array of 60 receivers. Both freshets considerably reduced salinities in the upper bay, from 15–20 to 10 km) to the lower bay where salinities were higher (10–20). This sex-specific movement response to changing salinities has not been explored or demonstrated previously in spotted seatrout. Accordingly, these results provide environmental mangers with unique information on how salinity dynamics affect the accessibility of this economically and ecologically important species to both anglers and scientific surveys. This information also provides insight into how this species may respond to large-scale freshwater diversions that are being planned as part of coastal restoration efforts along the Gulf coast of the USA. More broadly, our results add to a limited but growing body of evidence that environmental preferences of estuarine and coastal fishes often differ between sexes and that the variable abiotic conditions, so characteristic of estuaries, can have important behavioral consequences for mobile organisms living in these systems.