Marsh Complex Research Articles

SOCIOCULTURAL VALUATION OF ECOSYSTEM SERVICES OF THE BAJO SINÚ MARSH COMPLEX IN THE DEPARTMENT OF CÓRDOBA, COLOMBIA

Wetlands are one of the most productive ecosystems on earth; however, they are threatened by multiple factors. Despite society's interdependence and continuous interaction with these ecosystems, they are often overlooked in management and decision-making. Therefore, this research aims to socially value the Bajo Sinú Marsh Complex (Marshes: Momil, Zapal, and Guartinaja) according to the importance that the local community and experts place on the ecosystem services they provide. For its development, an environmental characterization was carried out, covering the biophysical and social dimensions. Subsequently, different ecosystem services validated with professionals were identified and then valued through semi-structured surveys and analyzed using statistical software such as SPSS. The results show that, for the community, the most important ecosystem services are cultural (35.86%), regulation (33.72%), and provisioning (30.42%), while experts rank regulation as the most important (36.3%), followed by cultural services (35.1%) and provisioning (28.6%). The results provide a necessary knowledge base for the analysis of the use and exploitation of services, as well as for developing guidelines for the sustainable management of the resources provided by these wetlands.

Using Geospatial Analysis to Guide Marsh Restoration in Chesapeake Bay and Beyond

Coastal managers are facing imminent decisions regarding the fate of coastal wetlands, given ongoing threats to their persistence. There is a need for objective methods to identify which wetland parcels are candidates for restoration, monitoring, protection, or acquisition due to limited resources and restoration techniques. Here, we describe a new spatially comprehensive data set for Chesapeake Bay salt marshes, which includes the unvegetated-vegetated marsh ratio, elevation metrics, and sediment-based lifespan. Spatial aggregation across regions of the Bay shows a trend of increasing deterioration with proximity to the seaward boundary, coherent with conceptual models of coastal landscape response to sea-level rise. On a smaller scale, the signature of deterioration is highly variable within subsections of the Bay: fringing, peninsular, and tidal river marsh complexes each exhibit different spatial patterns with regards to proximity to the seaward edge. We then demonstrate objective methods to use these data for mapping potential management options on to the landscape, and then provide methods to estimate lifespan and potential changes in lifespan in response to restoration actions as well as future sea level rise. We account for actions that aim to increase sediment inventories, revegetate barren areas, restore hydrology, and facilitate salt marsh migration into upland areas. The distillation of robust geospatial data into simple decision-making metrics, as well as the use of those metrics to map decisions on the landscape, represents an important step towards science-based coastal management.

Морфолого-генетична та агрономічна характеристики контрастних за засоленням ґрунтів солонцевого комплексу Приорілля

The article presents the results of field and laboratory studies on the determination of the morphological, genetic and agronomic characteristics of the soils of the Solon complex of Prioril, contrasting in terms of salinity - the establishment of the peculiarities of the morphological structure of the profiles, the granulometric composition, and the parameters of the main agrochemical, salt and physicochemical parameters of the salt marsh of the meadow-black earth shallow salt marsh and black earth-meadow soil - as typical components of the salt complex of the Oril river valley. Standardized field survey and laboratory-analytical methods were used. It has been established that manifestations of halogenation increase with depth in the Luchno-chernozem salt marsh. Alkalinity in the humus-iluvial horizon increases to a strong degree, in deeper horizons - to a very strong one; the degree of salinity increases to medium, strong, and finally to very strong in the bedrock. According to the depth of the upper horizon of salt accumulation, this soil is classified as saline. The content of absorbed sodium in the humus-iluvial and illuvial horizons corresponds to the "saline" gradation. The chernozem-meadow soil is non-saline according to the content of toxic salts in the entire profile, there are no signs of physical and physico-chemical salinity. The content of the silt fraction in the salt marsh profile increases with depth and reaches its maximum value in the illuvial horizon, which is typical for salt marshes and is explained by the redistribution of soil colloids in the profile, the granulometric composition of the salt marsh in the humus-eluvial and illuvial horizons is light clay, in the humus-illuvial - medium clay. The profile of the chernozem-meadow soil is also heterogeneous in granulometric composition, which is heavier from medium loam in the humus horizon to heavy loam in the transitional horizons. The reason for this may be ancient alluvial processes that formed the soil-forming rock of the single-forest terrace. The content of humus in the salt pan in humus-eluvial and humus-iluvial horizons is average, the content of mineral (nitrate and ammonia) nitrogen is very low. The content of mobile potassium turned out to be elevated, and the content of mobile phosphorus was very high. In the chernozem-meadow soil, the content of humus in the humus arable horizon is high, in the first transitional one, it is average. The content of mineral nitrogen is low. The content of mobile phosphorus exceeds the upper limit of the high level by 3.5 times, and mobile potassium by 3.1 times, which is typical for the soils of closed depressions and is a consequence of long-term accumulation of surface runoff waters. Conclusions. The salt marsh complex of Priorillya with the number of salt marshes in the soil cover of about 50% is typical for the southern part of the Middle Forest Steppe in terms of the structure of soil profiles and soil halogenation. A characteristic feature of the studied salt marsh complex is the significant contrast of its components in terms of halogenation manifestations: at a short distance there are salt marsh highly saline salt marsh and leached chernozem-meadow soil without physical and physico-chemical signs of salinity.

Land Use and Land Cover Change in Kolonnawa Marsh, Colombo, Sri Lanka

Kolonnawa Marsh (KM) is one of important urban wetland ecosystem in Colombo, Sri Lanka and plays important roles by providing invaluable ecosystem services. KM belongs to the Colombo marsh complex that consists of Heen marsh, Kotte marsh and Parliament lake which surrounded by highly populated and industrialized sites. Owing to the continuous exploitation, reclamation for home states and industries in recent decades, this urban wetland has experienced significant changes. In order toreveal the dynamic changes of the KM at landscape level, the land cover change (LC) since 2000 to 2021 was investigated, using land use maps of 2000 and 2016 from Survey Department of Sri Lanka and Google earth satellite images in 2021. The analysis was conducted using ArcGIS 10.7. The results reviled that in the KM extent has decreased by 34.66 ha from the year 2000 to 30.09 ha in 2016 (reduction percentage 13.2%), while 30.09 ha in 2016 to 28.62 ha in 2021 (reduction percentage 1.47%). Water covered area, marshy area and area covered with woody perennials have been identified as major habitat types in KM. The ratio between water covered areas into marshy land area was reported as 3:6 in 2000 while 1:2 and 1:4 in 2016 and 2021 respectively. Further to that, 18.47 ha of marshy land area has been converted to area dominated with woody perennial in 2021. Therefore, it can be concluded that extent of the KM is decreasing over the study period while transforming to terrestrial ecosystem. Hence, immediate interventions are needed to preserve this valuable freshwater ecosystem.
 Keywords: Urban wetland, Remote sensing, Kolonnawa Marsh, Land cover

Vegetation and hydrology stratification as proxies to estimate methane emission from tidal marshes

Direct measurement of methane emissions is cost-prohibitive for greenhouse gas offset projects, necessitating the development of alternative accounting methods such as proxies. Salinity is a useful proxy for tidal marsh CH4 emissions when comparing across a wide range of salinity regimes but does not adequately explain variation in brackish and freshwater regimes, where variation in emissions is large. We sought to improve upon the salinity proxy in a marsh complex on Deal Island Peninsula, Maryland, USA by comparing emissions from four strata differing in hydrology and plant community composition. Mean CH4 chamber-collected emissions measured as mg CH4 m−2 h−1 ranked as S. alterniflora (1.2 ± 0.3) ≫ High-elevation J. roemerianus (0.4 ± 0.06) > Low-elevation J. roemerianus (0.3 ± 0.07) = S. patens (0.1 ± 0.01). Sulfate depletion generally reflected the same pattern with significantly greater depletion in the S. alterniflora stratum (61 ± 4%) than in the S. patens stratum (1 ± 9%) with the J. roemerianus strata falling in between. We attribute the high CH4 emissions in the S. alterniflora stratum to sulfate depletion likely driven by limited connectivity to tidal waters. Low CH4 emissions in the S. patens stratum are attributed to lower water levels, higher levels of ferric iron, and shallow rooting depth. Moderate CH4 emissions from the J. roemerianus strata were likely due to plant traits that favor CH4 oxidation over CH4 production. Hydrology and plant community composition have significant potential as proxies to estimate CH4 emissions at the site scale.

Modeling Marsh Dynamics Using a 3-D Coupled Wave-Flow-Sediment Model

Salt marshes are dynamic biogeomorphic systems that respond to external physical factors, including tides, sediment transport, and waves, as well as internal processes such as autochthonous soil formation. Predicting the fate of marshes requires a modeling framework that accounts for these processes in a coupled fashion. In this study, we implement two new marsh dynamic processes in the 3-D COAWST (coupled-ocean-atmosphere-wave sediment transport) model. The processes added are the erosion of the marsh edge scarp caused by lateral wave thrust from surface waves and vertical accretion driven by biomass production on the marsh platform. The sediment released from the marsh during edge erosion causes a change in bathymetry, thereby modifying the wave-energy reaching the marsh edge. Marsh vertical accretion due to biomass production is considered for a single vegetation species and is determined by the hydroperiod parameters (tidal datums) and the elevation of the marsh cells. Tidal datums are stored at user-defined intervals as a hindcast (on the order of days) and used to update the vertical growth formulation. Idealized domains are utilized to verify the lateral wave thrust formulation and show the dynamics of lateral wave erosion leading to horizontal retreat of marsh edge. The simulations of Reedy and Dinner Creeks within the Barnegat Bay estuary system demonstrate the model capability to account for both lateral wave erosion and vertical accretion due to biomass production in a realistic marsh complex. The simulations show that vertical accretion is dominated by organic deposition in the marsh interior, whereas deposition of mineral estuarine sediments occurs predominantly along the channel edges. The ability of the model to capture the fate of the sediment can be extended to model to simulate the impacts of future storms and relative sea-level rise (RSLR) scenarios on salt-marsh ecomorphodynamics.

Birds as a food base for mosquitoes – carriers of the causative agent of tropical malaria

The paper discusses the food supply of the vector of malaria mosquitoes of the genus Anopheles, which are birds of tropical regions of West Africa. Birds, as distant migrants, penetrate high latitudes and contribute to the spread of malaria in Europe and other countries of the northern hemisphere. The results of the studies show that the main role in the choice of prey objects by female Anopheles gambiae mosquitoes birds is played by the nesting and forage biotopes of birds, which are comfortable for mosquito breeding. Probably, female mosquitoes use non-feathered parts of the body of adult birds for feeding unfeathered or weakly feathered chicks in nests. The circulation of Plasmodium falciparum includes populations of birds, primarily water, near-water and marsh complexes, as well as birds, the development of which takes place in specific conditions of a closed space in holes, hollows and closed nests. The Anopheles gambiae mosquito in this system plays the role of a carrier of Plasmodium falciparum not only among populations of birds and mammals, but also among humans, which determines the range of tropical malaria, which is a natural focal vector-borne disease. The authors have identified 37 species of birds carriers of malaria in natural and anthropogenic biocoenoses of Mali (West Africa). The most numerous during the migration and nesting period are birds of the aquatic, near-water and meadow-bog complexes (herons, herons, waders) distant migrants on the territory of Russia and neighboring countries. The risk areas include, first of all, the southern regions Astrakhan Region, Rostov Region and Krasnodar Region.

Dynamics of Marsh‐Derived Sediments in Lagoon‐Type Estuaries

AbstractSalt marshes are valuable ecosystems that must trap sediments and accrete in order to counteract the deleterious effect of sea level rise. Previous studies have shown that the capacity of marshes to build up vertically depends on both autogenous and exogenous processes including ecogeomorphic feedbacks and sediment supply from in‐land and coastal ocean. There have been numerous efforts to quantify the role played by the sediments coming from marsh edge erosion on the resistance of salt marshes to sea level rise. However, the majority of existing studies investigating the interplay between lateral and vertical dynamics use simplified modeling approaches, and they do not consider that marsh retreat can affect the regional‐scale hydrodynamics and sediment retention in back‐barrier basins. In this study, we evaluated the fate of the sediments originating from marsh lateral loss by using high‐resolution numerical model simulations of Jamaica Bay, a small lagoonal estuary located in New York City. Our findings show that up to 42% of the sediment released during marsh edge erosion deposits on the shallow areas of the basin and over the vegetated marsh platforms, contributing positively to the sediment budget of the remaining salt marshes. Furthermore, we demonstrate that with the present‐day sediment supply from the ocean, the system cannot keep pace with sea level rise even accounting for the sediment liberated in the bay through marsh degradation. Our study highlights the relevance of multiple sediment sources for the maintenance of the marsh complex.

Sediment Dynamics of a Divergent Bay–Marsh Complex

Bay–marsh systems, composed of an embayment surrounded by fringing marsh incised by tidal channels, are widely distributed coastal environments. External sediment availability, marsh-edge erosion, and sea-level rise acting on such bay–marsh complexes may drive diverse sediment-flux regimes. These factors reinforce the ephemeral and dynamic nature of fringing marshes: material released by marsh-edge erosion becomes part of a bay–marsh exchange that fuels the geomorphic evolution of the coupled system. The dynamics of this sediment exchange determine the balance among seaward export, deposition on the embayment seabed, flux into tidal channels, and import to the marsh platform. In this work, we investigate the sediment dynamics of a transgressive bay–marsh complex and link them to larger-scale considerations of its geomorphic trajectory. Grand Bay, Alabama/Mississippi, is a shallow microtidal embayment surrounded by salt marshes with lateral erosion rates of up to 5 m year−1. We collected 6 months of oceanographic data at four moorings within Grand Bay and its tidal channels to assess hydrographic conditions and net sediment-flux patterns and augmented the observations with numerical modeling. The observations imply a divergent sedimentary system in which a majority of the suspended sediment is exported seaward, while a smaller fraction is imported landward via tidal channels, assisting in vertical marsh-plain accumulation, maintenance of channel and intertidal-flat morphologies, and landward transgression. These results describe a dynamic system that is responsive to episodic atmospheric forcing in the absence of a strong tidal signal and the presence of severe lateral marsh loss.

Elevation and accretion dynamics at historical plots in the Biloxi Marshes, Mississippi Delta

The objectives of this study were to examine changes in accretion and elevation change over periods of up to 15 years for the Biloxi marsh complex (BMC) in southeastern Louisiana, part of the Mississippi Deltaic Plain, identify factors affecting accretionary dynamics, and put these findings in the context of ongoing restoration. We present elevation and accretion data from Surface Elevation Table (SET) and feldspar marker horizon sites first established in 2003. The sites were clustered in two areas (East and West) in the central BMC on the eastern edge of the Mississippi delta. Accretion markers were used in conjunction with elevation measurements to calculate shallow subsidence. These data were analyzed along with similar data from nearby Coastwide Reference Monitoring System (CRMS) sites located around the periphery of the BMC. Elevation decreased at the Western sites by −0.35 ± 0.13 cm/yr, and increased at the Eastern and CRMS sites by 0.40 ± 0.03 cm/yr and 0.72 ± 0.09 cm/yr, respectively. The rate of accretion was similar at the Western (0.49 ± 0.14 cm/yr) and Eastern (0.64 ± 0.07 cm/yr) sites, and over twice as much (1.30 ± 0.11 cm/yr) at the CRMS sites. Shallow subsidence, calculated as the difference between vertical accretion and surface elevation change, was 0.76 ± 0.49 cm/yr at the Western sites, 0.23 ± 0.06 cm/yr at the Eastern sites, and 0.58 ± 0.11 cm/yr at the CRMS sites. These trends are consistent with the observation that sediment is brought in from Chandeleur Sound to the east and is attenuated as deposition occurs across the landscape from east to west, and that levee flank depressions associated with Bayou La Loutre, an abandoned Mississippi River distributary ridge, are causing locally high subsidence in the Western region. Without intervention, these localized areas of the Western region will be submerged within the next several decades at current rates of elevation loss and eustatic sea-level rise, while the Eastern sites and the wetlands on the periphery of the BMC are likely to keep pace with sea level rise well into the second half of this century. These results demonstrate the importance of accurate knowledge of both subsidence and accretionary dynamics in determining coastal wetland sustainability and restoration approaches.

Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

AbstractSalt marshes are dynamic systems able to laterally expand, contract, and vertically accrete in response to sea level rise. Here, we present the grand challenges that need to be addressed to fully characterize marsh morphodynamics. The review focuses on physical processes and quantitative models. Without predictive models, it is impossible to determine the future marsh evolution under accelerated sea level rise. In these models, one of the challenges is to resolve both horizontal and vertical dynamics within the same framework. Vertically, the marsh has to accumulate enough material to contrast rising water levels. Horizontally, marsh erosion at the ocean side must be compensated by landward expansion in forests, lawns, and agricultural fields. The dynamics of the marsh‐upland boundary are still not fully understood and will require more research in the upcoming years. The complexity of marsh vegetation is seldom captured in predictive models of marsh evolution. More research is needed to understand the effects of each species or species assemblages on hydrodynamics and sediment transport. Here, we further advocate that a sediment budget resolving all sediment fluxes in a marsh complex is the most important metric of marsh resilience. Characterization of these fluxes will enable to connect salt marshes to other landforms and to unravel feedbacks controlling the evolution of the entire coastal system. Current models of marsh evolution rely on sparse data sets collected at few locations. Novel remote sensing techniques will provide high‐resolution spatial data that will inform a new generation of computer models.

Different impacts of moderate human land use on the plant biodiversity of the characteristic Pannonian habitat complexes

Habitat complexes exhibit varying vulnerability to human land use and thus have different impacts on biodiversity. In this study, we analyzed the effect of moderate land use on the plant species diversity in six characteristic Pannonian habitat complexes: forest steppe complex on sand, on dolomite, and on loess, as well as alkaline habitat complex, freshwater marsh complex, and zonal broadleaf colline forest. We chose two regions for each complex, and in each region, we selected a 2 × 2 km “natural” study site in a mostly protected area, and a moderately used “managed” site of the same size. We compared the alpha, beta, and gamma diversities of the total and the specialist species pools of the natural-managed site pairs by applying stratified random sampling and novel bootstrap statistics.The gamma diversity of the specialist species pool was found to be the most sensitive indicator of naturalness. It was higher in the natural sites of the loess and dolomite forest steppe and the freshwater marshland complexes, while there were no significant diversity differences in the other complexes. The diversity comparisons showed a consistent pattern: there were either no significant diversity differences in any of the natural-managed pairs, or there were significant differences in the gamma diversities of the specialist species pool in both the natural-managed pairs.We concluded that the same differences in naturalness may represent different sensitivities to human management as characterized by differences in diversity measures. Three habitat complexes, the loess and dolomite forest steppe and the freshwater marshland, require more focused nature protection efforts in order to preserve the habitat diversity, especially in maintaining the remnants of the natural woody patches and the most inundated habitats of the marshlands. In the case of the other studied complexes, moderate human land use can be harmonized by nature protection goals.

An important biogeochemical link between organic and inorganic carbon cycling: Effects of organic alkalinity on carbonate chemistry in coastal waters influenced by intertidal salt marshes

Dissolved organic carbon (DOC) contains organic acid charge groups that contribute organic alkalinity (OrgAlk) to total alkalinity (TA). These effects are often ignored or treated as a calculation uncertainty in many aquatic CO2 studies. This study evaluated OrgAlk variability, sources, and characteristics in estuarine waters exchanged tidally with a groundwater-influenced salt marsh in the northeast USA. OrgAlk provided a biogeochemical link between organic and inorganic carbon cycling through its direct effects on pH, and thus CO2 system speciation and buffer capacity. Two main charge groups were identified including carboxylic and phenolic or amine groups. Terrestrial groundwater and in-situ production within salt marsh peat contributed OrgAlk to the tidal creek, with the former being a more significant source. Groundwater entering the marsh complex contained exceptionally high OrgAlk (> 150 µmol kg−1), and these compounds were preferentially preserved within the DOC pool during groundwater transport and mixing with coastal water. OrgAlk:DOC ratios in groundwater and marsh-influenced water varied across space and time. This highlights the insufficiency of using a fixed proportion of DOC to account for organic acid charge groups. Accounting for OrgAlk altered H+ concentrations by ∼1–41 nmol kg−1 (equivalent to a pH change of ∼0.03–0.26), pCO2 by ∼30–1600 μatm and buffer capacity by ∼0.00–0.14 mmol kg−1 at the relative OrgAlk contributions of 0.9–4.3% of TA observed in the marsh-influenced tidal water. Thus, OrgAlk may have a significant influence on coastal inorganic carbon cycling. Further theoretical calculations confirm that these concentrations of OrgAlk would have sizable impacts on both carbonate speciation and, ultimately, air-sea CO2 fluxes in different coastal environments, ranging from estuarine to shelf waters. A new conceptual model linking organic and inorganic carbon cycling for coastal waters is proposed to highlight the sources and sinks of organic acid charge groups, as well as their biogeochemical behaviors and mechanistic control on the CO2 system.

Pond Excavation Reduces Coastal Wetland Carbon Dioxide Assimilation

AbstractCoastal wetlands comprise important global carbon sinks; however, anthropogenic disturbance accompanied with accelerating sea level rise threaten their continued survival. In this study, we quantified habitat disturbance to salt marshes in Barnegat Bay, New Jersey, resulting from the construction of ponds for mosquito control. Geographic object‐based image analysis of high‐resolution four‐band aerial imagery revealed that over 7,000 ponds were constructed in the marsh complex with pond densities as high as 290 ponds per km2. Physical disturbance from pond creation and sediment dispersal extended to over 17% of the bay's tidal wetlands. By tracking recolonization of vegetation, we estimated that it took 5 years for 51% vegetation recovery and 10 years for 69% recovery, with complete recover (100%) not expected for more than 50 years. This suggests that efforts to extend the lifespan of drowning coastal wetlands through sediment additions might disrupt carbon dioxide assimilation, as effects of disturbance persist. Focusing on greenhouse gas exchange, our work found that areas of marsh vegetation contribute to carbon assimilation (−42 g C · m−2 · year−1), while ponds and areas of bare peat created by pond excavation were associated with carbon emissions (44 and 125 g C · m−2 · year−1, respectively). These results suggest that the conversion of wetlands to ponds—which is a significant driver of coastal wetland loss worldwide—may convert coastal wetlands from greenhouse gas sinks to sources. Additionally, quantifying the area of vegetation within a marsh (vs. bare ground or open water) is important for quantifying their greenhouse gas mitigation function.

A geospatially resolved wetland vulnerability index: Synthesis of physical drivers.

Assessing wetland vulnerability to chronic and episodic physical drivers is fundamental for establishing restoration priorities. We synthesized multiple data sets from E.B. Forsythe National Wildlife Refuge, New Jersey, to establish a wetland vulnerability metric that integrates a range of physical processes, anthropogenic impact and physical/biophysical features. The geospatial data are based on aerial imagery, remote sensing, regulatory information, and hydrodynamic modeling; and include elevation, tidal range, unvegetated to vegetated marsh ratio (UVVR), shoreline erosion, potential exposure to contaminants, residence time, marsh condition change, change in salinity, salinity exposure and sediment concentration. First, we delineated the wetland complex into individual marsh units based on surface contours, and then defined a wetland vulnerability index that combined contributions from all parameters. We applied principal component and cluster analyses to explore the interrelations between the data layers, and separate regions that exhibited common characteristics. Our analysis shows that the spatial variation of vulnerability in this domain cannot be explained satisfactorily by a smaller subset of the variables. The most influential factor on the vulnerability index was the combined effect of elevation, tide range, residence time, and UVVR. Tide range and residence time had the highest correlation, and similar bay-wide spatial variation. Some variables (e.g., shoreline erosion) had no significant correlation with the rest of the variables. The aggregated index based on the complete dataset allows us to assess the overall state of a given marsh unit and quickly locate the most vulnerable units in a larger marsh complex. The application of geospatially complete datasets and consideration of chronic and episodic physical drivers represents an advance over traditional point-based methods for wetland assessment.

Empirical observations and numerical modelling of tides, channel morphology, and vegetative effects on accretion in a restored tidal marsh

AbstractTidal marshes form at the confluence between estuarine and marine environments where tidal movement regulates their developmental processes. Here, we investigate how the interplay between tides, channel morphology, and vegetation affect sediment dynamics in a low energy tidal marsh at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island. Poplar Island is an active restoration site where fine‐grained material dredged from navigation channels in the upper Chesapeake Bay are being used to restore remote tidal marsh habitat toward the middle bay (Maryland, USA). Tidal currents were measured over multiple tidal cycles in the inlets and tidal creeks of one marsh at Poplar Island, Cell 1B, using Acoustic Doppler Current Profilers (ADCP) to estimate water fluxes throughout the marsh complex. Sediment fluxes were estimated using acoustic backscatter recorded by ADCPs and validated against total suspended solid measurements taken on site. A high‐resolution geomorphic survey was conducted to capture channel cross sections and tidal marsh morphology. We integrated simple numerical models built in Delft3d with empirical observations to identify which eco‐geomorphological factors influence sediment distribution in various channel configurations with differing vegetative characteristics. Channel morphology influences flood‐ebb dominance in marshes, where deep, narrow channels promote high tidal velocities and incision, increasing sediment suspension and reducing resilience in marshes at Poplar Island. Our numerical models suggest that accurately modelling plant phenology is vital for estimating sediment accretion rates. In‐situ observations indicate that Poplar Island marshes are experiencing erosion typical for many Chesapeake Bay islands. Peak periods of sediment suspension frequently coincide with the largest outflows of water during ebb tides resulting in large sediment deficits. Ebb dominance (net sediment export) in tidal marshes is likely amplified by sea‐level rise and may lower marsh resilience. We couple field observations with numerical models to understand how tidal marsh morphodynamics contribute to marsh resilience. © 2019 John Wiley & Sons, Ltd.

Movement ecology of a mobile predatory fish reveals limited habitat linkages within a temperate estuarine seascape

Large predatory fishes, capable of traveling great distances, can facilitate energy flow linkages among spatially separated habitat patches via extended foraging behaviors over expansive areas. Here, we tested this concept by tracking the movement of a large mobile estuarine fish, red drum (Sciaenops ocellatus). Specifically, we addressed the following two questions: (i) What are the spatial and temporal patterns of red drum movement (rates of dispersal) and activity space? (ii) Does red drum movement facilitate linkages among estuarine marsh complexes? Dispersal from the release location was greatest during the first 2 weeks at liberty before declining to less than 0.5 km·week–1 for the remainder of the study. Activity space initially increased rapidly before reaching an asymptote at 2.5 km2 2 weeks postrelease. Connectivity indices calculated among marsh complexes corroborated these observations, suggesting high residency and limited seascape-scale linkages via red drum movement behaviors. These data highlight potential within-estuary spatial structure for mobile fishes and could inform subsequent efforts to track energy flows in coastal food webs, predict the footprint of local habitat restoration benefits, and enhance the design of survey regimes to quantify overall population demography.

Nutrient Enrichment Alters Salt Marsh Fungal Communities and Promotes Putative Fungal Denitrifiers.

Enrichment of ecosystems with excess nutrients is occurring at an alarming rate and has fundamentally altered ecosystems worldwide. Salt marshes, which lie at the land-sea interface, are highly effective at removing anthropogenic nutrients through the action of macrophytes and through microbial processes in coastal sediments. The response of salt marsh bacteria to excess nitrogen has been documented; however, the role of fungi and their response to excess nitrogen in salt marsh sediments is not fully understood. Here, we document the response of salt marsh fungal communities to long-term excess nitrate in four distinct marsh habitats within a northern temperate marsh complex. We show that salt marsh fungal communities varied as a function of salt marsh habitat, with both fungal abundance and diversity increasing with carbon quantity. Nutrient enrichment altered fungal communities in all habitats through an increase in fungal abundance and the proliferation of putative fungal denitrifiers. Nutrient enrichment also altered marsh carbon quality in low marsh surface sediments where fungal response to nutrient enrichment was most dramatic, suggesting nutrient enrichment can alter organic matter quality in coastal sediments. Our results indicate that fungi, in addition to bacteria, likely play an important role in anaerobic decomposition of salt marsh sediment organic matter.

Tidal fluxes of mercury and methylmercury for Mendall Marsh, Penobscot River estuary, Maine

Tidal marshes are both important sites of in situ methylmercury production and can be landscape sources of methylmercury to adjacent estuarine systems. As part of a regional investigation of the Hg-contaminated Penobscot River and Bay system, the tidal fluxes of total suspended solids, total mercury and methylmercury into and out of a regionally important mesohaline fluvial marsh complex, Mendall Marsh, were intensively measured over several tidal cycles and at two spatial scales to assess the source-sink function of the marsh with respect to the Penobscot River. Over four tidal cycles on the South Marsh River, the main channel through which water enters and exits Mendall Marsh, the marsh was a consistent sink over typical 12-h tidal cycles for total suspended solids (8.2 to 41 g m−2), total Hg (9.2 to 47 μg m−2), total filter-passing Hg (0.4 to 1.1 μg m−2), and total methylmercury (0.2 to 1.4 μg m−2). The marsh's source-sink function was variable for filter-passing methylmercury, acting as a net source during a large spring tide that inundated much of the marsh area and that is likely to occur during approximately 17% of tidal cycles. Additional measurements on a small tidal channel draining approximately 1% of the larger marsh area supported findings at the larger scale, but differences in the flux magnitude of filter-passing fractions suggest a highly non-conservative transport of these fractions through the tidal channels. Overall the results of this investigation demonstrate that Mendall Marsh is not a significant source of mercury or methylmercury to the receiving aquatic systems (Penobscot River and Bay). While there is evidence of a small net export of filter-passing (<0.4 μm pore size) methylmercury under some tidal conditions, the mass involved represents <3% of the mass of filter-passing methylmercury carried by the Penobscot River.

Mapping wetlands in Nova Scotia with multi-beam RADARSAT-2 Polarimetric SAR, optical satellite imagery, and Lidar data

Wetland maps currently in use by the Province of Nova Scotia, namely the Department of Natural Resources (DNR) wetland inventory map and the swamp wetland classes of the DNR forest map, need to be updated. In this study, wetlands were mapped in an area southwest of Halifax, Nova Scotia by classifying a combination of multi-date and multi-beam RADARSAT-2 C-band polarimetric SAR (polSAR) images with spring Lidar, and fall QuickBird optical data using the Random Forests (RF) classifier. The resulting map has five wetland classes (open-water/marsh complex, open bog, open fen, shrub/treed fen/bog, swamp), plus lakes and various upland classes. Its accuracy was assessed using data from 156 GPS wetland sites collected in 2012 and compared to the one obtained with the current wetland map of Nova Scotia. The best overall classification was obtained using a combination of Lidar, RADARSAT-2 HH, HV, VH, VV intensity with polarimetric variables, and QuickBird multispectral (89.2%). The classified image was compared to GPS validation sites to assess the mapping accuracy of the wetlands. It was first done considering a group consisting of all wetland classes including lakes. This showed that only 69.9% of the wetland sites were correctly identified when only the QuickBird classified image was used in the classification. With the addition of variables derived from lidar, the number of correctly identified wetlands increased to 88.5%. The accuracy remained the same with the addition of RADARSAT-2 (88.5%). When we tested the accuracy for identifying wetland classes (e.g. marsh complex vs. open bog) instead of grouped wetlands, the resulting wetland map performed best with either QuickBird and Lidar, or QuickBird, Lidar, and RADARSAT-2 (66%). The Province of Nova Scotia’s current wetland inventory and its associated wetland classes (aerial-photo interpreted) were also assessed against the GPS wetland sites. This provincial inventory correctly identified 62.2% of the grouped wetlands and only 18.6% of the wetland classes. The current inventory’s poor performance demonstrates the value of incorporating a combination of new data sources into the provincial wetland mapping.