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Barrier islands occur in north-western Europe between the North Sea and the Wadden Sea along the coast of Denmark, Germany and the Netherlands. Geomorphological units such as dunes and salt marshes are built by wind, water and sediment. The biota also feed back to the units by trapping sand and silt, transported by water and wind thus (de)stabilizing the local substrate and are able to modify their own abiotic environment. Hence, we refer to them as biogeomorphological units, thus including the role of engineering biota. We consider seven units: tidal basin, island head, intertidal flats, dune arc complex, wash-over complex, island tail with salt marsh, and green beach. We focus on the well-studied West-Frisian island of Schiermonnikoog, the Netherlands, from which we integrated published data. The biogeomorphological units are built with bioengineering species, and in turn provide habitats for plant- and animal species. These communities are subject to succession until climax stages with various timescales. These temporal aspects are derived from long-term measurements in the field, including the study of chronosequences. Biogeomorphological units also affect each other, including feed-backs from animals, plants and micro-organisms. Based on that we present a conceptual model of this particular barrier island. Knowledge gaps that can be identified include 1) interactions among geomorphological units, 2) interactions among these units and bio-engineers to come to biogeomorphological units, and 3) multiple spatial-temporal scales. Human interference such as Aatmospheric deposition applies to all islands and is difficult to manage. Other human interferences may, however, differ among individual islands and their surroundings. They can be managed such as various intensities of fisheries, sand suppletion, extraction of groundwater, the attitude of local people towards artificial sand-drift dikes and livestock grazing.

The pulmonate gastropod genus Ellobium has its greatest diversity in the modern Indo-West Pacific Region (IWP). Its origin, however, is traced to the Early Oligocene of the Northeastern Atlantic and the Western Tethys Region. Two Ellobium species are documented from the Rupelian of France and Italy and a new species is recorded from the Chattian of Hungary: Ellobium kerwaensis nov. sp. The first records in the IWP are known from the Early Miocene, suggesting an eastward range expansion of the genus around the Oligocene/Miocene boundary, when Ellobium became extinct in the European seas. Extant Ellobium species are bound to habitats above the high tide line in salt marshes and mangroves. Comparable environmental requirements are expected for the fossil congeners. Ellobium may derive from Eocene ancestors, such as the Bartonian Eoellobium heberti from the Northeastern Atlantic. Eoellobium is introduced in this paper as a new genus.

There is considerable alongshore and regional variability in rates of erosion at salt marsh margins, and, with widespread loss of tidal wetlands, there is a need to better understand the factors which make salt marshes more or less likely to persist over time. The resistance of salt marsh sediments to erosion is influenced by physicochemical and biological properties. So far, research on salt marsh margin erosion has largely focused on external forcing and margin response at scales much larger than those on which these marsh properties vary, resulting in an underestimation of the potentially important role of internal substrate characteristics. In order to investigate the possible internal controls on substrate stability at this sub-metre scale, resistive properties and erosion response of sediments were compared between two contrasting UK salt marshes: coarse-grain dominated Hesketh Out Marsh West (northwest England) and clay-silt dominated Northey Island (southeast England). Both sites have adjacent ‘natural’ and restored salt marsh areas, and were selected to allow additional comparisons between these two wetland types. The thesis begins by establishing the context for understanding marsh margin erosion and the growing policy ambitions for salt marsh protection and creation. Current understanding of salt marsh erosion and the balance between external forcing and internal resistance is then reviewed, specifically linking this to the properties of sediment from restored salt marsh habitat and identifying a series of research opportunities. This study investigates the grain-to-bulk scale erosion response and physicochemical and biological sediment properties of vertical salt marsh sections from the two locations. A field experiment was designed to monitor the millimetre-to-centimetre scale response of exposed sediment sections to tidal flat conditions, with morphological change being measured using a Structure-from-Motion methodology. Morphological change is shown to be linked to both the grain-scale physicochemical properties of sediments and the bulk scale three-dimensional internal structural properties of the sediment section. There are site-specific and depth-specific (i.e. within-site) internal characteristics, resulting from longer-term processes of accumulation and colonisation (i.e. sediment supply, vegetation type), which can influence salt marsh morphological response to hydrodynamic forcing. The properties and erosion responses of restored marshes are distinct from their natural analogues. The onset of centimetre-scale erosion is shown to impact core-scale morphology in tight cumulative feedbacks over an experiment monitoring period of eight months. These results are compared to in-situ field measurements of sediment resistance (vane-measured shear strength), to assess whether such point-scale observations can be related to centimetre-scale erosion mechanisms. Results show that shear strength surveys measure different aspects of internal resistance to those observed in the field experiment. The value of such approaches is considered with reference to better predictions of salt marsh evolution, and management of restored sites. The vertical and three-dimensional internal resistive properties of sediment significantly influence erosion at exposed marsh margins. The research highlights ‘weaknesses’ at the centimetre-scale as possible drivers of larger-scale (e.g. metres-scale) mass failure and phases of lateral retreat, but suggests that this cascading effect is strongly affected by biophysical feedbacks. Thus, the identification of locations of structural ‘weakness’ at the between-site and within-site scales could provide a conceptual framework for better understanding and prediction of erosion at near-vertical salt marsh margins.

Barrier islands occur in north-western Europe between the North Sea and the Wadden Sea along the coast of Denmark, Germany and the Netherlands. Geomorphological units such as dunes and salt marshes are built by wind, water and sediment. The biota also feed back to the units by trapping sand and silt, transported by water and wind thus (de)stabilizing the local substrate and are able to modify their own abiotic environment. Hence, we refer to them as biogeomorphological units, thus including the role of engineering biota. We consider seven units: tidal basin, island head, intertidal flats, dune arc complex, wash-over complex, island tail with salt marsh, and green beach. We focus on the well-studied West-Frisian island of Schiermonnikoog, the Netherlands, from which we integrated published data. The biogeomorphological units are built with bioengineering species, and in turn provide habitats for plant- and animal species. These communities are subject to succession until climax stages with various timescales. These temporal aspects are derived from long-term measurements in the field, including the study of chronosequences. Biogeomorphological units also affect each other, including feed-backs from animals, plants and micro-organisms. Based on that we present a conceptual model of this particular barrier island. Knowledge gaps that can be identified include 1) interactions among geomorphological units, 2) interactions among these units and bio-engineers to come to biogeomorphological units, and 3) multiple spatial-temporal scales. Human interference such as Aatmospheric deposition applies to all islands and is difficult to manage. Other human interferences may, however, differ among individual islands and their surroundings. They can be managed such as various intensities of fisheries, sand suppletion, extraction of groundwater, the attitude of local people towards artificial sand-drift dikes and livestock grazing.

Ribbed mussels, Geukensia demissa, are marsh fauna that are used in coastal management and restoration due to the ecosystem services they provide. Ribbed mussel restoration efforts may be improved with a greater understanding of the environmental drivers of ribbed mussel distribution at multiple spatial scales to predict areas where restoration could be successful. This study sought to estimate the effects of within-marsh (4 m) and landscape (500 m) factors on ribbed mussel distribution. Ribbed mussel densities were surveyed at 11 sites along the coast of Georgia, USA, and overlaid with spatial data for within-marsh factors (elevation, distance to marsh features, slope) as well as landscape factors (percent cover by subtidal creek, forest, and development within a 500-m radius). The distribution model was then validated using three previously unsurveyed marshes and explained 55% of the variance in ribbed mussel abundance. Ribbed mussel abundances and occupancy were most sensitive to changes in within-marsh factors (elevation and distance to subtidal creeks, bodies of water inundated during the full tidal cycle) but were also sensitive to landscape features (percent landcover of forests and development). The highest ribbed mussel densities were found in mid-elevation areas (similar to 0.7 m NAVD88), far from subtidal creeks, and in marshes surrounded with forest and development. These results contrast with distributions in the northeastern USA, where ribbed mussels are distributed along subtidal creek banks. This work suggests that restoration may be most effective when focused on appropriate elevations and at locations away from the marsh-creek ecotone. National Sea Grant Office, National Oceanic and Atmospheric Administration, United States Department of Commerce [NA180AR4170084]; Georgia Department of Natural Resources; Georgia Southern University's Graduate Student Organization Published version We would like to thank Raven Hurt, Sarah Batchelor, Jada Daniels, and numerous undergraduates for help in the field and lab. We would also like to acknowledge Jan Mackinnon at the Georgia Department of Natural Resources, Dr. Rachel Guy at the Sapelo Island National Estuarine Research Reserve, and Stephanie Knox at the Cannon's Point Preserve for feedback on this research project, field site access, and logistical support. We would like to thank Dr. Risa Cohen, Department of Biology, Georgia Southern University, for input on the study design. We thank Dr. Sinead Crotty and three anonymous reviewers for their helpful comments on the manuscript. This publication was supported by an Institutional Grant (NA180AR4170084) to the Georgia Sea Grant College Program from the National Sea Grant Office, National Oceanic and Atmospheric Administration, United States Department of Commerce. Additional funding was provided by the Georgia Department of Natural Resources and the Georgia Southern University's Graduate Student Organization. Public domain – authored by a U.S. government employee

Salt marsh ecosystems provide critical climate mitigation ecosystem services through carbon sequestration. Sea level rise (SLR) has variable effects on these ecosystems, both driving marsh migration into upland areas and causing inundation and erosion that reduces marsh extent. How salt marsh carbon sequestration responds to SLR thus represents an important carbon cycle feedback to climate change. Here, we examine the consequences of one meter (1 m) of SLR for salt marsh ecosystem carbon sequestration for Long Island, New York and for the North Fork peninsula in far northeastern Long Island using three different assumptions for salt marsh carbon sequestration rates. For the entirety of Long Island, SLR will reduce future carbon sequestration by 22 million tons of carbon dioxide (CO2) by 2100 under the medium sequestration rate assumption compared to a no-SLR scenario. This represents a net loss of $137.5 billion in carbon sequestration ecosystem service value due to SLR. On the North Fork peninsula, however, SLR increases sequestration by 370,000 tons of CO2 with a medium sequestration rate assumption relative to a no-SLR scenario. However, the magnitude of uncertainty in future carbon sequestration due to different assumptions of carbon sequestration rates is greater than the impact of SLR on carbon sequestration, pointing to the need for the use of field-based measurement of sequestration rates in managing coastal ecosystem response to climate change.

Salt marshes are unique habitats between sea or saline lakes and land that need to be conserved from the effects of global change. Understanding the variation in functional structure of plant community along environmental gradients is critical to predict the response of plant communities to ongoing environmental changes. We evaluated the changes in the functional structure of halophytic communities along soil gradients including salinity, in Iranian salt marshes; Lake Urmia, Lake Meyghan, Musa estuary, and Nayband Bay (Iran). We established 48 plots from 16 sites in four salt marshes and sampled 10 leaves per species to measure leaf functional traits. Five soil samples were sampled from each plot and 30 variables were analyzed. We examined the changes in the functional structure of plant communities (i.e., functional diversity [FD] and community weighted mean [CWM]) along local soil gradients using linear mixed effect models. Our results showed that FD and CWM of leaf thickness tended to increase with salinity, while those indices related to leaf shape decreased following soil potassium content. Our results suggest that the variations in functional structure of plant communities along local soil gradients reveal the effect of different ecological processes (e.g., niche differentiation related to the habitat heterogeneity) that drive the assembly of halophytic plant communities in SW Asian salt marshes., Plant-Environment Interactions, 3 (1), ISSN:25756265

Salt marshes can generally be considered as sinks for metals. Research into salt marshes in Cornwall, UK suggests those estuaries heavily impacted by mining contamination are characterised by a less diverse vegetation compared with a significantly less-polluted site. Assessment using the National Vegetation Classification on the mid-marsh confirmed an Armeria maritima-dominated community was to be found in the most metal-enriched salt marsh of Restronguet Creek. However, this plant was co-dominant with Plantago maritima in the moderately contaminated marsh of Lelant and not present at all in the Camel, which has been subject to limited mining related contamination. Using canonical correspondence analysis, vegetation abundance data was compared with geochemical variables within the sediment. Metals were studied using extractions to signal bioavailability. P. maritima was not associated with the very high metal levels found in Restronguet Creek. A. maritima, had some association with soluble copper and was closer to the bulk of metals than P. maritima. As tolerance to adverse conditions and competitiveness are mutually exclusive, A. maritima, therefore, exists in a successional relationship with P. maritima. A. maritima then appears to be outcompeted by P. maritima in marshes with low metal loadings. Moderately high metal content results in a loss of competitiveness by P. maritima allowing A. maritima to co-dominate. In extremely metal-rich estuaries, however, P. maritima is unable to compete, allowing A. maritima to colonize the mid-marsh. Vegetation community may, therefore, be useful as an indicator of the level of metal contamination. European Geoscience Union General Assembly: vEGU21

Galician Rias are among the most productive ecosystems in the world. Consequently, the soils of their salt marshes and sediments of the intertidal flats show high organic matter contents, reactive Fe, and sulfate, which promote pyrite synthesis and accumulation, using sulfate for organic matter decomposition. This work studies the morphological variability and concentration of pyrites (individual crystals and framboids) in different geochemical environments found in the Ria de Ortigueira (salt marsh soils and bottom sediments in the inner, middle, and outer section), addressing their dynamics in the marsh-ria system in relation to the hydrodynamic characteristics defined by tides and river discharges. Framboidal pyrites were the dominant morphology in marsh soils and sediments in the middle and inner sections of the Ria, while isolated crystals dominated its outer section. The results showed that lower marsh soils (colonized by Spartina) are the most favorable environment for pyrite synthesis, showing high pyritic Fe concentrations and high degrees of pyritization, largely exceeding the values observed in sediments from Galician Rias and from most sedimentary environments worldwide. However, the amount of framboidal pyrites present in the lower marsh (SPE: 4–5 × 104 framboids) was clearly lower than in bottom sediments of the inner and middle part of the Ria de Ortigueira (∼2–7 × 106 framboids), mainly due to the fact that pyrites were found to form large framboids in lower salt marsh soils. Thus, the amount of framboidal pyrites does not seem to be a good indicator of redox conditions in modern marine sediments. Pyrite crystals found in the sediments of the Ria showed poorly defined vertices and facets, indicating their degradation and suggesting that a significant amount of the pyrites found in the middle and inner sections derive from marsh collapse. Finally, the output of framboidal pyrites towards the outer Ria de Ortigueira reflects the low intensity of residual flows in this Ria. Therefore, the pyrites observed in the outer section consisted only of isolated crystals, presumably formed in situ under low sulfate-reducing activity conditions SI

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.

Salt marshes are important coastal habitats and provide ecosystem services to surrounding communities. They are, however, threatened by accelerating sea-level rise and sediment deprivation due to human activity within upstream catchments, which result in their drowning and a reduction in their extent. Rising seas are also leading to an expansion of coastal flooding protection infrastructures, which might also represent another serious if poorly understood threat to salt marshes due to effects on the resuspension and accumulation of sediment during storms. Here, we use observations from the Venice Lagoon (Italy), a back-barrier system with no fluvial sediment input recently protected by storm-surge barriers, to show that most of the salt-marsh sedimentation (more than 70% in this case) occurs due to sediment reworking during storm surges. We also prove that the large, yet episodic storm-driven sediment supply is seriously reduced by operations of storm-surge barriers, revealing a critical competition between the objectives of protection against coastal flooding and preservation of natural ecosystems. Without complementary interventions and management policies that reduce barrier activations, the survival of coastal wetlands is even more uncertain. Sediment supply to the Venice Lagoon is substantially reduced by flood barriers inhibiting storm-related sediment reworking and transport, according to observations through multiple storm events before and after barrier installation.

Runnelling is a minor and successful form of open marsh water management developed in Australia in the 1980s and integrated into mosquito control programs in the 1990s. While long-term monitoring and investigation of impacts has continued for one site, until recently there has been no assessment of operational runnelling more broadly across mosquito control agencies. This study addresses this issue. Forty-seven runnelled saltmarsh sites were assessed for runnel efficacy, function and condition. Issues impacting on runnel function, including both ecological and geomorphic processes, were noted. Data were mostly acquired from site inspections and discussions with mosquito control staff, with some records as available. Most runnels were constructed between 1990 and 2005, mainly using a dedicated runnelling machine. Almost half (49%) continued to contribute to mosquito control efficacy, either in part or fully, while half did not (51%). Efficacy was attributed to runnels being correctly configured in design, layout and construction and to relatively recent maintenance. Conversely, diminished efficacy was mostly attributed to ineffective hydrologic function, caused by vegetation blockages, erosion and/or deposition. Runnels alter tidal hydrology, affecting other ecological and geomorphic processes. These processes need to be managed to maintain runnel function and it is essential that monitoring and maintenance records are kept. Runnels can control mosquitoes for decades, provided ongoing monitoring and maintenance of the runnel system focusses on responding to early signs of impacts. Restoring degraded runnels should be undertaken using a runnel machine, however, changing environmental conditions may mean that a runnel should be ‘decommissioned’ instead.

The effects of sea level rise and coastal saltwater intrusion on wetland plants can extend well above the high-tide line due to drought, hurricanes, and groundwater intrusion. Research has examined how coastal salt marsh plant communities respond to increased flooding and salinity, but more inland coastal systems have received less attention. The aim of this study was to identify whether ground layer plants exhibit threshold responses to salinity exposure. We used two vegetation surveys throughout the Albemarle-Pamlico Peninsula (APP) of North Carolina, USA to assess vegetation in a low elevation landscape (≤ 3.8 m) experiencing high rates of sea level rise (3–4 mm/year). We examined the primary drivers of community composition change using Non-metric Multidimensional Scaling (NMDS) and used Threshold Indicator Taxa Analysis (TITAN) to detect thresholds of compositional change based on indicator taxa, in response to potential indicators of exposure to saltwater (Na, and the Σ Ca + Mg) and elevation. Salinity and elevation explained 64% of the variation in community composition, and we found two salinity thresholds for both soil Na+ (265 and 3843 g Na+/g) and Ca+ + Mg+ (42 and 126 µeq/g) where major changes in community composition occur on the APP. Similar sets of species showed sensitivity to these different metrics of salt exposure. Overall, our results showed that ground layer plants can be used as reliable indicators of salinity thresholds in coastal wetlands. These results can be used for monitoring salt exposure of ecosystems and for identifying areas at risk for undergoing future community shifts.

The biogeochemistry of tidal marsh sediments facilitates the transformation of mercury (Hg) into the biologically available form methylmercury (MeHg), resulting in elevated Hg exposures to tidal marsh wildlife. Saltmarsh and Acadian Nelson’s sparrows (Ammospiza caudacutua and A. nelsoni subvirgatus, respectively) exclusively inhabit tidal marshes, potentially experiencing elevated risk to Hg exposure, and have experienced range-wide population declines. To characterize spatial and temporal variation of Hg exposure in these species, we sampled total mercury (THg) in blood collected from 9 populations spanning 560 km of coastline, including individuals resampled within and among years. Using concurrent nesting studies, we tested whether THg was correlated with nest survival probabilities, an index of fecundity. Blood THg ranged from 0.074–3.373 µg/g ww across 170 samples from 127 individuals. We detected high spatial variability in Hg exposure, observing differences of more than 45-fold across all individuals and 8-fold in mean blood THg among all study plots, including 4-fold between study plots within 4 km. Intraindividual changes in blood Hg exposure did not vary systematically in time but were considerable, varying by up to 2-fold within and among years. Controlling for both species differences and maximum water level, the dominant driver of fecundity in this system, nest survival probability decreased by 10% across the full range of female blood THg concentrations observed. We conclude that Hg has the potential to impair songbird reproduction, potentially exacerbating known climate-change driven population declines from sea-level rise in saltmarsh and Acadian Nelson’s sparrows.

The unprecedented size of the deepwater horizon oil spill and scope of the subsequent response elicited intense and sustained interest in microbial responses to oiling, especially in salt marshes, which have featured prominently in debates about best practices to prevent and remediate oiling of vulnerable ecosystems. A number of studies have examined salt marsh soil microbial communities following the spill, but most have primarily concentrated on prokaryotes. The extent to which oiling elicited shifts in fungal diversity and community composition remains unclear. Here we present spatial and temporal comparisons of salt marsh soil fungal communities at two southern Louisiana salt marshes with contrasting oiling histories. We profiled fungal communities in 2013 alongside corresponding measurements of polycyclic aromatic hydrocarbons to assess whether and how responses to oiling are distinguishable from natural heterogeneity. Analyses based on high-resolution unbiased spatial sampling demonstrated that fungal communities did not align with shoreline classification of oiling less than three years after initial oiling, despite observable differences in oil residues and secondary oiling. Notably, extensive sampling allowed delineation of benchmark sampling thresholds and illustrated the value of using ranked differentials of relative abundance to characterize soil fungal communities. Our findings highlight the need for combining high-resolution sampling with judgment-based and systematic sampling approaches to accurately capture responses of salt marsh soil fungal community to oiling.

Tidal marsh loss at Blackwater National Wildlife Refuge (NWR) has been a major concern of refuge managers in recent decades. The approximately 2,035 hectares (5,028 acres) of tidal marsh that have converted to open water in Blackwater NWR since 1938 (Scott et al. 2009) represent one of the most significant areas of marsh conversion within the Chesapeake Bay. In 2013, a suite of climate adaptation strategies focused on sea level rise was developed for Blackwater NWR and surrounding areas of Dorchester County by the Blackwater Climate Adaptation Project (BCAP). The BCAP is a collaboration of The Conservation Fund, Audubon Maryland-DC, and the U.S. Fish and Wildlife Service, assisted by the Maryland Department of Natural Resources (MD DNR), U.S. Geological Survey, and others. In 2016, the BCAP implemented a thin-layer placement (TLP) project at Shorter’s Wharf in Blackwater NWR on 16 hectares (40 acres) of subsiding and fragmenting tidal marsh dominated by Schoenoplectus americanus, Spartina alterniflora, and Spartina patens. The purpose of the project was to increase the 16 hectares’ (40 acres’) resiliency to climate-driven sea level rise and storm impacts. The project built up the marsh elevation by applying thin layers of sediment dredged from the adjacent Blackwater River. The sediment enhancement was designed to extend the longevity of the marsh and increase its resiliency by raising its surface elevation in relation to the tidal regime and to return the habitat to its prior high-marsh condition with S. patens dominating. The colonization of this site by saltmarsh sparrow would be an indicator of success in reaching this goal. Dredging operations in November and December 2016 placed approximately 19,900 cubic meters (26,000 cubic yards) of sediment on the project site. Post-restoration elevations obtained one year after material placement indicated that, although the target elevations were achieved in 78% of the surveyed placement area, the material was not distributed uniformly. Coarser material tended to stack up at the discharge location while the grain size declined and the slopes flattened toward the periphery of the discharge area. In 2017, natural vegetation had regenerated through the placed sediment with vigorous regrowth of S. americanus and S. alterniflora . This regrowth was supplemented with hand-planting of more than 200,000 plugs of S. patens. Vegetation monitoring is ongoing to determine the plant composition evolution within the placement site. Pre-dredge and post-dredge bathymetric surveys reveal 70% accretion nearly two years after dredging within the borrow area footprint.

We present a high resolution multi-proxy study about environmental changes that occurred during the Holocene sea-level transgression and successive highstand (7–5.5 Kyr) in the central zone of Bahia Samborombon (∼35.6° S), Argentina. This study, one of the first in the area that integrates geomorphological and paleontological proxy data (pollen, non-pollen palynomorphs, foraminifera and mollusk shells), and focusing on a short time interval, offers the advantage of recognizing environmental and vegetation changes in a more comprehensive way. The aim of this work is to reconstruct the salt marsh vegetation history and paleoenvironmental changes; and to develop a model of the geomorphological evolution during the mid-Holocene sea-level transgressive phase. Between 6700 cal yr BP and 6500 cal yr BP, several rapid environmental changes took place. Those changes affected vegetation and microfauna, as well as the geomorphological features. During this period, middle to high salt marsh vegetation developed in an extensive and open tidal plain, where wide and long paleo tidal channels were flowing. Between 6500 and 6220 cal yr BP, the salt marsh transitioned into low salt marsh one as a response to a continued rise in sea level, resulting in the landward transgression of the coastline. The relative sea level reached the highstand between 6220 and 5500 cal yr BP and, consequently, extensive inundation of the coastal plain took place, except for the elevated areas such lunettes and ridges. After 5500 cal yr BP, seaward prograding beach and sand ridges formed in response to the onset of a regressive phase. Since then, the ancient tidal plain, extending ∼10 km from the present coastline, has been subjected to aeolian and pedogenetic processes.

The present paper deals with the historical evolution of the northern Bay of Cadiz (SW Spain) between the last eustatic maximum (6.5 ka BP) and the present day, by means of a series of independent proxies. The zone is constituted by the tidal estuary of the Guadalete River, filled with saltmarsh sediments during the late Holocene, due to the sheltering of the zone by a confining outer sandy barrier. The northern border of the Bay records an urban settlement of Phoenician Age (first millennium BC), Dona Blanca. A detailed survey was made in the contact between the Phoenician city and the saltmarshes in order to detect other possible urban structures related to the morphological and sedimentary evolution of this environment during historical times. Two campaigns with GPR Stream-X array were carried out as well as aerial imaging and topographic survey with UAV. In parallel, a total of 8 boreholes were made in different parts of the saltmarshes, including radiocarbon dating of selected samples for estimating sedimentation rates in the saltmarshes. Results obtained by georadar prospection and UAV survey revealed the presence of a second urban settlement on the marginal sedimentary plain, very probably installed upon a sandy fluvial island of the Guadelete River. The urban remains, of Punic Age, are partly covered by clay sediments due to the subsequent evolution of these saltmarshes, where sedimentation rates of up to nearly 2.4 mm/yr have been estimated for environments close to fluvial and/or tidal channels and hence more affected by sediment aggradation during flooding episodes. In recent times, river regulation by dams and the artificial desiccation and cropping of the saltmarshes have interrupted the natural trend of the area towards sedimentary silting up.

The San Francisco Bay has the largest concentration of salt marshes in the state of California. In the last 170 years, the vast majority of the historic tidal wetlands in the Bay have been significantly altered or destroyed due to diking, filling and other processes. Many of the remaining marshes have been impacted by changing sedimentation regimes and related loadings of pollutants such as heavy metals (Sr, Al, Fe, Ti, Cu, Pb, Ni, Zn) over this period, making ecological trajectories and resilience to disturbance uncertain. Here we examine changing sediment accretion rates, coupled with the longest and highest resolution heavy metal accumulation data from three San Francisco Bay marshes, to examine European impacts in the context of earlier Holocene variability. The results are consistent with larger-scale analyses and indicate that European alterations of landscapes and shorelines had geographically variable impacts on marsh sediment accumulation. Despite differential impacts on net sediment accretion, initial European impacts appear to have decreased the proportion of organic material in the marsh sediments, likely due to the delivery of eroded inorganic sediment from landscapes and shorelines. The results confirm significant European impacts on the geochemistry of marshes in the San Francisco Bay over the last ~150–200 years. Post-European arrival levels of Pb are unprecedented throughout the earlier Holocene. However, these values have declined in recent years. Concentrations of Sr, Ti, Cu, Ni, and Zn also increased following European arrival. Our results show that post-European concentrations are not so far removed compared to pre-European maximum concentrations. As sedimentation regimes and emissions of Pb and delivery of other metals have decreased, and as organic productivity increased on the marshes, environmental trajectories are shifting back towards their immediate pre-European conditions.

Tidal salt marshes are known to accumulate “blue carbon” at high rates relative to their surface area, which render these systems among the Earth's most efficient carbon (C) sinks. However, the potential for tidal salt marshes to mitigate global warming remains poorly constrained because of the lack of representative sampling of tidal marshes from around the globe, inadequate areal extent estimations, and inappropriate dating methods for accurately estimating C accumulation rates. Here we provide the first estimates of organic C storage and accumulation rates in salt marshes along the Pacific coast of Canada, within the United Nations Educational, Scientific and Cultural Organization (UNESCO) Clayoquot Sound Biosphere Reserve and Pacific Rim National Park Reserve, a region currently underrepresented in global compilations. Within the context of other sites from the Pacific coast of North America, these young Clayoquot Sound marshes have relatively low C stocks but are accumulating C at rates that are higher than the global average with pronounced differences between high and low marsh habitats. The average C stock calculated during the past 30 years is 54 ± 5 Mg C ha−1 (mean ± standard error), which accounts for 81 % of the C accumulated to the base of the marsh peat layer (67 ± 9 Mg C ha−1). The total C stock is just under one-third of previous global estimates of salt marsh C stocks, likely due to the shallow depth and young age of the marsh. In contrast, the average C accumulation rate (CAR) (184 ± 50 g C m−2 yr−1 to the base of the peat layer) is higher than both CARs from salt marshes along the Pacific coast (112 ± 12 g C m−2 yr−1) and global estimates (91 ± 7 g C m−2 yr−1). This difference was even more pronounced when we considered individual marsh zones: CARs were significantly greater in high marsh (303 ± 45 g C m−2 yr−1) compared to the low marsh sediments (63 ± 6 g C m−2 yr−1), an observation unique to Clayoquot Sound among NE Pacific coast marsh studies. We attribute low CARs in the low marsh zones to shallow-rooting vegetation, reduced terrestrial sediment inputs, negative relative sea level rise in the region, and enhanced erosional processes. Per hectare, CARs in Clayoquot Sound marsh soils are approximately 2–7 times greater than C uptake rates based on net ecosystem productivity in Canadian boreal forests, which highlights their potential importance as C reservoirs and the need to consider their C accumulation capacity as a climate mitigation co-benefit when conserving for other salt marsh ecosystem services.

The presence of plastic on marine coasts has been widely reported throughout the world. However, these materials have received little attention in coastal wetlands, particularly salt marshes. The abundance, size, type, color, and polymer distribution of large micro- (1-5mm), meso- (5-25mm), and macro-plastics (25-100mm) in eight salt marshes of the Bahia Blanca Estuary were analyzed in this study. Plastics from mudflat, low-salt marsh, and high-salt marsh sediments, and plant-litter from the storm line were isolated by wet sieving and flotation with NaCl saturated solution. The shape, size and color were determined visually under a stereomicroscope and the polymeric composition was determined by FTIR-ATR. The concentrations always followed the same pattern: storm-line plant litter¿high-salt marsh sediments¿low-salt marsh sediments¿mudflat sediments. The most contaminated salt marshes were those near the mouth of the Maldonado stream and an illegal landfill. The relative abundance of each type of plastic varied within the salt marsh, fragments and pellets followed the same pattern as concentrations. Furthermore, this percentage varied between salt marshes, owing primarily to the source to which they were exposed. Thus, those near dumps and sewage discharges had more films and fibers, respectively, while those near the main channel had more pellets. In terms of polymer distribution, 40.5% of the 1600 items analyzed were PELD, followed by 29% PEHD, 20.4% PP, and 4.1% EPS. The films were mostly PELD¿PP¿PEHD, the fragments were PEHD¿PP¿PELD and pellets were PEHD¿PELD. At the spatial level, the relative abundance of each polymer depended on the relative abundance of each plastic shape/type. Finally, we highlight that this study is the first in salt marshes around the world and is focusing on management strategies to improve the coastal wetland quality. Also see: https://micro2022.sciencesconf.org/427357/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

This study assessed for the first time the occurrence of legacy persistent organic pollutants (POPs), specifically organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), in plastics ranging from 1 to 25 mm (micro/meso-plastics) and 25 to 100 mm (macroplastics) and sediments from salt marshes at the Bahia Blanca Estuary, Argentina. These ecologically important ecosystems are located in the intertidal zone of a coastal environment heavily impacted by human activity, including deep-water ports, petrochemical complexes, and cities with populations of over 400,000 inhabitants with inadequate environmental management. Results showed that the average concentrations and detection frequency of POPs were substantially higher in the plastics than in the sediments: 167.4 ng/g, 25.2 ng/g and 2.7 ng/g, for micro/meso-plastics, macro-plastics, and sediments, respectively, showing the high capacity of plastics to accumulate organic substances. In regards to the environmental levels of the POPs series, in general PCBs¿DDTs¿HCHs¿HCB¿PeCB with independence of the location and matrix. Exceptions emerged close to an open dump and industrial effluents where HCB and PeCB were dominant. The spatial distribution varied depending on the POPs group series and the matrix; however, the levels of DDTs and HCHs were consistently low throughout the sedimentary record. While HCH and DDT were higher in plastics near Maldonado River discharge. Meanwhile, higher PCBs, HCB, and PeCB levels correlated urban-industrial facilities and open dumps. This is the first study on the presence of POPs in plastics from coastal wetlands around the world, as well as the first to assess the association of these chemicals in environmental plastics from Argentina. Also see: https://micro2022.sciencesconf.org/427372/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

A multidisciplinary group of salt marsh professionals from Maine to Virginia participated in a collaborative learning exchange to improve restoration for the overall health and resilience of coastal wetlands. This was an unprecedented forum through which participants representing different geographies, backgrounds, and roles in salt marsh management were able to share and learn from one another to develop the best available restoration methods for on-the-ground projects that address multiple benefits. By including mosquito control agencies, restoration practitioners, regulatory agencies, academic researchers, and conservation organizations in the learning exchange, we developed an understanding and acceptance of different approaches. Regulators learned about project ideas and contributed to project designs in early development stages. Collaborating while engaged in on-the ground projects enabled participants to implement lessons learned in real time. Field trips to restoration sites at different stages of development allowed a greater and more fluid exchange of ideas and practical implementation advice. Practitioners leveraged resources and developed new collaborations. Lessons learned and shared through this faster and more flexible forum will inform the design, implementation, and monitoring of restoration projects across the region and improve overall marsh health and resilience in the face of climate change. Learning exchanges like this should be used more frequently to improve the efficiency and effectiveness of coastal restoration particularly when there is a windfall of cash and a short window of opportunity such as with post-disaster federal spending.

The coastal zone of China has experienced large increases in population, economy and urbanization since the early 1980s. Many studies have reported the loss, degradation and fragmentation of coastal wetlands in China at local to regional scales. To date, at the national scale, our knowledge of the spatial distribution, inter-annual variation and multi-decadal trends of coastal wetlands in China remains very limited. Here we analysed ~62,000 Landsat-5, -7 and -8 images over the period 1984–2018 and generated maps of coastal wetlands for individual years in China at 30-m spatial resolution. We found that coastal wetland area significantly decreased between 1984 and 2011. We also found a substantial increase in saltmarsh area and a stable trend of tidal flat area since 2012, driven by reduced anthropogenic activities and increased conservation and restoration efforts. These coastal wetland maps for the period 1984–2018 are invaluable for improvement of coastal wetland management and sustainability in China. China’s coasts have become more populous and urbanized. This study finds a rebound in the area of coastal wetlands, reflecting recent conservation and restoration, with large losses between 1984 and 2011 followed by increases in saltmarsh area and stabilization of tidal flats.

Macrobenthos organisms are vital ecological components of intertidal wetlands. This work studied effects of non-native mangrove rehabilitation (Kandelia obovata) and salt marsh invasion (Spartina alterniflora) on macrobenthos communities in Ximen Island (Zhejiang, China). The macrobenthos communities were compared between rehabilitated K. obovata forests of five different stand ages (2-, 8-, 11-, 16-, and 60-year-old) and adjacent S. alterniflora marsh and non-vegetated mudflat. Compared to the mudflat, S. alterniflora increased the abundance, Shannon–Wiener diversity index (H’), and Margalef's richness index (d’) of macrobenthos. Gastropoda abundance was high in the S. alterniflora marsh, whereas, malacostraca biomass was low. Within mangrove forests, macrobenthos abundance was positively correlated with the stand age of mangroves (Spearman Correlation, P

The El Nino–Southern Oscillation (ENSO) strongly influences climate and hydrology on the planet and may drive the structure and functioning of estuarine communities. However, the effects of the ENSO on coastal areas are dependent on the spatial scale and the intrinsic characteristics of the estuary. Over six years (2013 to 2018), we investigated the variability in macrobenthic secondary production of Spartina alterniflora marshes and adjacent unvegetated areas in a subtropical coastal lagoon in Southern Brazil. We tested whether the ENSO events affect the benthic secondary production of these two habitats. Most environmental variables (air temperature, northward surface stress and northward wind component) did not differ significantly between ENSO phases, except for precipitation. Monthly precipitation totals during El Nino months were 70% higher than neutral and La Nina conditions. A total of 25,862 organisms (8,191 in salt marshes and 17,671 in unvegetated areas) belonging to 39 taxa (25 in marshes and 34 unvegetated areas) were collected throughout the study. The tanaid Monokalliapseudes schubarti, and Nereididae polychaeta Laeonereis acuta were largely the most abundant species in both vegetated and unvegetated areas, with higher biomass and productivity. The secondary production in unvegetated areas increased 216%, from a mean of 107.5 g C/m2/y to 336.4 g C/m2/y during El Nino. However, the salt marshes responded differently than the unvegetated areas, with secondary production more stable over the time, with highest value of 164.2 g C/m2/y-1. There is also a distinction in the effects on different species, L. acuta showed an increase only in biomass (from 0.024 to 0.042 g DW/0.03m2), whereas M. schubarti increased both in biomass (more than 4000%) and density (more than 5000%). In contrast, no significant differences in density, biomass and secondary production for both species were detected over time in the salt marshes. Our findings indicate that large scale climatic variations, such as ENSO, can strongly affect estuarine density, biomass and secondary production, but salt marshes buffer El Nino effects on benthic associations.

Tidal wetlands are a significant source of dissolved organic matter (DOM) to coastal ecosystems, which impacts nutrient cycling, light exposure, carbon dynamics, phytoplankton activity, microbial growth, and ecosystem productivity. There is a wide variety of research on the properties and sources of DOM; however, little is known about the characteristics and degradation of DOM specifically sourced from tidal wetland plants. By conducting microbial and combined UV exposure and microbial incubation experiments of leachates from fresh and senescent plants in Chesapeake Bay wetlands, it was demonstrated that senescent material leached more dissolved organic carbon (DOC) than fresh material (77.9 ± 54.3 vs 21.6 ± 11.8 mg DOC L−1, respectively). Degradation followed an exponential decay pattern, and the senescent material averaged 50.5 ± 9.45% biodegradable DOC (%BDOC), or the loss of DOC due to microbial degradation. In comparison, the fresh material averaged a greater %BDOC (72.6 ± 19.2%). Percent remaining of absorbance (83.3 ± 26.7% for fresh, 90.1 ± 10.8% for senescent) was greater than percent remaining DOC, indicating that colored DOM is less bioavailable than non-colored material. Concentrations of DOC leached, %BDOC, and SUVA280 varied between species, indicating that the species composition of the marsh likely impacts the quantity and quality of exported DOC. Comparing the UV + microbial to the microbial only incubations did not reveal any clear effects on %BDOC but UV exposure enhanced loss of absorbance during subsequent dark incubation. These results demonstrate the impacts of senescence on the quality and concentration of DOM leached from tidal wetland plants, and that microbes combined with UV impact the degradation of this DOM differently from microbes alone.

Ditching is one of the most widespread forms of anthropogenic impact on tidal marshes but its effects remain poorly understood. Recently, the phenomenon of “waffle” pooling has been documented in ditched marshes, where a repeating pattern of shallow rectangular pools form in the marsh interior. While pools in unditched marsh may eventually revegetate, waffle pools appear to be a more permanent source of vegetation loss. This study assesses the factors influencing the distribution of waffle pools and other marsh pool types from Maine to Virginia using imagery and existing datasets. Waffle pools were most likely to occur where tidal range was less than 0.8 m, but they could also occur anywhere that tidal range was reduced by anthropogenic features. Unlike waffle pools, the presence of isolated and tidally-connected pools throughout the region was not influenced by tidal range, although both of these pool types were more likely to occur in unditched marshes with higher elevations relative to MSL. An analysis of change of New Jersey’s and New York’s marshes since 1970s confirmed that waffle pools are a recent phenomenon and that this process was responsible for 30–100% of all marsh interior vegetation loss in regions of the study area with tidal range below 0.8 m. Overall, interior marsh loss increased as tidal range decreased. Loss of marsh at edges due to erosion increased as the ratio of edge to marsh area increased. We propose that waffle pools are the product of long-term ditching impacts and that comprehensive strategies are needed that restore drainage networks, restore elevation and alleviate tidal restrictions. Since waffle pooled marshes often contain favorable salt marsh mosquito habitat, restoration efforts should integrate ecological approaches with mitigating public health concerns.

The estuarine habitat mosaic supports the reproduction, growth, and survival of resident and migratory fish species by providing a diverse portfolio of unique habitats with varying physical and biological features. Global climate change is expected to result in increasing temperatures, rising sea levels, and changes in riverine hydrology, which will have profound effects on the extent and composition of the estuarine habitat mosaic and its associated nursery quality for juvenile fish. We used a spatially explicit bioenergetics model to assess how different climate change scenarios might affect juvenile salmon growth rate potential relative to present day conditions in the Nisqually River Delta, WA, USA. The model indicated that prey-rich habitats such as emergent salt marshes and eelgrass meadows were most likely to facilitate growth, and that reductions in their areal extent and accessibility could have severe consequences for salmon. For instance, unmitigated sea-level rise halved the predicted extent of low- and high-elevation emergent salt marsh, leading to a 30% reduction in end-of-season weights. Increasing water temperatures compounded these effects during the late spring and summer such that the average daily growth rate of an individual fish decreased by an additional 5–50% when compared to the effects of sea-level rise alone. Lethal temperatures (> 24 °C) were infrequently observed, but they were more likely to occur during summer low tides in the mudflat and eelgrass habitats when accessibility to prey-rich marsh was minimal, thereby limiting foraging capacity and the availability of thermal refugia. Our findings indicate that, barring the enactment of targeted management strategies, rising tidal levels and increasing ocean temperatures may reduce the quality of the estuarine habitat mosaic for out-migrating salmon and other sensitive fish species.

Whole genome duplications (WGDs) lead to polyploid specimens and are regarded as major drivers for speciation and diversification in plants. One prevalent problem when studying WGDs is that effects of polyploidization in ancient polyploids cannot be disentangled from the consequences of selective evolutionary forces. Cytotypic differences in distribution, phenotypic appearance and in response to surface elevation (determined by HOF-modeling) were identified in a relatively young taxa-group of a hexaploid F1-hybrid (Spartina× townsendii H. Groves & J. Groves, Poaceae) and its dodecaploid descendent (Spartina anglica C.E. Hubbard, Poaceae) using vegetation assessments (1029 plots; 1 × 1 m2) from the European Wadden Sea mainland salt marshes, including elevational and mean high tidal (MHT) data. While the F1-hybrid was mainly present in the eastern part of the Wadden Sea, its dodecaploid descendent occurred in the entire Wadden Sea area. The Spartina cytotypes differed in phenotypes (median of Spartina cover: hexaploid = 25% vs. dodecaploid = 12%) and in elevational niche-optimum (hexaploid = − 49.5 cm MHT vs. dodecaploid = 8.0 cm MHT). High ploidy levels correlated with establishment success in Spartina along geographic gradients but did not seem to increase the capacity to cope with abiotic severity downwards the elevational gradient in salt marshes.

The aim of this paper is to deal with syntaxonomical and ecological characteristics of Tamarix smyrnensis communities developed on both salt marsh and riparian habitats of the Yesilirmak Delta Plains. The floristic composition of the communities was analysed by Braun-Blanquet method and the effect of edaphic parameters on the communities were determined using ordination techniques (CCA). The habitat types were identified according to the European Nature Information System (EUNIS) habitat coding list. Junco acuti-Tamaricetum smyrnensis ass. nov. developed on salt marshes and belonging to the alliance of Tamaricion tetragynae, and Tamaricetum tetrandrae-smyrnensis ass. nov. developed on meander banks/river island (eyot) and belonging to the alliance of Rubo sancti—Nerion oleandri distributed under influence of electrical conductivity (EC) of soil. Additionally, it was observed that both associations belonged to subunits of Mediterraneo-Macaronesian tamarisk thickets according to EUNIS.

Nutrient input from estuarine producers underpins coastal fisheries production and knowing which producers are the most responsible for fish diet helps effectively protect and restore coastal ecosystems. Focussing on the Richmond River in Australia as a case study, we sampled the main estuarine producers and estimated their proportional contributions of nutritional input to seven commercially important fisheries species using Bayesian isotope mixing models. We valued the dietary input of estuarine producers to the commercial fisheries by combining dietary contribution estimates with total annual catch data from commercial fishers. A conservative estimate is that estuarine producers in the Richmond River Estuary contribute at least 82 725 kg (78%) of the total annual catch of the seven commercially important fish with an estimated annual value of $AU 450 117. Sea mullet and Mud crab contributed 95% of the total catch, and 93% of the total value assigned to estuarine producers. The two highest valued estuarine producers were tidal marsh (Juncus kraussii) $AU 82 432 and seagrass (Zostera capricorni) $AU 65 423. This study demonstrates the substantial role of estuarine producers to commercial fisheries production and the fisheries economy more broadly. With large areas of estuarine producers under threat globally from land clearing for agriculture, aquaculture and urbanisation, the results presented here provide evidence to support the value of coastal habitats and benefits of their preservation and restoration. GRAPHIC ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13280-021-01600-3.

Salt marshes are vulnerable to climate change-associated sea-level rise and storm-induced surges. Their degradation will likely affect shorebirds relying on this ecosystem. Least Sandpiper (Calidris minutilla) and Pectoral Sandpiper (Calidris melanotos) migrating along coastline habitats typically use salt marshes to rest and replenish their body reserves. Our objective was to test if width of the different vegetation zones within salt marshes affects the occurrence of Least and Pectoral Sandpipers stopping along the St. Lawrence River Estuary, Quebec, Canada, during fall migration. We established 26 survey sites, each 600 m in length, along the shoreline. Shorebird surveys were conducted in 2011 and 2012. We characterized salt marshes by measuring the width of each vegetation zone (lower marsh and upper marsh). We analyzed shorebird presence/not detected data with generalized estimating equations to test the predictions that occurrence of Least Sandpipers and Pectoral Sandpipers increases with width of both the lower and upper marsh. Upper marsh width was positively associated with probability of occurrence in each species. Our results highlight the importance of protecting the integrity of salt marshes for these two species. In the St. Lawrence River Estuary, where landward migration of salt marshes is no longer possible (coastal squeeze), effective management of shorelines is much needed. Otherwise, salt marshes and these two species could be locally jeopardized.

The results of sediment-stratigraphic, diatom and pollen analyses, and AMS 14C dating of salt marsh sediments at Higgin’s Neuk, Airth in the inner Forth estuary in central Scotland are reported. En...

Coastal wetlands reclamation is facing the problem of salinization. Along with the alternation of ecosystem status, studying the following effect on soil properties becomes emergency. Here we reported the pH, salinity and elemental content (mainly metals) variation affected by the vegetation situations, water sources and geographic positions. The results showed that vegetation could lead the pH and salinity of seawater zones closer to that of freshwater zones in both spatial and time scales. Spartina alterniflora (SA) was the most efficient species among the investigated plants, causing decreases of 0.15–0.69 in pH and 2.250–3.821 in salinity. This result might be caused by the absorption of Ca and K from salt marshes by SA and Suaeda salsa (SS), due to the fact that the component content of calcium (all reduced to approximate one-third) and potassium (reduced in some samples) both decreased. Meanwhile, vegetation could improve soil in seawater zones in Fe content with no extra negative influences in elemental analysis. Thus, ecological engineered vegetation indicated great potential in alternating coastal salt marshes to favorable wetlands or farmlands with almost primitive ecosystem. The results might be significant for ecological engineering and agricultural management in future.

Salt marshes form along coastlines and are very interesting ecosystems due to their function and services. In the future, salt marsh plants might provide food and medicine as crops irrigated via seawater in hyper-arid regions. In the Arabian Gulf, little is known about salt marsh vegetation. Therefore, a targeted search on scientific literature was performed to provide a comprehensive assessment. Hence, current knowledge of the extent and status of salt marsh in the Arabian Gulf region was reviewed, based on literature-based analysis. Then, historic trends of salt marsh publications were carefully inspected. This study provides a list of salt marsh families and their genera and species, with a total of 51 family 179 genera 316 species in the Arabian Gulf. The largest family was Chenopodiaceae followed by Poaceae, Asteraceae. Moreover, this study identified some of the gaps that could help future directions for scientific research, and help making decisions of conservation, management policies and procedures.

With climate change and rising sea levels, the coastal zone’s flood risk is deteriorating. Previous researches have shown a gradually degrading capacity of traditional hard engineering structures (e.g., seawall, dikes, etc.) on flood mitigation due to problems such as land subsidence and insufficient maintenance. To remedy the defects, the “building with nature concept” for coastal protection with saltmarshes was examined by combining field measurements and numerical simulations. The advantages of saltmarsh over traditional seawall on flood protection was demonstrated from the perspective of both flood area mitigation and economic gain, based on scenario simulations. Results show that tidal wetlands are essential in mitigating significant wave heights (Hs) and current velocities even during storm conditions. The storm wave and current velocity reduction ratio ( \begin{document}$R{R}_{{\rm{w}}}$\end{document} and \begin{document}$R{R}_{{\rm{c}}}$\end{document} ) by saltmarshes on Chongming Dongtan Shoal (CMDS) during Typhoon 9711 is approximately 11% and 51%, respectively. The wave and current mitigation by Scirpus mariqueter are more efficient than Spartina alterniflora and Phragmites australis during measurements in 2010, which were approximately 0.3 m and 0.2 m/s, 0.125 m and 0.155 m/s, 0.086 m and 0.128 m/s per kilometer width, respectively. The summer saltmarsh area 54.2 km2 on CMDS protects approximately 32 km2 land area behind the seawall from being flooded, equivalent to the seawall heightening of approximately 0.42 m on equivalent flood mitigation. The performance of cost-and-benefit analysis shows a relatively higher (by 3%–7%) net present value (NPV) and a higher (by 1.5 times) benefit-cost ratio (BC) of nature-based solution (i.e., saltmarsh restoration) compared with traditional hard engineering solution (i.e., seawall construction). Thus, building seawall with nature, such as a hybrid flood protection measure, should be implemented in the future coastal redesign and maintenance.

Salt marshes are increasingly valued for their role in coastal defense. In particular, marsh plants slow the progression of waves, thereby decreasing wave heights, orbital velocities and associated energy. Practical application of these effects has driven substantial research estimating the effects of plants on waves. However, the effects of waves on plants remain understudied, especially regarding plant responses along a wave climate gradient. To begin to understand these responses, we collected above- and belowground plant data and wave data from 60 sites across Mobile Bay, USA, and tributaries and evaluated plant responses along the range of assessed wave climate conditions. Plant responses among the dominant species, Juncus roemerianus and Spartina alterniflora, varied along the wave climate gradient. However, the basal diameter of shoots in both species declined linearly with increasing wave climate. While wave climate had no observable effect on other S. alterniflora parameters, the declining diameter of J. roemerianus shoots along the same gradient was commensurate with a decline in the percentage of live canopy shoots aboveground and an increase in root and rhizome biomass in the active rooting zone belowground. In contrast to previous studies, other responses including the height, biomass and density of aboveground shoots in both species were not related to wave climate. More broadly, these results demonstrate that plant features important for wave attenuation such as shoot diameter can change in response to varying wave conditions. These feedbacks should be incorporated to improve coastal modeling and successes of coastal conservation, restoration and enhancement projects.

Identifying migration routes and fall stopover sites of Cinnamon Teal (Spatula cyanoptera septentrionalium) can provide a spatial guide to management and conservation efforts, and address vulnerabilities in wetland networks that support migratory waterbirds. Using high spatiotemporal resolution GPS‐GSM transmitters, we analyzed 61 fall migration tracks across western North America during our three‐year study (2017–2019). We marked Cinnamon Teal primarily during spring/summer in important breeding and molting regions across seven states (California, Oregon, Washington, Idaho, Utah, Colorado, and Nevada). We assessed fall migration routes and timing, detected 186 fall stopover sites, and identified specific North American ecoregions where sites were located. We classified underlying land cover for each stopover site and measured habitat selection for 12 land cover types within each ecoregion. Cinnamon Teal selected a variety of flooded habitats including natural, riparian, tidal, and managed wetlands; wet agriculture (including irrigation ditches, flooded fields, and stock ponds); wastewater sites; and golf and urban ponds. Wet agriculture was the most used habitat type (29.8% of stopover locations), and over 72% of stopover locations were on private land. Relatively scarce habitats such as wastewater ponds, tidal marsh, and golf and urban ponds were highly selected in specific ecoregions. In contrast, dry non‐habitat across all ecoregions, and dry agriculture in the Cold Deserts and Mediterranean California ecoregions, was consistently avoided. Resources used by Cinnamon Teal often reflected wetland availability across the west and emphasize their adaptability to dynamic resource conditions in arid landscapes. Our results provide much needed information on spatial and temporal resource use by Cinnamon Teal during migration and indicate important wetland habitats for migrating waterfowl in the western United States., We analyzed 61 fall migration tracks of fall migrating Cinnamon Teal in western North America. Furthermore, we investigated habitat selection patterns at fall stopover sites. Our results can be used to further inform waterfowl conservation and management efforts in the United States and Mexico.

The San Francisco Bay Area is a leader in environmental stewardship and home to numerous wetland restoration projects including the largest tidal wetland restoration project on the American West Coast. As tidal marsh wetlands are restored throughout the Bay Area many opportunities remain to reaffirm the importance of water management that reduces mosquito production and protects public health. Unlike the early 1900s when long term saltmarsh mosquito control was achieved with large scale surface water management projects, regulatory restrictions produce new hurdles that impact mosquito control and restoration projects alike. Work done in the wetlands surrounding the San Francisco Bay must comply with existing management plans, permit requirements, and government regulations. The same is true for emerging technologies. While unmanned airsystems employed for mosquito control improves efficiency and accuracy, regulations in this arena limit their broad use in wetlands that abut the San Francisco Bay. Mosquito abatement districts collect substantial scientific data that inform land management and mosquito control operations. This information is useful for evaluating wetland restoration progress in the Bay Area and fostering partnerships that keep a public health perspective at the forefront.

Salt marshes are research hotspots of the carbon cycle in coastal zones because large amounts of atmospheric carbon dioxide is fixed by salt marshes vegetation and stored in its biomass and soil. Dissolved organic carbon (DOC) in submarine groundwater (well water and pore water) in salt marshes plays an important role in advective exchange between the salt marshes and coastal waters. However, the molecular characteristics of DOC in salt marsh groundwater are poorly understood because of the complex DOC structures and hydrodynamic process. In this study, fluorescent components and refractory DOC (RDOC) in submarine groundwater from a salt marsh (Chongming Island, China) and adjacent coastal water were characterized by fluorescence spectroscopy and nuclear magnetic resonance spectroscopy. The fluorescent components identified by parallel factor analysis indicated that humic-like substances dominated the chromophoric dissolved organic matter in the submarine groundwater. The chromophoric dissolved organic matter and dissolved organic matter in the submarine groundwater had non-conservative behaviors because of additions from terrestrial humic substances. The nuclear magnetic resonance spectra indicated that bioactive substances (carbohydrates) contributed only 13.2%–14.8% of the dissolved organic matter in the submarine groundwater but carboxyl-rich alicyclic molecules (CRAMs), the main components of RDOC, contributed 64.5% of the dissolved organic matter. Carbohydrates and CRAMs contributed 16.4% and 61.7% of the dissolved organic matter in the coastal water, similar to the contributions for submarine groundwater. The DOC concentration in submarine groundwater was 386±294 µmol/L, which was significantly higher than that in coastal water (91±19 µmol/L). The high DOC concentrations and >60% relative RDOC content suggested that submarine groundwater may be an important source of RDOC to coastal seawater. This information will be helpful for estimating the climate effects of salt marsh blue carbon.

Coastal wetlands are essential for regulating the global carbon budget through soil carbon sequestration and greenhouse gas (GHG – CO2, CH4, and N2O) fluxes. The conversion of coastal wetlands to agricultural land alters these fluxes' magnitude and direction (uptake/release). However, the extent and drivers of change of GHG fluxes are still unknown for many tropical regions. We measured soil GHG fluxes from three natural coastal wetlands – mangroves, salt marsh, and freshwater tidal forests – and two alternative agricultural land uses – sugarcane farming and pastures for cattle grazing (ponded and dry conditions). We assessed variations throughout different climatic conditions (dry–cool, dry–hot, and wet–hot) within 2 years of measurements (2018–2020) in tropical Australia. The wet pasture had by far the highest CH4 emissions with 1231±386 mgm-2d-1, which were 200-fold higher than any other site. Dry pastures and sugarcane were the highest emitters of N2O with 55±9 mgm-2d-1 (wet–hot period) and 11±3 mgm-2d-1 (hot-dry period, coinciding with fertilisation), respectively. Dry pastures were also the highest emitters of CO2 with 20±1 gm-2d-1 (wet–hot period). The three coastal wetlands measured had lower emissions, with salt marsh uptake of -0.55±0.23 and -1.19±0.08 gm-2d-1 of N2O and CO2, respectively, during the dry–hot period. During the sampled period, sugarcane and pastures had higher total cumulative soil GHG emissions (CH4+N2O) of 7142 and 56 124 CO2-eqkgha-1yr-1 compared to coastal wetlands with 144 to 884 CO2-eqkgha-1yr-1 (where CO2-eq is CO2 equivalent). Restoring unproductive sugarcane land or pastures (especially ponded ones) to coastal wetlands could provide significant GHG mitigation.

Climate change plays a large role in driving species range shifts; however, the physical characteristics of an environment can also influence and alter species distributions. In New England salt marshes, the mud fiddler crab Minuca pugnax is expanding its range north of Cape Cod, MA, into the Gulf of Maine (GoM) due to warming waters. The burrowing lifestyle of M. pugnax means sediment compaction in salt marshes may influence the ability of crabs to dig, with more compact soils being resistant to burrowing. Previous studies indicate that salt marshes along the GoM have a higher sediment compaction relative to marshes south of Cape Cod. Physical characteristics of this habitat may be influencing the burrowing performance of M. pugnax and therefore the continuation of their northward range expansion into the GoM. We conducted a controlled laboratory experiment to determine if compaction affects the burrowing activity of M. pugnax in historical and range-expanded populations. We manipulated sediment compaction in standardized lab assays and measured crab burrowing performance with individuals collected from Nantucket (NAN, i.e. historical range) and the Plum Island Estuary (PIE, i.e. expanded range). We determined compaction negatively affected burrowing ability in crabs from both sites; however, crabs from PIE have a higher probability of burrowing in higher sediment compactions than NAN crabs. In addition, PIE crabs were more likely to burrow overall. We conclude that site level differences in compaction are likely altering burrowing behavior in the crab’s expanded-range territory by way of local adaptation or phenotypic plasticity.

Body size is considered an important structuring mechanism of food webs because consumers are usually larger and more mobile than their prey and may couple energy among habitats. We explored the links among trophic position (TP), body size, and the coupling of different energy channels (phytoplankton and C4‐marsh plants) in a saltmarsh landscape in the northern Gulf of Mexico—a dynamic system considered weakly shaped by biotic interactions. Body size was positively associated with TP, and this relationship was stronger in the phytoplankton pathway vs. the C4‐marsh pathway. There was a gradual increase in the coupling of phytoplankton and C4‐marsh plants at larger body sizes and higher TP. Phytoplankton supported longer food chains and larger body sizes than C4‐marsh plants. Results support predictions of the landscape theory for food web architecture and indicate that the role of body size in determining trophic interactions may vary across food web compartments.

Animal groups are known to exhibit collective behaviours that allow for effective responses to predators and environmental factors. Habitats with high levels of structural complexity have been shown to influence the collective tendencies of these animal aggregations. However, the effect of anthropogenically induced habitat complexity on collective tendency is still unknown. We examined the effect of a water control structure (WCS), located in an estuarine salt marsh system, on the collective behaviours of free ranging juvenile Gulf menhaden (Brevoortia patronus), a schooling forage fish. Using an acoustic imaging sonar, behavioural observations prior to and during predator attacks were collected in an open marsh canal as well as in the vicinity of the WCS. We found that fish in schools responded to the WCS by swimming in a less aligned and cohesive manner, while maintaining an increased ability to transfer social information. Our results demonstrate that collective tendency in schooling fish is affected by the presence of anthropogenically introduced habitat complexity, prior to and during predator attack. Our study, thus, strengthens the idea that the complex environmental conditions induced by the presence of man-made structures may play a large role in structuring collective behaviour and trophic interactions in aquatic environments.