Low Salt Marsh Research Articles

Colonization of mudflat substrate by microarthropods: the role of distance, inundation frequency and body size

Salt marshes represent a unique ecosystem at the marine-terrestrial boundary of shallow protected coastlines. Microarthropods form an essential component of soil food webs, but how they colonize new intertidal habitats is little understood. By establishing two experimental systems without animals, we investigated microarthropod colonization (1) at the seashore from the pioneer zone to the lower and upper salt marsh and (2) at the same tidal height on artificial islands 500 m from the seashore. Potential source populations of microarthropods in the respective zones were also investigated. Colonization of microarthropods after 5 years was consistently faster on the seashore than on the artificial islands. Collembola and Mesostigmata colonized all the zones both on the seashore and on the artificial islands, with colonization being faster in the upper salt marsh and in the pioneer zone than in the lower salt marsh. Oribatida colonized the new habitats on the seashore, but only little on the artificial islands. Variations in species composition were more pronounced between salt marsh zones than between experimental systems, indicating that local environmental conditions (i.e., inundation frequency) are more important for the assembly of microarthropod communities than the distance from source populations (i.e., dispersal processes). Variations in community body size of Oribatida and Mesostigmata indicated environmental filtering of traits, with smaller species suffering from frequent inundations. Notably, Mesostigmata most successfully colonized the new habitats across salt marsh zones on both systems. Overall, the results document major mechanisms of colonization of intertidal habitats by microarthropods with different life histories and feeding strategies.

Spatial distribution and characteristics of plastic pollution in the salt marshes of Bahía Blanca Estuary, Argentina

This study delves into the magnitude and attributes of plastic pollution in the salt marshes of the Bahía Blanca Estuary, Argentina, with a specific focus on its spatial distribution. The investigation included the evaluation of microplastics (1–5 mm), mesoplastics (5–25 mm) and macroplastics (25–100 mm), discovering elevated levels along the high salt marsh strandline compared to low salt marsh and mudflat areas. Notably, the abundance of plastic reached staggering levels, reaching up to 20,060 items/m2 in the vicinity of an illegal dumpsite. Microplastics, particularly in the 2–4 mm range, were dominant, and the main plastic components were high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS). Plastic films emerged as the predominant plastic type, while the presence of pellets hinted at potential sources such as illegal dumping and port-related activities.This contamination could be largely attributed to inappropriate waste management practices and urban runoff, which pose a substantial ecological threat to these ecosystems. Urgent remedial action is essential to protect these marshes, underscoring the critical need for comprehensive wetland management and educational initiatives to ensure their long-term sustainability.

Vegetation changes in coastal wetlands of the outer estuary of the Río de la Plata as a result of anthropic-induced hydrological modifications

Samborombón Bay in Argentina is one of the largest coastal wetlands of South America. The Ajó wetlands are located to the south of Samborombón Bay and despite being protected natural areas, the land is privately owned and used for extensive cattle ranching where producers build embankments to reclaim salt marshes land and expand cattle grazing areas. The aim of this study is to identify the occurrence of embankments in the landscape of the Ajó coastal wetlands, to describe their effect on-plant communities' structure (composition and species abundances), and environmental features (soil and water physical and chemical variables). Embankments were mapped using satellite images and aerial photographs. Based on the mapping, 7 sampling areas of marshes with embankments were selected for the study of vegetation, water, and soil. Each sampling area has an embankment that interrupts a tidal channel dividing the marsh into two sectors, one connected to the tidal flow and the other disconnected. Vegetation and soil sampling were performed along a transect covering 3 relative topography levels (High salt marshes, Low salt marshes, and Mudflat-tidal channel) on each side. The results show that embankments and livestock activity modify the plant community structure and environmental features. Disconnected marshes compared to connected ones have a higher abundance of grassland species, freshwater species, salt-tolerant species, and exotic species. Surface water has a greater range of variability in electrical conductivity and the majority ions and soil salinity is higher in disconnected high marshes than in connected ones. In a context of global change, there is uncertainty about the tendency of these observed changes. In this sense, the study carried out based on the monitoring of vegetation, soils, and water is a relevant tool for detecting environmental impacts in wetlands whose hydrology has been anthropically modified.

Spatial and temporal patterns of microphytobenthos communities along the marine-terrestrial boundary in the German Wadden Sea

Microphytobenthos (MPBs) are the main primary producers in shallow marine ecosystems, such as the Wadden Sea. We investigated the spatial and temporal dynamics of MPB communities across the marine-terrestrial boundary over three seasons (spring, summer, and fall) on three East Frisian Islands (Norderney, Spiekeroog, and Wangerooge) in the German Wadden Sea. Natural transects were compared with 12 experimental islands (salt marsh vegetated vs. initially bare islands) established on the tidal flats of Spiekeroog for studying dispersal-mediated community assembly. Sediment cores were taken along triplicate transects and on three elevation levels of the experimental islands, corresponding to the pioneer (pio) zone, the lower salt (LS) marsh, and the upper salt (US) marsh. On both the natural transects and the experimental islands, the highest MPB biomass was observed in the pio zone, where vegetation-driven sediment stabilization and high-mud content could have promoted MPB biomass in this marine-terrestrial transition zone. On the experimental islands, MPB biomass and diversity significantly decreased with elevation regardless of the season, indicating that the rarely submerged upper salt marsh level supported minimal MPB growth. The MPB biomass was also higher on initially vegetated than on bare islands, which was the most pronounced on the US level. On the tidal flat transects, the MPB biomass significantly increased with elevation up to the pio zone before decreasing again in the LS marsh. Temperature, sediment water content, and grain size significantly affected transect MPB biomass. MPB diversity, on the other hand, was not related to elevation but was rather determined by temperature, mean grain size, and mud content. Our study suggests that extending MPB studies into the “terrestrial” domain of salt marshes enhances our understanding of the microalgae–plant interaction in this important boundary zone.

Trophic structure and origin of resources of soil macrofauna in the salt marsh of the Wadden Sea: a stable isotope (15N, 13C) study

Salt marshes exist along the gradient of the marine mudflat to the terrestrial dunes, with a gradient of shore height and associated plant zonation. The lower salt marsh (LSM) extends from the mean high tidal level to 35 cm above that level and is followed by the upper salt marsh (USM). Despite changes in the amount of allochthonous marine input and in abiotic conditions, little is known about changes in the trophic structure and used of basal resources by the soil macrofauna along marine—terrestrial boundaries. Natural variations in carbon stable isotope ratios (δ13C signatures) allow insight into basal resources of consumers such as marine algae, terrestrial C3 and C4 photosynthesising plants. Furthermore, variations in nitrogen stable isotope ratios (δ15N signatures) allow insight into the trophic position of consumers. We investigated spatial and temporal changes in stable isotope signatures in salt marsh soil macrofauna of the island of Spiekeroog, German Wadden Sea. The range of δ15N signatures indicated no changes in food chain length across salt marsh zones with consumers in both zones comprising primary decomposers, secondary decomposers and first order predators. However, the trophic position of individual species changed between zones, but in particular with season. Contrasting δ15N signatures, the range in δ13C signatures in the LSM was twice that in the USM indicating a wider range of resources consumed. Bayesian mixing models indicated predominant autochthonous resource use in both the LSM and USM, with the use of marine allochthonous resources never exceeding 29.6%. However, the models also indicate an increase in the use of marine resources in certain species in the LSM with no use in the USM. Overall, the results indicate that the resource use of salt marsh macrofauna varies more in space than in time, with the food web being generally based on autochthonous rather than allochthonous resources. However, there also is trophic plasticity in certain species across both temporal and spatial scales including variations in the use of allochthonous resources. Generally, however, marine input contributes little to the nutrition of salt marsh soil macroinvertebrates.

Can Coastal Habitats Rise to the Challenge? Resilience of Estuarine Habitats, Carbon Accumulation, and Economic Value to Sea-Level Rise in a Puget Sound Estuary

Sea-level rise (SLR) and obstructions to sediment delivery pose challenges to the persistence of estuarine habitats and the ecosystem services they provide. Restoration actions and sediment management strategies may help mitigate such challenges by encouraging the vertical accretion of sediment in and horizontal migration of tidal forests and marshes. We used a process-based soil accretion model (Coastal Wetland Equilibrium Model) combined with a habitat classification model (MOSAICS) to estimate the effects of SLR, suspended sediment, and inland habitat migration on estuarine habitats, soil carbon accumulation, and economic value of climate change mitigation of carbon accumulation (social cost of carbon dioxide) in a macrotidal estuary in the northwest USA over 100 years (2011 to 2110). Under present-day sediment levels, we projected that after 100 years, most high salt marsh would remain with < 100 cm SLR, but substantial area converted to transitional (low) salt marsh and mudflat with ≥ 100 cm SLR. Increasing sediment availability increased the projected resilience of transitional salt marsh to SLR but did not prevent declines in high marsh area. Projected total carbon accumulation plateaued or declined with ≥ 100 cm SLR, yet the economic value of carbon accumulation continued to rise over time, suggesting that the value of this ecosystem service was resilient to SLR. Doubling or tripling sediment availability increased projected carbon accumulation up to 7.69 and 14.2 kg m−2 and increased total economic value up to $373,000 and $710,000, respectively. Allowing marsh migration supported conversion of upland to freshwater marsh, with slight increases in carbon accumulation. These results inform climate adaptation planning for wetland managers seeking to understand the resilience of estuarine habitats and ecosystem services to SLR under multiple management strategies.

Spatial and temporal variations in salt marsh microorganisms of the Wadden Sea.

Salt marshes exist at the interface of the marine and the terrestrial system. Shore height differences and associated variations in inundation frequency result in altered abiotic conditions, plant communities, and resource input into the belowground system. These factors result in three unique zones, the upper salt marsh (USM), the lower salt marsh (LSM), and the pioneer zone (PZ). Marine detritus, such as micro‐ and macroalgae, is typically flushed into the PZ daily, with storm surges moving both salt marsh detritus and marine detritus into higher salt marsh zones. Microbial assemblages are essential for the decomposition of organic matter and have been shown to sensitively respond to changes in abiotic conditions such as oxygen supply and salinity. However, temporal and spatial dynamics of microbial communities of Wadden Sea salt marshes received little attention. We investigated the dynamics of soil microbial communities across horizontal (USM, LSM, and PZ), vertical (0–5 and 5–10‐cm sediment depth), and temporal (spring, summer, and autumn) scales in the Wadden Sea salt marsh of the European North Atlantic coast using phospholipid fatty acid (PLFA) analysis. Our results show strong spatial dynamics both among salt marsh zones and between sediment depths, but temporal dynamics to be only minor. Despite varying in space and time, PLFA markers indicated that bacteria generally were the dominant microbial group across salt marsh zones and seasons, however, their dominance was most pronounced in the USM, whereas fungal biomass peaked in the LSM and algal biomass in the PZ. Only algal markers and the stress marker monounsaturated to saturated fatty acid ratio responded to seasonality. Overall, therefore, the results indicate remarkable temporal stability of salt marsh microbial communities despite strong variability in abiotic factors.

A multiproxy study of intertidal surface sediments from two macrotidal estuarine systems (Canche, Authie) in northern France: Insights into environmental processes

Estuaries are considered one of the most dynamic ecosystems in the world, ensuring high production and transfer of large quantities of organic matter (OM) from continents to the ocean. Despite the large influence of estuaries in the functioning of coastal ecosystems, our understanding of OM dynamics in these buffering coastal environments remains fragmented. In this frame, our study was carried out to describe and understand the main drivers of OM distribution in two estuaries (Canche, Authie) of the eastern English Channel, based on descriptive and quantitative approaches. For this purpose, in February and March 2018, surface sediments were sampled at low tide along cross-shore transects in the intertidal zone of each estuary. Analysis of sediment grain size, porosity, proportion of aggregated particles, total carbonate content and organic geochemical characteristics (total OM content, atomic TOC/TN ratio, δ13C value) of surface sediments allowed identifying four biosedimentary facies: sand flat, mud flat, low and high salt marshes. In parallel, the elemental and isotopic characterization of the suspended particulate OM inputs by the rivers, the surface biofilms and the halophytic vegetation was performed to trace the three major sources contributing to sedimentary OM in both estuaries. Spatial distribution of OM in surface sediments (ranging between 0.6 and 26.9% dry weight) evidenced higher contents along marsh platforms than in sand and mud flats. and the OM pool was mainly constituted of a mixing of C3 terrestrial vascular plants, marine and riverine phytoplankton. The comparison between both estuaries highlighted that the geomorphology impacted by natural and anthropic factors plays a preponderant role in the distribution and the sources of sedimentary OM by influencing vegetation communities and hydrodynamic processes. In the context of sea level rise, an improved understanding of the OM dynamics within each biosedimentary facies is crucial to better constrain and assess the role of macrotidal estuaries in carbon cycle.

High Productivity Makes Mangroves Potentially Important Players in the Tropical Silicon Cycle

Over the last two decades, recognition of the important role terrestrial plants play in regulating silicon (Si) cycling has emerged. Si improves plant fitness by protecting them from abiotic (e.g., desiccation) and biotic (e.g., fungal attack) stressors. Once incorporated into plant biomass this biogenic Si is more bio-available than the lithogenic material from which it was ultimately derived. Thus plants play a key function in regulating the amount and timing of Si availability in downstream ecosystems. Recent work has highlighted the importance of salt marshes in the temperate Si cycle. However, the role of their tropical counterparts, mangroves, has largely gone unexplored. Here we report foliar concentrations of plant Si (as %Si by dry weight) for four Caribbean mangrove species: Conocarpus erectus (buttonwood), Laguncularia racemosa (white mangrove), Avicennia germinans (black mangrove), and Rhizophora mangle (red mangrove). Overall, the median Si concentration was low (0.07%) and did not vary among plant part (e.g., foliage, twig, and propagule). There was also little variation in Si among species. Using literature values of aboveground net primary production, and the concentrations reported here, we estimate an aboveground mangrove Si uptake rate of 2–10 kg Si ha–1 year–1. These rates are on par with rates reported for temperate and boreal forests as well as low nutrient salt marshes, but lower than estimates for high nutrient salt marshes. Thus, despite the low Si concentrations observed in mangroves, their high productivity appears to make them a hot spot of Si cycling in tropical coastal systems.

High-Resolution Monitoring of Tidal Systems Using UAV: A Case Study on Poplar Island, MD (USA)

Tidal processes regulating sediment accretion rates and vegetated platform erosion in tidal systems strongly affect salt marsh evolution. A balance between erosion and deposition in a restored salt marsh is crucial for analyzing restoration strategies to be adopted within a natural context. Marsh morphology is also coupled with tidal mudflats and channel networks and this makes micro-tidal systems crucial for a detailed assessment of restoration interventions. Here, we present a methodological approach for monitoring channel morphodynamics and vegetation variations over a time frame of six years in a low tidal energy salt marsh of the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island (Maryland, USA). The project is a restoration site where sediment dredged from the shipping channels in the upper Chesapeake Bay is used to restore a tidal marsh habitat in mid-Chesapeake Bay. Aerial surveys with an Unmanned Aerial Vehicle (UAV) have been performed for the high-resolution mapping of a small tidal system. Flight missions were planned to obtain a Ground Sample Distance (GSD) of 2 cm. Structure-from-Motion (SfM) and Multi-View-Stereo (MVS) algorithms have been used to reconstruct the 3D geometry of the site. The mapping of channel morphology and an elevation assessment on the mudflat were performed using orthomosaics, Digital Terrain Models (DTMs) and GNSS survey. The results highlight that the workflow adopted in this pilot work is suitable to assess the geomorphological evolution over time in a micro-tidal system. However, issues were encountered for salt marsh due to the presence of dense vegetation. The UAV-based photogrammetry approach with GNSS RTK ground surveys can hence be replicated in similar sites all over the world to evaluate restoration interventions and to develop new strategies for a better management of existing shorelines.

Environmental changes related to the Holocene sea-level transgression and successive highstand (7–5.5 Kyr) at the NE coastal plain of Buenos Aires (Argentina)

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 Bahía Samborombón (∼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.

Salt marsh palynological assemblages as modern analogue tools for interpreting past vegetation zones and environmental conditions in the NE coastal plain of Argentina

In this study we examine the distribution patterns of modern palynological assemblages from different salt marsh zones and microenvironments in order to generate reference data for the north-central sector of Bahía Samborombón, to be used as analogues for interpreting fossil palynological assemblages. For the modern palynological analysis, 23 surface sediment samples were taken from different tidal environments in the coastal zone, including intertidal, low, middle and high salt marsh. The results allowed to differentiate and characterize the tidal environments from the palynological point of view. Small changes in the microrelief such as tidal channels, cheniers, and depressions areas, modify the local vegetation and therefore determine the final palynological assemblage. Fossil data from the central zone of Bahía Samborombón (PM 1 stratigraphic sequence) was compared with the modern pollen data to interpret vegetation and paleoenvironmental changes; which demonstrated that salinity, mainly related to the tidal influence, drove the paleoenvironmental changes. This study provides new modern palynological data for Bahía Samborombón and may constitute an important tool to interpret Holocene fossil sediment sequences. This data could be used in future paleoenvironmental reconstructions in coastal plain deposits whose evolution are linked to relative sea-level fluctuations.

Saltmarsh sustainability throughout the Holocene in Boston Harbor: A new sea-level curve for the lower Gulf of Maine and implications of recent anthropogenic alteration

Saltmarsh evolution is closely linked to sea-level rise (SLR) and sediment supply. In a regime of accelerating SLR, saltmarsh survival depends on the ability of the marsh platform to grow vertically through organic and inorganic accumulation, and laterally via transgression over adjacent uplands. In formerly glaciated settings, the formation and maintenance of a saltmarsh are complicated by steep uplands, low sediment availability, isostatic rebound, changes to tidal amplitudes, and anthropogenic alteration. While much work has examined the development of large saltmarshes in New England since the mid-Holocene and Anthropocene, little is known about the smaller isolated saltmarshes that form in pockets along the glaciated coastline. We use radiocarbon dates from newly uncovered index points (basal peat) within Boston Harbor to date one of the oldest saltmarshes in the region (∼4.2 ka), and calculate the polynomial relative sea-level curve (RSLR) for the lower Gulf of Maine taking into account tidal amplification throughout the Holocene. This study informs the historical persistence of isolated saltmarshes under varying rates of sea-level rise (magnitude as much as 2 mm yr−1). Additionally, we refine the timing and rates of the mid-Holocene sea-level deceleration in this region: between 2.8 and 3.3 ka, slowing from 2.1 mm yr−1 to 0.5 mm yr−1. RSLR determined from the past century of tide gauge data is 2.86 mm yr−1, five times greater than historic rates over the past 2000 years. Recent vertical accretion rates (determined from marker horizons and 210Pb data) indicate that portions of Boston Harbor’s saltmarshes are able to keep pace with current RSLR. However, historical diking and ditching practices appear to have resulted in elevation loss and conversion from high saltmarsh platforms to low saltmarsh platforms, largely influencing the amount of inorganic sediment needed to help maintain marsh surfaces. These results highlight that knowledge of historical anthropogenic modifications and changes in hydroperiod are critical when interpreting vertical accretion results. More importantly, anthropogenic modification within sediment starved saltmarshes may be the cause for cannibalization of marsh shorelines, whereby inorganic sediment eroded from marsh edges is recycled and delivered to the surface, facilitating vertical accretion that offsets RSLR. Under modern accelerated sea-level rise and decreased sediment supply, this cannibalization process may now be the only pathway for saltmarsh survival.

Long-Term Effects of Sheep Grazing in Various Densities on Marsh Properties and Vegetation Dynamics in Two Different Salt-Marsh Zones

For conservation management of grassland ecosystems, an important question is under which conditions large grazers induce compositional and structural variation in plant communities, which is a prerequisite for high biodiversity. Here we used two long-term projects on the mainland salt marshes of the Wadden Sea to test the hypothesis that long-term grazing management with different stocking densities results in plant communities with distinctively different plant species composition and vegetation structure. The two projects took place on a low clayey and a high sandy salt marsh with different stocking densities of sheep: 0, 1.5, 3.5, 4.5 and the initially 10 sheep ha−1, where measurements were collected 11, 15, 19 and 23 years after the start of the project. Moreover, grazers affect abiotic conditions by reducing soil-redox potential and surface elevation, thereby driving composition and structure of salt-marsh vegetation. On the low salt marsh, a continued high stocking density (10 sheep ha−1) resulted in succession from the early-successional Puccinellia maritima community to the late-successional Atriplex portulacoides community. On the high salt marsh, the early-successional Festuca rubra community was maintained under all stocking densities. Cessation of grazing resulted in succession to the Elytrigia atherica community in both salt-marsh types. Intermediate stocking densities (1.5, 3 or 4.5 sheep ha−1) resulted in a mosaic of tall vegetation and patches of lawn, i.e. short-grazed vegetation, where Puccinellia maritima lawn occurred interspersed with patches of the Festuca rubra and tall Elytrigia atherica communities in both salt-marsh types. Effects of grazers were influenced by the presence of watering points near the sea wall. To conclude, our results show how joint interactions between grazers and abiotic conditions drive vegetation diversity and heterogeneity, with implications for ecosystem functions and services such as wildlife biodiversity and coastal protection.

Impact of sea level change on coastal soil organic matter, priming effects and prokaryotic community assembly.

Salt marshes are coastal areas storing high amounts of soil organic matter (SOM) while simultaneously being prone to tidal changes. Here, SOM-decomposition and accompanied priming effects (PE), which describe interactions between labile and old SOM, were studied under controlled flooding conditions. Soil samples from two Wadden Sea salt marsh zones, pioneer (Pio), flooded two times/day, and lower salt marsh (Low), flooded ∼eight times/month, were measured for 56 days concerning CO2-efflux and prokaryotic community shifts during three different inundation-treatments: total-drained (Drained), all-time-flooded (Waterlogged) or temporal-flooding (Tidal). Priming was induced by 14C-glucose addition. CO2-efflux from soil followed Low>Pio and Tidal>Drained>Waterlogged, likely due to O2-depletion and moisture maintenance, two key factors governed by tidal inundation with regard to SOM mineralisation. PEs in both zones were positive (Drained) or absent (Waterlogged, Tidal), presumably as a result of prokaryotes switching from production of extracellular enzymes to direct incorporation of labile C. A doubled amount of prokaryotic biomass in Low compared to Pio probably induced higher chances of cometabolic effects and higher PE. 16S-rRNA-gene-amplicon-based analysis revealed differences in bacterial and archaeal community composition between both zones, revealing temporal niche adaptation with flooding treatment. Strongest alterations were found in Drained, likely due to inundation-mediated changes in C-binding capacities.

Seasonal dynamics and changing sea level as determinants of the community and trophic structure of oribatid mites in a salt marsh of the Wadden Sea.

Global change processes affect seasonal dynamics of salt marshes and thereby their plant and animal communities. However, these changes have been little investigated for microarthropod communities. We studied the effect of seasonality and changes in sea level on oribatid mites in the natural salt marsh and on artificial islands in the back-barrier environment of the island Spiekeroog (Wadden Sea, Germany). Three zones of the artificial islands were filled with transplanted sods from the lower salt marsh zone and thereby exposed to three different inundation frequencies. We hypothesized that oribatid mite communities will differ along the natural salt marsh vegetation zones [upper salt marsh (USM), lower salt marsh (LSM), pioneer zone (PZ)], which are influenced by different tidal regimes. Accordingly, total oribatid mite densities declined from the USM and LSM to the PZ. Similarly, oribatid mite species compositions changed along the salt marsh transect and also responded to variations in inundation frequency in LSM on artificial islands with typical species of the USM, LSM and PZ being Multioppia neglecta (USM), Hermannia pulchella (LSM), Zachvatkinibates quadrivertex (LSM, PZ) and Ameronothrus schneideri (LSM, PZ). Oribatid mite density in the salt marsh and on the artificial islands was at a maximum in winter and spring; this was due in part to high density of juveniles, pointing to two reproductive periods. We hypothesized that oribatid mite trophic structure changes due to variations in abiotic (e.g., tidal dynamics, temperature) and biotic conditions (e.g., resource availability). Stable isotope (15N, 13C) and neutral lipid fatty acid analyses indicated that oribatid mite species have different diets with e.g., Z. quadrivertex feeding on macroalgae and fungi, A. schneideri feeding on microalgae and bacteria, and Scheloribates laevigatus and M. neglecta feeding on dead organic matter, bacteria and fungi. Overall, the results indicate that oribatid mite species in salt marshes are affected by changes in environmental factors such as inundation intensity, with the effects being most pronounced in species with narrow trophic niches and limited niche plasticity. The results also indicate that oribatid mite communities of the LSM respond little to short-term (one year) changes in inundation frequency.

Past environmental changes during the Late Holocene sea-level fall (last 2.7 Ka) at Bahía Samborombón, NE coastal plain (Argentina)

Here we present a reconstruction of vegetation history and environmental changes at the central zone of Bahía Samborombón during the Late Holocene sea-level regressive phase (last 2.7 Ka) corresponding to MIS 1. This study is an integrative approach based on the combination of geomorphological and micropaleontological (pollen, non-pollen palynomorphs and foraminifera) proxy data. We found agreement among the environmental inferences from each proxy, which clearly show the evolution of the estuarine saltmarsh from an intertidal environment under significant marine influence towards a supratidal brackish-freshwater environment as sea-level was falling. The evidence of this evolution is (1) coastal progradation encompassing at least 5.7 km as revealed by relict shorelines. Saltmarsh elevation is another evidenced as a result of accretion due to fine sediments accumulation of at least 1.2 m thick. We posit based on these values, significant progradation and accumulation processes. (2) Plant succession, characterized by the replacement of low saltmarsh vegetation by that typical of high saltmarsh; which then is associated to brackish-freshwaters plant communities in shallow water-bodies environments. (3) A gradual decrease of dinocysts and foraminifera assemblages, the latter absent during the last millennium indicating a decrease in marine influence and the consequent lower salinity values. Bahía Samborombón coastal plains became a regional scale character during the last 2.7 Ka due to its surface increase, turning into one of the most extensive southeastern-South America saltmarshes, currently constituting a biosphere reserve.

Benthic foraminifera in transitional environments in the English Channel and the southern North Sea: A proxy for regional-scale environmental and paleo-environmental characterisations

On the basis of the available databases including 700 sampling stations from subtidal to salt marsh areas, the purpose of this paper is to synthesise the regional distribution of living benthic foraminifera in transitional environments along the English Channel and southern North Sea. Indicator species analyses assign 37 foraminiferal taxa to high salt marsh, middle salt marsh, low salt marsh, tidal flat, tidal channel, and subtidal environmental units. Species are indicator of a single unit (e.g., Elphidium gunteri for tidal flat) up to four units (e.g., Haynesina germanica from tidal flat to middle marsh). The outcomes of the present study enhance future high-resolution paleo-environmental interpretations based on benthic foraminifera in transitional environments.

Impacts of Fertilization and Tidal Inundation on Elevation Change in Microtidal, Low Relief Salt Marshes

We evaluated the importance of both tidal inundation and nutrient fertilization as drivers of elevation change in coastal salt marshes. The three sites investigated occurred along a 9-km stretch of the Atlantic Intracoastal Water Way in Central North Carolina. Despite their close geographic proximity, the sites varied in tidal range, elevation within the tidal frame, and stem height and stem density of Spartina alterniflora. Total standing aboveground biomass and marsh surface elevation change (measured by surface elevation tables; SETs) were documented during a 3-year period of nutrient fertilization and for two additional years after fertilization ceased. Measured elevation change rates in control plots varied from 0.2 to 1.2 cm year−1 and were negatively correlated with starting elevation (r 2 = 0.82, p < 0.05). Fertilization resulted in increases in both standing aboveground biomass and marsh surface elevation change. Fertilized sites gained 0.69 to 2.1 cm year−1 during the 3-year application period and 0.02 to 0.97 cm year−1 during the post application period. The magnitude of the fertilization-induced elevation response was mediated by position in the tidal frame with sites that were lower gaining less elevation relative to controls than sites that were higher. The data presented here suggest that nutrient fertilization may be an effective adaptive management strategy for helping minerogenic marshes keep pace with sea level, but that the impact of fertilization may depend on tidal inundation.

Assessment of Hurricane Sandy damage and resulting loss in ecosystem services in a coastal-urban setting

We quantified the location and extent of damage from Hurricane Sandy in habitats within the complex coastal-urban region of Jamaica Bay, New York and calculated the values of ecosystem services (ESV) lost. Results were compared with those from Hurricane Katrina. We found that moderate flooding and sand deposition were the most prevalent types of damage, and they caused the most degradation to low salt marsh habitat. Compared with Hurricane Katrina, damage from Hurricane Sandy to built and natural capital was generally lower for almost all categories except beach erosion. This was especially damaging due to the high levels of disturbance prevention ecosystem services beaches and dunes provide. Our impact index revealed that the majority of damage was minimal in severity (60%) and would likely be reversed within five years (62%), with a total possible loss of up to US$ 6.5 million for Jamaica Bay, NY. We demonstrated the use of our results to identify vulnerable areas for protection and restoration, and to calculate gains in ESVs in each scenario. By quantifying the location, extent and type of damage from Hurricane Sandy and the ESVs lost, we can provide another dimension to protection and restoration efforts in this sensitive coastal-urban region.