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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 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.

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.

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 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 dynamic ecosystems that change in response to local geographic and geologic factors as well as sea level changes. Most east coast salt marshes are the result of rising sea levels since the end of the last ice age, about 20,000 ybp. To compound this natural process, anthropogenic manipulations for farming, development and other purposes have occurred for centuries. Alterations to salt marshes for the purpose of controlling larval mosquitoes at their source, at least along the east coast of the United States, have occurred since the early twentieth century. These alterations have included large-scale manipulations such as extensive parallel grid-ditching and impounding. Within the last 50 years, more selective source reduction methods such as Open Marsh Water Management (OMWM) have been employed with fewer deleterious impacts to marsh resources. Even more recently, the more holistic approach of Integrated Marsh Management (IMM) has been used with considerable success particularly in the northeastern and Mid-Atlantic states. IMM not only uses OMWM techniques but incorporates the judicious use of mosquito control pesticides, tidal flow restoration, impoundment management, wildlife habitat enhancement, invasive plant control, and selective shallow ditching (“runneling”) depending on local conditions and management plans. As many marshes are becoming wetter and either drowning or migrating inland (where possible) due to the effects of increasing rates of sea level rise, the compounding long-term impacts of parallel grid-ditching and past manipulations on marsh surface elevation and hydrology are being more intently studied. These changes in saltmarsh dynamics have had and will continue to have impacts on where saltmarsh mosquitoes are produced, which could have corollary effects on public health and quality of life near coastal communities. As salt marshes continue to change, mosquito control agencies can play a significant role in providing input for salt marsh restoration and management in addition to their primary objective of vector control and enhancing quality of life.

Accurately mapping, modeling, and managing the diversity of wetlands present in estuaries often relies on habitat classification systems that consistently identify differences in biotic structure or other ecosystem characteristics between classes. We used field data from four Oregon estuaries to test for differences in vegetation structure and edaphic characteristics among three tidal emergent marsh classes derived from National Wetlands Inventory (NWI) data: low estuarine marsh, high estuarine marsh, and tidal palustrine marsh. Independently of NWI class, we also evaluated the number and types of plant assemblages present and how edaphic variables, non-native plant cover, and plant species richness varied among them. Pore water salinity varied most strongly across marsh classes, with sediment carbon and nitrogen content, grain size and marsh surface elevation showing smaller differences. Cover of common vascular plant species differed between marsh classes and overall vegetation composition was somewhat distinct among marsh types. High estuarine marsh had the largest species pools. However, plot-level plant diversity was similar among marsh classes. Non-native species cover was highest in tidal palustrine and high estuarine marshes. The marshes in the study contained a large number of plant assemblages with most occurring across more than one marsh class. The more common assemblages occurred along a continuum of tidal elevation, soil salinity, and edaphic characteristics, with varying plant richness and non-native cover. Our data suggest that NWI classes are useful for differentiating several general features of Oregon tidal marsh structure, but that more detailed information on plant assemblages found within those wetland classes would allow more precise characterization of additional wetland features such as edaphic conditions and plant diversity.

The paper outlines the evolution of an Australian form of Open Marsh Water Management (OMWM) called runnelling which was implemented in relatively pristine saltmarshes. Runnelling involves shallow channels and was distinguished from OMWM which involves ditching. Both methods aim to conserve tidal hydrology. The core research covers 28 years of research on the original experimental site (Coomera Island, Queensland), in routine monitoring and impact assessments that were made periodically. It also introduces and incorporates information from associated research. This includes effects of runnelling on non-target aspects—snails and crabs. Emerging issues during the course of the longer-term research included the risk of mobilising acid sulfates and of mangrove encroachment into the saltmarsh. As well, use of the data was extended to retrofit it to address broader questions about saltmarsh processes and how to identify them. That identified progressive changes at the Coomera site, and so a further query was whether the system showed signs of approaching a tipping point. In summary, there were some identifiable effects of runnelling in all parts of the research. These were mostly related to the increased wetness near runnels, as flooding by tides would occur at tides up to 0.30 m lower than the pre-runnelling situation. The increased wetness was related to plants, snails and crabs. From a mosquito management perspective the method was successful. From an environmental perspective the environmental changes were only very close to runnels (within 10 m). The overall changes at the experimental site were consistent with other changes in eastern Australia, especially of mangrove encroachment into saltmarshes. Once the runnelling method appeared to manage mosquitoes without damaging wetland values it was adopted widely throughout south east Queensland, encouraged by the positive attitude of permitting agencies, but longer-term evaluation was hindered by lack of relevant records.

Pollen assemblages closely reflect the local vegetation that characterizes the salinity status, providing useful analogs for paleoecologxical reconstruction in regional deposits. Palynological evidences of surface sediments from the Coringa mangrove wetland were correlated with the physicochemical and sediment salinity records to observe the relationship between them. The statistical analysis of the data obtained here revealed a marked horizontal salinity gradient from north to south.. In this study, ordination (detrended correspondence analysis) of palynomorph groups has identified a salinity gradient of 1.1 to 3.0 PSU from the north to the south in the wetland. High palynomorph deposition and lower salinity are observed along channel margins due to the mixing of estuarine water during the rainy season. The mudflats along the transects show a lower diversity of plants in the pollen record and high total dissolved solids (TDS) than commonly found in the coastal wetlands. The presence of scrubby halophytic vegetation in the upper saltmarsh and oligohaline-freshwater vegetation in the low tidal saline marshes is a zonation pattern related to the localized influence of freshwater conditions. Palynomarine Index (PMI) reveals the highest freshwater/tidal inundation along Ramannapalem due to the presence of numerous riverine channels while the remaining part of the wetland has restricted tidal inundation leading to the conversion of mangrove forests to salt pans and paddy fields. Thus, the health and productivity of the mangrove ecosystem are also governed by hydrodynamics, catchment land use, water discharge in the channels, and tidal flushing.

Development of coastal New England has led to the replacement of up to 37% of salt marshes with degraded freshwater wetlands, primarily through tidal restrictions. Removing these restrictions to restore salt marsh ecology would improve water quality, increase flood and storm protection, nutrient filtration, erosion control, and carbon sequestration. However, such restorations replace functional freshwater wetlands and could potentially impact freshwater species. Freshwater-dependent wildlife species such as the spotted turtle (Clemmys guttata), may be especially vulnerable to rapid changes in habitat resulting from tidal reintroduction due to their high site fidelity and limited ability to disperse quickly. Conservation of genetically and physically isolated spotted turtle populations as well as the restoration of salt marshes to mitigate climate change impacts are both high priorities on Nantucket Island. These two priorities conflicted in a project to restore tidal hydrology to an impounded freshwater marsh known to host a robust spotted turtle population. We evaluated changes to spotted turtle home range size and location and habitat use in response to salt marsh restoration over eight years. Home range size did not change but the location of home ranges shifted into bordering wetlands landward of the tidal salt water influence. Spotted turtles selected remaining freshwater marshes and shrub swamps while avoiding developed land and areas of establishing salt marsh within areas that had previously been high quality habitat. This study suggests prioritizing conservation of wetlands adjacent to planned salt marsh restoration to provide habitat for freshwater species to migrate.

Herbivore-plant interactions have been shown to play central roles in determining the structure of salt marsh communities. However, relatively little is known about how marsh herbivory varies over small spatial scales (e.g.

Dating saltmarshes is a fundamental step to conserve them suitably, because the oldest saltmarshes are becoming increasingly rare and host a particular biodiversity. In a French Atlantic saltmarsh, we counted tree rings on Suaeda vera, a ligneous plant of the European saltmarshes. We considered that the age of the stem may give the minimal age of the saltmarsh on which it grows as this is a specialist species of this habitat. By combining the dating of the saltmarsh using this proxy with a classical dating based on a photo-interpretation method, we found that the count of tree rings on S. vera gives an accurate dating of the minimal age of a saltmarsh patch. However, because of the rather low longevity of this species (maximum of 27 years in the investigated area), old maps and aerial photographs still remain essential to date the oldest saltmarsh patches. We further discuss: (1) the potential use of cross-dating on dead stems of the plant to reconstruct the long-history of saltmarshes; (2) the potential link between the growth velocity of S. vera and the spatial dynamics of saltmarshes.

Salt marshes are at risk globally if they cannot keep pace with sea level rise. Along the United States Mid-Atlantic coast, high marsh has already declined, and is particularly vulnerable to future loss due to greater regional rates of relative sea level rise and limited capacity for both vertical accretion and landward migration. To support climate adaptation efforts in the region, we conducted a spatial overlay analysis to (1) assess interior ponding in the high tidal marsh zone caused by waterlogging, and (2) identify restoration opportunities where poor drainage is limiting natural recovery. Surface inundation has increased across over 14,000 ha of high marsh in the region, mostly along the eastern Chesapeake Bay and New Jersey coast. Within this waterlogged area, we identified 239 potential restoration sites (275 ha). Validation data indicate our analysis had relatively high accuracy in identifying potential restoration sites, with a true positive rate of 76% and a true negative rate of 96%. Widespread waterlogging emphasizes the need for climate adaptation efforts to restore and protect high marsh in the face of future change. Our recommended restoration strategy of connecting waterlogged sites to tidal creeks aligns with best practices by enabling drainage of high marsh to halt or even reverse ponding, improve recovery from future flooding events, and ultimately facilitate marsh migration with sea level rise.

Worldwide, human activities have modified hydrology and nutrient loading regimes in coastal wetlands. Understanding the interplay between these drivers and subsequent response of wetland plant communities is essential to informing wetland management and restoration efforts. Recent restoration strategies in Louisiana proposes to use sediment diversions from the Mississippi River to build land in adjacent wetlands and reduce the rate of land to open water conversion. In conjunction with sediment delivery, diversions can increase nutrient loads and water levels in the receiving basins. We conducted a greenhouse mesocosm experiment in which we exposed three common tidal freshwater and brackish marsh plants (Panicum hemitomon, Sagittaria lancifolia, and Spartina patens) to two nitrate loading rates [high (35 g N m2 year−1) and low (0.25 g N m2 year−1)], and two flooding treatments (with and without diversion pulsing). Experimental units were set at two different elevations within the treatment tanks to simulate both a healthy and degraded marsh. Plant growth metrics and soil physicochemical properties were measured monthly. Final total biomass was determined at the study’s conclusion. Growth responses differed between species but were not significantly influenced by the treatments. Soil redox potential decreased significantly following the increase in flooding associated with the diversion pulse, but recovered to pre-diversion levels after a 3-month recovery period. Our study suggests short flooding pulses with a recovery period may be key for maintaining healthy marshes, however there remains a need for longer-term empirical studies to understand marsh response to pressures associated with river sediment diversions over time.

Coastal wetlands are projected to experience increases in anthropogenic and climatic disturbances, which may alter plant-sediment feedbacks critical for maintaining marsh resilience to sea level. To study the effects of disturbance on ecogeomorphic processes, we examined aboveground plant responses and sediment accretion in three locations relative to the shoreline (low, mid, and high) within a tidal marsh at Grand Bay National Estuarine Research Reserve, Mississippi, USA. This study site was affected by two hurricanes in the fall of 2008, and subsequently burned as part of a controlled experiment in January 2009, permitting examination of the effects of two disturbance types on aboveground plant responses and vertical accretion. Fire and hurricanes affected these response variables differently, with effects dependent on location within the marsh. Fire significantly reduced standing aboveground biomass, and subsequent recovery of vegetation relative to pre-burn levels was faster in low marsh plots nearest to the shore than in high marsh plots closest to the marsh-pine ecotone. Hurricanes introduced sediment to the marsh platform, resulting in greater accretion in low marsh plots that had more standing biomass and higher stem densities than high marsh plots. Collectively, these results demonstrate that disturbances can heterogeneously affect surface soil-building processes in marshes through effects on sediment and organic matter accumulation, which may have important consequences for surface elevation maintenance in coastal marshes.

Importance of community stakeholder participation in coastal freshwater and tidal wetland monitoring and restoration has become increasingly recognised. In Australia, Land and Sea Rangers (LSR) are appointed land and sea custodians from local indigenous communities and under guidance of experts learn a range of scientifically relevant and rigorous sampling techniques to protect and conserve Country. Scientific training to build LSR confidence to tackle restoration and conservation of sensitive and culturally important wetlands is shown here. Between May 2014 and May 2015 three training campaigns were completed where LSR on Boigu and Saibai Islands (the most northern islands in the Torres Straits, Australia), completed water quality and wetland flora/fauna surveys across both islands. Forty wetland fauna species were documented (with a similar wetland assemblage on each ANOSIM P > 0.4) comprising 35 fish species (including the invasive freshwater climbing perch, Anabas testudineus), two crustaceans, a freshwater turtle (Chelodina oblonga) (a relic freshwater species after the last sea level rise approximately 6,000 years ago in the region), and two mangrove snakes (Myron richardsoni and Fordonia leucobalia) (both snake records represent a range extension). This data was presented at community workshops with the purpose to build LSR confidence, and with the community, develop a plan to conserve wetland cultural and environmental values. Five thematic wetland conservation themes were identified which resulted in agreeing to management actions necessary on both islands. Since the inception of this program in 2014, additional LSR restoration and monitoring programs have extended to wetlands on other islands in the Torres Straits. We advocate the need for more remote area wetland monitoring and management programs facilitated through LSR programs.

Recent salt marsh and barrier island restoration efforts in the northern Gulf of Mexico have focused on optimizing self-sustaining attributes of restored marshes to provide maximum habitat value and storm protection to vulnerable coastal communities. Salt marshes in this region are dominated by Spartina alterniflora and Avicennia germinans, two species that are valued for their ability to stabilize soils in intertidal salt marshes. We conducted a controlled greenhouse study to investigate the influences of substrate type, nutrient level, and marsh elevation on the growth and biomass allocation of S. alterniflora and A. germinans, and the consequent effects on soil development and stability. S. alterniflora exhibited optimal growth and survival at the lowest elevation (− 15 cm below the water surface) and was sensitive to high soil salinities at higher elevations (+ 15 cm above the water surface). A. germinans performed best at intermediate elevations but was negatively affected by prolonged inundation at lower elevations. We found that although there was not a strong effect of substrate type on plant growth, the development of stressful conditions due to the use of suboptimal materials would likely be exacerbated by placing the soil at extreme elevations. Soil shear strength was significantly higher in experimental units containing either S. alterniflora or A. germinans compared to unvegetated soils, suggesting that plants effectively contribute to soil strength in newly placed soils of restored marshes. As marsh vegetation plays a critical role in stabilizing shorelines, salt marsh restoration efforts in the northern Gulf of Mexico and other storm impacted coasts should be designed at optimal elevations to facilitate the establishment and growth of key marsh species.

Penaeid shrimp represent an important group of valuable exploited species known to either directly utilise saltmarsh habitat, or utilise saltmarsh-derived productivity. Consequently, both areal coverage and primary productivity of saltmarsh habitat has direct consequences for the productivity of these important fisheries, and they are likely to be key beneficiaries of habitat repair. This study aimed to establish quantitative estimates of abundance of School Prawn, Metapenaeus macleayi, across a recovering wetland system; Hexham wetland in the Hunter River. Six surveys were conducted across the wetland using a specialised benthic sled, and absolute abundance of School Prawn was estimated. School Prawn were consistently more abundant in certain areas of the wetland (the highest abundance site supported 1017 prawns per 100 m2), and the average density across the wetland was 244 prawns per 100 m2. All areas of the wetland (except the area closest to the wetland mouth) supported the full range of size classes, and multiple cohorts of prawns moved through the system during the sampling program. The asymmetry observed in the distribution of prawns across the wetland is likely to be due to a combination of water quality and inter-specific interactions. These results show that the recovering wetland is supporting a high abundance of School Prawn. Our estimates of recruitment for School Prawn will also be useful in gauging the potential increases in fisheries productivity arising from habitat repair in this, and other systems.

Nitrogen (N) and Silicon (Si) availability can affect the vigor and resiliency of plant communities. The effects of N on plant growth has been investigated in multiple species and is understood to promote growth. Though it is generally understood that Si aids in plant functions such as stem strength enhancement and herbivory defense, the role Si has not been explored in many wetland plant species. Tidal wetland plants are often subjected to high wind and wave energy, which can cause breakage or collapse of stems. This body of research investigated the combined effects of Si and N regimes to reduce the occurrence of stem collapse through its influence on stem strength. We investigated the effects of Si and N concentration on the growth, morphology, and physiology of Schoenoplectus acutus and Schoenoplectus californicus, two species of macrophytes that are commonly used in freshwater tidal restoration plantings. Individuals of each species were grown hydroponically in four different nutrient combinations (low Si and low N, low Si and high N, high Si and low N, and high Si and high N). Results indicated that increased N concentrations promoted aboveground biomass production, whereas increased Si concentration enhanced stem strength and decreased the likelihood of stem collapse and herbivory. Plants receiving a high Si and low N nutrient combination exhibited the most robust stems. Our findings emphasize the importance of Si, as well as N, in Schoenoplectus spp. growth and highlight the potential applications for these nutrients in enhancing tidal marsh management.

In Canada and elsewhere in North America, impoundments are created in compensation for historic wetland loss and for habitat loss due to development projects, but these new sites are infrequently evaluated to determine how effectively they function. The Cumberland Marsh Region (CMR), located at the head of the Bay of Fundy, Canada, is of importance to migratory birds and has been subject to 300+ years of anthropogenic alteration, including impoundment creation on diked and drained tidal marsh in the last five decades. Wetland managers have noticed a pervasive decline in impoundment productivity leading to reduced waterbird usage (senescence). To understand factors that promote senescence, we analyzed abiotic and biotic proxies in sediment archives from six freshwater impoundments in two coastal watersheds to assess spatial trends across the CMR within recent decades. Our results demonstrate that impoundment productivity is driven by autochthonous nutrient sources (C/N between 7.7 and 14.4), but biogeochemical conditions can be highly variable among impoundments despite their proximity. Biogeochemical variation among top-of-core sediment samples from each impoundment was generally minimal, and thus we believe that the aging of impoundments has resulted in low productivity and organic matter accumulation due to dike stabilization and declines in nutrient loading. We conclude that these freshwater impoundments (in the CMR and likely other similar settings) are not highly productive, and may not provide abundant forage and optimal wildlife habitat which is expected of these systems; adaptive management strategies and hydrologic rehabilitation merit consideration to enhance ecological functioning. Understanding landscape attributes, hydrologic dynamics, and conditions prior to and after major human alterations should be a priority in future compensation projects.

An oligotrophic coastal freshwater marsh converted to open water within months after receiving partially-treated sewage water in fall 2006. Rafts of the upper 60 cm of marsh soil were found throughout the area within two years, as parts of the 1100 year-old marsh were re-distributed in the open water. We examined the marsh soils from 2009 to 2012 to determine some of the cause-and-effect consequences of their decomposition to the formation of these floating mats. There was a lack of herbivory damage in April 2009 where the outer boundary of the soil profile was weakened at 50–60 cm depth, and eventually converted to open water. A 2012 storm event flooded the area by 1.5 m, resulting in new marsh mat ‘pop-ups’ whose bottom underside was coincidental with the layer of maximum decline in soil strength in the sewage treated area. We conclude that the addition of partially-treated sewage weakened the soil structure during this high water event and others to allow for the vertical separation of the marsh as the buoyancy forces exceeded the marsh’s anchor strength, thereby exposing the softer older peats to decomposition, and smothering marsh underneath the mat’s new location. A chronic effect of eutrophication on these marshes was, therefore, revealed in a dramatic flooding event. A bottom up (nutrient addition), not top-down stress (herbivory) contributed to wetland loss in the area, and is a potentially significant chronic stressor for other eutrophied marshes with significant aboveground flooding.

Managed re-alignment of sea defences is seen as the way to strengthen these by rationalising the line between land and sea and creating a buffer of inter-tidal habitat in front of them. This buffer is most commonly salt marsh which absorbs wave energy thus protecting the defences. The global area of salt marsh is in decline due to a range of issues and managed re-alignment is a way of creating or recreating this important habitat. This review examines managed re-alignment schemes in the light of salt marsh loss, rising sea levels and a changing climate. The ecosystem services and benefits provided by salt marsh can be assessed and given a monetary value. Managed re-alignment can be an important tool for salt marsh creation and coastal zone management. The number and size of schemes in the UK has increased in recent years but the area of recreated salt marsh is still insufficient to replace that lost by erosion and other processes. Background data from a proposed site, and adjacent areas likely to be affected, need to be collected prior to embarking on a scheme that may prove successful. Stakeholder interests cannot be neglected and there will also be a need for long-term monitoring. Re-created salt marshes may form an effective sea defence buffer but they remain significantly different from adjacent natural marshes for many years both in their vegetation and functional equivalence.

Water resource development has decreased water delivery to marshes in the Nueces Delta, Corpus Christi, Texas, USA by 45% since 1983, which has led to marsh degradation. Recent management actions will allow for partial hydrological restoration of the marsh, but there is a need to understand the dynamics and the interactive roles of climate and water cycle changes in order to predict changes in salt marshes in the future. In this study, a model of multi-species competition with respect to hydrological change was developed to perform modeling experiments of the effects of water elevation on development of marsh plant species. Nueces Delta plants were divided into two functional groups: (1) clonal stress tolerant plants (Batis maritima, Distichlis spicata, Monanthcloe littoralis, and Salicornia virginica), and (2) clonal dominants (Borrichia frutescens and Spartina alterniflora). Growth rates were calculated for three climate regimes (wet, moderate, and dry), and in three elevation locations (low, mid, and high marsh). The model predicts reductions in plant cover in both drought and moderate conditions. Marsh plant coverage increases only during wet conditions and when there is space available for plant expansion. It is concluded that changes in areal extent of the marsh largely depend on water flow and elevation, which in turn depends on the quantity of fresh water flowing into the marsh. However, under current climate and water management conditions, the marsh will degrade further.

Salt marshes are wet environments at the transition between land and sea, which are inhabited by species that are adapted to stressing environmental factors, such as frequent tidal inundations and highly variable salinity. The rapid and global disappearance of these ecosystems results in the loss of those species that here have their typical habitat. In the lagoon of Venice, a programme for the protection of the surviving salt marshes was initiated by building dredge islands in the framework of more comprehensive restoration work. The ecological characterisation of these man-made habitats was studied through analysing the beetle fauna established on six dredge islands with different topographical traits. Beetle assemblages were evaluated by analysing species richness and abundance. The observed species were arranged in ecological groups and within sub-habitats, delimited according to the zonation of halophytes and ruderal vegetation. Both the composition and distribution of the beetle assemblages were strongly affected by the soil elevation, which determines the salinity gradient and the flooding rate. Hygrophilous and halobious taxa were dominant; however, many generalist taxa were present on some higher islands characterised by areas with a height greater than 60 cm above the mean sea level. Notably, these rarely submerged soils hosted some uncommon halophilous species, as well as thermophilous taxa typical of Mediterranean habitats that were not present on the surrounding mainland. Overall, although the dredge islands possessed some topographical traits that differed significantly from those of the natural salt marsh, they proved to host the biotic communities typical of these latter habitats, as well as other saline soil specialists.

Carbon stored in soil and vegetative biomass in mangrove swamps, salt marshes, and seagrass flats (“coastal blue carbon”) is a significant component of the coastal carbon budget due to the ability of these ecosystems to sequester atmospheric carbon dioxide as plant biomass and peat. Growing interest in the protection of these essential yet vulnerable coastal ecosystems, as well as recognition of their capacity to sequester atmospheric carbon dioxide, has led to the need for rapid and accurate quantification of location-specific coastal blue carbon stocks. This study provides allometric equations for the calculation of aboveground dry biomass based on plant height for 18 salt marsh species from Tampa Bay, Florida, USA. The 18 plant species were also analyzed for carbon and nitrogen content to determine the appropriate carbon conversion factor to use for blue carbon calculations. The salt marsh plants had an average of 1.2 ± 0.4% nitrogen and 41.1 ± 5.5% carbon. With the exception of Batis maritima, which had a carbon content of only 23.4%, carbon content for all other species ranged from 33.4–47.1%. The four most succulent plant species in this study contained an average of 33.3 ± 7.0% carbon, while the nine graminoid species contained 44.4 ± 2.0% carbon. These species-specific equations and carbon data provide non-destructive methods to rapidly quantify vegetative biomass and carbon stocks for monitoring efforts and blue carbon stock assessments.

Australia’s developed coasts are a heavily competed space, subject to urban, industrial and agricultural development. A diversity of habitats, such as mangroves, saltmarshes and seagrasses, comprise Australia’s coastal seascape and provide numerous benefits including fish productivity, carbon sequestration, nutrient cycling, coastal protection and recreation. Decision makers need to be able to weigh up the relative costs and benefits of coastal development, protection or repair and to do this they need robust, accessible and defensible data on the ecological function and economic value of Australia’s coastal seascapes. We reviewed the published literature, with a focus on saltmarsh as a vulnerable ecological community, to determine the availability of information on key ecological functions that could inform ecosystem service valuation. None of the publications we reviewed quantified nutrient cycling, coastal protection or recreation functions. Only 13 publications presented quantitative information on carbon sequestration and fish productivity. These were limited geographically, with the majority of studies on sub-tropical and temperate saltmarsh communities between south-east Queensland and Victoria. This demonstrates a lack of quantitative information needed to substantiate and communicate the value of Australia’s saltmarshes in different locations, scales and contexts. Research should focus on addressing these knowledge gaps and communicating evidence in a relevant form and context for decision-making. We discuss four principles for research funding organisations and researchers to consider when prioritising and undertaking research on key ecological functions of Australia’s saltmarshes, and coastal seascapes more broadly, to support sustainable coastal development, protection and repair for long-term economic and community benefit.

Estuaries are composed of multiple interconnected habitat types used by transient fish species during their period of estuarine residency. Structural marsh management restricts habitat connectivity and impedes the movement of fishes among these habitat types by limiting access via water control structures (WCSs) between the managed area and the rest of the estuary. While some general information on fish passage rates is available, species-specific information on passage through WCSs is lacking for salt marsh fishes. We monitored tagged fishes from March 2012 through November 2013 using passive integrated transponder antenna arrays at two identical WCSs in the Calcasieu Lake estuary, Louisiana, USA, to assess the effect of slotted WCSs on fish behavior. A total of 420 individuals of 15 species was tagged and released at the WCSs; of these, 145 individuals representing 11 species were later detected at the WCSs. Five species comprised most (93%) of the detected individuals: Elops saurus (n = 60), Mugil cephalus (n = 43), Sciaenops ocellatus (n = 20), Pogonias cromis (n = 7), and Ariopsis felis (n = 5). Passage rates were low, with most of the observed fishes (n = 80) passing only once through the structures. Other than E. saurus, which was only observed migrating out of the managed marsh, no clear pattern in swimming direction was observed for the other species. Detected species were all present primarily during the summer and fall, however, diel activity at the structures varied by species. The WCSs in our study area appeared to attract and congregate fishes, functioning more like ecological hotspots, rather than simply facilitating fish passage.

Saline wetlands may be well suited for purifying contaminated water from saline agriculture and aquaculture or from freshwater-based agriculture in areas subject to increased salinity. However, case studies on the nutrient removal efficiency of halophyte species are scarce, especially for temperate regions. Here we tested the nutrient removal efficiency and ability to store nutrients in aboveground and belowground biomass of three halophyte species, Aster tripolium, Bolboschoenus maritimus subsp. compactus, and Spartina anglica, in a greenhouse microcosm experiment at two salinity levels. Nutrient removal from water differed among the species: Spartina had the highest nitrogen removal, Bolboschoenus and Spartina had the highest phosphorus removal. The species also differed in the allocation of the nutrient uptake. Bolboschoenus had the highest absolute uptake of nitrogen and phosphorus in shoots, whereas Spartina had the highest uptake of nitrogen and phosphorus in roots. The applicability of these three species in constructed saline wetlands depends on the local salinity and water regime.

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

In coastal South Carolina, most impounded marshes are managed for waterfowl; fewer are managed for fishes. Tidal control is central to each strategy but raises concerns that nursery function could be impaired. This research examined the assemblage composition of fishes during early-life stages. We sampled two impoundments of each management type monthly in 2008 and 2009. We used light traps to collect 61,527 sub-adult fish representing 21 species and 16 families and push nets to collect 12,670 sub-adult fish representing 13 species and 11 families. The effective number of species detected at larval stage in “fish” impoundments (summer mean = 2.52 ± 0.20, winter mean = 2.02 ± 0.66) was greater than in “waterfowl” impoundments (summer mean = 1.27 ± 0.14, winter mean = 1.06 ± 0.09); CI = 90 %. Species richness did not differ between management types, but hierarchical linear models predicted differences in assemblage composition. These findings underscore the importance of frequent water exchange for maintaining diverse assemblages of early-life-stage fishes in marsh impoundments.

Growth and survival of transplanted vegetation for salt marsh restoration can be greatly affected by edaphic conditions. We investigated the potential for an organic carbon sediment amendment, alginate, to enhance establishment and growth of Spartina alterniflora transplants, as well as colonization by macroinvertebrates commonly associated with S. alterniflora (Uca sp. and Littoraria irrorata). Plots were established in a bare mud area previously inhabited by S. alterniflora, and transplant rhizospheres were either treated with alginate or left unamended as controls. Growth of transplanted S. alterniflora and colonization by Uca sp. and L. irrorata were evaluated over portions of three growing seasons. Within the first month post-transplantation, a nonsignificant trend toward greater live stem density emerged, but disappeared completely by week ten. Both Uca sp. and L. irrorata densities were significantly greater in the alginate treatment compared to the control only during the first ten weeks post-transplantation. However, the initial organic content of the sediment in the transplant area was more than twice that in the adjacent natural marsh. Therefore, our findings suggest that a threshold level of sediment organic matter above which alginate addition does not confer an advantage on transplanted S. alterniflora may exist, and the conditions under which amendments are most beneficial to transplanted S. alterniflora should be determined.

Salt marshes of Samborombon Bay (Argentina) have been grazed sporadically at very low stocking rates, but in the last decade, grazing intensity increased due to agriculture expansion. We investigated the effect of cattle grazing on vegetation and soil salinity on the most extended Spartina densiflora community. This community develops along an elevation gradient where the frequency and duration of tidal flooding and soil salinity increased as elevation decreased. Vegetation and soil data were collected from a national park excluded to cattle grazing for 30 years and from an adjacent commercial livestock farm continuously grazed by cattle. As elevation level decreased, plant cover, richness and diversity of functional groups and species decreased. As we expected, grazing altered soil salinity and vegetation composition in different extent along the elevation gradient. Grazing changed vegetation structure more intensively in the high elevation level because it reduced the competitive exclusion exerted by S. densiflora, allowing the increase in floristic richness. Grazing increased soil salinity and the contribution of salt-tolerant species only in the medium but not in the low elevation level probably because the higher frequency and duration of tidal flooding counterbalanced the increase in evaporation promoted by biomass removal in the low respect to the medium elevation level. While grazing may cause positive impacts for plant conservation in the high elevation level, it may cause negative consequence for livestock production because of the reduction in forage quality along the entire elevation gradient.

In New England salt marshes, man-made earthen barriers, or berms, are generally historic, small-scale (average height = 0.71 m ± 0.12 SE; average length = 166 m ± 41 SE) tidal restrictions which originated from past agricultural, industrial, and environmental practices. The orientation and size depends primarily on the original purpose of the barrier, but this study examines the effects of berms oriented parallel to the incoming tide such that some landward portion of the marsh receives a different tidal signal than the seaward portion. Our hypotheses considered the impacts of the altered hydrology on pore water chemistry and edaphic characteristics. The results indicate that the effect of berms on salt marsh physical structure varies significantly by site. Where the tidal flooding frequency is restricted and drainage is poor, the landward marsh shows pool development, high salinity and sulfide concentrations, and low vegetation cover. In contrast, where tidal flooding is inhibited but the marsh soils are well-drained, salinity and sulfide concentrations decrease and accelerated decomposition results in subsidence and reduced soil organic matter. Given these findings, impacts from berms may impair salt marsh function and resilience to invasive plants and sea level rise.

Salt marshes exhibit striking vegetation zonation corresponding to spatially variable elevation gradients which dictate their frequency of inundation by the tides. The salt marshes in the upper Bay of Fundy, a dynamic hypertidal system, are of considerable interest due to increasing recognition of salt marsh ecosystem values and the extent of prior conversion of salt marshes to agricultural lands, much of which are no longer in use. To determine the suitability of two potential restoration sites at Beausejour Marsh in New Brunswick, Canada, geomatics technologies and techniques were used to assess vegetation and elevation patterns in an adjacent reference salt marsh and the proposed restoration sites. Light detection and ranging digital elevation models (DEMs) were created for the reference marsh and the restoration sites in both the spring (leaf-off) and late summer (leaf-on, maximum biomass) periods. Aerial photographs and Quickbird multispectral imagery were used to visually interpret vegetation zones on the reference marsh and were field validated using vegetation characteristics from quadrats referenced with differential GPS. Elevation limits of the salt marsh vegetation zones were extracted from the DEM of the reference marsh and applied to the DEM of the restoration sites to determine the percentage area of each site that would be immediately suitable for new salt marsh growth. Of the two restoration sites assessed, one had experienced significant subsidence since dyking; only about 40 % of the site area was determined to be of sufficient elevation for immediate vegetation colonization. The second site, while more than 88 % suitable, would require the installation of a large dyke on the landward side of the restoration site to prevent flooding of adjacent lands. This study provides essential high resolution elevation and vegetation zonation data for use in restoration site assessments, and highlights the usefulness of applied geomatics in the salt marsh restoration planning process.