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The California salt marsh snailMelampus olivaceus, a species from southern California, has established a thriving population in the Elkhorn Slough estuary (Monterey Bay), hundreds of kilometers north of where it is long-established and regularly found. Since the late 1800s this high littoral zone salt marsh snail has occasionally been reported in central California, but only as isolated individuals or shells. We first observed a few individuals ofM. olivaceusin Elkhorn Slough in 2013, and the species is now abundant and reproducing throughout the estuary inSalicornia pacifica(pickleweed) marshes. We also document for the first time that this species has a planktonic, feeding larva. Salt marsh snails may have been transported northward as planktonic larvae during periodic El Niño warm water events. Such transport has been reported for other species, but what makes this case unusual is the persistence, reproduction and abundance of the snail following transport.

Salt marshes can protect coastlines against flooding by attenuating wave energy and enhancing shoreline stabilization. However, salt-marsh functioning is threatened by human influences and sea level rise. Although it is known that protection services are mediated by vegetation, little is known about the role of vegetation structure in salt-marsh accretion. We investigated the role of vegetation presence, vegetation type and structural vegetation characteristics in sedimentation and sediment grain size. We established 56 plots on a salt marsh on the Dutch Wadden island of Texel. Plots were divided over four vegetation types contrasting in vegetation structure and varied in elevation and distance to creeks. Vegetation presence was controlled by clipping in subplots. Within each plot, we measured seven vegetation characteristics, sedimentation and the sediment grain size distribution. Furthermore, we explored the effect of the natural variation in vegetation structure on wave attenuation with a simple model approach. For this, we developed vegetation scenarios based on the field measurements of stem height, diameter and density. We found that vegetation presence increased sedimentation on average by 42%. Sedimentation was highest in Salicornia vegetation and increased with stem height and branching level. Grain size also seemed to increase with branching level. Modelled wave attenuation was 7.5 times higher with natural vegetation compared to topography only, was strongest for Spartina vegetation and most sensitive to the natural variance in stem density. Our results can be used to improve predictions of salt-marsh accretion and the implementation of salt marshes in nature-based flood defences.

If a community and its substrate are raised by tectonic uplift, the species present can either die out in the area, survive in situ unchanged, or survive in situ with adaptation and differentiation. The large-scale passive uplift of plant and animal populations during mountain-building is accepted in a growing number of studies, but the idea has seldom been examined critically. If passive uplift does occur, it has implications for interpreting community structure and speciation in some of the most biodiverse places on Earth, tropical mountains. It would also provide a simple explanation for many altitudinal anomalies, such as the occurrence of typical coastal elements at unusually high altitudes in certain localities. Examples include the coastal saltmarsh plant Salicornia at 4200 m altitude in the rapidly uplifted Andes, coastal frogs and ferns in African mountains, and inland mangroves in New Guinea. The first aim of this paper is to review previous work on passive uplift worldwide and the main ideas that have been discussed. A second goal is to discuss possible tests of passive uplift.

The succulent salt marsh plant Salicornia tegetaria occurs in both temporarily open / closed (TOCE) and permanently open estuaries (POE) where it experiences a wide range of physicochemical conditions in South African estuaries. The study investigated the characteristics of this plant in relation to water level in a TOCE and a POE and showed that cover was stable in the permanently open estuary but changed in response in water level in the temporarily open/closed system. Monthly expansion in S. tegetaria cover was 46% compared to 5.2% in the POE. In the TOCE the life cycle took four months to complete, seedlings emerged two days after the water level dropped, and the habitat was exposed. This was despite the mouth being closed for the whole study period and a mean water depth inundation of 27 ± 6 cm. Plants in the TOCE produced significantly more inflorescences (409 ± 79 per m²) and seed (45 542 ± 9 212 per m2), compared to the plants in the POE where water level was stable (87 ± 9 inflorescences per m² and 7 092 ± 775 seeds per m²). A large sediment seedbank (9 758 seeds m−2) in the TOCE ensures germination when water level drops and conditions become favourable for establishment. These data are important as they indicate that S. tegetaria is a remarkably adaptive species that can grow over a wide range of physicochemical conditions that will allow the species to persist in the face of future future sea level rise and anthropogenic pressures.

Constructed salt marshes as a Nature-Based Solution for coastal defense offer additional benefits over conventional engineering, but project realization is often hampered by practical and governmental obstacles. We assessed the execution of a local-scale salt marsh construction project as a Nature-Based Solution (NBS) with respect to the regional-scale Social-Ecological System (SES) in an explicitly linked NBS-SES framework. A local municipality came up with various plans to develop its waterfront but these proved unrealizable without wider stakeholder participation. Crucial for success was that the local initiative was turned into an NBS integrating livability, biodiversity and flood safety, and that it was linked to the governance systems and actors in a regional SES. The chosen NBS consists of a city beach and two salt marshes, a salt marsh park that is open to the public and a pioneer salt marsh that is only accessible for research. The pioneer salt marsh was constructed by raising the seabed to around mean high tide with sand obtained from a capital dredging project. It was used as a large-scale natural experiment in salt marsh construction. To test the effect of enrichment with silt and clay on initial salt marsh development, six hectare-scale compartments were created in which mud was mixed with sand in the top 1.0 m of the bed to three mud contents of on average 8%, 25% and 48%. Heavy machinery was needed to mix mud through the upper meter of the sandy bed. Mixing mud was softening the sediment causing the machines to sink into the 48% mud enriched bed. To test whether seeding with a pioneer plant species accelerates salt marsh development, fragments of Salicornia procumbens plants were seeded in half of three compartments. Field observations between November 2018 to September 2020 showed that seeding of Salicornia plant fragments resulted in significant differences in vegetation cover and species richness in the first growing season. Mud content showed significant positive effects on vegetation cover and species richness in the two monitored growing seasons, where the compartments with on average 7–9% mud had the lowest vegetation cover and species numbers. When constructing a salt marsh by raising sand and mixing mud, a mud content of 25% is practically feasible and results in high vegetation cover and species richness.

Metal pollution is a well-known anthropogenic impact of highly developed estuaries, with dire consequences to the ecosystem. This study investigated the metal concentrations (Al, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in the sediment colonised by Salicornia tegetaria, a dominant salt marsh plant in the lower intertidal zone of the Swartkops Estuary. The samples were collected at five sites along the banks of the middle and lower reaches of the estuary, and analysed using an Inductively Coupled Plasma - Optical Emission Spectrometer. Metal contamination was determined using established normalised baseline models. It was found that all the sites contained metal enrichment, with the estuary mouth experiencing the least enrichment. Salicornia tegetaria holds a substantial amount of anomalous metals within its rhizosediment — providing a valuable ecosystem service to a highly developed Swartkops Estuary.

The below ground biomass of salt marsh species accounts for more than half of the total plant biomass in salt marsh systems, yet no biomass data exist for salt marsh species in South Africa. The aims of the current study were to compare the biomass allocation of Salicornia tegetaria in six estuaries and relate findings to their environmental conditions. The current study measured the physico-chemical variables of the sediment (moisture content, organic matter content, electrical conductivity, pH) and pore water (temperature, salinity, pH, depth) at Olifants, Berg, Langebaan, Heuningnes, Nahoon and Kwelerha estuaries. Above and below ground biomass and stem height measurements were also collected. The below ground biomass (1.51 ± 0.24 kg m−2) and root/shoot ratio (1.36 ± 0.17) was the lowest at Heuningnes Estuary with no significant difference at the remaining estuaries, suggesting that factors, such as geomorphology and sedimentological processes, could have a stronger effect on the biomass allocation in this species. Important drivers of biomass allocation were sediment pH, redox potential and pore water depth. The current study provides baseline information for S. tegetaria, an endemic salt marsh species, for which there is a paucity of data. This species plays a major role in the ecology of the lower intertidal zone, which will be vulnerable to sea-level rise.

Tidal marshes play an important role in climate change mitigation through natural coastal protection. The effectiveness of the natural coastal defense by tidal marshes is closely related to their channel network which is in turn greatly influenced by their vegetation cover and shape. Previous research suggests a dual effect of vegetation on marsh topography; stabilizing sediment on the one hand versus promoting erosion and channel incision on the other hand. This study links these effects to different vegetation species, Salicornia procumbens, Spartina anglica, and Puccinellia maritima (further referred to as Salicornia, Spartina, and Puccinellia), by means of a coupled bio-hydromorphodynamic modeling study. Single species, species-assemblages, and species shifts were studied, incorporating both species-specific physical plant properties and spatiotemporal growth strategies. The results indicate the influence of vegetation on the marsh topography to be highly species-dependent, but also of a very complex nature. Both the presence of Spartina and Puccinellia resulted in significant channel development, whereas Salicornia did not induce topographic change. The combination of several species promoted or reduced channel development depending on the included species. Species-shifts linked with climatic changes resulted in increased erosion of the existing channel network potentially reducing the protective capacity of the marsh.

The extensive loss of tidal marsh habitat surrounding the San Francisco Bay has led to numerous restoration projects to restore ecosystem function. Native cordgrass (Spartina foliosa) is important for sediment accumulation and nesting habitat for endangered California Ridgway’s Rail (Rallus obsoletus obsoletus), and because salt marshes are typically nitrogen-limited ecosystems, previous restoration studies in California have used nitrogen fertilizers to increase plant growth. This study compared the use of two low-nitrogen, high-carbon fertilizers (Macrosystis pyrifera (kelp) and sodium alginate) to stimulate N2-fixing bacteria inhabiting the S. foliosa rhizosphere in a historic and recently restored marsh in San Francisco Bay. Alginate increased N2-fixation, though there was no observed S. foliosa growth response. Kelp suppressed N2-fixation, and increased the foliar nitrogen content of Salicornia pacifica in mixed Spartina-Salicornia stands. The restored marsh had less than 0.5 μM phosphate in porewaters, suggesting phosphorus, not nitrogen, limits S. foliosa growth in this marsh. Alginate increased rates of N2-fixation and may promote plant growth in marshes exhibiting nitrogen limitation. Phosphate limitation was a surprise considering numerous previous studies indicate nitrogen as the primary limiting nutrient of tidal marsh plants. We recommend first assessing nutrient stoichiometry when considering manipulations to promote plant growth in restored marshes.

The strength of species interactions often varies geographically and locally with environmental conditions. Competitive interactions are predicted to be stronger in benign environments while facilitation is expected to be stronger in harsh ones. We tested these ideas with an aboveground neighbor removal experiment at six salt marshes along the California coast. We determined the effect of removals of either the dominant species, Salicornia pacifica, or the subordinate species on plant cover, aboveground biomass and community composition, as well as soil salinity and moisture. We found that S. pacifica consistently competed with the subordinate species and that the strength of competition varied among sites. In contrast with other studies showing that dominant species facilitate subordinates by moderating physical stress, here the subordinate species facilitated S. pacifica shortly after removal treatments were imposed, but the effect disappeared over time. Contrary to expectations based on patterns observed in east coast salt marshes, we did not see patterns in species interactions in relation to latitude, climate, or soil edaphic characteristics. Our results suggest that variation in interactions among salt marsh plants may be influenced by local‐scale site differences such as nutrients more than broad latitudinal gradients.

In Reserva Natural de Castro Marim e Vila Real de Santo Antonio (SE of Portugal), most of the salt marshes and saltpans are abandoned contributing to their degradation and, consequently, alteration of some ecological conditions. Rehabilitation of these areas by a Salicornia crop can contribute to their economic and environmental improvement by stimulation of biogeochemical processes and biomass commercialization. However, the development of agro-techniques adjusted to species and variable environmental conditions from Mediterranean are needed in order to improve the Salicornia crop. This study aimed to evaluate: i) potential use of seedlings from greenhouse in the field cultivation; and ii) survival, growth and yield of Salicornia under shading and different salinity conditions of the soils and irrigation waters. Autochthonous Salicornia species (S. ramosissima and S. patula) were tested. Germination tests under controlled conditions and in situ mesocosm assays were carried out. Assays were realized with a low density of seedlings from natural conditions and greenhouse, and soils and waters from estuary both with different salinities. Intermediate and high salinities (25-45dS/m) affected only S. patula germination. In general, Salicornia growing in soils with low salinity had great fresh biomass accumulation independently of seedling source (from natural conditions and greenhouse) and/or growing season. The shading seems to improve the fresh biomass accumulation and yield. Under Mediterranean conditions, the transplantation of Salicornia from greenhouse to the field was a promising technique, independently of the salinity conditions. This study demonstrated that the abandoned and saline areas can be rehabilitated by a sustainable crop of Salicornia. project "Cultivo sustentavel de halofitas na Reserva Natural do Sapal de Castro Marim e Vila Real de Santo Antonio" from Programa POAlgarve 21 [ALG-02-0931-FEDER-000022] info:eu-repo/semantics/publishedVersion

To test the effects of site and successional stage on nitrogen fixation rates in salt marshes of the Venice Lagoon, Italy, acetylene reduction assays were performed with Salicornia veneta- and Spartina townsendii-vegetated sediments from three restored (6–14 years) and two natural marshes. Average nitrogen fixation (acetylene reduction) rates ranged from 31 to 343 μmol C2H4·m−2·h−1 among all marshes, with the greatest average rates being from one natural marsh (Tezze Fonde). These high rates are up to six times greater than those reported from Southern California Spartina marshes of similar Mediterranean climate, but substantially lower than those found in moister climates of the Atlantic US coast. Nitrogen fixation rates did not consistently vary between natural and restored marshes within a site (Fossei Est, Tezze Fonde, Cenesa) but were negatively related to assayed plant biomass within the acetylene reduction samples collected among all marshes. Highest nitrogen fixation rates were found at Tezze Fonde, the location closest to the city of Venice, in both natural and restored marshes, suggesting possible site-specific impacts of anthropogenic stress on marsh succession.

Among the few available morphological traits in the genus Salicornia L. (Amaranthaceae/Chenopodiaceae), most are extremely variable within species probably due to high levels of plasticity. In addition, identifying Salicornia taxa is further complicated by that these plants lose many of their diagnostic characters upon drying. Morphological studies of fresh (or liquid preserved) specimens is thus important in taxonomical studies. The objective of this study was a numerical morphological analyses of Salicornia populations in the Nordic countries and an adjacent Russian region with the aim to ascertain whether taxonomic division of this genus based on morphology is feasible. In all, 666 plants were collected for morphometric measurements from 31 localities and 52 populations or subpopulations of the North Sea coasts, Danish straits, Baltic Sea, the Norwegian Sea, Barents Sea, and the White Sea areas. For practical reasons, part of the samples was studied fresh, and part preserved in FAA pending measurements. Data were analyzed by principal component analysis (PCA) and hierarchical cluster analysis. The main taxonomical division was found between the diploid S. europaea s.l. and the tetraploid S. procumbens Sm., and was mainly based on fertile segment and flower morphology characteristics. Data also show ecological differences: diploids inhabit the upper part of salt marshes, whereas tetraploids grow in the hydrolittoral zone and are restricted to areas of regular tidal influence. It was not possible to make a morphological distinction between the two cryptic diploid species S. europaea s.s. and S. perennans Willd. in the present study. North Norwegian S. europaea clearly deviated from more southern populations, but taxonomical conclusions based only on morphology were avoided. In contrast, the division of S. procumbens into two geographical races/subspecies, the southern subsp. procumbens and the northern subsp. pojarkovae was supported.

Macroalgae in estuarine and coastal waters, in contrast to vascular salt marsh plants, have previously been utilised as biomonitors of sediment-held metals. The colonising halophyte Salicornia spp., however, occurs in both mudflats alongside macroalgae, as well as in association with salt marsh vascular plants. The present research aims to determine the relationships between fluctuations in sediment-held metals and those in Salicornia spp. over the course of a growing season. Samples of the species and corresponding underlying sediment were collected from the metal mine-polluted Restronguet Creek of the Fal Estuary, Cornwall on a monthly basis between March and November, 2000. Oven-dried sediment and vegetation samples were analysed for total Fe, Cu, Zn and Mn. Significant correlations with both the roots and aerial portion of the plant were found with sediment Cu and Zn concentrations. Significant relationships with either Mn or Fe were not observed. Thus, Salicornia spp. would appear to be a suitable tool for biomonitoring Zn and, particularly, Cu. Hyperaccumulation of Zn in the aerial portion during initial growth also indicates that Salicornia spp. may be useful for alleviating metal contamination through phytoextraction, whilst Cu in the roots is proposed as having potential for phytostabilization.

In this paper, we constructed the halophyte Mesocosm experimental group which was used as a substrate material that consisted of tidal flat and dredged sediment. Depending on whether the ingredients of vegetation and substrate material of Mesocosm, we constructed Mesocosm A (tidal flat sediment + Salicornia herbecea), Mesocosm B (only dredged sediment), Mesocosm C (dredged sediment + Salicornia herbecea). Monitoring was carried out of seawater quality factors (Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), temperature, salinity), sediment factors (Chemical Oxygen Demand (COD), Total (T-N), Total Phosphorus (T-P) and growth of Salricornia herbecea) in each Mesocosm. Habitat Stability Index of vegetation was calculating by using the monitoring results. HSI of Mesocosm C was calculated from 0.87 to 0.95 as compared to the relatively high HSI Mesocosm A, it was evaluated to be able to be used in the restoration of the coastal salt marsh with dredged sediment.

Oligochaetes (Annelida) are active bioturbators that can be present in high densities in the transition zone between intertidal flats and salt marshes, though their occurrence and functional role remain understudied. This study aimed to clarify the biogeomorphic role of oligochaete bioturbation in facilitating or hindering vegetation establishment. Two microcosm experiments were performed to assess the effect of oligochaete bioturbation on sediment properties, oxidation depth, algal biomass, seed distribution, and germination success of pioneer species Salicornia spp. Oligochaetes created burrow networks in the sediment matrix, which, together with upward conveyor belt feeding, lead to substrate mixing. Sediment reworking rates of oligochaetes were compared with those of polychaete macrofauna. Bioturbation and bio-irrigation of burrows can stimulate resource flows into the sediment. Oxidation depth increased almost tenfold in the presence of oligochaetes. Their bioturbation did not seem to affect sediment properties such as dry bulk density, porosity, and organic matter content. Sediment reworking, however, significantly reduced algal biomass at the surface with possible cascading effects on sediment stability and erodibility. Oligochaete conveyor belt feeding buried Salicornia spp. seeds until below the critical germination depth, thus negatively affecting Salicornia spp. germination and seedling establishment. Our study indicates that small, though numerous, oligochaete bioturbators may reduce lateral expansion potential of salt marshes by hindering the establishment of pioneer vegetation in the transition zone. Additionally, in dynamic fine-grained habitats, these oligochaetes have the feature to quickly oxygenate the sediment top layer.

Climate change shuffles species ranges and creates novel interactions that may either buffer communities against climate change or exacerbate its effect. For instance, facilitation can become more prevalent in salt marshes under stressful conditions while competition is stronger in benign environments. Sea-level rise (SLR) is a consequence of climate change that affects the distribution of stress from inundation and salinity. To determine how interactions early in SLR are affected by changes in these two stressors in Mediterranean-climate marshes, we transplanted marsh turfs to lower elevations to simulate SLR and manipulated cover of the dominant plant species, Salicornia pacifica (formerly Salicornia virginica). We found that both S. pacifica and the subordinate species were affected by inundation treatments, and that subordinate species cover and diversity were lower at low elevations in the presence of S. pacifica than when it was removed. These results suggest that the competitive effect of S. pacifica on other plants is stronger at lower tidal elevations where we also found that salinity is reduced. As sea levels rise, stronger competition by the dominant plant will likely reduce diversity and cover of subordinate species, suggesting that stronger species interactions will exacerbate the effects of climate change on the plant community.

Background and aims Salt marsh plant communities will be among the first to be exposed to the predicted increase in sea level and to the associated environmental changes. The objectives of this study

We investigated the potential for an invasive sea lavender, Limonium ramosissimum subsp. provinciale (Algerian sea lavender; LIRA) to spread in San Francisco Estuary (SFE) tidal marshes by testing how two determinants of tidal marsh plant distribution, salinity and inundation, affect LIRA dispersal, germination, growth, and reproduction. Simulating dispersal in 0, 15, and 30 parts per thousand (ppt) salinity water, we found seeds remained afloat similarly regardless of salinity, and seed viability after floatation was high (88%); however, seeds in 0 ppt aquaria germinated after just 4 d, suggesting shorter dispersal distances in fresh than in brackish or saline water. Next, we compared LIRA and native halophyte seed germination in 0, 15, 30, and 45 ppt water. Percentage of germination was similar between species after 3 wk, but LIRA germinated faster in fresh water than all native species (90% vs. 5% germination after 4 d), suggesting a possible establishment advantage for LIRA at low salinities. Finally, we grew LIRA under crossed salinity and inundation levels in a tidal simulator for a growing season. LIRA growth and seed production increased when either salinity or inundation was reduced. We conclude that spread could be greatest among salt marshes due to high potential for seed dispersal in saline water, yet spread within marshes may be greatest in relatively lower salinity conditions where growth and reproduction are maximized.

Halophytes are naturally adapted in saline environments, where they benefit from the substantial amounts of salt in the growth media. The need for salt-tolerant crops increases as substantial percentages of cultivated land worldwide are affected by salinity. There are few protocols, guidelines, or trials for glasswort (Salicornia (L.) and Sarcocornia (Scott), belong to the Amaranthaceae) field cultivation. The high salt tolerance and content in bioactive compounds make glassworts one of the most important candidates for future use both for fresh and processed food, due to their functional and health properties. This review describes the glassworts respect to their biodiversity and the most important factors affecting propagation, salt tolerance traits, agro-techniques and yields, food uses and nutraceutical properties.

The Plopul salt marshes, Tulcea County, developed within the perimeter of Lake Beibugeac, have been identified as having a high concentration of halophytes on a relatively small area of about 100 ha. These have formed vegetal communities that fit within two types of Natura 2000 habitats: 1310 Communities of Salicornia and other annuals colonising mud and sand and 1530* Pannonic salt steppes and salt marshes. Four of the 57 species recorded are rare at national level: Halocnemum strobilaceum, Limonium bellidifollium subsp. danubiale, Limonium meyeri and Salicornia prostrata. The area currently has a SPA (Special Protection Area) status, but the unique concentration of halophytes, the presence of Natura 2000 habitats and of rare species, also recommend the area for designation as a SCI (Sites of Community Interest).

In tidal marshes, facilitative and competitive interactions between plant species can shift in response to variation in stress gradients (e.g., inundation and salinity) and resource gradients (e.g., nutrient availability). We measured plant competitive response using relative yield based on total biomass of salt marsh species Salicornia virginica and Triglochin concinna. We tested interactions between these species in two greenhouse experiments using an additive experimental design which included nitrogen supply, water level, and duration (4-months and 1-year) treatments. We repeated two N-supply treatments in a 1-year field experiment at two elevations. We found that competitive and facilitative processes were dependent on the type of stress, the species, and the experiment duration. We found a facilitation-competition shift along the N-availability gradient, but only for Salicornia in the 4-month experiment. We found no effect of N addition on competitive response in the 1-year experiment; relative yield values remained

In the Hudson–James Bay system, grubbing and grazing by lesser snow geese have resulted in severe devegetation of coastal marshes. These changes likely represent an example of an alternative stable state; however, long-term datasets documenting whether revegetation is occurring are scarce. Here, we report results of a 10-year study investigating changes in the state of a degraded salt marsh system on the north coast of Akimiski Island, Nunavut. Four transects were intensively sampled in 1998 and 2008, two within the dense nesting and brood-rearing area of a snow geese colony, one on the colony edge, and one outside it; all of these sites were also used by broods of Canada geese. Key forage species (Puccinellia phryganodes, Festuca rubra, Carex subspathacea) were less common near the colony center than elsewhere; biomass of Puccinellia also tended to be lower in more central areas. Forage species often increased in abundance between samplings, but the magnitude of changes was small. In contrast, non-forage species (Salicornia, Spergularia, Glaux) often reached high abundance within the colony center; some (Salicornia) decreased while others (Spergularia) increased. We argue the degraded state was initiated by foraging damage from an exceptional stopover of 295,000 staging birds in 1972 and that the combined foraging pressure of relatively small numbers of nesting and migrant geese since then, coupled with soil changes, has been sufficient to maintain devegetated areas as a persistent alternative state. Whether or not this state is truly stable, further recovery is likely to be very slow.

The high marsh in southeast Atlantic coast salt marshes forms a relatively small but ecologically important transition zone between low marsh and the terrestrial shoreline. However, long-term trend data from high marshes are limited to a few studies. Permanent plots established in a high marsh near Waties Island in northeast South Carolina were measured for plant coverage from 2002–2010. At the beginning and at the end of the study, four groups of plots were identified: mixed indicated by Borrichia frutescens, Distichlis spicata, and Fimbristylis castanea; Juncus indicated by Juncus roemerianus; Salicornia indicated by Salicornia virginica; and Spartina indicated by Spartina patens. Ordination of the 2010 plot data and soil analyses produced clear separation of the groups along a single dominant axis with Salicornia and Juncus groups at the high end of a salinity gradient and the Spartina group at the high end of soil organic matter gradient. Comparison of plots classified in 2002 to the same p...

The purpose of this paper was to examine the vegetative, sedimentary, nekton and hydrologic conditions pre-restoration and the initial 2 years post-restoration at a partially restricted macro-tidal salt marsh site. Replacement of the culvert increased tidal flow by 88%. This was instrumental in altering the geomorphology of the site, facilitating the creation of new salt marsh pannes, expansion of existing pannes in the mid and high marsh zones, and expansion of the tidal creek network by incorporating relict agricultural ditches. In addition, the increase in area flooded resulted in a significant increase in nekton use, fulfilling the mandate of a federal habitat compensation program to increase and improve the overall availability and accessibility of fish habitat. The restoration of a more natural hydrological regime also resulted in the die-off of freshwater and terrestrial vegetation along the upland edge of the marsh. Two years post-restoration, Salicornia europea (glasswort) and Atriplex glabriuscula (marsh orache), were observed growing in these die-back areas. Similar changes in the vegetation community structure were not observed at the reference site; however, the latter did contain higher species richness. This study represents the first comprehensive, quantitative analysis of ecological response to culvert replacement in a hypertidal ecosystem. These data will contribute to the development of long-term data sets of pre- and post-restoration, and reference marsh conditions to determine if a marsh is proceeding as expected, and to help with models that are aimed at predicting the response of marshes to tidal restoration at the upper end of the tidal spectrum.

Sources of sedimentary organic matter to a Morse River, Maine (USA) salt marsh over the last 3390 ± 60 RCYBP (Radiocarbon Years Before Present) are determined using distribution patterns of n -alkanes, bulk carbon isotopic analysis, and compound-specific carbon isotopic analysis. Marsh foraminiferal counts suggest a ubiquitous presence of high marsh and higher-high marsh deposits (dominated by Trochammina macrescens forma macrescens , Trochammina comprimata , and Trochammina inflata ), implying deposition from ∼0.2 m to 0.5 m above mean high water. Distributions of n -alkanes show a primary contribution from higher plants, confirmed by an average chain length value of 27.5 for the core sediments, and carbon preference index values all >3. Many sample depths are dominated by the C 25 alkane. Salicornia depressa and Ruppia maritima have similar n -alkane distributions to many of the salt marsh sediments, and we suggest that one or both of these plants is either an important source to the biomass of the marsh through time, or that another unidentified higher plant source is contributing heavily to the sediment pool. Bacterial degradation or algal inputs to the marsh sediments appear to be minor. Compound-specific carbon isotopic analyses of the C 27 alkane are on average 7.2‰ depleted relative to bulk values, but the two records are strongly correlated ( R 2 = 0.89), suggesting that marsh plants dominate the bulk carbon isotopic signal. Our study underscores the importance of using caution when applying mixing models of plant species to salt marsh sediments, especially when relatively few plants are included in the model.

The salt marsh dodders, Cuscuta salina, have been historically delimited as a morphologically variable assemblage of inbreeding forms that parasitize hosts growing in alkaline or saline habitats from western North America. This morphological diversity has been tradi- tionally classified into three varieties: salina , major , and papillata . A morphometric analysis of floral characters and a molecular study using both plastid and nuclear DNA sequences strongly support the segregation of a new species, Cuscuta pacifica Costea and M. A. R. Wright, from C. salina . The new species corresponds to a lineage that includes varieties major and papillata , whereas C. salina is limited essentially to its type variety. Cuscuta pacifica and C. salina are sister species that have only a small area of parapatry in lower California, where they are ecologically and reproductively separated. Cuscuta salina occurs mostly in inland vernal pools and salt flats of Arizona, California, Nevada, Utah, Baja California, and Sonora, and grows primarily on Frankenia and Suaeda . Cuscuta pacifica can be found in salt marshes from the south- central Pacific coast of California north into British Columbia, parasitic especially on Salicornia and Jaumea carnosa . Cuscuta salina var. papillata (Yunck.) Costea and M. A. R. Wright, parasitic on hosts that grow in coastal interdunes, falls within the range of variation of C. pacifica , where it is transferred.

The seed banks of two temporarily open/closed estuaries in South Africa were quantified in this study. Charophyte oospores represented almost 72% of the sexual propagules in the sediment with a mean oospore density of 31,306 oospores m−2. This was followed by the seeds of the intertidal salt marsh plant Sarcocornia perennis (18%) (7929 seed m−2) and the submerged angiosperm Ruppia cirrhosa (7%) (2852 seeds m−2). The remaining 3% was made up of a mixture of species such as Salicornia meyeriana, Sporobolus virginicus, Stukenia pectinata, Bolboschoenus maritimus and terrestrial species. Although seed density did not differ significantly with depth, seeds still occurred at 20 cm depth providing a regeneration source in the event of sediment disturbance. Three salinity (0, 17 and 35 PSU) and moisture treatments (exposed, waterlogged and submerged) were applied to collected sediment to determine how fast species would germinate. S. perennis germinated after 3 d to a maximum of 82%. Submerged species began to germinate only after 18 d (Chara vulgaris and R. cirrhosa) and had low germination percentages of between 11 and 15% after 91 d. Results from this study indicate that in the event of unpredictable disturbance events such as water level fluctuations, large sediment seed reserves would ensure habitat persistence.

The potential for marsh plants to be vectors in the transport of mercury species was studied in the natural, mature, tidal China Camp salt marsh on San Pablo Bay. The fluxes of organic matter, mercury (THg), and monomethylmercury (MeHg) were studied in natural stands of Spartina foliosa and Salicornia virginica. Seasonal fluxes from the sediment into aboveground biomass of live plants and subsequent transfer into the dead plant community by mortality were measured. Loss of THg and MeHg from the dead plant community through fragmentation, leaching, and excretion were calculated and were similar to net uptake. Seasonal data were added up to calculate annual mass balances. In S. foliosa, annual net production was 1,757 g DW m−2, and the annual net uptakes in the aboveground biomass were 305 μg THg m−2 and 5.720 μg MeHg m−2. In S. virginica, annual net production was 2,117 g DW m−2, and the annual net uptakes in aboveground biomass were 99.120 μg THg m−2 and 1.990 μg MeHg m−2. Of both plant species studied, S. foliosa had a slightly lower production rate but greater mercury species uptake and loss rates than S. virginica, and, consequently, it is to be expected that S. foliosa matter may affect the local and possibly the regional food web relatively more than S. virginica. However, the actual effects of the input of mercury-species-containing plant-derived particulate matter into the food webs would depend on trophic level, food preference, seasonal cycle of the consumer, total sediment surface area vegetated, location of the vegetation in the marsh landscape, and estuary bay landscape. Since the levels of mercury species in dead plant material greatly exceed those in live plant material (on a dry weight basis), detritivores would ingest greater mercury species concentrations than herbivores, and consumers of S. foliosa would ingest more than consumers of S. virginica. The greatest THg and MeHg losses of both plant species due to mortality and to fragmentation–leaching–excretion occurred in late spring and early autumn, which corresponds to peak MeHg levels observed in sediments of coastal systems of previous studies, suggesting enhanced THg–MeHg export from the marsh to the nearshore sediment.

Annual plants that coexist among perennial dominants might persist in microsites that are stressful to their competitors. In Californian salt marshes, where cover of annual and perennial Salicornia species are negatively correlated, we hypothesized that waterlogged depressions support the annual (Salicornia bigelovii) but not the region’s dominant perennial (Salicornia virginica). In a large restoration site, S. virginica cover was low in naturally formed pools, and our 10-cm depressions decreased its cover by approximately 30% compared to the controls. S. bigelovii grew taller and produced more flowers in waterlogged sites with low soil redox potential, and it completed its life cycle in the 5-cm-deep depressions that we created. Experimentally reducing S. virginica canopy cover in shallow depressions also increased the survival of the annual. In the greenhouse, rhizosphere oxidation was indicated as a mechanism for tolerating waterlogging, as S. bigelovii elevated the soil redox potential by 50 mV more than S. virginica did. Also, in the greenhouse, S. bigelovii seedlings actually suppressed the growth of S. virginica seedlings under increased flooding. We conclude that waterlogged microsites help sustain S. bigelovii in Californian salt marshes and that this increasingly rare plant could be managed by adding shallow depressions to restoration sites.

1. Restoration of salt marshes on previously reclaimed land provides an excellent opportunity to study plant colonization and subsequent development of salt-marsh vegetation. Insight into the process of salt-marsh development can guide the design, implementation and evaluation of salt-marsh restoration schemes and help determine appropriate management strategies. 2. We evaluated the process of salt-marsh restoration at a species- and plant-community level and investigated how the sequence of species establishment is related to site suitability, availability of the target species in the local and regional species pools and dispersal traits. 3. It took approximately 5 years for species diversity in the restoration site to become similar to a local reference marsh. The annual species Salicornia spp. and Suaeda maritima colonized and reached maximum abundance first. Perennial species (Puccinellia maritima, Aster tripolium, Spartina anglica, Spergularia media, Atriplex portulacoides and Limonium vulgare) only started to colonize or increase notably in abundance after 3 years of restoration. 4. Plant composition at the highest elevation of the restoration site developed from an annual Salicornia community into a Puccinellia maritima salt marsh, which was similar to the local reference marsh. After 8 years, the lower elevations were still covered by annual Salicornia salt marsh despite the potential for the development of a Puccinellia community. 5. Salt tolerance appeared to be much more important in explaining the sequence of species establishment than the availability of the species in the local or regional species pools or dispersal traits. 6. Synthesis and applications. The prospect of salt-marsh restoration after de-embankment is good, with target species establishing spontaneously and vegetation succession taking place. Because most salt-marsh species are dispersed over short distances, it is important that a well-developed salt marsh is adjacent to the restoration site. The rate of salt-marsh development and species diversity appears to be affected mainly by surface elevation. Proper elevation in relation to tidal inundation is therefore a prerequisite for the successful restoration of salt-marsh vegetation after de-embankment.

In marine wetlands, nitrogen fixation is a potentially important nutrient source for nitrogen-limited primary producers, but interactions between nitrogen fixers and different vascular plant species are not fully understood. Nitrogen fixation activity was compared in sediments vegetated by three plant species, Spartina foliosa, Salicornia virginica, and Salicornia bigelovii in the Kendall Frost Reserve salt marsh in Mission Bay (CA). This study addressed the effects of plant type, day and night conditions, and sediment depths on nitrogen fixation. Higher rates of nitrogen fixation were associated with S. foliosa than with either of the two Salicornia spp., which are known to compete more effectively than Spartina for exogenous nitrogen in the salt marsh environment. Rates of nitrogen fixation, determined by acetylene reduction, in sediments vegetated by S. virginica were low during the day (7.7 ± 1.2 μmol C2H4 m−2 h−1) but averaged 13 ± 6.6 μmol C2H4 m−2 h−1 at night, with particularly high rates in samples from locations with visible cyanobacterial mats. The opposite diel pattern was found for sediments containing S. foliosa plants, in which average daytime and nighttime rates of nitrogen fixation were 62 ± 23 and 21 ± 15 μmol C2H4 m−2 h−1, respectively. For S. foliosa, nitrogenase activity of rinsed roots and different sediment sections (0–1, or 4–5 cm depths) were measured. Although nitrogen fixation rates in vegetated sediment samples were substantial, all but one of rinsed S. foliosa root samples (n = 12) and subsurface sediments at 4–5 cm depths failed to show nitrogen fixation activity after 2 h, suggesting that the most active nitrogen fixers in these systems likely reside in surface sediments. Further, nitrogenase activity in shaded and unshaded S. foliosa samples did not differ, suggesting that nitrogen fixers may not rapidly respond to changes in plant photosynthetic activity. Average nitrogen fixation rates in S. foliosa-vegetated samples from the Mission Bay salt marsh were on the same order as those of highly productive Atlantic coast marshes, and this microbially-mediated nitrogen source may be similarly substantial in other Mediterranean wetlands. Sediment abiotic variables seem to exert greater control upon nitrogen fixation activity than the effects of particular plant species. Nonetheless, dominant plant species may differ substantially in their reliance on nitrogen fixation as a nutrient source, with potentially important consequences for wetland conservation and restoration.

Ecological interactions often vary geographically. Work in salt marshes on the Atlantic Coast of the United States has documented community-wide latitudinal gradients in plant palatability and plant traits that may be driven in part by greater herbivore pressure at low latitudes. To determine if similar patterns exist elsewhere, we studied six taxa of saltmarsh plants (Atriplex, Juncus, Limonium, Salicornia, Spartina and Suaeda) at European sites at high (Germany and the Netherlands) and low (Portugal and Spain) latitudes. We conducted feeding assays using both native and non-native consumers, and documented patterns of herbivore damage in the field. As in the United States, high-latitude plants tended to be more palatable than low-latitude plants when offered to consumers in paired feeding assays in the laboratory, although assays with grasshopper consumers were less consistent than those with crab consumers, and plants in the field at low-latitude sites tended to experience greater levels of herbivore pressure than plants at high-latitude sites. Similarly, high-latitude leaf litter was more palatable than litter from low-latitude plants when offered to consumers in paired feeding assays in the laboratory. Latitudinal gradients in plant palatability and herbivore pressure may be a general phenomenon, and may contribute to latitudinal gradients in decomposition processes.

In salt-marshes, bulk carbon isotope values reflect organic matter contributions not only from salt-marsh plants, but also from algal and bacterial inputs, as well as allochthonous terrestrial organic matter. In the present study, compound specific isotope analysis was applied to a core and modern plant samples collected from a Machiasport, Maine salt-marsh. We sampled 10 plant species common to the marsh including Spartina alterniflora, Spartina patens, Juncus gerardi, Solidago sempervirens, Salicornia europa, Potentilla anserina, Atriplex patula, Plantago maritima, Suaeda maritima and Limonium nashii. Isolation of two n-alkanes (C27 and C29) present in marsh plant samples allowed for the reconstruction of past plant communities present in the cored deposits. For the C27 and C29 homologues there is a 3–10‰ separation in carbon isotopic composition between C3 and C4 species. Carbon isotopic values down core show a transition from a C4 dominated plant community to a C3 dominated community, attributable to the migration of lower marsh zones onto brackish/freshwater marsh zones during a late Holocene relative sea-level rise. The two homologues used have the potential to provide paleoenvironmental information in future core work, where the sea-level variable will be controlled.