Salt Marsh Communities Research Articles

Estuarine oiling increases a long-term decline in mussel growth

The ribbed mussel, Geukensia granosissima, cycles nutrients, contributes to soil stability, and can be a major component of predator-prey communities in salt marshes. Mussels were exposed to the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, and salt marshes remain contaminated eight years later. We hypothesized that the oiled mussels had reduced annual growth, altered population size frequency, and perhaps changed valve morphometrics. We sampled 10 marshes near Port Sulphur, LA, to measure the morphometrics of 133 mussels and their age-specific growth rate, and also the marsh oil content and percent vegetative cover. The relationships between valve weight, length and biomass weight were stable as mussels aged. A Year 1 growth decline from 1994 to 2018 is not easily explained by estuarine acidification, flooding, and temperature rise; freshening of estuarine waters is suggested to be a probable causal factor in the declining growth rate. The average valve length and dry biomass per valve declined with oiling in 2010. A multiple regression equation using the percent cover and oil concentration in 2018 described 70% of the variation in valve length. Sites with the highest oiling had few mussels with 14 annual growth bands and more of the younger mussels compared to sites with the lowest oiling. Valve growth in Year 1 declined for four years after the oil spill and was not compensated by higher growth rates in older mussels. Annual growth was below the amount predicted in a regression equation for the five years after the oil spill. Mussel populations may also have been structured by predators that were also responsive to oiling in subtle ways.

Growth and Survivorship of Red Mangrove Seedlings Under a Mangrove Canopy and in a Saltmarsh Community in Northeastern Florida

• In northeastern Florida, the red mangrove has established in saltmarsh communities. • Seedling growth was compared between saltmarsh and mangrove microhabitats. • Temperatures at the sediment surface were similar between microhabitats. • Inundation was greatest during storm events and high tides. • Greater growth in the Spartina microhabitat was likely due to significantly greater light availability. • Shaded conditions in under the mangrove canopy likely limited growth. In the United States, Rhizophora mangle L. populations have established in saltmarsh communities at the northern extent of its range in Guana Tolomata Matanzas National Estuarine Research Reserve, near St. Augustine, FL. This two-year study monitored the growth and survivorship of propagules planted in the intertidal band dominated by Spartina alterniflora Loisel and mangroves. Propagules in the S. alterniflora microhabitat grew more than twice as fast, had a greater number of leaves per plant, and produced more sets of branches and flower buds than those growing under the mangrove canopy. Differences in growth were likely due to the 2.7 times greater mean monthly insolation in the Spartina microhabitat during the spring-summer growing season. Individuals persisted beneath the mangrove canopy and may take advantage of increased light availability from canopy gaps created by extreme storm events. Despite the 67% mortality from herbivory, wind gusts, storm surge, and extreme high tides, surviving R. mangle seedlings reached maturity in the unshaded and warmer microclimate of the low-lying saltmarsh vegetation. Spartina alterniflora may serve as a facilitator during the cotyledon phase of R. mangle and did not inhibit the success of the seedling establishment, providing a mechanism by which dispersed R. mangle propagules may spread northward into saltmarsh communities.

The Effect of Sea Level Rise on Dabbling Duck Energetic Carrying Capacity

ABSTRACTWaterfowl migrating and overwintering in the Atlantic Flyway depend on adequate availability of wetland plant communities to survive winter and fuel reproduction in the subsequent breeding season. Energetics models are the primary tool employed by conservation planners to estimate energetic carrying capacity based on energy supply and demand in different wetlands to assist with effective habitat conservation. Coastal impoundments have been used to provide a consistent, annual source of energy for migrating and wintering waterfowl. But few studies have attempted to comprehensively assess the relative value of managed coastal impoundments compared with unmanaged tidal salt marshes to wintering waterfowl in the Mid‐Atlantic region with further consideration to the effect of sea level rise changing availability. We estimated biomass and energy of preferred foods for 5 dabbling duck species in 7 impoundments and 3 tidal salt marshes over winter by collecting soil core (n = 1,364), nekton (n = 426), and salt marsh snail (Melampus spp.; n = 87) samples in October, January, and April 2011–2013. Food‐energy density was greater in freshwater impoundments for nearly all dabbling ducks (range = 183,344–562,089 kcal/ha), and typically greater in brackish impoundments (range = 169,665–357,160 kcal/ha) than most tidal salt marsh communities (range = 55,693–361,429 kcal/ha), whereas mudflat (range = 96,223–137,473 kcal/ha) and subtidal (range = 55,693–136,326 kcal/ha) communities typically contained the least energy. Extrapolating to the state level, we estimated 7.60 × 109–1.14 × 1010 kcal available within a 16‐km buffer from the Delaware Bayshore, depending on species. Combining estimates for daily energy expenditure and food energy, we estimated 2.86 × 107–7.06 × 107 duck energy days currently available to dabbling ducks over winter. We estimated that in the next century, dabbling duck carrying capacities are likely to decrease under all but the most conservative sea level rise scenarios because of the gradual replacement of land‐cover types that provide high energy density (i.e., low marsh, high marsh communities) with those that provide low energy density (i.e., subtidal, mudflat communities). Coastal impoundments in Delaware, USA, will provide increasingly important habitat for wintering dabbling ducks in the coming decades provided they are properly maintained and retain their current energetic density because they will contain a growing proportion of the available duck energy days on the landscape. Our research will assist managers in meeting target population goals for dabbling ducks in Delaware and the Mid‐Atlantic region by highlighting key differences in the function and value of various wetlands. © 2021 The Wildlife Society.

Freshwater input drives invasion success of exotic plants in saltmarsh communities

AbstractWhile saltmarsh communities are endangered in many parts of the world due to anthropogenic impact, the risk of invasion by exotic plants is considered to be low because of their saline conditions. However, in urban areas, saltmarshes receive high nutrient freshwater input through stormwater discharge. We tested if invasion of saltmarsh by exotic plant species was facilitated by increased nutrients and reduced salinity associated with urban stormwater input. In a manipulative glasshouse experiment, we grew saltmarsh communities under four treatments: high salinity–low nutrients (control), high salinity–high nutrients, low salinity–low nutrients and low salinity–high nutrients. We then invaded the saltmarsh communities with four common invasive exotic plants. Their survival rates were monitored weekly for seven weeks before final harvesting. All exotic species showed significantly higher survival in the ‘low salinity’ treatment compared to the ‘high salinity’ treatment. There was variability among species, with three of four having low survival rates (0–3%) under ‘high salinity’ conditions, while survival of Protasparagus aethiopicus was reduced to only 53–59%. Our findings suggest that under natural conditions of saltmarshes, the establishment of exotic plant seedlings is restricted. Additional freshwater increased the survival of invading exotic species significantly, whereas adding nutrients increased biomass production but not necessarily survival of exotics. However, the results can be highly species dependant as shown by the unexpected salinity tolerance of P. aethiopicus. Reduction in salinity of saltmarsh due to stormwater input facilitates invasion by exotic plant species that would otherwise be unable to tolerate the highly saline environment.

Climate Change Impacts on Salt Marsh Blue Carbon, Nitrogen and Phosphorous Stocks and Ecosystem Services

Salt marshes are valuable ecosystems, as they provide food, shelter, and important nursery areas for fish and macroinvertebrates, and a wide variety of ecosystem services for human populations. These ecosystem services heavily rely on the floristic composition of the salt marshes with different species conferring different service values and different adaptation and resilience capacities towards ecosystem stressors. Blue carbon, nitrogen, and phosphorous stocks are no exception to this, and rely on the interspecific differences in the primary production metabolism and physiological traits. Furthermore, these intrinsic physiological characteristics also modulate the species response to any environmental stressor, such as the ones derived from ongoing global changes. This will heavily shape transitional ecosystem services, with significant changes of the ecosystem value of the salt marshes in terms of cultural, provisioning, regulating, and supporting ecosystem services, with a special emphasis on the possible alterations of the blue carbon, nitrogen, and phosphorous stocks retained in these key environments. Thus, the need to integrate plant physiological characteristics and feedbacks towards the expected climate change-driven stressors becomes evident to accurately estimate the ecosystem services of the salt marsh community, and transfer these fundamental services into economic assets, for a fluid communication of the ecosystems value to stakeholders, decision and policy makers, and environmental management entities.

Plant response to fungal root endophytes varies by host genotype in the foundation species Spartina alterniflora.

Root-associated fungi provide a wide range of functions for their host plants, including nutrient provisioning, pathogen protection, and stress alleviation. In so doing, they can markedly influence host-plant structural and physiological traits, although the degree to which these effects vary within particular plant host species is not well understood. We conducted a 7-month common-garden inoculation experiment to test the potential effects of a marine fungus (Lulwoana sp.) on the phenotypic traits of different genotypes of the host, the salt marsh plant species Spartina alterniflora. Lulwoana belongs to the dark septate endophytes (DSE), a polyphyletic group of fungi that are commonly found colonizing healthy plant roots, though their ecological role remains unclear. We documented significant impacts of Lulwoana on S. alterniflora morphology, biomass, and biomass allocation. For most traits in our study, these impacts varied significantly in direction and/or magnitude across S. alterniflora genotypes. Effects that were consistent across genotype were generally negative. Plant response was not predicted by the percentage of roots colonized, consistent with findings that dark septate endophytes do not necessarily influence plant growth responses through direct contact with roots. The observed changes in stem height, biomass, and biomass allocation have important effects on plant competitive ability, growth, and fitness, suggesting that plant-fungal interactions have community and ecosystem level effects in salt marshes.

Saltmarsh rhizosphere fungal communities vary by sediment type and dominant plant species cover in Nova Scotia, Canada.

We surveyed Spartina saltmarsh sediment rhizosphere fungal communities at three saltmarshes and two timepoints in coastal Nova Scotia. Based on ITS2 Illumina miSeq rDNA data and multivariate analysis, neither sediment zone nor collection period correlated with fungal ASV richness, but collection site did. However, Shannon diversity indicated that sediment zone played a significant role in fungal diversity. For unweighted and weighted UniFrac distance, site was the major factor driving beta-diversity, with sediment zone and collection period having smaller roles. Sediment type and saltmarsh plant species may play important roles in structuring rhizosphere fungal assemblages, here dominated by ascomycetes. To our knowledge, our study is the first to assess fungal sediment communities in saltmarshes in Atlantic Canada using metabarcoding. It provides a biodiversity analysis of sediment fungi in a poorly studied but highly important ecosystem and points to their roles in nutrient cycling, blue carbon, coastal stability and coastal restoration. Our work will inform ongoing saltmarsh restoration in Atlantic Canada.

Halophile wheatgrass Thinopyrum elongatum (Host) D.R. Dewey (Poaceae) in three Apulian coastal wetlands: vegetation survey and genetic diversity

Three Apulian (SE Italy) coastal sites, Torre Canne to Torre San Leonardo (T), Punta della Contessa Salt Pans (S) and the La Vela Swamp (P), characterised by sandy shores and salt marshes recognised as wetland environments belonging to the Natura 2000 network, were selected as study areas in order to survey the vegetation zonation, plant communities, ecological context and genetic diversity of Thinopyrum elongatum population within humid habitats. Analysis of vegetation, plant communities and soil samplings were carried out to investigate the ecological context of 24 populations collected of this halophile wheatgrass, along with biochemical characterization (A-PAGE, SDS-PAGE, and IEFxSDS-PAGE) of seed storage proteins, used to assess the genetic diversity intra- and inter-populations and genotype frequencies. Thinopyrum elongatum populations showed a significative presence in the halophile shrub plant communities of salt marshes, especially those characterised by Limbarda crithmoides and Artemisia caerulescens. The differences of the protein patterns, suggest the presence in the T area of a higher genetic variability and a greater resistance to the numerous factors of human pressure. The results have been discussed hypothesizing that this multidisciplinary approach could be considered a model to evaluate in the future the same environments or other similar ones, subjected to anthropogenic pressures and environmental changes.

Small-scale variation in herbivore abundance and grazing on Juncus roemerianus dominated salt marshes

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., < 2 km) within a single geographic region as well as the potential driving forces for such variability. Here we quantify the small-scale spatial variablity in insect grazing on three Juncus roemerianus marshes in Grand Bay National Estuarine Research Reserve, MS, USA. Sampling covered both monthly and seasonal temporal scales (February to November) to capture the well described seasonality in insect grazing in these marshes Our results show large differences in abundance of insect herbivores and intensity of herbivory across, but not within, the three marshes. In addition, the observed spatial differences in herbivory do not appear to be related to herbivore abundance or insect species, but potentially to differences in landscape context, such as proximity to upland habitats (i.e., forestland) or habitat fragmentation. These results demonstrate that insect herbivory in marshes can also vary substantially at small spatial scales and we suggest some mechanisms responsible for such differences.

Spatial and temporal patterns of initial plant establishment in salt marsh communities

AbstractQuestionsHow are dispersal processes, abiotic and biotic interactions determining the initial salt marsh plant community establishment and development when connectivity is different? We aim to answer this question by analysing the spatial and temporal patterns of plant establishment along an environmental gradient at two connectivity settings.LocationBack‐barrier salt marsh and tidal flats of Spiekeroog, northwest Germany.MethodsWe established an experiment along a saltmarsh elevation gradient with bare sediment open for spontaneous colonisation on the natural salt marsh and on the experimental salt marsh islands built on the tidal flats approximately 500 m from the natural salt marsh for low connectivity. Plant establishment was identified from georeferenced photos at least monthly.ResultsExperimental islands as low‐connectivity plots had limited colonisation by annual halophytes that produced large number of small seeds. Number of individuals increased with higher connectivity at patches enclosed by salt marsh. Number of individuals was highest at the mid elevations whereas peak species richness was at the upper salt marsh. Temporal patterns of seedling emergence showed increasing plant numbers until the end of April followed by a gradual decline over the season at the pioneer and lower salt marsh zones. Upper elevations on the other hand had a stable number of low individual counts over time. Spatial clustering of plant individuals indicating possible facilitation was important at the initial stages of salt marsh development at pioneer and lower salt marsh elevation, but only early in the season.ConclusionsStochastic patterns of early salt marsh colonisation indicated that success of species colonisation was determined by seed properties, seed availability and environmental conditions mediated by elevation. We found indications that at the initial stages, further colonisation was supported by already colonised plants but shifted to avoidance later in the season.

The intertidal plant communities in north‐eastern Australia, their carbon stores and vulnerability to extreme climate events

Abstract During the strong El Niño event of 2015–2016 large‐scale dieback of mangrove forests was observed in the Gulf of Carpentaria region of northern Australia. These and other intertidal communities are also extensive along the 7,400 km coastline of north‐eastern Australia. Determination of their floristic composition, potential carbon (C) store and sequestration capacity, and vulnerability to climate extremes is required for their effective conservation management and was the aim of this study. Standardized, state‐wide quantitative classification methods identified five mangrove forest and three saltmarsh communities covering 2,604 km2 along this coastline. Estuarine and oceanic mangrove forests were mapped separately. Carbon storage and sequestration capacity of the intertidal communities and their vulnerability to strong El Niño events were estimated using published data and GIS analyses. An estimated potential 126.2 (± 27.3 SEM) Tg C and 8.3 (±0.4 SD) Tg C were stored in the mangrove forests and saltmarshes, respectively. Comparatively, the rainforests of the region stored an estimated equivalent amount of C but covered three times the area, and the most widespread woodlands (Eucalyptus tetrodonta) of the region stored an estimated 1.5 times the C but covered 16 times the area. The C stored in the intertidal communities was estimated as equivalent to 493.47 Tg of CO2, valued at AU$6.8 billion on the Australian carbon market in December 2018. Annual C sequestration potential was 0.18–0.34 Tg C/year, valued between AU$8.9 and $17 million. Approximately 360 ha of mangrove forest was estimated as lost because of dieback during the 2015–16 El Niño event. Three types of mangrove forest were identified as potentially vulnerable to dieback from El Niño‐driven climate events. This study highlights the national and global significance of these intertidal systems and our findings need to be incorporated in future conservation and development planning of northern Australia.

Environmental and Spatial Influences on Biogeography and Community Structure of Saltmarsh Benthic Diatoms

Benthic microalgae play important roles in energy flow and biogeochemistry of coastal ecosystems; however, factors influencing community composition remain largely unknown. Our purpose was to identify and compare spatial and environmental influences on benthic diatom biogeography at regional scales. In summer 2018, we sampled sediment at various spatial scales (0.0001–180 km) from five saltmarshes in South Carolina, USA, and characterized diatom assemblages using DNA metabarcoding. Twenty-three environmental variables from marsh sediments, adjacent creeks, and atmosphere were recorded. Multivariate analyses revealed that the saltmarsh communities were clearly distinct. Community dissimilarity was compared to both geographic distance and environmental differences to determine influences on community structure. Mantel tests and redundancy analysis revealed that spatial influences, in addition to several environmental factors (phosphate, grain size, sediment sorting, sediment moisture, and creek salinity), were significant. Variation partitioning revealed that 26% of community variation was explained by geographic distance alone, whereas 60% could be explained by combined spatial/environmental factors. In contrast, the independent explanatory power of individual environmental factors was negligible. Our findings suggest that spatially structured environmental variation mainly conditioned the saltmarsh diatom biogeography in this region. Dispersal limitation, as evinced by the large pure spatial effect and distance-decay pattern, was also important. Spatial effects were stronger relative to that previously observed in other microbial groups (marine bacteria and phytoplankton) and detected at finer spatial scales. Results support prior studies that suggest body size and dispersal mode are important drivers of metacommunity structure and therefore must be considered when studying aquatic microbial biogeography.

March of the mangroves: Drivers of encroachment into southern temperate saltmarsh

Tidal wetlands are experiencing climate change driven shifts in their community composition, distribution, and functions. Mangroves have expanded into saltmarshes where their ranges overlap on five continents. Yet questions remain about the spatial variability of climate change drivers and subsequent local ecological feedbacks on these distributional shifts. Along the southernmost range of mangroves, we studied shifts between Avicennia marina and threatened saltmarsh communities. We used semi-automated object based image analysis to classify wetlands in aerial imagery from 1970 to 2017. Saltmarsh coverage decreased at the expense of mangrove encroachment. Landward migration of saltmarsh was negligible. Unlike other mangrove-saltmarsh ecotone studies, neither changes in seasonal extreme temperatures nor sea level rise were associated with the observed transitions. Rather, mangrove encroachment correlated with increasing annual maximum temperature and was more extensive at sites with lower mean elevations, shorter mean distances to earliest known mangrove-saltmarsh boundary, and higher densities of tidal creeks. Accounting for local variation in mangrove encroachment is informative for managing the provision of desirable ecosystem services. As climate change impacts the southernmost mangrove-saltmarsh ecotone, areas with higher mean elevations and fewer tidal creeks could be prioritized to mitigate the loss of saltmarsh.

Freeze tolerance of poleward‐spreading mangrove species weakened by soil properties of resident salt marsh competitor

Abstract Increasing temperatures associated with climate change are shifting plant species to higher latitudes. Soil communities could aid the plants’ shift into novel areas by harbouring fewer soil‐borne antagonists or more mutualists that influence the fitness and stress tolerance of the shifting species. Alternatively, they could contain novel antagonists or fewer mutualists. Thus, soil communities could positively or negatively affect plant range expansion, particularly if they influence plants’ responses to climate, such as freeze tolerance, that feedback to affect expansion. We used the northward range expansion of the black mangrove, Avicennia germinans, into a system dominated by marsh cordgrass, Spartina alterniflora, in northern Florida, USA to study how the novel soil environment (i.e. S. alterniflora soil) affects mangrove fitness, susceptibility to cold stress and the colonization of mutualist fungi. We quantified abundance of root mutualistic fungi in mixed marsh‐mangrove habitat and conducted a laboratory experiment to test effects of steam‐sterilized and live soils from A. germinans and S. alterniflora on the growth, condition, fungal colonization and freeze tolerance of A. germinans seedlings. In the field, we found two times higher dark septate endophyte (DSE) colonization of A. germinans roots and three times higher fungal spore density in A. germinans soil compared to S. alterniflora roots and soil. In the laboratory experiment, seedlings in steamed S. alterniflora soil treatments had 50%–65% survival after freezing, compared to 0% survival in treatments with live S. alterniflora soil. A. germinans live soil mixed with S. alterniflora steamed soil yielded A. germinans roots with the highest DSE colonization and seedlings with greater shoot biomass and lower root:shoot ratios. S. alterniflora live soil lowered the freeze tolerance of A. germinans, decreased mangrove survival and depressed DSE colonization. Synthesis. S. alterniflora soil could impede A. germinans establishment in salt marsh communities. As climate warming gradually allows A. germinans to displace S. alterniflora, the rhizosphere could become increasingly hospitable to A. germinans. Our work suggests the soil community associated with resident species mediates climatic stressors to affect expansion success.

Accumulation and partitioning of metals and metalloids in the halophytic saltmarsh grass, saltwater couch, Sporobolus virginicus

Remnant endangered saltmarsh communities in Australia often occur in urbanised estuaries where industrial processes have contaminated sediments with metal(loid)s. Despite this issue, virtually nothing is known on local plant species exposure to metal contaminants, nor their ability to uptake and translocate metal(loid)s from contaminated estuarine sediment. In the current study, we assessed the accumulation and partitioning of the metal(loid)s Zn, Cu, Pb, Cd and Se in the dominant saltmarsh primary producer, Sporobolus virginicus, across three urbanised estuaries in NSW Australia. Lake Macquarie was the most contaminated estuary, while Sydney Olympic Park, Port Jackson exhibited intermediate metal(loid) loadings and Hunter Wetlands exhibited the lowest loadings among estuaries. Essential metals (Zn and Cu) were more mobile, with sediment:root bioconcentration factors (BCFs) greater than unity and translocation among plant organs greater than, or equal to, unity. Other metal(loid)s were less mobile, with BCFs equal to unity and translocation factors among organs much reduced. Despite these barriers to translocation, all metal(loid)s were accumulated to roots with dose, and further accumulative relationships between metal(loid)s in roots and culms, and culms and leaves, were evidenced (with the exception of Cu). Along with sediment metal(loid)s, increases in sediment pH predicted Cu uptake in roots and increases in soil organic matter predicted Se uptake in roots. Although significant positive linear relationships were observed between sediment metal(loid)s and plant organ metal(loid)s(withholding Cu), the variance explained was low to intermediate for most metal(loid)s suggesting employing S. virginicus as an accumulative bioindicator would be impractical.

Effect of nitrate supply on the facilitation between two salt-marsh plants (Suaeda salsa and Scirpus planiculmis)

Abstract Aims In estuarine salt-marshes, nitrate supply and soil salinity, which are known as two main environmental drivers, simultaneously affect the interspecific interactions between plant species. However, to date, their interactive effects on interspecific interactions have not been closely examined for salt-marsh plant species. Methods Juvenile plants of Suaeda salsa L. (Chenopodiaceae) and Scirpus planiculmis Fr. (Cyperaceae) were grown in rinsed river sand to conduct a greenhouse experiment with three treatment categories: interspecific interaction (mixed culture or monoculture), three salinity levels (1, 50 and 100 mmol L−1) and three nitrate levels (0.5, 5 and 10 mmol L−1). First, height and biomass of all plants were measured. Then, the growth data, relative interaction index and competitive important index of the two species were analyzed. Important Findings The interspecific interactions between S. salsa and S. planiculmis were facilitation across the salinity gradients. The promotion of S. salsa growth with high nitrate supply did not enhance the facilitative effect of the species, especially at low salinity. However, high nitrate supply significantly shifted the interspecific interactions of S. planiculmis from facilitation to competition at high salinity. Our results suggest that excessive nitrate application changes the prediction of the stress-gradient hypothesis along a salinity gradient, leading to collapse of the two species coexistence in the salt-marshes. These findings make a contribution to the understanding of how S. salsa and S. planiculmis, as well as salt-marsh communities, respond to the human modification of estuarine nutritional levels.

The effect of heavy metal contamination pre-conditioning in the heat stress tolerance of native and invasive Mediterranean halophytes

Abstract Salt marshes are worldwide recognized for their unique and important ecological role. According to the Intergovernmental Panel on Climatic Change (IPCC), the frequency and intensity of warming events will rise due to global changes. Halophyte plants, inhabiting salt marshes are known for being highly tolerant to various abiotic stresses, nonetheless, although it has been acknowledged that the tolerance response is species specific there could also be differences at the population level. The present work aims to determine if the life history of two halophytes (Halimione portulacoides and Spartina patens), namely in terms of contaminant exposure, influences inter-populational heat tolerance. For this purpose, individuals from both species collected at pristine and contaminated sites were exposed to normal and increased temperature conditions, and its physiological fitness evaluated throughout biochemical and biophysical analysis. The photobiological traits, pigment and fatty acid profiles and oxidative stress biomarkers analyses of warming treated individuals, indicate that chronic heavy metal pre-conditioning significantly influences the heat stress tolerance of the native halophyte plants. Halimione portulacoides individuals collected at heavy metal contaminated salt marsh appeared more tolerant to heat stress. On the other hand, the invasive S. patens from the pristine site showed higher tolerance to heat stress. Thus, the pre-conditioning influences the tolerance mechanisms can affect the way in which salt marsh communities will evolve in the future, possibly being different through salt marshes. The contaminated marsh can be more resilient to invasion than the non-contaminated marsh, since the native species has benefited from this pre-conditioning. Moreover, and from the ecophysiological point the set of biophysical and biochemical indicators were tested, show a high efficiency in describing the ecophysiological traits, both between species and populations, facing different pre-conditioning histories.

ФЛОРИСТИЧЕСКОЕ БОГАТСТВО И НАСЫЩЕННОСТЬ ПРИМОРСКИХ РАСТИТЕЛЬНЫХ СООБЩЕСТВ С ДОМИНИРОВАНИЕМ TRIGLOCHIN MARITIMA L. (JUNCAGINACEAE) НА ПОБЕРЕЖЬЕ СЕВЕРНЫХ МОРЕЙ

The article presents the results of studying of the floral richness and density of communities dominated by the circumboreal temperate Arctic species Triglochin maritima L. (fam. Juncaginaceae). On the tidal zone of the western coast of the White sea in the direction from the lowland to the level of the low tide the geobotanical descriptions of plant communities on the model transects were made. The ecological characteristics of habitats, including geomorphic shore type, wave exposure and the mechanical composition of the substrate were given. It is revealed that various indicators of the geomorphological structure of the coast of the Bay effect on the characteristics and features of the floristic richness and density in the saltmarsh communities in these biotopes

Elevated carbon dioxide and reduced salinity enhance mangrove seedling establishment in an artificial saltmarsh community.

The global phenomenon of mangrove encroachment into saltmarshes has been observed across five continents. It has been proposed that this encroachment is driven in part by rising atmospheric CO2 concentration and reduced salinity in saltmarshes resulting from rising sea levels enhancing the establishment success of mangrove seedlings. However, this theory is yet to be empirically tested at the community-level. In this study, we examined the effect of CO2 and salinity on seedling growth of two mangrove species, Aegiceras corniculatum and Avicennia marina, grown individually and in a model saltmarsh community in a glasshouse experiment. We found that the shoot (210%) and root (91%) biomass of the saltmarsh species was significantly greater under elevated CO2. As a result, both mangrove species experienced a stronger competitive effect from the saltmarsh species under elevated CO2. Nevertheless, A. marina seedlings produced on average 48% more biomass under elevated CO2 when grown in competition with the saltmarsh species. The seedlings tended to allocate this additional biomass to growing taller suggesting they were light limited. In contrast, A. corniculatum growth did not significantly differ between CO2 treatments. However, it had on average 36% greater growth under seawater salinity compared to hypersaline conditions. Avicennia marina seedlings were not affected by salinity. From these results, we suggest that although CO2 and salinity are not universal drivers determining saltmarsh-mangrove boundaries, it is likely that rising atmospheric CO2 concentration and reduced salinity associated with sea level rise will enhance the establishment success of mangrove seedlings in saltmarshes, which may facilitate mangrove encroachment in the future.

Relationships between Salt Marsh Vegetation and Surface Elevation in Coos Bay Estuary, Oregon

Salt marsh habitats support a diverse array of estuarine species but are vulnerable to increased inundation resulting from sea-level rise. In order to characterize relationships between vegetation and elevation and inform assessments of risk to salt marsh communities from projected sea-level rise, we collected vegetation and elevation data at 42 salt marsh sites in Coos Bay Estuary, Oregon. For 1-m2 plots along transects from the bayside edge to the upland, we recorded height and percent cover of all plant species present. We determined plot location and elevation at 1-m intervals with a Trimble Pathfinder Pro XRS differential GPS and TOPCON GTS223 Total Station for comparison with existing LiDAR. Cluster analysis distinguished six vegetation groups. Two low marsh groups (average elevation 1.74 and 1.91 m) were characterized by swampfire (Sarcocornia perennis) with an average height of 31 cm, and saltgrass (Distichlis spicata) with an average height of 22 cm. Plots in the high marsh groups had average elevations ranging from 2.21 to 2.57 m and were characterized by tufted hairgrass (Deschampsia cespitosa) and Oregon gumweed (Grindelia stricta var. stricta), with an average height of 50 cm and 43 cm, respectively. Mid-marsh groups (average elevations of 2.01 and 1.99 m) were dominated by Lyngbye's sedge (Carex lyngbyei) with an average height of 64 cm. The data collected along these transects allowed us to assess LiDAR elevation accuracy, identify sites where LiDAR data require correction, and provide species-specific height data for correction of LiDAR in areas of dense vegetation.