Salt Marsh Species Research Articles

Soil salinity and moisture gradients and plant zonation in Mediterranean salt marshes of Southeast Spain

For two years, we measured soil moisture, pH, salinity, and ion concentrations bimonthly from 55 vegetation plots in six Mediterranean salt marshes of SE Spain. Edaphic characteristics during dry and wet seasons were compared within six selected plant communities. The dominant species in each of these communities were Suaeda vera, Lygeum spartum, Limonium sp, Sarcocornia fruticosa, Halocnemum strobilaceum, and Arthrocnemum macrostachyum. Although soil salt concentrations were lower during the wet season, different patterns of temporal variation in total dissolved salts, sodium adsorption ratio, Cl−, Na+, K+, Ca2+, and Mg2+ were observed in the soils occupied by different plant communities. The variation patterns for SO 4 2− were the same in all plant communities. The Ca2+/Mg2+, Ca2+/Na+, and SO 4 2− /Cl− ratios increased during the wet season because of the more pronounced decrease in Cl−, Na+, and Mg2+ concentrations relative to Ca2+, and SO 4 2− . Canonical correspondence analysis (CCA) related the species distribution with certain soil conditions. The edaphic variables that best explained the data were maximum soil moisture, mean K+/Na+ ratio, mean Ca2+/Mg2+ ratio, maximum pH, and maximum K+. Two different environments were identified: dry salt marsh and wet salt marsh. to examine soil ionic gradients in these two environments, two further CCA were applied. The variables that best explained soil-vegetation relationships in the dry salt marsh were mean K+/Na+ ratio, mean Ca2+/Mg2+ ratio, maximum K+, and minimum Ca2+/Na+ ratio. Some representative dry salt marsh species were Lygeum spartum, Atriplex glauca, Suaeda vera, and Frankenia corymbosa. The variables explaining the data set in the wet salt marsh were maximum sodium adsorption ratio, maximum Mg2+ content, mean Ca2+ content, and mean Ca2+/Mg2+ ratio. Species such as Arthrocnemum macrostachyum, Sarcocornia fruticosa, Juncus maritimus, and Tamarix boveana were representative of this environment.

Renal anatomy in sparrows from different environments.

The renal anatomy of three species of sparrows, two from mesic areas, the House Sparrow (Passer domesticus) and Song Sparrow (Melospiza melodia), and one salt marsh species, the Savannah Sparrow (Passerculus sandwichensis) was examined. Electron microscopy was used to describe the ultrastructure of the nephron. In addition, stereology was used to quantify the volumes of cortex, medulla, and major vasculature of the kidneys, and the volumes and surface areas occupied by individual nephron components. There appeared to be no differences in the ultrastructural anatomy of the nephrons among the sparrows. Proximal tubules contained both narrow and wide intercellular spaces filled with interdigitations of the basolateral membrane. The thin limbs of Henle contained very wide intercellular spaces which were absent in the thick limbs of Henle. The distal tubule cells contained short, apical microvilli and infoldings of the basolateral membrane. In cross section, the medullary cones of all birds display an outer ring of thick limbs of Henle which surround an inner ring of collecting ducts, which in turn surround a central core of thin limbs of Henle. The Savannah Sparrow has a significantly higher volume of medulla compared to the two more mesic species. Within the cortex, the Savannah Sparrow also has a significantly higher volume of proximal tubules but a significantly lower volume of distal tubules than the other species. Within the medulla, the Savannah Sparrow has a significantly higher volume and surface area of capillaries, and a significantly higher surface area of thick limbs of Henle and collecting ducts than the mesic species. These data suggest that the salt marsh Savannah Sparrow has the renal morphology necessary to produce a more highly concentrated urine than the mesic zone species.

Similarity between seed banks and above‐ground vegetation along a salinity gradient

Abstract. Zonation of above‐ground vegetation often occurs in salt marshes along salinity and moisture gradients. The above‐ground vegetation and seed bank in four physiognomically different vegetation zones in a salt marsh were compared to determine their level of similarity using percent similarity as a distance measure. 10‐m transects were established along a salinity gradient through four different vegetation zones; a Salicornia zone, a Salicornia‐Atriplex zone, an Atriplex zone and an Atriplex‐Hordeum zone. A UPGMA cluster analysis demonstrated that the above‐ground vegetation was not usually highly correlated with the seed bank composition of zonal communities. Since seeds of these annual salt marsh species occurred in all zones, the levels of salt stress may be the main factor determining which species were found in the above‐ground vegetation.

Structure and status of the intertidal wetlands of the Knysna Estuary

The intertidal wetlands of the Knysna Estuary cover an area of 1000 hectares and are important both to the ecology of the estuary as well as to the tourism-orientated economy of Knysna. Little research, however, has been conducted on these wetlands. The aim of this research was to investigate the floristic structure of the wetlands in relation to both the salinity and inundation gradients that typify an estuary. An herbarium of 54 species was collected of which 27 were saltmarsh or estuarine species. A vegetation map was compiled illustrating that the lower and middle reaches of the estuary were dominated by succulent, herbaceous saltmarsh species while the upper reaches were estuarine and dominated by reeds and rushes. The structure of the communities in the low and middle reaches was determined primarily by the regular tidal inundation patterns experienced by the marshes while in the upper reaches it was the infrequent tidal inundation, coupled with the presence of a large brackish water body adjacent to the marsh, that determined the community structure here. A qualitative assessment of anthropogenic impacts on the wetlands is also made.

The Effects of Temperature and Seasonal Change on the Germination of Two Salt Marsh Species, Atriplex prostrata and Salicornia europaea, along a Salinity Gradient.

The purpose of this study was to determine whether seasonal temperature changes interact with salinity concentration to inhibit germination. Flooding of a marsh may also influence the size of the seed bank. Soil cores (6.0 cm diameterx7.5 cm deep) were collected from four salt marsh zones in Rittman, Ohio. Salt was most concentrated at the innermost zone, which contained almost exclusively Salicornia europaea, and least concentrated at the outermost zone, which contained mainly Hordeum jubatum and Atriplex prostrata. Soil cores were collected during April, June, and October 1996 and were placed in temperature treatments of 5 degrees /15 degrees C, 5 degrees /25 degrees C, 15 degrees /25 degrees C, and 25 degrees /35 degrees C (dark/light). Seeds were germinated for 8-10 wk, and the seeds that did not germinate were counted from a 2.2-cm-diameter subsample. Results demonstrated that for both S. europaea and A. prostrata, the total number of seeds that germinated decreased throughout the growing season. The number of ungerminated seeds decreased throughout the year for A. prostrata, but for S. europaea, the number of ungerminated seeds increased from April to June and then decreased from June to October. For both species, the ratio of germinated to total seeds decreased from April to June and increased from June to October. Over the growing season and in all salinity zones, the 5 degrees /25 degrees C temperature treatment was the most stimulatory to seed germination. We suspect that a flooding event in June that killed the standing vegetation may have reduced soil salinity and allowed more seeds than usual to germinate, thus effectively eliminating the S. europaea seed bank. Thus, seed banks play a significant role in these salt marsh habitats by providing a new source of seeds for the establishment of later cohorts after flooding or salt stress eliminates an early cohort of seedlings.

Rehabilitation of Saline Wetland, Olympics 2000 Site, Sydney (Australia)—II: Saltmarsh Transplantation Trials and Application

The New South Wales Olympic Co-ordination Authority, which is responsible for the redevelopment of the site for the Olympic Games 2000, Sydney, is committed to the rehabilitation of the remnant ecosystems remaining on the site. This paper describes a 3-year saltmarsh transplantation project, and resulting management approaches for the rehabilitation of other saline wetland areas on the site. Two series of cuttings (spring and autumn) were made, including three dominant species and three species rare in Sydney. It was found that all the species could be propagated without difficulty, but field survival and growth were much higher for the spring series than the autumn one. Measurement was also made of the colonisation of mangrove and saltmarsh species that occurred at the site over the course of the trials. New understandings of estuarine wetland colonisation have emerged, and the information has been used to develop methods of transplantation for other parts of the Olympic site, and to define management needs for monitoring success.

Gas Exchange and Chlorophyll Fluorescence of C3 and C4 Saltmarsh Species

Spartina maritima (Curtis) Fernald, Spartina densiflora Brong, Arthrocnemum perenne (Miller) Moss, and Arthrocnemum fruticosum (L.) Moq are very frequent halophytes on the coasts of SW Europe. The first two are perennial Gramineae with C4 metabolism; the last two are perennial Chenopodiaceae with C3 metabolism. Controlled garden experiments were carried out with the four species to compare their physiological response, i.e., water potential (Ψ), net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), and chlorophyll fluorescence of photosystem (PS) 2 under saline and non-saline conditions. S. maritima behaves as an osmoconformer species, the other three as osmoregulators. In the four species, PN, E, and gs improved following freshwater irrigation. The variations in PN might be related with biochemical changes (which appear not to affect PS2), but not with significant stomatal fluctuations, which are associated with a lower water use efficiency in the case of Arthrocnemum. The species were segregated into two groups (not depending on their C3 or C4 photosynthetic pathway), in relation with the topographic level of this species in natural conditions: the relative responses of PN in S. maritima and A. perenne were lower than those of S. densiflora and A. fruticosum. The salt-tolerance index supports such segregation. S. densiflora demonstrated the best competitive possibilities against salt-tolerant glycophytes, with its more flexible response in saline or brackish environments, which explains its spreading along the rivers draining into the estuaries of the SW Iberian Peninsula.

Halophytes for the treatment of saline aquaculture effluent

We determined the feasibility of using salt-tolerant plants (halophytes) as biofilters to remove nutrients from saline aquaculture wastewater. Suaeda esteroa, Salicornia bigelovii and Atriplex barclayana (Chenopodiaceae), species with potential as forage and oil seed crops, were grown in sand in draining containers (lysimeters) in a greenhouse experiment. They were irrigated to meet evapotranspiration demand and to produce a 0.3 leaching fraction, using aquaculture effluent generated from an intensive tilapia culture system. The effluent salinity was increased with NaCl to make salinity treatments of 0.5, 10 and 35 ppt. The plant–soil system removed 98% and 94% of the applied total and inorganic nitrogen, respectively. It removed 99% and 97% of the applied total and soluble reactive phosphorus, respectively. High removal rates occurred despite the high leaching fraction. Salt inhibited ( P<0.05) the growth rate, nutrient removal, and volume of water that all three plant species could process. Suaeda and Salicornia, which are succulent salt marsh species, performed better than the desert saltbush, Atriplex, at the higher salinities.

A Paleoecological Assessment of Phragmites australis in New England Tidal Marshes: Changes in Plant Community Structure During the Last Few Millennia

Although Phragmites has been an upper border tidal marsh species for thousands of years, it is only recently (within the last century or so) that the distribution of this plant within the coastal marsh community has become prominent. Prior to approximately 100 years ago, Phragmites was an upper border/brackish marsh co-dominant in many marsh systems. Occurrence of this species varied between associations of sedges, Typha, forbs and a variety of woody shrubs. Paleoreconstructions rarely show the presence of a Phragmites monoculture or early associations with salt marsh species. However, since the turn of this century (and perhaps as early as the middle of the last century) the distribution of Phragmites has changed substantially. Today, this plant often forms dense monocultures and is commonly found in association with Spartina grasses. The results of this paleoecological investigation show that the changes that have been observed in Phragmites communities during the last 100 years are not part of the long-term cycle of development in these systems and are new to the landscape.

Effect of Improved Tidal Flushing and Competitive Interactions at the Boundary between Salt Marsh and Pasture

Zonation of salt marsh plants has been widely recognized and studied, but the boundary between salt marsh and adjacent upland plants has seldom been considered. Three hypotheses about the boundary between salt marsh and adjacent upland pasture were tested on Kooragang Island, New South Wales, Australia. First, we hypothesized that increased tidal range resulting from removal of culverts that restricted tidal flow to areas of salt marsh would lead to landward spread of salt marsh into areas previously dominated by pasture. Monitoring results showed an increase in areal cover by salt marsh plants and a decrease in pasture plants along the boundary between salt marsh and pasture in areas affected by culvert removal, while no change could be detected at a reference site unaffected by culvert removal. Second, we hypothesized that the down-gradient distribution of the pasture species Stenotaphrum secundatum (buffalo grass) was restricted by physical conditions, while the up-gradient distribution of the salt marsh species Sarcocornia quinqueflora (samphire) was restricted by competition with pasture species. Results of a reciprocal transplant experiment were consistent with this hypothesis. Third, we hypothesized that the rate of salt marsh spread following culvert removal would be influenced by competition with pasture species. Results of an experiment in which pasture was removed adjacent to a salt marsh affected by culvert removal were consistent with this hypothesis. Results may help guide management of over 1,300 structures that restrict tidal flow to estuarine wetland habitat in New South Wales, Australia.

ENCEPHALITIS IN A BOY FROM SOUTH CAROLINA

ENCEPHALITIS IN A BOY FROM SOUTH CAROLINA

The impact of red mud on growth of wetland vegetation and substrate fertility

Greenhouse experiments were conducted to evaluate the impact of “red mud”, the residue of the Bayer process for extracting alumina from bauxite, on wetland to investigate whether red mud can be used for wetland restoration. Two wetland species,Spartina alterniflora Loisel. andSagittaria lancifolia L., were used to test their response to the following substrate treatments: 100% marsh sediment, 100% red mud, a mixture of 50% marsh sediment and 50% red mud, a mixture of 50% red mud and 50% compost, and neutralized red mud. Each substrate treatment received two fertilization levels, fertilized (N−P−K) and unfertilized. Red mud could support the growth of the salt marsh species,Spartina alterniflora, but not the fresh marsh species.Sagittaria lancifolia. The high Na content and salinity of red mud, even when mixed with marsh sediment or compost, appeared to be the primary cause for the high mortality ofSagittaria in these substrates. Fertilization did not reduce the stress response ofSagittaria to red mud, but significantly increased the growth ofSpartina. Red mud is low in available N and P and required fertilizer or organic matter (e.g., compost) addition to increase fertility. In experiments with both fresh and salt marsh sediments, the concentrations of soluble heavy metals, with the exception of Mn, were not significantly greater for red mud than for marsh sediment. Thus, the release of heavy metals from red mud over the short-term may not pose an environmental concern. However, the mobilization of heavy metals over the long-term and the influence of plants in accumulating metals requires further investigation.

Effect of cement dust on three halophytic species of the Mediterranean salt marshes in Egypt : M. M. Migahid & S. M. El-Darier, Journal of Arid Environments, 30(3), 1995, pp 361–366

Effect of cement dust on three halophytic species of the Mediterranean salt marshes in Egypt : M. M. Migahid & S. M. El-Darier, Journal of Arid Environments, 30(3), 1995, pp 361–366

Effect of cement dust on three halophytic species of the Mediterranean salt marshes in Egypt

The present study was carried out on the halophytic species Salicornia fruticosa. Halocnemum strobilaceum and Arthrocnemum glaucum native to the Mediterranean salt marshes. Plant material were collected at a distance of 1, 3 and 5 km from an early constructed cement factory in the area. Washed cements from the surface area of study plants were found to be about 5·0, 1·7 and 1·0 μg cm−2 at the three locations respectively. Cement increased the mortality of young branches leading to a reduction in the height and cover of the three species, especially Arthrocnemum glaucum, which was most sensitive to the dust. Water content, relative water content and succulence were improved in the living parts of the three species. A considerable increase in proline was found in Arthrocnemum glaucum and in soluble carbohydrate for the other two species.

The response of Aster tripolium and Puccinellia maritima to atmospheric carbon dioxide enrichment and their interactions with flooding and salinity

The effects of 380 and 720 μmol mol −1 atmospheric CO 2 on growth, dry matter allocation, net leaf photosynthesis and stomatal conductance of the C 3 salt marsh species Aster tripolium L. and Puccinellia maritima (Hudson) Parl. were studied. Plants were grown in pots under combinations of low (50–250 mM NaCl) or high (450–550 mM NaCl) salinity and non-flooded or flooded salt marsh soil. High salinity reduced growth of both species, while flooding increased biomass production of A. tripolium. Root weight of A. tripolium and total plant weight of P. maritima was increased by atmospheric CO 2 enrichment when the soil was flooded. Under non-flooded conditions, the effect of elevated CO 2 on growth was small ( P. maritima) or absent ( A. tripolium). The relative increase in total plant weight of both species by elevated CO 2 was higher under saline conditions. Dry matter allocation between root, stem and leaf, as reflected in leaf weight ratio and shoot to root ratio, was not changed by elevated CO 2, while specific leaf area was slightly decreased by CO 2 enrichment. Elevated CO 2 stimulated net leaf photosynthesis of both species, while stomatal conductance decreased. These effects were not changed by salinity or flooding treatment.

Disturbance of salt marsh vegetation by wrack mats in Great Sippewissett Marsh.

To quantify disturbance to salt marsh vegetation, and to test the notion that disturbance and species richness are related, we studied disturbance of vegetation by 195 wrack mats that had become stranded over Great Sippewissett Marsh. The mats varied in area, thickness, residence time, and elevation of stranding. Mats that were large, that had residence times of 3-4 months, and were stranded at higher elevations produced the most damage, ranging from total eradication to a decrease in shoot density of underlying vegatation. Thickness had no effect. About 70% of mats caused no damage, and of those that did, damage was usually 50% or less of the area beneath the mat. Plant species were differentially distributed along the tidal excursion within the marsh, and there were more species (8-9) high in the intertidal range than lower (4-6 species). Vertical distribution of species, species richness, and rate of annual disturbance were not well correlated, although highest and lowest disturbance rates corresponded to highest and lowest species richness. Most of the increases in species richness, however, occurred over a very small range of disturbance, so narrow that it seemed unlikely that disturbance affected richness. It seems more likely that factors other than disturbance rate control vertical position of species in salt marshes. It also appears that the effect of disturbance by wrack is less important than has been claimed.

Patterns in the Evolution of Physiological Specialization in Salt-Marsh Animals

Patterns of tolerance to stressful abiotic variables among animals that have colonized salt marshes provide models for the study of the evolution of physiological specialization. We provide an overview of some closely related pairs or groups of species that show hierarchical gradations in tolerance, and thereby physiological mechanisms of compensation, along a line perpendicular to the shore. However, a full understanding of the evolution of physiological specialization requires that we evaluate the role of abiotic factors in light of the biotic interactions in which salt-marsh species are embedded. The common occurrence of salt-marsh endemics in a species-poor environment must be related to the unusual character of this habitat, in which the reduced importance of some biotic forces is paired with highly stressful abiotic factors. The salt marsh is probably not a refuge for competitively inferior forms so much as it is a highly selective environment that admits only those specialized species that can muster the necessary physiological adaptations. Thus the apparently lower competitive ability of salt-marsh species under conditions that are not abiotically stressful is likely to be a secondary consequence of the costs of mechanisms conferring tolerance, and of life in a species-poor habitat. Salt marshes provide an arena in which it is possible to experimentally evaluate the evolutionary and ecological importance of abiotic stress, especially in relation to parapatric or allotopic distributions. Yet very few studies have provided such a rigorous approach, despite a long-standing recognition that abiotic factors interact strongly with biotic forces in the salt marsh.

Tidal Marsh Restoration: Trends in Vegetation Change Using a Geographical Information System (GIS)

AbstractAdequately evaluating the success of coastal tidal marsh restoration has lagged behind the actual practice of restoring tidally restricted salt marshes. A Spartina‐dominated valley marsh at Barn Island Wildlife Management Area, Stonington, Connecticut, was tidally restricted in 1946 and consequently converted mostly to Typha angustifolia. With the re‐introduction of tidal flooding in 1978, much of the marsh has reverted to Spartina alterniflora. Using a geographical information system (GIS), this study measures restoration success by the extent of geographical similarity between the vegetation of the restored marsh and the pre‐impounded marsh. Based on geographical comparisons among different hydrologic states, pre‐impounded (1946), impounded (1976), and restored (1988) tidal marsh restoration is a convergent process. Although salt marsh species currently dominate the restored system, the magnitude of actual agreement between the pre‐impounded vegetation and that of the restored marsh is only moderate. Further restoration of the salt marsh vegetation may be limited by continued tidal restriction, marsh surface subsidence, and reduced accretion rates. General trends of recovery are identified using a gradient approach and the geographic pattern’ of vegetation change. In the strictest sense, if restoration refers only to vegetation types that geographically replicate preexisting types, then only 28% of the marsh has been restored. Restoration in a broader sense, however, representing the original salt marsh vegetation regardless of spatial position, amounts to 63% restored. Unrestored marsh, dominated by Typha angustifolia and Phragmites australis, remains at 37%. By emphasizing trends during vegetation recovery, this evaluation technique aims to understand the restoration process, direct future research goals, and ultimately aid in future restoration projects.

Interactive effects of atmospheric CO2 enrichment, salinity and flooding on growth of C3 (Elymus athericus) and C4 (Spartina anglica) salt marsh species

Interactive effects of atmospheric CO2 enrichment, salinity and flooding on growth of C3 (Elymus athericus) and C4 (Spartina anglica) salt marsh species

Germination ecology of coastal plants in relation to salt environment

AbstractResponses of seed germination to salinity were examined using 37 species collected from salt marshes, cliffs, and fore (unstable) and hind (stable) sand dunes along Japanese coasts. For comparison, seed germination of nine inland species was also examined. The soil salinities in salt marshes ranged from 150 to 300 mmol/L NaCl, whereas those in fore and hind dunes ranged from 0 to 150 mmol/L NaCl, with a few exceptions. Cliff soils showed relatively high salinities up to 300 mmol/L NaCl. Ciff and foredune soils that encountered a typhoon and storm showed high salinities &gt;300 mmol/L NaCl. Salt tolerance in seed germination of coastal plants was ordered by comparing the responses of percentage and rate of germination to salinity conditions up to 200 mmol/L NaCl, being in the order of salt marsh&gt;cliff&gt;foredune≅hind dune≅inland. Thse results indicate that salt tolerance in seed germination of coastal plants is closely related to the salinity conditions of their habitats. Germination experiments under favorable conditions showed that a high percentage of the seeds of salt marsh species germinate rapidly, those of diff species germinate slowly and those of foredune species exhibit a low percentage and low rate of germination. It seems that these germination characteristics contribute to the success of germination at the ‘safe site’ and the subsequent survivorship of emerged plants in their natural habitats.