Australis Marsh Research Articles

Small-Scale Spatial Variability of Soil Methane Production Potential and Porewater Characteristics in an EstuarinePhragmites australisMarsh

ABSTRACT Tong, C.; Huang, J., and Jia, Y., 2015. Small-scale spatial variability of soil methane production potential and porewater characteristics in an estuarine Phragmites australis marsh. High temporal and spatial variability is a problem when quantifying methane flux from wetland soils. Spatial variability of methane production at the landscape scale has been investigated for different wetlands, but few studies have examined soil methane production at the small scale. Here, we investigated small-scale spatial patterns of soil methane production potentials and concentrations of porewater acetate, dissolved CO2, , , and soil dissolved organic carbon (DOC) in a brackish Phragmites australis marsh of the Min River estuary, southeast China. Sampling was performed for an area of 1.6 × 1.6 m to a depth of 30 cm (5-cm intervals) using a grid of 0.4 m resolution. Data were interpolated by an inverse distance moving average weighted method. Large differences in soil methane production potentials were detected ...

Plant effects on burrowing crab morphology in a Chinese salt marsh: Native vs. exotic plants

Burrowing crabs are conspicuous components of many salt marshes yet factors influencing burrow morphology have received little attention. We studied the effects of marsh plants on crab burrows and found significant variation of crab burrow morphology along a successional gradient from mudflat to vegetated marshes (either exotic Spartina alterniflora or native Phragmites australis marsh). Mudflat soil had lower water content, but higher bulk density than vegetated marshes. Burrows in vegetated marshes had more openings and branching and higher width–depth ratios, but smaller openings and lower depth, length, and total volume than on mudflats. S. alterniflora marshes had less rhizome biomass, but higher fine root biomass than P.australis marshes found at higher elevations, and burrows in S. alterniflora marshes were shallower, shorter, had smaller volumes, but had larger surface openings than P.australis marshes. Young S. alterniflora marshes had higher aboveground biomass, but lower stem density, rhizome and fine root biomass, and burrows were deeper, longer, and larger than in old S. alterniflora marshes. These data suggest that plant properties influence burrow morphologies and that burrow morphologies change during salt marsh succession due to changing root distributions and soil properties.

Incorporation of Exotic Spartina alterniflora into Diet of Deposit-Feeding Snails in the Yangtze River Estuary Salt Marsh: Stable Isotope and Fatty Acid Analyses

The response of deposit-feeding animals to plant invasions is still unclear, because their food sources are often difficult to identify. We examined the effect of the exotic plant species, Spartina alterniflora, on the food source composition of two dominant snail species, Assiminea latericea and Cerithidea largillierti, in the Yangtze River estuary salt marsh using a combination of stable isotope and fatty acid analyses. We collected the snails and their potential food materials (sediment organic matter, particulate organic matter, and plant material) in S. alterniflora and native plant Phragmites australis marshes and then determined the composition of food sources of snails based on fatty acid markers and stable isotope composition. Our results indicated that A. latericea and C. largillierti are deposit feeders grazing on sedimentary particles originating from diatoms, bacteria, and vascular plants. Invasive S. alterniflora did not result in a change in the relative contribution of microalgae, bacteria, and vascular plants to the food source of the snails. Spartina alterniflora was confirmed to be assimilated by both snail species. The higher assimilation of S. alterniflora by A. latericea compared with C. largillierti is probably related to the greater ability of A. latericea to assimilate plant materials from detritus, as evidenced by fatty acid composition. Overall, S. alterniflora can be incorporated into the food web of the estuarine salt marsh by the dominant snail species with generalist-feeding habits.

Temporal and vertical distribution of microphytobenthos biomass in mangrove sediments of Zhujiang (Pearl River) Estuary

Being a primary producer, Microphytobenthos (MPB) play an important role in the benthic ecosystem of mangrove swamps. The temporal and vertical distribution of MPB biomass, expressed as chlorophyll a (Chl a), was investigated in mangrove swamps on the Qi’ao island and the Futian Mangrove Nature Reserve, Guangdong Province, South China. Both locations are situated in the Zhujiang (Pearl River) Estuary. For each location, bi-monthly sampling was carried out at four sites during low tide period. Except one site on the Qi’ao Island, which was in Phragmites australis marsh, all sites were in mangrove swamps. The Chl a concentration in surface (0–1 cm) sediment ranged from 0.2 µg/cm3 to 8.3 µg/cm3 in the Qi’ao Island and from 2.1 µg/cm3 to 15.6 µg/cm3 in the Futian Mangrove Reserve. The peak Chl a concentration occurred in winter or early spring, while the lowest Chl a concentration, with a value of about one quarter of the peak, was observed in summer or early autumn. The vertical distribution of Chl a concentration exhibited an exponential decline with depth, which indicated a muddy sediment with high organic matter, and the slope of the curve was positively related to Chl a concentration in the surface sediment. The MPB biomass of the Qi’ao Island was significantly lower than that of the Futian Mangrove Reserve. Our results suggest that the overlaying water quality might influence the MPB biomass in surface sediments.

Water chemistry distinguishes wetland plant communities of the Great Lakes coast

U.S. coastal wetlands of the Laurentian Great Lakes span a north-to-south gradient (latitude 47–41° N) of increasing human population and agricultural intensity that alters their water chemistry and vegetation. We related field-measured water chemistry to vegetation condition and composition using data from 48 freshwater coastal wetlands along this sub-continental gradient, building upon previous findings that GIS-derived landscape descriptors could adequately predict vegetation condition in Great Lakes coastal wetlands. Our aim was to determine (1) whether plant communities could be differentiated by their surface water chemistry, and (2) if water chemistry could better predict wetland vegetation condition than GIS-derived variables. Seven distinct plant communities were identified by agglomerative hierarchical clustering and non-metric multidimensional scaling of vegetation cover data: Sphagnum-carpeted poor fens, Sparganium eurycarpum marshes, Calamagrostis canadensis wetlands, Schoenoplectus pungens marshes, Phragmites australis marshes, and two floristically distinct Typha-dominated marshes. There were significant differences (ANOVA) among the seven plant assemblages identified for most water chemistry metrics (Cl−, chlorophyll a, conductivity, NO3-N, pH, total N, total P, total suspended solids), but dissolved oxygen, dissolved organic carbon, and NH4-N did not vary significantly across the assemblages. The two different Typha-dominated plant communities were chemically distinct from each other in chlorophyll a, conductivity, NO3-N, pH and total suspended solids concentrations, and we recommend that they be separated into distinct associations: Typha spp. – Thelypteris palustris – Hydrocharis morsus-ranae and Typha spp. – C. canadensis – Leersia oryzoides. Plant communities tended to be geographically clustered, but wetlands that were geographic outliers of their floristic type were chemically similar to other wetlands in their plant community grouping despite being on different lakes. When offered both GIS-derived and field-measured potential predictor variables, a regression tree model of wetland condition chose only GIS-derived variables. However, a classification tree model derived solely from field-measured water chemistry variables correctly classified 79% of the sites into four plant community groupings based on total N, conductivity, and pH. Grouping wetlands by plant communities could provide a scientifically-defensible basis for stricter water quality standards to protect sensitive wetland types.

Spartina alterniflora invasion increases soil inorganic nitrogen pools through interactions with tidal subsidies in the Yangtze Estuary, China

Invasive alien plants increase both plant N and soil inorganic N pools in many terrestrial ecosystems. This is believed to be the result of altered plant-soil-microbe feedbacks that accelerate N cycling. However, it may also be due to the greater ability of invasive species to uptake lateral N subsidies that can modify ecosystem N dynamics. We conducted manipulative field experiments to determine the impact of smooth cordgrass (Spartina alterniflora) invasion on the N cycling of salt marsh ecosystems in the Yangtze Estuary, China. The results showed that the aboveground plant N and soil inorganic N pools in S. alterniflora marshes, 14.39 and 3.16 g N m(-2), were significantly higher than those in native common reed (Phragmites australis) marshes, 11.61 and 2.29 g N m(-2). These increases after invasion were explained by a significantly higher uptake of dissolved inorganic N (DIN) from tidal subsidies in S. alterniflora marshes (6.59 g N m(-2)) than from those in P. australis marshes (1.61 g N m(-2)), and not by soil organic N mineralization, which was not significantly different between S. alterniflora (6.45 g N m(-2)) and P. australis marshes (6.84 g N m(-2)) during the growing season. Our study indicated that the ecosystem engineering effects of S. alterniflora, which increases the interception of external N input, can be an alternative mechanism that increases plant N and soil inorganic N pools--especially in ecosystems with ample anthropogenic N subsidies, such as the coastal wetlands of China.

Impacts of Spartina alterniflora invasion on the benthic communities of salt marshes in the Yangtze Estuary, China

As a species for ecological engineering, Spartina alterniflora was introduced to Chongming Dongtan in 1995, and over the last 10 years, this species has rapidly invaded large areas of the Chongming Dongtan nature reserve. In this study, use of a normalized biomass size-spectra (NBSS) approach was explored to evaluate the possible impacts of S. alterniflora invasion on the benthic communities along gradients of intertidal zones and the invasion history of S. alterniflora within the nature reserve. The results showed that the characteristics of macrobenthic communities and the variation in macrobenthic communities described by the first two CCA axes revealed clearly the gradients of elevation and invasion history of S. alterniflora. The differences in the macrobenthic assemblages between the Spartina alterniflara marshes and the native Phragmites australis marshes decreased with increasing of invasion history of S. alterniflara. The macrobenthic biomass showed a decreasing trend, while the meiobenthic biomass showed a reverse trend along the elevation gradient. The macrobenthic biomass of S. alterniflora marshes with longer invasion history was higher than that at recently invaded S. alterniflora marshes, while the meiobenthic biomass was lower. The slopes of NBSS for the sampling sites showed a trend of steeper slopes with decreasing of elevation and at the recently invaded S. alterniflora marshes than that at marshes with longer invasion history, while the differences between the native P. australis marshes and the S. alterniflora marshes with long invasion history tended to be diminished. The NBSS approach could thus be used more widely to detect possible impacts of S. alterniflara invasion on benthic assemblages. This study also indicated the potential for this approach to provide valuable insights into the ecosystem ecology of invasive species, which could be very important for wetland biodiversity conservation and resource management in the Yangtze River Estuary and other such impacted areas.

Exotic Spartina alterniflora provides compatible habitats for native estuarine crab Sesarma dehaani in the Yangtze River estuary

Although the impact of plant invasions on benthic communities, especially burrowing crabs, has received increasing attention, the results from past studies are mixed. The exotic plant Spartina alterniflora has become the most abundant species in the salt marshes of the Yangtze River estuary since it was first found just over a decade ago, but its effects on crabs in the salt marshes is largely unknown. To examine whether the invasions of this exotic plant affected native crabs, we compared the biomass and abundance of the dominant burrowing crab Sesarma dehaani in an exotic Spartina marsh, native Phragmites australis marsh and mudflats of the Yangtze River estuary, China. To explain the differences of S. dehaani populations between different habitats, feeding preference of S. dehaani for Spartina and Phragmites was investigated. Results showed crab abundance and biomass in the Spartina marsh were significantly greater than those in the Phragmites marsh and mudflats. Soil water content and plant community characteristics in the Spartina marsh also significantly differed in the Phragmites marsh and mudflats. Moreover, the feeding preference experiment showed that crabs consumed Spartina more than twice as much as Phragmites. In summary, this study showed that Spartina provided compatible habitats for native crab S. dehaani through offering suitable food source and moderate environmental conditions.

Effects of Spartina alterniflora invasion on benthic nematode communities in the Yangtze Estuary

Invasions of exotic plant species in estuaries have occurred worldwide, and may pro- foundly affect native biodiversity and estuarine ecosystem functioning. To assess the effect of plant invasions on benthic meiofauna, we compared the nematode communities in marshes dominated, respectively, by invasive Spartina alterniflora and native Scirpus mariqueter and Phragmites australis at 3 local sites over 2 seasons in the Yangtze River estuary, PR China. S. alterniflora stands had gen- erally lower nematode trophic diversity than the stands of the 2 native plants, suggesting that the exotic plant led to a simplified benthic food web. The relative abundance of bacterial-feeding nema- todes tended to increase in S. alterniflora marshes compared to P. australis marshes. The increased bacterial-feeding nematodes in S. alterniflora stands are likely to reflect the altered decomposition processes, rates and pathways, which may, in turn, modify belowground nutrient cycling of the estu- arine ecosystems. The dissimilarity in nematode community structure between S. alterniflora and S. mariqueter marshes was smaller than that between S. alterniflora and P. australis marshes, and the dissimilarity between Spartina-invaded and native marshes was even smaller than between the 2 native plant marshes. It is suggested that the detection of the ecological consequences of plant inva- sions depends on which native plant species is considered. Site effects were generally detected in the comparison of sediment properties and nematodes among 3 plant marshes. Sediment water content, electrical conductivity, bacterial biomass and litter biomass were identified as the most important factors in the shaping of the nematode communities.

Salt tolerance and osmotic adjustment of Spartina alterniflora (Poaceae) and the invasive M haplotype of Phragmites australis (Poaceae) along a salinity gradient

An invasive variety of Phragmites australis (Poaceae, common reed), the M haplotype, has been implicated in the spread of this species into North American salt marshes that are normally dominated by the salt marsh grass Spartina alterniflora (Poaceae, smooth cordgrass). In some European marshes, on the other hand, Spartina spp. derived from S. alterniflora have spread into brackish P. australis marshes. In both cases, the non-native grass is thought to degrade the habitat value of the marsh for wildlife, and it is important to understand the physiological processes that lead to these species replacements. We compared the growth, salt tolerance, and osmotic adjustment of M haplotype P. australis and S. alterniflora along a salinity gradient in greenhouse experiments. Spartina alterniflora produced new biomass up to 0.6 M NaCl, whereas P. australis did not grow well above 0.2 M NaCl. The greater salt tolerance of S. alterniflora compared with P. australis was due to its ability to use Na(+) for osmotic adjustment in the shoots. On the other hand, at low salinities P. australis produced more shoots per gram of rhizome tissue than did S. alterniflora. This study illustrates how ecophysiological differences can shift the competitive advantage from one species to another along a stress gradient. Phragmites australis is spreading into North American coastal marshes that are experiencing reduced salinities, while Spartina spp. are spreading into northern European brackish marshes that are experiencing increased salinities as land use patterns change on the two continents.

Blocking Phragmites australis reinvasion of restored marshes using plants selected from wild populations and tissue culture

This study tested a vegetation strategy for controlling Phragmites australis invasion into brackish marshes as an alternative to the current technique of repeated herbicide sprays followed by burning. This strategy involves blocking P. australis by planting desired plants selected from wild populations and/or tissue culture regenerants at key points on the major routes of P. australis invasion. The planting of native species was conducted at three sites in a herbicide-treated P. australis marsh near Salem, NJ. Wild population selections of three upland marsh shrubs, Myrica cerifera, Baccharis halimifolia, and Iva frutescens, as well as two grass species, Spartina alterniflora and Spartina patens, and two rushes, Juncus gerardi and Juncus roemerianus, were planted according to their normal zonation positions. Tissue culture regenerated plants of the two grasses and two rushes, and the sedge species Scirpus robustus, were also planted. Plant growth at each site was monitored each year after planting for up to 3 years. Most plants of B. halimifolia, I. frutescens, J. roemerianus, and S. patens demonstrated a consistent vigorous growth at all three sites, whether or not the plants were collected from wild populations or were tissue culture regenerants. These multi-layered walls of plants demonstrated effectiveness in controlling the P. australis by restricting or inhibiting its spread. Upon screening 48 regenerated plants of S. patens at one of the three sites, we found that some regenerants showed enhanced characteristics for blocking P. australis, such as greater expansion and a high stem density. The availability of the tissue culture-regenerated plants of the native marsh species makes it possible to select lines from local genotypes that have desirable characteristics for wetland restoration projects, such as blocking P. australis reinvasion.

Seedling sulfide sensitivity among plant species colonizing Phragmites-infested wetlands

Seedling establishment is an important means of re-colonizing herbicide-treated and burned Phragmites australis marshes and of filling in newly created or naturally forming marshes. Knowing the differential sensitivity of the various species to sulfide better enables us to predict which plants are likely to colonize given areas (i.e., be it desirable species or P. australis). This study focuses on the sulfide sensitivity of the seedlings of five plant species that may re-colonize the cleared marsh surface either from wild seed stock or introduced propagules: Spartina alterniflora, Spartina patens, Setaria magna, Atriplex triangularis, and P. australis. Seedlings were grown in culture tubes in semi-solid agar media containing Hoagland’s nutrients; sulfide treatments included levels of sulfide from 0 to 8 mM. Parameters measured included number of leaves, number of lateral roots, shoot length, root length, leaf length, and biomass. Setaria magna proved to be the most sensitive to sulfide, followed in order by A. triangularis, S. patens, P. australis, and S. alterniflora. Differences in edaphic sulfide are not likely to be helpful in favoring S. magna, A. triangularis, or S. patents over P. australis. Phragmites australis was compared to S. alterniflora in a second experiment with six concentrations of sulfide between 0 and 2.0 mM. Results indicated that sulfide levels between 0.4 and 0.9 mM would favor seedling establishment of S. alterniflora over P. australis, and at 0.9 mM, S. alterniflora seedlings would have the decided advantage.

Is the invasion of the common reed, Phragmites australis, into tidal marshes of the eastern US an ecological disaster?

Studies of effects of the invasive brackish marsh plant Phragmites australis (common reed) on estuarine biota are reviewed. With few exceptions, most field studies indicate that these P. australis-dominated marshes have diverse and abundant benthic biota, and are utilized by nekton, comparable to Spartina alterniflora marshes. However, larval mummichogs, Fundulus heteroclitus, appear to be reduced in P. australis marshes compared with S. alterniflora marshes. Small epifauna living on plant stems also appear to be denser on S. alterniflora than P. australis stems. Other studies indicate that the detritus produced by decaying P. australis litter provides food value comparable to that of S. alterniflora and that its production enters estuarine food webs. Therefore, the general assumption that these marshes are ecologically “useless” is untrue. This information should be considered by marsh managers when making decisions about restoration projects.

Benthic communities of common reed Phragmites australis and marsh cordgrass Spartina alterniflora marshes in Chesapeake Bay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 261:51-61 (2003) - doi:10.3354/meps261051 Benthic communities of common reed Phragmites australis and marsh cordgrass Spartina alterniflora marshes in Chesapeake Bay Martin H. Posey1,*, Troy D. Alphin1, David L. Meyer2, John M. Johnson2 1Center for Marine Science and Department of Biological Sciences, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, North Carolina 28409, USA 2National Oceanic and Atmospheric Association (NOAA), Center for Coastal Fisheries and Habitat Research, 101 Pivers Island Road, Beaufort, North Carolina 28516, USA *Email: poseym@uncw.edu ABSTRACT: Invasive species are receiving increased attention both for their direct effects, including competitive displacement and predator-prey interactions, and indirect effects involving ecosystem and habitat alterations. The common reed Phragmites australis is spreading along much of the Atlantic and Gulf coasts of the USA. Its spread is particularly apparent in disturbed oligohaline to mesohaline areas, where it may displace the marsh cordgrass Spartina alterniflora. Because of the different morphologies of these plants, associated sediment effects, and differences in biogeochemical cycling, there is the potential for significant faunal community changes where macrophyte species replacement occurs. We conducted a study in the mesohaline region of Chesapeake Bay to examine differences between benthic communities associated with S. alterniflora and P. australis marshes. Paired P. australis and S. alterniflora marshes were sampled at 4 sites in summer and 2 sites in fall, blocking for tidal height (high marsh versus low marsh) and small-scale topographic features (rivulet and hummock areas in each marsh type). Sediment grain size did not differ between marsh types, and percent organics differed only for P. australis hummock sites compared to other habitat types. Benthic microalgal biomass also did not differ among marsh types. There was only a small effect on faunal abundance patterns, with most species exhibiting slightly higher mean density in Spartina compared to adjacent Phragmites marshes. Much stronger differences in faunal density were observed between hummocks and adjacent rivulets within each marsh type. While macrophyte type had a detectable effect, local microhabitat characteristics had a stronger relation to local faunal abundance patterns. Since such microhabitat characteristics may covary with macrophyte type (although they did not do so in this study), care must be taken in the design and interpretation of comparative marsh studies and more emphasis should be given to including relations of small-scale topographic features with faunal characteristics. In this system and on the scale studied here, macrophyte replacement did not strongly affect the benthic infaunal community. KEY WORDS: Phragmites australis · Spartina alterniflora · Benthos · Invasive species · Chesapeake Bay · Marsh topography Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 261. Online publication date: October 17, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Comparison of nekton use of Phragmites australis and Spartina alterniflora marshes in the Chesapeake Bay, USA

Throughout the eastern USA many Spartina alterniflora salt-marsh systems are being altered through the invasion of Phragmites australis. As a result, substantial declines in the areal dis- tribution of S. alterniflora-dominated habitat have occurred in contrast to increases in P. australis dominated habitat. While information is scarce on nekton use of P. australis marsh, increases in the areal distribution of this species have concerned resource managers. Managers typically view the shift of S. alterniflora to P. australis marsh as a shift from a biologically diverse and productive marsh to one less biologically diverse and productive. We examined nekton use of P. australis marsh relative to S. alterniflora marsh with similar geographic location and physical conditions. We found no signif- icant differences (p > 0.05) in the utilization of P. australis and S. alterniflora marsh by nekton in terms of abundance or biomass. Further, no significant difference (p > 0.05) in the total number of nekton species was evident between P. australis and S. alterniflora marsh. We postulate that under similar environmental and physical conditions these marsh types are equivalent in terms of nekton use. It may be necessary to reevaluate current wetland management practices which involve the elimina- tion of P. australis in favor of S. alterniflora marsh in order to increase nekton use.