Section Of Marsh Research Articles

Surface Water and Groundwater Interactions in Salt Marshes and Their Impact on Plant Ecology and Coastal Biogeochemistry

AbstractSalt marshes are highly productive intertidal wetlands providing important ecological services for maintaining coastal biodiversity, buffering against oceanic storms, and acting as efficient carbon sinks. However, about half of these wetlands have been lost globally due to human activities and climate change. Inundated periodically by tidal water, salt marshes are subjected to strong surface water and groundwater interactions, which affect marsh plant growth and biogeochemical exchange with coastal water. This paper reviews the state of knowledge and current approaches to quantifying marsh surface water and groundwater interactions with a focus on porewater flow and associated soil conditions in connection with plant zonation as well as carbon, nutrients, and greenhouse gas fluxes. Porewater flow and solute transport in salt marshes are primarily driven by tides with moderate regulation by rainfall, evapotranspiration and sea level rise. Tidal fluctuations play a key role in plant zonation through alteration of soil aeration and salt transport, and drive the export of significant fluxes of carbon and nutrients to coastal water. Despite recent progress, major knowledge gaps remain. Previous studies focused on flows in creek‐perpendicular marsh sections and overlooked multi‐scale 3D behaviors. Understanding of marsh ecological‐hydrological links under combined influences of different forcing factors and boundary disturbances is lacking. Variations of surface water and groundwater temperatures affect porewater flow, soil conditions and biogeochemical exchanges, but the extent and underlying mechanisms remain unknown. We need to fill these knowledge gaps to advance understanding of salt marshes and thus enhance our ability to protect and restore them.

Greenhouse gas flux with reflooding of a drained salt marsh soil.

Salt marshes are highly effective carbon (C) sinks and bury more C per square meter annually than any other ecosystem. Reclamation and anthropogenic impacts, however, have resulted in extensive losses of salt marshes. Carbon credits can be generated and sold by restoring marshes, but only if C sequestration and net reductions in greenhouse gases (GHG) are reliably quantified. Restored marshes, however, may exhibit different patterns of GHG emissions than natural marshes and it is possible that they could temporarily become sources of N2O even in the usually N-limited estuarine environment. Research on short-term GHG flux following salt marsh restoration is limited to studies of two restored marshes which examined GHG flux more than six months after the return of tidal flooding. Here we report on a laboratory experiment in which soil cores collected from a drained agricultural marsh on the St. Lawrence Estuary were flooded with estuary water. Gas flux measurements immediately after flooding revealed small increases in N2O and CH4, but a large decline in CO2 yielding, from a climatic perspective, a net cooling effect over the observation period. In addition to restoring the land’s capacity to sequester C once a marsh develops, returning tidal flooding thus appears to have the added benefit of stemming large ongoing C losses. With more than 400 km2 of undeveloped dykeland, Eastern Canada is well positioned to restore large sections of marsh and contribute to reducing atmospheric CO2 concentrations.

Restoring Tidal Equilibrium: Removing a Hydrologic Barrier and Lowering Salinity at the Magnolia Inlet, Texas

ABSTRACT Huff, T.P. and Feagin, R.A., 2017. Restoring tidal equilibrium: Removing a hydrologic barrier and lowering salinity at the Magnolia Inlet, Texas. In: Martinez, M.L.; Taramelli, A., and Silva, R. (eds.), Coastal Resilience: Exploring the Many Challenges from Different Viewpoints. Journal of Coastal Research, Special Issue No. 77, pp. 97–103. Coconut Creek (Florida), ISSN 0749-0208. A large area of salt marsh located between Magnolia Beach and Indianola, Texas had rapidly degraded over the last few decades due to a hydrologic barrier. Sediment and shell debris in the main tidal channel had greatly reduced flow between interior sections of marsh and the adjacent open bay, blocking all hydrologic exchange except for extreme tides. As a result, the impounded waters were often hypersaline, the vegetation was dying, and access to habitat was restricted for aquatic nekton. Our overall objective was to identify the cross section of debris that would need to be removed from the channel in order to restore ...

Identification conformity of wetlands biotopes of the Northwest of the Black Sea region

This publication presents the analysis of the mostly used international and Ukrainian classification systems for wetland areas performed for identification of different-type marsh biotopes of steppe rivers in the Northwest Black Sea Region. Among the classification systems, the most well-known are the Ramsar Classification System for Wetland Type (1971) and Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al., 1979). In these systems, valley marsh biotopes are identified as riverine and palustrine, non-tidal, unstable (perennial impounded and seasonal/intermittent) freshwater marshes on mineral rich soils predominantly covered by grasslike plants (rush, reedmace, sedge). The delta marshes of the Danube, Dniester and Dnieper are referred to as tidal brackish and freshwater marshes. According to Ukrainian classification systems for hygromorphic geosystem, marsh biotopes are regarded as mouth wetlands, which is peculiar to delta marsh areas of the Danube and Dnieper interfluve. Thus, riverbed marshes of small and medium-sized rivers are located in other areas and are usually met both in the lower (continuous marsh areas), middle (fragmented marsh mosaic), and upper (coastland) river flow areas, which is caused by an unstable watercourse rate and transforming of their riverbed parts into marsh sections covered by eurytopic wetland species.

Rapid wetland expansion during European settlement and its implication for marsh survival under modern sediment delivery rates: COMMENT

The paper by [Kirwan et al. (2011)][1] proposes an intriguing hypothesis on the formation of a salt marsh in New England (United States). Through the analysis of sediment cores and radiocarbon dates, the authors show that a section of marsh formed after the European settlement in Massachusetts due

Suspended sediment deposition and trapping efficiency in a Delaware salt marsh

This study examined sediment deposition and retention in a section of salt marsh in the St. Jones River estuary in Delaware. Sediment traps, siphon samplers, a LISST particle sizer, and four water level sensors were deployed in a 100 m by 200 m grid over the course of a spring tide in June 2007. The objective was to determine the relative influences of suspended sediment concentration, settling velocity, tidal hydroperiod, and vegetation density on sediment deposition and trapping efficiency within a small section of marsh. Hydroperiod is not a major contributor to sediment deposition in the study plot. Spatial patterns in depositional processes on tidal timescales are instead primarily controlled by overmarsh SSC, settling velocity, and distance from the tidal channel. Trapping efficiency, or the ratio of measured deposition and the amount of sediment available for deposition, decreased with distance away from the tidal channel, indicating that less of the available suspended sediment was deposited in the marsh interior. The suspended particles were flocculated, but floc sizes decreased with distance away from the tidal channel.

Tidally driven multiscale pore water flow in a creek‐marsh system

Intertidal wetlands are complex hydrological systems characterized by strong, dynamic interactions between coastal surface water and groundwater, driven particularly by tides. We simulated such interactions with a focus on three‐dimensional, variably saturated pore water flow in a creek‐marsh system that bordered a tidally dominated main channel. Simulated intratidal groundwater dynamics exhibited significant flow asymmetry with nonzero mean flow velocities over the tidal period. The tidally averaged flow led to pore water circulation with three dimensionality linked strongly to the marsh topography, over a range of spatial scales: near the creek bank, around the creek meander, and over long marsh sections inclined toward the main channel. Particle tracking revealed that time scales associated with these circulations differed by orders of magnitude. Under the simulated conditions, the creek served as the main outlet of the pore water circulation paths, especially those linked with infiltration into the upper marsh surface areas away from the main channel. Local net efflux, influenced by the creek channel curvature, varied along the creek but produced a total discharge largely proportional to the creek length. Water infiltrating the soil in the lower marsh surface areas away from the creek tended to discharge directly to the main channel. However, the total discharge to the main channel was much less than that into the creek. This study highlights the hydrological complexity of intertidal marshes and the need for further research on interactions among marsh morphology, hydrology, and ecology, which underpin the functionalities of these wetland systems.

Accelerated erosion of saltmarshes infested by the non-native burrowing crustacean Sphaeroma quoianum

Lateral erosion of saltmarshes is affected by many abiotic and biotic factors. While abiotic factors are typically regarded as primary drivers of erosion, biotic influences such as burrow- ing or bioturbating taxa can also extensively modify the physical structure of this marine habitat. Many estuaries on the Pacific coast of North America have been invaded by populations of the burrowing non-native isopod Sphaeroma quoianum, which are thought to exacerbate the erosion of saltmarshes. We conducted a mensurative experiment to examine the relationship between popula- tions of S. quoianum and lateral erosion rate of saltmarshes in Coos Bay, Oregon, USA. After 1 yr, we measured higher lateral erosion rates, more undercutting, and higher numbers of calved and slumped marsh sections in marsh sites infested by S. quoianum than in uninfested sites. This effect was also consistent at smaller spatial scales: we found lateral erosion was 300% higher in burrowed areas than in adjacent (within approx. 1 m) unburrowed areas within infested sites. Our results sug- gest that the prodigious burrowing by dense populations of S. quoianum can accelerate erosion rates in saltmarshes and are substantial geomorphic agents of change in estuaries on the Pacific coast of North America.

Denitrification in Marsh‐Pond‐Marsh Constructed Wetlands Treating Swine Wastewater at Different Loading Rates

Denitrification in constructed wetlands can be very important in the treatment of swine lagoon effluent when land application areas are limited. The objectives of this investigation were to determine (i) the denitrification enzyme activity (DEA) in the marsh sediments of marsh‐pond‐marsh (MPM) constructed wetlands, (ii) changes in DEA with additions of carbon and nitrate, and (iii) the response of DEA to different wastewater N loading rates. Swine wastewater was applied to six MPM wetlands located at North Carolina A&T State University, Greensboro, NC, at rates of 4 to 35 kg N ha−1d−1Soil samples were obtained from the top 25 mm of the marsh sections on four dates for determination of DEA via the acetylene blockage method (blocked at N2O). Headspace N2O was measured via gas chromatography. In the control treatment, they ranged from 0.06 to 1.13 and 0.16 to 0.79 mg N2O‐N kg−1soil hr−1in the first and second marshes, respectively. In both marshes, the DEA rate was significantly increased with the addition of nitrate but not by glucose, indicating that nitrate was a clear limiting factor for denitrification. The DEA in both the control and the amended treatments increased dramatically with increased wastewater N loading, and the increases were generally more pronounced in the first marsh. The DEA values produced in the absence of acetylene blockage did not increase with wastewater N loading rate. Denitrification enzyme activity levels in the marsh sections of the MPM were generally consistent with a highly denitrifying environment.

Phragmites australis invasion and expansion in tidal wetlands: Interactions among salinity, sulfide, and hydrology

Through their physiological effects on ion, oxygen, and carbon balance, respectively, salinity, sulfide, and prolonged flooding combine to constrain the invasion and spread ofPhragmites in tidal wetlands. Initial sites of vigorous invasion by seed germination and growth from rhizome fragments appear limited to sections of marsh where salinity is <10‰, sulfide concentrations are less than 0.1 mM, and flooding frequency is less than 10%. In polyhaline tidal wetlands the invasion sites include the upland fringe and some high marsh creek banks. The zones of potential invasion tend to be larger in marshes occupying lower-salinity portions of estuaries and in marshes that have been altered hydrologically. Owing to clonal integration and a positive feedback loop of growth-induced modification of edaphic soil conditions, however, a greater total area of wetland is susceptible toPhragmites expansion away from sites of establishment. Mature clones have been reported growing in different marshes with salinity up to 45‰, sulfide concentration up to 1.75 mM, and flooding frequency up to 100%. ForPhragmites establishment and expansion in tidal marshes, windows of opportunity open with microtopographic enhancement of subsurface drainage patterns, marsh-wide depression of flooding and salinity regimes, and variation in sea level driven by global warming and lunar nodal cycles. To avoidPhragmites monocultures, tidal wetland creation, restoration, and management must be considered within the context of these different scales of plant-environment interaction.

Treatment of swine wastewater in marsh-pond-marsh constructed wetlands

Swine waste is commonly treated in the USA by flushing into an anaerobic lagoon and subsequently applying to land. This natural system type of application has been part of agricultural practice for many years. However, it is currently under scrutiny by regulators. An alternate natural system technology to treat swine wastewater may be constructed wetland. For this study we used four wetland cells (11 m width x 40 m length) with a marsh-pond-marsh design. The marsh sections were planted to cattail (Typha latifolia, L.) and bulrushes (Scirpus americanus). Two cells were loaded with 16 kg N ha(-1) day(-1) with a detention of 21 days. They removed 51% of the added N. Two additional cells were loaded with 32 kg ha(-1) day(-1) with 10.5 days detention. These cells removed only 37% of the added N. However, treatment operations included cold months in which treatment was much less efficient. Removal of N was moderately correlated with the temperature. During the warmer periods removal efficiencies were more consistent with the high removal rates reported for continuous marsh systems--often > than 70%. Phosphorus removal ranged from 30 to 45%. Aquatic macrophytes (plants and floating) assimilated about 320 and 35 kg ha(-1), respectively of N and P.

Wave Transformation Over Salt Marshes: A Field and Numerical Modelling Study from North Norfolk, England

This paper presents quantitative evidence for the effectiveness of a meso- to macro-tidal open coast salt marsh in attenuating incoming waves over a range of tidal and meteorological conditions. Field measurements of wind waves at three locations on a sand flat to salt marsh cross-shore transect showed that wave energy dissipation rates over the salt marsh were significantly higher (at an average of 82%) than over the sand flat (at an average of 29%). The difference in water depth between the sand flat and salt marsh sections of the transect was not sufficient to account for the difference in wave attenuation, indicating that an increase in surface friction is the primary reason for increased wave attenuation over the salt marsh. Comparison of the field results with a numerical model based on theoretical wave energy dissipation suggests that surface friction factors of the order of ≤0·4 are responsible for the high values of wave attenuation over the salt marsh. The results provide empirical support, both for maintaining salt marshes in front of existing sea defence lines and for creating new salt marsh as part of coastal set-back/shoreline realignment schemes.

Evaluation of a macro encapsulated repellent to reduce risk of white phosphorous ingestion by waterfowl foraging in a contaminated marsh

White Phosphorous contamination of a marsh at a U.S. Army artillery training range in Alaska is a causative agent for waterfowl mortality. We developed an encapsulated bird repellent containing the active ingredient, methyl anthranilate, and evaluated the formulations efficacy in reducing feeding activity by ducks, reducing mortality of ducks feeding in contaminated sediments, and the repellents ability to move ducks from contaminated areas. The formulation has a limited life span of about 4 days. However, in pen trials feeding activity of mallards can be reduced by up to 80%. Long term exposure to treated sediments confers a survival advantage to mallards tested in pens, and free-ranging mallards can be moved off of treated sections of marsh. This prototype formulation may have utility in the short-term remediation of contaminated sediments for the protection of waterfowl.

Porewater chemistry associated withPhragmites andSpartina in a Connecticut tidal marsh

Porewater chemistry and plant height were examined along 5 short transects extending from sections of tidal marsh dominated by the common reedPhragmites australis to those dominated bySpartina alterniflora. Phragmites was found at relatively higher tidal elevations along 4 of 5 transects; along all transects,Phragmites was growing and flowering throughout a porewater salinity range from 12 to 30 ppt. Dissolved inorganic phosphorus concentrations varied from 0 to >35 μM in bothSpartina andPhragmites sections of marsh, but ammonium concentrations averaged >40 μM in zones dominated bySpartina and 400 μM, perhaps due to sulfide inhibition of nitrogen uptake for growth. The persistence ofPhragmites at field conditions of high salinity and elevated sulfide concentrations suggests that hydrologic management may be insufficient to eradicatePhragmites in tidal wetlands.

Factors affecting vegetation dieback of an oligohaline marsh in coastal Louisiana: Field manipulation of salinity and submergence

Vegetation dieback is an important component of wetland loss in low salinity marshes of coastal Louisiana. A field experiment was conducted to determine the factors responsible for vegetation dieback within oligohaline marshes of Louisiana. Sections of marsh, dominated by Sagittaria lancifolia L., were transplanted into one of four locations depending on the treatment: (1) increased submergence—sods were lowered 15 cm below the donor marsh surface, (2) increased salinity—sods were transplanted into a higher salinity marsh and adjacent dieback pond, (3) increased salinity and submergence—sods were transplanted into a higher salinity marsh and adjacent dieback pond at 15 cm below the marsh surface, and (4) control—sods were exhumed and replaced at the ambient elevation of the donor marsh. Plant biomass and edaphic characteristics were measured after 5 mo. An increase in submergence caused decreased plant growth of the S. lancifolia‐dominated marsh community. An increase in salinities to 4–5 g/kg were not detrimental to plant growth. Although saltwater intrusion alone did not cause decreased growth of the S. lancifolia‐dominnled plant community, the combination of saltwater intrusion and increased plant submergence caused the greatest decrease in plant growth due to increased toxic sulfides and a likely reduction in the uptake of NH4‐N by the wetland vegetation. This illustrates that the dieback of oligohaline marsh vegetation can be alleviated by decreasing plant submergence even at salinities as high as 4.6 g/kg.

Environmental conditions of a backfilled pipeline canal four years after construction

We studied the environmental conditions along 56 km of a backfilled pipeline canal four years after construction was completed. The canal traverses fresh, intermediate, brackish, and saline marshes in southeastern Louisiana. Over one-third of the sampling sections in the fresh intermediate marsh regained more than 60% vegetation cover; mean canal depth was 44 cm, and submerged aquatic vegetation (SAV) covered 59% of the bottom. The brackish marsh sections revegetated only where the canal passed through the mineral soils of the Bayou Lafourche natural levee; mean canal depth was 67 cm, and SAV covered 23% of the bottom. The salt marsh revegetated poorly; the area remained 80% open water, as it was before canal construction. Mean canal depth was 59 cm, and SAV covered 10% of the bottom. Backfilling did not return the marsh to its original condition, but the shallow ponds that formed along the canal resemble natural ponds in depth and vegetation.

Spoil banks: Effects on a coastal marsh water-level regime

Above- and below-ground water-level fluctuations were measured in the marshes south of New Orleans, Louisiana, between November 1982 and December 1983. The purpose of the program was to define the basic marsh water-level regime and to investigate how canal spoil banks may influence the water-level regime. Two study areas were used: (1) a control area, defined as a section of marsh with unrestricted hydrologic connection to an adjacent bayou; and, (2) a partially-impounded area, defined as an area with limited hydrologic connection to an adjacent bayou due to the presence of dredged canal spoil banks. Data sources included marsh water levels from gages deployed at three sites within the study areas and water levels from the adjacent bayous obtained from the tide gages of U.S. Army Corps of Engineers. Data from all marsh gage sites showed a similar pattern with a distinct surface and subsurface diurnal tidal signal superimposed upon other, larger scale events. These larger scale events correspond to the passage of weather fronts. The data also indicated that a significant amount of water-level fluctuation in the marshes occurs below ground. A comparison of the control area and the partially-impounded site indicated that the spoil banks changed the response of the marsh water levels to the forcing from the bayou, with the result that the partially-impounded area: (1) was flooded 141 hours more per month than the control area; (2) had fewer, but longer flooding events; (3) had fewer but longer drying events; and (4) reduced water exchange, both above and below ground.

The Development of a Tidal Marsh: Upland and Oceanic Influences

A stratigraphic study was undertaken to determine the historic role of watershed and sea—level changes on the development of Fresh Pond Marsh on Long Island's north shore. Pollen analytic, radiometric, and macrofossil techniques were aimed at differentiating among marsh, watershed, and regional changes over the last 1000 yr. A study of surface pollen distribution was conducted to determine pollen source and tidal influences on pollen deposition and to evaluate comparability of fossil pollen records from various intertidal environments. Regional and local inputs along a transect that included several tidal regimes were identified. Pollen counts from these different environments were comparable and proved useful for marsh reconstructions. Pollen analyses from the coastal marsh and a nearby lake distinguished changes in upland vegetation and cultural patterns within the watershed from those occurring regionally. Records of local pollen, foraminifera, macrofossils, rhizomes, and lithology indicated that the history of Fresh Pond Marsh has included periods of both tidal and freshwater conditions. Close dating control provided by 210Pb measurements and historically documented changes in indicator pollen taxa identified marsh responses to external influences, including dynamics of a baymouth bar, land clearing, agriculture, mosquito ditching, and sea—level fluctuations. Results showed that (1) tidal marsh sections can provide sensitive records of both upland and marsh vegetation histories, (2) pollen and macrofossil records can be closely linked to tide—gauge records and are responsive to short—term changes in sea level with a high degree of temporal resolution, and (3) upland influences can play an important role in determining the course of plant succession in the intertidal environment. Pollen provides the most sensitive record of marsh and upland development, as long as pollen source is accounted for.

The effect of a seasonal change in canopy structure on the photosynthetic efficiency of a salt marsh.

A seasonal decline in the photosynthetic efficiency of a Chesapeake Bay salt marsh occurs concurrently with a seasonal shift in foliage canopy structure from erect- to horizontal-leaved. Infrared gas analysis was used to measure net photosynthesis by isolated sections of marsh before and after the canopy was subjected to experimental manipulations designed to mimiic the natural canopy change. During June and July when the canopy was normally erect, inducing horizontal leaf orientation reduced net photosynthesis by 50 percent. In late August, when the canopy was naturally horizontal, making the leaves erect increased photosynthesis. These results support the hypothesis that the normal seasonal decline in photosynthesis is due, at least in part, to the shift in canopy structure.

Land, Tenure, and Population in the Royal Manor of Havering, Essex, 1251–13521′3

T HE king's manor of Havering, i 2 miles east of London, was surveyed by the crown twice during the central medieval period, in I 25i and again a century later. These two Extents, particularly the unusually full record from I352/3, enable us to describe the tenure of land within the manor, to examine the nature of the subtenants and subtenancies, and to calculate how much land each person had in his actual occupancy. A tentative history of land clearing, population, and tenure in Havering during the years between I25i and I 352/3 may be compiled from a variety of other records. The rather precocious development of Havering's economy into a later medieval pattern, and the manor's position on the periphery of the London market, lend general interest to this material. Wavering's physical setting and legal/administrative background were of primary importance to its economic life. The manor was large in size, i6,ooo acres, stretching northward from the Thames for nine miles. After a section of marsh along the river the land in the southern half of the area is easily worked, gravelly soil, of rather low fertility; it was in this region that the original fields and the community of Hornchurch lay. The market town of Romford, on the main London-Chelmsford road, was the institutional centre of the manor, north of which lay heavy London clay, still densely wooded in i 200. With the exception of the enclosed royal park, the woodlands were gradually being taken over by the tenants throughout the medieval and Tudor periods. In io86 the tenant and demesne lands constituted about 5,ooo acres. By I25I this had grown to 8,500 acres, and in the following century another i,000 acres were added. Between I350 and i650 the arrented land grew from 9,500 to i2,000 acres. Havering was a royal manor of the ancient demesne.2 Rents and services had been fixed before I 251, and with few exceptions the crown made no attempt to supervise or control what went on within the manor as long as the traditional issues were forthcoming. No restriction was placed upon the transfer or division of land, upon marriage, or upon personal mobility. There was thus an open land market among a population of functionally free peasants. Havering's economy was diverse and flexible. Most land was held in separate fields, ranging normally from 3 to 2o acres. During the thirteenth and fourteenth