Lateral Marsh Edge Erosion as a Source of Sediments for Vertical Marsh Accretion

With sea level rise accelerating and sediment inputs to the coast declining worldwide, there is concern that tidal wetlands will drown. To better understand this concern, sources of sediment contributing to marsh elevation gain were computed for Plum Island Sound estuary, MA, USA. We quantified input of sediment from rivers and erosion of marsh edges. Maintaining elevation relative to the recent sea level rise rate of 2.8 mm yr−1 requires input of 32,299 MT yr−1 of sediment. The input from watersheds is only 3,210 MT yr−1. Marsh edge erosion, based on a comparison of 2005 and 2011 LiDAR data, provides 10,032 MT yr−1. This level of erosion is met by \u3c0.1% of total marsh area eroded annually. Mass balance suggests that 19,070 MT yr−1 should be of tidal flat or oceanic origin. The estuarine distribution of 14C and 13C isotopes of suspended particulate organic carbon confirms the resuspension of ancient marsh peat from marsh edge erosion, and the vertical distribution of 14C‐humin material in marsh sediment is indicative of the deposition of ancient organic carbon on the marsh platform. High resuspension rates in the estuarine water column are sufficient to meet marsh accretionary needs. Marsh edge erosion provides an important fraction of the material needed for marsh accretion. Because of limited sediment supply and sea level rise, the marsh platform maintains elevation at the expense of total marsh area

Restoring Salt Marsh and Functions to Newly Acquired Shoreline in North Mill Pond, Portsmouth

A berm of construction debris used to fill salt marsh and steepen the shoreline along North Mill Pond many decades ago was removed in 2010 after the land was deeded to the City. Removal of the berm reestablished regular tidal flooding to over 2,400 ft2 of tidal marsh. From 2009 to 2011, the fifth grade classes at New Franklin School learned about the project and planted mussels, shrubs and marsh plants at the site. Plant survival was excellent in the low marsh (94%) and good in the high marsh (77%). By September 2011 (Year Two) plant cover increased to 42% in the low marsh and 13% in the high marsh. After the first growing season for the upper marsh (planted in May, 2011), cover reached 23%. Some fine-grained sediment was eroded from the surface of the high marsh due to low plant cover, but no linear features or erosion scours were observed. The site can be observed over time online, including construction and plant development at http://picturepost.unh.edu

Salt marsh harvest mouse abundance and site use in a managed marsh

The salt marsh harvest mouse (Reithrodontomys raviventris) is a federal and California listed endangered mammal endemic to the San Francisco Bay. The objectives of this research were to determine habitat use of endangered salt marsh harvest mice in a managed marsh in Fremont California, and to evaluate whether managed flooding of the marsh provides favorable habitat conditions for the mice. In addition, this research explores the effectiveness of using mark-recapture model selection analysis to estimate capture probability, survival, and population growth rate for salt marsh harvest mice. Mice were captured for four nights per month between May and August, 2008. Thirty-six unique salt marsh harvest mice were captured for a catch per 100 nights of trap effort of 1.9. The sex ratio of male to female mice was skewed towards males with a sex of 2.3:1. Salt marsh harvest mice were distributed randomly throughout the marsh and no relationships were found between mice distribution and pickleweed salinity, pickleweed height, distance to levees, distance to dry or filled water bodies, percent cover of vegetation, or sympatric rodents. The findings of this study indicate that catch-per-trap-effort, the current standard method to estimate salt marsh harvest mice populations, may not be accurate. The results of this study can be used by managers of salt marsh harvest mice habitat to manage and estimate mouse populations

Water Quality Monitoring of the Indiana Dunes National Lakeshore Great Marsh Complex

The Great Marsh complex of the Indiana Dunes National Lakeshore was drained extensively by humans, beginning in the late 1800’s to provide land for farming and residences. Since 1998, 500 acres of the Great Marsh complex have been undergoing restoration in an attempt to return them to their pre-developed conditions. To assess the success of the ongoing restoration on water quality, 15 different parameters used to assess water quality are being measured. Data collected from June 2007 through July 2011 indicates that the water quality is typical of that for a wetlands in this region, and that the Great Marsh complex is functioning properly as a wetlands. For example, total phosphorous analyses indicate that the Great Marsh complex is consuming substantial amounts of phosphorus present in water entering the wetland, that the average conductivity in the Great Marsh complex is ≈270µS/cm, and that the amount of nitrogen in the water generall y decreases as the water passes through the marsh. The restored Great Marsh complex also experiences seasonal changes that are characteristic of a wetlands. This includes fluctuating water temperatures, water levels, pH levels, and dissolved oxygen levels

Experimental salt marsh islands: a model system for novel metacommunity experiments

Shallow tidal coasts are characterised by shifting tidal flats and emerging or eroding islands above the high tide line. Salt marsh vegetation colonising new habitats distant from existing marshes are an ideal model to investigate metacommunity theory. We installed a set of 12 experimental salt marsh islands made from metal cages on a tidal flat in the German Wadden Sea to study the assembly of salt marsh communities in a metacommunity context. Experimental plots at the same elevation were established within the adjacent salt marsh on the island of Spiekeroog. For both, experimental islands and salt marsh enclosed plots, the same three elevational levels were realised while creating bare patches open for colonisation and vegetated patches with a defined transplanted community. One year into the experiment, the bare islands were colonised by plant species with high fecundity although with a lower frequency compared to the salt marsh enclosed bare plots. Initial plant community variations due to species sorting along the inundation gradient were evident in the transplanted vegetation. Competitive exclusion was not observed and is only expected to unfold in the coming years. Our study highlights that spatially and temporally explicit metacommunity dynamics should be considered in salt marsh plant community assembly and disassembly

Feeding ecology of 0-group sea bass Dicentrarchus labrax in salt marshes of Mont Saint-Michel bay (France)

0-group sea bass, Dicentrarchus labrax, colonize intertidal marsh creeks of Mont Saint Michel Bay, France, on spring tides (e.g., 43% of the tides) during flood and return to coastal waters during ebb. Most arrived with empty stomachs (33%), and feed actively during their short stay in the creeks (from 1 to 2 h) where they consumed on average a minimum of 8% of their body weight. During flood tide, diet was dominated by mysids, Neomysis integer, which feed on marsh detritus. During ebb, when young sea bass left tidal marsh creeks, the majority had full stomachs (more than 98%) and diet was dominated by the most abundant marsh (including vegetated tidal flats and associated marsh creeks) resident amphipod, Orchestia gammarellus. Temporal and tidal effects on diet composition were shown to be insignificant. Foraging in vegetated flats occurs very rarely since they are only flooded by about 5% of the tides. It was shown that primary and secondary production of intertidal salt marshes play a fundamental role in the feeding of 0-group sea bass. This suggests that the well known nursery function of estuarine systems, which is usually restricted to subtidal and intertidal flats, ought to be extended to the supratidal, vegetated marshes and mainly to intertidal marsh creeks

Wetlands Evaluation for Philbrick\u27s Pond Marsh Drainage Evaluation North Hampton, NH

Philbrick’s Pond is a lagoon type estuary that formed landward of barrier beach spits in North Hampton, NH. Its inlet was stabilized and restricted by the road that is now Route 1A or Ocean Boulevard. Water flow from the Gulf of Maine passes through a culvert running under Route 1A and into a small waterway and is further restricted as it runs through a clay pipe under an old trolley berm. The lagoon is characterized as a 29 acre tidal marsh. The goal of the overall project is to evaluate the condition and hydrology of the two restrictions recognizing the conflicting needs for improved drainage from upstream flooding and limiting tidal flooding associated with extreme (i.e., storm surge) and normal flooding events due to sea level rise. The tidal marsh itself is a resource held in the public trust and therefore should be protected from any negative impacts associated with current conditions or predicted impacts due to future alternatives that may be chosen by the Town and its residents. Ditching of the marsh in the mid twentieth century rerouted drainage paths (e.g., Chapel Brook) and has resulted in large areas of vegetation loss between ditches in the past 60 years, as first reported by Short in 1984. The objectives of this report on the tidal marsh are threefold: 1) to evaluate the health of the tidal marsh by comparing existing and new data in Philbrick’s Pond with conditions found in the Little River tidal marsh just to the south; 2) characterize the relative benefits to the tidal marsh for the hydraulic alternatives evaluated by the hydrologic modeling; and 3) recommend management actions to restore marsh health using small scale drainage improvements (also known as runneling)

Impact of sheep grazing on juvenile sea bass, Dicentrarchus labrax L., in tidal salt marshes

The diet of young of the year sea bass, Dicentrarchus labrax L., from sheep grazed and ungrazed tidal salt marshes were com-pared qualitatively and quantitatively in Mont Saint-Michel Bay. In areas without grazing pressure, the vegetation gradient changes from a pioneer Puccinellia maritima dominated community at the tidal ¯at boundaries through a Atriplex portulacoides dominated community in the middle of the marsh to a mature Elymus pungens dominated community at the landward edge. The A. portula-coides community is highly productive and provides important quantities of litter which provides a habitat and good supply to substain high densities of the detrivorous amphipod Orchestia gammarellus. In the grazed areas, the vegetation is replaced by P. maritima communities, a low productive grass plant, and food availability and habitat suitability are reduced for O. gammarellus. Juvenile sea bass colonise the salt marsh at ¯ood during 43% of the spring tides which inundate the salt marsh creeks. They forage inside the marsh and feed mainly on O. gammarellus in the ungrazed marshes. In grazed areas, this amphipod is replaced by other species and juvenile sea bass consume less food from the marsh. This illustrates a direct effect of a terrestrial herbivore on a coastal food web, and suggests that management of salt marsh is complex and promotion of one component of their biota could involve reductions in other species

Pickering Brook Salt Marsh Restoration - Phase II

In the early 1900’s, the majority of coastal salt marshes in New England were ditched as part of an aggressive mosquito control program. In an attempt to eradicate mosquito-breeding habitat, open water areas were drained by a series of ditches excavated in the thick peat soils. Elimination of open water and the unnatural drainage patterns led to degradation of healthy, functional saltmarsh systems and the disappearance of critical habitat for American black ducks, wading birds, shorebirds, shellfish, and fish species, including those that eat mosquito larvae. The practice of mosquito ditching has since been found to have unintended consequences in salt marshes. The artificial ditch systems were found to hold shallow water just long enough for mosquitoes to successfully breed, while prohibiting access to predatory fish species that eat the larvae. Mosquito populations thrived. Ditching also lowered the water table and reduced soil salinities, thus increasing the potential for the invasion of non-native species, such as Phragmites australis (Daiber 1986). Overall, ditching decreased habitat for native species, disrupted the normal hydrologic functions of the salt marsh ecosystem and likely increased mosquito populations. The 23-acre salt marsh addressed in Phase II of this project is part of the larger 42-acre Pickering Brook salt marsh restoration project area (Phase I: 19 acres, Phase II: 23 acres). The Phase II salt marsh is located on the north side of Pierce Point, along Pickering Brook, adjacent to Great Bay in Greenland, Rockingham County, New Hampshire. It is located within the Great Bay Estuary and is identified as a high priority habitat in the Habitat Protection Plan of the Great Bay Resource Protection Partnership. The goal of the Pickering Brook Salt Marsh Restoration Project Phase I and Phase II was to restore a more natural hydrologic regime and provide permanent open water areas on the marsh surface. Restoration activities included the creation and enhancement of surface pools and reclamation of the man-made ditches, while imposing the least impact to the marsh surface. The restoration will also manage mosquito populations, expand recreational opportunities and improve water quality on the marsh Phase II construction occurred under permit number 2002-02056 as amended. Ducks Unlimited contracted with SWAMP, Inc. to complete restoration activities with specialized low ground pressure equipment. Using a specialized wetland excavator, 13 man-made ditches were filled using marsh soils excavated during the enhancement of four permanent pools. To restore the marsh platform of the 23-acre Phase II salt marsh, approximately 470 CY of material was excavated for pool enhancement and then returned to the marsh through the filling or partial filling of existing ditches. Phase II earthmoving activities were completed by April 30, 2004. A monitoring plan was established for Pickering Brook based on a combination of the GPAC and U.S. Fish and Wildlife Service, Coastal Program protocols. Monitoring will provide data necessary to evaluate both restoration approaches and their rate of success at accomplishing goals for this site through the sampling of chosen parameters or indicators. Data analysis and conclusions are beyond the scope of this restoration project and will be conducted under a separate contract. Data was collected with the help of local landowners and volunteers from the Portsmouth Country Club, the Great Bay National Estuarine Research Reserve, and Ducks Unlimited, Inc. Parameters used to assess the success of this restoration include fish use, bird use, mosquito larvae abundance, water levels and salinity, and native vegetation growth. In the ever-evolving world of salt marsh restoration, it is important to incorporate an adaptive management plan into project design. For larger areas, a phased approach may also provide flexibility and benefit restoration efforts at a specific site under specific conditions. The completion of Phase I of the Pickering Brook restoration provided important information and feedback that were used to modify the Pickering Phase II restoration design. The two approaches used to reclaim man-made ditches at Pickering Brook were meant to address the goals and objectives of the restoration plan. Monitoring data collected in subsequent years will be analyzed to comparatively evaluate marsh recovery. Using these two techniques side by side creates an opportunity for study and will provide researchers and land managers with great insight into the response of this salt marsh community to these practices

Development and Monitoring of Revegetation Methods: Connecting Students with Restoration Activities at Awcomin Marsh

Five classes in a local elementary school participated in an effort to grow and plant high marsh and upper border vegetation at a salt marsh restoration site in spring 2005. Seeds of six marsh upper edge species were successfully germinated and grown into seedlings by third graders. The seedlings were planted by the students in late spring 2005, but only switchgrass and quackgrass plants appeared to have established and survived after one year. Mature shoots of three high marsh species planted by the third graders (salt hay, salt grass and black grass) established successfully and continue to proliferate. In addition, we assessed an experiment of cordgrass plantings performed by community volunteers in 2002. The experiment was designed to test the effectiveness of three planting techniques at a salt marsh restored by the excavation of old dredge spoil that had been colonized by common reed. After four growing seasons, Plug, Bare Root Shoot, and Seed Head planting techniques exhibited greater cover of cordgrass and total cover of vascular plants when compared with unplanted areas. Cover of perennial plants (e.g., cordgrass), which contributes directly to belowground soil development in salt marshes, dominated the planted plots. Cover of annual species dominated the unplanted plots. Planting cordgrass in areas where dredge spoils and common reed had been excavated from a historic marsh accelerated the development of native vegetation compared with unplanted areas. Performance and evaluation of the two sets of plantings has provided information about appropriate planting techniques for our region and has involved and educated the local community about the values of salt marsh to promote stewardship. Recommendations included the use of bare root shoot and seed head planting techniques where cordgrass is desired. Outside plots or a greenhouse may be needed for successful propagation of upper edge marsh species from seed, and a planting program that includes mature plants as well as seedlings is recommended to ensure success