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

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

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

Can thin-lipped mullet directly exploit the primary and detritic production of European macrotidal salt marshes?

Juveniles and adults (>100 mm) of Liza ramada colonize macrotidal salt marsh creeks of Mont Saint-Michel bay (France)between March and November, during spring tide floods (43% of the tides) and return to coastal waters during the ebb. This fish species actively feeds during its short stay in the creek (from 1 to 2 h). On average, each fish swallows sediment including living and inert organic matter, which amounts to 8% of its fresh body weight. Their diet is dominated by small benthic items (especially diatoms and salt marsh plant detritus), that correspond to the primary and detritic production of this macrotidal salt marsh creek. Despite very short submersion periods, mullets filter and ingest large quantities of sediment and concentrated organic matter (on average organic matter in stomach content is 31%) produced by these coastal wetlands. European salt marshes are thus shown to act as trophic areas for mullets, which are well adapted to this constraining habitat which is only flooded for short periods during spring tides

Salt Marsh Values in a Changing World: Examining Sea Level Rise on Tidal Marshes with a Surface Elevation Table

Rising seas are threatening coastal communities and putting added pressures on the natural environment. Sea level rise rates are increasing on a global scale (from 1.7 to 3.2 mm/yr). Salt marshes are not only intertidal habitats acutely influenced by sea levels, but they also provide key ecosystem services such as: buffers against storm surges, habitat for wildlife, carbon dioxide storage, and pollutant filtration. In New England, salt marshes have built at a rate of 1 to 2 mm annually over the past 4,000 years, which has kept pace with sea level rise. However, we do not know if salt marshes can keep building if sea levels rise at a more rapid rate of 4 mm/yr or greater. To monitor how salt marshes are responding to faster sea level rise, we measured salt marsh accretion and elevation change along the coast of New Hampshire at three different marshes (a total of 11 stations) using marker horizons and a Surface Elevation Table (SET). The SET sites were established in two marshes over a decade ago and more recently at a third marsh in 2011. Data were collected in 2013 and the new rates are compared to previous elevation changes. The major findings included an unprecedented marsh elevation growth rate of 4.3 mm/yr, which shows that our marshes are building at rates fast enough to keep up with the current sea level rise. Furthermore, the rate of salt marsh building appears to be greater than the global sea level rate of 3.2 mm/yr, suggesting our local rate of sea level rise may be greater than 3.2mm/year. Salt marshes could provide a valuable indirect measure of local sea level rise

Environmental conditions of a salt-marsh biodiversity experiment on the island of Spiekeroog (Germany)

Field experiments investigating biodiversity and ecosystem functioning require the observation of abiotic parameters, especially when carried out in the intertidal zone. An experiment for biodiversity–ecosystem functioning was set up in the intertidal zone of the back-barrier salt marsh of Spiekeroog Island in the German Bight. Here, we report the accompanying instrumentation, maintenance, data acquisition, data handling and data quality control as well as monitoring results observed over a continuous period from September 2014 to April 2017. Time series of abiotic conditions were measured at several sites in the vicinity of newly built experimental salt-marsh islands on the tidal flat. Meteorological measurements were conducted from a weather station (WS, https://doi.org/10.1594/PANGAEA.870988), oceanographic conditions were sampled through a bottom-mounted recording current meter (RCM, https://doi.org/10.1594/PANGAEA.877265) and a bottom-mounted tide and wave recorder (TWR, https://doi.org/10.1594/PANGAEA.877258). Tide data are essential in calculating flooding duration and flooding frequency with respect to different salt-marsh elevation zones. Data loggers (DL) for measuring the water level (DL-W, https://doi.org/10.1594/PANGAEA.877267), temperature (DL-T, https://doi.org/10.1594/PANGAEA.877257), light intensity (DL-L, https://doi.org/10.1594/PANGAEA.877256) and conductivity (DL-C, https://doi.org/10.1594/PANGAEA.877266) were deployed at different elevational zones on the experimental islands and the investigated salt-marsh plots. A data availability of 80% for 17 out of 23 sensors was achieved. Results showed the influence of seasonal and tidal dynamics on the experimental islands. Nearby salt-marsh plots exhibited some differences, e.g., in temperature dynamics. Thus, a consistent, multi-parameter, long-term dataset is available as a basis for further biodiversity and ecosystem functioning studies

Valuing New Hampshire Salt Marshes: An Approach to Measuring Ecosystem Services

David Burdick presented work a method for estimating the ecosystem services benefits of salt marsh restoration. The approach combines ecological valuation, which uses structural and functional indicators to measure the marshes response to restoration, and economic valuation, which uses ecosystem services valuations, to determine the net gain in ecosystem services of marsh restoration

The rationale for attempting to define salt marsh mosquito-breeding areas in Galveston County by remote sensing the associated vegetation

The rationale for attempting to define salt marsh mosquito breeding areas in Galveston County was discussed, including a botanical survey of the marsh plant communities, their relationship to flooding, and their exposure to salt water. Particular emphasis is given to Distichlis spicata, a widespread marsh grass. Evidence suggests that breeding areas of Aedes sollicitans are associated with Distichlis and that both species respond to similar ecological conditions in the salt marsh. Aspects of the remote sensing of the Distichlis are considered

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

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