Mary-Jane James-Pirri

CHANGES IN SALT MARSH VEGETATION, PHRAGMITES AUSTRALIS, AND NEKTON IN RESPONSE TO INCREASED TIDAL FLUSHING IN A NEW ENGLAND SALT MARSH

This study examined the response of Argilla Marsh in Ipswich, Massachusetts, USA to increased tidal flushing instituted to restore a salt marsh invaded by Phragmites australis. In late fall 1998, we replaced the old 0.9-m-diameter culvert feeding this marsh with a 2.4 × 1.5-m box culvert, thus increasing both the volume of tidal exchange and porewater salinity. We carried out yearly sampling of vegetation for two years pre-restoration and for four years after restoration. Analysis of Similarities (ANOSIM) showed that the plant community on the restored marsh had changed after restoration but that on the reference marshes had not. Over 80% of the change in the restored marsh was attributed to an increase in Spartina alterniflora cover and decreases in the cover of Phragmites australis, Typha angustifolia, and Solidago sempervirens. The two brackish species, P. australis and T. angustifolia showed an immediate negative response to the increased flooding and salinity. Surviving P. australis culms in the restored marsh were shorter in stature than they were prior to restoration, suggesting that the increased flooding and porewater salinities had lowered the productivity of this species. The increase in S. alterniflora post-restoration fit an exponential curve, indicating that there was a lag in its response initially, but then it expanded rapidly and was still in a very rapid expansion phase after four years. Despite an overall decline of P. australis on the scale of the whole marsh, there was a great deal of variation in responses of individual patches of P. australis to the restoration. Some declined, some were unchanged, and some even increased. The response of nekton to the restoration was less obvious than that of vegetation. Before restoration, the creek system in the tidally restricted marsh functioned like an impoundment that was only marginally connected to the larger salt marsh ecosystem. At that time, seining indicated that more species of nekton occurred at greater densities in creeks in the tidally restricted marsh than in the downstream reference. Increasing the tidal amplitude in the restored marsh resulted in an overall decline in the catch per unit effort there. In contrast to the creeks, the Spartinadominated section of the flooded marsh surface in the restored marsh did harbor more Fundulus heteroclitus, particularly the smaller size class, than did the downstream reference marsh or a P. australis patch in the restored marsh. Our analysis of vegetation and nekton suggests that Argilla Marsh was still adjusting to hydrologic changes four years after restoration.

Monitoring food web changes in tide-restored salt marshes: A carbon stable isotope approach

Primary producer (angiosperms, macroalgae, submerged aquatic vegetation), suspended particulate matter, andFundulus heteroclitus isotope values (δ13C, δ15N, δ34S) were examined to assess their use as indicators for changes in food web support functions in tidally-restored salt marshes. Study sites, located throughout the southern New England region (USA), ranged fromSpartina alterniflora-dominated reference marshes, marshes under various regimes and histories of tide restoration, and a severely tide-restrictedPhragmites australis marsh.Fundulus δ13C values were greater for fish from referenceSpartina marshes than for fish from adjacent tide-restricted or tide-restored marshes where higher percent cover of C3 plants, lower water column salinities, and more negative dissolved inorganic δ13C values were observed. The difference inFundulus δ13C values between a tide-restrictedPhragmites marsh and an adjacent referenceSpartina marsh was great compared to the difference between marshes at various stages of tide restoration and their respective reference marshes, suggesting that food web support functions are restored as the degree of tidal restriction is lessened. While a multiple isotopic approach can provide valuable information for determining specific food sources to consumers, this study demonstrates that monitoringFundulus δ13C values alone may be useful to evaluate the trajectory of ecological change for marshes undergoing tidal restoration.

The Impact of Biomedical Bleeding on Horseshoe Crab, Limulus polyphemus, Movement Patterns on Cape Cod, Massachusetts

The purpose of this study was to determine if bleeding, for biomedical purposes, influenced the behavior of horseshoe crabs, Limulus polyphemus. In the summer of 2001, ten bled and ten control (unbled) female horseshoe crabs were tracked for 26 days using acoustic telemetry in a small estuary on Cape Cod, Massachusetts. All but three crabs, two bled and one control, were located during the study period. No mortality was observed in the control group, while 20% mortality was observed within the bled group. There was no significant difference in the average rate of movement or in the spatial distribution within the estuary between the two groups. However, a difference was detected in the movement patterns. Horseshoe crabs from the bled group had a random direction of movement compared to the directional movement pattern of the control group, suggesting that the bled crabs experienced more disorientation.

The Effects of Integrated Marsh Management (IMM) on Salt Marsh Vegetation, Nekton, and Birds

An integrated marsh management (IMM) project in an urbanized watershed on Long Island, New York, USA, aimed to mitigate salt marsh degradation and to reduce mosquito production by an innovative combination of restoration and open marsh water management methods. The grid ditch network at two treatment marshes was replaced with naturalized tidal channels and ponds. Effects of the hydrologic alterations were monitored utilizing a before–after–control–impact approach. The treatment marshes experienced a number of beneficial outcomes including a fourfold reduction in the invasive Phragmites australis and increased native vegetation cover in the most degraded portions of the marsh, increased abundance and diversity of marsh killifish and estuarine nekton species, higher shorebird and waterfowl densities, and increased avian species diversity. The successful implementation of IMM concept led to improved marsh health and diminished mosquito production. Therefore, this study may serve as a template for similar large-scale integrated salt marsh restoration projects.

Effects of open marsh water management on numbers of larval salt marsh mosquitoes

ABSTRACT Open marsh water management (OMWM) is a commonly used approach to manage salt marsh mosquitoes than can obviate the need for pesticide application and at the same time, partially restore natural functions of grid-ditched marshes. OMWM includes a variety of hydrologic manipulations, often tailored to the specific conditions on individual marshes, so the overall effectiveness of this approach is difficult to assess. Here, we report the results of controlled field trials to assess the effects of two approaches to OMWM on larval mosquito production at National Wildlife Refuges (NWR). A traditional OMWM approach, using pond construction and radial ditches was used at Edwin B. Forsythe NWR in New Jersey, and a ditch-plugging approach was used at Parker River NWR in Massachusetts. Mosquito larvae were sampled from randomly placed stations on paired treatment and control marshes at each refuge. The proportion of sampling stations that were wet declined after OMWM at the Forsythe site, but not at the Parker River site. The proportion of samples with larvae present and mean larval densities, declined significantly at the treatment sites on both refuges relative to the control marshes. Percentage of control for the 2 yr posttreatment, compared with the 2 yr pretreatment, was >90% at both treatment sites.

Integrated Marsh Management (IMM): a new perspective on mosquito control and best management practices for salt marsh restoration

Salt marsh management often embraces diverse goals, ranging from the restoration of degraded marshes through re-introduction of tidal flow to the control of salt marsh mosquito production by altering marsh surface topography through Open Water Marsh Management (OMWM). However, rarely have these goals been incorporated in one project. Here we present the concept of Integrated Marsh Management (IMM), which combines the best management practices of salt marsh restoration and OMWM. Although IMM offers a comprehensive approach to ecological restoration and mosquito control, research evaluating this concept’s practical implementations has been inadequate. A long-term IMM project at Wertheim National Wildlife Refuge located in a highly urbanized watershed on Long Island, New York, USA was designed to fill this knowledge gap. A combination of restoration and OMWM techniques was employed at two treatment marshes, the results monitored before and after alterations, and compared to two adjacent control marshes. The treatment marshes experienced decreased mosquito production, reduced cover of the invasive common reed (Phragmites australis), expansion of native marsh vegetation, increased killifish and estuarine nekton species abundance, as well as increased avian species diversity and waterbird abundance. This demonstration project validated the IMM conceptual approach and may serve as a case study for similar IMM projects in the future.

A Method to Quantitatively Sample Nekton in Salt-Marsh Ditches and Small Tidal Creeks

Abstract We designed a novel gear to quantitatively sample nekton (free-swimming fish and crustaceans) from salt-marsh ditches and small tidal creeks. This gear, the ditch net, is portable and inexpensive to manufacture, and many replicate samples can be simultaneously collected. The ditch net can sample ditches and tidal creeks as narrow as 25 cm and up to 1 m wide (or wider if the design is modified). The net is suspended between four stakes and covers a 1-m length of ditch bottom. To sample nekton, the mesh doors on both ends of the ditch net are raised, thus enclosing a known area of water and trapping nekton within the net. Catch efficiency of the ditch net was comparable with the actual density of fish traversing the ditch as estimated from video data. Recovery efficiency of the gear was high (99%), indicating that fish rarely escape after the net is triggered. A power analysis indicated that a sample size of 20 provided good power (>0.80 at an alpha level of 0.05) to detect temporal or site differe...

Selected hemolymph constituents of captive, biomedically bled, and wild caught adult female American horseshoe crabs (Limulus polyphemus)

Hemolymph from adult female American horseshoe crabs (Limulus polyphemus) was analyzed from wild caught and three treatments from a biomedical bleeding experiment: captive control, captive bled, and handled according to Best Management Practices (BMP). A total of 10 constituents were measured: blood urea nitrogen, creatinine, glucose, lactate, protein, and ionic concentrations of calcium, chloride, magnesium, potassium, and sodium. Protein concentration was positively correlated with size (prosomal width), while sodium and potassium were negatively correlated with size. Only protein concentration differed among groups, with the captive bled BMP group having significantly lower protein values than either captive control or wild crabs. Wild crabs had higher creatinine, glucose, and potassium values compared to all captive groups. Chloride, calcium, magnesium, and sodium concentrations were lower for wild crabs compared to the captive groups. Lower protein values in the captive bled BMP group suggest that prolonged biomedical bleeding may impact crab physiology.

Ecological Thresholds for Salt Marsh Nekton and Vegetation Communities

Salt marsh vegetation and nekton respond to stressors in estuarine systems, providing ideal indicators of change. Here we characterize the structure of these communities along a gradient of anthropogenic stress (e.g., human population size of watersheds, degree of hydrological alteration of marshes), identify ecological thresholds that are linked to community condition, and provide potential decision thresholds for land managers based on an evaluation of community condition. Salt marsh nekton and vegetation community data (species composition and abundance) were compiled from over 180 discrete data sets from marshes along the Atlantic coast from Maine to Virginia. Using multivariate techniques (e.g., Principal Component Analysis, Canonical Correspondence Analysis, Analysis of Similarities), patterns of community change along a gradient of hydrologic impact and degree of watershed development were elucidated. Several levels of community complexity, individual species’ abundances, and relative abundances of life history-based groups were used to identify potential metrics for ecological thresholds. The nekton community displayed shifts in community structure along a gradient of human population size (e.g., anthropogenic stress gradient) in surrounding watersheds, from resident fish-dominated communities at marshes in watersheds with low human populations to shrimp-dominated communities (Palaemonidae species) in watersheds with high human populations. Vegetation communities from reference (relatively hydrologically undisturbed) marshes were dominated by obligate halophytes (e.g., salt meadow grasses) with low proportions of invasive plants. Impacted (e.g., tidally restricted) marshes had fewer halophytic obligate wetland plants, more facultative wetland plant species, and higher proportions of invasive species. Shifts in characteristics of nekton and vegetation communities toward the impacted state can be used as ecological thresholds upon which decision thresholds for land managers can be based. For example, detection of declining proportions of killifish and transient fish and increasing proportions of Palaemonidae shrimp (the ecological threshold metrics), would indicate a community changing from moderate to poor condition (the decision threshold), thereby triggering management actions. Ecological thresholds are presented for both nekton and vegetation communities and are presented in the context of a desired resource goal (good, moderate, poor condition) that can be used by resource managers to evaluate responses to restoration activities or the overall condition of the marsh community. Findings from this study are most directly relevant to northeastern US salt marshes, but the methods used to derive the ecological threshold metrics can be applied to other regions.