Reference Marshes Research Articles

Factors influencing blue carbon accumulation across a 32‐year chronosequence of created coastal marshes

AbstractSaline coastal marshes are blue carbon ecosystems with relatively high soil carbon (C) stocks and high rates of soil C accumulation. Loss of saline wetlands due to relative sea‐level rise, land‐use change, and hydrologic alterations liberates previously stored C and reduces the capacity for future C sequestration. Widespread wetland loss has prompted marsh restoration and creation projects around the world; however, little is known about the timescale and capacity for created marshes to function as blue C sinks and the role of environmental conditions in mediating soil C accumulation in restoration sites. Using a chronosequence of five created saline marshes ranging in age from 5 to 32 yr and two adjacent natural reference marshes in southwest Louisiana, USA, short‐ and longer‐term C accumulation rates (SCAR and LCAR, respectively) were determined using feldspar marker horizons and peat depth in cores at six locations in each marsh. Created marshes ranged in elevation from −12 to 41 cm (NAVD88) and supported assorted plant community compositions driven by local environmental conditions. SCAR ranged from 75 to 430 g C·m−2·yr−1, which were comparable in the two youngest and two oldest marshes. Longer‐term CAR ranged from 18 to 99 g C·m−2·yr−1 but did not significantly differ among marshes of different ages. Our findings indicate that LCAR in these created marshes were influenced by site‐specific environmental conditions (i.e., stem density and mineral sediment) rather than marsh age. Results suggest that conditions appropriate for the establishment of vegetation with high stem densities, such as Distichlis spicata and Spartina patens, may facilitate higher LCAR in created marshes, which may be useful for restoration project planning and mitigation of climate change.

The Potential Resiliency of a Created Tidal Marsh to Sea Level Rise

Abstract. The purpose of this study was to determine the elevation dynamics of a created tidal marsh on the North Carolina coast. Deep rod surface elevation tables (RSET) and feldspar marker horizons (MH) were installed in plots to measure net surface elevation changes and to quantify contributing processes. Twelve total plots were placed on four elevation gradient transects (three transects within the created marsh and one within a reference marsh), with three plots along each transect. Elevation gradient transects included a low marsh plot dominated by , a middle marsh plot dominated by , and a high marsh plot dominated by . RSET and MH were measured in December 2012, January 2014, April 2017, and March 2018. Elevation change ranged from 1.0 to 4.0 mm year-1 within the created marsh and from -0.4 to 2.0 mm year-1 within the reference marsh. When compared to the long-term linear trend in local relative sea level rise (RSLR) of 3.10 ±0.35 mm year-1, the middle marsh plots within the created marsh trended toward survival, with an observed elevation increase of 3.1 ±0.2 mm year-1. Alternatively, the low and high marsh plots within the created marsh trended toward submergence, with observed elevation increases of 2.1 ±0.2 and 1.3 ±0.2 mm year-1, respectively. These results indicate that a created marsh can display elevation dynamics similar to a natural marsh and can be resilient to current rates of RSLR if constructed with a high elevation capital. Surface elevation changes were observed over a short time period and in a relatively young marsh, so it is uncertain if these trends will continue or how the long-term relation with RSLR will develop. While this study provided initial data on the ability of created tidal marshes to respond to observed sea level rise, subsequent observations are needed to evaluate the long-term elevation dynamics. Keywords: Resiliency, Sea level rise, Surface elevation tables, Tidal marsh, Vertical accretion.

Rhizosphere Microbial Communities of Spartina alterniflora and Juncus roemerianus From Restored and Natural Tidal Marshes on Deer Island, Mississippi.

The U. S. Gulf of Mexico is experiencing a dramatic increase in tidal marsh restoration actions, which involves planting coastal areas with smooth cordgrass (Spartina alterniflora) and black needlerush (Juncus roemerianus) for erosion control and to provide habitat for fish and wildlife. It can take decades for sedimentary cycles in restored marshes to approach reference conditions, and the contribution of the sediment microbial communities to these processes is poorly elucidated. In this study, we addressed this gap by comparing rhizosphere microbiomes of S. alterniflora and J. roemerianus from two restored marshes and a natural reference marsh located at Deer Island, MS. Our results revealed that plants from the restored and reference areas supported similar microbial diversity indicating the rapid colonization of planted grasses with indigenous soil microbiota. Although close in composition, the microbial communities from the three studied sites differed significantly in the relative abundance of specific taxa. The observed differences are likely driven by the host plant identity and properties of sediment material used for the creation of restored marshes. Some of the differentially distributed groups of bacteria include taxa involved in the cycling of carbon, nitrogen, and sulfur, and may influence the succession of vegetation at the restored sites to climax condition. We also demonstrated that plants from the restored and reference sites vary in the frequency of culturable rhizobacteria that exhibit traits commonly associated with the promotion of plant growth and suppression of phytopathogenic fungi. Our findings will contribute to the establishment of benchmarks for the assessment of the outcome of coastal restoration projects in the Gulf of Mexico and better define factors that affect the long-term resiliency of tidal marshes and their vulnerability to climate change.

Recovery of Salt Marsh Invertebrates Following Habitat Restoration: Implications for Marsh Restoration in the Northern Gulf of Mexico

Recovery following salt marsh restoration in the northern Gulf of Mexico is investigated using meta-analysis for two salt marsh indicator invertebrates, the periwinkle snail (Littoraria irrorata) and amphipod crustaceans (Amphipoda). These invertebrates serve key marsh ecosystem functions including facilitating nutrient cycling and serving as prey for larger ecologically and economically important species. Recovery of periwinkles in restored marshes compared to reference sites is quantified by progression in population density and, because the species is long-lived (~ 10 years), in terms of biomass added per unit area each year following restoration. Amphipods are shorter-lived with high annual turnover; thus, recovery through time is estimated by the density of individuals rather than by biomass. The results of the analyses indicate progressive periwinkle recovery to equivalence with reference systems by year 4 in terms of density and year 6 with respect to annual biomass addition, while amphipod densities do not fully recover in the first 20 years following restoration. Although periwinkle recovery in terms of annual biomass addition reaches equivalence by year 6, the development of an age class structure characteristic of reference marshes would likely take longer because of the relatively long lifespan for this species. In addition to providing insight into the benefits of salt marsh restoration in the northern Gulf of Mexico, the approach described can be applied more generally to restoration scaling in a natural resource damage assessment context.

Nitrous oxide emissions could reduce the blue carbon value of marshes on eutrophic estuaries

The supply of nitrogen to ecosystems has surpassed the Earth’s Planetary Boundary and its input to the marine environment has caused estuarine waters to become eutrophic. Excessive supply of nitrogen to salt marshes has been associated with shifts in species’ distribution and production, as well as marsh degradation and loss. Our study of salt marshes in agriculturally intensive watersheds shows that coastal eutrophication can have an additional impact. We measured gas fluxes from marsh soils and verified emissions of nitrous oxide (N2O) in nitrogen-loaded marshes while the reference marsh was a sink for this gas. Salt marsh soils are extremely efficient carbon sinks, but emissions of N2O, a greenhouse gas 298 times more potent than CO2, reduces the value of the carbon sink, and in some marshes, may counterbalance any value of stored carbon towards mitigation of climate change. Although more research is merited on the nitrogen transformations and carbon storage in eutrophic marshes, the possibility of significant N2O emissions should be considered when evaluating the market value of carbon in salt marshes subject to high levels of nitrogen loading.

Enhanced invertebrate prey production following estuarine restoration supports foraging for multiple species of juvenile salmonids (Oncorhynchus spp.)

Estuaries provide crucial foraging resources and nursery habitat for threatened populations of anadromous salmon. As such, there has been a global undertaking to restore habitat and tidal processes in modified estuaries. The foraging capacity of these ecosystems to support various species of out‐migrating juvenile salmon can be quantified by monitoring benthic, terrestrial, and pelagic invertebrate prey communities. Here, we present notable trends in the availability of invertebrate prey at several sites within a restoring large river delta in Puget Sound, Washington, U.S.A. Three years after the system was returned to tidal influence, we observed substantial additions to amphipod, copepod, and cumacean abundances in newly accessible marsh channels (from 0 to roughly 5,000–75,000 individuals/m2). In the restoration area, terrestrial invertebrate colonization was dependent upon vegetative cover, with dipteran and hymenopteran biomass increasing 3‐fold between 1 and 3 years post‐restoration. While the overall biodiversity within the restoration area was lower than in the reference marsh, estimated biomass was comparable to or greater than that found within the other study sites. This additional prey biomass likely provided foraging benefits for juvenile Chinook, chum, and coho salmon. Primary physical drivers differed for benthic, terrestrial, and pelagic invertebrates, and these invertebrate communities are expected to respond differentially depending on organic matter exchange and vegetative colonization. Restoring estuaries may take decades to meet certain success criteria, but our study demonstrates rapid enhancements in foraging resources understood to be used for estuary‐dependent wildlife.

Bottom‐up control of parasites

AbstractParasitism is a fundamental ecological interaction. Yet we understand relatively little about the ecological role of parasites compared to the role of free‐living organisms. Bottom‐up theory predicts that resource enhancement will increase the abundance and biomass of free‐living organisms. Similarly, parasite abundance and biomass should increase in an ecosystem with resource enhancement. We tested this hypothesis in a landscape‐level experiment in which salt marshes (60,000 m2 each) received elevated nutrient concentrations via flooding tidal waters for 11 yr to mimic eutrophication. Nutrient enrichment elevated the densities of the talitrid amphipod, Orchestia grillus, and the density and biomass of its trematode parasite, Levinseniella byrdi. Strikingly, L. byrdi prevalence increased over time, up to 13 times higher in nutrient‐enriched marshes (30%) relative to the mean prevalence in reference marshes (2.4%). The biomass density of infected amphipods was, on average, 11 times higher in nutrient‐enriched marshes (1.1 kg/ha) than in reference marshes (0.1 kg/ha), when pooling across all years. Orchestia grillus biomass comprises 67% of the arthropod community biomass; thus, nutrient enrichment elicits a substantial surge in parasitized biomass in the arthropod community. If our results are typical, they suggest that eutrophication can increase parasite abundance and biomass with chronic resource enhancement. Therefore, minimizing aquatic nutrient pollution may prevent outbreaks of parasites with aquatic hosts.

Carbon and nitrogen storage of a restored wetland at Illinois’ Emiquon Preserve: potential for carbon sequestration

Conversion of wetlands to croplands results in the release of a significant amount of carbon (C) from soil organic matter (SOM) into the atmosphere. Restoring wetlands from croplands has C sequestration potential. The overall goal of our study was to quantify C and N storage of a restored wetland at the Emiquon Preserve, and examine its potential for C sequestration by comparing its C storage with C storage of reference natural wetlands in Illinois. Samples of plants and soils at the restored wetland and four reference wetland sites were collected in 2009 and 2011, respectively. We found that ecosystem storage of organic C (OC) and total N (TN) of the restored wetland was 38.29 Mg C ha−1 and 2.43 Mg N ha−1, respectively. For the reference sites, the average ecosystem storage of OC for sedge meadow and marsh was higher at 136.63 and 52.04 Mg C ha−1, respectively. The soil OC (SOC) storage of the restored wetland was only about 25% of SOC storage of reference sedge meadow sites and 46% of reference marsh site, suggesting that the restored wetland at Emiquon has the potential to sequester a large amount of additional C in the future.

Urban Land use Affects Resident Fish Communities and Associated Salt Marsh Habitat in Alabama and West Florida, USA

Urban land-use has been shown to impact aquatic environments however not much is known about the effects of low to medium density residential development. Fish and associated habitat were sampled along 23 salt marshes (dominated by Juncus roemerianus) across three urban and three reference tidal creeks of Alabama and west-Florida. Reference creeks had very little surrounding development while urban creeks were surrounded by residential neighborhoods typical for the region. Fish were sampled seasonally for one year along the marsh-water edge using baited minnow traps. Tidal creeks and marsh edges were also surveyed for various environmental attributes including: marsh species composition, stem density and biomass, sediment contaminants, marsh slope, salinity, and water temperature. Urban creeks showed evidence of longer freshwater conditions and greater salinity fluctuation. Total fish abundance and biomass were significantly lower in urban marshes (10.1 ± 1.3 fish trap−1 and 34.8 ± 5.1 g trap−1) compared to reference marshes (14.3 ± 1.8 fish trap−1 and 77.4 ± 10.0 g trap−1). Based on nonmetric multidimensional scaling (NMDS), urban and reference fish assemblages were clearly clustered and correlated with salinity, marsh slope and sediment Cd concentration. These results suggest that marshes in urban-residential tidal creeks may support modified habitats compared to undeveloped creeks.

Response of salt marshes to oiling from the Deepwater Horizon spill: Implications for plant growth, soil surface-erosion, and shoreline stability

We investigated the initial impacts and post spill recovery of salt marshes over a 3.5-year period along northern Barataria Bay, LA, USA exposed to varying degrees of Deepwater Horizon oiling to determine the effects on shoreline-stabilizing vegetation and soil processes. In moderately oiled marshes, surface soil total petroleum hydrocarbon concentrations were ~70mgg−1 nine months after the spill. Though initial impacts of moderate oiling were evident, Spartina alterniflora and Juncus roemerianus aboveground biomass and total live belowground biomass were equivalent to reference marshes within 24–30months post spill. In contrast, heavily oiled marsh plants did not fully recover from oiling with surface soil total petroleum hydrocarbon concentrations that exceeded 500mgg−1 nine months after oiling. Initially, heavy oiling resulted in near complete plant mortality, and subsequent recovery of live aboveground biomass was only 50% of reference marshes 42months after the spill. Heavy oiling also changed the vegetation structure of shoreline marshes from a mixed Spartina–Juncus community to predominantly Spartina; live Spartina aboveground biomass recovered within 2–3years, however, Juncus showed no recovery. In addition, live belowground biomass (0–12cm) in heavily oiled marshes was reduced by 76% three and a half years after the spill. Detrimental effects of heavy oiling on marsh plants also corresponded with significantly lower soil shear strength, lower sedimentation rates, and higher vertical soil-surface erosion rates, thus potentially affecting shoreline salt marsh stability.

Interactions between soil physicochemistry and belowground biomass production in a freshwater tidal marsh

The success of tidal freshwater wetland restoration is typically gauged by the re-establishment of characteristics found in reference marshes. Although plant species composition may resemble reference marshes within a few years after the initiation of restoration, return of soil physicochemical properties may take much longer. We investigated soil characteristics in a post-levee breach freshwater tidal marsh restoration site (Liberty Island, California), and the impacts of soil compaction on the survival and growth of emergent macrophytes. In a field study, we examined soil physicochemical properties throughout 50-cm deep soil cores collected from locations at Liberty Island that differed in location and stage of vegetation colonization. In a controlled mesocosm study, we subjected three species that are commonly implemented in restoration plantings (Schoenoplectus acutus, S. californicus, and Typha latifolia) to two levels of soil compaction (control and high soil bulk density) to determine the influence of soil compaction on soil physicochemical properties and macrophyte response. Belowground biomass increased and soil bulk density decreased with time since vegetation colonization. The controlled study showed that both Schoenoplectus species exhibited greater survival than T. latifolia. The species explored are capable of ameliorating compacted soil conditions over time; this ability can facilitate the re-establishment of wetland structure and function at restoration sites.

Predicting the number, orientation and spacing of dike breaches for tidal marsh restoration.

Abstract Tidal channels are structurally and functionally prominent features in tidal marshes, so their restoration is central to tidal marsh habitat restoration. Consequently, an important question in tidal marsh restoration is how many tidal channels can a restoration site support, and thus, how many dike breaches should be made to restore tidal inundation and tidal channels, if the dike is not to be removed entirely. Allometric analysis of reference tidal marshes in Puget Sound river deltas and the lower Columbia River Estuary showed that channel outlet count scales with marsh area, and that completed and proposed tidal marsh restoration projects had 5-fold fewer channel outlets than reference marshes. This deficiency likely impacts fish access to the restoration sites. After addressing the question of tidal channel outlet count, or dike breach count, the next design questions are how should dike breaches be oriented in tidal marsh islands and how should they be spaced. GIS and statistical analysis of reference marsh islands indicated that outlets of the two largest tidal channels draining a marsh island are typically oriented downstream, in parallel with the nearest river channel. However, the outlets of smaller tidal channels are oriented randomly. Tidal channel outlet spacing is generally independent of site size and constant within a river delta. Geometric mean spacing ranged from 122 m in the Snohomish Delta to 280 m in the North Fork Skagit Delta. These results provide important guidance to improve tidal marsh restoration design, and illustrate a useful approach to restoration design evaluation.

Salinization during salt-marsh restoration after managed realignment

Salt marshes provide an important and unique habitat for plants and animals. To restore salt marshes, numerous coastal realignment projects have been carried out, but restored marshes often show persistent ecological differences from natural marshes. We evaluate the effects of elevation and marsh topography, which are in turn affected by drainage and livestock grazing, on soil salinity after de-embankment. Salinity in the topsoil was monitored during the first 10 years after de-embankment and compared with salinity in an adjacent reference marsh. Additionally, salinity at greater depths (down to 1.2 m below the marsh surface) was monitored during the first 4 years by measuring the electrical conductivity of the groundwater. Chloride concentration in the top soil strongly decreased with increasing elevation; however, it was not affected by marsh topography, i.e. distance to creek or breach. Chloride concentrations higher than 2 g Cl−/litre were found at elevations below 0.6 m + MHT. Salinization of the groundwater, however, took several years. At low marsh elevations, the salinity of the deep groundwater (at 1.2 m depth) increased slowly throughout the full 4-year period of monitoring but did not reach the level of seawater. Compared to the ungrazed treatment, the grazed treatment led to lower accretion rates, lower soil-moisture content and higher chloride content of soil moisture. The de-embankment of the agricultural grasslands resulted in a rapid increase of soil salinity, although deeper ground-water levels showed a much slower response. Elevation accounted for most of the variation in the salinization of the soil. Grazing may enhance salinity of the top soil.

Differences in tidal channel network geometry between reference marshes and marshes restored by historical dike breaching

Tidal marsh restoration generally involves dike breaching rather than complete dike removal to restore tidal inundation. Dike removal more completely restores hydrodynamic processes, but dike breaching is more economical. Thus, without a clear demonstration of the ecological benefits of complete or extensive dike removal, economic considerations are likely to cause restoration planners and engineers to prefer dike breaching. To provide some insight into the relative benefit of dike breaching versus dike removal, tidal channel planform geometry was compared between historical dike breach sites (>15 years old) and reference tidal marsh. Tidal channel networks were examined because they mediate many hydrodynamic, sedimentary, and ecological processes. Dike breach sites were found to have fewer tidal channel outlets than reference sites, but greater total channel surface area and length. These differences were likely the result of remnant dikes constraining tidal prism entirely to channel networks rather than allowing a portion of the prism to transit site boundaries as sheet flow. Allometric analysis of GIS-calculated tidal channel drainage basin area relative to total marsh area indicated the proportion of tidal prism comprised of sheet flow was inversely related to total marsh area, with the smallest marsh islands having no tidal channels and all of their tidal prism consisting of sheet flow. This suggests dike removal to restore sheet flow is most important for small restoration projects. However, dike removal may still be important for large restoration sites depending on issues not examined in this paper, e.g., remnant dike effects on river flood hydrodynamics.

Utilisation of a coastal grassland by geese after managed re-alignment

In this study we evaluate the effect of coastal re-alignment on the utilisation of coastal grasslands by staging geese. We assessed vegetation change and utilisation by geese using repeated mapping and regular dropping counts in both the restored marsh and adjacent reference sites. All measurements were started well before the actual re-alignment. In addition, we studied the effects of livestock grazing on vegetation and geese, using exclosures. The vegetation transformed from fresh grassland into salt-marsh vegetation. A relatively large proportion of the de-embanked area became covered with secondary pioneer vegetation, and the overall cover of potential food plants for geese declined. Goose utilisation had initially dropped to low levels, both in autumn and in spring, but it recovered to a level comparable to the reference marsh after ten years. Exclosure experiments revealed that livestock grazing prevented the establishment of closed swards of grass in the poorly drained lower area of the restored marsh, and thereby negatively affected goose utilisation of these areas during spring staging. Goose grazing in the restored marsh during spring showed a positive numerical response to grass cover found during the preceding growing season. (1) The value of restored salt marsh as foraging habitat for geese initially decreased after managed re-alignment but recovered after ten years. (2) Our findings support the idea that the value of foraging habitats depends largely on the cover of forage plants and that this can be manipulated by adjusting both grazing and drainage.

Limited Vegetation Development on a Created Salt Marsh Associated with Over-Consolidated Sediments and Lack of Topographic Heterogeneity

Restored salt marshes frequently lack the full range of plant communities present on reference marshes, with upper marsh species underrepresented. This often results from sites being too low in the tidal frame and/or poorly drained with anoxic sediments. A managed coastal realignment scheme at Abbotts Hall, Essex, UK, has oxic sediments at elevations at which upper marsh communities would be expected. But 7 years after flooding, it continued to be dominated by pioneer communities, with substantial proportions of bare ground, so other factors must hinder vegetation development at these elevations. The poorly vegetated areas had high sediment shear strength, low water and organic carbon content and very flat topography. These characteristics occur frequently on the upper parts of created marshes. Experimental work is required to establish causal links with the ecological differences, but other studies have also reported that reduced plant β-diversity and lower usage by fish are associated with topographic uniformity. Uniformity also leads to very different visual appearance from natural marshes. On the upper intertidal, sediment deposition rate are slow, water velocities are low and erosive forces are weak. So, topographic heterogeneity cannot develop naturally, even if creeks have been excavated. Without active management, these conditions will persist indefinitely.

Concentrations and geochemical fractions of rare earth elements in two different marsh soil profiles at the North Sea, Germany

The purpose of this study was (1) to determine the vertical distribution of rare earth element (REE) concentrations, stocks, and geochemical fractions in two different marsh soil profiles and (2) to quantify the relations between REEs and soil properties. A sandy Fluvisol recently flooded by tidal water and a clayey Gleysol landward the dike impacted by fluctuating groundwater levels served as reference marsh soils. An aqua regia extraction was used to determine the concentrations of REEs; additionally, a sequential extraction procedure developed by the Commission of the European Communities Bureau of Reference was conducted to assess the geochemical fractions (exchangeable, reducible, oxidisable, residual fraction) of REEs. Both extractions were carried out according to genetic horizons. The stocks of REEs were calculated and the relations between physico-chemical soil properties and concentrations/mobility of REEs were quantified via correlation analysis. The aqua regia extractable REE concentrations and stocks of the Gleysol were about two times higher compared to the Fluvisol since the Gleysol was more clayey and REEs might adsorb onto clay minerals. We have detected small differences of REE concentrations and geochemical fractions between the horizons of the single profiles. Rare earth elements existed mainly in residual or reducible fraction, followed by oxidisable, and water soluble/exchangeable/carbonate bound fraction. The most striking difference between the two marsh soil profiles regarding the geochemical fractions was the higher residual fraction in the Fluvisol than in the Gleysol what seemed to be due to the lower aqua regia extractable concentration in the former. The aqua regia extractable concentration as well as reduction and oxidation processes of (amorphous) iron and manganese complexes seemed to have the most important impact on the geochemical fractions of REEs in the studied marsh soil profiles. In future, those findings should be verified in further marsh soils worldwide. In particular, future studies should elucidate the specific release kinetics of REEs and their determining factors.

Macroinvertebrate Prey Availability and Fish Diet Selectivity in Relation to Environmental Variables in Natural and Restoring North San Francisco Bay Tidal Marsh Channels

Tidal marsh wetlands provide important foraging habitat for a variety of estuarine fishes. Prey organisms include benthic–epibenthic macroinvertebrates, neustonic arthropods, and zooplankton. Little is known about the abundance and distribution of interior marsh macroinvertebrate communities in the San Francisco Estuary (estuary). We describe seasonal, regional, and site variation in the composition and abundance of neuston and benthic–epibenthic macroinvertebrates that inhabit tidal marsh channels, and relate these patterns to environmental conditions. We also describe spatial and temporal variation in diets of marsh-associated inland silverside, yellowfin goby, and western mosquitofish. Fish and invertebrates were sampled quarterly from October 2003 to June 2005 at six marsh sites located in three river systems of the northern estuary: Petaluma River, Napa River, and the west Delta. Benthic/epibenthic macroinvertebrates and neuston responded to environmental variables related to seasonal changes (i.e., temperature, salinity), as well as those related to marsh structure (i.e., vegetation, channel edge). The greatest variation in abundance occurred seasonally for neuston and spatially for benthic–epibenthic organisms, suggesting that each community responds to different environmental drivers. Benthic/epibenthic invertebrate abundance and diversity was lowest in the west Delta, and increased with increasing salinity. Insect abundance increased during the spring and summer, while Collembolan (springtail) abundance increased during the winter. Benthic/epibenthic macroinvertebrates dominated fish diets, supplemented by insects, with zooplankton playing a minor role. Diet compositions of the three fish species overlapped considerably, with strong selection indicated for epibenthic crustaceans—a surprising result given the typical classification of Menidia beryllina as a planktivore, Acanthogobius flavimanus as a benthic predator, and Gambusia affinis as a larvivorous surface-feeder. Fish diets were influenced by position along the estuarine gradient and season. Overall, our data show that local-scale site effects and marsh position within the estuary influence invertebrate community composition and abundance. Additionally, we show that restoring marsh ecosystems can subsidize fishes similarly to reference marshes. We, thus, recommend that managers focus on the ability of restoring marshes to produce food subsidies for target species when planning and designing tidal marsh restoration projects, especially those targeted for food web support.

White perch Morone americana (Gmelin, 1789) habitat choice and movements: Comparisons between Phragmites-invaded and Spartina reference marsh creeks based on acoustic telemetry

An investigation of the effects of the Phragmites invasion on movements and habitat use focused on ultrasonic telemetry of white perch (Morone americana) throughout Alloway Creek, Delaware Bay, New Jersey. Of the individuals tracked (192–266mm FL), there was high site fidelity (19 out of 30 individuals) but there was also variability in movement patterns, home range size, and habitat use. On average, individual fish spent most of their time stationary (67%), and substantially less time moving (22%) and tended to move up creek with flooding tides, and down creek with ebbing tides. Higher movement levels occurred at mid-ebb and mid-flood stages when water velocity was at its highest. Eighteen individuals had tidal excursions — either long distance movements with the tide or excursions onto the marsh surface or into shallow creeks at high tide. Individuals originally tagged in Spartina creeks tended to utilize only Spartina areas (12/13 tagged fish stayed in Spartina), whereas none of the individuals tagged in Phragmites creeks stayed in Phragmites areas (0 out of 5 tagged fish). These results suggest that the tagged individuals did not prefer Phragmites habitats. Further, this study indicates that it is important to consider animal behavior such as movement patterns, home range area and habitat use when evaluating the effectiveness of restoration programs. Such measures can provide insight into why altered habitats differ from reference sites in terms of quality, identify critical resources for animals and enhance our understanding of how animals contribute to ecosystem function.

Acute Effects of Drought on Emergent and Aquatic Communities in a Brackish Marsh

Plants and animals in brackish marshes are adapted to live within a wide, yet finite, range of conditions. Events that shift the environmental state beyond that range can dramatically alter habitats and, potentially, the numerous ecosystem services they provide. A prolonged exceptional drought in Texas (October 2010–January 2012) provided a unique opportunity to understand how brackish wetland habitats respond to an extreme environmental event. We examined marshes in the Lower Neches Wildlife Management Area (Texas, USA) that fell within the drought affected area, including restored areas and an adjacent reference marsh. To test our hypothesis that the brackish marsh community would be sensitive to drought conditions, we quantified emergent plant and submerged aquatic vegetation (SAV) and animal (invertebrates, fish) characteristics in summer 2010 and 2011. In spite of its severity, the exceptional drought of 2011 did not have a negative impact on emergent plant communities: biomass, stem density, and chlorophyll a concentrations were the same in pre-drought and drought years in all restored and reference areas. In contrast, SAV biomass was reduced by up to 100 % in the drought year. Some fish and invertebrate densities were also reduced by an order of magnitude or more, possibly due to the loss of SAV. Aquatic faunal species composition was markedly different in the drought year, largely due to the loss of the hydrobiid snail Probythinella protera and the gain of some marine species, including Gulf menhaden (Brevoortia patronus), brown shrimp (Farfantepenaeus aztecus), and white shrimp (Litopenaeus setiferus). By altering aquatic the plant and animal community, this drought event may subsequently reduce trophic support for higher consumers, or contribute to a decline in water quality. Restoration monitoring programs that only focus on relatively stress-resistant, emergent wetland plant communities may underestimate the sensitivity of these ecosystems to extreme environmental events like droughts.