Californian Salt-Marsh Vegetation: An Improved Model of Spatial Pattern

Although tidal wetland vegetation patterns are typically related to elevation, we hypothesized that the vertical range of a species may shift where the topography is more heterogeneous. We examined plant species occurrences in relation to elevation, proximity to the bay, and proximity to tidal creeks at a near-pristine wetland in San Quintín Bay, Baja California, Mexico. At the whole-wetland scale, most species occurred primarily within a 30-cm elevation band (the marsh plain). However, Spartina foliosa occurred only at the bayward margin, even though “suitable” elevations were present further inland. A similar pattern was found in San Diego Bay. At the microtopographic scale, three species on the marsh plain were strongly influenced by elevation, whereas four species responded to both elevation and proximity to tidal creeks. The latter species tended to “avoid” the lower 10 cm of the marsh plain except near a tidal creek. Species richness was thus greater (by 0.6 species at the lowest 10-cm class) at the tidal creek margin. Better drainage near creeks is the hypothesized cause. Our results help explain why species that are transplanted to constructed wetlands do not always grow at the full range of elevations they occupy in natural wetlands. We recommend that species be introduced to their modal elevation (determined from nearby reference marshes) and that salt-marsh construction designs include topographic heterogeneity (complex tidal creek networks). The analysis of broad-scale and fine-scale patterns of occurrence also suggests new habitat nomenclature. Elevation-based terms (“low,”“middle,” and “high” marsh) should be replaced by a system that considers elevation, landscape position, and conspicuous species. We suggest three habitat designations: (a) the high marsh—a 30- to 70-cm elevation range with Salicornia subterminalis; (b) the marsh plain—a 30-cm elevation range with heterogeneous topography and up to nine common species; and (c) cordgrass habitat—the bayward portion of the marsh plain and lower elevations, all occupied by Spartina foliosa. Although these habitats do not have discrete boundaries, separate terms are needed for wetland restoration plans and these designations will improve recognition that vegetation patterns respond to horizontal, as well as vertical, position.     

Fish community responses to ecosystem stressors in coastal estuarine wetlands: a functional basis for wetlands management and restoration

Functional responses of estuarine fish species to environmental perturbations such as wetland impoundment, changes in water quality, and sediment accretion are investigated. The study focuses on the feeding, growth and habitat use by California killifish (Fundulus parvipinnis), topsmelt (Antherinops affinis), and juvenile California halibut (Paralichthys californicus) in impacted coastal wetlands to provide an ecological basis for guidance on the management and restoration of these ecosystems. The ecology of California killifish, Fundulus parvipinnis, is closely tied with the marsh surface, which they access at high tide to feed and grow. Field estimates of food consumption show that killifish can increase their food intake by two-fold to five-fold by adding marsh surface foods to their diet. Bioenergetics modeling predicts that killifish can grow over an order of magnitude faster if they add intertidal marsh surfaces to their subtidal feeding areas. Tidal inlet closures and increased marsh surface elevations due to sediment accretion can restrict killifish access to the marsh surface, affecting its growth and fitness. An open tidal inlet and tidal creek networks that allow killifish to access the marsh at high tide must be incorporated into the restoration design. Topsmelt and California halibut are also adversely affected by tidal inlet closures. Food consumption rates of topsmelt are 50% lower when the tidal inlet is closed, compared to when the estuary is tidally-flushed. Tidal inlet closures inadvertently induce variations in water temperature and salinity and negatively affect growth of juvenile California halibut. Tidal creek networks which consist of channels and creeks of various orders are also important to halibut. Large halibut (>200 mm TL) inhabit deeper, high order channels for thermal refuge, while small halibut (<120 mm TL) are abundant in lower order channels where they can feed on small-sized prey which are typically less abundant in high order channels. Maintaining an open tidal inlet, implementing sediment management programs and designing coastal wetlands with tidal creek networks adjacent to intertidal salt marsh habitat (for fish access) are key elements that need to be considered during the planning and implementation of coastal wetland restoration projects.     

Tidal marsh plant responses to elevated CO2, nitrogen fertilization,and sea level rise

Elevated CO₂ and nitrogen (N) addition directly affect plant productivity and the mechanisms that allow tidal marshes to maintain a constant elevation relative to sea level, but it remains unknown how these global change drivers modify marsh plant response to sea level rise. Here we manipulated factorial combinations of CO₂ concentration (two levels), N availability (two levels) and relative sea level (six levels) using in situ mesocosms containing a tidal marsh community composed of a sedge, Schoenoplectus americanus, and a grass, Spartina patens. Our objective is to determine, if elevated CO₂ and N alter the growth and persistence of these plants in coastal ecosystems facing rising sea levels. After two growing seasons, we found that N addition enhanced plant growth particularly at sea levels where plants were most stressed by flooding (114% stimulation in the + 10 cm treatment), and N effects were generally larger in combination with elevated CO₂ (288% stimulation). N fertilization shifted the optimal productivity of S. patens to a higher sea level, but did not confer S. patens an enhanced ability to tolerate sea level rise. S. americanus responded strongly to N only in the higher sea level treatments that excluded S. patens. Interestingly, addition of N, which has been suggested to accelerate marsh loss, may afford some marsh plants, such as the widespread sedge, S. americanus, the enhanced ability to tolerate inundation. However, if chronic N pollution reduces the availability of propagules of S. americanus or other flood‐tolerant species on the landscape scale, this shift in species dominance could render tidal marshes more susceptible to marsh collapse.     

Comparison of Nitrogen Fixation Activity in Tall and Short Spartina alterniflora Salt Marsh Soils

A comparison of the N₂ fixers in the tall Spartina alterniflora and short S. alterniflora marsh soils was investigated. Zero-order kinetics and first-order kinetics of acetylene reduction were used to describe the activity of the N₂ fixers in marsh soil slurries. It was found that the V_max values were approximately 10 times greater for the N₂ fixers in the tall Spartina than in the short Spartina marsh when raffinose was used as the energy source. In addition, the (K_s + S_n) values were approximately 4 to 15 times lower for the N₂ fixers in the tall Spartina than in short Spartina marsh. First-order kinetics of nitrogen fixation for several substrates indicate that the N₂ fixers in the tall Spartina marsh were two to seven times more active than those in the short Spartina marsh. Ammonium chloride (25 μg/ml) did not inhibit nitrogen fixation in the tall Spartina marsh, but there was a 50% inhibition in nitrogen fixation in the short Spartina marsh. On the other hand, sodium nitrate inhibited nitrogen fixation almost 100% at 25 μg/ml in both soil environments. Amino nitrogen (25 to 100 μg/ml) had little or no effect on nitrogen fixation. The results indicate that the N₂ fixers in the tall Spartina marsh were physiologically more responsive to nutrient addition than those in the short Spartina marsh. This difference in the two populations may be related to the difference in daily tidal influence in the respective areas and thus provide another explanation for the enhanced S. alterniflora production in the creek bank soil system.     

Seasonal Variability of Diazotroph Assemblages Associated with the Rhizosphere of the Salt Marsh Cordgrass, Spartina alterniflora

Nitrogen fixation is the primary N source in the highly productive but N-limited North Inlet, SC, USA salt marsh system. The diverse assemblages of nitrogen-fixing (diazotrophic) bacteria associated with the rhizospheres of the short and tall growth forms of Spartina alterniflora were analyzed at two sites, Crab Haul Creek and Goat Island, which are in different tidal creek drainage systems in this marsh. The sites differed in proximity to the main channel for tidal intrusion and in several edaphic parameters. We hypothesized that either the differing abiotic environmental regimes of the two sites or the variation due to seasonal effects result in differences in the diazotroph assemblage. Rhizosphere samples were collected seasonally during 1999 and 2000. DNA was purified and nifH amplified for denaturing gradient gel electrophoresis (DGGE) analysis of diazotroph assemblage composition. Principal components analysis was used to analyze the binary DGGE band position data. Season strongly influenced assemblage composition and biplots were used to identify bands that significantly affected the seasonal and site-specific clustering. The types of organisms that were most responsive to seasonal or site variability were identified on the basis of DGGE band sequences. Seasonally responsive members of the anaerobic diazotrophs were detected during the winter and postsenescence conditions and may have been responsible for elevated pore water sulfide concentrations. Sequences from a diverse assemblage of Gammaproteobacteria were predominant during growth periods of S. alterniflora. Abiotic environmental parameters strongly influenced both the S. alterniflora and the diazotrophic bacterial assemblages associated with this keystone salt marsh plant species.     

Hydrologic and edaphic constraints on Schoenoplectus acutus,Schoenoplectus californicus,and Typha latifolia in tidal marsh restoration

The demand for an improved knowledge base for planning and management of tidal marsh restoration worldwide has become more fully recognized. In the Sacramento‐San Joaquin Bay Delta, California, U.S.A., concerns have arisen about the degradation of the Delta and key ecosystem services. One restoration method proposed includes intentionally breaching levees that protect agricultural lands to re‐establish a hydrology that encourages tidal marsh development. Our research investigated relevant constraints on vegetation establishment and expansion of key tidal marsh species. We transplanted three macrophyte species (Schoenoplectus acutus, Schoenoplectus californicus, and Typha latifolia) using two transplant types (rhizomes and adults) in locations that varied in hydrologic and edaphic conditions at Liberty Island, a post‐levee breach tidal marsh restoration site. Two years of monitoring revealed that transplanted adults outperformed rhizomes. In addition, S. californicus exhibited greater survival and vegetation expansion. S. californicus vegetation expansion covered a maximum area of approximately 23 m², which is two orders of magnitude (OOM) greater than the maximum area covered by S. acutus (approximately 0.108 m²) and three OOM greater than T. latifolia (approximately 0.035 m²). Results suggest that hydrologic regime and degree of soil compaction are influential in controlling vegetation establishment and expansion. Greater vegetation expansion occurred in transplant sites characterized by a deeper surface layer of non‐compacted soil in conjunction with shorter durations of flooding. Information derived from this study is valuable to restoration planning in the Delta and other tidal marshes worldwide where these species occur, especially in terms of setting restoration goals and trajectories based on site‐specific environmental characteristics.     

Macro‐Tidal Salt Marsh Ecosystem Response to Culvert Expansion

The purpose of this paper was to examine the vegetative, sedimentary, nekton and hydrologic conditions pre‐restoration and the initial 2 years post‐restoration at a partially restricted macro‐tidal salt marsh site. Replacement of the culvert increased tidal flow by 88%. This was instrumental in altering the geomorphology of the site, facilitating the creation of new salt marsh pannes, expansion of existing pannes in the mid and high marsh zones, and expansion of the tidal creek network by incorporating relict agricultural ditches. In addition, the increase in area flooded resulted in a significant increase in nekton use, fulfilling the mandate of a federal habitat compensation program to increase and improve the overall availability and accessibility of fish habitat. The restoration of a more natural hydrological regime also resulted in the die‐off of freshwater and terrestrial vegetation along the upland edge of the marsh. Two years post‐restoration, Salicornia europea (glasswort) and Atriplex glabriuscula (marsh orache), were observed growing in these die‐back areas. Similar changes in the vegetation community structure were not observed at the reference site; however, the latter did contain higher species richness. This study represents the first comprehensive, quantitative analysis of ecological response to culvert replacement in a hypertidal ecosystem. These data will contribute to the development of long‐term data sets of pre‐ and post‐restoration, and reference marsh conditions to determine if a marsh is proceeding as expected, and to help with models that are aimed at predicting the response of marshes to tidal restoration at the upper end of the tidal spectrum.     

Evaluation of Long‐Term Response of Intertidal Creek Nekton to Phragmites australis (Common Reed) Removal in Oligohaline Delaware Bay Salt Marshes

In the oligohaline Alloway Creek watershed of the upper Delaware Bay, invasive Phragmites australis (Common reed; hereafter Phragmites) has been removed in an attempt to restore tidal marshes to pre‐invasion form and function. In order to determine the effects of Phragmites on nekton use of intertidal creeks and to evaluate the success of this restoration, intertidal creek nekton assemblages were sampled with weirs from May to November for 7 years (1999‐2005) in three marsh types: natural Spartina alterniflora (Smooth cordgrass; hereafter Spartina), sites treated for Phragmites removal (hereafter referred to as Treated), and invasive Phragmites marshes. Replicate intertidal creek collections in all three marsh types consisted primarily of resident nekton and were dominated by a relatively low number of ubiquitous intertidal species. The Treated marsh nekton assemblage was distinguished by greater abundances of most nekton, especially Fundulus heteroclitus (Mummichog). Phragmites had little impact on nekton use of intertidal creeks over this period as evidenced by similar nekton assemblages in the Spartina and Phragmites marshes for most years. Long‐term assemblage‐level analyses and nekton abundances indicated that the Treated marsh provided enhanced conditions for intertidal creek nekton. The response of intertidal creek nekton suggests that the stage of the restoration may influence the results of comparisons between the marsh types and should be considered when evaluating marsh restorations.     

Drainage and Elevation as Factors in the Restoration of Salt Marsh in Britain

Intertidal restoration through realignment of flood defenses has become an important component of the U.K. coastal and estuarine management strategy. Although experimentation with recent deliberate breaches is in progress, the long‐term prognosis for salt marsh restoration can be investigated at a number of sites around Essex, southeast England where salt marshes have been reactivated (unmanaged restoration) by storm events over past centuries. These historically reactivated marshes possess higher creek densities than their natural marsh counterparts. Both geomorphology and sedimentology determine the hydrology of natural and restored salt marshes. Elevation relative to the tidal frame is known to be the primary determinant of vegetation colonization and succession. Yet vegetation surveys and geotechnical analysis at a natural marsh, where areas with good drainage exist in close proximity to areas of locally hindered drainage at the same elevation, revealed a significant inverse relationship between water saturation in the root zone and the abundance of Atriplex portulacoides, normally the physiognomic dominant on upper salt marsh in the region. Elsewhere in Essex natural and restored marshes are typified by very high sediment water contents, and this is reflected in low abundance of A. portulacoides. After a century of reestablishment no significant difference could be discerned between the vegetation composition of the storm‐reactivated marshes and their natural marsh counterparts. We conclude that vegetation composition may be restored within a century of dike breaching, but this vegetation does not provide a reliable indicator of ecological functions related to creek structure.     

Macrophyte disturbance alters aquatic surface microlayer structure,metabolism, and fate

Macrophytes drive the functioning of many salt marsh ecosystem components. We questioned how temporary clearing of the macrophyte community, during restoration, would impact processes at the scale of the aquatic surface microlayer. Development, deposition, and breakup of the tidal creek surface microlayer were followed over tidal cycles seasonally in a cleared “former” Phragmites marsh and an adjacent restored Spartina marsh. Metabolic and physical processes of the mobile surface microlayers and underlying water were compared, along with distribution of organic and inorganic components onto simulated plant stems. In July and October, chlorophyll-a quantities were less on simulated stems in the cleared site than in the restored site. The aquatic microlayer in the cleared site creek exhibited lower photosynthesis and respiration rates, fewer diatoms and green algae, and less chlorophyll-a. There was a lower concentration (250 times) and reduced diversity of fatty acids in the surface microlayer of the cleared site, reflecting a smaller and less diverse microbial community and reduced food resources. Fiddler crab activity was an order of magnitude higher where macrophytes had been cleared. Their consumption of edaphic algae on the mud surface may account for the reduced algae and other organics in the creek surface microlayer, thus representing a redirection of this food resource from creek consumers. Overall, there were less total particulates in the creek surface microlayer at the cleared site, and they dropped out of the surface microlayer sooner in the tidal cycle, resulting in a lower sediment load available for deposit onto marsh surfaces.     

Tidal‐flow restoration provides little nesting habitat for a globally vulnerable saltmarsh bird

Tidal marshes are among the most threatened habitats on Earth because of their limited natural extent, a long history of human drainage and modification, and anticipated future sea‐level rise. Tidal marshes also provide services to humans and support species of high conservation interest. Consequently, millions of dollars have been spent on tidal marsh restoration throughout North America. Southern New England has a long history of tidal marsh restorations, often focused on removal of the invasive plant Phragmites australis. Working in 18 Connecticut marshes, we examined the bird community in 21 plots in restoration sites and 19 plots in reference sites. Restoration plots were divided into those in marshes where management involved restoring tidal flow and those where direct Phragmites control (e.g. cutting, herbicide) was used. Saltmarsh sparrows Ammodramus caudacutus, which are considered globally vulnerable to extinction, were less common where tidal flow had been restored than at reference sites and nested in only one of 14 tidal‐flow restoration plots. No abundance differences were found for large wading birds, willets Tringa semipalmata, or seaside sparrows Ammodramus maritimus. Vegetation at sites where tidal flow had been restored showed characteristics typical of lower‐elevation marsh, which is unsuitable for nesting saltmarsh sparrows. We conclude that, although tidal‐flow restorations in Connecticut control Phragmites and restore native saltmarsh vegetation, they produce conditions that are largely unsuitable for one of the highest conservation priority species found in eastern U.S. salt marshes.     

基于胁迫梯度假说和互惠理论的海三棱藨草种群恢复技术

滨海湿地生态修复已成为阻止海岸带生态系统退化、保护生物多样性以及提供生态服务的关键措施。以长江口原生盐沼植物海三棱藨草(Scirpus mariqueter)为研究对象,选取崇明东滩新生滩涂湿地为研究区域,通过沿潮滩高程梯度的海三棱藨草植株斑块的移植实验,探究胁迫梯度假说和互惠理论(即种内的正相互作用)对长江口海三棱藨草种群恢复的指导意义。研究结果显示:(1)在一定的胁迫梯度范围内(潮滩高程2.0 m以上),增大种植斑块可以促进海三棱藨草的种内正相互作用,显著提高种植斑块的存活率和植株密度(P0.05);(2)潮滩水文动力沉积条件与潮滩高程梯度密切相关(P0.05),水文动力沉积作用对海三棱藨草定居和生长的胁迫随高程梯度下降而增强。潮滩高程2.0 m以下处强烈的水文动力条件干扰限制了生物-物理因素的正反馈作用。滨海湿地盐沼植被修复工作的成功率可以通过改进种植方式,增强种内的正相互作用得到极大的提高。研究可为开展大规模滨海湿地盐沼植被修复工程和提高生态修复效率提供科学依据和技术支持。     

Relationship between topographic heterogeneity and vegetation patterns in a Californian salt marsh

Questions: Are species richness and species abundances higher in the presence of tidal creeks? Do species richness and species abundances vary with plot size? Location: Intertidal plain of Volcano Marsh, Bahia de San Quintin, Mexico. Methods: We analysed vegetation patterns in large areas (cells) with tidal creeks (+creek) and without (‐creek). We surveyed vegetation cover, microtopography, habitat type, and distance to creeks in nested plots of five sizes, 0.1, 0.25, 1, 2.5, and 10 m². Results: Species richness, frequency, cover, and assemblages differed between ±creek cells. Richness tended to be higher in +creek cells, and cover and frequency of individual species differed significantly between ±creek cells. We found consistent patterns in vegetation structure across plot sizes. We encountered 13 species that occurred in 188 unique assemblages. The most common assemblage had six species: Batis maritima, Frankenia salina, Salicornia bigelovii, S. virginica, Salicornia spec. and Triglochin concinna. This assemblage occurred in ±creek cells and at all spatial scales. Of the most common assemblages all but one were composed of multiple species (3–9 species/plot). Conclusions: The persistence of vegetation patterns across a 100‐fold range in spatial scale suggests that similar environmental factors operate broadly to determine species establishment and persistence. Differences in assemblage composition result from variation of frequency and cover of marsh plain species, particularly Suaeda esteroa and Monanthochloe littoralis. The recommendation for restoration of Californian salt marshes is to target (and plant) multi‐species assemblages, not monocultures.     

Quantifying Vegetation and Nekton Response to Tidal Restoration of a New England Salt Marsh

Tidal flow to salt marshes throughout the northeastern United States is often restricted by roads, dikes, impoundments, and inadequately sized culverts or bridge openings, resulting in altered ecological structure and function. In this study we evaluated the response of vegetation and nekton (fishes and decapod crustaceans) to restoration of full tidal flow to a portion of the Sachuest Point salt marsh, Middletown, Rhode Island. A before, after, control, impact study design was used, including evaluations of the tide‐restricted marsh, the same marsh after reintroduction of tidal flow (i.e., tide‐restored marsh), and an unrestricted control marsh. Before tidal restoration vegetation of the 3.7‐ha tide‐restricted marsh was dominated by Phragmites australis and was significantly different from the adjacent 6.3‐ha Spartina‐dominated unrestricted control marsh (analysis of similarities randomization test, p < 0.001). After one growing season vegetation of the tide‐restored marsh had changed from its pre‐restoration condition (analysis of similarities randomization test, p < 0.005). Although not similar to the unrestricted control marsh, Spartina patens and S. alterniflora abundance increased and abundance and height of Phragmites significantly declined, suggesting a convergence toward typical New England salt marsh vegetation. Before restoration shallow water habitat (creeks and pools) of the unrestricted control marsh supported a greater density of nekton compared with the tide‐restricted marsh (analysis of variance, p < 0.001), but after one season of restored tidal flow nekton density was equivalent. A similar trend was documented for nekton species richness. Nekton density and species richness from marsh surface samples were similar between the tide‐restored marsh and unrestricted control marsh. Fundulus heteroclitus and Palaemonetes pugio were the numerically dominant fish and decapod species in all sampled habitats. This study provides an example of a quantitative approach for assessing the response of vegetation and nekton to tidal restoration.     

Seasonal patterns of daily net photosynthesis,transpiration and net primary productivity of Juncus roemerianus and Spartina alterniflora in a Georgia salt marsh

Summary Studies of the seasonal CO₂ and water vapor exchange patterns of Juncus roemerianus and Spartina alterniflora were conducted in an undisturbed marsh community on Sapelo Island, Georgia. Daily patterns of net photosynthesis, transpiration, leaf diffusive conductance and water-use efficiency in response to ambient conditions were monitored on intact, in situ plants. Net primary productivity was calculated from the daytime CO₂ fixation totals, nighttime CO₂ loss, leaf standing stock and aboveground to belowground biomass ratios for each plant type.The tall form of S. alterniflora had higher rates of photosynthesis and higher water-use efficiency values which, in conjunction with low respiratory losses and large leaf standing crop, results in high values of net primary productivity. The environmental factors in the marsh which permit these physiological responses occur in less than 10% of the marsh. Overall, the physiological capabilities of the short form of S. alterniflora were reduced in comparison to the tall form, but the combination of environmental factors which determine the physiological responses of this form occur in a much greater portion of the marsh, and the short form of S. alterniflora dominates the Sapelo Island marshes.The response patterns of the C₃ species, J. roemerianus, differed somewhat from the height forms of S. alterniflora. A large, seasonally constant leaf standing crop coupled with moderate rates of photosynthesis resulted in a net primary productivity value which was between the tall and short height forms of S. alterniflora. However, as with the tall S. alterniflora, the environmental conditions under which this high productivity and high water loss rate can be sustained are restricted to specific regions of the environmental gradient in the marsh.Contribution No. 435 from the University of Georgia Marine Institute     

Biogeochemical Implications of Episodic Impoundment in a Restored Tidal Marsh of San Francisco Bay,California

Impounded tidal conditions often compromise coastal marsh restoration goals, through vegetation loss and other biogeochemical feedbacks. To determine if episodic marsh impoundments could be partially responsible for the observed cordgrass (Spartina foliosa) dieback at Crissy Field, Golden Gate National Recreation Area, we examined sulfur chemistry and plant stress along transects between and during tidal inlet closure events from 2007 to 2008. During closures, porewater sulfide (PW S^2?) concentrations did not respond consistently among sites, nor did they increase to levels likely to cause stress damage to cordgrass (>1 mM). However, sediment solid‐phase total reduced sulfur (TRS) concentrations did respond strongly to closures both at surface and subsurface depth intervals, and they were greatest in sites with high organic matter content (>5%). The temporal patterns of both PW S^2? and TRS suggest that while sulfate reduction may be enhanced during closure events, the free sulfide produced is largely precipitated into solid‐phase minerals. Even without millimolar levels of PW S^2?, plant stress was observed during closures, as indicated by a buildup of ethanol in root tissues, a by‐product of fermentative respiration brought on by limited oxygen availability. Further, enhanced sulfate reduction may be related to the higher relative concentrations of methylmercury in low intertidal surface sediments observed during closure events. These data suggest that, in support of vegetated tidal marsh restoration goals, tidal flows should be maintained actively to reduce the impact of impoundment events on marsh biogeochemistry and productivity.     

Influence of Mycorrhizal Inoculation, Inundation Period, Salinity, and Phosphorus Availability on the Growth of Two Salt Marsh Grasses, Spartina alterniflora Lois. and Spartina cynosuroides (L.) Roth., in Nursery Systems

Restoration of salt marsh ecosystems is an important concern in the eastern United States to mitigate damage caused by industrial development. Little attention has been directed to the mycorrhizal influence on plantings of salt marsh species to stabilize estuarine sediments and establish cover. In our study, seedlings of two salt marsh grasses, Spartina alterniflora and Spartina cynosuroides, were grown in soil with a commercial, mixed species inoculum of arbuscular mycorrhizal fungi. Plants were grown in experimental “ebb and flow” boxes, simulating three levels of tidal inundation, to which two levels of applied phosphorus (P) and two levels of salinity were imposed. After 2.5 months, S. alterniflora was poorly colonized by arbuscular mycorrhizae, developing only fungal hyphae and no arbuscules, but S. cynosuroides became moderately colonized. Mycorrhizal inoculation marginally improved growth and P and nitrogen (N) content of both plant species at low levels of P supply but significantly increased tillering in both plant species. This factor could be beneficial in enhancing ground cover during restoration procedures. Greater P availability increased the mycorrhizal status of S. cynosuroides and improved P nutrition of both plant species, despite a reduction in the root‐to‐shoot ratio. Increasing salinity reduced mycorrhizal colonization of S. alterniflora but not of S. cynosuroides. Growth and nutrient content of S. alterniflora was improved at higher levels of salinity, but only increased nutrient content in S. cynosuroides. Increased duration of tidal inundation decreased plant growth in both species, but tissue P and N concentrations were highest with the longest time of inundation in both species.     

Fish community composition and diversity at restored estuarine habitats in Tampa Bay,Florida, United States

Estuary restoration in Tampa Bay, Florida, United States, is an ongoing focus of natural resource managers because of pressure from an increasing coastal population, historic habitat loss, and restoration's importance to economic development, recreational activities, and fish habitat. A growing population can also limit future large‐scale restorations due to associations with cost and land availability. This limitation might be overcome by applying the habitat mosaic approach to restoration, which creates distinct habitat types at small spatial scales. This approach was applied to create three types of estuarine habitat, reconnected tidal creek, salt marsh, and tidal pond. The objectives of this study were to (1) initiate monitoring of a restored wetland mosaic and (2) determine how fish diversity and community structure vary among restored habitat types. Replicated sampling using a 3‐mm mesh seine was used to characterize the fish communities. Our results indicate that the habitat mosaic approach creates suitable habitat for a variety of fish species where 37% of fish species were captured in just one habitat type. In particular, the recreationally important Centropomus undecimalis (common snook) was more common in the mangrove‐lined creek and the non‐native Sarotherodon melanotheron (blackchin tilapia) was common in the tidal pond. Greater emphasis should be placed on applied restoration research to identify how habitat types within a larger restoration mosaic contribute to local species diversity and recreationally and commercially important fishes, while limiting non‐natives. This emphasis could reveal how restoration approaches can be modified to include habitat mosaics, maximizing their contribution to productive fish habitat.     

Accelerating the Restoration of Vegetation in a Southern California Salt Marsh

Re-establishing plant cover is essential for restoring ecosystem functions, but revegetation can be difficult in severe sites, such as salt marshes that experience hypersalinity and sedimentation. We tested three treatments (adding tidal creeks, planting seedlings in tight clusters, and rototilling kelp compost into the soil) in a site that was excavated to reinstate tidal flows and restore salt marsh. The magnitude of responses was the reverse of expectations, with tidal creeks having the least effect and kelp compost the most. On the marsh plain, kelp compost significantly increased soil organic matter (by 17% at 0–5 cm; p = 0.026 and 11.5% at 5–20 cm; p = 0.083), total Kjeldahl nitrogen (45% at 5–8 cm; p < 0.001) and inorganic nitrogen (35% at 5–8 cm; p < 0.006), and decreased bulk density (16% at 0–5 cm; p < 0.001 and 21% at 5–8 cm depth; p < 0.001) compared to control plots. Survivorship of kelp compost treated plantings increased, along with growth (> 50% increase in a growth index at 20 months after planting; p < 0.0001). In Spartina foliosa plots, kelp compost did not affect soil organic matter, but plants were taller (by ~11 cm; p = 0.003) and denser (47% more stems; p = 0.003). Planting seedlings 10-cm apart in tight clusters on the marsh plain increased survivorship by 18% (compared to 90-cm apart in loose clusters; p = 0.053), but not growth. Tidal creek networks increased survivorship of Batis maritima and Jaumea carnosa by ≥20% (p = 0.060 and 0.077, respectively). Kelp compost had a strong, positive influence on vegetation establishment by ameliorating some of the abiotic stress.     

Tidal Marsh Restoration: Trends in Vegetation Change Using a Geographical Information System (GIS)

Adequately evaluating the success of coastal tidal marsh restoration has lagged behind the actual practice of restoring tidally restricted salt marshes. A Spartina-dominated valley marsh at Barn Island Wildlife Management Area, Stonington, Connecticut, was tidally restricted in 1946 and consequently converted mostly to Typha angustifolia. With the re-introduction of tidal flooding in 1978, much of the marsh has reverted to Spartina alterniflora. Using a geographical information system (GIS), this study measures restoration success by the extent of geographical similarity between the vegetation of the restored marsh and the pre-impounded marsh. Based on geographical comparisons among different hydrologic states, pre-impounded (1946), impounded (1976), and restored (1988) tidal marsh restoration is a convergent process. Although salt marsh species currently dominate the restored system, the magnitude of actual agreement between the pre-impounded vegetation and that of the restored marsh is only moderate. Further restoration of the salt marsh vegetation may be limited by continued tidal restriction, marsh surface subsidence, and reduced accretion rates. General trends of recovery are identified using a gradient approach and the geographic pattern’ of vegetation change. In the strictest sense, if restoration refers only to vegetation types that geographically replicate preexisting types, then only 28% of the marsh has been restored. Restoration in a broader sense, however, representing the original salt marsh vegetation regardless of spatial position, amounts to 63% restored. Unrestored marsh, dominated by Typha angustifolia and Phragmites australis, remains at 37%. By emphasizing trends during vegetation recovery, this evaluation technique aims to understand the restoration process, direct future research goals, and ultimately aid in future restoration projects.