No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Mechanisms of Marsh Habitat Alteration Due to Phragmites: Response of Young-of-the-Year Mummichog (Fundulus heteroclitus) to Treatment for Phragmites Removal
Abstract
In recent decades, marshes naturally dominated bySpartina spp. have been replaced byPhragmites australis throughout the northeastern United States. We suggest that early in this invasion there was little effect on the fish fauna.
As the invasion proceeds, the marsh surface habitat became more altered (i.e., elevated, flattened, reduced water-filled depressions,
and reduced standing water), which resulted in a reduction of feeding, reproduction, and nursery function for fishes, especiallyFundulus spp. These potential changes in marsh habitat and function have resulted in numerous attempts to removePhragmites and restoreSpartina spp. To evaluate the response of marsh surface fishes toPhragmites treatment, we examined fish use in the brackish water reaches of Alloway Creek in the Delaware Bay estuary. ReferencePhragmites habitats were compared with referenceSpartina alterniflora-dominated habitats and sites treated (1996–1998) to removePhragmites to restore former vegetation (i.e., restored, now comprised of 100%Spartina). Fish were sampled with an array (n=9 at each site) of shallow pit traps (rectangular glass dishes, 27.5×17.5×3.7 cm). Small
individuals (mean=17.5, 5–45 mm TL) dominated all pit trap collections. Fish abundance was highest at the restored (catch
per unit effort [CPUE]=2.16) andSpartina (CPUE=0.81) sites with significantly lower values atPhragmites (CPUE=0.05) habitats. Samples were dominated by young-of-the-year mummichog,Fundulus heteroclitus (98% of total fish, n=631). The only other fish species collected was spotfin killifish,Fundulus luciae (2% of total catch, n=14), which was only present in restored andSpartina habitats. These observations suggest that the restored marsh is providing habitat (water-filled depressions on the marsh
surface) for young-of-the-yearFundulus spp. These marshes are responding favorably to the restoration based on the much greater abundance of fish in restored versusPhragmites habitats and the overall similarity between restored andSpartina habitats.
... Both invasive macrophyte species (Phragmites and Spartina in the marsh and mangrove systems, respectively) that were removed in restoration efforts are ecosystem engineers that drastically alter biotic and abiotic factors in the habitats in which they invade ( Li et al., 2009;Rooth and Cornwell, 2003). When invading salt marshes, Phragmites traps sediment at an increased rate, raising the elevation of the marsh platform and changing marsh platform dynamics ( Able et al., 2003;Rooth and Cornwell, 2003). Even after restoration, marsh platform dynamics do not immediately return to reference conditions ( Able et al., 2003). ...
... When invading salt marshes, Phragmites traps sediment at an increased rate, raising the elevation of the marsh platform and changing marsh platform dynamics ( Able et al., 2003;Rooth and Cornwell, 2003). Even after restoration, marsh platform dynamics do not immediately return to reference conditions ( Able et al., 2003). Access to the marsh platform during spring high tides is an important driver of trophic dynamics and energy flow in marsh food webs, and higher marsh platform elevation would limit connectivity between marsh creek and platform habitats ( Nelson et al., 2015). ...
... Access to the marsh platform during spring high tides is an important driver of trophic dynamics and energy flow in marsh food webs, and higher marsh platform elevation would limit connectivity between marsh creek and platform habitats ( Nelson et al., 2015). Removing invasive macrophytes and allowing for the re-establishment with the natural dominant macrophyte may not restore all the physical characteristics of the reference habitat and may alter ecosystem connectivity, thus shifting the baseline resource pool that supports the restored food web to a state not found in reference habitats ( Able et al., 2003;Dibble and Meyerson, 2014;Litvin et al., 2018). Layman et al. (2007) describes the consequences of the loss of habitat connectivity in mangrove ecosystems, as fragmentation between mangroves and tidal creeks led to decreases in the variability of resource use, altering ecosystem function. ...
The primary goal of habitat restoration is to recover the ecological structure, function, and services of natural ecosystems lost due to disturbance. Post-restoration success typically focuses on the return of a desired habitat type, consumer species composition, or abundance relative to a reference site. However, how energy flow responds to habitat restoration has not been widely studied, and there is a need to develop a better understanding of how energy flows through a restored vs reference ecosystem following restoration. We tested recently developed niche metrics as a tool to assess the degree of recovery of ecosystem energy flow and evaluate the success of habitat restoration. Using published stable isotope values from six systems, one to three years post-restoration, we used Bayesian mixing models to quantify resource use by consumers to generate food web hypervolumes for restored and reference habitats in each ecosystem and to quantify similarity in resource use between restored and reference systems. Our analysis showed that there were differences in restoration success at each restoration project between the restored and reference food webs, but two general patterns emerged in the early stages following restoration. Restoration efforts that restore biogenic habitats display lower levels of recovery of food web function than those that only restore abiotic habitat structural. Restoration increases the variability in basal resource use of consumers in food webs that rely heavily on one basal resource, while in food webs that relied on multiple basal resources consumers decrease variability in basal resource use. Our results demonstrate that hypervolume analysis is a powerful tool that can be used to quantify energy flow, the recovery of food web function, and measure restoration success.
... This category included 10 studies, all from marine coastal ecosystems [18,62,63,73,76,81,[95][96][97][98]. The majority of these studies were located in the Northern hemisphere (nine), and in the USA (four [81,95,97,98]), followed by Canada (two, [73,76]), Mexico (one, [62]), France (one, [63]) and Sweden (one, [18]). ...
... This category included 10 studies, all from marine coastal ecosystems [18,62,63,73,76,81,[95][96][97][98]. The majority of these studies were located in the Northern hemisphere (nine), and in the USA (four [81,95,97,98]), followed by Canada (two, [73,76]), Mexico (one, [62]), France (one, [63]) and Sweden (one, [18]). In the Southern hemisphere there was only one study from Australia [96]. ...
... In the Southern hemisphere there was only one study from Australia [96]. Studies varied in the validity: six were judged to have high validity [62,63,73,81,95,96] and four were assigned medium validity ( [18,76,97,98]). Medium validity was assigned due to unbalanced sampling design [76], pseudoreplication [97], differences between samples [98] and lack of spatial control [18]. There were no studies with unclear validity. ...
Background
Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas.
Methods
We searched for peer-reviewed and grey literature on such impacts in English, Dutch, Danish, Finnish, German, Swedish and Spanish. Searches were performed in bibliographic databases, specialist websites, bibliographies of review articles. We also contacted stakeholder to find relevant literature. Eligible studies included small- and large-scale field studies in marine systems and large lakes (> 10,000 km ² ) in temperate regions of the Northern and Southern Hemispheres. Included replicated comparisons of fish recruitment between altered and unaltered control areas, comparisons before and after an alteration, or both. Relevant outcomes (response variables) included measures of recruitment defined as abundance of juvenile fish in coastal habitats. All fish species were considered. Articles were screened for eligibility by title, abstract and full text. Eligible studies were critically appraised based on their external and internal validity. From each eligible study of sufficient validity, we extracted information on study design, measured outcomes, exposure, type of comparator, effect modifiers and study findings. Study findings were synthesised narratively.
Results
We searched for eligible studies in 15 databases, 24 specialist websites, Google Scholar, and bibliographies of 11 review articles. The review finally included 37 studies that were eligible and of sufficient validity to be considered for final synthesis. Most studies (23 of 37) were from the Northern Hemisphere. Studies varied in design, spatial resolution, target fish species, and type of structural habitat change. This high level of variation did not allow for a quantitative synthesis and prevented us from drawing general conclusions on the impact of structures or structural modifications on fish recruitment. In this review we provide a narrative synthesis of the evidence base and classify eligible studies into six categories (based on type of exposure and comparator). The categories are as follows: the impacts on fish recruitment of: (1) artificial structures in coastal areas, (2) structures designed as fish attractors, (3) large scale urban sprawl, (4) ‘novel’ habitats, (5) habitat loss, and (6) restoration.
Conclusions
This review revealed a very limited evidence base for how structural modifications and marine urban sprawl can affect fish recruitment. Thus, there is a substantial mismatch between stakeholder needs and research evidence. Further, the impact and ecological performance of artificial structures depend both on context and species. Clearly, there is a need for more research on the subject, especially on long-term consequences at larger spatial scales.
... Although we did not measure the slope of the creek bank at our trawl sites throughout the estuary, we did observe steep, almost vertical, creek edges in mangrove areas (Electronic Supplemental Material; Fig. S1), which were also observed in mangrove habitats in Louisiana (Caudill 2005). Conversely, salt marsh habitats in the GTM estuary had much more gradual slopes, characteristic of typical Spartina alterniflora-dominated marshes on the US Atlantic coast (e.g., Able et al. 2003). Habitat characteristics such as creek bank slope or steepness and the elevation of the marsh surface platform can influence nekton access as well as habitat function (Able et al. 2003;Allen et al. 2007). ...
... Conversely, salt marsh habitats in the GTM estuary had much more gradual slopes, characteristic of typical Spartina alterniflora-dominated marshes on the US Atlantic coast (e.g., Able et al. 2003). Habitat characteristics such as creek bank slope or steepness and the elevation of the marsh surface platform can influence nekton access as well as habitat function (Able et al. 2003;Allen et al. 2007). This can, in turn, have effects on nekton abundance and distribution in these habitats. ...
The marsh-mangrove ecotone along the southeastern US Atlantic coast occurs in northeast Florida within the Guana-Tolomato-Matanzas (GTM) estuary, where emergent vegetation transitions from marsh-dominated in the north to mangrove-dominated in the south. Dominant vegetation type has been shown to influence creek bank slope, nekton access to refuge, predation risk, and access to food. The northward distribution of mangroves in the estuarine mosaic is in flux in northeast Florida, and the effect on subtidal nekton, including commercially important species, is not known. To determine if estuarine nekton assemblages differ along the marsh-mangrove ecotone, a 60-km transition zone within GTM estuary was divided into 20 sub-zones where nearshore subtidal nekton communities were sampled monthly with trawls for 1 year. A total of 15,750 individuals consisting of 100 species were collected during the study period; 13 species made up 90% of the total catch. Subtidal nekton assemblages in marsh sites were dominated by typical salt marsh species (i.e., Leiostomus xanthurus, Anchoa spp., Bairdiella chrysoura) and had little overlap with assemblages in mixed and mangrove sites, which were dominated by structure-oriented species (i.e., Lagodon rhomboides and Eucinostomus spp.). Despite similar environmental conditions among the zones, there were clear differences in the subtidal nekton community along the marsh-mangrove ecotone, largely driven by fish species. This change in nekton community along the ecotone suggests that ecological processes such as food availability or predator/prey dynamics affected by changes in marsh surface habitats may result in differences in nekton species distribution and abundance across interconnected habitats such as in subtidal nekton that we observed in the GTM estuary.
... Dead end creeks dominated by Spartina alterniflora in the lower, higher salinity estuary and Spartina cynosuroides in the upper estuary are the most common. In the upper estuary, at lower salinities, the marshes are dominated by invading Phragmites [26,29,30] and have a more diverse freshwater flora. Thoroughfares connecting bays and other waterways are most common in the lower estuary, such as in Sheepshead Meadows, and the channels through the flood tidal delta in the vicinity of Little Egg Inlet in Great Bay (Seven Islands) and Little Egg Harbor (Story Islands area). ...
... The overall reduced number of peat reefs further up the estuary may be due to changes in vegetation along the salinity gradient. This appears most evident along the edges of low salinity creeks where the invasive form of Phragmites australis is common (personal observation), especially in late stages of the invasion [29]. It may be that the extensive and deep rhizome mat of this species prevents peat reef formation. ...
... The invasive clonal grass Phragmites australis (hereafter P. australis) is aggressively colonizing freshwater coastal marshes and displacing resident plant species with dense, monotypic stands (Trebitz and Taylor, 2007;Whyte et al., 2008;Tulbure and Johnston, 2010). Phragmites australis out-competes the plant species historically characteristic of cattail marsh and meadow marsh habitats (Wilcox et al., 2003) and fills in open-water pools (Able et al., 2003). Not only does this reduce floristic diversity (Keller, 2000), but invasion has the potential to threaten the highly-valued coastal-marsh habitat used by a unique suite of wetland birds, including species at risk like least bittern (Ixobrychus exilis). ...
... It has been argued that the density of stands and rigidity of stems can make the habitat impenetrable to large-bodied waterbirds (Benoit and Askins, 1999;Kessler et al., 2011). Further, the increased above-ground biomass couples with high litter accumulation (Rooth et al., 2003;Windham, 2001) to smooth microtopography, raise soil and reduce standing water levels (Lathrop et al., 2003;Weinstein and Balletro, 1999;Windham and Lathrop, 1999), eliminating open-water pools and creeks (Able et al., 2003). Standing water and open-water pools are essential habitat for waterbirds and shorebirds, contributing to the overall heterogeneity of marshes and correlating with an increase in bird species richness, especially in meadows (Benoit and Askins, 1999;Riffell et al., 2001). ...
On the North shore of Lake Erie, Long Point provides habitat to many thousands of breeding and migrating birds, including marsh-nesting species that are in decline across the Great Lakes. Invasive Phragmites australis threatens the ecological integrity of these marshes. Early concerns prompted a study into the effects of invasion on bird use in 2001–2002 that concluded P. australis was not a major bird conservation issue. We evaluate breeding season bird occupancy in these wetlands after over a decade of P. australis expansion, comparing bird diversity and abundance in P. australis with diversity and abundance in the vegetation communities that P. australis is displacing: cattail, meadow, and open-water marsh. We also examine community composition and functional traits to better capture the effects of P. australis invasion. In 2015, total bird abundance was lower in P. australis than cattail marsh (ANOVA p < 0.001), with little difference in bird species richness among vegetation types (ANOVA p = 0.272). Bird community composition was distinct among the vegetation types (MRPP p < 0.001), such that P. australis supported a subset of bird species found within cattail and meadow marsh habitat, rather than novel species. Phragmites australis habitat excludes many marsh-nesting species and provides habitat for shrub-nesting, ground and foliage gleaners instead. Marsh-nesters of conservation concern are restricted to remaining cattail, meadow marsh, and open-water habitat. The full effects of P. australis invasion may exhibit a lag time, and community composition and functional traits should be considered when evaluating the effects of biological invasions.
... Wetlands, which comprise 6% of the earth's land mass, host 24% of the most invasive plant species (Zedler and Kercher 2004). These wetland invaders compete with native species and modify physical and biological environments through increased sediment trapping and altered nutrient dynamics, food webs, and water cycling (Zavaleta 2000;Blank and Young 2002;Able et al. 2003;Windham and Meyerson 2003;Zedler and Kercher 2004;Burkle et al. 2012;Wigginton et al. 2014;Robison et al. 2021). ...
Invasive species exert disproportionate impacts in wetlands and pose particular challenges for rare species persisting at small spatial scales. In the urbanized San Francisco Estuary (SFE), which contains 90% of California’s remaining coastal wetlands, invasive and rare species often co-occur. One narrow endemic taxon, the federally listed Suisun thistle ( Cirsium hydrophilum var. hydrophilum ) is restricted to two or three locations where the invasive perennial pepperweed ( Lepidium latifolium ) has an increasing presence. Perennial pepperweed has invaded salt, brackish, and freshwater wetlands around the SFE, leading to high management concern. In this study, we investigated how perennial pepperweed may contribute to further rarity of the Suisun thistle, by conducting a removal experiment and surveying soil-plant relationships. Removing pepperweed led to a doubling of native species relative cover and an increase in native species richness by an average of one species per plot, positive effects on Suisun thistle cover, number, and reproductive output, and shifts in soil properties. Combined with survey data inside and outside of pepperweed stands, we conclude that pepperweed competes with Suisun thistle via competition for space, nutrients, and light, interferes with the Suisun thistle’s reproductive success, and alters brackish marsh soil physicochemical characteristics to further favor pepperweed. We recommend local control of pepperweed to prevent further loss of Suisun thistle. Further, the wide range of mechanisms by which this invasion may proceed if unchecked should be considered in other settings where rare or uncommon species are at risk from invaders.
... Phragmites inhibits the movement of large animals through wetlands, and few herbivores have been observed consuming this invasive grass (Meyerson et al. 2000). There is also evidence to suggest that bird (Raichel et al. 2003;Robichaud and Rooney 2017), turtle (Cook et al. 2018), macroinvertebrate (Warren et al. 2001;Whyte et al. 2009), and fish (Warren et al. 2001;Able et al. 2003;Raichel et al. 2003;Dibble and Meyerson 2016) populations may be altered by Phragmites invasion. Previous studies in tidal marsh wetlands in the eastern United States found that Phragmites stands supported a different arthropod assemblage than neighboring native vegetation sites Denno 2005, 2006). ...
Wetlands provide essential habitat for shorebirds, songbirds, and waterfowl. Invasive species can disrupt trophic interactions within wetlands by altering the arthropod assemblages on which birds rely. An invasive grass species, Phragmites australis (common reed), has invaded wetlands across North America, including those surrounding the Great Salt Lake, Utah, U.S.A. Phragmites outcompetes native vegetation and alters habitat for resident and migratory birds, yet how Phragmites affects arthropod assemblages is unclear. To address these knowledge gaps, this study investigated how arthropod assemblages differ between native and invasive vegetation in Great Salt Lake wetlands. We examined the arthropod assemblages found within three native habitats as well as in Phragmites-invaded areas. There were few differences in arthropod assemblages between Phragmites and two native habitats (hardstem bulrush, Schoenoplectus acutus and alkali bulrush, Bolboschoenus maritimus). Arthropod assemblages differed between Phragmites and the native Salicornia rubra (pickleweed), which differed markedly from the other plant species in structure, biomass, and related site conditions. Identifying how arthropods interact with Phragmites and native vegetation is critical to recognizing how to effectively manage wetlands for bird habitat. By gaining an understanding of these relationships, arthropod biomass, abundance, diversity, and assemblage composition could serve as assessment metrics for determining wetland management success.
... The introduction of a non-native lineage of the wetland grass Phragmites australis to North America has led to a dramatic increase in its relative abundance at the expense of native plants (Saltonstall, 2002;Silliman and Bertness, 2004;Escutia-Lara et al., 2012;Yuckin and Rooney, 2019). Once established, invasive Phragmites forms large mono-specific stands that can reduce animal and plant diversity (Able et al., 2003;Minchinton and Bertness, 2003), and alter biogeochemical cycles (Bernal et al., 2017;Mozdzer and Megonigal, 2013). ...
Land use changes and greater nitrogen input into waterways have facilitated the spread of an invasive Eurasian lineage of Phragmites australis across North America. Its establishment has led to decreases in wetland plant diversity, and displacement of a native American Phragmites lineage considered to be a low-nutrient specialist. We hypothesized that carbon-rich amendments that reduced nitrogen availability would competitively favor the native lineage and nitrogen additions would favor the invasive lineage. In the greenhouse we assessed competitive interactions between native and invasive lineages following sawdust (low nitrogen) and urea (high nitrogen) additions by measuring total biomass, chlorophyll fluorescence and evaluating biomass allocation. Sawdust additions did not limit invasive Phragmites growth, while urea increased aboveground biomass of both lineages. Unexpectedly, mixtures of native and invasive Phragmites produced more above and belowground biomass than monocultures. Our findings suggest that at the level examined in this study, carbon additions would not be an effective management tool to control invasive Phragmites or restore the native North American lineage, but that facilitation between native and invasive lineages could promote their coexistence across a range of nutrient availability. Our results also provide limited evidence that displacement of native Phragmites could be due to other factors such as disturbance rather than competitive exclusion.
... A decline in Spartina and increase in Phragmites resulted in shifts from free-living to concealed herbivores, reductions in the dominant spiders, reductions in arthropod predators, and increases in detritivores (Gratton and Denno, 2005). Fish abundance (young-of-the-year Fundulus spp.; mummichog) is also reduced following Phragmites invasion and reversed with Phragmites management in Atlantic coastal marshes (Able et al., 2003). More generally, sub-adult nekton (swimming crustaceans, aquatic fish) were found to be negatively impacted by Phragmites based on a meta-analysis of the literature (Dibble et al., 2013). ...
Globally, the management of invasive plants is motivated by a desire to improve ecosystem services (e.g., recreation, flood mitigation, soil fertility for agriculture, aesthetics) and critical habitat for imperiled species. To reduce invader populations and impacts, it is important to document the social and ecological basis (i.e., the social-ecological system) for the management that has been employed and areas where a greater level of coordination among stakeholder groups (managers, scientists, legislators, resource users) could improve efforts. We present a conceptual model that builds on current thinking for how best to connect these four stakeholder groups—to foster stronger citizen lobbying for impacted resources, science-based governance, legislator-driven noxious weed laws and funding for management and science, knowledge co-production by scientists and managers, and co-management by managers and resource users. In light of our model, we present two case studies based in Nebraska and Utah, U.S.A. involving a common North American wetland invader, Phragmites australis (non-native common reed). In Nebraska, potential lawsuits stemming from water conveyance was strong motivation for funding management. In Utah, duck hunters and other resource users initially instigated management. Progress toward the successful management of Phragmites has been the result of manager-scientist partnerships addressing a knowing-doing gap among practitioners, the complexities of management mosaics, as well as overcoming economic and logistical constraints. Our model demonstrates how legislative initiatives can fund new research and bolster on-going management, while organically building strong partnerships among scientists, managers, and resource users that are key for successfully managing invasive species.
... En el caso de los ecosistemas acuáticos las alteraciones producidas por las especies invasoras pueden cambiar radicalmente las características del sitio al grado de destruirlo completamente (figura 12.1). Este es el caso del carrizo (Phragmites australis), que cuando es invasor altera la microtopografía de los humedales que invade, pues su patrón de crecimiento y talla hace que crezca hacia las zonas profundas de los canales reteniendo sedimentos en el proceso, causando el relleno de los humedales, eliminando las zonas con columnas de agua importantes para otras especies y alterando la dinámica hidrológica (Able et al., 2003). ...
... We recommend including structural heterogeneity treatments such as pools, channels, and other connectivity methods in invasive plant control efforts. Such approaches have been demonstrated to result in increased fish use and habitat quality across diverse wetland ecosystem types (Able et al., 2003;Larkin et al., 2006Larkin et al., , 2008 including Typha invaded St. Lawrence River wetlands (northern pike;Farrell and Brown, 2012;Neveldine et al., 2019). More study of fish assemblages within dense Typha stands across GLCWs is needed across seasons to expand on our summer data; most studies of Great Lakes fish communities describe sampling near or partially within Typha stands because of sampling difficulties in these dense habitats (Henning et al., 2014), but as Typha continues to dominate plant communities, a determination of the suitability of fish habitat, and consequently the potential area of fish habitat loss, as a result of increasing Typha stands across GLCWs is critical. ...
Great Lakes coastal wetlands (GLCWs) provide critical fish habitat. The invasion of GLCWs by hybrid and narrow-leaved cattail, Typha × glauca and Typha angustifolia (hereafter Typha), homogenizes wetlands by out-competing native plant species and producing copious litter. However, the effect of this invasion on fish communities is little known. To measure the effect of Typha on fishes, we established plots in Typha invaded and native wetland emergent zones in a northern Lake Michigan coastal wetland, and measured environmental variables, plants, and fishes in each zone over two summers. Dissolved oxygen and water temperature were significantly lower in invaded compared to native plots. Invaded plots were dominated by Typha and its litter; whereas. sedges (Carex spp.) were the most abundant species in native plots. Fish abundance and species richness were significantly lower in Typha compared to native wetland plots. The Typha fish community was dominated by hypoxia tolerant mudminnow whereas other small, schooling, fusiform species such as cyprinids and fundulids were absent. These results illustrate the negative impact of a dominant invasive plant on Great Lakes fishes that is expected to be found in Typha invasions in other GLCWs.
... P. australis was targeted for removal, because it is considered a Bbiopollutant^in the U.S, that negatively influences the habitat value of tidal salt marshes for young nekton by elevating the marsh planform and filling in the microtopography of the marsh surface (Windham 1995;Weinstein and Balletto 1999;Able et al. 2003;Rooth et al. 2003). The former alters the hydroperiod, the latter influences access to the marsh plain by resident and young-of-year transient organisms (Boesch and Turner 1984;Rozas et al. 1988;Kneib 1997;Able and Hagen 2000). ...
Abstract
Restoration of 4049 ha of tidal wetlands was required to offset nekton losses at a power facility located on Delaware Bay, USA.
Vegetation coverage, the permitted criterion for success, was compared by meta-analysis to restoration trajectories for abundance
and growth of dominant nekton during the same 17-year period at two reference and five restoration sites. Mean catch per unit
effort (CPUE), at both upper Bay (former Phragmites australis dominated sites) and lower Bay (former salt hay farms), were
generally indistinguishable from those of the reference sites, and Hedge’s d for all sites suggested that numbers of individuals at
restored locations did not differ significantly from those at the reference sites. Mean length distributions of dominant nekton in the
upper Bay, however, were negative for all restoration sites combined by the end of the study. Although growth of nekton at the
lower Bay restoration sites was indistinguishable from reference sites, the grand mean length for nekton measured at all sites in
the Bay was negative suggesting that nekton growth at the formerly Phragmites-dominated sites failed to meet the restoration
goals by the end of the study period. Thus, vegetation success criteria may not necessarily reflect recovery of animal related
success criteria.
... On a natural marsh, Morzaria-Luna et al. (2004) found that plant species richness was slightly higher in areas close to creeks, and these areas also had higher topographic heterogeneity. Topographic variation is also associated with increased use of natural marshes by fish (Able et al. 2003). However, an experimental assessment at Friendship Marsh in the Tijuana Estuary showed that whilst creek excavation did generate topographic heterogeneity by 'jump starting' the development of the drainage network (Wallace et al. 2005), the effect of this on plant survival was only modest (O'Brien and Zedler 2006) and although one fish species showed higher abundance where creeks were excavated, a second species occurred at lower abundance (Larkin et al. 2008). ...
Halophyte distributions on saltmarshes are strongly related to elevation in the tidal frame. However, collinearity between elevation, the consequent inundation regime, and sediment waterlogging/redox potential obscures the proximate causes of distribution patterns. We sought to distinguish the effects of elevation per se from those of waterlogging by manipulating microtopography.
We experimentally manipulated elevation by ±15 cm at locations that spanned the elevation ranges of three saltmarshes recently reactivated by managed coastal realignment. Experimental plots were initially cleared of any vegetation. Elevation and sediment redox potential were determined for each plot. We planted five perennial species (Armeria maritima, Atriplex portulacoides, Limonium vulgare, Plantago maritima and Triglochin maritima) in half of the plots, recording survival over 4 years, and monitored natural colonization of the other plots.
Overall, redox potential increased with elevation. Sediments were more oxidizing in raised plots and more reducing in lowered plots. Redox reductions in lowered plots were in line with those that would be predicted from the overall redox/elevation relationship, but increases in raised plots were greater than predicted from elevation alone.
Plant colonization and survival was poorer in lowered plots and, for most species, improved in raised plots. This poorer colonization and survival can, in part, be attributed to the concomitant alterations in redox potential and elevation in the tidal frame, but microtopographic manipulation also had substantial independent effects on plant performance, including on the survival of all planted species and the colonization of Puccinellia maritima, Salicornia europaea agg. and Tripolium pannonicum.
Synthesis. Microtopography can have effects on sediment chemistry and plant performance similar in magnitude to those of overall tidal elevation. Understanding how its effects modulate the relationship between tidal elevation, redox and other environmental conditions helps clarify the abiotic factors that fundamentally determine halophyte colonization and survival. These results support the use of topographic manipulation to enhance the diversity of created saltmarshes.
... Studies conducted within Alloway Creek, in the Delaware Bay estuary and the Connecticut River documented a decrease in water availability in areas of marshes that were dominated by Common Reed (Warren et al., 2001; Able et al., 2003). This, in turn, also affected the abundance of larval and juvenile fishes due to loss of rearing habitat (Warren et al., 2001; Able et al., 2003).The temperature of the water was also found to be lower in marshes containing Common Reed, as the reed often is found to cover the surface of the water, preventing light and heat from entering(Able et al., 2003). Summary of the ecological impacts of P. australis to native fishes in North America-Count of the number of papers reviewed that document specific changes caused by P. australis, to native fishes in North America (total of 34 papers reviewed). ...
The invasive European Common Reed (Phragmites australis), first established in North America in the early 1900’s, is now a dominant emergent aquatic plant in many coastal and inland wetlands. A review of the literature was conducted to evaluate the extent of ecological impacts on fishes and their habitat, such as changes in the composition and abundance of native fishes and wetland plants, and alterations to water availability and substrate. The review indicated that a reduction in the abundance of native fishes was common (54.54% of studies), as were impacts to fish habitat (e.g., 54.54% of studies documented a change in wetland plant composition). Many studies were conducted in the eastern and northern United States, which showed that the abundance of juvenile and larval fishes was significantly lower in marshes dominated by P. australis, relative to those dominated by native plant species (Spartina alterniflora); however, changes to wetland plant abundance and composition, water availability, water temperature, nutrient cycling, substrate, reproduction and spawning, genetics of native fishes, and general food web effects were also observed. These results indicate that P. australis poses numerous ecological impacts to the structure and function of wetland habitats, with implications for the ongoing productivity of aquatic ecosystems.
... P. australis was targeted for removal, because it is considered a Bbiopollutant^in the U.S, that negatively influences the habitat value of tidal salt marshes for young nekton by elevating the marsh planform and filling in the microtopography of the marsh surface (Windham 1995;Weinstein and Balletto 1999;Able et al. 2003;Rooth et al. 2003). The former alters the hydroperiod, the latter influences access to the marsh plain by resident and young-of-year transient organisms (Boesch and Turner 1984;Rozas et al. 1988;Kneib 1997;Able and Hagen 2000). ...
Abstract
Restoration of 4049 ha of tidal wetlands was required to offset nekton losses at a power facility located on Delaware Bay, USA.
Vegetation coverage, the permitted criterion for success, was compared by meta-analysis to restoration trajectories for abundance
and growth of dominant nekton during the same 17-year period at two reference and five restoration sites. Mean catch per unit
effort (CPUE), at both upper Bay (former Phragmites australis dominated sites) and lower Bay (former salt hay farms), were
generally indistinguishable from those of the reference sites, and Hedge’s d for all sites suggested that numbers of individuals at
restored locations did not differ significantly from those at the reference sites. Mean length distributions of dominant nekton in the
upper Bay, however, were negative for all restoration sites combined by the end of the study. Although growth of nekton at the
lower Bay restoration sites was indistinguishable from reference sites, the grand mean length for nekton measured at all sites in
the Bay was negative suggesting that nekton growth at the formerly Phragmites-dominated sites failed to meet the restoration
goals by the end of the study period. Thus, vegetation success criteria may not necessarily reflect recovery of animal related
success criteria.
... P. australis was targeted for removal, because it is considered a Bbiopollutant^in the U.S, that negatively influences the habitat value of tidal salt marshes for young nekton by elevating the marsh planform and filling in the microtopography of the marsh surface (Windham 1995;Weinstein and Balletto 1999;Able et al. 2003;Rooth et al. 2003). The former alters the hydroperiod, the latter influences access to the marsh plain by resident and young-of-year transient organisms (Boesch and Turner 1984;Rozas et al. 1988;Kneib 1997;Able and Hagen 2000). ...
Restoration of 4049 ha of tidal wetlands was required to offset nekton losses at a power facility located on Delaware Bay, USA. Vegetation coverage, the permitted criterion for success, was compared by meta-analysis to restoration trajectories for abundance and growth of dominant nekton during the same 17-year period at two reference and five restoration sites. Mean catch per unit effort (CPUE), at both upper Bay (former Phragmites australis dominated sites) and lower Bay (former salt hay farms), were generally indistinguishable from those of the reference sites, and Hedge’s d for all sites suggested that numbers of individuals at restored locations did not differ significantly from those at the reference sites. Mean length distributions of dominant nekton in the upper Bay, however, were negative for all restoration sites combined by the end of the study. Although growth of nekton at the lower Bay restoration sites was indistinguishable from reference sites, the grand mean length for nekton measured at all sites in the Bay was negative suggesting that nekton growth at the formerly Phragmites-dominated sites failed to meet the restoration goals by the end of the study period. Thus, vegetation success criteria may not necessarily reflect recovery of animal related success criteria.
... (Common Reed; hereafter Phragmites) (Rogalski and Skelly 2012). and herpetofaunal communities (Able et al. 2003, Fell et al. 2003, Meyer 2003. Therefore, we hypothesized that areas impacted by Phragmites represented lowerquality habitat for SGCN and would have reduced diversity and altered community structure. ...
Effective management of wetlands often involves the suppression of invasive species, and understanding the ecological consequences of management efforts is an important goal. A non-native strain of Phragmites australis (Common Reed; hereafter Phragmites) is aggressively invading North American wetlands, and the species has been shown to alter hydrology and impact aquatic organisms. Clear Creek Wildlife Management Area, in Kentucky, is heavily impacted by Phragmites invasion. Portions of the Wildlife Management Area with Phragmites were treated with herbicide to restore wetland flora, and in this study, we evaluated the effects of both the presence and management of Phragmites on wildlife populations and ecosystem function. We selected 3 locations (treated Phragmites, untreated Phragmites, and Phragmites-free) and surveyed each for water chemistry, wildlife populations, and stable-isotope signatures over a 2-y period. Water chemistry varied with the presence or absence of Phragmites, suggesting differences in nutrient cycling. Fish diversity did not differ among sites, but individual species varied in distribution and abundance between the Phragmites sites and the Phragmites-free site. Turtles showed significant differences in both diversity and body size based on the presence or absence of Phragmites, but not herbicide treatment. We detected no significant differences in frog diversity across treatments. We recorded 8 Kentucky Species of Greatest Conservation Need, but there were few differences in the distribution of these species across sites. Stable-isotope analysis revealed variation in food-web structure based on the presence of Phragmites. These results indicate that herbicides had little effect on fish and herpetofaunal communities in the short term, but potentially significant ecological changes may occur if Phragmites were eradicated. Our conclusions highlight the importance of monitoring habitat restoration to guide future management. A holistic, ecosystem-level approach is necessary to understand the impacts of both invasive species and their management.
... Invasive plants alter the systems they are invading through changing vegetation structure, soil characteristics, fire regimes, hydrology, or biotic interactions (Levine et al., 2003). These structural and hydrological changes have substantial faunal impacts including reductions in bird nesting habitat, limiting nekton access to intertidal habitat used for feeding, refuge, and reproduction, and altering energy flow from herbivores to higher trophic levels in the invaded habitat (Able, Hagan, and Brown, 2003;Benoit and Askins, 1999;Gratton and Denno, 2006;Osgood et al., 2003). The structure characteristics of flora and fauna in mangrove wetlands had been changed after the Spartina invasions. ...
Gao, X.; Wang, M.; Wu, H.; Wang, W., and Tu, Z., 2018. Effects of Spartina alterniflora invasion on the diet of mangrove crabs (Parasesarma plicata) in the Zhangjiang Estuary, China.
Spartina alterniflora, an exotic invasive plant, has become the most serious threat colonizing mangrove areas in China in the past two decades. The diets of a dominant mangrove crab, Parasesarma plicata, in two mangrove habitats (Kandelia obovata forest and Avicennia marina forest) and adjacent S. alterniflora marsh in a subtropical mangrove estuary in Fujian, China, were investigated using stable isotopes, while a feeding experiment was carried out. The results showed that in the Avicennia forest, Parasesarma was herbivorous, feeding mainly on macroalgae. In the Kandelia forest, the contribution of mangrove leaves, macroalgae, and sediment to the diet of Parasesarma were about 75.5%, 24.2%, and 0.2%, respectively. While Parasesarma had a higher δ¹³C value and also a higher δ¹⁵N value in the Spartina marshes relative to the two mangrove habitats, suggesting that they were feeding on Spartina detritus as well as some small invertebrates. The feeding experiment showed that the δ¹³C value of Parasesarma after 90-day feeding only on Spartina leaves was very close to the δ¹³C value of the crab caught from the Spartina marshes, indicating that Spartina was the main carbon source. These results demonstrated that the invasion of Spartina has changed the main food resources of native crabs by providing food resources, which could affect the impact of crabs as ecological engineers and eventually affect the integrity and function of native ecosystems.
... Invasive P. australis has also invaded freshwater habitats, roadside ditches, and other disturbed areas (Marks et al. 1994;Saltonstall 2002). Invasive P. australis alters estuarine ecosystems via impacts on nutrient cycling and marsh elevation, and it can negatively affect associated fauna including birds and fish (Keller 2000;Talley and Levin 2001;Burdick and Konisky 2003;Able et al. 2003;Minchinton et al. 2006). Invasive P. australis is generally viewed as a nuisance, and has become the focus of labor-intensive and expensive management or eradication efforts (Martin and Blossey 2013;Hazelton et al. 2014). ...
Phenotypic variation within species can have community- and ecosystem-level effects. Such variation may be particularly important in ecosystem engineers, including many invasive species, because of the strong influence of these species on their surrounding communities and environment. We combined field surveys and glasshouse experiments to investigate phenotypic variation within the invasive common reed, Phragmites australis, among four estuarine source sites along the east coast of North America. Field surveys revealed variation in P. australis height and stem density among source sites. In a glasshouse environment, percent germination of P. australis seeds also varied across source sites. To test the degree to which phenotypic variation in P. australis reflected genetic or environmental differences, we conducted a glasshouse common garden experiment assessing the performance of P. australis seedlings from the four source sites across a salinity gradient. Populations maintained differences in morphology and growth in a common glasshouse environment, indicating a genetic component to the observed phenotypic variation. Despite this variation, experimentally increased porewater salinity consistently reduced P. australis stem density, height, and biomass. Differences in these morphological metrics are important because they are correlated with the impacts of invasive P. australis on the ecological communities it invades. Our results indicate that both colonization and spread of invasive P. australis will be dependent on the environmental and genetic context. Additional research on intraspecific variation in invasive species, particularly ecosystem engineers, will improve assessments of invasion impacts and guide management decisions in estuarine ecosystems.
... European lineages of Phragmites have invaded wetlands and disturbed habitats across North America (Saltonstall 2002;Kettenring and Mock 2012;Lambertini et al. 2012a;Meyerson and Cronin 2013). It is considered invasive and undesirable by many wetland managers because of its rapid spread (e.g., McCormick et al. 2010a, b;Vanderlinder et al. 2013), its negative impacts on native vegetation and wildlife habitat, its potential as a fire hazard, and its negative effects on property values (Marks et al. 1994;Keller 2000;Able et al. 2003;Minchinton et al. 2006;Kettenring et al. 2012a). However, there are benefits of this species to some wildlife species, nutrient removal, and buffering the effects of sea level rise in coastal wetlands (Kettenring et al. 2012a;Kiviat 2013). ...
Spread rates of invasive plant species depend heavily on variable seed/seedling survivorships over various habitat types as well as on variability in seed dispersal induced by rapid transport of propagules in open areas and slow transport in vegetated areas. The ability to capture spatial variability in seed survivorship and dispersal is crucial to accurately predict the rate of spread of plants in real world landscapes. However, current analytic methods for predicting spread rates are not suited for arbitrary, spatially heterogeneous systems. Here, we analyze invasion rates of the invasive plant Phragmites australis (common reed) over variable wetland landscapes. Phragmites is one of the most pervasive perennial grasses, outcompeting native vegetation, providing poor wildlife habitat, and proving difficult to eradicate across its invasive range in North America. Phragmites spreads sexually via seeds and asexually via underground (rhizomes) and aboveground (stolons) stems. We construct a structured integrodifference equation model of the Phragmites life cycle capturing variable seed survivorship in a seed bank, sexual and asexual recruitment into a juvenile age class, and differential competition among all classes with adults. The demographic model is coupled with a homogenized ecological diffusion/settling seed dispersal model that allows for seed deposition that varies with habitat type. The dispersal kernel we develop does not require local normalization and can be implemented efficiently using standard computational techniques. The model generates a traveling wave of isolated patches, establishing only in suitable habitats. We use the method of multiple scales to predict invasion speed as a solvability condition at large scales and test the predictions numerically. Accurate predictions are generated for a wide range of landscape parameters, indicating that invasion speeds can be understood in landscapes of arbitrary structure using this approach.
... Major issues facing wetland habitats include long-term changes in land cover and land use (generally including agricultural activities, habitat destruction, encroachment, and historic diking of estuarine habitat) [6], shoreline hardening, shoreline erosion, and shoreline alterations anthropogenically induced to change the structure and function of the actual marsh surface such as hydrology, marsh topography, plant community, nutrient retention, tidal flooding, detritus accumulation, and availability to secondary producers [7][8][9][10][11]. ...
... Phragmites is a tall (2-4 m), clonal, perennial grass, found in freshwater and brackish wetlands and moist, disturbed habitats . Although Phragmites may provide some important ecosystem services (Kiviat 2013), it is generally viewed unfavorably by wetland managers because it creates dense monocultures which often replace native wetland vegetation, altering plant diversity, and negatively impacts habitat for many wildlife species (Keller 2000;Able et al. 2003;Silliman and Bertness 2004;Chambers et al. 2008). In Great Salt Lake (GSL) wetlands, dense monocultures of invasive Phragmites have greatly reduced the habitat quality of wetlands for migratory waterfowl and shorebirds Vanderlinder et al. 2014). ...
The introduced grass Phragmites australis (hereafter Phragmites) is one of the most widespread invasive plants in North American wetlands. Phragmites has been extensively studied in some regions of North America, such as the Chesapeake Bay and the Great Lakes. However, little research has evaluated the extent of Phragmites invasion in the Intermountain West and the environmental drivers that have promoted its spread, particularly in the critically important Great Salt Lake (GSL) wetlands. Here we use high-resolution multispectral imagery to map the current distribution of Phragmites around GSL. We then identify factors associated with Phragmites presence in GSL using a species distribution model using the Random Forest algorithm. We contrast these findings with what is known about Phragmites invasion in other regions. We estimate that Phragmites occupies over 93 km2 around GSL. Phragmites was more likely to be found in wetland areas close to point sources of pollution, at lower elevations with prolonged inundation, and with moderate salinities. Results from our study will assist wetlands managers in prioritizing areas for Phragmites monitoring and control by identifying likely areas of prime Phragmites habitat.
... In coastal wetlands, marsh plains are dotted with small pools that benefit wetland food webs. In contrast, non-native Phragmites australis (common reed), an aggressive invader, eliminates pool-flat heterogeneity, causing lower macroinvertebrate diversity (Angradi et al. 2001) and reduced nursery, reproduction, and feeding support functions for fishes (Able et al. 2003). ...
Theory and Application
• Theory relevant to habitat heterogeneity in restoration comes from work on ecological niches, fractal dynamics, and mechanisms of species coexistence.
• Habitat heterogeneity is a key factor in landscape, ecosystem, and community processes across aquatic and terrestrial systems.
• Heterogeneity encompasses not only visible structural aspects of heterogeneity, but also spatial variation in soil properties, chemistry, and other features.
• Heterogeneity is predicted to be an important influence on biodiversity and ecosystem function in restored systems. Further research is needed to understand fundamental cause-effect relationships and to improve methods for incorporating appropriate heterogeneity into restoration.
... In contrast to the high species richness and abundance of waterfowl at the urbanized wetlands in apparently poor condition, other reports for New England salt marshes suggest that degraded salt marshes provide poor breeding habitat for marsh specialists such as seaside and sharp-tailed sparrows (i.e., Ammodramus maritimus and A. caudacutus; e.g., Stoll and Golet 1983; Reinert and Mello 1995; Brawley et al. 1998). In addition, in highly altered marshes the lower plant species richness and the trend toward a more homogenous landscape dominated by tall S. alterniflora and the invasive P. australis lowers the habitat value for some fish and bird species (Benoit and Askins 1999; Deegan 2002; Able et al. 2003). Seaside and sharp-tailed sparrows are two of only four species of passerine birds that breed regularly in RI salt marshes (Stoll and Golet 1983). ...
In southern New England, salt marshes are exceptionally vulnerable to the impacts of accelerated sea level rise. Regional rates of sea level rise have been as much as 50 % greater than the global average over past decades, a more than fourfold increase over late Holocene background values. In addition, coastal development blocks many potential marsh migration routes, and compensatory mechanisms relying on positive feedbacks between inundation and sediment deposition are insufficient to counter inundation increases in extreme low-turbidity tidal waters. Accordingly, multiple lines of evidence suggest that marsh submergence is occurring in southern New England. A combination of monitoring data, field re-surveys, radiometric dating, and analysis of peat composition have established that, beginning in the early and mid-twentieth century, the dominant low-marsh plant, Spartina alterniflora, has encroached upward in tidal marshes, and typical high-marsh plants, including Juncus gerardii and Spartina patens, have declined, providing strong evidence that vegetation changes are being driven, at least in part, by higher water levels. Additionally, aerial and satellite imagery show shoreline retreat, widening and headward extension of channels, and new and expanded interior depressions. Papers in this special section highlight changes in marsh-building processes, patterns of vegetation loss, and shifts in species composition. The final papers turn to strategies for minimizing and coping with marsh loss by managing adaptively and planning for landward marsh migration. It is hoped that this collection offers lessons that will be of use to researchers and managers on coasts where relative sea level is not yet rising as fast as in southern New England.
... Restoration of degraded ecosystems has been described as the ''acid test'' of ecological knowledge (Egan 2001) making management efforts to remove invasive plants and restore native communities both a practical matter and a research opportunity. A number of studies have shown that the negative effects of invasive P. australis are reversible for some plant, fish and insect communities (Farnsworth and Meyerson 1999;Able et al. 2003;Gratton and Denno 2006;Hunter et al. 2006;Dibble and Meyerson 2012. Many restoration and management efforts for P. australis have used mechanical and chemical approaches and have been long-term and large-scale (Marks et al. 1994;Hazelton et al. 2014), yielding a wealth of information. ...
The cosmopolitan reed grass Phragmites australis (Poaceae) is an intensively studied species globally with a substantial focus in the last two decades on its invasive populations. Here we argue that P. australis meets the criteria to serve as a model organism for studying plant invasions. First, as a dominant species in globally important wetland habitats, it has generated significant pre-existing research, demonstrating a high potential for funding. Second, this plant is easy to grow and use in experiments. Third, it grows abundantly in a wide range of ecological systems and plant communities, allowing a broad range of research questions to be addressed. We formalize the designation of P. australis as a model organism for plant invasions in order to encourage and standardize collaborative research on multiple spatial scales that will help to integrate studies on the ecology and evolution of P. australis invasive populations, their response to global environmental change, and implications for biological security. Such an integrative framework can serve as guidance for studying invasive plant species at the population level and global spatial scale.
Oligohaline Phragmites australis and Spartina alterniflora marshes with similar physical conditions were examined within two different geographic regions: 1) related to marsh nekton and marsh-edge finfish species abundance, biomass and community structure, 2) to determine whether marsh functional patterns are consistent over large-scale geographic settings, and 3) to assess consistency of nekton use for each macrophyte type between geographic regions. Few significant differences regarding abundance, biomass, community structure, and catch composition between P. australis and S. alterniflora marshes for marsh nekton and marsh-edge finfish species were observed. P. australis and S. alterniflora marshes, regardless of geographic region, provided similar functions for marsh nekton and estuarine finfish communities. However, differences between Chesapeake Bay and North Carolina geographic regions for marsh nekton use were pronounced. Significantly more nekton species utilized P. australis and S. alterniflora marshes in North Carolina versus Chesapeake Bay. Also, the abundance of seven of 12 marsh nekton species common to both regions within S. alterniflora marshes, and four of 12 species within P. australis marshes, differed significantly between regions. It is important to consider at what point differences between estuarine habitats warrant the selection of one functional habitat over another, or conversion of functional habitat for restoration of another. Instead of determinations based on one or a few species of interest, clearly defined criteria should be used to determine necessity for replacement of one habitat type for another, and these should consider ecological values and attributes necessary for ecosystem function.
Biological invasion has been one of the reasons that coastal wetlands gradually lose their ecological services. The current study investigates the spread of a commonly found invasive species in coastal wetlands in Northeastern US, the Phragmites australis. Within a relatively pristine wetland complex in coastal New Jersey, we collected high-resolution multispectral remote sensing images for eight years (2011–2018), in both winter and summer seasons. The land cover/land use status in this wetland complex is relatively simple, contains only five identifiable vegetation covers and water. Applying high accuracy machine learning algorithms, we are able to classify the land use/land cover in the complex and use the classified images as the basis for the grey system coupled system dynamics simulative model. The simulative model produces land use land cover change in the wetland complex for the next 25 years. Results suggest that Phragmites australis will increase in coverage in the future, despite the stable intensity of anthropogenic activities. The wetland complex could lose its essential ecological services to serve as an exchange spot for nekton species from the sea.
Large-scale wetland reforestation and hydrologic restoration projects have been implemented worldwide though few have been well studied or monitored following restoration. Many are located in the United States where laws require restoration to compensate for the loss of aquatic and wetland resources. Many projects are in coastal areas or deltas where the rate of wetland loss is great and where water and sediment are available to restore hydrology and build (wet)lands. Seven examples are presented: saline tidal marshes (2), inland freshwater marshes (2), delta wetlands (2), and mangrove reforestation (1). Techniques range from large-scale plantings to river diversions, and nearly all require reintroduction of hydrology. Large restoration projects often involve rewetting with river water (marshes of Mesopotamia (Iraq) and Yellow River Delta (China)), and/or sediment (Louisiana, United States). Perhaps the largest wetland restoration project in the world, the Florida Everglades, is a restoration in progress that may not be completed for another 60 years.
Coastal wetlands including salt marshes are among the most productive ecosystems on Earth. They are known for improving the quality of coastal water and provisioning coastal fisheries. However, this ecosystem is under potential threat due to urban coastal land reclamation, limited sediment supply, increased nutrient/eutrophication, and sea level rise. Therefore, restoration efforts to protect the degraded salt marsh habitat are considerably increasing worldwide. In this paper, we present an overview of salt marsh restoration techniques and success indicators. Published scientific literature in English language was collected by searching the most relevant keywords from popular search engines, namely, Google Scholar, Scopus, and Mendeley to get the information about salt marsh restoration techniques and success indicators. This study comprehensively reviewed data from 78 peer-reviewed papers. Results indicated that much of the salt marsh was restored through assisted abiotic strategies (e.g., recovery of tidal exchange, managed realignment, and sediment level amendment). A total of 214 indicators were found, spanning over six major ecological attributes such as structural diversity, ecosystem functions, physical conditions, species composition, external exchange, and absence of threat. Author keywords analysis revealed several hotspots for recent research (e.g., 16 s rRNA, fungi, microbial communities, carbon accumulation, and blue carbon). This paper proposes a model for restoring degraded salt marsh, as well as tracking their success. The information presented here will assist the marine ecosystem restoration practitioners in getting a comprehensive understanding of salt marsh restoration success evaluation.
The patterns of reproduction and ontogeny in the taxonomically rich estuary- associated fishes from around the world, including all the major groups from elasmobranchs to bony fishes, are as diverse as documented for fishes living in other ecosystems. Further, the diversity in the life histories of bony fishes, the dominant group in estuaries, is complex with egg, larval, juvenile and adult stages having different ecologies. Moreover, some stages that use estuaries also use the adjacent, downstream ocean and upstream
freshwaters for parts of their life history. Given these complexities in patterns and modes of reproduction, it is not surprising that recruitment processes of estuary- associated fishes are also diverse. In Introduction, we listed six broad topic areas that framed the scope of the chapter. We summarise major conclusions in the six areas.
In New England saltmarshes, mummichogs (Fundulus heteroclitus) connect the vegetated marsh and creek food webs by opportunistically foraging on the invertebrate communities of the marsh surface when access is permitted by tidal flooding and marsh-edge geomorphology. Via their movements, mummichog represent a critical food web node, as they can potentially transport energy from the marsh surface food web to creek food web and exert top-down control on the communities of the vegetated marsh surface. Here, we demonstrate that access to the marsh surface (afforded by marsh-edge geomorphology) did not impact mummichog distribution across the marsh platform and exhibited no evidence of top-down control on their invertebrate prey. Thus, mummichogs function as initial nodes in the trophic relay, unidirectionally moving energy from the vegetated marsh to the creek food web. Reduced marsh surface access via altered marsh-edge geomorphology results in a 50% to 66% reduction in total energy available to aquatic predators via this route. Estuarine systems are intimately connected to coastal and offshore systems via consumer mediated flows of energy; thus, disruptions to the trophic relay from the marsh surface at the tidal creek scale can have far reaching impacts on secondary productivity in multiple disparate systems and must be accounted for in considerations of impacts to future food-web function.
Salt marshes are highly dynamic and important ecosystems that dampen impacts of coastal storms and are an integral part of tidal wetland systems, which sequester half of all global marine carbon. They are now being threatened due to sea-level rise, decreased sediment influx, and human encroachment. This book provides a comprehensive review of the latest salt marsh science, investigating their functions and how they are responding to stresses through formation of salt pannes and pools, headward erosion of tidal creeks, marsh-edge erosion, ice-fracturing, and ice-rafted sedimentation. Written by experts in marsh ecology, coastal geomorphology, wetland biology, estuarine hydrodynamics, and coastal sedimentation, it provides a multidisciplinary summary of recent advancements in our knowledge of salt marshes. The future of wetlands and potential deterioration of salt marshes is also considered, providing a go-to reference for graduate students and researchers studying these coastal systems, as well as marsh managers and restoration scientists.
Evidence for relative sea-level rise in the Mullica River-Great Bay, a relatively undisturbed watershed in southern New Jersey, stretches over hundreds of years. The increase in global sea-level rise in the region is enhanced by subsidence and results in rates that are approximately double the global average. In recent decades, the occurrence of “ghost forests,” standing dead forests, especially of the salt-intolerant Atlantic White Cedar, is becoming increasingly obvious as tidal inundation of salty waters increases further inland, especially in the upper portions of the Mullica River and its tributaries. Even older evidence of sea-level rise in the watershed is the subtidal and intertidal occurrence of “cedar cemeteries,” i.e., buried accumulations of Atlantic white cedar stumps and timbers that have been radiocarbon-dated from the fifteenth to the sixteenth centuries to as old as the fifth century. Some of these are being exposed as rising water extends intertidal creeks into adjacent wetlands and uncovers this rot-resistant wood. Sea-level rise is perhaps the most significant threat to the persistence of salt marshes over the coming century. Sea-level rise decreases salt marsh area by erosion at the marsh edge, drowning of the marsh surface, and the expansion of marsh pools into larger marsh “lakes.” In some instances, this loss of salt marshes is compensated for by expansion landward into ghost forests, but in this watershed and others, the expansion is by invasive plant species such as Phragmites australis, which is suboptimal habitat for fishes, crabs, and other invertebrates. The combination of a fast rate of sea-level rise in an area relatively free from recent human intervention makes the Mullica Valley watershed an ideal location to continue to evaluate the effects of sea-level rise on salt marsh ecosystems.
Biological invasions resulting from anthropogenic activities are one of the greatest threats to maintaining ecosystem functioning and native biodiversity. Invasions are especially problematic when the invading species behaves as an ecosystem engineer that is capable of transforming ecosystem structure, function, and community dynamics. Of particular concern is the spread of emergent wetland grasses whose root systems alter hydrology and structural stability of soils, modify ecosystem functions, and change community dynamics and species richness. To address the threats posed to ecosystems across the globe, management practices focus on the control and removal of invasive grasses. However, it remains unclear how severely invasive grasses alter ecosystem functions and whether alterations persist after invasive grass removal, limiting our ability to determine if management practices are truly sufficient to fully restore ecosystems. Here, we conducted a meta-analysis to quantify ecological alterations and the efficacy of management following the invasion of Spartina alterniflora and Phragmites australis, two common and pervasive invaders in coastal wetlands. Our results indicate that S. alterniflora and P. australis significantly alter measures of ecosystem functioning and organismal abundance. Invaded ecosystems had significant elevations in abiotic carbon and nitrogen fixation and uptake in areas with invasive grasses, with differential photosynthetic pathways of these two grass species further explaining carbon fluxes. Moreover, evidence from our analyses indicates that management practices may not adequately promote recovery from invasion, but more data are needed to fully assess management efficacy. We call for future studies to conduct pairwise comparisons between uninvaded, invaded, and managed systems and provide research priorities.
Flood mitigation and protection of coastal infrastructure are key elements of coastal management decisions. Similarly, regulating and provisioning roles of coastal habitats have increasingly prompted policy makers to consider the value of ecosystem goods and services in these same decisions, broadly defined as “the benefits people obtain from ecosystems.” We applied these principles to a study at three earthen levees used for flood protection. By restricting tidal flows, the levees degraded upstream wetlands, either by reducing salinity, creating standing water, and/or by supporting monocultures of invasive variety Phragmites australis. The wetlands, located at Greenwich, NJ, on Delaware Bay, were evaluated for restoration in this study. If unrestricted tidal flow were reestablished with mobile gates or similar devices, up to 226 ha of tidal salt marsh would be potentially restored to Spartina spp. dominance. Using existing literature and a value transfer approach, the estimated total economic value (TEV) of goods and services provided annually by these 226 ha of restored wetlands ranged from 2,390,854 y−1. The associated annual engineering cost for including a mobile gate system to fully restore tidal flows to the upstream degraded wetlands was about $1,925,614 y−1 resulting in a benefit-cost ratio range of 0.98–1.14 over 50 years (assuming no wetland benefits realized during the first 4 years). Thus, inclusion of a cost-effective mobile gate system in any engineering design to improve long-term flood resilience in the region would produce dual benefits of protecting people and property from major storms, while preserving and enhancing ecosystem values.
Fungal endophytes can improve plant tolerance to abiotic stress. However, the role of these plant–fungal interactions in invasive species ecology and their management implications remain unclear. This study characterized the fungal endophyte communities of native and invasive lineages of Phragmites australis and assessed the role of dark septate endophytes (DSE) in salt tolerance of this species. We used Illumina sequencing to characterize root fungal endophytes of contiguous stands of native and invasive P. australis along a salinity gradient. DSE colonization was assessed throughout the growing season in the field, and effects of fungal inoculation on salinity tolerance were investigated using laboratory and greenhouse studies. Native and invasive lineages had distinct fungal endophyte communities that shifted across the salinity gradient. DSE colonization was greater in the invasive lineage and increased with salinity. Laboratory studies showed that DSE inoculation increased P. australis seedling survival under salt stress; and a greenhouse assay revealed that the invasive lineage had higher aboveground biomass under mesohaline conditions when inoculated with a DSE. We observed that P. australis can establish mutualistic associations with DSE when subjected to salt stress. This type of plant–fungal association merits further investigation in integrated management strategies of invasive species and restoration of native Phragmites.
Classic bottom-up theory predicts that increased resource availability (for example, nutrients) at the base of the food web will stimulate primary production and, in turn, secondary production. Recent studies, however, indicate that bottom-up controls on food web production can be modified by other factors, such as landscape configuration and continuity. As part of a 10-year ecosystem-scale experiment in a New England salt marsh, we investigated the response of secondary consumers, specifically a fish, the mummichog (Fundulus heteroclitus), to nutrient enrichment. In the first 6 years, we observed a classic bottom-up response of increased production of algae, invertebrate prey, and mummichogs. After the sixth year, however, mummichog biomass declined to below reference levels by the eighth year. This decline in mummichog biomass coincided with nutrient-induced collapse of the low-marsh habitat. Based on stable isotope analyses, field surveys, and small-scale experiments, we suggest that the geomorphic changes induced a trophic decoupling between creek and marsh habitats, thereby reducing mummichog access to prey in the intermittently flooded marsh. Thus, despite continued stimulation of algal and invertebrate prey production, fish abundances declined to below pre-enrichment levels. Our results demonstrate how geomorphic controls can override classic bottom-up control and emphasize the importance of long-term studies in detecting the response of slow-turnover phenomena (for example, changing landscapes).
Heterogeneity is a key feature of wetland ecosystems, which vary physically, chemically, and biologically over space and time. Today, longstanding interest in how heterogeneity influences fundamental ecological processes is coupled with concern that anthropogenic changes are reducing the heterogeneity of wetland and other ecosystems. Spatial heterogeneity is apparent in wetlands at landscape, habitat, and micro scales. Variation can be gradual along environmental gradients or abrupt; even relatively small changes in wetlands can exert large influences through interactions with hydrology. Temporal heterogeneity is an important feature of wetlands, from the decadal or longer scales associated with vegetation succession to diurnal variability in water levels. Origins, effects, and applications of heterogeneity to wetland management are discussed, with a focus on the spatial dimension of wetland heterogeneity at the habitat scale. © Springer Science+Business Media B.V., part of Springer Nature 2018. All rights reserved.
Alteration of estuarine shorelines associated with increased urbanization can significantly impact biota and food webs. This study determined the impact of shoreline alteration on growth and movement of the estuarine fish Fundulus heteroclitus in a tributary of the Delaware Coastal Bays. Fundulus heteroclitus is abundant along the east coast of the USA, and is an important trophic link between marsh and subtidal estuary. The restricted home range of F. heteroclitus allowed discrete sampling, and fish growth comparisons, along 35–65-m long stretches of fringing Spartina alterniflora and Phragmites australis marsh, riprap, and bulkhead. Fundulus heteroclitus were tagged with decimal Coded Wire Tags. Of 725 tagged F. heteroclitus, 89 were recaptured 30–63 days later. Mean growth rate (0.06–0.15 mm day⁻¹ across all shoreline types) was greatest at riprap, lowest at Spartina and Phragmites, and intermediate at bulkhead, where growth was not significantly different from any other shoreline. This suggests that discernible environments exist along different shoreline types, even at the scale of tens of meters. No difference in movement distance was detected at different shoreline types; most individuals displayed a high degree of site fidelity. Forty-seven percent were recaptured within 5 m of their tagging location, although alongshore movements up to 475 m were recorded. Estimates of relative F. heteroclitus productivity, using relative density data from a concurrent study, were highest along Spartina and Phragmites, intermediate at riprap, and lowest at bulkhead. Therefore, despite greater growth rates along riprap than at vegetated shores, armoring reduces abundance sufficiently to negatively impact localized productivity of F. heteroclitus.
Die ökologischen Effekte einer mosaikartigen winterlichen Rohrwerbung wurden untersucht. Dabei konnten der Bestand selber, die Vegetation, Fische, Amphibien und Vögel berücksichtigt werden. Phragmites-Halme wachsen nach eine Mahd in höheren Dichten, bleiben aber etwas kürzer. Durch die Methodik kam es an den seeseitigen Ausdehnungsfronten der Röhrichte zu mahbedingten Schäden am Schilf. Für die Fischbestände war kein Einfluss der Wintermahd erkennbar. Amphibien profitierten von der Mahd, und hielten sich auf den geschaffenen Flachwasserflächen auf. Bei den Vögeln zeigte sich eine erhöhte Artenvielfalt nach der Mahd, die freien Flachwasserflächen wurden als Habitat von vorher abwesenden Arten angenommen. Bei einer Schilfbrüter-Art zeigte sich eine Abnahme der vorher hohen Bestandsdichte.
Urbanization and industrial development pressures have seriously impacted coastal ecosystems, including vegetated intertidal and subtidal marine habitats such as barrier strands and associated wetlands and seagrasses. These ecosystems provide a suite of services including carbon storage, pollution and nutrient abatement, soil formation, fisheries support, and flood and storm protection. Emphasis has been placed on vegetated marine habitats that occur immediately adjacent to the Gulf of Mexico, including barrier islands and beaches, salt marshes and mangroves, seagrasses, intertidal and subtidal flats, and reed marshes at the mouth of the Mississippi River. These habitats, their depositional environments, and the ecology of their dominant flora and fauna are described within the context of major marine and terrestrial ecoregions. The information and analysis in this chapter should better enable effective management and restoration of coastal habitats in the Gulf as environmental change continues to alter their structure and function and reshape their associated biotic assemblages.
Anthropogenic modifications of estuarine environments, including shoreline hardening and corresponding alteration of water quality, are accelerating worldwide as human population increases in coastal regions. Estuarine fish species inhabiting temperate ecosystems are adapted to extreme variations in environmental conditions including water temperature, salinity, and dissolved oxygen across seasonal, daily, and hourly time scales. The present research utilized quantitative sampling to examine the spatiotemporal distribution of shore-zone estuarine fish species in association with four unique shoreline types across a range of water temperature and dissolved oxygen conditions. Fish were collected from the intertidal and shallow subtidal region of four shoreline types, Spartina alterniflora marsh, Phragmites australis marsh, riprap, and bulkhead, in the summer and fall of 2009 and 2010. Analyses were performed to (1) compare mean fish density among shoreline types across all water conditions and (2) explore relationships of the complete fish assemblage, three functional species groupings, and two fish species (Fundulus heteroclitus and Menidia menidia) to unique shoreline/water conditions. Significantly greater mean fish densities were found along S. alterniflora shorelines than armored shorelines. Several metrics including fish density, species richness, and occurrence rates suggest S. alterniflora shorelines may serve as a form of refuge habitat during periods of low dissolved oxygen and high temperatures for various species, particularly littoral-demersal species including F. heteroclitus. Potential mechanisms that could contribute to a habitat providing refuge during adverse water quality conditions include tempering of the adverse condition (decreased temperatures, increased dissolved oxygen), predation protection, and increased foraging opportunities.
Each year millions of larval and 0+ juvenile fishes are recruited into estuarine fish populations around the world. For several decades the roles of littoral aquatic and emergent macrophyte habitats as nursery areas for many of these species have been studied and debated at length. This review attempts to collate the published literature and provide a synopsis of the varying, and sometimes conflicting, views on this topic. A large number of studies have shown that a range of species and an abundance of juvenile fishes are associated with littoral macrophytes in estuaries, some of which are found almost exclusively within particular plant habitats. Other studies have shown the movement of certain juvenile fishes from one type of littoral plant habitat to another as they grow and develop new feeding strategies and dietary requirements. Overall, it would appear that seagrass beds and mangrove forests are particularly favoured by fishes as nursery areas in both estuaries and the nearshore marine environment, and that the loss of these habitats leads to a decline in juvenile fish diversity and abundance. Salt marshes and reed beds generally have a lower diversity of fishes than seagrass and mangrove habitats, possibly due to the more temperate location of salt marshes and the dense structure of some reed beds. Stable isotope studies in particular are providing increasing evidence that carbon assimilated by juvenile fishes in mangrove, marsh and reed habitats is not primarily derived from these macrophytes but comprises a mixture of these sources and a diverse range of macro- and microalgae, particularly epiphytic, epipsammic, epipelic and epilithic diatoms and algae found in these areas. The closest trophic link between the macrophyte food chain and associated fishes occurs in seagrass habitats where a significant portion of the overall macrophyte leaf biomass often consists of epiphytic algae and diatoms. Structurally, mangrove forests, salt marshes and reed beds provide more substantial and complex habitats for juvenile fish refuge, but some of these habitats are constrained with regard to nursery provision by being fully exposed at low tide. Under such circumstances the small fish are sometimes forced into creeks and channels where larger piscivorous fishes are often present. Overall, in terms of a broad ranking of the four habitats as potential fish nursery areas, seagrass meadows are ranked first, followed by mangrove forests, salt marshes and then reed beds. This ranking does not imply that the lower ranked habitats are unimportant, since these plants perform a myriad of ecosystem services that are not related to the provision of fish nursery areas, e.g. bank stabilization. It is also emphasized that the protection of specific plant species should not be encouraged because it is important to have an ecosystem approach to conservation so that the diversity of habitats and their connectivity for fishes is maintained.
Heterogeneity is a key feature of wetland ecosystems, which vary physically, chemically, and biologically over space and time. Today, longstanding interest in how heterogeneity influences fundamental ecological processes is coupled with concern that anthropogenic changes are reducing the heterogeneity of wetland and other ecosystems. Spatial heterogeneity is apparent in wetlands at landscape, habitat, and micro scales. Variation can be gradual along environmental gradients or abrupt; even relatively small changes in wetlands can exert large influences through interactions with hydrology. Temporal heterogeneity is an important feature of wetlands, from the decadal or longer scales associated with vegetation succession to diurnal variability in water levels. Origins, effects, and applications of heterogeneity to wetland management are discussed, with a focus on the spatial dimension of wetland heterogeneity at the habitat scale.
Hydrologic restriction of salt marshes and subsequent invasion by Phragmites australis could influence the reproductive success of Fundulus heteroclitus, a common salt marsh resident that forages and spawns on the marsh surface at flood tide. Previous research in our laboratory using data from 2010 to 2011 examined the proportion of actively spawning F. heteroclitus residing in altered New England salt marshes as part of a larger experiment to examine the physiological condition of fish in restricted and restored marshes relative to paired unrestricted (reference) sites. We detected a significant decrease in the proportion of actively spawning fish in restricted relative to paired unrestricted marshes, but no difference between restored and paired unrestricted marsh fish. In this manuscript, we conduct a re-analysis of a portion of that data (July 2011) to explore potential mechanisms behind previous results. Using forward stepwise selection and generalized linear mixed models, we determined that the reduction in actively spawning restricted marsh fish was due to a single predictor (lipid mass); there were no effects of water temperature, body size, parasite prevalence, parasite density, and growth rate on the response. Previous results indicate healthy restricted marsh fish already have reduced energy reserves. Since investment in oocytes is energetically costly (this analysis), the effect could manifest at the population level as a reduction in actively spawning fish. In addition, oocyte quality is reduced in restricted marshes (as measured by % lipid; 13.9 ± 1.6 % SD) relative to paired unrestricted marshes (15.9 ± 2.3 % SD). Although these data are preliminary and represent a single lunar cycle, additional studies are warranted to explore relationships between P. australis invasion, restoration, and effects on the fecundity of this ubiquitous salt marsh fish.
Large-scale wetland reforestation and hydrologic restoration projects have been implemented worldwide though few have been well studied or monitored following restoration. Many are located in the US where laws require restoration to compensate for the loss of aquatic and wetland resources. Many projects are in coastal areas or deltas where the rate of wetland loss is great and where water and sediment are available to restore hydrology and build (wet)lands. Five examples are presented: saline tidal marshes, inland freshwater marshes, delta wetlands (2), and mangrove reforestation. Techniques range from large-scale plantings to river diversions and nearly all require reintroduction of hydrology. Large restoration projects often involve rewetting with river water (marshes of Mesopotamia (Iraq) and Yellow River Delta (China), and/or sediment (Louisiana, USA)). Some projects such as in tidal marsh restoration (Delaware Bay, USA) were intensively monitored following restoration. For others, such as mangrove reforestation in the Mekong River Delta (Vietnam), little to no monitoring was conducted.
A large-scale wetland restoration case-study is discussed in response to fish losses in an open cycle, cooling water system at a generating facility located on Delaware Bay, USA. Stable isotope analyses of vegetation, resident and marine transient finfishes in marshes and open waters of the estuary are described, along with biochemical condition of individuals as it relates to habitat quality, and secondary production. Population dynamics of spot (Leiostomus xanthurus), a "target species" impacted by the generating facility was used to compare fish losses at the intake with new production of this species in the restored marshes. A "whole estuary" (or seascape) approach to restoration was adopted, one that integrates the concepts of donor control, linkages between tidal salt marshes, the marsh-estuary-coastal continuum and the recruitment success of marine transients. We emphasize that individual wetlands do not function in isolation; rather they are spatially explicit and functionally connected habitat mosaics incorporating ecological processes driven by organism behavior. Linkages among habitats that affect the growth and survival of earlier life stages therefore tend to be underplayed in restoration planning; but few species are confined to a single habitat; e.g., tidal salt marshes. In contrast, the findings of our seascape focused study demonstrated consistent and predictable animal density or productivity 'hotspots' in relation to spatial position within the seascape. Both ontogenetic habitat shifts, the use of transitory and temporary habitats, and the concept of the estuarine seascape are discussed in the context of restoring not just habitats, but also estuarine-coastal "connectivity". ©2016 by the Board of Regents of the University of Wisconsin System.
One of the world's largest tidal wetland restoration projects was conceived to offset the loss of nekton to once-through cooling at a power plant on Delaware Bay, USA. An aggregated food chain model was employed to estimate the area of tidal salt marsh required to replace these losses. The 5040 ha was comprised of two degraded marsh types – Phragmites-dominated marshes and diked salt hay farms – at eleven locations in oligo-mesohaline and polyhaline reaches of the estuary. At a series of `summits' convened with noted experts in the field, it was decided to apply an ecological engineering approach (i.e., `self design', and minimal intrusion) in a landscape ecology framework to the restoration designs while at the same time monitoring long-term success of the project in the context of a `bound of expectation'. The latter encompassed a range of reference marsh planforms and acceptable end-points established interactively with two advisory committees, numerous resource agencies, the permitting agency and multiple-stakeholder groups. In addition to the technical recommendations provided by the project's advisors, public health and safety, property protection and public access to the restored sites were a constant part of the dialogue between the utility, its consulting scientists and the resource/permitting agencies. Adaptive management was used to maintain the restoration trajectories, ensure that success criteria were met in a timely fashion, and to protect the public against potential effects of salt intrusion into wells and septic systems, and against upland flooding. Herbicide spray, followed by prescribed burns and altered microtopography were used at Phragmites-dominated sites, and excavation of higher order channels and dike breaching were the methods used to initiate the restorations at the diked salt hay farms. Monitoring consisted of evaluating the rate of re-vegetation and redevelopment of natural drainage networks, nekton response to the restorations, and focused research on nutrient flux, nekton movements, condition factors, trophic linkages, and other specific topics. Because of its size and uniqueness, the Estuary Enhancement Program as this project is known, has become an important case study for scientists engaged in restoration ecology and the application of ecological engineering principles. The history of this project, and ultimately the Restoration Principles that emerged from it, are the subjects of this paper. By documenting the pathways to success, it is hoped that other restoration ecologists and practitioners will benefit from the experiences we have gained.
Phragmites expansion rates (linear at 1–3% yr−1) and impacts of this expansion on high marsh macroinvertebrates, aboveground production, and litter decomposition fromPhragmites and other marsh graminoids were studied along a polyhaline to oligohaline gradient. These parameters, and fish use of creeks
and high marsh, were also studied inPhragmites control sites (herbicide, mowing, and combined herbicide/mow treatments).Phragmites clones established without obvious site preferences on oligohaline marshes, expanding radially. At higher salinities,Phragmites preferentially colonized creekbank levees and disturbed upland borders, then expanded into the central marsh. Hydroperiods,
but not salinities or water table, distinguishedPhragmites-dominated transects. Pooled samples ofPhragmites leaves, stems, and flowers decompose more slowly than other marsh angiosperms;Phragmites leaves alone decompose as or more rapidly than those of cattail. AbovegroundPhragmites production was 1,300 to 2,400 g m−2 (about 23% of this as leaves), versus 600–800 g m−2 for polyhaline to mesohaline meadow and 1,300 g m−2 for oligohaline cattail-sedge marsh. Macroinvertebrates appear largely unaffected byPhragmites expansion or control efforts; distribution and densities are unrelated to elevation or hydroperiod, but densities are positively
related to litter cover. Dominant fish captured leaving flooded marsh wereFundulus heteroclitus andAnguilla rostrata; both preyed heavily on marsh macroinvertebrates.A. rostrata andMorone americana tended to be more common inPhragmites, but otherwise there were no major differences in use patterns betweenPhragmites and brackish meadow vegetation. SAV and macroalgal cover were markedly lower within aPhragmites-dominated creek versus one withSpartina-dominated banks. The same fish species assemblage was trapped in both plus a third within the herbicide/mow treatment. Fish
biomass was greatest from theSpartina creek and lowest from thePhragmites creek, reflecting abundances ofF. heteroclitus. Mowing depressedPhragmites aboveground production and increased stem density, but was ineffective for control.Phragmites, Spartina patens, andJuncus gerardii frequencies after herbicide-only treatment were 0.53-0.21; total live cover was
We examined the nursery role of salt marshes for transient nekton by searching the literature for data on density, growth, and survival of juvenile fishes and decapod crustaceans in marshes and using meta-analyses to test hypotheses. We analyzed density data from 32 studies conducted throughout the world, Based on fish density, habitat types could be ranked from highest to lowest as: seagrass > vegetated marsh edge, nonvegetated marsh, open water, macroalgae, oyster reefs > vegetated inner marsh. However, patterns of habitat use varied among the 29 fish species represented. For decapod crustaceans (seven species), habitat types were ranked: seagrass > vegetated marsh edge > nonvegetated marsh, vegetated inner marsh, open water, macroalgae > oyster reef. We identified only 5 comparative studies on transient nekton growth in salt marshes. Fish growth in nonvegetated salt marsh was not significantly different from growth in open water or in macroalgae beds but was significantly lower than in seagrass. Growth of decapod crustaceans was higher in vegetated marsh than in nonvegetated marsh. Nekton survival in salt marsh (11 studies analyzed) was higher than in open water, lower than in oyster reef/cobble and not significantly different from survival in seagrass. When density, growth and survival are all considered, the relative nursery value of salt marshes for nekton appears higher than open water but lower than seagrass. Vegetated marsh appears to have a higher nursery value than nonvegetated marsh; however, tidal dynamics and nekton movement among marsh components complicates these comparisons. The available data have a strong geographical bias; most studies originated in the northern Gulf of Mexico or on the Atlantic coast of the United States. This bias may be significant because there is some evidence that salt marsh nursery value is dependent on geography, salinity regimes and tidal amplitude.
We compared nekton densities over a range of measured flooding conditions and locations withinPhragmites australis andSpartina alterniflora (salt marsh cordgrass) at the Charles Wheeler Salt Marsh, located on the lower Housatonic River estuary in southwestern Connecticut.
Nekton were sampled on nine spring high tide events from May to October 2000 using bottomless lift nets positioned between
0–5 and 10–20 m from the creek edge. Flooding depth, duration, and frequency were measured from each vegetation type during
each sampling month. Benthic macroinvertebrate density was also measured within each vegetation type in May, July, and September.
Frequency of flooding was 52% lower and flooding depth and duration were also significantly reduced inP. australis relative toS. alterniflora. A total of 4,197 individuals representing 7 species, mostlyPalaemonetes pugio (dagger-blade grass shrimp) andFundulus heteroclitus (common mummichog), were captured.P. pugio densities were significantly greater inS. alterniflora as were benthic macroinvertebrate density and taxa richness during May, but not during June or October. Total fish density
was not significantly different betweenP. australis andS. alterniflora and was independent of location on the marsh. Significantly more juvenileF. heteroclitus were collected withinS. alterniflora relative toP. australis in June and July, suggesting that recruitment of this species may be lower inP. australis habitat. Fish density generally did not vary predictably across the range of flooding depth and duration; there was a positive
relationship between flooding depth and fish density inS. alterniflora. The measured reduction in flooding frequency (52%) withinP. australis at the Housatonic site would result in an average total monthly fish use, expressed as density, of 447 ind m−2 forP. australis and 947 ind m−2 forS. alterniflora. WhenP. australis expansion results in reduction of flooding frequency and duration, nekton community composition can change, access to the
marsh surface is reduced twofold, and nursery habitat function may be impaired.
Tidal energy available for geomorphic work decreases with distance upstream from tidal sources. Headward areas of drainage systems are transitional between tidal and biogenic influences. Levees that develop from inorganic sediment transported by tides are absent in upstream reaches. Contributions of inorganic sediment to soil devel opment are restricted to areas near channel banks. Peat increased from 10 to 45% of total soil weight within 15m of a third order channel. The form of channels in cross section and profile varies in relation to tidal range. Where the full range is exhibited, the ratio of channel width to depth is greater than unity. Where thalweg elevation exceeds mean low tide level, the ratio is less than unity. Although thalweg gradient increases upstream, the relation of width to distance was found to be nearly constant between upstream and downstream reaches (2.6 cf. 2.8m width change per 1000m length, respectively). Overall configuration of channel networks is affected by vegetation that regulates the distribution of tidal energy in headward reaches. Plant growth that constricts the cross section of a first order channel initiates its retrogression, which involves the formation of subterranean channels, potholes, and channel pans. The tidal prism displaced by retrogression is accommodated elsewhere by headward erosion. Differences in tidal schedule between opposing drainage systems represent potential hydraulic gradients across drainage divides. When headward erosion causes channel capture, the zone of flood tide convergence shifts towards the channel with the later schedule. The result is a channel that is continuous between two tidal sources. Eventually, a new divide is formed by rapid sedimen tation within the convergence zone. Drainage divides are often occupied by 'turf pans' that function as water storage compartments and result from intrinsic variability in plant productivity. Each physiographic feature of the marsh plain is distributed within a predictable narrow range of elevation.
We conducted a study to determine the trophic pathways leading to juvenile fish in 2 mesohaline tidal marshes bordering Delaware Bay. The relative roles of the major primary producers in supplying energy, ultimately, to the mummichog Fundulus heteroclitus were assessed by measuring the stable isotopic compositions of juveniles (21 to 56 mm total length, TL; most of which were young-of-the-year) and those of macrophyte vegetation, phytoplankton, and benthic microalgae at each site. We collected samples of primary producers and F. heteroclitus, the dominant fish species in this and other marshes along the east coast of the USA, in June and August 1997, at 2 study sites (upstream and downstream) within Mad Horse Creek (a Spartina alterniflora-dominated site) and Alloway Creek (a Phragmites australis-dominated site), for a total of 4 study sites. Our results indicate that F. heteroclitus production is based on a mixture of primary producers, but the mixture depends on the relative abundance of macrophytes. In S. alterniflora-dominated marshes, C and S isotope ratios indicate that F. heteroclitus production is supported by S, alterniflora production (ca 39%, presumably via detritus), while in P. australis-dominated marshes, secondary production is based upon P. australis (73%). To our knowledge, this finding provides the first evidence that P. australis may contribute to aquatic food webs in tidal marshes. Benthic microalgae also contribute to the food chain that leads to F. heteroclitus in both marsh types, while phytoplankton may be of lesser importance. Benthic microalgal biomass was lower in the P, australis-dominated system, consistent with a greater effect of shading in P, australis- versus S. alterniflora-based creek systems. Based on the difference in nitrogen isotope values between F. heteroclitus and the primary producers, the trophic level of F. heteroclitus appears to be similar in the 2 marsh types, despite the differing vegetation types. In summary, the relative roles of the primary producers in supplying energy to F. heteroclitus varies locally and, in particular, with respect to the type of marsh macrophyte vegetation.
This paper reviews the origin and development of New England salt marshes. The authors present vegetation patterns and dynamics in light of new data and evaluate the complex of interacting factors influencing the patterns. They consider man's impacts and make recommendations for maintaining marsh integrity.
A critical link missing from our understanding of the nursery role of specific marine habitats is the evidence of connectivity between juvenile and adult habitats. This paper reviews and evaluates evidence of, and spatial scales for, movements from juvenile to adult habitats and it summarises the methods used to study movements. Examples include many fish families but few invertebrate taxa, and most are species of economic importance for USA and Australia. The types of juvenile habitat range from the entire estuary or shallow open coastal waters to specific habitats within estuaries or coastal waters; in some cases juvenile habitats include habitats not traditionally regarded as nursery areas (e.g. the surf zone). The duration of time spent in juvenile habitats averages 13 mo (range 8 d to 5 yr). The majority of organisms move distances of kilometres to hundreds of kilometres from juvenile to adult habitats, although the scale of movements ranged from metres to thousands of kilometres. Changes in abundance among separate habitats and the progression of size classes among separate habitats are the main methods used to infer movement and habitat connectivity. Spatial partitioning of stages of maturity, natural parasites, and a variety of artificial tagging methods have also been used. The latter will become more useful with continued developments in the miniaturisation of artificial tags. More recent studies have used natural tags (e.g. trace elements and stable isotopes) and these methods show great promise for determining movements from juvenile to adult habitats. Few studies provide good evidence for movement from specific juvenile habitats to adult habitats. Future studies need to focus on this movement to supplement data on density, growth and survival of organisms in putative nursery habitats. Such information will allow management and conservation efforts to focus on those habitats that make the greatest contribution to adult populations.
The transition between larval and juvenile development remains ill defined for fishes that undergo indirect
development, with 0+ juveniles sometimes referred to as small adults. We examine this transition to determine whether 0+ juvenile roach, Rutilus rutilus, can be considered as small adults; we reanalysed data on the functional morphology, visual acuity, and microhabitat use of 0+ roach (1555 mm standard length (SL)) in the rivers Great Ouse (United Kingdom) and Danube (Hungary and Slovakia). Factors related to swimming ability in 0+ roach attained adult levels at 3545 mm SL, this corresponding with a temporary stabilisation in the development of visual acuity and with a significant (MannWhitney U test) microhabitat shift from protective cover in the littoral to the open channel. Contrary to current practice, which defines the start of the juvenile period in roach at 1518 mm SL, we propose the 1540 mm interval to be the final larval step, and that the juvenile period does not begin until morphological changes and structures characteristic of larval development (rapid allometric growth, remnants of finfold) have disappeared, all juvenile structures (complete scale cover, nasal septa, etc.) are present, and relative growth has stabilised.
Interdependence among disturbance events, ecosystem properties, and biological invasions often make causal relationships difficult to discern. For example, Phragmites australis invasion in mid-Atlantic salt marshes is often associated with disturbances that create well-drained features as well as with low sulfide concentrations, but explanations of these associations have been elusive. We tested experimentally: 1) that disturbances increasing wetland drainage facilitate Phragmites invasion by altering sulfide concentrations and salinity; 2) that translocation allows plants to spread beyond drainage areas; and 3) that plants can then lower edaphic stress through pressure ventilation of the rhizosphere and promote further expansion. At the invasion front, treatments of 1) severing rhizomes to halt translocation and 2) combined severing with clipping dead culms to limit ventilation of the rhizosphere killed most culms, but did not affect pore water chemistry. In already invaded areas, severing and clipping reduced culm height and panicle production, severing alone and in combination with clipping also raised sulfide and ammonium concentrations in the root zone. There were no treatment effects on plant performance or pore water chemistry along mosquito ditches, where sulfide concentrations were negligible. Small-scale hydrological alterations such as ditches appear to provide suitable sites for the establishment of Phragmites because soils are well-drained and are low in free sulfides. Subsequent expansion into more hostile areas occurs through translocation, with well-drained areas acting as sources for essential substances. Once established, the plant increases rhizosphere oxygenation and lowers sulfide concentrations.
Most tidal marsh on Delaware Bay has a history of diking for purposes of salt hay (Spartina patens) production and wildlife management. Extensive ditching for drainage and mosquito control has also altered natural hydrological
cycles, and combined with diking or other water control structures has provided suitable conditions for invasion by Phragmites australis. Where diking and other water control measures have been in place for extended periods, in some instances back to colonial
times, marsh surfaces have subsided by oxidation and compaction, and high marsh species of plants are maintained artificially
at low marsh elevations. These conditions lead to potential catastrophic “blow-outs” when dikes are rapidly breached, principally
by storms. Although seawater may enter the breaches and fill the marsh, the absence of a typical fourth order drainage system
(long filled by farming practices and sedimentation) prevents efficient return of tidal water to the adjacent bay. Massive
circulation patterns and standing water combined with the low marsh plain elevation kill extant plants and prevent recolonization
by low marsh species. The result may be destruction of the root mat and “fluidization” of the entire marsh surface—replaced
by an open water lagoon environment. It may take many decades for the marsh to begin to reestablish itself, if ever. Without
further intervention, the slowly recovering marsh is characterized by “tree-like” drainage configurations that appear to exhibit
low drainage density downstream, low overall sinuosity and higher order intertidal streams. It is in this framework that the
ecological engineering of macroscale marsh restoration and the criteria that determine its success, the “bound of expectation,”is
undertaken.
The mummichog,Fundulus heteroclitus, is one of the most abundant macrofaunal components of salt marsh ecosystems along the east coast of the United States. During
April–November 1998, we determined the habitat use and movement patterns of young-of-the-year (YOY) and adult mummichogs in
a restored marsh, formerly a salt hay farm, and an adjacent creek in order to expand our understanding of the ecology of the
species and evaluate the success of the restoration. Four major fish habitat types (large first-order natural creek, second-order
created creek, linear drainage ditch, and marsh surface) were identified within the study site. Patterns of relative abundance
and mark and recapture using coded wire tags were used to determine the habitat use, tidal movements, home range, and site
fidelity of the species within these habitat types. A total of 14,784 fish, ranging from 20–100 mm SL, were captured with
wire mesh traps and tagged, and 1,521 (10.3%) fish were recaptured. A variety of gears were used to attempt to recapture fish
across all habitat types, including wire mesh traps, push nets, and otter trawls. Based on abundance and recaptures of tagged
fish, the YOY and adults primarily used the shallow subtidal and intertidal areas of the created creek, the intertidal drainage
ditches, and the marsh surface of the restored marsh but not the larger, first-order natural creek. At low tide, large numbers
were found in the subtidal areas of the created creek; these then moved onto the marsh surface on the flooding tide. Elevation,
and thus hydroperiod, appeared to influence the microscale use of the marsh surface. We estimated the home range of adults
and large YOY (20–100 mm SL) to be 15 ha at high tide, which was much larger than previously quantified. There was strong
site fidelity to the created creek at low tide. The habitat use and movement patterns of the mummichog appeared similar to
that reported for natural marshes. Coupled with the results of other studies on the feeding, growth, and production of this
species in this restoreh, the species appeared to have responded well to the restoration.
Vegetation change in response to restriction of the normal tidal prism of six Connecticut salt marshes is documented. Tidal flow at the study sites was restricted with tide gates and associated causeways and dikes for purposes of flood protection, mosquito control, and/or salt hay farming. One study site has been under a regime of reduced tidal flow since colonial times, while the duration of restriction at the other sites ranges from less than ten years to several decades. The data indicate that with tidal restriction there is a substantial reduction in soil water salinity, lowering of the water table level, as well as a relative drop in the marsh surface elevation. These factors are considered to favor the establishment and spread ofPhragmites australis (common reed grass) and other less salt-tolerant species, with an attendant loss ofSpartina-dominated marsh. Based on detailed vegetation mapping of the study sites, a generalized scheme is presented to describe the sequence of vegetation change from typicalSpartina- toPhragmites-dominated marshes. The restoration of thesePhragmites systems is feasible following the reintroduction of tidal flow. At several sites dominated byPhragmites, tidal flow was reintroduced after two decades of continuous restriction, resulting in a marked reduction inPhragmites height and the reestablishment of typical salt marsh vegetation along creekbanks. It is suggested that large-scale restoration efforts be initiated in order that these degraded systems once again assume their roles within the salt marsh-estuarine ecosystem.
This paper compares the available North Americanliterature and data concerning several ecologicalfactors affecting Phragmites australisin inlandfreshwater, tidal fresh, and tidal brackish marshsystems. We compare aboveground productivity, plantspecies diversity, and sediment biogeochemistry; andwe summarize Phragmiteseffects on faunalpopulations in these habitats. These data suggest thatPhragmitesaboveground biomass is higher thanthat of other plant species occurring in the samemarsh system. Available data do not indicate anysignificant difference in the aboveground Phragmitesbiomass between marsh types, nor doesthere appear to be an effect of salinity on height.However, Phragmitesstem density wassignificantly lower in inland non-tidal freshwatermarshes than in tidal marshes, whether fresh orbrackish. Studies of the effects of Phragmiteson plant species richness suggest that Phragmitesdominated sites have lower diversity.Furthermore, Phragmiteseradication infreshwater sites increased plant diversity in allcases. Phragmitesdominated communities appearto have different patterns of nitrogen cyclingcompared to adjacent plant communities. Abovegroundstanding stocks of nitrogen (N) were found to behigher in Phragmitessites compared to thosewithout Phragmites. Porewater ammonium(NH4
+) did not differ among plant covertypes in the freshwater tidal wetlands, but inbrackish marshes NH4
+was much higher inSpartinaspp. than in neighboring Phragmitesstands. Faunal uses of Phragmitesdominated sites in North America were found to vary bytaxa and in some cases equaled or exceeded use ofother robust emergent plant communities. In light ofthese findings, we make recommendations for futureresearch.
One of the most important reasons stated in legislation for protecting salt marshes is their support of commercially and recreationally
important nekton (fish and crustaceans). Yet, there is a surprising level of uncertainty among scientists regarding the role
of salt marshes in supporting secondary production. The emphasis has been on “marine transient” species (in earlier literature
often referred to as “estuarine dependent”) because they have life histories that seem designed to place young-of-the-year
or juveniles in marsh habitats and because these species are often of commercial or recreational value. Salt marshes are believed
to provide: 1) trophic support resulting in high growth rates, 2) increased survivorship due to lowered mortality, and 3)
a suitable physico-chemical environment for development of young fishes. In this paper, we consider the evidence for each
of these, with an emphasis on the trophic and survivorship aspects. The seasonally warmer temperatures of estuaries and salt
marsh creeks apparently provide a metabolic advantage that supports high growth rates. The influence of marsh-derived organic
matter in estuarine food webs is apparent, and its importance to marine transient fishes is supported by dietary, behavioral,
and isotopic evidence. The major pathways by which marsh organic matter is transferred to fish are largely indirect, through
microbial and invertebrate intermediaries. Invertebrates are the primary link to fish consumers of marsh-associated production,
transforming microphytes, organic detritus, and microbial detrital heterotrophs into available biomass. Although most detrital
organic carbon entering salt marsh systems, mainly from emergent grasses, is apparently respired by heterotrophs, the support
of consumers by marsh plant detritus and microalgae can be equally important. The use of salt marsh detritus in food webs
usually occurs in close proximity to the salt marsh indicating that outwelling of salt marsh organic matter offshore is not
the dominant way that salt marshes support offshore fisheries. Salt marsh support of offshore fisheries is more probably by
direct export of juvenile fish biomass and a trophic relay involving ontogenetic and cyclic migrations of nekton species,
rather than export of organic detritus. Understanding the controls on marine transient fish mortality is probably the most
problematic and least studied aspect of their ecology. The few estimates of mortality rates of fishes in estuaries are as
high as, or higher than, mortality rates of fishes in other marine and freshwater ecosystems. However, because of faster growth
rates, fish spend less time in the small stages with the higher mortality rates. Within estuaries, mortality rates for some
species, but not all, are lower in marsh creeks compared to more open areas. The value of marshes as refuge habitat is probably
due to the interaction of temperature, turbidity, and vegetative structure in restricting the foraging of piscine predators.
Since the early 1900sPhragmites australis has been replacing other vegetation in Atlantic and gulf coast marshes at a rate of about 1% to 6% of the marsh surface per
year. Vast areas of coastal marsh are now characterized by dense monotypic stands of this species. By virtue of its ability
to build up the marsh surface,P. australis affects the landscape, hydrology, and hydroperiod of the marsh as well as drainage density, and other geomorphic features.
Smoothed microtopography results in more difficult access to the marsh by nekton, and possibly reduced exchange of organic
materials between the marsh and adjacent estuary. The pattern of replacement byP. australis results in fragmentation of existing stands ofSpartina alterniflora and other extant macrophytes, thereby altering landscape ecology and the ability of the marsh to support biodiversity and
the production of marsh fauna.
Recently, Phragmites australis (common reed) in North American wetlands has changed from a species with limited distribution to an invasive species producing
dense monospecific stands. This expansion has forced out other wetland vegetation, potentially changing the functions of these
ecosystems. Little research has focused on whether P. australis stands serve as valuable wetland habitat and foraging areas for terrestrial animals and resident marsh nekton. This study
addressed the effect of different hydrologic and geomorphic conditions among P. australis stands on abundance of resident nekton in Piermont Marsh, located on the lower Hudson River Estuary. Three P. australis-dominated sites (erosional creekbank, depositional creekbank, interior) were sampled for nekton using bottomless lift nets
during day and night spring high tides during the months of July, August, and September, 1998. Hydrology data were collected
for ten continuous days during each sampling period and included mean flooding depth, duration, and frequency for the three
sites. Species captured on the marsh surface included Fundulus heteroclitus (common mummichog), Palaemonetes pugio (dagger-blade grass shrimp), Callinectes sapidus (blue crab), and Uca minax (brackish water fiddler crab). Results indicate that nekton and macrobenthos are using all areas sampled, and measured densities
are comparable to those measured in some non-P. australis dominant wetlands elsewhere on the Hudson River. Although no strong correlation was made between nekton densities and hydrology,
definite patterns were observed in the data. The results indicated that additional variables, such as geomorphology, might
interact with hydrology to influence nekton use of the marsh surface. Although exact mechanisms controlling spatial variation
of nekton use within P. australis stands still need to be elucidated, P. australis does seem to serve as nekton habitat.
This study investigates the influence ofPhragmites australis (common reed) invasion on the habitat of the resident marsh fish,Fundulus heteroclitus (mummichog) in the Hackensack Meadowlands, New Jersey. These abundant fish play an important role in the transfer of energy
from the marsh surface to adjacent subtidal waters and thus estuarine food webs. The objectives of this 2-yr study (1999 and
2000) were to compare the distribution and abundance of the eggs, larvae, juveniles, and adults of mummichog and their invertebrate
prey inhabitingSpartina alterniflora-dominated marshes withPhragmites-dominated marshes, and to experimentally investigate the influence of marsh surface microtoprography on larval fish abundance
withinPhragmites-dominated marshes. In 2000, we verified that egg deposition does occur inPhragmites-dominated marshes. In both years, the abundance of larvae and small juveniles (4–20 mm TL) inS. alterniflora was significantly greater than inPhragmites-dominated marshes, while larger juveniles and adults (>20 mm TL) were similarly abundant in both habitat types. The overall
abundance of larvae and small juveniles was significantly greater in experimentalPhragmites plots in which microtopography was manipulated to resemble that ofSpartina marshes than inPhragmites control plots. Major groups of invertebrate taxa differed between marsh types with potential prey for larval fish being significantly
more abundant inS. alterniflora marshes.Phragmites-dominated marshes may not provide the most suitable habitat for the early life-history stages of the mummichog. The low abundance
of larvae and small juveniles inPhragmites marshes is likely due to inadequate larval habitat and perhaps decreased prey availability for these early life history stages.
The responses of tidal marsh macroinvertebrate assemblages to the conversion of Spartina alterniflora marshes to marshes dominated by the invasive reed, Phragmites australis, are poorly understood Changes in edaphic, vegetative, hydrologic, and detrital conditions that attend conversion to Phragmites should produce changes in the intertidal fauna. We used core sampling (7.8-cm diameter, 4-cm deep) and litter packs to compare
the intertidal macroinvertebrate fauna of Phragmites marshes and adjacent remnant Spartina marshes in a brackish reach of the Mullica River (0–17 ppt salinity during the study) in southern New Jersey, USA. Detrital
and above-ground vegetative biomass and water velocity were greater in Phragmites marsh; stem density, microtopographic relief, and the density of standing-water microhabitats were greater in Spartina marsh. The intertidal assemblages varied between marsh types. Total macroinvertebrate density was greater in Spartina marsh (97,000 m−2) than in Phragmites marsh (82,000 m−2). Mean taxa richness (number of taxa per core sample) was greater in Spartina marsh (12.4 taxa sample−1) than in Phragmites marsh (9.4 taxa sample−1) and dominance (relative abundance of the three most abundant taxa) was lower. Oligochaeta, Nematoda, and the polychaete,
Manayunkia aestuarina, dominanted the fauna (>75% of the total abundance) in both marsh types. Of these, oligochaetes were more abundant in Spartina marsh, and nematodes and polychaetes were slightly more abundant in Phragmites marsh. Most common subdominant taxa (100-4,000 m−2), including ceratopogonids, chironomids, mites, ostracods, isopods, and gastropods were more abundant in Spartina marsh. Collembolans were more abundant in Phragmites marsh; amphipods were about equally abundant in both marsh types. Invertebrate abundance and assemblage composition varied
with distance from the edge of the marsh in both marsh types; overlap in assemblage composition between marsh types was greates
at the edge of the marsh, where more frequent inundation may have moderated the influence of vegetation type on the marsh
fauna. For mean taxa richness and for the density of most taxa, the effect of marsh type on density exceeded the effect of
season, marsh position, or a local salinity gradient. We consider the greater density of intertidal standing-water microhabitats
and probably of microalgal production as important sources of faunal variation between marsh types. Fewer refugia from predators
during high tide in Phragmites marsh may also contribute to variation in faunal abundance and community structure between marsh types. Detritus biomass
was probably a more important source of spatial variation in the fauna of the Phragmites marsh than in Spartina marsh.
The mummichog,Fundulus heteroclitus, is one of the most important macrofaunal components of salt marsh surfaces and an important link to subtidal areas of the
adjacent estuary along the east coast of the U.S. We estimated growth, population size, and production of the mummichog in
a restored marsh in order to improve our understanding of the role of this resident fish and to evaluate the success of the
restoration. The restored marsh, covering 234 ha, was a former salt hay farm located in the mesohaline portion of Delaware
Bay that was restored to tidal influence in August 1996. We separated the mummichog population into two components based on
life history stage and summer habitat use patterns. One component, consisting of adults and large young-of-the-year (YOY),
exhibited tidal movements to and from the marsh surface and the subtidal creeks. These were examined with an intensive mark
and recapture program using coded wire tags. Another component, consisting of small YOY, remained on the marsh surface throughout
the tidal cycle. Throw traps were used to sample these small YOY. The mean annual population density of adults and large YOY
for the entire marsh was approximately 1.2 fish m−2 and mean monthly density peaked at 2.9 fish m−2. The mean annual density of small YOY on the marsh surface was 15.1 fish m−2 and mean monthly density peaked at 41.4 fish m−2. Size and season influenced the growth rate of individual fish and instantaneous growth rates ranged from 0.03 to 2.26 mo−1. Total annual mummichog production was estimated to be 8.37 g dw m−2 yr−1, with adults and large YOY contributing 28.4% (2.38 g dw m−2 yr−1) and small YOY on the marsh surface contributing 71.6% (5.99 g dw m−2 yr−1). The seasonal use and population densities were comparable to previous studies in natural marshes while growth and production
of mummichog in this restored marsh appeared to be higher. Coupled with the results of other studies on the feeding, movement,
and habitat use of this species in this restored marsh, the species has responded well to the restoration.
We began in Chapter 1 with an introduction to the salt marsh as an ecological system and progressively dissected that system into component parts and processes, examining interactions, impacts, and controls. We started to put the parts together again when discussing the carbon-flow model. We complete the process of unification in this final chapter, concentrating in particular on the mechanisms by which salt marshes are connected to the larger systems abutting and affecting them—the land and its rivers on the one side, and the sea on the other.
Every individual of a population is challenged daily by circumstances that demand certain levels of performance if the organism is to survive long enough to contribute to recruitment, no matter how recruitment is defined. The challenges faced by fish larvae are especially arduous and numerous because of their relatively small size, which limits their abilities to thwart predators, starvation, and transport to detrimental environs (Miller et al., 1988; Fuiman and Magurran, 1994). Performance — behavioural, physiological or otherwise — is the key to survival and, hence, recruitment. It can be measured for any of a multitude of processes that operate from the subcellular through whole-organism levels. Natural selection acts on the entire phenotype — morphology, physiology and behaviour — to shape the performance capacities of individuals. Detailed knowledge of these performance capacities and the magnitude of their variation is essential for a full understanding of the mechanisms that ultimately determine recruitment.
The NOAA program on National Estuarine Research Reserves (NERR) has developed to encompass 21 locations, each dedicated to the development and operation of an estuarine area as a natural field laboratory. Education and research are the primary goals of the Program. The Mullica River - Great Bay estuarine system in southern New Jersey is proposed to be added to the national program. It is large, encompassing a total of 46,172 hectares.
Spawning in a natural population of the mummichog, Fundulus heteroclitus, occurs cyclically throughout its reproductive season. Gonadal maturity and spawning readiness of males and females are greatest for several days coincident with new or full moon. The spawning rhythm is apparent in size distributions of fry collected during the spawning season. A diurnal cycle in both spawning readiness and gonadal maturity was super-imposed on the lunar spawning rhythm. Although mature eggs were found in the ovaries of fish examined during the day at spawning peaks, these eggs were usually dispersed throughout the stroma of the ovary. Fish sampled at the night high tide usually contained ovulated eggs grouped posteriorly in the lumen of the ovary, at the opening of the ovipositor. This rhythmicity synchronizes spawning with the highest tides of the lunar cycle, and makes possible the deposition of eggs in locations which insure their incubation away from strong tidal currents. The observed spawning rhythm is an important component of a reproductive sequence that appears to be of adaptive significance in the tide marsh environment.
Reed grass (Phragmites australis (Cav.) Trin. ex Steud.) has invaded large areas of tidal marsh along the lower Connecticut River and often occurs as a monoculture. Tidal marsh invertebrates (snails, amphipods and isopods) were common to abundant in reed grass-dominated regions, as well as in areas covered by typical tidal marsh vegetation at four sampling stations set up along the salinity gradient. This finding suggests that reed grass marshes provide suitable physical habitat and usable food resources for these semiaquatic detritus/algae feeders. Mummichogs (Fundulus heteroclitus L.) were caught on the high marsh during daylight high tides using Breder traps and an analysis of their gut contents was made. When daylight tides were high enough to cover the marsh surface, mummichogs moved up onto the marsh and fed extensively on marsh invertebrates, both in reed grass marshes and reed grass-free marshes. Such foraging appears to represent a direct trophic link between the marshes and adjacent estuarine waters. Even when tides were not high enough to flood the marsh surface, mummichogs moved into the tidal creeks that course through reed grass marshes and largely reed grass-free marshes and foraged there. With respect to macroinvertebrate populations and mummichog foraging, the reed grass marshes appear to be functioning in essentially the same ways as nearby marshes not invaded by this plant, at least in the short term.
The current perception of estuarine nekton assemblages has been shaped by an emphasis on transient marine fishes, a focus on commercially harvested species, and a tendency to diminish or dismiss the role of permanent resident nekton in the functioning of estuarine ecosystems. Tidal marshes are among the most productive environments on Earth, but the importance of marsh production in the trophic support of adjacent estuarine and coastal ocean ecosystems has been debated for decades. The largest areal component, and defining feature of tidal marshes, is the vegetated intertidal zone. Estuarine nekton assemblages are considered from this intertidal perspective, with the intent of highlighting the potential importance of resident species in the transfer of intertidal production to the estuary. Quantitative methods for sampling in the shallow waters of this highly structured and dynamic environment have been developing, and may provide new insights into this issue. Although few marine and freshwater transients have direct access to intertidal production, almost all life-history stages of resident nekton have an intimate and very direct association with the intertidal marsh. Information on habitat use, feeding habits, life histories and movements is related to spatial features of the marsh landscape to illustrate a hypothetical 'trophic relay'. This conceptual model shows how different groups of resident and transient nekton may interact to move intertidal production horizontally across landscape boundaries and into the subtidal estuary.
Productivity of a Delaware, U.S.A., tidal creek population of adult Fundulus heteroclitus (Linnaeus) was estimated during the summers of 1972 and 1973. Population size, length-frequency distribution, length-weight relationship, standing crop, instantaneous growth coefficients by length and weight, and mortality rate were determined. Petersen and Jolly stochastic indices were used to estimate population sizes along several 36 m segments of creek bank, the 36 m unit being a boundary limit for summer home range in our study area for most individual fish. Production was computed using an exponential model of growth rate and a linear model of mean stock biomass. Population parameters for young-of-the-year fish were derived by estimating the recruitment necessary to reconstitute the adult population between the end of our first and the start of our second summer study periods. These data are partially summarized in a model of changes in age and size class structure over an annual cycle.Mortality rate for age group O (from eggs to 59 mm T.L.) was estimated to be at least 99·5%, while mortality rate in age group I and older (⩾60 mm T.L.) was estimated to be from 51 to 57% per year. Productivity was a minimum of 40·7 gm−2 year−1, this being one of the highest reported values for fish productivity. Young-of-the-year fish produce at least 78% of the annual production. The high productivity of this resident fish population indicates that F. heteroclitus makes an important contribution to the energy transfers within tidal marshes.
Throughout the eastern USA many Spartina alterniflora salt-marsh systems are being altered through the invasion of Phragmites australis. As a result, substantial declines in the areal distribution of S. alterniflora-dominated habitat have occurred in contrast to increases in P. australis dominated habitat. While information is scarce on nekton use of P. australis marsh, increases in the areal distribution of this species have concerned resource managers. Managers typically view the shift of S. alterniflora to P. australis marsh as a shift from a biologically diverse and productive marsh to one less biologically diverse and productive. We examined nekton use of P. australis marsh relative to S. alterniflora marsh with similar geographic location and physical conditions. We found no significant differences (p > 0.05) in the utilization of P. australis and S. alterniflora marsh by nekton in terms of abundance or biomass. Further, no significant difference (p > 0.05) in the total number of nekton species was evident between P. australis and S. alterniflora marsh. We postulate that under similar environmental and physical conditions these marsh types are equivalent in terms of nekton use. It may be necessary to reevaluate current wetland management practices which involve the elimination of P. australis in favor of S. alterniflora marsh in order to increase nekton use.
Species composition, numbers and biornass of the nekton comn~unity on a regularly-flooded Spartina marsh near Beaufort, North Carolina, USA, was estimated for 1 yr using modified 10 m block nets. Thirty-five fish species dominated by mummichog Fundulus heteroclitus, spot Leiostomus xanthurus and pinfish Lagodon rhornboides were captured from the marsh surface. Numbers were greatest in April (1300 per 10 m of marsh edge); biomass was greatest in September (900 g per 10 m). Stream Order 1 (rivulet) marsh was occupied by fewer species, but contained greater numbers and biomass than Stream Order 3 (channel) marsh.
The recent expansion of the reed Phragmites australis in western Atlantic salt marshes has become a conservation concern. Historically, Phragmites was restricted to the terrestrial border of marshes, but now it aggressively invades lower elevations. To explore factors influencing this expansion, we examined (1) the effects of physical factors and competitive interactions on the performance of Phragmites and (2) the role of clonal integration on the ability of Phragmites to invade low marsh habitats. We transplanted Phragmites into vegetation along an elevation gradient, with and without neighboring plants. Phragmites died when transplanted to the lowest marsh zone but survived and expanded in higher marsh zones. This suggests that the low oxygen availability characteristic of waterlogged soils limits Phragmites growth in the low marsh. Neighboring vegetation reduced Phragmites growth in all zones, and severing Phragmites rhizomes invading the low marsh reduced the survivorship and photosynthetic rate of ramets. These results suggest that Phragmites may invade low marsh habitats by initially establishing itself in the high marsh and then expanding into lower, less favorable habitats using clonal integration. This has important implications for understanding the changing dynamics of New England salt marsh plant communities and developing management strategies for the control of Phragmites.
Fundulus heteroclitus (L.) from a North Carolina Spartina marsh teed largely on small crustaceans (amphipods, tanaids and copepods) and polychaetes. Fish longer than 30 mm standard length also ingested considerable amounts of living plant material. Smaller individuals were distinctly carnivorous. Recognizable particles of Spartina detritus occurred in less than 15% of the guts examined. The relationship of weight to length changed significantly during the year. Although females were larger than males of the same age. males were heavier than females of the same length, except for a brief period at the peak of the spawning season in the early spring. An average second season fish may lay up to 512 eggs from March through August, but first season fish did not reach reproductive size by the end of the spawning season. Growth of first season fish in mid-summer averaged 5% of their total weight per day. These significant seasonal changes in ecological properties of killifish populations are important in any estimates of growth, reproduction, and production.