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1.
The effects of bioturbation by the mud fiddler crab (Uca pugnax) on salt marsh seedling recruitment were investigated experimentally in this study. Burrowing and foraging activity caused
a large amount of soil disturbance, which in turn negatively impacted the establishment of seedlings. Either seeds did not
germinate or seedlings were uprooted or buried. Although the majority of the published literature suggests a positive influence
of Uca spp. on salt marsh plant growth, at high densities they have the potential to hinder the re-colonization of areas made bare
by previous disturbance. This study illustrates the perhaps underappreciated role that bioturbators can have on vegetation
patterns in salt marshes and other ecosystems. 相似文献
2.
In mid-Atlantic salt marshes, reproductively active male sand fiddler crabs, Uca pugilator, use a single greatly enlarged major claw as both a weapon to defend specialized breeding burrows from other males and an ornament to attract females for mating. During the summer breeding season, females strongly prefer to mate with males controlling burrows in open areas high on the shore. Food availability decreases while temperature and desiccation stress increase with increasing shore height, suggesting that the timing and location of fiddler crab mating activity may result in a potential trade-off between reproductive success and physiological condition for male crabs. We compared thermal preferences in laboratory choice experiments to body temperatures of models and living crabs in the field and found that from the perspective of a fiddler crab, the thermal environment of the mating area is quite harsh relative to other marsh microhabitats. High temperatures significantly constrained fiddler crab activity on the marsh surface, a disadvantage heightened by strongly reduced food availability in the breeding area. Nevertheless, when the chance of successfully acquiring a mate was high, males accepted a higher body temperature (and concomitantly higher metabolic and water loss rates) than when the chances of mating were low. Likewise, experimentally lowering costs by adding food and reducing thermal stress in situ increased fiddler crab waving display levels significantly. Our data suggest that fiddler crabs can mitigate potential life history trade-offs by tuning their behavior in response to the magnitude of both energetic and non-energetic costs and benefits. 相似文献
3.
Irwin A. Ungar 《The Botanical review》1998,64(2):176-199
The influence of biotic factors on the distribution and establishment of halophytes is being considered in this review. Physicochemical
factors, such as salinity and flooding, often are considered to be the determining factors controlling the establishment and
zonational patterns of species in salt marsh and salt desert environments. Sharp boundaries commonly are found between halophyte
communities even though there is a gradual change in the physicochemical environment, which indicates that biotic interactions
may play a significant role in deterining the distribution pattern of species and the composition of zonal communities. Competition
is hypothesized to play a key role in determining both the upper and lower limits of species distribution along a salinity
gradient. Field and laboratory experiments indicate that the upper limits of distribution of halophytes into less saline or
nonsaline habitats is often determined by competition. There appears to be a reciprocal relationship between the level of
salt tolerance of species and their ability to compete with glycophytes in less saline habitats. Halophytes are not competitive
in nonsaline habitats, but their competitive ability increases sharply in saline habitats. Allelopathic effects have been
reported in salt desert habitats, but have not been reported along salinity gradients in salt marshes. Some species of halophytes
that are salt accumulators have the ability to change soil chemistry. Chemical inhibition of intolerant species occurs when
high concentrations of sodium are concentrated in the surface soils of salt desert plant communities that are dominated by
salt-accumulating species. Establishment of less salt-tolerant species is inhibited in the vicinity of these salt-accumulating
species. Herbivory is reported to cause both an increase and a decrease in plant diversity in salt marsh habitats. Heavy grazing
is reported to eliminate sensitive species and produce a dense cover of graminoids in high marsh coastal habitats. However,
in other marshes, grazing produced bare patches that allowed annuals and other low marsh species to invade upper marsh zonal
communities. A retrogression in plant succession may occur in salt marshes and salt deserts because of heavy grazing. Intermediate
levels of grazing by sheep, cattle, and horses could produce communities with the highest species richness and heterogeneity.
Grazing by geese produced bare areas that had soils with higher salinity and lower soil moisture than vegetated areas, allowing
only the more salt-tolerant species to persist. Removal of geese from areas by use of inclosures caused an increase in species
richness in subarctic salt marshes. Invertebrate herbivores could also inhibit the survival of seeds and the ability of plants
to establish in marshes. Parasites could play a significant role in determining the species composition of zonal communities,
because uninfected rarer species are able to establish in the gaps produced by the death of parasitized species. 相似文献
4.
A notable omission from wetlands ecology has been the study of the influence of herbivores on vegetation. Reported here are the effects of grazing by snow geese Anser caerulescens altantica on the vegetation of salt marshes along the mid-Atlantic coast of the United States, Exclosures were used to compare total and species percent cover between grazed and ungrazed areas in three marshes (Salt Flats, South Pond, and Bodie Island) with differing vegetation communities from 1978 to 1980.
Spartina alterniflora was reduced by ⅔ in grazed versus ungrazed areas of Salt Flats, S. S. patens was reduced by ½ in grazed portions of South Pond but recovered when grazing ceased. In grazed portions of Bodie Island total plant cover was reduced by 16%. Scirpus robustus and S. patens reacted in opposite ways to grazing pressure with S. robustus increasing and S. patens decreasing, Elocharis was found only in grazed areas of Bodie Island. Echinochloa crusgali appeared in grazed portions of this marsh in 1978 but decreased in abundance during subsequent years. Scirpus americanus was unaffected by grazing, maintaining a nearly constant percent cover in grazed and ungrazed areas at Bodie Island.
Differences in responses to grazing are discussed in terms of each species' growth and reproductive strategies as tempered by the physical and biological environment within each marsh. 相似文献
Spartina alterniflora was reduced by ⅔ in grazed versus ungrazed areas of Salt Flats, S. S. patens was reduced by ½ in grazed portions of South Pond but recovered when grazing ceased. In grazed portions of Bodie Island total plant cover was reduced by 16%. Scirpus robustus and S. patens reacted in opposite ways to grazing pressure with S. robustus increasing and S. patens decreasing, Elocharis was found only in grazed areas of Bodie Island. Echinochloa crusgali appeared in grazed portions of this marsh in 1978 but decreased in abundance during subsequent years. Scirpus americanus was unaffected by grazing, maintaining a nearly constant percent cover in grazed and ungrazed areas at Bodie Island.
Differences in responses to grazing are discussed in terms of each species' growth and reproductive strategies as tempered by the physical and biological environment within each marsh. 相似文献
5.
W. Christopher Long Russell P. Burke 《Journal of experimental marine biology and ecology》2007,353(1):80-88
Anthropogenic habitat fragmentation is increasingly problematic in both terrestrial and aquatic systems. Fragmentation reduces the size of habitat patches, so examining the effect of patch size on community structure can provide insight into the potential effects of fragmentation. In this study, we examined the effect of habitat size on the density of Spartina alterniflora shoots in tidal saltwater marshes, as well as on the two predominant macrofaunal species, the marsh periwinkle Littoraria irrorata and fiddler crabs Uca spp. We estimated the density of shoots in three different marsh habitats, (1) large island marshes, (2) small island marshes, and (3) large fringing marshes, in Indian Field Creek, York River, Chesapeake Bay. We manipulated shoot density in each of the marsh types to distinguish between the effects of marsh grass density and marsh type on crab and Littoraria densities in the system. We found significant differences in grass density among the three marsh types as well as significant species-specific effects of grass density, marsh type, and distance from edge on faunal abundance. Decreasing the shoot density resulted in a decrease in Littoraria density in the large marshes. Littoraria density increased with distance from edge in the small marshes and in the first 5 m of the fringing marshes, then decreased with distance from edge after 5 m in the fringing marshes. Shoot density had a negative effect on crabs in both the large and small marshes. These results suggest that fragmentation would have a negative effect on the community structure by lowering the densities of both the flora and fauna. 相似文献
6.
Fiddler crabs (Uca spp.) are common inhabitants of temperate and tropical coastal communities throughout the world, often occupying specific microenvironments within mangrove and salt marsh habitats. As second intermediate hosts for trematodes, we investigated patterns of host distribution and parasitism for 3 species of sympatric fiddler crabs in mangrove habitats adjacent to the Indian River Lagoon, Florida. Fiddler crab distribution varied among species, with Uca speciosa dominating the low and mid intertidal regions of mangrove banks. This species also exhibited higher prevalence and abundance of Probolocoryphe lanceolata metacercariae compared with Uca rapax, which is relatively more abundant in the high intertidal zone. We conducted a field experiment to test whether U. speciosa was more heavily parasitized by P. lanceolata as a result of its habitat distribution by raising U. speciosa and U. rapax under identical environmental conditions. After exposure to shedding cercariae under the same field conditions, all individuals of U. speciosa became parasitized by P. lanceolata, whereas no U. rapax were parasitized, suggesting that differences in parasitism were driven by host selection. 相似文献
7.
Sergey V. Budaev 《Environmental Biology of Fishes》1997,49(1):71-78
Underwater field observations in a non-reproductive period revealed enormous variation in schooling tendencies among individual european wrasses, Symphodus ocellatus. The fish occupying vegetated habitats displayed much more pronounced schooling tendencies than those from open areas. Sixteen solitary and schooling males were caught with a small seine and observed in a novel environment. The former individuals turned out to be much more bold and active than the latter in this test, which would suggest lower fear and higher exploratory tendency. It was hypothesized that the bolder wrasses might appear as territorial nest-builders in the reproductive period, whereas the shyer ones are likely to play sneaky and satellite tactics. 相似文献
8.
Ramona O. Swenson 《Environmental Biology of Fishes》1999,55(1-2):99-114
Understanding the ecology and behavior of endangered species, such as the tidewater goby, Eucyclogobius newberryi, is important for identifying problems and formulating solutions for species recovery. The tidewater goby forms isolated populations in California's coastal lagoons, creeks, and marshes. Rapid declines in the number of populations led to its listing as an endangered species in 1994. This benthic fish prefers stillwater habitats and feeds on small invertebrates. It is an annual species with an extended breeding season. Fish are larger in marsh habitats than in lagoon or creek habitats. The male digs a spawning burrow, preferably in sand, where he provides care for a single clutch. The tidewater goby is sex-role reversed: females compete more intensely than males for access to mates. The tidewater goby is a species at risk, in part due to narrow habitat preferences, isolation of populations, short lifespan, lack of marine dispersal, and vulnerability to introduced predatory fishes. Attributes that favor its recovery include euryhaline tolerances, rapid reproductive rate, its potential for opportunistic feeding, and the possibility of natural recolonization under certain circumstances. Potential conservation measures include protecting coastal marshes that adjoin creeks and lagoons, maintaining natural hydrologic regimes, preventing artificial breaching of the sandbar at the estuary's mouth, and preventing introductions of predatory fishes. Captive breeding and reintroduction of tidewater gobies are potential tools for recovery, provided that underlying problems of habitat availability and suitability and issues of genetic integrity and disease transmission are addressed. Further research into the tidewater goby's utilization of marsh habitats, dispersal mechanisms, response to artificial breaching events, and metapopulation genetics would provide additional information for management. 相似文献
9.
R. Scott Warren Paul E. Fell Ron Rozsa A. Hunter Brawley Amanda C. Orsted Eric T. Olson Varun Swamy William A. Niering 《Restoration Ecology》2002,10(3):497-513
In 1980 the State of Connecticut began a tidal marsh restoration program targeting systems degraded by tidal restrictions and impoundments. Such marshes become dominated by common reed grass (Phragmites australis) and cattail (Typha angustifolia and T. latifolia), with little ecological connection to Long Island Sound. The management and scientific hypothesis was that returning tidal action, reconnecting marshes to Long Island Sound, would set these systems on a recovery trajectory. Specific restoration targets (i.e., pre‐disturbance conditions or particular reference marshes) were considered unrealistic. However, it was expected that with time restored tides would return ecological functions and attributes characteristic of fully functioning tidal salt marshes. Here we report results of this program at nine separate sites within six marsh systems along 110 km of Long Island Sound shoreline, with restoration times of 5 to 21 years. Biotic parameters assessed include vegetation, macroinvertebrates, and use by fish and birds. Abiotic factors studied were soil salinity, elevation and tidal flooding, and soil water table depth. Sites fell into two categories of vegetation recovery: slow, ca. 0.5%, or fast, more than 5% of total area per year. Although total cover and frequency of salt marsh angiosperms was positively related to soil salinity, and reed grass stand parameters negatively so, fast versus slow recovery rates could not be attributed to salinity. Instead, rates appear to reflect differences in tidal flooding. Rapid recovery was characterized by lower elevations, greater hydroperiods, and higher soil water tables. Recovery of other biotic attributes and functions does not necessarily parallel those for vegetation. At the longest studied system (rapid vegetation recovery) the high marsh snail Melampus bidentatus took two decades to reach densities comparable with a nearby reference marsh, whereas the amphipod Orchestia grillus was well established on a slow‐recovery marsh, reed grass dominated after 9 years. Typical fish species assemblages were found in restoration site creeks and ditches within 5 years. Gut contents of fish in ditches and on the high marsh suggest that use of restored marsh as foraging areas may require up to 15 years to reach equivalence with reference sites. Bird species that specialize in salt marshes require appropriate vegetation; on the oldest restoration site, breeding populations comparable with reference marshland had become established after 15 years. Use of restoration sites by birds considered marsh generalists was initially high and was still nearly twice that of reference areas even after 20 years. Herons, egrets, and migratory shorebirds used restoration areas extensively. These results support our prediction that returning tides will set degraded marshes on trajectories that can bring essentially full restoration of ecological functions. This can occur within two decades, although reduced tidal action can delay restoration of some functions. With this success, Connecticut's Department of Environmental Protection established a dedicated Wetland Restoration Unit. As of 1999 tides have been restored at 57 separate sites along the Connecticut coast. 相似文献
10.
Oliver-D. Finch Heinrich Krummen Friedhelm Plaisier Walter Schultz 《Wetlands Ecology and Management》2007,15(3):207-228
The specific communities of spiders and carabid beetles of island salt marsh habitats of the East Frisian Island chain at
the German North Sea coast were investigated. During the vegetation periods of 1997 and 1998 three pitfall trapping transects
were installed on the islands of Borkum and Wangerooge. Within the salt marshes, transects extended from 0 m to 175 m. Elevation
gradients varied between 10 cm and 232 cm above MHT (mean high tide). On Borkum, 35 traps were exposed in two transects, on
Wangerooge 25 traps were placed in one transect. Three to five elevations above MHT were investigated per transect, each one
with five traps. Highest species numbers were recorded in the higher elevated salt marshes. In contrast, highest activity
values were noticed in the medium elevated salt marshes. Within both groups, spiders and carabids, four communities were distinguished
by indirect gradient analysis. Indicator species were assigned to the different communities that were mainly assorted to different
elevations of the salt marshes. Thus, the communities of both taxa corresponded well to the vegetational formations. The importance
of sea level rise for structuring the communities of salt marsh arthropods is discussed. Overall, still great uncertainties
exist on how arthropod communities and salt marshes themselves will develop. 相似文献
11.
Spatial variability in the response of lower trophic levels after carp exclusion from a freshwater marsh 总被引:3,自引:0,他引:3
Vanessa L. Lougheed Patricia Chow-Fraser 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》2001,9(1):21-34
Large common carp (Cyprinus carpio >30 cm) wereexcluded from a turbid, eutrophic coastal marsh of Lake Ontario with theconstruction of a fishway at the outlet. The marsh was sampledintensively for 2 seasons prior to (1993, 1994) and following (1997,1998) carp exclusion to study changes in water quality and shifts incommunity structure of phytoplankton and zooplankton. Samples werecollected from May to September in three habitats: open water, vegetated(cattail beds) and sewage lagoon. In the first year after carpexclusion, mean seasonal water turbidity decreased at all sites by49–80%; this was accompanied by growth of submergentplants in shallow, sheltered areas including the vicinity of cattails atthe vegetated site. This drop in turbidity was not significant in thesecond year after exclusion at the open water and lagoon sites, withturbidity levels declining by only 26–54% of1993–1994 values; only the vegetated site showed a sustaineddecrease in turbidity and persistent growth of submergent plants. At thevegetated site, increased clarity was concurrent with a significantreduction in edible algal biomass and an increased representation oflarge zooplankton grazers and substrate-associated cladocerans. At theopen water site, a spring clear-water phase was evident during the firstyear of exclusion and this coincided with the unusual appearance of alarge population of Daphnia. Compared to the other sites, thelagoon remained relatively turbid throughout the study. Results of thisstudy indicate that the response of lower trophic levels tobiomanipulation was variable from site-to-site and contributed to theco-existence of two alternative states in the marsh. In vegetated areas,water clarity was maintained by a positive feedback system betweenzooplankton and submergent macrophytes in the first 2 years followingexclusion. We suggest that both benthivore removal (to reducebioturbation) and planktivore reductions (to produce top down effects)were required to produce clear water and allow submersed macrophytegrowth. Although carp removal likely contributed to a 45%reduction in turbidity, an unusual climactic event in 1997, resulting indelayed fish spawning in the marsh, temporarily reduced zooplanktivoryand favoured zooplankton grazing-induced water clarity improvements. 相似文献
12.
MEGAN BAILEY SCOTT A. PETRIE SHANNON S. BADZINSKI 《The Journal of wildlife management》2008,72(3):726-732
Abstract: During the past 30 years, nonnative mute swan (Cygnus olor) populations have greatly increased, and continue to increase, in the eastern United States and within the lower Great Lakes (LGL) region. As a result, there is much concern regarding impacts of mute swan on native waterfowl, aquatic plants, and marsh habitats. There are presently only limited dietary data for mute swans in North America and none exist for birds in the LGL region. Thus, in 2001, 2002, and 2004 we collected 132 mute swans from LGL coastal marshes in Ontario, Canada, to determine dietary composition and to evaluate 1) seasonal and sex-related variation in adult diets and 2) age-related dietary differences. Adult diets did not differ among years, collection sites, or seasons, but female diets contained more pondweed spp. (Potamogeton spp.) and less slender naiad (Najas flexilis) and common waterweed (Elodea canadensis) than did diets of males. Adult males, adult females, and cygnets had similar diets during summer and autumn. Overall, mute swan diets mainly consisted of above-ground biomass of pondweed spp., muskgrass (Chara vulgaris), coontail (Ceratophyllum demersum), slender naiad, common waterweed, wild celery (Vallisneria americana), and wild rice (Zizania palustris); below-ground parts of wild celery, sago pondweed (Stuckenia pectinatus), and arrowhead spp. (Sagittaria spp.) were eaten infrequently. Comparison of our findings with those of other diet studies suggested considerable dietary overlap between mute swans and several other species of native waterfowl. Thus, we suggest that mute swans have potential to compete with native waterfowl and impact aquatic plants that are important waterfowl foods within LGL coastal marshes. Further, our results can be used to assess which aquatic plant species may be most impacted by foraging activities of mute swans at other important waterfowl stopover and wintering sites in North America. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):726–732; 2008) 相似文献
13.
Climate change and loss of saltmarshes: consequences for birds 总被引:3,自引:0,他引:3
R. G. Hughes 《Ibis》2004,146(S1):21-28
Saltmarshes are areas of vegetation subject to tidal inundation and are important to birds for several reasons. Saltmarshes are areas of high primary productivity and their greatest significance for coastal birds is probably as the base of estuarine food webs, because saltmarshes export considerable amounts of organic carbon to adjacent habitats, particularly to the invertebrates of mudflats. In addition, saltmarshes are of direct importance to birds by providing sites for feeding, nesting and roosting. Climate change can affect saltmarshes in a number of ways, including through sea-level rise. When sea-level rises the marsh vegetation moves upward and inland but sea walls that prevent this are said to lead to coastal squeeze and loss of marsh area. However, evidence from southeast England, and elsewhere, indicates that sea-level rise does not necessarily lead to loss of marsh area because marshes accrete vertically and maintain their elevation with respect to sea-level where the supply of sediment is sufficient. Organogenic marshes and those in areas where sediment may be more limiting (e.g. some west coast areas) may be more susceptible to coastal squeeze, as may other marshes, if some extreme predictions of accelerated rates of sea-level rise are realized. 相似文献
14.
The salt marshes of the Wadden Sea are important wintering areas for some species of granivorous passerines, which have declined considerably since the 1960s. We investigated the habitat choice of all wintering passerines in eight study areas in German salt marshes with special consideration of human impact on these habitats. Granivorous species that almost exclusively winter in salt marshes, Shorelark (Eremophila alpestris), Snow Bunting (Plectrophenax nivalis) and Twite (Carduelis flavirostris) were concentrated in the lower salt marsh vegetation and in the driftlines, while all other species preferred the high upper salt marsh communities, although Rock Pipits (Anthus petrosus littoralis) fed in muddy areas along ditches. Shorelarks switched habitat in conditions where seeds were scarce to feed instead on arthropods in upper salt marshes. Intensively sheep-grazed upper salt marshes resemble lower salt marshes in their vegetation and were therefore mainly visited by Shorelarks, Snow Buntings and Twites. In winter, the driftline is preferred by the two former species, while in autumn and spring more birds foraged in the salt marshes. Twites prefer to feed mainly on seeds of Salicornia. Areas with S. europaea are visited mainly in late autumn and early winter, while areas with S. stricta are used throughout the winter because of a steady supply of seeds. Several years after embankment, polders are hardly used any more by the lower salt marsh species as the habitat changes into freshwater marshes. Large embankment projects since the early 1960s have included salt marshes and intertidal flats, and the resultant loss of habitat is responsible for the decline of lower salt marsh species. For other passerine species the effects of reclamation are unknown. The effects of intensified grazing on the wintering populations of Shorelark, Snow Bunting and Twite are still unresolved. Although grazing supports lower salt marsh vegetation, the seed production per plant is much lower there and some important seed producers hardly occur. Since grazing was reduced and embankment projects have been stopped, the salt marsh areas (especially lower salt marshes) have increased and so have the wintering populations of Shorelark, Snow Bunting and Twite. For the other species, the consequences of habitat changes are unknown, although it is suggested that reduced grazing will support them. Reducing the human impact on salt marshes will, in the long run, probably lead to a natural salt marsh with much variety in elevation and in its corresponding vegetation and bird communities. Meanwhile, management by grazing might be required in parts of the salt marshes. 相似文献
15.
K. W. Able T. M. Grothues S. M. Hagan M. E. Kimball D. M. Nemerson G. L. Taghon 《Reviews in Fish Biology and Fisheries》2008,18(1):65-97
This synthesis brings together published and unpublished data in an evaluation of restoration of former salt hay farms to
functioning salt marshes. We compared nine years of field measurements between three restored marshes (Dennis, Commercial,
and Maurice River Townships) and a reference marsh (Moores Beach) in the mesohaline portion of Delaware Bay. In the process,
we compared channel morphology, geomorphology, vegetation, sediment organic matter, fish assemblages, blue crabs, horseshoe
crabs, benthic infauna, and diamondback terrapins. For fishes we compared structural (distribution, abundance) and functional
(feeding, growth, survival, reproduction, production) aspects to evaluate the restored marshes in an Essential Fish Habitat
context. Marsh vegetation and drainage density responded gradually and positively with restored marshes approximating the
state of the reference marsh within the nine-year study period. The fauna responded more quickly and dramatically with most
measures equal or greater in the restored marshes within the first one or two years after restoration. Differences in response
time between the vegetation and the fauna imply that the faunal response was more dependent on access to the shallow intertidal
marsh surface and intertidal and subtidal creeks than on characteristics of the vegetated marsh. The fishes in created subtidal
creeks in restored marshes responded immediately and maintained fish assemblages similar to the reference marsh over the study
period. The intertidal creek fish assemblages tended to become more like the reference marsh in the last years of the comparison.
Overall, these results document the success of the restoration and how marshes function for both resident and transient fauna,
especially fishes. 相似文献
16.
D. M. Burdick M. Dionne R. M. Boumans F. T. Short 《Wetlands Ecology and Management》1997,4(2):129-144
Efforts are underway to restore tidal flow in New England salt marshes that were negatively impacted by tidal restrictions. We evaluated a planned tidal restoration at Mill Brook Marsh (New Hampshire) and at Drakes Island Marsh (Maine) where partial tidal restoration inadvertently occurred. Salt marsh functions were evaluated in both marshes to determine the impacts from tidal restriction and the responses following restoration. Physical and biological indicators of salt marsh functions (tidal range, surface elevations, soil water levels and salinities, plant cover, and fish use) were measured and compared to those from nonimpounded reference sites. Common impacts from tidal restrictions at both sites were: loss of tidal flooding, declines in surface elevation, reduced soil salinity, replacement of salt marsh vegetation by fresh and brackish plants, and loss of fish use of the marsh.Water levels, soil salinities and fish use increased immediately following tidal restoration. Salt-intolerant vegetation was killed within months. After two years, mildly salt-tolerant vegetation had been largely replaced in Mill Brook Marsh by several species characteristic of both high and low salt marshes. Eight years after the unplanned, partial tidal restoration at Drakes Island Marsh, the vegetation was dominated bySpartina alterniflora, a characteristic species of low marsh habitat.Hydrologic restoration that allowed for unrestricted saltwater exchange at Mill Brook restored salt marsh functions relatively quickly in comparison to the partial tidal restoration at Drakes Island, where full tidal exchange was not achieved. The irregular tidal regime at Drakes Island resulted in vegetation cover and patterns dissimilar to those of the high marsh used as a reference. The proper hydrologic regime (flooding height, duration and frequency) is essential to promote the rapid recovery of salt marsh functions. We predict that functional recovery will be relatively quick at Mill Brook, but believe that the habitat at Drakes Island will not become equivalent to that of the reference marsh unless the hydrology is further modified.Corresponding Editor: R.E. Turner Manuseript 相似文献
17.
D. M. Burdick M. Dionne R. M. Boumans F. T. Short 《Wetlands Ecology and Management》1996,4(2):129-144
Efforts are underway to restore tidal flow in New England salt marshes that were negatively impacted by tidal restrictions. We evaluated a planned tidal restoration at Mill Brook Marsh (New Hampshire) and at Drakes Island Marsh (Maine) where partial tidal restoration inadvertently occurred. Salt marsh functions were evaluated in both marshes to determine the impacts from tidal restriction and the responses following restoration. Physical and biological indicators of salt marsh functions (tidal range, surface elevations, soil water levels and salinities, plant cover, and fish use) were measured and compared to those from nonimpounded reference sites. Common impacts from tidal restrictions at both sites were: loss of tidal flooding, declines in surface elevation, reduced soil salinity, replacement of salt marsh vegetation by fresh and brackish plants, and loss of fish use of the marsh. Water levels, soil salinities and fish use increased immediately following tidal restoration. Salt-intolerant vegetation was killed within months. After two years, mildly salt-tolerant vegetation had been largely replaced in Mill Brook Marsh by several species characteristic of both high and low salt marshes. Eight years after the unplanned, partial tidal restoration at Drakes Island Marsh, the vegetation was dominated bySpartina alterniflora, a characteristic species of low marsh habitat. Hydrologic restoration that allowed for unrestricted saltwater exchange at Mill Brook restored salt marsh functions relatively quickly in comparison to the partial tidal restoration at Drakes Island, where full tidal exchange was not achieved. The irregular tidal regime at Drakes Island resulted in vegetation cover and patterns dissimilar to those of the high marsh used as a reference. The proper hydrologic regime (flooding height, duration and frequency) is essential to promote the rapid recovery of salt marsh functions. We predict that functional recovery will be relatively quick at Mill Brook, but believe that the habitat at Drakes Island will not become equivalent to that of the reference marsh unless the hydrology is further modified. 相似文献
18.
Previous research on intertidal nekton communities has identifiedimportant determinants of community structure and distribution;
however, fewstudies have compared nekton utilization of disparate marsh habitats. Inthis study, abundance and distribution
patterns of resident nekton werecompared between tidal freshwater marsh and salt marsh surfaces varying inflooding depth and
duration. Nekton were collected in pit traps installedalong elevational transects at four marshes in coastal Virginia (twofreshwater,
two saline) from April through November 1992–1993. Thedominant fish collected at all sites was the mummichog Fundulusheteroclitus.
The daggerblade grass shrimp Palaemonetes pugio was thedominant nekton species collected at salt marsh sites, and was seasonallyabundant
on tidal freshwater marshes. A positive correlation betweenflooding depth and nekton abundance was observed on salt marshes;
anopposite pattern was observed on tidal freshwater marshes. Tidal floodingregime influences the abundance of resident nekton,
however, the effect maybe confounded by other environmental variables, including variation insurface topography and seasonal
presence or absence of submerged aquaticvegetation (SAV) in adjacent subtidal areas. In mid-Atlantic tidalfreshwater wetlands,
SAV provides a predation refuge and forage site forearly life stages of marsh-dependent nekton, and several species utilizethis
environment extensively. Salt marshes in this region generally lackdense SAV in adjacent subtidal creeks. Consequently, between-sitedifferences
in species and size-specific marsh surface utilization byresident nekton were observed. Larvae and juveniles represented 79%and
59% of total fish collected at tidal freshwater and salt marshsites, respectively. The resident nekton communities of tidal
freshwater andsalt marsh surfaces are characterized by a few ubiquitous species with broadenvironmental tolerances.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
In recent years, salt marsh restoration projects have focused upon restoring hydrology through culvert enlargement to return functional values lost due to reduced tidal flow. To evaluate culvert effects on upstream nekton assemblages, fyke nets were set upstream of tidally restricted creeks, creeks recently restored with larger culverts, and paired reference creeks in New Hampshire and Maine, U.S.A. Subtidal habitats created or enlarged by scour were found immediately upstream of undersized culverts. All marshes supported similar assemblages and densities of fish, suggesting that marshes upstream of moderately restrictive culverts provide suitable habitat to support fish communities. However, densities of Crangon septemspinosa (sand shrimp) were significantly reduced upstream of culverts. A mark–recapture study was conducted in tidally restricted, restored, and reference marsh creeks to evaluate culvert effects on the movement of Fundulus heteroclitus (mummichog), the numerically dominant fish species in New England salt marshes. Recapture data indicated that small culvert size and consequently increased water velocity significantly decreased fish passage rates. We infer that upstream subtidal habitats and greater water velocities due to undersized culverts decreased nekton movements between upstream and downstream areas, resulting in segregated nekton populations. Restoration of salt marsh hydrology by the installation of adequately sized culverts will support increased fish access to marsh habitats and nekton‐mediated export of marsh‐derived production to coastal waters. 相似文献
20.
R.T. Kneib 《Journal of experimental marine biology and ecology》1984,83(1):41-51
Larval and juvenile fishes were collected at low tide from the surface of an intertidal salt marsh on Sapelo Island, Georgia every 6 days from 25 May through 20 December 1982. Larval fishes were present in shallow puddles of tidal water on the marsh from the beginning of the sampling period until the end of October. Juveniles were present throughout the year. Fundulus heteroclitus (Linnaeus) and F. luciae (Baird) accounted for 96.3% (67.0% and 29.3%, respectively) of the 4355 fishes collected. These fishes exhibited synchronous, temporal pulses in larval abundance, suggesting that reproduction was discontinuous and controlled by the same factor(s) in both species. Larval F. heteroclitus inhabited aquatic micro-habitats near the upland edge of the intertidal marsh, but as the larvae grew to juvenile size (≈ 10 mm standard length) they moved to lower elevations near a tidal creek. Large juveniles and adults of F. heteroclitus infrequently occurred in the samples, presumably because they leave the intertidal marsh as the tide ebbs. F. luciae were rarely found in low marsh areas, but all age classes (including adults) occurred at higher elevations, supporting previous suggestions that this species prefers high marsh habitats. The vegetated, intertidal salt marsh appears to be the principal nursery habitat for both of these cyprinodontid species. 相似文献