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1.
Few studies concerning tide-restricted and restoring salt marshes emphasize fishes and decapod crustaceans (nekton) despite
their ecological significance. This study quantifies nekton utilization of three New England salt marshes under tide-restricted
and restoring conditions (Hatches Harbor, Massachusetts; Sachuest Point and Galilee, Rhode Island). The degree of tidal restriction
differed among marshes allowing for an examination of nekton utilization patterns along a gradient of tidal restriction and
subsequent restoration. Based on sampling in shallow subtidal creeks and pools, nekton density and richness were significantly
lower in the restricted marsh compared to the unrestricted marsh only at the most tide-restricted site (Sachuest Point). The
dissimilarity in community composition between the unrestricted and restricted marsh sites increased with more pronounced
tidal restriction. The increase in nekton density resulting from tidal restoration was positively related to the increase
in tidal range. Species richness only increased with restoration at the most tide-restricted site; no significant change was
observed at the other two sites. These patterns suggest that only severe tidal restrictions significantly reduce the habitat
value of New England salt marshes for shallow subtidal nekton. This study suggests that the greatest responses by nekton,
and the most dramatic shift towards a more natural nekton assemblage, will occur with restoration of severely restricted salt
marshes. 相似文献
2.
In Louisiana, salt marshes are being created in an effort to offset the large loss of such habitat that has occurred over the last 50 yr. Primary productivity is an important function and indicator of success for salt marsh creation and restoration projects. The aim of this study was to determine whether the aboveground and belowground productivity of the dominant salt marsh grassSpartina alterniflora in created marshes in southwest Louisiana began to approximate productivity levels in natural marshes, over time. Net annual aboveground primary productivity (NAPP) was measured by a harvest technique, while the ingrowth core method was used to estimate net annual belowground primary productivity (NBPP). NAPP levels were similar to those found in other, Louisiana salt marshes, while NBPP levels were similar to or higher than the reported range forS. alterniflora studied along the Atlantic and Gulf of Mexico coasts. NAPP tended to decrease as the created marshes aged, but the levels in the oldest, 19 year old, created marsh were still well above values measured in the, natural marshes. It was estimated that it would take 35 yr after marsh creation for NAPP in the created marshes to become equivalent to that in natural marshes. NBPP in the created marshes became equivalent to levels found in the natural marshes after 6–8 yr, but then belowground production increased with marsh age, reaching an asymptote that surpassed natural marsh levels. Equivalency in primary productivity has not been reached in these marshes. Elevation also affected productivity, as higher elevational sites with greater topographic heterogeneity had significantly lower aboveground and belowground biomass levels than those with elevations closer to mean sea level. This underscores the need to construct marshes so that their mean elevation and degree of topographic heterogeneity are similar to natural marshes. 相似文献
3.
Patterns of nekton occurrence on the salt marsh surface at high tide and in an adjacent intertidal creek pool at low tide were used to investigate movements of nekton in an intertidal basin. Paired collections were made in North Inlet estuary, SC on 67 dates over 9 years. Comparisons of high- and low-tide total abundance indicated that what remained in the creek pool at low tide was representative of the nekton on the flooded marsh. Of the 64 taxa collected, the same 8 species ranked in the top 10 in both the high- and low-tide collections. Abundances of most resident species were positively correlated with the area of marsh flooded, but mummichog (Fundulus heteroclitus), the most abundant resident, was not. Abundances of young-of-the-year transient species were not related to the extent of tidal flooding. Some transient species used the flooded marsh but did not occupy the pool at low tide, and others found in the pool did not use the marsh. Differences in abundance, biomass, and length between the marsh and pool collections indicated differences in the tendency of species and life stages to retreat downstream of the pool to the subtidal channel. Proportionately more of the nekton that were present on the flooded marsh left the intertidal basin when large changes in temperature and salinity occurred between high and low tides. More transients left the basin following higher tides, but more residents did not. The results demonstrate a wide range of taxonomic and ontogenetic patterns among nekton using intertidal salt marsh basins and the underappreciated importance of intertidal creek pools as alternative low-tide refuges. 相似文献
4.
Flooding of salt marshes controls access to the marsh surface for aquatic organisms and likely regulates the value and use
of this habitat for juvenile fishery species. We examined geographic variability in marsh access by measuring tidal flooding
characteristics in 15 Spartina alterniflora marshes in the southeastern US between South Texas and lower Chesapeake Bay. Flooding duration and flooding frequency were
correlated with the elevation of the marsh edge in relation to mean low water and with the tidal range. Mean annual flooding
duration over the years 2006–2008 was highest in Texas (91.5% in Aransas Bay) and North Carolina (89.3% in Pamlico Sound)
and lowest in Timbalier Bay, LA (54%) and the lower Carolinas and Georgia (55–57%). We used published data on densities of
blue crabs and penaeid shrimps as a measure of habitat selection, and there was a positive relationship between marsh selection
and flooding duration. 相似文献
5.
We used137Cs-dating to determine vertical accretion rates of 15 salt marshes on the Bay of Fundy, the Gulf of St. Lawrence, and the
Atlantic coast of Nova Scotia. Accretion rates are compared to a number of factors assumed to influence vertical marsh accretion:
rates of relative sea-level rise, climatic parameters (average daily temperatures and degree days) and latitude (related to
insolation and day length), sediment characteristics (organic matter inventory, bulk, mineral, and organic matter density),
distance of the core site from the nearest source of tidal waters, and the tidal range. Uniques to our study is a consideration
of climatic parameters and latitude, which should influence organic matter production, and thus vertical accretion rates.
Significant predictors of accretion rates (in order of importance) were found to be organic matter inventory, distance from
a creek, and range of mean tides. Contrary to conclusions from previous studies, we found that accretion rates decreased with
increasing tidal range, probably because we considered a wider span of tidal ranges, from micro- to macrotidal. Although four
marshes with low organic matter inventories also show a deficit in accretion with respect to relative sea-level rise, organic
matter is not limiting in two-thirds of the marshes studied, despite shorter growing seasons. 相似文献
6.
An analysis of data relatingSpartina alterniflora Loisel. to tidal elevations along the Atlantic and Gulf coasts demonstrated that although this species is primarily confined to the intertidal zone, its elevational limits. of occurrence do not correspond to a consistent elevation relative to a tidal datum in all marsh locations. The variation in the vertical distribution of this species reported among marsh studies was attributed primarily to differences in mean tide range (MTR). A positive correlation between MTR and elevational growth range (r=0.91) demonstrated that theSpartina alterniflora zone expands with increasing tidal amplitude. Differences in MTR among marsh locations accounted for 70 and 68% of the statistical variation in the upper and lower limits, respectively, ofS. alterniflora growth. Among marshes of similar tidal amplitudes, the upper limit of occurrence ofS. alterniflora in northern marshes was significantly lower than that in marshes at lower latitudes. These results, in combination with regional differences in plant species distribution across the upper intertidal zone, suggested that some of the variation in the upper limit was due to latitudinal differences in growth conditions and/or differences in interspecific competition. Local and regional differences in other factors such as salinity, nutrients, or physical disturbance may have also contributed to the variation in the limits of growth relative to a tidal plane within and among marshes. 相似文献
7.
Large-scale marsh restoration efforts were conducted to restore normal salt marsh structure and function to degraded marshes
(i.e., former salt hay farms) in the mesohaline lower Delaware Bay. While nekton response has been previously evaluated for
the marsh surface and subtidal creeks in these marshes, little effort has been focused on intertidal creeks. Nekton response
in intertidal creeks was evaluated by sampling with seines to determine if restored (i.e., former salt hay farms restored
in 1996) and reference (i.e., natural or relatively undisturbed) salt marshes were utilized by intertidal nekton in a similar
manner. The overall nekton assemblage during June–October 2004–2005 was generally comprised of the same species in both the
restored and reference marshes. Intertidal creek catches in both marsh types consisted primarily ofFundulus heteroclitus andMenidia menidia, with varying numbers of less abundant transient species present. Transient nekton were more abundant at restored marshes
than reference marshes, but in insufficient numbers to cause differences in nekton assemblages. In both marsh types, low tide
stages were characterized by resident nekton, dominated byF. heteroclitus, while high tide stages were characterized by a variable mix of transient and resident nekton. Assemblage level analyses
indicated that intertidal creeks in restored and reference marshes were generally utilized in a similar manner by a similar
nekton assemblage, so restoration efforts were deemed successful. This is in agreement with multiple comparative studies from
the ame marshes examining fish, invertebrates, and vegetation in different marsh habitats. 相似文献
8.
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. 相似文献
9.
Elizabeth Burke Watson Cathleen Wigand Earl W. Davey Holly M. Andrews Joseph Bishop Kenneth B. Raposa 《Estuaries and Coasts》2017,40(3):662-681
Tidal salt marsh is a key defense against, yet is especially vulnerable to, the effects of accelerated sea level rise. To determine whether salt marshes in southern New England will be stable given increasing inundation over the coming decades, we examined current loss patterns, inundation-productivity feedbacks, and sustaining processes. A multi-decadal analysis of salt marsh aerial extent using historic imagery and maps revealed that salt marsh vegetation loss is both widespread and accelerating, with vegetation loss rates over the past four decades summing to 17.3 %. Landward retreat of the marsh edge, widening and headward expansion of tidal channel networks, loss of marsh islands, and the development and enlargement of interior depressions found on the marsh platform contributed to vegetation loss. Inundation due to sea level rise is strongly suggested as a primary driver: vegetation loss rates were significantly negatively correlated with marsh elevation (r 2?=?0.96; p?=?0.0038), with marshes situated below mean high water (MHW) experiencing greater declines than marshes sitting well above MHW. Growth experiments with Spartina alterniflora, the Atlantic salt marsh ecosystem dominant, across a range of elevations and inundation regimes further established that greater inundation decreases belowground biomass production of S. alterniflora and, thus, negatively impacts organic matter accumulation. These results suggest that southern New England salt marshes are already experiencing deterioration and fragmentation in response to sea level rise and may not be stable as tidal flooding increases in the future. 相似文献
10.
Paul E. Fell Nancy C. Olmstead Elaine Carlson William Jacob Diane Hitchcock Gregory Silber 《Estuaries and Coasts》1982,5(3):234-239
The distribution of macroinvertebrates on Connecticut tidal marshes corresponds well with that reported for other marshes along the Atlantic and Gulf coasts of the United States. The greatest densities and biomass of the ribbed mussel,Geukensia demissa, were found on marshes in the central and western part of the state where both the annual production ofSpartina alterniflora and tidal range are large. *** DIRECT SUPPORT *** A01BY019 00011 相似文献
11.
We sampled nekton (fishes and decapod crustaceans) in submerged aquatic vegetation (SAV) (Potanogeton nodosus, Najas guadalupensis), in emergent marsh vegetation (Sagittaria spp. andScirpus americanus), and over unvegetated bottom associated with three islands in the Atchafalaya River Delta, Louisiana. The purpose of our study was to quantify nekton densities in these major aquatic habitat types and to document the relative importance of these areas to numerically dominant aquatic organisms. We collected a total of 33 species of fishes and 7 species of crustaceans in 298 1-m2 throw trap samples taken over three seasons: summer (July and August 1994), fall (September and October 1994), and spring (May and June 1995). Fishes numerically accounted for >65% of the total organisms collected. Vegetated areas generally supported much higher nekton densities than unvegetated sites, although bay anchoviesAnchoa mitchilli were more abundant over unvegetated bottom than in most vegetated habitat types. Among vegetation types, most species showed no apparent preference between SAV and marsh. However, inland silversidesMenidia beryllina and freshwater gobiesGobionellus shufeldti were most abundant inScirpus marsh in summer, and blue crabsCallinectes sapidus were most abundant in SAV (Potamogeton) in spring. Several species (sheepshead minnowCyprinodon variegatus, rainwater killifishLucania parva, and blue crab) apparently selected the vegetated backmarsh of islands (opposite of riverside) over stream-sideScirpus marsh. Freshwater gobies, in contrast, were most abundant in streamsideScirpus marsh. Densities of juvenile blue crabs were high (up to 17 m−2) in vegetated delta habitat types and comparable to values reported from more saline regions of Gulf Coast estuaries. Shallow vegetated habitat types of the Atchafalaya River Delta and other tidal freshwater systems of the Gulf Coast may be important nursery areas for blue crabs and other estuarine species. 相似文献
12.
We describe the use of flume nets for passively, quantitatively, and nondestructively sampling fishes and macrocrustaceans on tidal marsh surfaces. We captured 3,765 organisms of 23 species in 118 samples using six such nets in a Virginia tidal freshwater marsh in 1984. Efficiency estimates for four common species of fishes range from 53 to 80%. Flume nets are most suited to the collection of long-term data and are particularly useful in elucidating seasonal trends in species composition and relative abundance. These nets are also useful in comparing different microhabitats within and between marshes. This method is most applicable to intertidal habitats with predictable lunar tides, including mud flats, mangrove swamps, and other wetlands. 相似文献
13.
R. T. Kneib 《Estuaries and Coasts》1997,20(1):214-230
Variability in early life stages of species that are permanent residents of the estuarine nekton is poorly understood, especially in systems with extensive areas of emergent vegetation (e.g., salt marshes and mangroves). Sampling small mobile nekton in these shallow intertidal habitats presents a difficult methodological challenge. Simulated aquatic microhabitats (SAMs) were used to collect the early life stages of resident nekton that remained on the emergent marsh surface after it was exposed by the tide and could not be adequately sampled by traditional methods. Where the intertidal is a prominent areal component of the estuary, a large portion of young nekton could be overlooked using other common survey methods (e.g., plankton tows or block nets). Populations of young fishes and natant crustaceans were monitored for a year at 3-d to 6-d intervals from both low and high intertidal elevations within each of two marsh sites on Sapelo Island, Georgia, USA. Three species accounted for >99% of the 41,023 individuals collected. These were the killifishesFundulus heteroclitus (57.0%) andF. luciae (4.0%), and the daggerblade grass shrimp,Palaemonetes pugio (38.4%). YoungF. heteroclitus were used in field enclosure experiments to relate abundance data to actual areal densities. Average annual estimated density of young nekton on the surface of the intertidal marsh at low tide was 7.2 individuals m?2. Early life stages of estuarine resident species, particularly those with demersal young, are not affected by the same physical processes influencing larval supply and recruitment variability in marine-spawned species. In salt marshes, biotic factors (e.g., adult reproductive activity, predation, and food limitation) may be more important as proximate causes of variation during the early life histories of resident nekton. 相似文献
14.
Nutrient availability is known to mediate plant community structure in many systems, but relatively few studies of nutrient effects have been done in systems where strong gradients in physical stress might constrain the effects of nutrients. Recent studies in New England, United States, salt marshes indicate that nutrients may strongly mediate plant community composition by increasing the competitive ability of stress-tolerant species that are normally displaced by competition to recently-disturbed or low-intertidal habitats. It is unknown whether these results can be generalized to salt marshes in other geographic regions that experience different climates, tidal regimes, and edaphic conditions. To address the generality of these results from New England, we fertilized seven different mixtures of salt marsh plants at study sites on the southeast and Gulf coasts of the U.S. Two of these mixtures were studied in both geographic regions. Consistent with results from New England, fertilization always increased the biomass of the low-marsh dominantSpartina alterniflora and usually led to it increasing in dominance at the expense of high-marsh species. Fertilization also led to increased community dominance byDistichlis, but only in a mixture where it was already common. Fertilization led to changes in plant dominance patterns in four of the seven types of mixtures that we studied. Results were not a function of edaphic conditions, at least within the range included in our study, and were consistent between the southeastern and Gulf coasts, which experience markedly different tidal regimes. The broad similarity of these results suggests that changes in nutrient input may lead to predictable changes in the composition of similar salt marsh plant communities across large geographic areas despite site to site variation in the abiotic environment. 相似文献
15.
Currently, the largest tidal wetlands restoration project on the US Pacific Coast is being planned and implemented in southern San Francisco Bay; however, knowledge of baseline conditions of salt marsh extent in the region prior to European settlement is limited. Here, analysis of 24 sediment cores collected from ten intact southern San Francisco Bay tidal marshes were used to reconstruct spatio-temporal patterns of marsh expansion to provide historic context for current restoration efforts. A process-based marsh elevation simulation model was used to identify interactions between sediment supply, sea-level rise, and marsh formation rates. A distinct age gradient was found: expansion of marshes in the central portion of southern San Francisco Bay dated to 500 to 1500 calendar years before present, while expansion of marshes in southernmost San Francisco Bay dated to 200 to 700 calendar years before present. Thus, much of the tidal marsh area mapped by US Coast Survey during the 1853–1857 period were in fact not primeval tidal marshes that had persisted for millennia but were recently formed landscapes. Marsh expansion increased during the Little Ice Age, when freshwater inflow and sediment influx were higher than during the previous millennium, and also during settlement, when land use changes, such as introduction of livestock, increased watershed erosion, and sediment delivery. 相似文献
16.
Ilia Rochlin Mary-Jane James-Pirri Susan C. Adamowicz Mary E. Dempsey Thomas Iwanejko Dominick V. Ninivaggi 《Estuaries and Coasts》2012,35(3):727-742
An integrated marsh management (IMM) project in an urbanized watershed on Long Island, New York, USA, aimed to mitigate salt marsh degradation and to reduce mosquito production by an innovative combination of restoration and open marsh water management methods. The grid ditch network at two treatment marshes was replaced with naturalized tidal channels and ponds. Effects of the hydrologic alterations were monitored utilizing a before–after–control–impact approach. The treatment marshes experienced a number of beneficial outcomes including a fourfold reduction in the invasive Phragmites australis and increased native vegetation cover in the most degraded portions of the marsh, increased abundance and diversity of marsh killifish and estuarine nekton species, higher shorebird and waterfowl densities, and increased avian species diversity. The successful implementation of IMM concept led to improved marsh health and diminished mosquito production. Therefore, this study may serve as a template for similar large-scale integrated salt marsh restoration projects. 相似文献
17.
One of the steepest depositional coasts of western James Bay is found along the west shores of Akimiski Strait, north of the mouth of the Ekwan River. This shore receives considerable amounts of sediment during the spring break-up of the rivers. The sediments are stored on the steep narrow tidal flats and marshes, and in thinner (up to 80 cm) drapes on till-cored shoals that parallel and protect the coast. The low areas between the shoals and the mainland are swept and reworked by relatively powerful (2 m s?1) reversing currents due to flooding and ebbing of tides into the strait.A series of distinct environments and sedimentary facies develop on this western coast and its antecedent longshore shoal. The outer part of the shoal is characterized by tidal bedding, Macoma balthica burrows and considerable ice scour. The inner part of the shoal has winnowed sand, the greatest abundance of Macoma, and well-developed flaser bedding. The longshore tidal channel separating the shoal from the mainland has coarse sand lags in the shallower parts and silty sand in deeper protected areas. The steep tidal flats develop laminated silty sands locally saturated and slumping toward the channel. The high saturation of the sediments inhibits colonization of the flats by Macoma. The narrow marshes have characteristic vegetation zonation, with Puccinellia phryganodes colonizing the lower marsh. The sedimentary sequence of the marsh displays irregular, bioturbated laminated sequences of silt, silty sand and organic matter. 相似文献
18.
Linda A. Deegan 《Estuaries and Coasts》2002,25(4):727-742
Coastal ecosystems such as eelgrass beds and salt marshes have always been valued for their high productivity and rich bounty of fish and shellfish. High plant productivity, complex physical structure, and suitable environmental characteristics combine to create areas of high production of important recreational and commercial species. If we are to successfully manage and restore these ecosystems, it is important to understand the mechanisms by which support of nekton may be affected by nutrient enrichment. A review of the literature suggests that there are some similarities and differences in the effects of nutrient enrichment on the support of nekton by seagrass and salt marsh ecosystems. Nutrient enrichment may compromise the ability of these habitats to support fish and invertebrates before the habitat itself is gone. In both ecosystems, alteration of characteristics within the ecosystem (for example, stem density in seagrass and food webs in marshes) affect the support of nekton, even though the basic ecosystem is still clearly extant. Because of differences in natural ecosystem characteristics, loss of ecosystem function does not occur through the same mechanisms. In seagrass systems, physical structure is usually lost first, followed by alteration of food webs and finally changes in dissolved oxygen. In salt marsh systems, loss of dissolved oxygen may occur early in the process, followed by food web alterations and eventually changes in the physical structure may occur. For both seagrass and salt marsh ecosystems, the mechanisms suggested to operate at the ecosystem-level are often based on relatively small-scale plot experiments that have been conducted in only a few locations. A better understanding of how these ecosystems function across broad geographic regions will be needed to ensure functioning coastal ecosystems. 相似文献
19.
Planimetry studies of coastal geology maps prepared by the Maine Geological Survey show that there is more than an order of magnitude more tidal marsh area in the state of Maine than documented in previously published estimates. The highly convoluted coast of Maine, which is approximately 5,970 km long, contains almost 79 km2 of salt marsh, far more than any other New England state, New York, or the Bay of Fundy region. Reasonable estimates for the per-unit primary productivity of salt marshes lead to projections of total marsh productivity on the order of 1010 g dry weight yr?1 for the Maine coast and 1011 g dry weight yr?1 for the Gulf of Maine as a whole. Distribution of tidal marsh area is strongly controlled by coastal geomorphology, which varies considerably along the coast of Maine. The salt marsh area is concentrated in the southwestern coastal region of arcuate bays, where marshes have developed behind sandy beaches. A series of long islands and bedrock peninsulas in the south-central portion of the coast also provides sheltered areas where large marshes occur. Northeast of Penobscot Bay salt marshes become more numerous and smaller in average areal extent. A lack of protection from waves, along with limited sources of glacio-fluvial and glacio-marine sediments, restricts the occurrence of salt marshes in that region to the frignes of coves and tidal rivers. 相似文献
20.
The Gulf Killifish (Fundulus grandis) is one of the most abundant nekton species in the US Gulf of Mexico (GOM) salt marshes, providing an important trophic link in these systems. Recently, the use of F. grandis as an indicator species of salt marsh health in the region has been suggested because its Atlantic coast congener, the Mummichog (Fundulus heteroclitus) has filled such a role due to its demonstrated high site fidelity and small-scale movements. Given the similar life histories between species, F. grandis was assumed to exhibit the same type of small-scale movements, although this has not been documented. During summer 2013, we collected and marked 1,719 fish from a northern Gulf of Mexico estuary, recapturing 959 (56 % recapture rate). Of these recaptured fish, only 31 moved from their original tagging location, and of these, 29 moved only 100 m between sites connected by salt marsh. Based on these results, F. grandis appears to exhibit high site fidelity and make only small-scale movements, similar to F. heteroclitus, supporting its role as an indicator species. 相似文献