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1.
This paper examines how perennial Aster tripolium and annual Salicornia procumbens salt marshes alter the biomass, density, taxon diversity, and community structure of benthic macrofauna, and also examines
the role of elevation, sediment grain size, plant cover, and marsh age. Core samples were collected on a fixed grid on an
intertidal flat in the Westerschelde estuary (51.4° N, 4.1° E) over 5 years (2004–2008) of salt marsh development. In unvegetated
areas, macrobenthic biomass, density, and taxon diversity were highest when elevation was highest, benthic diatoms were most
abundant, and sediment median grain size was smallest. In contrast, in salt marsh areas, macrobenthic biomass and taxon diversity
increased with median grain size, while the effects of elevation and diatom abundance on macrobenthic biomass, density, and
diversity were not significant. In fine sediments, macrofaunal community structure in the salt marsh was particularly affected;
common polychaetes such as Nereis diversicolor, Heteromastus filiformis, and Pygospio elegans had low abundance and oligochaetes had high abundance. Marsh age had a negative influence on the density of macrofauna, and
A. tripolium stands had lower macrofaunal densities than the younger S. procumbens stands. There were no significant effects of marsh age, plant cover, and vegetation type on macrobenthic biomass, taxon diversity,
and community structure. The results highlight that ecosystem engineering effects of salt marsh plants on macrofauna are conditional.
Organic enrichment of the sediment and mechanical hindering of macrofaunal activity by plant roots are proposed as plausible
mechanisms for the influence of the salt marsh plants on macrofauna. 相似文献
2.
In the tidal creeks of the southeastern United States, the numerically and ecologically dominant macrobenthic organisms are
typically oligochaetes. Due to their relatively small size and difficult taxonomy, little is known about the short-term and
seasonal changes in the oligochaetes of tidal creeks. This study presents a report of the spatial and temporal changes of
the oligochaete taxa within and between two tidal creeks in southern South Carolina, at monthly intervals over a 13-month
period. These changes are framed within the reference of monthly changes in benthic chlorophylla, sediment composition, and porewater ammonia, as well as in the perspective of seasonal changes in the entire tidal creek
macrobenthic community. The most abundant oligochaete found in this study was the tubificidMonopylephorus rubroniveus, followed by the naidParanais litoralis and the tubificidsTubificoides heterochaetus andT. brownae. All of the oligochaetes exhibited strong month-to-month and spatial changes, indicative of changes in water quality and
sediment habitat characteristics (e.g., low dissolved oxygen, high benthic chlorophylla). There were significant correlations between the abundance of most species and either benthic chlorophylla concentration or the silt-clay fraction of the sediment. Looking at short-term changes in this rapidly changing component
of the macrobenthic community provides insight not only into the ecology of the oligochaetes, but also into the changes in
the tidal creek ecosystem and their potential effects on other biota. 相似文献
3.
In a continuing effort to monitor the fish response to marsh restoration (resumed tidal flow, creation of creeks), we compared
qualitative and quantitative data on species richness, abundance, assemblage structure and growth between pre-restoration
and post-restoration conditions at two former salt hay farms relative to a reference marsh in the mesohaline portion of Delaware
Bay. The most extensive comparison, during April–November 1998, sampled fish populations in large marsh creeks with otter
trawls and in small marsh creeks with weirs. Species richness and abundance increased dramatically after restoration. Subsequent
comparisons indicated that fish size, assemblage structure, and growth of one of the dominant species,Micropogonias undulatus, was similar between reference and restored marshes 1 and 2 yr post-restoration. Total fish abundance and abundance of the
dominant species was greater, often by an order of magnitude, in one of the older restored sites (2 yr post-restoration),
while the other restored site (1 yr post-restoration) had values similar to the reference marsh. The success of the restoration
at the time of this study suggests that return of the tidal flow and increased marsh area and edge in intertidal and subtidal
creeks relative to the former salt hay farms contributed to the quick response of resident and transient young-of-the-year
fishes. 相似文献
4.
This two-part study examined the benthic macrofaunal community in Delaware salt marsh impoundments having partial tidal restriction. The first part compared abundance, diversity, and taxonomic composition in three habitat types in impoundments—creeks, vegetated creek banks, and ponds—to those found in natural marshes. Impoundment effects were present but were habitat-specific. Abundances were higher in natural marsh creeks than in impoundment creeks, and diversities were higher in impoundment ponds than in natural marsh ponds. Vegetated bank communities in impoundments were about 50% insects and arachnids and 50% oligochaetes, while natural bank communities were primarily oligochaetes and the polychaeteManayunkia aestuarina. This is likely due to the decrease in flooding of the vegetated high marsh caused by partial impoundment. Pond and creek community composition also showed impoundment effects: in comparison with natural marshes, impoundments had higher proportions of the burrowing anemoneNematostella vectensis, nemerteans, andTubificoides sp. oligochaetes and lower proportions of the oligochaeteClitellio arenarius. The second part of the study compared benthic macrofauna in an impoundment before, during, and after the water level was lowered so that some bottom sediments were exposed and some covered with just a few centimeters of water for several weeks. During this event, macrofaunal abundances were reduced and the community shifted from being dominated by annelids, anemones, and nemerteans toward one dominated by annelids and insects. About 6 wk after reflooding, persistent effects of this disturbance were still suggested by greatly increased abundances and 96% dominance by one species of oligochaete,Paranais litoralis. Impoundment management plans calling for periods of sediment exposure or very low water may want to consider the potential for strong and persistent effects on the macrofaunal community. 相似文献
5.
Macrobenthic community indices were examined for their ability to characterize the influence of shoreline alteration and watershed
land use in nearshore estuarine environments of the Chesapeake Bay, U.S.A. Twenty-three watersheds were surveyed in 2002 and
2003 for nearshore macrobenthic assemblages, environmental parameters (i.e., dissolved oxygen, pH, total suspended solids,
salinity, and sediment composition), shoreline condition, and land use. Two indices of macrobenthic biological integrity,
benthic index of biological integrity in the nearshore (B-IBIN) and abundance biomass comparison (W-value), were evaluated for associations with environmental and shoreline condition,
and riparian and watershed land use. Comparisons between nearshore measures of the B-IBI with offshore values (>2 m; Chesapeake
Bay benthic index of biological integrity [B-IBICB]) were conducted to assess the ability of the index to reflect land use patterns at near and far proximities to shore. Nearshore
macrobenthic communities were represented by a total of 94 species (mean number of species =9.2 ± 0.4 sample−1), and were dominated by the phyla Arthropoda, Annelida, and Mollusca. Temporal variability in environmental conditions and
macrobenthic abundance and biomass may be attributable to the notable increase in precipitation in 2003 that led to nutrient
influxes and algal blooms. For the biotic indices applied in the nearshore, the highest scores were associated with forested
watersheds (W-value, B-IBIN). Ecological thresholds were identified with nonparametric change-point analysis, which indicated a significant reduction
in B-IBIN and W-value scores when the amount of developed shoreline exceeded 10% and developed watershed exceeded 12%, respectively. 相似文献
6.
We examined fish assemblages in tidal salt marsh creeks in Delaware Bay in order to evaluate their response to treatment forPhragmites removal following initial treatment in 1996. In Alloway Crrek, a tributary to Delaware Bay, reference creeks draining marsh of untreatedPhragmites or naturally occurringSpartina were compared with creeks in marshes treated forPhragmites removal. These reference and treated creeks occur in close proximity and share many characteristics including salinity, temperature, dissolved oxygen, and turbidity, although creeks inPhragmites sites differed slightly in bathymetry. We analyzed a time series of otter trawl collections (22 monthly sample periods from 1999 to 2001) for differences in juvenile fish assemblage among creeks with different vegetation history. Periodically, young-of-the-year (YOY) and age 1+ white perch (Morone americana), YOY spot (Leiostomus xanthurus), YOY Atlantic menhaden (Brevoortia tyrannus), and other species were relatively more abundant atPhragmites sites, but other dominant species were preiodically abundant at all sites. Among-treatment differences based on principal response curves analysis accounted for about 19% of the total species variation, but differences varied widely among sample periods and there is little or no indication of a trend over the 3-yr period. Larger collections were often associated with subtidal structure, which was more common atPhragmites sites and potentially represents a sampling artifact. Assemblages of creeks with differing vegetation history differ weakly but recognizably, suggesting slow or little response to treatment, at least based on otter trawl collections in subtidal marsh creeks.
相似文献7.
Kenneth W. Able Deborah N. Vivian Gina Petruzzelli Stacy M. Hagan 《Estuaries and Coasts》2012,35(3):743-753
We examined connectivity among marsh subhabitats to determine the structural limits and important components of a polyhaline
salt marsh by studying the patterns of abundance, residency, and movement of a numerically and ecologically dominant nektonic
fish (mummichog, Fundulus heteroclitus). We captured, tagged (n = 14,040 individuals, 30–110 mm), and recaptured from Feb 2001 to Jul 2002, although most recaptures (75–95% by tagging location)
occurred within 150 days. Seasonal residency and movements were common among most subhabitats based on catch per unit effort
and recapture per unit effort. Thus, these (marsh pools, intertidal and subtidal creeks, and marsh surface) should be considered
natural subhabitats within New England type salt marshes. Further, all these subhabitat types should be included in studies
of salt marsh nekton and marsh restoration and creation activities. 相似文献
8.
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
9.
The northern shore of Lake Ontario is one of the longest settled parts of Canada beginning around 1795. Accelerated settlement and deforestation after 1840 resulted in massive soil loss from easily-eroded Pleistocene glacial landscapes and the siltation of creeks and lagoons. Channel capacity was reduced but river flow was enhanced by diminished infiltration resulting in straightening of meandering channels, accelerated erosion of stream banks, increased incidence of downstream flooding and large influxes of mud to Lake Ontario. Conservation measures after World War II were successful but rapid urban sprawl after 1970 hardened watersheds and badly impacted the quality and quantity of surface and ground waters flowing to Lake Ontario. The Frenchman’s Bay watershed (27 km2) 50 km east of Toronto is one of the country’s most urbanized (pop: 100,000; 76 % urban cover) and is crossed by Canada’s busiest highway (Highway 401). The watershed drains to Lake Ontario through a coastal lagoon (Frenchman’s Bay) in which pre-settlement postglacial carbonate is abruptly overlain by a ‘European settlement’ mud layer rich in weed pollen and organic debris; the uppermost ‘urban’ part of this deposit shows elevated level of metals and other contaminants. This layer records soil loss after 1840 and more recently, the influx of contaminated urban waters and sediment. Some 7,600 tonnes of road salt have been applied to the lagoon watershed each year producing spikes of brackish surface runoff during winter thaws. Some 50 % of the total salt applied to the entire watershed is conveyed directly to Frenchman’s Bay Lagoon via surface runoff; the rest enters the groundwater system resulting in year-round brackish baseflow to creeks. Chloride continues to be stored in underlying aquifers such that the system has yet to reach a steady-state discharge. Future salinity of baseflow reaching the lagoon can be expected to increase by about 40 %. Rapid migration of contaminated groundwater is facilitated by the widespread presence of thick (<8 m) coarse-grained and heterogeneous fill materials of the built landscape. The watershed is experiencing ongoing changes in land use as urban infilling proceeds. The aquatic ecology of inflowing creeks to the lagoon has been greatly impacted resulting in major loss of wetlands and submergent vegetation and distinct changes in the structure of fish populations. This is the most detailed study of an urban watershed in Canada; lack of knowledge elsewhere is a constraint on the design and testing of mitigation measures and is a major impediment to assessing the impact of ongoing climate change on urban water resources, and the effects of urban runoff on Great Lakes water quality. 相似文献
10.
Delaware Bay is one of the largest estuaries on the U.S. eastern seaboard and is flanked by some of the most extensive salt marshes found in the northeastern U.S. While physicochemical and biotic gradients are known to occur along the long axis of the bay, no studies to date have investigated how the fish assemblage found in salt marsh creeks vary along this axis. The marshes of the lower portion of the bay, with higher salinity, are dominated bySpartina spp., while the marshes of the upper portion, with lower salinity, are currently composed primarily of common reed,Phragmites australis, S. alterniflora, or combinations of both. Extensive daytime sampling (n=815 tows) during May–November 1996 was conducted with otter trawls (4.9 m, 6 mm mesh) in six intertidal and subtidal marsh creek systems (upper and lower portions of each creek) where creek channel depths ranged from 1.4–2.8 m at high tide. The fish taxa of the marsh creeks was composed of 40 species that were dominated by demersal and pelagic forms including sciaenids (5 species), percichthyids (2), and clupeids (7), many of which are transients that spawn outside the bay but the early life history stages are abundant within the bay. The most abundant species wereMorone americana (24.3% of the total catch),Cynoscion regalis (15.4%),Micropogonias undulatus (15.3%),Anchoa mitchilli (12.0%), andTrinectes maculatus (10.8%). Non-metric Multi-Dimensional Scaling ordination of catch per unit effort (CPUE) data indicated two fish assemblages that were largely independent of the two major vegetation types, but generally corresponded with spatial variation in salinity. This relationship was more complex because some of the species for which we could discriminate different age classes by size had different patterns of distribution along the salinity gradient. 相似文献
11.
Shifting nutrient limitation and eutrophication effects in marsh vegetation across estuarine salinity gradients 总被引：1，自引：0，他引：1
Caitlin Mullan Crain 《Estuaries and Coasts》2007,30(1):26-34
In light of widespread coastal eutrophication, identifying which nutrients limit vegetation and the community consequences
when limitation is relaxed is critical to maintaining the health of estuarine marshes. Studies in temperate salt marshes have
generally identified nitrogen (N) as the primary limiting nutrient for marsh vegetation, but the limiting nutrient in low
salinity tidal marshes is unknown. I use a 3-yr nutrient addition experiment in mid elevation,Spartina patens dominated marshes that vary in salinity along two estuaries in southern Maine to examine variation in nutrient effects. Nutrient
limitation shifted across estuarine salinity gradients; salt and brackish marsh vegetation was N limited, while oligohaline
marsh vegetation was co-limited by N and phosphorus (P). Plant tissue analysis ofS. patens showed plants in the highest salinity marshes had the greatest percent N, despite N limitation, suggesting that N limitation
in salt marshes is partially driven by a high demand for N to aid in salinity tolerance. Fertilization had little effect on
species composition in monospecificS. patents stands of salt and brackish marshes, but N+P treatments in species-rich oligohaline marshes significantly altered community
composition, favoring dominance by high aboveground producing plants. Eutrophication by both N and P has the potential to
greatly reduce the characteristic high diversity of oligohaline marshes. Inputs of both nutrients in coastal watersheds must
be managed to protect the diversity and functioning of the full range of estuarine marshes. 相似文献
12.
John D. Lopez Mark S. Peterson Jake Walker Gretchen L. Grammer Mark S. Woodrey 《Estuaries and Coasts》2011,34(1):148-158
The saltmarsh topminnow (Fundulus jenkinsi) is federally listed as a Species of Concern due to a its rarity, impacts from human activities, and lack of information
on its biology and ecology. From 2007 through 2008, we used Breder traps to fish the marsh edge on a falling tide in four
regions from Louisiana through the Florida panhandle during winter, spring, and summer periods. Out of 2,108 Breder traps
deployed, 661 F. jenkinsi were collected as far east as Escambia Bay, Florida, with Weeks Bay, National Estuarine Research Reserve (NERR), Alabama,
yielding the highest F. jenkinsi abundance. Principal component analysis (PCA) was used to ordinate physical–chemical data into two meaningful components:
a geomorphic axis (water depth, bank slope, and plant stem density) and a seasonal/spatial axis of species occurrence (water
temperature, salinity, and turbidity). PCA showed a higher mean catch-per-unit-effort (CPUE) in environments comprised of
low to moderate stem density (<25 stems/0.25 m−2), depth (<25 cm), bank slope (<15°), turbidity (<30 NTU), and salinity (<16) coupled with spring and early summer water temperatures
(>15°C). F. jenkinsi CPUE was significantly higher in Spartina cynosuroides marsh edge compared with five other habitat types, even though it was one of the least sampled habitats. This species appears
to be collected more frequently and in higher CPUE in small dendritic creeks off of main channels than suggested by our previous
work in main channel edge habitat. This suggests that small creeks are important vectors for marsh access and supports the
value of the dendritic nature of salt marshes to marsh residents. 相似文献
13.
D. Sanger A. Blair G. DiDonato T. Washburn S. Jones G. Riekerk E. Wirth J. Stewart D. White L. Vandiver A. F. Holland 《Estuaries and Coasts》2015,38(1):49-66
Upland areas of southeastern United States tidal creek watersheds are popular locations for development, and they form part of the estuarine ecosystem characterized by high economic and ecological value. The primary objective of this work was to define the relationships between coastal development, with its concomitant land use changes and associated increases in nonpoint source pollution loading, and the ecological condition of tidal creek ecosystems including related consequences to human populations and coastal communities. Nineteen tidal creek systems, located along the southeastern US coast from southern North Carolina to southern Georgia, were sampled in the summer, 2005 and 2006. Within each system, creeks were divided into two primary segments based upon tidal zoning—intertidal (i.e., shallow, narrow headwater sections) and subtidal (i.e., deeper and wider sections)—and then watersheds were delineated for each segment. Relationships between coastal development, concomitant land use changes, nonpoint source pollution loading, the ecological condition of tidal creek ecosystems, and the potential impacts to human populations and coastal communities were evaluated. In particular, relationships were identified between the amount of impervious cover (indicator of coastal development) and a range of exposure and response measures including increased chemical contamination of the sediments, increased pathogens in the water, increased nitrate/nitrite levels, increased salinity range, decreased biological productivity of the macrobenthos, alterations to the food web, increased flooding potential, and increased human risk of exposure to pathogens and harmful chemicals. The integrity of tidal creeks, particularly the headwaters or intertidally dominated sections, was impaired by increases in nonpoint source pollution associated with sprawling urbanization (i.e., increases in impervious cover). This finding suggests that these habitats are valuable early warning sentinels of ensuing ecological impacts and potential public health and flooding risk from sprawling coastal development. The results also validate the use of a conceptual model with impervious cover thresholds for tidal creek systems in the southeast region. 相似文献
14.
0-group sea bass,Dicentrarchus labrax, colonize intertidal marsh creeks of Mont Saint Michel Bay, France, on spring tides (e.g., 43% of the tides) during flood
and return to coastal waters during ebb. Most arrived with empty stomachs (33%), and feed actively during their short stay
in the creeks (from 1 to 2 h) where they consumed on average a minimum of 8% of their body weight. During flood tide, diet
was dominated by mysids,Neomysis integer, which feed on marsh detritus. During ebb, when young sea bass left tidal marsh creeks, the majority had full stomachs (more
than 98%) and diet was dominated by the most abundant marsh (including vegetated tidal flats and associated marsh creeks)
resident amphipod,Orchestia gammarellus. Temporal and tidal effects on diet composition were shown to be insignificant. Foraging in vegetated flats occurs very rarely
since they are only flooded by about 5% of the tides. It was shown that primary and secondary production of intertidal salt
marshes play a fundamental role in the feeding of 0-group sea bass. This suggests that the well known nursery function of
estuarine systems, which is usually restricted to subtidal and intertidal flats, ought to be extended to the supratidal, vegetated
marshes and mainly to intertidal marsh creeks. 相似文献
15.
The conversion of undisturbed coastal regions to commercial and suburban developments may pose a threat to surface and groundwater quality by introducing nitrate-nitrogen (NO3 ?-N) from runoff of land-applied wastewater and fertilizers. Microbial denitrification is an important NO3 ?-N removal mechanism in coastal sediments. The objective of this study was to compare denitrification and nitrate conversion rates in coastal sediments from a golf course, suburban site, undeveloped marsh, and nonmarsh area near rapidly developing Hilton Head Island, South Carolina. Nitrous oxide was measured using gas chromatography and nitrate and ammonium concentrations were measured using a flow injection autoanalyzer in microcosms spiked, with 50 μg NO3 ?-N gdw?1. The two marsh sites had the greatest ammonium production, which was correlated with fine sediment particle size and higher background sediment nitrate and surface water sulfate concentrations. The golf course swale had greatest denitrification rates, which were correlated with higher total carbon and organic nitrogen in sediments. Nitrate was consumed in golf course sediments to a greater extent than in the undeveloped marsh and upland freshwater sites, suggesting that the undeveloped sites and receiving estuaries may be more susceptible to nitrate contamination than the golf course swale and marsh under nonstorm conditions. Construction of swales and vegetated buffers using sediments with high organic carbon content as best management practices may aid in removing nitrate and other contaminants from runoff prior to its transport to the receiving marsh and estuary. 相似文献
16.
Salt marsh intertidal creeks are important habitats for dozens of species of nekton, but few studies have attempted to quantify
patterns of tidal movement. We used the sweep flume, a new sampling device, to investigate relationships between depth and
movements of nekton inside the mouths of intertidal creeks. Sweep flumes located in three creek beds were used to collect
nekton at 10 cm increments (10–100 cm of water depth) during flood and ebb tides in the North Inlet, South Carolina, salt
marsh. Of the 37 taxa collected, 13 comprised>99.5% of the total catch and were the focus of the analysis. A nonlinear mixed
modeling procedure was used to determine, the depth at which each major taxon reached peak abundance during flood tides. With
high degrees of spatial and temporal consistency, resident taxa entered early on the rpsing tide and transient taxa entered
during mid to late tide. Depths of peak migrations varied among taxa and were consistent between creeks, days (within months),
and years. As summer progressed, depths of peak migration increased for young-of-the-yearLeiostomus xanthurus, Lagodon rhomboides, Mugil curema, Eucinostomus argenteus, andLitopenaeus setiferus as their median sizes increased. Within tides, depths of migration increased as a function of size forL. xanthurus andM. curema. Comparisons between flood and ebb tides indicated that most taxa exited the creeks at approximately the same depths at which
they entered. Relationships between major taxa pairs suggested that biotic interactions may have contributed to the structure
of the migrations observed in this study. Our results are the first to demonstrate quantitatively that the migrations of nektonic
taxa into intertidal creeks are structured and related to depth. 相似文献
17.
Anammox bacteria are widespread in the marine environment, but studies of anammox in marshes and other wetlands are still
scarce. In this study, the role of anammox in nitrogen removal from marsh sediments was surveyed in four vegetation types
characteristic of New England marshes and in unvegetated tidal creeks. The sites spanned a salinity gradient from 0 to 20 psu.
The impact of nitrogen loading on the role of anammox in marsh sediments was studied in a marsh fertilization experiment and
in marshes with high nitrogen loading entering through ground water. In all locations, nitrogen removal through anammox was
low compared to denitrification, with anammox accounting for less than 3% of the total N2 production. The highest relative importance of anammox was found in the sediments of freshwater-dominated marshes, where
anammox approached 3%, whereas anammox was of lesser importance in saline marsh sediments. Increased nitrogen loading, in
the form of nitrate from natural or artificial sources, did not impact the relative importance of anammox, which remained
low in all the nitrogen enriched locations (<1%). 相似文献
18.
Adenosine triphosphate (ATP), particulate organic carbon (POC), pH, temperature, and salinity associated with the water column of several salt marsh creeks were monitored at 5 stations for 8 months. A gradient in mean salinity of 11.5‰ to 32.7‰ was observed in the creeks. No significant correlations (Pearson’s r) could be found among the variables measured at the station with the highest salinity. ATP and POC were found to be positively correlated at all other stations. Salinity was found to be negatively correlated with both ATP and POC only at a station with the second highest mean salinity (28.8‰) and could account for only 45.7‰ of the variation in ATP. The lack of significant correlations between salinity and ATP as well as the inability of salinity to account for a large portion of the variation in ATP suggested that salinity had little relationship to the level of total microbial mass. 相似文献
19.
Lori Zaikowski Kevin T. McDonnell Robert F. Rockwell Fred Rispoli 《Estuaries and Coasts》2008,31(1):85-100
The chemical and biological impacts of anthropogenic physical modifications (i.e., channelization, dredging, bulkhead, and
jetty construction) to tributaries were assessed on New York’s Long Island South Shore Estuary. Water-quality data collected
on Carmans, Patchogue, and Swan Rivers from 1997 to 2005 indicate no significant differences in nutrient levels, temperature,
or pH among the rivers, but significant differences in light transmittance, dissolved oxygen (DO), salinity, and sediments
were observed. Patchogue River (PR) and Swan River (SR) were significantly more saline than Carmans River (CR), PR and SR
had less light transmittance than CR, and both exhibited severe warm season hypoxia. CR was rarely hypoxic and only at the
lower layer of the deepest station in warm seasons. Deep stations on PR had hypoxic readings year round, but the shallower
SR was well-oxygenated at all stations after the fall turnover. There were wide diel and seasonal variations in chlorophyll
a on each river, and measurements were significantly higher at poorly flushed stations. In warm seasons, this often resulted
in hyperventilation with supersaturated DO in the upper water column on sunny days, and suboxic conditions at nights and/or
in deeper layers. PR sediments were anoxic, SR sediments ranged from normal to anoxic, and CR sediments were normal at all
stations. Polyaromatic hydrocarbon concentrations in PR sediments were over three orders of magnitude higher than SR and CR
sediments. Benthic invertebrate assessment of species richness, biotic index, and Ephemeroptera, Plecoptera and Trichoptera
richness indicated that PR was severely impacted, SR ranged from slightly to severely impacted, and CR ranged from non-impacted
to slightly impacted. Diversity and abundance of plankton were comparable on SR and CR, and were significantly higher than
on PR. The data indicate that nutrients do not play a major role in hypoxia in these estuarine tributaries but that physical
forces dominate. The narrow inlets, channelization, and abrupt changes in depth near the inlets of PR and SR foster hypoxic
conditions by inducing salinity stratification that limits vertical mixing and by restricting horizontal water mass exchange
with the bay. The study suggests that other tributaries with such physical modifications should be examined to assess the
temporal and spatial extent of hypoxia. 相似文献
20.
Marshes are important habitats for various life history stages of many fish and invertebrates. Much effort has been directed at restoring marshes, yet it is not clear how fish and invertebrates have responded to marsh restoration. The blue crab,Callinectes sapidus, uses marsh habitats during much of its benthic life. We investigated the response of blue crabs to marsh restoration by comparing crab abundance (catch per unit effort), mean size and size frequency distribution, sex ratio, and molt stages of crabs in recently restored marshes that were former salt hay farms to that of adjacent reference marshes with similar physical characteristics in the mesohaline portion of Delaware Bay. Field sampling occurred monthly (April–November) in 1997 and 1998 using replicate daytime otter trawls in large marsh creeks and weirs in smaller intertidal marsh creeks. Blue crabs were either equal or more abundant, the incidence of molting was in most months similar, and population sex ratios were indistinguishable in restored and reference marshes, suggesting that the restored areas attract crabs and support their growth. Site location had a greater effect on the sex ratio of crabs such that marshes closer to the mouth of the bay contained a higher percentage of adult female crabs. In each annual growing season (April–July), the monthly increase in crab size and, in some months (June–July), the incidence of molting at the restored sites was greater than the reference sites, suggesting that the restored sites may provide areas for enhanced growth of crabs. These results suggest that blue crabs have responded positively to restoration of former salt hay farms in the mesohaline portion of Delaware Bay. 相似文献