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1.
In recent decades, marshes naturally dominated bySpartina spp. have been replaced byPhragmites australis throughout the northeastern United States. We suggest that early in this invasion there was little effect on the fish fauna. As the invasion proceeds, the marsh surface habitat became more altered (i.e., elevated, flattened, reduced water-filled depressions, and reduced standing water), which resulted in a reduction of feeding, reproduction, and nursery function for fishes, especiallyFundulus spp. These potential changes in marsh habitat and function have resulted in numerous attempts to removePhragmites and restoreSpartina spp. To evaluate the response of marsh surface fishes toPhragmites treatment, we examined fish use in the brackish water reaches of Alloway Creek in the Delaware Bay estuary. ReferencePhragmites habitats were compared with referenceSpartina alterniflora-dominated habitats and sites treated (1996–1998) to removePhragmites to restore former vegetation (i.e., restored, now comprised of 100%Spartina). Fish were sampled with an array (n=9 at each site) of shallow pit traps (rectangular glass dishes, 27.5×17.5×3.7 cm). Small individuals (mean=17.5, 5–45 mm TL) dominated all pit trap collections. Fish abundance was highest at the restored (catch per unit effort [CPUE]=2.16) andSpartina (CPUE=0.81) sites with significantly lower values atPhragmites (CPUE=0.05) habitats. Samples were dominated by young-of-the-year mummichog,Fundulus heteroclitus (98% of total fish, n=631). The only other fish species collected was spotfin killifish,Fundulus luciae (2% of total catch, n=14), which was only present in restored andSpartina habitats. These observations suggest that the restored marsh is providing habitat (water-filled depressions on the marsh surface) for young-of-the-yearFundulus spp. These marshes are responding favorably to the restoration based on the much greater abundance of fish in restored versusPhragmites habitats and the overall similarity between restored andSpartina habitats. 相似文献
2.
Much effort has been directed recently at restoring marshes, by the removal of the invasive common reed,Phragmites australis, yet it is not clear how fish and invertebrates have responded either to the invasion ofPhragmites or to marsh restoration. The blue crab,Callinectes sapidus, uses marsh habitats during much of its benthic life. We investigated the response of blue crabs toPhragmites invasion and restoration efforts by comparing crab abundance (catch per unit effort), mean size and size frequency distribution,
sex ratio, and molting of crabs in three physically similar areas differing in marsh vegetation;Spartina-dominated,Phragmites-dominated, and a treated area (Phragmites removed and now dominated bySpartina) in one marsh in the upper portion of Delaware Bay. Field sampling occurred monthly (April to November) from 1999 to 2001
using replicate daytime otter trawls in large marsh creeks. Crabs were categorized by carapace width into recruits (<30 mm),
juveniles (30–115 mm), and adults (>115 mm). Juveniles dominated the system, representing 69.4% of all crabs. Similar monthly
increases in mean size and molting patterns during the growing season (May–August) occurred inSpartina (natural and treated sites) andPhragmites sites suggesting that, subtidal habitats, used for molting, in these areas do not differ. More juveniles in the feeding molt
stage (i.e., intermolt) than in other molt stages and more recruits predominantly in the feeding molt stage than adults were
inSpartina, suggesting differences in the marsh surfaces used as feeding habitats withSpartina being preferred. Sex ratios of each life history stage were skewed towards males, but this was related to the low salinity
of Alloway Creek, rather than marsh surface vegetation. Our results suggest that marsh surface vegetation influences the way
blue crabs use marsh surface habitats, thus restoration efforts focusing on changing vegetation type may have a positive influence
on blue crabs. 相似文献
3.
The invasion ofSpartina marshes by the common reed,Phragmites australis, along the east coast of the United States over the last several decades has been well documented, although we know little about the impact of this invasion on the fish fauna and the few published papers seem contradictory. During 1999–2000 (May–September) we evaluated the fish response to vegetation type (Phragmites australis veersusSpartina alterniflora) by monitoring several aspects of fish early life history (egg deposition, embryonic development, hatching success, and larval and juvenile abundance) in low salinity marshes in the Mullica River in southern New Jersey. The dominant fish species using the marsh surface,Fundulus heteroclitus (93% of total catch, n=996 individuals), reproduced in both vegetation types with eggs deposited in leaf axils near the base of the plant inSpartina and in broken stems ofPhragmites during both years. These eggs also undergo successful embryonic development to hatching in both vegetation types. Larval and juvenile (5–75 mm total length, but 95% < 34 mm TL) abundance of this species is much reduced onPhragmites-dominated (mean CUPE=0.02, n=7 ind) marsh surface relative toSpartina (mean CPUE=2.31). These findings, and similar results for fish abundance in 1997 and 1998, indicate that theSpartima marsh surface is likely essential fish habitat for this species because it provides habitat for larvae and small juveniles, whilePhragmites does not. ThePhragmites invasion in brackish marshes may be having deleterious effects on fish populations and possibly on predators that prey uponF. heteroclitus, and as a result, marsh secondary production. 相似文献
4.
This study investigates the influence ofPhragmites australis (common reed) invasion on the habitat of the resident marsh fish,Fundulus heteroclitus (mummichog) in the Hackensack Meadowlands, New Jersey. These abundant fish play an important role in the transfer of energy
from the marsh surface to adjacent subtidal waters and thus estuarine food webs. The objectives of this 2-yr study (1999 and
2000) were to compare the distribution and abundance of the eggs, larvae, juveniles, and adults of mummichog and their invertebrate
prey inhabitingSpartina alterniflora-dominated marshes withPhragmites-dominated marshes, and to experimentally investigate the influence of marsh surface microtoprography on larval fish abundance
withinPhragmites-dominated marshes. In 2000, we verified that egg deposition does occur inPhragmites-dominated marshes. In both years, the abundance of larvae and small juveniles (4–20 mm TL) inS. alterniflora was significantly greater than inPhragmites-dominated marshes, while larger juveniles and adults (>20 mm TL) were similarly abundant in both habitat types. The overall
abundance of larvae and small juveniles was significantly greater in experimentalPhragmites plots in which microtopography was manipulated to resemble that ofSpartina marshes than inPhragmites control plots. Major groups of invertebrate taxa differed between marsh types with potential prey for larval fish being significantly
more abundant inS. alterniflora marshes.Phragmites-dominated marshes may not provide the most suitable habitat for the early life-history stages of the mummichog. The low abundance
of larvae and small juveniles inPhragmites marshes is likely due to inadequate larval habitat and perhaps decreased prey availability for these early life history stages. 相似文献
5.
The extensive spread ofPhragmites australis throughout brackish marshes on the East Coast of the United States is a major factor governing management and restoration
decisions because it is assumed that biogeochemical functions are altered by the invasion. Microbial activity is important
in providing wetland biogeochemical functions such as carbon and nitrogen cycling, but there is little known about sediment
microbial communities inPhragmites marshes. Microbial populations associated with invasivePhragmites vegetation and with native salt marsh cordgrass,Spartina alterniflora, may differ in the relative abundance of microbial taxa (community structure) and in the ability of this biota to decompose
organic substrates (community biogeochemical function). This study compares sediment microbial communities associated withPhragmites andSpartina vegetation in an undisturbed brackish marsh near Tuckerton, New Jersey (MUL), and in a brackish marsh in the anthropogenically
affected Hackensack meadowlands (SMC). We use phospholipid fatty acid (PLFA) analysis and enzymataic activity to profile sediment
microbial communities associated with both plants in each site. Sediment analyses include bulk density, total organic matter,
and root biomass. PLFA profiles indicate that the microbial communities differ between sites with the undisturbed site exhibiting
greater fatty acid richness (62 PLFA recovered from MUL versus 38 from SMC). Activity of the 5 enzymes analyzed (β-glucosidase,
acid phosphatase, chitobiase, and 2 oxidases) was higher in the undisturbed site. Differences between vegetation species as
measured by Principal Components Analysis were significantly greater at the undisturbed MUL site than at SMC, and patterns
of enzyme activity and PLFAs did not correspond to patterns of root biomass. We suggest that in natural wetland sediments,
macrophyte rhizosphere effects influence the community composition of sediment microbial populations. Physical and chemical
site disturbances may impose limits on these rhizosphere effects, decreasing sediment microbial diversity and potentially,
microbial biogeochemical functions. 相似文献
6.
To test whether invasive Spartina alterniflora marshes were functionally equivalent to native Scirpus mariqueter marshes, the present study used bottomless lift nets (20 m2) during 12 high-tide events from August to October 2008 to compare nekton densities and biomass between the two marsh types
in the Dongtan wetland. A total of eight species of fish, two species of shrimp, and three species of crab were collected.
So-iny mullet Chelon haematocheilus, keeled mullet Liza carinata, Asian freshwater goby Acanthogobius ommaturus, and ridge-tail prawn Exopalaemon carinicauda dominated samples from the two marsh types and accounted for over 90% of the total catch. There were significantly greater
densities and biomass (p < 0.05) of total nekton (all species combined) and two mullets (C. haematocheilus and L. carinata) in S. alterniflora marshes than in S. mariqueter marshes in August 2008, while no significant differences (p > 0.05) between the two marsh types were observed for densities and biomass of any species or total nekton in September and
October 2008. Non-metric multidimensional scaling ordination did not show clear separation of samples between the two marsh
types (r = 0.071, p = 0.159). Furthermore, there were no habitat-specific differences (p > 0.05) in the size distributions of the three numerically dominant species (C. haematocheilus, L. carinata, and A. ommaturus). We concluded that S. alterniflora marshes were utilized by nekton in a fashion similar to their utilization of native S. mariqueter marshes under similar physical conditions. 相似文献
7.
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
8.
Juan M. Jiménez Kazimierz Więski Laurie B. Marczak Chuan-Kai Ho Steven C. Pennings 《Estuaries and Coasts》2012,35(2):475-485
Top–down and bottom–up effects interact to structure communities, especially in salt marshes, which contain strong gradients
in bottom–up drivers such as salinity and nutrients. How omnivorous consumers respond to variation in prey availability and
plant quality is poorly understood. We used a mesocosm experiment to examine how salinity, nutrients, an omnivore (the katydid
Orchelimum fidicinium) and an herbivore (the planthopper Prokelisia spp.) interacted to structure a simplified salt marsh food web based on the marsh grass Spartina alterniflora. Bottom–up effects were strong, with both salinity and nutrients decreasing leaf C/N and increasing Prokelisia abundance. Top–down effects on plants were also strong, with both the herbivore and the omnivore affecting S. alterniflora traits and growth, especially when nutrients or salt were added. In contrast, top–down control by Orchelimum of Prokelisia was independent of bottom–up conditions. Orchelimum grew best on a diet containing both Spartina and Prokelisia, and in contrast to a sympatric omnivorous crab, did not shift to an animal-based diet when prey were present, suggesting
that it is constrained to consume a mixed diet. These results suggest that the trophic effects of omnivores depend on omnivore
behavior, dietary constraints, and ability to suppress lower trophic levels, and that omnivorous katydids may play a previously
unrecognized role in salt marsh food webs. 相似文献
9.
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
10.
Alejandro?D.?Canepuccia Maria?S.?Fanjul Eugenia?Fanjul Florencia?Botto Oscar?O.?Iribarne Consejo Nacional de Investigaciones Científicas y Técnicas Departamento de Biología Universidad Nacional de Mar del Plata Mar del Plata Argentina 《Estuaries and Coasts》2008,31(5):920-930
The role of positive and indirect interactions is often crucial in communities with intense abiotic stress such as salt marshes.
The burrowing crab, Neohelice (=Chasmagnathus) granulata, is the dominant benthic macroinvertebrate of southwest Atlantic marshes (southern Brazil to Northern Argentinean Patagonia),
having strong direct and indirect effects on marsh soil and, in consequence, on marsh vegetation and primary consumers. In
this work, we investigate if this crab indirectly modifies habitat use by the granivorous rodents, Akodon azarae and Oligoryzomys flavescens, by increasing nutrient availability and thus enhancing seed production by the marsh plant Spartina densiflora. The study was conducted at the Mar Chiquita Coastal Lagoon, Argentina (37°32′ S). Rodent frequencies in S. densiflora were positively correlated with crab densities throughout the low and middle marsh. Additionally, the highest quality of
S. densiflora and inflorescence density was recorded at the highest crab densities. Experimental manipulation of crab densities shows that
N. granulata indirectly enhances the performance of S. densiflora (e.g., decreased fiber content and C/N ratios) and increases density of seeds. Moreover, N. granulata also facilitates S. densiflora seed availability to rodents by concentrating them in sediment mound at their burrows entrances. Experimental rodent exclusions
showed that rodent species used S. densiflora seeds, a variable positively related to crab burrow density. Thus, our results show that N. granulata drives the granivorous rodent distribution and the intensity of seeds–rodent interaction trough facilitative and indirect
interactions in marsh community. 相似文献
11.
C. A. Currin S. C. Wainright K. W. Able M. P. Weinstein C. M. Fuller 《Estuaries and Coasts》2003,26(2):495-510
The invasion ofPhragmites australis into tidal marshes formerly dominated bySpartina alterniflora has resulted in considerable interest in the consequences of this invasion for the ecological functions of marsh habitat. We examined the provision of trophic support for a resident marsh fish,Fundulus heteroclitus, in marshes dominated byP. australis, byS. alterniflora, and in restored marshes, using multiple stable isotope analysis. We first evaluated our ability to distinguish among potential primary producers using the multiple stable isotope approach. Within a tidal creek system we found significant marsh and elevation effects on microalgal isotope values, and sufficient variability and overlap in primary producer isotope values to create some difficulty in identifying unique end members. The food webs supportingF. heteroclitus production were examined using dual isotope plots. At both sites, the δ13C values ofF. heteroclitus were clustered over values for benthic microalgae (BMI) and approximately midway between δ13C values ofSpartina andPhragmites. Based on comparisons of fish and primary producer δ13C, δ15N, and δ34S values, and consideration ofF. heteroclitus feeding habits, we conclude that BMI were a significant component of the food web supportingF. heteroclitus in these brackish marshes, especially recently-hatched fish occupying pools on the marsh surface. A 2‰ difference in δ13C betweenFundulus occupying nearly adjacentSpartina andPhragmites marshes may be indicative of relatively less reliance on BMI and greater reliance onPhragmites production inPhragmites-dominated marshes, a conclusion consistent with the reduced BMI biomass found inPhragmites marshes. The mean δ13C value ofF. heteroclitus from restored marshes was intermediate between values of fish from naturally occurringSpartina marshes and areas invaded byPhragmites. We also examined the isotopic evidence for ontogenetic changes in the trophic position of larval and juvenileF. heteroclitus. We found significant positive relationships betweenF. heteroclitus δ15N values and total length, reflective of an increase in trophic position as fish grow.F. heteroclitus δ15N values indicate that these fish are feeding approximately two trophic levels above primary producers. 相似文献
12.
Through their physiological effects on ion, oxygen, and carbon balance, respectively, salinity, sulfide, and prolonged flooding
combine to constrain the invasion and spread ofPhragmites in tidal wetlands. Initial sites of vigorous invasion by seed germination and growth from rhizome fragments appear limited
to sections of marsh where salinity is <10‰, sulfide concentrations are less than 0.1 mM, and flooding frequency is less than
10%. In polyhaline tidal wetlands the invasion sites include the upland fringe and some high marsh creek banks. The zones
of potential invasion tend to be larger in marshes occupying lower-salinity portions of estuaries and in marshes that have
been altered hydrologically. Owing to clonal integration and a positive feedback loop of growth-induced modification of edaphic
soil conditions, however, a greater total area of wetland is susceptible toPhragmites expansion away from sites of establishment. Mature clones have been reported growing in different marshes with salinity up
to 45‰, sulfide concentration up to 1.75 mM, and flooding frequency up to 100%. ForPhragmites establishment and expansion in tidal marshes, windows of opportunity open with microtopographic enhancement of subsurface
drainage patterns, marsh-wide depression of flooding and salinity regimes, and variation in sea level driven by global warming
and lunar nodal cycles. To avoidPhragmites monocultures, tidal wetland creation, restoration, and management must be considered within the context of these different
scales of plant-environment interaction. 相似文献
13.
Quantifying the relative value ofPhragmites australis andSpartina alterniflora habitat is important to evaluate the benefits and risks of different attempts to addressPhragmites expansion on the U.S. eastern seaboard. Two contrasting approaches commonly used to restore tidal marsh habitats invaded
byPhragmites communities involve sprayingPhragmites with herbicide only when its coverage of a particular marsh area is near or close to 100%. Alternatively, after the first
application, herbicide is annually applied on any surviving patches ofPhragmites present in a mosaic of other marsh vegetation. A model is introduced to evaluate the relative habitat value of these control
regimes, here termed the Intermittent and Continuous. Compared to the Intermittent approach, the area of herbicide application
in the Continuous approach is higher in the first 6 yr, but lower the reafter. The cumulative gain in habitat quality after
20 yr in either approach is sensitive to the presumed relative values ofPhragmites versusSpartina habitat, and may even be negative if they are nearly equal. Annual applications of herbicide to patches ofPhragmites appears to generate more habitat value and with less herbicide than occasional applications whenPhragmites cover is at is maximum. 相似文献
14.
Oysters can create reefs that provide habitat for associated species resulting in elevated resident abundances, lower mortality
rates, and increased growth and survivorship compared to other estuarine habitats. However, there is a need to quantify trophic
relationships and transfer at created oyster reefs to provide a better understanding of their potential in creating suitable
nekton habitat. Stable isotope analyses (δ13C and δ15N) were conducted to examine the organic matter sources and potential energy flow pathways at a created intertidal oyster
(Crassostrea ariakensis; hereinafter, oyster) reef and adjacent salt marsh in the Yangtze River estuary, China. The δ13C values of most reef-associated species (22 of 37) were intermediate between those of suspended particle organic matter (POM)
and benthic microalgae (BMI), indicating that both POM and BMI are the major organic matter sources at the created oyster
reef. The sessile and motile macrofauna colonizing the reef make up the main prey of transient nekton (e.g., spotted sea bass,
Asian paddle crab, and green mud crab), thus suggesting that the associated community was most important in supporting higher
trophic levels as opposed to the direct dietary subsidy of oysters. The created oyster reef consistently supported higher
trophic levels than the adjacent salt marsh habitat due to the dominance of secondary consumers. These results indicate that
through the provision of habitat for associated species, created oyster reefs provide suitable habitat and support a higher
average trophic level than adjacent salt marsh in the Yangtze River estuary. 相似文献
15.
The mummichog,Fundulus heteroclitus, is one of the most important macrofaunal components of salt marsh surfaces and an important link to subtidal areas of the
adjacent estuary along the east coast of the U.S. We estimated growth, population size, and production of the mummichog in
a restored marsh in order to improve our understanding of the role of this resident fish and to evaluate the success of the
restoration. The restored marsh, covering 234 ha, was a former salt hay farm located in the mesohaline portion of Delaware
Bay that was restored to tidal influence in August 1996. We separated the mummichog population into two components based on
life history stage and summer habitat use patterns. One component, consisting of adults and large young-of-the-year (YOY),
exhibited tidal movements to and from the marsh surface and the subtidal creeks. These were examined with an intensive mark
and recapture program using coded wire tags. Another component, consisting of small YOY, remained on the marsh surface throughout
the tidal cycle. Throw traps were used to sample these small YOY. The mean annual population density of adults and large YOY
for the entire marsh was approximately 1.2 fish m−2 and mean monthly density peaked at 2.9 fish m−2. The mean annual density of small YOY on the marsh surface was 15.1 fish m−2 and mean monthly density peaked at 41.4 fish m−2. Size and season influenced the growth rate of individual fish and instantaneous growth rates ranged from 0.03 to 2.26 mo−1. Total annual mummichog production was estimated to be 8.37 g dw m−2 yr−1, with adults and large YOY contributing 28.4% (2.38 g dw m−2 yr−1) and small YOY on the marsh surface contributing 71.6% (5.99 g dw m−2 yr−1). The seasonal use and population densities were comparable to previous studies in natural marshes while growth and production
of mummichog in this restored marsh appeared to be higher. Coupled with the results of other studies on the feeding, movement,
and habitat use of this species in this restored marsh, the species has responded well to the restoration. 相似文献
16.
Although top-down control of plant growth has been shown in a variety of marine systems, it is widely thought to be unimportant in salt marshes. Recent caging experiments in Virginia and Georgia have challenged this notion and shown that the dominant marsh grazer (the periwinkle,Littoraria irrorata) not only suppresses plant growth, but can denude marsh substrate at high densities. In these same marshes, our field observations suggest that the black-clawed mud crab,Panopeus herbstii, is an abundant and potentially important top-down determinant of periwinkle density. No studies have quantitatively examinedPanopeus distribution or trophic interactions in marsh systems, and its potential impacts on community structure remained unexplored. We investigated distribution and feeding habits ofPanopeus in eight salt marshes along the Mid-Atlantic seashore (Delaware-North Carolina). We found that mud crabs were abundant in tall (4–82 ind m?2), intermediate (0–15 ind m?2), and short-form (0–5 ind m?2)Spartina alterniflora zones in all marshes and that crab densities were negatively correlated with tidal height and positively correlated with bivalve density. Excavation of crab lairs r?utinely produced shells of plant-grazing snails (up to 36 lair?1) and bivalves. Lab experiments confirmed that mud crabs readily consume these abundant marsh molluscs. To experimentally examine potential community effects of observed predation patterns, we manipulated crab and periwinkle densities in a 1-mo field experiment. Results showed thatPanopeus can suppress gastropod abundance and that predation rates increase with increasing snail density. In turn, crab suppression of snail density reduces grazing intensity on salt marsh cordgrass, suggesting presence of a trophic cascade. These results indicate that this previously under-appreciated consumer is an important and indirect determinant of community structure and contribute to a growing body of evidence challenging the long-standing notion that consumers play a minor role in regulating marsh plant growth. 相似文献
17.
Anthony J. Rietl John A. Nyman Charles W. Lindau Colin R. Jackson 《Estuaries and Coasts》2017,40(3):832-841
Understanding methane emissions from natural sources is becoming increasingly important with future climactic uncertainty. Wetlands are the single largest natural source of methane; however, little attention has been given to how biota and interactions between aboveground and belowground communities may affect methane emission rates in these systems. To investigate the effects of vegetative disturbance and belowground biogeochemical alterations induced by biota on methane emissions in situ, we manipulated densities of Littoraria irrorata (marsh periwinkle snails) and Geukensia granosissima (gulf ribbed mussels) inside fenced enclosures within a Spartina alterniflora salt marsh and measured methane emissions and sediment extracellular enzyme activity (phosphatase, β-glucosidase, cellobiohydrolase, N-acetyl-β-D-glucosaminidase, peroxidase, and phenol oxidase) over the course of a year. Changes in snail density did not have an effect on methane emission; however, increased densities of ribbed mussels significantly increased the emission of methane. Sediment extracellular enzyme activities for phosphatase, cellobiohydrolase, N-acetyl-β-D-glucosaminidase, and phenol oxidase were correlated to methane emission, and none of the enzymes assayed were affected by the snail and mussel density treatments. While methane emissions from salt marsh ecosystems are lower than those from freshwater systems, the high degree of variability in emission rates and the potential for interactions with naturally occurring biota that increase emissions warrant further investigations into salt marsh methane dynamics. 相似文献
18.
Ribbed mussels (Geukensia demissa) help form the basis of highly productive salt marshes along the Atlantic coast of North America, in southern New England, and further south. Little is known about their ecology and reproductive biology at more northern latitudes (Maritime Canada; >43o N). As a step in determining the sustainability of ribbed mussel populations near the northern limit of their range (Northumberland Strait, Gulf of St. Lawrence, Canada), gametogenesis and spawning were monitored over 3 years (May–August 2012, June–November 2014, and April–October 2015) at four sites spanning ~100 km of coastline. These sites are typically ice-covered from mid-December to March or April. The onset of gametogenesis was later, the reproductive stages on any given date were more varied, and the reproductive season was shorter than for southern populations of ribbed mussels. Oocyte density and size did not vary among sites, indicating similar site-level processes, but did vary among years. Oocyte density and size varied greatly among mussels at a given site, and within a single gonad. This highlights the importance of individual variability, perhaps related to mussel location within a marsh, and the effects of nutrients and temperature on gonads. Accounting for the individual-level variability, reproductive output was estimated at ~105 oocytes per ripe female mussel, which is within the fecundity estimates for other marine bivalve broadcast spawners. 相似文献
19.
Summary The complexation of aluminium(III) and silicon(IV) was studied in a simplified seawater medium (0.6 M Na(Cl)) at 25 °C. The
measurements were performed as potentiometric titrations using a hydrogen electrode with OH
− ions being generated coulometrically. The total concentrations of Si(IV) and Al(III) respectively [Si
tot
] and [Al
t
ot], and −log[H
+] were varied within the limits 0.3 < [Si
tot
] < 2.5 mM, 0.5 < [Al
tot
] < 2.6 mM, and 2 ≤ -log[H
+] ≤ 4.2. Within these ranges of concentration, evidence is given for the formation of an AlSiO(OH)
3
2+
complex with a formation constant log β1,1-1 = −2.75 ± 0.1 defined by the reaction
Al
3++Si (OH)4 ↔ AlOSi(OH)
3
2+
+H
+
An extrapolation of this value to I=0 gives log β1,1-1 = −2.30. The calculated value of log K (Al
3++SiO(OH)
3
−
↔ AlOSi(OH)
3
2+
) = 6.72 (I=0.6 M) can be compared with corresponding constants for the formation of AlF
2+ and AlOH
2+ , which are equal to 6.16 and 8.20. Obviously, the stability of these Al(III) complexes decreases within the series OH
−>SiO(OH)
3
−
> F
− 相似文献
20.
The stable isotope signatures of marine transient and resident nekton were used to investigate trophic linkages between primary
producers, marsh macrophytes, phytoplankton, benthic microalgae, and consumers within the Delaware Bay. A whole estuary approach
was used to compare the flux of nutrients from primary producers to juvenile weakfish (Cynoscion regalis), bay anchovy (Anchoa mitchilli), and white perch (Morone americana) in open waters of the lower and upper Bay and adjacent salt marshes dominated by eitherSpartina alterniflora orPhragmites australis. Our results suggest that trophic linkages vary significantly along the salinity gradient, reflecting the transition fromSpartina toPhragmites-dominated marshes, and secondarily, in a marsh to open water (offshore) direction at a given salinity. Superimposed on this
pattern was a gradient in the proximate use of organic matter that depended on life history traits of each species ranging
from pelagic to benthic in the order bay anchovy > weakfish > white perch. 相似文献