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1.
In recent years the pace of exotic species introduction and invasion has accelerated, particularly in estuaries and wetlands.
Species invasions may affect coastal ecosystems in many ways. Alteration of sedimentary environments, through structure formation
and burrowing, has particularly dramatic effects on coastal habitats. This study examines modification of channel bank and
marsh edge habitat by the burrowing Australasian isopod Sphaeroma quoyanum Milne Edwards, in created and natural salt marshes of San Diego Bay and San Francisco Bay. Abundance and distribution patterns
of this isopod species, its relationships with habitat characteristics, and its effects on sediment properties and bank erosion
were examined seasonally, and in several marsh microhabitats. Mean isopod densities were 1541 and 2936 individuals per 0.25 m2 in San Francisco Bay, and 361 and 1153 individuals per 0.25 m2 in San Diego Bay study sites during December and July 1998, respectively. This isopod forms dense, anastomosing burrow networks.
S. quoyanum densities did not differ as a function of location within creeks or location in natural versus created marshes. Burrows,
which are on average 6 mm wide and 2 cm long, were associated with firm sediments containing high detrital biomass. Although
erosion is a natural process along salt marsh banks, enclosure experiments demonstrated that isopod activities can enhance
sediment loss from banks. In areas infested with S. quoyanum, losses may exceed 100 cm of marsh edge per year. The effects of habitat alteration by this invading species are likely to
increase in severity in the coastal zone as these ecosystems become degraded.
Received: 30 March 2000 / Accepted: 21 September 2000 相似文献
2.
M. R. Plante-Cuny C. Salen-Picard C. Grenz R. Plante E. Alliot C. Barranguet 《Marine Biology》1993,117(2):355-366
Effects of an experimental pollution by neogenous and fossil organic matter on microphyto- and macrozoobenthic communities were studied in situ over a 1 yr period (July 1989 to May 1990) in a shallow microtidal bay (Gulf of Fos, south coast of France). Three experimental enclosures of 1 m2 non-defaunated sediments were covered with 1 cm of polluted defaunated sediments. The sediment in one enclosure contained natural biodeposits with a high organic matter content (BD), that in a second enclosure contained Arabian light crude oil (BAL), and the sediment in the third enclosure contained diesel oil-based cuttings (CUT). Pollution by contaminants did not prevent microphytobenthos from colouizing sediments. Population changes over time were quite similar in all enclosures, except in CUT, where a four times higher chlorophyll a content appeared to be related to a decreased number of grazers and consequently lower grazing rates of animals. Toxicity to the fauna was immediate in the case of BAL and occurred within 3 mo at CUT. Opportunistic species settled in all contaminated sediments; this occurred quite rapidly in BD and BAL which recovered within 3 mo to levels comparable with control sediments. In CUT, natural populations had not recovered after 1 yr, whereas a quasi-monospecific population of Capitella capitata was still present. During the first 3 mo, the oxygen demand of the sediment was higher in oil-contaminated sediments than in controls. On the whole, the changes in fluxes and organism assemblages in our weakly tidal area appear to be consistent with other findings in macrotidal seas. 相似文献
3.
The response of an estuarine macrobenthic community to different intensities of physical disturbance was examined using comparable
field and mesocosm experiments. In the field study, areas of sediment (2500 cm2) were disturbed by surface-raking at a range of disturbance intensities: no disturbance, once every 2 mo, once every month,
once every 2 wk, once or three times every week. These disturbance regimes were also imposed on buckets of sediment (855 cm2) collected from the field study site and maintained within a mesocosm system. In the univariate data analysis, neither field
nor mesocosm communities displayed any trends in relation to the frequency of disturbance. Diversity indices were generally
reduced in the mesocosm communities compared with the field communities. Multivariate analysis indicated significant differences
between the field communities subjected to the most intense disturbance and those communities disturbed every ±2 wk or less.
These differences were attributed to reductions in the five numerically dominant species in the high- disturbance treatments.
More statistically significant differences were observed between the different disturbance intensities in the mesocosm experiment
than in the field study. The implications of differences between field and mesocosm experiments results are discussed.
Received: 14 June 1999 / Accepted: 3 December 1999 相似文献
4.
Standing crop, population size, and species diversity of the macrobenthic organisms in an estuarine channel were studied before and after dredging. A new suction-corer which sampled an area 0.1 m2 to a depth of 30 cm was used in order to insure the inclusion of large, deep-dwelling animals. Eleven months after dredging, biomass and number of species and specimens had not recovered to pre-dredging levels. Colonization began with relatively large, swiftly moving forms such as the errant polychaete Nereis succinea and the crab Neopanope texana sayi. Stations in silt and mud regions recovered more slowly than those in sandier sediments. Most of the dominant and subdominant species had not recovered 11 months after dredging, and the previously abundant polychaetes Notomastus latericeus and Clymenella torquata had virtually disappeared. Only relatively uncommon lamellibranchs such as Tellina agilis, Lyonsia hyalina and Mulinia lateralis increased after dredging. Distribution of sediment types changed as the result of modified tidal velocities in the channel. Mud and silt were removed by the dredge, exposing the sand underneath, and sandy stations became muddier as the result of lowered current velocities. Marked changes in species composition reflected this change in sediment character. Eleven months after dredging no evidence of succession was found, but colonization had begun. Values of all three parameters studied were reduced to small fractions of pre-dredging levels, although species diversity in sandy sediments exceeded pre-dredging levels. 相似文献
5.
Colonisation of various types of sediment by estuarine nematodes via lateral infaunal migration: a laboratory study 总被引:1,自引:0,他引:1
A small-scale laboratory study was conducted to assess the capability of nematode species collected at an intertidal mudflat to migrate laterally into defaunated sediment by using an experimental design that excluded hydrodynamic influences. The colonisation of native mud, non-native sand and two types of non-native mud-sand mixture was monitored over a period of 2 months. Results revealed that the composition of source and colonist communities differed significantly between treatments and over time. Within the first 2 weeks of the experiment, dominance patterns in the control sediments were most similar to the sand treatment, indicating that the majority of species were able to migrate easily into non-native sandy sediment. Over the course of the experiment, colonist communities in the muddy sediments became more similar to the control microcosms, whereas the structure of the sand assemblage became increasingly dissimilar to that of the source community. The temporal patterns observed might be related to factors associated with sediment granulometry, such as the availability of appropriate food sources. The outcome of this study demonstrated that the colonisation of defaunated sediment via lateral interstitial migration is a directed, species-specific process that can lead to the establishment of colonist communities that are significantly different from source communities.Communicated by J.P. Thorpe, Port Erin 相似文献
6.
Deposit-feeders can respond to seasonal fluctuations in food concentration both functionally (e.g. by adjusting feeding rates)
and physiologically (e.g. by changing the concentration of bacteriolytic agents in gut fluids). Laboratory feeding experiments
were carried out (11 to 21 July 1997) with the arenicolid polychaete worm Abarenicola pacifica (Healy and Wells). Objectives were to test for separate and interactive effects of sediment food concentration and temperature
(6, 11, and 16 °C) on deposit-feeder functional (feeding rates) and physiological (bacteriolytic activity of gut fluids) responses.
Food concentration was varied experimentally using sieved (1 mm) natural sediments (Md φ=2.00; 0.6% organic) mixed with combusted
(500 °C, 8 h) sediments for final concentrations of 25, 50, and 100% natural sediment. Sediment food quality was measured
as: (1) bioavailable amino acids (EHAA), (2) chlorophyll a (chl a), and (3) bacterial abundance. Feeding rates were inferred from egestion rates (ER, g h−1) and analyzed with respect to worm size. Bacteriolytic activity of midgut fluids was assayed turbidimetrically against two
bacterial isolates, after worms had fed on experimental sediments for 15 d. Temperature and food concentration both significantly
affected feeding rates, with maxima occurring at 50 and 100% natural sediment mixtures, and at high (16 °C) temperature. ER
was positively, but not significantly correlated with EHAA and chl a; a positive, significant correlation was detected between ER and sediment bacterial abundance. Overall, functional responses
agreed with earlier compensatory intake models for deposit-feeders. However, the size and direction of these responses was
temperature-sensitive, suggesting that these models need to be adjusted for changes in absorption rates. No effects of ambient
temperature or food concentration on bacteriolytic rates were observed, possibly due to compensatory mechanisms or the presence
of multiple bacteriolytic agents in gut fluids.
Received: 28 June 1999 / Accepted: 14 March 2000 相似文献
7.
Mudball-building cirratulid polychaetes have been described previously only from the southern California margin. During a
study of oxygen minimum-zone benthos in fall 1994, we observed dense aggregations of agglutinated mudballs at 840 to 875 m
on the Oman margin in the northwest Arabian Sea. These were inhabited, and probably constructed, by a cirratulid polychaete
species in the genus Monticellina. The mudballs were cigar-shaped, 4.5 to 25 mm long, and positioned vertically so as to protrude several millimeters above
the sediment–water interface. Total mudball densities were ∼16 000 m−2. Occupied mudballs occurred at densities of 2 112 m−2; 89% were in the uppermost 2 cm of sediment, and no occupied mudballs were found below 10 cm. Organisms other than the cirratulid
were present on 1.7% of the mudballs examined, and included epizoic polychaetes, agglutinated and calcareous Foraminifera.
Various polychaetes, a nemertean and nematodes were found inside tests. Mudball abundance exhibited positive associations
with densities of several paraonid polychaete species, and with densities of burrowing and subsurface-deposit-feeding polychaetes.
Negative associations were observed between mudballs and three tube-building taxa (two polychaetes and an amphipod). Mudball-inhabiting
cirratulids are abundant in at least two low-oxygen, margin settings. We expect further sampling of bathyal environments to
yield additional systems in which cirratulid mudballs are common. Such observations are valuable because mudballs appear to
represent a significant source of heterogeneity that can influence macrofaunal community structure in deep-sea sediments.
Received: 15 January 1997 / Accepted: 30 January 1997 相似文献
8.
Polychaetes belonging to the genus Capitella are often present in high numbers in organic-rich sediments polluted with, e.g., oil components, and Capitella spp. may have a great impact on the biogeochemistry of these sediments. We examined the influence of Capitella sp. I on microbial activity in an organic-rich marine sediment contaminated with the polycyclic aromatic hydrocarbon, fluoranthene.
Capitella sp. I were added to microcosms (10 000 ind m−2) and the impact of a pulse-sedimentation of fluoranthene-contaminated sediment (3 mm layer) was studied for a period of 12
d after sedimentation. The sediment oxygen uptake and total sediment metabolism (TCO2 production) increased in cores with worms (71 to 131%), whereas the anaerobic activity, measured as sulfate reduction rate
12 d after sedimentation, was lower compared to cores without worms. The effect of fluoranthene on sulfate reduction was most
pronounced in the presence of worms, with a 34% reduction versus 16% in cores without worms. The reduced sulfur pools in cores
with worms were smaller than in cores without worms, suggesting that the reduced anaerobic activity was caused by increased
oxidation of the sediment, which may favor O2 and other electron-acceptors (e.g. NO3
−, Fe3+, Mn4+) in organic matter decomposition. The sediment oxygen uptake and TCO2 production did not show significant changes due to fluoranthene treatment, indicating that these parameters were either less
sensitive to fluoranthene stress or recovered more rapidly (i.e. within 48 h) than sulfate reduction rates. Bioturbation by
Capitella sp. I altered the depth profile of fluoranthene such that fluoranthene was found in deeper sediment layers (down to 2 cm)
where diffusional loss and microbial breakdown probably are reduced relative to surface layers. In cores without worms, fluoranthene
was found down to 1 cm, with 75% remaining in the upper 5 mm.
Received: 5 December 1996 / Accepted: 11 February 1997 相似文献
9.
Nuria Méndez Inez Linke-Gamenick Valery E. Forbes Donald J. Baird 《Marine Biology》2001,138(2):311-319
The effects of the widespread polycyclic aromatic hydrocarbon (PAH) fluoranthene on sediment-processing rates in the infaunal
polychaete Capitella spp. were investigated by comparing five populations of this deposit-feeding species complex: Capitella sp. I from New York, USA; Capitella sp. M from Milos, Greece; Capitella sp. S from Sylt, Germany; and two unidentified Capitella populations from salmon farm sediments –Capitella population K from Kilmelford, Scotland and Capitella population C from Cranford, Ireland. Replicate worms from each strain were exposed to 0, 10, and 95 μg (g dry wt sediment)−1 fluoranthene (=μg/g fluoranthene) for a period of 16 days. Initial and final wet and dry weights (mg) of worms and worm-specific
growth rates (WSGRs) were calculated. Sediment processing was measured as the sum of the total dry weight of pellets produced
during the experiment, and we estimated size-specific processing rates (SSPRs) as a measure of sediment processed per mg worm
dry weight per day. The five populations of Capitella spp. differed significantly in body size, WSGR, and sediment-processing rates. Capitella sp. I grew faster than all of the other populations. Capitella population C and Capitella population K from fish farm sediments, with the largest body lengths (up to 52.0 ± 27.2 mm), had the highest processing rates,
whereas the small Capitella sp. S (up to 17.1 ± 5.6 mm) had the lowest. There were also significant differences in SSPR among populations with Capitella sp. I having a higher SSPR (about 12 × body wt/day) than Capitella population C (about 5 × body wt/day) and Capitella population K (3 × body wt/day). The fluoranthene concentrations used in the present study, while representing moderately
to highly contaminated conditions, had only marginal effects on sediment-processing and growth rates of all of the Capitella populations examined. Processing of contaminated sediment by Capitella spp. may be important in the remediation of PAH-contaminated sediment.
Received: 16 January 2000 / Accepted: 28 August 2000 相似文献
10.
Temporal fluctuations of species composition and abundance of fish juveniles in the National Park Kornati were studied over
12 months from January to December 1992. A total of 40 168 individuals, representing 24 families and 69 species, were collected
using a 50 m long beach seine. The community was dominated numerically by a few species: Atherina hepsetus (45.90%), Sarpa salpa (21.21%), Diplodus vulgaris (10.49%), and Symphodus ocellatus (6.98%), constituting over 84.58% of the total catch. Similarity between patterns in the abundance of the 17 most common
species were examined using correlation matrix-based principal component analysis. Results were compared to the abiotic factors
leading to the conclusion that only a low amount of variation in the abundance field can be explained by temperature, salinity
and dissolved oxygen.
Received: 23 March 1997 / Accepted: 11 April 1997 相似文献
11.
Accurate determination of diet is important in ecological studies. Many macrobenthic predators fragment their prey so finely
that identification of component organisms is difficult. Knowledge of the food available to masticatory predators such as
lobsters can help in determining potential prey and enhance the accuracy of dietary assessments. With SCUBA divers limited
by depth and submersion time, benthic analyses are becoming increasingly reliant on camera systems. Here, based on paired
samples, we assess the relative merits of using removal-sampling by divers versus monochrome video photography to determine
the prey spectrum available to macrobenthic predators. We also relate the results to the gut contents of rock lobsters (Jasus lalandii) that were collected simultaneously. Diver samples took on average four times longer to collect and process than video-image
samples. No significant differences were evident between the number of species identified in diver samples and video-image
samples (n = 21 paired samples, Student's t = 0.233, P > 0.1), although an analysis of similarity (ANOSIM) test revealed that the results obtained from the two sampling methods
were significantly different in terms of species composition (global R = 0.203, P < 0.01). Cluster analysis based on Bray–Curtis similarity to compare diver and video-image samples revealed four clusters
of samples with <35% similarity, confirming that the two techniques do sample different assemblages of species. Video images
detected and allowed identification of all species of prey recorded in the rock lobsters' stomach contents, probably because
rock lobsters prey mainly on relatively large prey which are readily detected by video. Diver-sampling underestimated or failed
to detect two important prey types, namely small barnacles and encrusting coralline algae. We concluded that the camera system
employed was adequate for assessing the prey assemblages available to macrobenthic predators such as lobsters, and that it
was considerably more economical than using divers.
Received: 10 September 1998 / Accepted: 6 May 1999 相似文献
12.
J. Gilmour 《Marine Biology》1999,135(3):451-462
Laboratory and field experiments were used to determine whether high (≃100 mg l−1), low (≃50 mg l−1) and control (≃0 mg l−1) levels of suspended sediment affected fertilisation, larval survival, and larval settlement in the scleractinian coral Acropora digitifera (Dana, 1846). Both high- and low-sediment treatments significantly decreased fertilisation, but post-fertilisation embryonic
development was not inhibited by suspended sediments. Larval survival and larval settlement were significantly reduced in
high- and low-sediment treatments. No difference was found between high- and low-sediment treatments in any of the three post-spawning
processes investigated, suggesting that they are susceptible to sediment concentrations which are not exceptionally high even
under natural conditions (>50 mg l−1). The introduction of an additional stress in the form of high levels of suspended sediments coupled with naturally high
variability in recruitment may have a considerable effect on the successful supply and settlement of coral larvae to a reef.
Given that many coral communities are open reproductive systems, the consequences of disturbance events are not likely to
be restricted to the impact area. Recruitment to a population may be reduced significantly in the presence of high levels
of suspended sediments because of effects on larval survival and settlement. Recruitment of larvae to adjacent populations
may also be affected due to a decreased fertilisation success and potential increases in mortality of larvae passing through
the affected site.
Received: 13 August 1998 / Accepted: 22 July 1999 相似文献
13.
The role of ambient and enhanced ultraviolet-B radiation (UVB; 280 to 315 nm) in a natural sand-associated microbenthic community
was studied in a 3-week experiment by incubating intact sediment cores from a shallow bay in an outdoor flow-through system
with 27 aquaria. After sampling of initial cores, the remaining cores (one per aquarium) were given one of three treatments:
no, ambient, and moderately enhanced UVB, and sampled, nine at a time, after 5, 12, and 19 d. The response of the community
was studied by analysing algal and meiofaunal composition and biomass, chlorophyll a content, composition of pigments and fatty acids, and content of UV-absorbing compounds (state variables), as well as carbon
fixation and allocation, and bacterial productivity (rate variables). Among rate variables, significant effects of UVB-treatments
were found for carbon fixation and allocation, while bacterial productivity was not affected. For state variables, a significant
response was observed for the composition of microalgae and fatty acids, and for chlorophyll a content. The effect of treatments was mainly observed as differences in development with time (two-way analysis of variance,
treatment × time interaction). Towards the end of the experiment, the no-UVB treatment most often differed from one or both
of the two treatments with UVB exposure, the latter showing lower values. There were marked successional changes in the community,
irrespective of treatment. The microalgal community changed from being dominated by coccoid cyanobacteria and epipsammic diatoms
to a dominance of epipelic diatoms and filamentous cyanobacteria. The pattern of carbon allocation, as well as an increased
C/N ratio of the sediment, suggested limitation of growth, perhaps by nutrients, at the end of the experiment. This may possibly
have acted synergistically with UVB exposure to create the treatment effects. The new knowledge gained from our experiment
is that ambient UVB can exert a stress on the function of sand-associated microbenthic communities in shallow waters and that
this effect coincides with structural differences in the community. More experiments in natural or semi-natural systems are
needed to allow better prediction of microbenthic community-level responses to UVB.
Received: 11 November 1997 / Accepted: 12 June 1998 相似文献
14.
Abundance and temporal distribution of viable (able to germinate) resting stage cells of planktonic diatoms in bottom sediments
have been investigated almost monthly during 1989 to 1992 in Hiroshima Bay, western part of Seto Inland Sea, Japan. The abundance
of viable resting stages in bottom sediments was enumerated with the extinction dilution method (most probable number method,
MPN). In bottom sediments of Hiroshima Bay, dominantly distributed species and/ or genera of the diatom resting stages were
Skeletonema costatum, Chaetoceros spp. and Thalassiosira spp. Viable resting stages of these diatoms were densely distributed on the orders of 103 to 106 (MPN g−1 wet sediments), and persisted in bottom sediments throughout the investigation period. Conversely, vegetative cells of these
diatoms fluctuated remarkably in the water column and disappeared sporadically. Survival of the resting stages in a collected
sediment sample was also determined with the MPN method, at different storage temperatures (5, 10, 15, 20, 25 °C). The survival
test demonstrated that the diatom resting stages could survive in the dark for several months or years in sediments. Resting
stages survived longer at the lower storage temperature, and the order of longevity was consistent within three diatoms (Chaetoceros spp. > Thalassiosira spp. > S. costatum) at each storage temperature. The present study suggests that these diatom resting stages in the coastal bottom sediments
could serve as a “seed bank”, analogous to those of terrestrial plants. The seed bank would ensure the survival of diatoms
within highly fluctuating coastal environments, while it would also be the source of sporadic and autochthonous diatom blooms
in coastal waters.
Received: 29 November 1996 / Accepted: 16 December 1996 相似文献
15.
The distribution and enrichment of selected trace metals (Cd, Cr, Cu, Ni, Pb, Sn, Zn) in benthic sediments of the Southport
Broadwater, a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia, was
studied with the objective of assessing the extent and degree of sediment contamination. Sediment samples from the 0–10 cm
and 10–20 cm depth intervals of 32 sites within the Southport Broadwater and surrounding residential canals were analysed
for particle size distribution, pH, organic C and ‘near-total’ major (Al, Ca, Fe, Mn) and trace (Cd, Cr, Cu, Ni, Pb, Sn, Zn)
metal contents. Sediment contamination for each trace metal was assessed by (1) comparison with Australian sediment quality
guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical normalisation
against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, the results indicate that submerged
sediments in the study area are not presently enriched with Cd, Cr or Ni, with the spatial distribution of these metals being
very well explained by the abundance of alumino-silicate clay minerals. However, several sites were strongly enriched with
Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The study indicates
that several varying approaches are needed for a satisfactory assessment of contaminant enrichment in estuarine sediments. 相似文献
16.
Effects of physical disturbance on nematode communities in sand and mud: a microcosm experiment 总被引:1,自引:0,他引:1
A microcosm experiment was carried out to evaluate the effects of continuous and spasmodic physical disturbance of differing
frequency on the structure of nematode communities of intertidal sand and mud. There was a marked, characteristic change in
abundance and diversity for both sediment types. In the sand microcosms, the majority of univariate measures of community
structure, including species diversity, were lowest in the sediments subjected to a high frequency of disturbance. For the mud microcosms, most univariate measures reached their highest values in the treatments
with an intermediate frequency of disturbance and were lower in treatments subjected to both higher and lower frequencies. Multivariate ordinations
for both nematode assemblages showed a clear separation of undisturbed controls and disturbed treatments, but only for the
muddy sediment was there a graded change in community composition with increasing frequency of disturbance. These results
confirmed our a priori expectation that nematode assemblages from mobile sandy sediments would be more resilient to physical
disturbance than those from sheltered muds, and these observations are considered in the context of Connell's intermediate
disturbance hypothesis.
Received: 7 May 1997 / Accepted: 10 October 1997 相似文献
17.
In-situ manipulative experiments were conducted over a 3-month period (May–August 1980) to examine the rate at which meiobenthos colonizes oiled and untreated azoic fine sands at a shallow subtidal site in the lower York River, Virginia. Three concentrations of fresh Prudhoe Bay crude oil were added to sediments: 100, 2 500 and 10000 mg oil kg-1 dry wt sediment. Untreated azoic and natural sediments served as controls. Within 16 d, meiofauna densities in all treatments were comparable to natural populations in surface oxidized sediments, but densities fluctuated greatly during the remainder of the sampling period. Nematodes slowly colonized the subsurface anoxic sediments below the redox potential discontinuity (RPD); some less common species did not significantly recover below the RPD in the two more heavily oiled treatments. Analysis of nematode community composition by reciprocal averaging ordination and numerical classification revealed generally lower abundances, but no distinct differences, in species composition in the oiled substrates as compared to untreated and natural community controls. Ordination of sequential samples suggested that the nematode species assemblages in the untreated controls fully recovered from these small-scale disturbances by 90 d. Life history characteritics and frequent tidal transport combine to make estuarine meiobenthos highly resilient following disturbance. Contrary to prior recolonization studies, a successional sequence was found for the colonizing nematodes which may be analogous to models of macrobenthic colonization (e.g. McCall, 1975). The comesomatid nematode Sabatieria pulchra, which is frequently dominant in polluted sediments, colonized relatively late in the experiment. Consequently, stress resistance and resilience may not be as coincident in meiofauna as in macrofauna because of differences in factors affecting their dispersal. 相似文献
18.
Most studies of spatial patterns of invertebrates in soft sediments have concentrated on populations of individual species.
Those that examined patterns in communities have tended to employ categorical analytical techniques. Using macrofaunal abundance
data from van Veen grab samples collected 20 to 100 m apart in known spatial arrangements from Scottish sea-lochs, the relationships
between patterns in macrobenthic species composition and distances between samples were explored using matrix correlations
in a non-parametric framework. Using a simple definition of spatial structure, i.e. that intersample distances are monotonically
correlated with intersample species-similarity, spatial structure at each of seven stations was assessed using non-parametric
Mantel tests based on rank-correlations. Changes in community structure were positively correlated with distance at all sites
in Loch Etive, on both current-swept muddy sands and soft deep muds. Different components of the macrobenthos contributed
to spatial pattern at each site. Simple spatial structure was also detectable at a muddy-sand site in Loch Creran, but neither
on soft mud, nor at the soft mud site in the Firth of Lorne. The concept of rank-correlograms was introduced. These were used
to examine the extent and form of spatial structure in different components of the macrobenthos at each site. Relationships
between similarity and distance were neither simple nor consistent. Results were compared to previous studies which used the
same data, and it was concluded that studies carried out at a particular scale, or on a particular component of the benthos,
are unlikely to be successful in predicting spatial relationships at other scales or for other components of the benthos.
Correlational rather than categorical analyses are recommended for exploratory studies of spatial relationships in the benthos.
Analyses of the spatial structure at these seven sea-loch sites suggests that by ensuring that samples are at least 40 m apart
an investigator is unlikely to underestimate variability or otherwise invalidate statistical analyses based on the use of
the samples as replicates. Spacing samples up to 100 m apart may increase variability estimates, further reducing the chance
of concluding that a difference exists when one does not.
Received: 4 May 1999 / Accepted: 8 March 2000 相似文献
19.
Relationship between depth, sediment, latitude, and the structure of benthic infaunal assemblages on the mainland shelf of southern California 总被引:2,自引:0,他引:2
Mary Bergen Stephen B. Weisberg Robert W. Smith Donald B. Cadien Ann Dalkey David E. Montagne Janet K. Stull Ronald G. Velarde J. Ananda Ranasinghe 《Marine Biology》2001,138(3):637-647
A regional benthic survey was conducted in 1994, and the data were used to assess the relationship among three habitat factors
(depth, sediment grain size, and latitude) and the distribution of benthic infaunal assemblages on the southern California
coastal shelf. Benthic samples were collected with a 0.1 m2 Van Veen grab from 251 sites on the continental shelf (10–200 m deep) from Point Conception, California, to the United States–Mexico
international border. The relationship between habitat and assemblages was investigated by conducting a Q-mode cluster analysis
to define groups of stations with similar species composition and then examining whether differences were present in physical
habitat attributes among those groups of stations. Analysis of data from 175 uncontaminated sites yielded four habitat-related
benthic infaunal assemblages along the southern California coastal shelf: a shallow-water assemblage from 10–32 m, a mid-depth
assemblage between 32 and 115 m, and two deep-water (115–200 m) assemblages, one in fine and one in coarse sediments. These
empirically defined points in the depth and sediment grain size gradients can be used to define reference habitats for the
development of biocriteria. Benthic abundance and diversity were greatest in the mid-depth assemblage, conforming to predictions
for benthic assemblages in regions of upwelling. Within the 500 km of coastline examined, latitude was not an important factor
in defining assemblages.
Received: 3 December 1999 / Accepted: 9 October 2000 相似文献
20.
Body volume growth rate, dry tissue weight, organic carbon content, and nucleic acid content (RNA and DNA) of individual
Capitella sp. I were measured after 14 d of exposure to natural sediment, sediment contaminated with fluoranthene (in acetone) and sediment
treated with acetone only. Exposure to 101 μg fluoranthene g−1 sediment dry wt during 2 weeks reduced body volume specific growth rate by 50%. Dry tissue weight and carbon content were
also lower in fluoranthene-exposed worms. However, when corrected for differences in body volume, worms from fluoranthene-contaminated
sediment had a higher dry weight and carbon content per unit body volume than worms from the control and acetone treatments.
Part, but not all, of the reduction in body volume growth rate in response to fluoranthene may have been due to a reduction
in tissue water content. The correlation between RNA:DNA ratio (which has previously been used as a predictor of recent growth
rate) and worm growth rate was weak in the control group and was significantly influenced by sediment treatment. Not only
did the fluoranthene-exposed worms have a lower growth rate than expected based on their RNA:DNA ratio, but analysis of this
group separately indicated that measured growth rate was independent of the RNA:DNA ratio. Our results not only confirm previous
indications of a weak relationship between nucleic acid content and actual growth, but indicate that empirical, predictive
relationships between these variables measured under favorable growth conditions should not be extrapolated to predict growth
under toxicant-stressed conditions.
Received: 6 April 1997 / Accepted: 7 May 1997 相似文献