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1.
1. Spatial patterns in channel morphology and substratum composition at small (1–10 metres) and large scales (1–10 kilometres) were analysed to determine the influence of habitat heterogeneity on the distribution and abundance of larval lamprey. 2. We used a nested sampling design and multiple logistic regression to evaluate spatial heterogeneity in the abundance of larval Pacific lamprey, Lampetra tridentata, and habitat in 30 sites (each composed of twelve 1‐m2 quadrat samples) distributed throughout a 55‐km section of the Middle Fork John Day River, OR, U.SA. Statistical models predicting the relative abundance of larvae both among sites (large scale) and among samples (small scale) were ranked using Akaike's Information Criterion (AIC) to identify the ‘best approximating’ models from a set of a priori candidate models determined from the literature on larval lamprey habitat associations. 3. Stream habitat variables predicted patterns in larval abundance but played different roles at different spatial scales. The abundance of larvae at large scales was positively associated with water depth and open riparian canopy, whereas patchiness in larval occurrence at small scales was associated with low water velocity, channel‐unit morphology (pool habitats), and the availability of habitat suitable for burrowing. 4. Habitat variables explained variation in larval abundance at large and small scales, but locational factors, such as longitudinal position (river km) and sample location within the channel unit, explained additional variation in the logistic regression model. The results emphasise the need for spatially explicit analysis, both in examining fish habitat relationships and in developing conservation plans for declining fish populations. 相似文献
2.
Valuable biological information can be obtained by monitoring the movement of organisms. However, the choice of monitoring
method becomes highly restricted when following small organisms (<100 mm), especially in aquatic ecosystems. Stable isotopes
are being increasingly used in this respect but rarely at the local spatial scale, i.e. 10–1000 s of metres. We sought to
identify movement of small fishes between a main river channel and its tributary. Little overlap in isotope baseline was detected
between the two channels despite some temporal variability in δ15N of baseline indicator organisms in the main river. The individuals of two small cyprinid fish species (Leuciscus souffia and Alburnoides bipunctatus) of all the size classes (40–100 mm) caught within the tributary showed considerable heterogeneity in δ15N values. Classification and discriminant analysis on isotope-derived data distinguished two significantly different groups.
Moreover, this result was supported by further sampling of fish caught in the main river (in May and December 2006). Alternative
hypotheses, such as dietary differences, biological factors, temporal shifts and spatial differences in diet, did not explain
δ15N variability. This application of stable isotopes at a relatively small spatial and temporal scales further demonstrates
its potential as a tool for ecologists. 相似文献
3.
Small-scale spatial variability in intertidal and subtidal turfing algal assemblages and the temporal generality of these patterns 总被引:1,自引:0,他引:1
M.A Coleman 《Journal of experimental marine biology and ecology》2002,267(1):53-74
Spatial and temporal variation in patterns of distribution and abundance of algal assemblages is large and often occurs at extremely small spatial and temporal scales. Despite this, few studies investigate interactions between these scales, that is, how patterns of spatial variation change through time. This study investigated a number of scales of spatial variation (from tens of centimetres to kilometres) in assemblages of intertidal and subtidal turfing algae. Significant differences were found in the composition and abundances of species in assemblages of turf at all spatial scales tested. Much of the variation among assemblages could, however, be explained at the scale of quadrats (tens of centimetres apart) (27±1.4 (SE)% of dissimilarity) with an additional 7±1.2% explained at the scale of sites (tens of metres apart) and 10±1.5% at the scale of locations (kilometres apart). Although the greatest dissimilarity in assemblages occurred at the scale of habitats, this accounted for a relatively small proportion of the overall variation in assemblages. These patterns were consistent through time, that is, at each sampling time the spatial scale explaining the greatest proportion of variation in assemblages was replicate quadrats separated by tens of centimetres. These patterns appear to be due to small-scale variation in patterns of distribution and abundances of the individual species that comprise turfing algal assemblages. The results of this experiment suggest that large scale processes have less effect on patterns of variability of algal assemblages than those occurring on relatively smaller spatial scales and that small-scale spatial variation should not be considered as simply “noise”. 相似文献
4.
Juvenile reef fish communities represent an essential component of coral reef ecosystems in the current focus of fish population
dynamics and coral reef resilience. Juvenile fish survival depends on habitat characteristics and is, following settlement,
the first determinant of the number of individuals within adult populations. The goal of this study was to provide methods
for mapping juvenile fish species richness and abundance into spatial domains suitable for micro and meso-scale analysis and
management decisions. Generalized Linear Models predicting juvenile fish species richness and abundance were developed according
to spatial and temporal environmental variables measured from 10 m up to 10 km in the southwest lagoon of New Caledonia. The
statistical model was further spatially generalized using a 1.5-m resolution, independently created, remotely sensed, habitat
map. This procedure revealed that : (1) spatial factors at 10 to 100-m scale explained up to 71% of variability in juvenile
species richness, (2) a small improvement (75%) was gained when a combination of environmental variables at different spatial
and temporal scales was used and (3) the coupling of remotely sensed data, geographical information system tools and point-based
ecological data showed that the highest species richness and abundance were predicted along a narrow margin overlapping the
coral reef flat and adjacent seagrass beds. Spatially explicit models of species distribution may be relevant for the management
of reef communities when strong relationships exist between faunistic and environmental variables and when models are built
at appropriate scales. 相似文献
5.
Coral reef communities of the western Atlantic have changed over the past two to three decades, but the magnitude and causes
of this change remain controversial. Part of the problem is that small-scale patterns observed on individual reefs have been
erroneously extrapolated to landscape and geographic scales. Understanding how reef coral assemblages vary through space is
an essential prerequisite to devising sampling strategies to track the dynamics of coral reefs through time. In this paper
we quantify variation in the cover of hard corals in spur-and-groove habitats (13–19 m depth) at spatial scales spanning five
orders of magnitude along the Florida Reef Tract. A videographic sampling program was conducted to estimate variances in coral
cover at the following hierarchical levels and corresponding spatial scales: (1) among transects within sites (0.01- to 0.1-km
scale), (2) among sites within reefs (0.5- to 2-km scale), (3) among reefs within sectors of the reef tract (10- to 20-km
scale), and (4) among sectors of the reef tract (50- to 100-km scale). Coral cover displayed low variability among transects
within sites and among sites within reefs. This means that transects from a site adequately represented the variability of
the spur-and-groove habitat of the reef as a whole. Variability among reefs within sectors was highly significant, compared
with marginally significant variability among sectors. Estimates from an individual reef, therefore, did not adequately characterize
nearby reefs, nor did those estimates sufficiently represent variability at the scale of the sector.
The structure and composition of coral reef communities is probably determined by the interaction of multiple forcing functions
operating on a variety of scales. Hierarchical analyses of coral assemblages from other geographic locations have detected
high variability at scales different from those in the present study. A multiscale analysis should, therefore, precede any
management decisions regarding large reef systems such as the Florida Reef Tract.
Accepted: 19 July 1999 相似文献
6.
Variation in planktonic larval duration (PLD) and growth of Pomacentrus coelestis was investigated on the southern Great Barrier Reef at multiple spatial scales. A tetracycline experiment, using presettlement
fish, demonstrated that increments were formed daily. Variation in PLD was low between reef clusters (0%), reefs within clusters
(0.4–8.5%) and sites within reefs (13.1%), but high among individuals within sites (86.5–91.5%); PLD ranged from 15 to 27 days.
It was predicted that PLD would vary at greater spatial scales, but differences were low and a review of all studies on P. coelestis in tropical waters had a similar range of PLDs to our study. Contrary to a hypothesis that fish with slower growth would
have longer PLDs, there was no significant relationship between mean presettlement increment width of otoliths and PLD for
fish from the two reef clusters examined. There were, however, differences in presettlement growth rates between reef clusters
(over 100 km apart) over the last 5–6 days of planktonic life. Warmer waters at the Swain Reefs (0.1–1°C) may have contributed
to these differences in growth. Stochastic transport of larvae, habitat choice by presettlement fish in a reef mosaic, and
variable conditions in the plankton may contribute to variation in PLD, presettlement growth and size-at-settlement in P. coelestis. We propose that prolonged periods of settlement choice may obscure simple relationships between PLD and size-at-settlement. 相似文献
7.
Recruitment of scleractinian corals on settlement plates at Heron Island, Great Barrier Reef, was examined over four years
(September 1991–September 1995) to quantify spatio-temporal patterns at different scales and to assess post settlement mortality.
Recruitment was dominated by pocilloporid corals which accounted for 80.1% of the 8627 spat counted, whereas non-isoporan
acroporids represented only 16.4%. Poritids, faviids and isoporan acroporids rarely recruited to the plates (3.5%), despite
their obvious abundance as adults on the reef. Recruitment patterns on the plates indicate strong space-time interactions
as evidenced by patchy recruitment of both pocilloporid and acroporid spat. Interactions were found between space (on the
scale of 102 m, i.e. sites within zones, and 101 m, i.e. racks within sites) and time (on the scale of years) for pocilloporids and between space (on the scale of 103 m, i.e. zones, and 102 m) and time (on the scale of years) for acroporids. Post-recruitment mortality of acroporid spat in the period 3–10 months
after their major spawning was dependent on their initial recruitment density, but pocilloporid mortality was either independent
of initial recruitment density or, more likely, obscured by additional recruitment of pocilloporids to plates between late
February and September. High rates of recruitment and growth by other sessile organisms, particularly bryozoans and oysters,
appear to result in increased post-recruitment mortality and limit recruitment of scleractinian corals on settlement plates.
The work reinforces an emerging picture that coral recruitment patterns are determined by mechanisms that manifest over a
large range of spatial scales.
Accepted: 1 September 1997 相似文献
8.
We evaluated the spatial and temporal scales over which otolith signatures varied in a reef fish on the Great Barrier Reef
(GBR) using the non-dispersing damselfish Acanthochromis polyacanthus. We found a robust multi-element separation in otolith signatures from reef clusters in the northern and southern GBR. Variance
components indicated that this spatial scale accounted for the majority of the variation in two elemental ratios (Ba/Ca and
Sr/Ca) over the 2 years of the study. There was also significant variation in elemental signatures between otoliths collected
over two consecutive years, as well as within a season. Individual reefs within clusters were less distinguishable based on
otolith chemistry and were probably observed by differences within reefs (among sites and broods within sites). These results
indicate that it may be difficult to determine the reef of origin for individual fish using otolith chemistry, while determining
natal region seems a realistic goal. 相似文献
9.
Alexandre M. Garcia João P. Vieira Kirk O. Winemiller Marcelo B. Raseira 《Hydrobiologia》2004,515(1-3):39-48
Jenynsia multidentata is an important component of the fish assemblage of the Patos Lagoon estuary in southern South Brazil. In order to investigate its reproductive cycle and abundance patterns, standardized sampling was conducted over large spatial (marine, estuary and lagoon) and temporal (1996–2003) scales. Both females and males were significantly more abundant during summer (December–March) than winter (June–August). Total abundance was significantly positively correlated with water temperature (R=0.91), but not with salinity and Secchi depth. Females achieved higher average (49.1 mm L T) and maximum size (91 mm) than males (37.7 mm; 66 mm), and average sex ratio was female-biased (3.2:1) across all months. An annual reproductive cycle composed of two cohorts was proposed: individuals born from December to March started reproducing during late winter and spring and individuals born from September to November started reproducing during late summer and fall. A 12-month survey conducted throughout the longitudinal gradient of the lagoon indicated that the species was only present in the estuary, and was absent from marine and upper lagoon areas. The abiotic factors analyzed could not explain this spatial distribution. Inter-annual variation in abundance was great, with higher abundance during drier years. A `dilution effect' was proposed to explain the low abundance of the species in the estuary during high-rainfall trigged by El Niño episodes. 相似文献
10.
Although spatial and temporal variation in plankton diversity is regularly investigated in surveys, experiments, and models,
there is a lack of methods for predicting spatial patchiness of plankton diversity. We develop and apply a suite of geostatistical
and multiple-regression analysis tools to assess ciliate diversity in a tropical coastal lagoon; these methods can predict
spatial and temporal patterns of diversity, provide error estimates associated with these predictions, and assess which environmental
factors may drive diversity patchiness. Geostatistical analysis was applied to H′ (Shannon diversity index) from 25 to 35 data collected from a sampling grid (40 × 40 m), and 10 dispersed lagoonal sites,
in the dry and rainy seasons, on numerous occasions. Conditional simulation and kriging were used to predict diversity at
the lagoonal and small scales, respectively. The relationship between diversity (H′) and the environment was examined by multiple-regression analysis. Thirty-six ciliate morphospecies occurred; H′ ranged from 0 to 1.9 and was patchy. Multiple regression indicated ciliate diversity changed seasonally, increasing when
the sand bar was open and the lagoon was connected with the sea. Geostatistical analysis extended the recognition that seasonal
changes alter diversity: when the rainy season produced a variable environment, relatively small scale patches and diversity
gradients occurred; in the dry season, when the lagoon was physically uniform, larger and fewer diversity patches occurred;
at the sublagoonal scale, diversity patches were similarly structured in the two seasons. Results indicate environmental variability
and immigration can be the main drivers behind ciliate diversity in the lagoon. We recommend the patterns these data reveal
and methods we employ be considered when further studies are continued to examine diversity on local and larger scales.
Handling editor: S. Declerck 相似文献
11.
M.A. Coleman 《Journal of experimental marine biology and ecology》2003,291(1):131-145
Recruitment is often important in structuring patterns of distribution and abundance of algal assemblages. Intertidal and subtidal turfing algal assemblages consistently vary on small spatial scales (tens of centimetres), and this variability may be due to patterns of recruitment varying on similar spatial scales. The validity of this model was evaluated by testing the hypothesis that the numbers and types of taxa recruiting to turfs would vary at small spatial scales within intertidal and within subtidal habitats. Abundances of algal recruits were estimated on sandstone plates that were placed at a number of spatial scales within intertidal and within subtidal habitats (centimetres to tens of metres). Significant differences in entire assemblages were found only between habitats. This was explained by abundances of individual taxa, which generally varied between intertidal and subtidal habitats or between sites within habitats. Only small proportions of the overall spatial variation (dissimilarity) could be explained at the scale of replicate recruitment plates that were centimetres apart. Results indicate that while recruitment may contribute to differences between intertidal and subtidal habitats, it cannot explain the small-scale spatial variability in established turfing algal assemblages within these habitats. There was some evidence to suggest that recruitment may contribute to variability in established turfing algal assemblages but only over longer time scales than examined here. 相似文献
12.
Patterns of growth in an exploited reef fish Lethrinus miniatus were examined over 5 years (1995–1999) at two spatial scales: (1) among regions of the Great Barrier Reef (GBR) separated by >100 km and (2) among reefs within each of these regions, separated by ≤10 km. Mean annual growth of L. miniatus varied significantly among years, but this variation was consistent among ages and regions, indicating that factors that influence temporal patterns in growth were not age-specific and operated at relatively large spatial scales. Significant variation in growth was also observed among some reefs within regions, although the greatest variation was among regions. The average maximum fork length ( ) and average maximum mass ( M ∞ ) varied significantly among regions, suggesting that productivity of L. miniatus is likely to vary among regions of the GBR. There was also significantly greater mass of fish for a given L F in two regions, which magnified the regional differences in M ∞ . The observed temporal and spatial variation in growth highlighted the importance of a multi-scale approach to population studies and assessment of fish stocks. 相似文献
13.
14.
Core samples were taken along a 4 km stretch of intertidal seagrass on North Stradbroke Island, eastern Australia, at nested
scales of 1 m (stations), 150 m (sites), and 2 km (localities) to investigate the extent to which abundance, diversity, and
assemblage composition of the dominant smaller members (<10 mm) of the intertidal seagrass macrobenthos vary spatially and
over what scales. Gastropods and polychaetes dominated both the 91 species present and, together with decapods, also the numbers
of individuals. Abundance was low (mean < 2000 individuals m−2) but species diversity was high (overall Simpson’s index of diversity 0.91), with 44% of species occurring only as one or
two individuals, and with only two species contributing >10% to the total numbers (the microgastropod Calopia imitata and crab Enigmaplax littoralis, both little known, rarely recorded endemics). On average, a species only occurred at 6% of stations and only four occurred
at >25%. Assemblages at the three localities did not vary significantly in gross ecological features (levels of species richness,
faunal abundance and species diversity per component site) (ANOVA P ≫ 0.05), but did vary markedly in their composition at all spatial scales (PERMANOVA P < 0.05). Variance partitioning showed that components of total variance were least at the largest spatial scale (locality
15.9%) and greatest at the smallest scale (station 59.3%). The commoner individual species all showed random distributions
at small spatial scales but clumped distributions at large spatial scales. 相似文献
15.
Patterns of spatial and temporal variation of macrofauna under boulders in a sheltered boulder field
M. G. Chapman 《Austral ecology》2002,27(2):211-228
Abstract Spatial and temporal patterns of abundance of animals and plants must be quantified before models to explain distributions can be developed. These patterns also provide essential data for measuring potential effects of environmental disturbances. Studies in many different habitats have shown that most organisms, particularly invertebrates, have highly variable and interactive patterns of abundance, with much variability at the smallest temporal and spatial scales. Intertidal boulder fields in New South Wales, Australia, support a diverse fauna, many species of which are relatively rare. These habitats are commonly found near rock‐platforms and in sheltered estuaries and are subjected to many human disturbances. Although there have been a few studies on the fauna in boulder fields, none has documented variability of the assemblage using multivariate and univariate techniques and most studies have not incorporated different spatial and temporal scales. This study quantifies spatial variation at three scales (metres, tens of metres alongshore and tens of metres upshore) and temporal variation at two scales (3 months and 2 years) of the assemblage of molluscs and echinoderms in a sheltered boulder field subjected to little natural or human disturbance. Multivariate analyses revealed that each site contained a distinct assemblage, mainly due to the relative abundances of a few species. Most species, those generally only found under boulders and common, widespread species, had considerable spatial variability in abundances, with more than 90% measured at the smallest scale, that is metre to metre within a site. Changes in abundances over 3 months or 2 years varied among species and sites in unpredictable ways. These data show that sampling designs to measure impacts on these fauna will need to be complex and must incorporate a number of spatial and temporal scales if they are to be able to detect impact against such a variable background. 相似文献
16.
Dispersal in marine systems is a critical component of the ecology, evolution, and conservation of such systems; however,
estimating dispersal is logistically difficult, especially in coral reef fish. Juvenile bicolor damselfish (Stegastes partitus) were sampled at 13 sites along the Mesoamerican Barrier Reef System (MBRS), the barrier reefs on the east coast of Central
America extending from the Yucatan, Mexico to Honduras, to evaluate genetic structure among recently settled cohorts. Using
genotype data at eight microsatellite loci genetic structure was estimated at large and small spatial scales using exact tests
for allele frequency differences and hierarchical analysis of molecular variance (AMOVA). Isolation-by-distance models of
divergence were assessed at both spatial scales. Results showed genetic homogeneity of recently settled S. partitus at large geographic scales with subtle, but significant, genetic structure at smaller geographic scales. Genetic temporal
stability was tested for using archived juvenile S. partitus collected earlier in the same year (nine sites), and in the previous year (six sites). The temporal analyses indicated that
allele frequency differences among sites were not generally conserved over time, nor were pairwise genetic distances correlated
through time, indicative of temporal instability. These results indicate that S. partitus larvae undergo high levels of dispersal along the MBRS, and that the structure detected at smaller spatial scales is likely
driven by stochastic effects on dispersal coupled with microgeographic effects. Temporal variation in juvenile cohort genetic
signature may be a fundamental characteristic of connectivity patterns in coral reef fishes, with various species and populations
differing only in the magnitude of that instability. Such a scenario provides a basis for the reconciliation of conflicting
views regarding levels of genetic structuring in S. partitus and possibly other coral reef fish species. 相似文献
17.
Spatial patterns in abundance of a damselfish reflect availability of suitable habitat 总被引:9,自引:0,他引:9
For species with metapopulation structures, variation in abundance among patches can arise from variation in the input rate
of colonists. For reef fishes, variability in larval supply frequently is invoked as a major determinant of spatial patterns.
We examined the extent to which spatial variation in the amount of suitable habitat predicted variation in the abundance of
the damselfish Dascyllus aruanus, an abundant planktivore that occupies live, branched coral throughout the Indo-Pacific. Reef surveys established that size,
branching structure and location (proximity to sand) of the coral colonies together determined the ”suitability” of microhabitats
for different ontogenetic stages of D. aruanus. Once these criteria were known, patterns of habitat use were quantified within lagoons of five Pacific islands. Availability
of suitable habitat generally was an excellent predictor of density, and patterns were qualitatively consistent at several
spatial scales, including among different lagoons on the same island, among different islands and between the central (French
Polynesia and Rarotonga) and western (Great Barrier Reef, Australia) South Pacific. A field experiment that varied the amount
of suitable coral among local plots indicated that habitat for settlers accounted for almost all of the spatial variation
in the number of D. aruanus that settled at that location, suggesting that spatial patterns of abundance can be established at settlement without spatial
variation in larval supply. Surveys of four other species of reef-associated fish revealed that a substantial fraction of
their spatial variation in density also was explained by availability of suitable reef habitat, suggesting that habitat may
be a prevalent determinant of spatial patterns. The results underscore the critical need to identify accurately the resource
requirements of different species and life stages when evaluating causes of spatial variation in abundance of reef fishes.
Received: 18 May 1999 / Accepted: 9 January 1999 相似文献
18.
J.-P. Torréton 《Coral reefs (Online)》1999,18(1):43-53
Biomass, production and heterotrophic activity of bacterioplankton were determined for two weeks in the Great Astrolabe Reef
lagoon, Fiji. Bacterial and Bacterial activities were distributed homogeneously throughout the water column (20 to 40 m deep)
and varied little from site to site inside the lagoon. Bacterioplankton biomass and production also varied little over a diel
period with coefficients of variation of 9 and 22%, respectively. On average, over the whole study, bacterial abundance was
0.77×109 cells l-1 and bacterial production averaged 0.36 μg-at. C l-1 d-1. Bacterial abundance and production were greater in the lagoon than in oceanic waters. Attachment to particles seems to provide
an advantage for bacterioplankton growth because specific growth rates for attached bacterioplankton were, on average, significantly
greater than that of the free community. Growth efficiency, determined by correlating the net increase of bacterial biomass
and the net decrease of dissolved organic carbon (DOC) in dilution cultures, was very low (average 6.6%). Using carbon growth
efficiency and bacterial production rates, heterotrophic activity was estimated to average 5.4 μg-at. C l-1 d-1. The turn-over rate of DOC (average 114 μg-at. C l-1) due to bacterial consumption was estimated to be 0.048 d-1 during the period of study.
Accepted: 25 July 1998 相似文献
19.
Spatial patterns in the abundance of the softsediment meiofauna and a predatory goby, Valenciennia longipinnis, were examined in the lagoon of One Tree Reef (Great Barrier Reef). The study provided a quantitative framework to assess the importance of physical factors on and predator prey interactions between the meiofauna and V.longipinnis. Patterns of abundance were examined at two spatial scales: among four habitats (100's of m apart) and among sites (10's of m apart) within habitats. Of the four major constituents of the meiofauna (harpacticoid copepods, nematodes, polychaetes and oligochaetes), gut analyses showed that harpacticoid copepods were the primary prey of V.longipinnis. Spatial patterns of meiofaunal abundance in the lagoon were taxon specific. Polychaetes and harpacticoid copepods exhibited significant differences among habitats. Within habitats, however, polychaetes exhibited significant differences between sites whereas copepods were uniformly distributed. Abundances of nematodes and oligochaetes did not differ between habitats. Densities of nematodes differed significantly between sites while the number of oligochaetes were similar at both spatial scales. V.longipinnis was more abundant in shallow habitats than in deep ones. This study suggests that sediment type may be an important factor influencing the distribution of both the goby and the meiofauna. V.longipinnis and two of the four meiofaunal taxa (harpacticoid copepods and polychaetes) were more abundant in the shallow habitat with fine-grained sediments. There was no significant difference between abundances of meiofaunal taxa in sites where V.longipinnis was present or absent. Overall, more fish occurred in the habitat which had the highest densities of harpacticoid copepods. 相似文献