Vertical distribution,abundance and community structure of oncaeid copepods in the Oyashio region,western subarctic Pacific

The vertical distribution, abundance and community structure of oncaeid copepods were investigated in the Oyashio region, western subarctic Pacific. Samples were collected with a 0.10 mm mesh closing type net from five discrete layers down to a maximum depth of 2,000 m in September and December 1996 and in April and October 1997. The copepods were widely distributed from epipelagic to bathypelagic zones, and showed prominent peaks of abundance above the thermocline and/or between 250 and 1,000 m depth. Standing stocks of total oncaeid copepods ranged from 1.5 to 2.5×10⁵ inds m^–2 at 0–2,000 m in the water column, which are the same order of magnitudes as those reported in tropical, subtropical and polar regions by previous workers. A total of 38 species and two forms belonging to the genera Oncaea, Triconia, Spinoncaea, Conaea and Epicalymma, and two provisionally classified species of the family Oncaeidae were identified in this study. Of these, 14 species have already been recorded from the eastern subarctic Pacific. Several warm-water species were also found in December 1996 and/or October 1997, when the effect of warm-core rings originating from the Kuroshio Current was evident in the epipelagic zone. Dominant species throughout the whole water column were T. borealis, T. canadensis, O. grossa, O. parila, O. rimula, O. lacinia, Epicalymma spp. and Oncaea sp. A, and these eight species together always made up about half of the total oncaeid numbers. Community analysis revealed that species composition in epipelagic and upper mesopelagic zones varied temporally due to the changes of hydrographic conditions, whereas those in lower mesopelagic and bathypelagic zones were relatively stable, reflecting the constancy of deep environments.Communicated by O. Kinne, Oldendorf/Luhe     

The distribution of lianas and their change in abundance in temperate forests over the past 45 years

Lianas (woody vines) are an important and dynamic component of many forests throughout the world, and increases in CO2, mean winter temperature, and forest fragmentation may promote their growth and proliferation in temperate forests. In this study, we used a 45-year data set to test the hypothesis that lianas have increased in abundance and basal area in the interiors of 14 deciduous temperate forests in Wisconsin (USA) since 1959. We also censused woody plants along a gradient from the forest edge to the interior in seven of these forests to test the hypothesis that the abundance of lianas declines significantly with increasing distance from the forest edge. We found that lianas did not increase in abundance within the interiors of temperate forests in Wisconsin over the last 45 years. However, relative and absolute liana abundance decreased sharply with increasing distance from forest edges. Our findings suggest that forest fragmentation, not climate change, may be increasing the abundance of lianas in northern deciduous temperate forests, and that lianas may further increase in abundance if the severity of forest fragmentation intensifies.     

Invasive prey impacts the abundance and distribution of native predators

While an extensive literature exists on the negative effects of invasive species, little is known about their facilitative effects on native species, particularly the role of invasives as trophic subsidies to native predators. The invasive gypsy moth (Lymantria dispar) undergoes periodic outbreaks during which it represents a super-abundant food source for predators capable of consuming it, particularly native cuckoos (Coccyzus erythropthalmus and C. americanus). We examined how gypsy moth outbreaks affect the abundance and distribution of cuckoos using the North American Breeding Bird Survey and 29 years of U.S. Forest Service gypsy moth defoliation records. Abundances of both Black-billed and Yellow-billed Cuckoos were significantly above average during outbreaks, but populations were average or below average in preceding and subsequent years, suggesting that cuckoos are immigrating to defoliations during outbreak years. Spatial analyses showed that cuckoo abundances approximately 40-150 km outside of defoliation areas were significantly below average, and these under-occupied breeding areas extended in all four compass directions around outbreaks. This result supports the idea that cuckoos locate gypsy moth outbreaks during a post-migratory nomadic phase. By shifting the annual distribution of cuckoos, gypsy moths may be shifting the trophic impact of cuckoos across large distances, which could affect native insect herbivores and plants.     

Different patterns of phytoplankton distribution,cell size,species' composition and abundance

A survey of the phytoplankton in the eastern Atlantic Ocean south of the Gulf of Guinea was undertaken, covering the local cyclonic gyre in the neutral col between the South Subtropical gyre, the Equatorial Countercurrent and the coast of Africa. Phytoplankton distribution, cell size, and abundance displayed distinct patterns which are presumed to be related to differential environmental dependence.     

Zooplankton biodiversity and lake trophic state: explanations invoking resource abundance and distribution

While empirical studies linking biodiversity to local environmental gradients have emphasized the importance of lake trophic status (related to primary productivity), theoretical studies have implicated resource spatial heterogeneity and resource relative ratios as mechanisms behind these biodiversity patterns. To test the feasibility of these mechanisms in natural aquatic systems, the biodiversity of crustacean zooplankton communities along gradients of total phosphorus (TP) as well as the vertical heterogeneity and relative abundance of their phytoplankton resources were assessed in 18 lakes in Quebec, Canada. Zooplankton community richness was regressed against TP, the spatial distribution of phytoplankton spectral groups, and the relative biomass of spectral groups. Since species richness does not adequately capture ecological function and life history of different taxa, features which are important for mechanistic theories, relationships between zooplankton functional diversity (FD) and resource conditions were examined. Zooplankton species richness showed the previously established tendency to a unimodal relationship with TP, but functional diversity declined linearly over the same gradient. Changes in zooplankton functional diversity could be attributed to changes in both the spatial distribution and type of phytoplankton resource. In the studied lakes, spatial heterogeneity of phytoplankton groups declined with TP, even while biomass of all groups increased. Zooplankton functional diversity was positively related to increased heterogeneity in cyanobacteria spatial distribution. However, a smaller amount of variation in functional diversity was also positively related to the ratio of biomass in diatoms/chrysophytes to cyanobacteria. In all observed relationships, a greater variation of functional diversity than species richness measures was explained by measured factors, suggesting that functional measures of zooplankton communities will benefit ecological research attempting to identify mechanisms behind environmental gradients affecting diversity.     

Fragmented seagrass habitats on the Mediterranean coast, and distribution and abundance of mysid assemblages

Four different habitats were sampled in order to determine the spatial and temporal distribution and abundance of mysids in a seagrass meadow ecosystem. These habitats included meadows of Posidonia oceanica and Cymodocea nodosa, the edge of P. oceanica meadow and sandy substrates. Three random sites for each habitat were sampled along the coast of Alicante at different times, using a hand-net technique (6 m²). Seven species of mysids were identified: Leptomysis posidoniae, Leptomysis buergii, Paramysis helleri, Siriella clausii, Mesopodopsis slabberi, Siriella armata and Mysidopsis gibbosa. Total abundance of mysids was highest at the edge of the P. oceanica meadow, followed by the C. nodosa meadow, sandy substrate and P. oceanica meadow, respectively (P<0.05); this pattern was found during all sampling periods except one. Three species showed persistent spatial segregation by habitat (S. clausii in Posidonia; L. posidoniae at the edge; S. armata in Cymodocea), whereas the other four did not show any clear segregation by habitat (ANOVA, P<0.01). On a site scale (km), spatial variability was very high. Multivariate analyses confirm the existence of differences in the assemblage structure among habitats, with a gradual change from the Posidonia meadow to sand. Posidonia and Cymodocea showed different mysid assemblages. Fragmented, shallow, vegetated habitat on the Mediterranean coast seems to support a higher abundance and species richness of mysids, through habitat diversification, in comparison with homogeneous habitats.     

Vertical distribution and migration of fishes of the lower mesopelagic zone off Oregon

An exceptionally large midwater trawl (50 m² mouth area) with 5 opening and closing codends was towed horizontally in the lower mesopelagic zone at depths of 500, 650, 800 and 1000 m off Oregon (USA) from 1–6 September, 1978. In comparison to more conventional trawls, ours collected more fish, including rare species and large individuals of common species. Comparison of collections made by day and by night revealed that 12 of the 15 most common species probably migrated vertically. Bathylagus milleri evidently migrates from 650 m during the day to 500 m at night. Cyclothone acclinidens and C. atraria were more abundant by night than by day at 800 m, possibly due to an upward migration from deeper depths at night. C. pseudopallida, C. signata, Chauliodus macouni, Tactostoma macropus and Stenobrachius leucopsarus were more abundant by day than by night at 500 m, suggesting that they migrated out of this depth horizon at night. Lampanyctus regalis, and large individuals of B. pacificus were more abundant by night than by day at 500 m, possibly because they migrated upward from near 650 m. Many species exhibited trends of increasing or decreasing size with depth, and several species showed changes in migratory behavior with size. For example, only small (<240 mm) T. macropus migrated vertically, whereas only large (>110 mm) B. pacificus appeared to migrate. Depths of maximum abundance of congeneric species were usually separated. B. milleri and B. pacificus had similar distributions by day, but the former was shallower at night. S. leucopsarus tended to live shallower than S. nannochir both day and night. Congeners always occurring at the same depth were Cyclothone pseudopallida and C. signata (both most abundant at 500 m) and C. acclinidens and C. atraria (both most abundant at 800 m).     

三江平原泥炭地微量元素垂直分布特征

采用冬季采样，现场分层的方法，系统地研究了三江平原河床-河漫滩型泥炭地和谷底洼地型泥炭地微量营养元素和有益元素的垂直分布特征。结果表明，微量营养元素Cu、Zn、Fe、Mn、B和有益元素Ni、Sr、Ti、V、Co均有在G层急剧积累的趋势，Fe、Mn、B、Zn、Ti、Sr质量分数在Ase层明显高于泥炭层，某些微量元素间具有显著的相关性。     

Vertical distribution of phytoplankton during investigations of a natural surface film

An interdisciplinary research program (Kombiniertes Oberflächenfilmprojekt KOFF), in the North Sea area about 75 km west of the Island of Sylt, is directed towards gaining further knowledge on the biological importance of the natural surface film. The investigations include the water body below the film as well as dynamic processes at the surface. Persistence of calm weather conditions (cloudless sky) before and during the investigations permitted observations of the diurnal species-specific vertical migration of Dinophyceae. Two groups could be distinguished: (1) Prorocentrum micans and Ceratium furca; (2) C. horridum, C. macroceros and C. fusus. The active accumulation of P. micans in the slick was verified by a significant correlation coefficient—linearly correlated with the time of day. The results presented reveal continuity between surface film and underlying water column.This work was supported by the Sonderforschungsbereich (SFB) 94, Hamburg, of the Deutsche For-schungsgemeinschaft.     

Impact of sewage on the distribution,abundance and community structure of rocky intertidal macro-organisms

The biological effects of a low-volume domestic sewage discharge were studied near Wilson Cove, San Clemente Island, California (USA), from February to June, 1972. There were fewer species and less cover near the outfall (7 macro-invertebrates, 17.6%; 13 macrophytes, 91.7%) than in nearby “unpolluted” control areas (9 macroinvertebrates, 9.2%; 30 macrophytes, 103.4%). The outfall biota was less diverse than that of the controls, as shown by 5 different diversity indices. A great reduction in community stratification (spatial heterogeneity) and, hence, community complexity occurred near the outfall; this reduction in stratification was primarilly due to the absence of Egregia laevigata, Halidrys dioica, Sargassum agardhianum and Phyllospadix torreyi. These were replaced in the mid-intertidal near the outfall by a low turf of blue-green algae, Ulva californica, Gelidium pusillum and small Pterocladia capillacea, and in the lower intertidal by Serpulorbis squamigerus covered with Corallina officinalis Var. chilensis. A statistically-based determination of assemblages or groups of organisms (i.e., cluster analysis) revealed 3 discrete outfall and 3 discrete control area groups; 3 assemblages contained samples from both areas. The distributional patterns of these groups indicate that near the outfall the degree of dilution of discharged sewage is more important in regulating zonation than is tidal height. The enhancement of the suspension feeder Serpulorbis squamigerus and the omnivores Ligia occidentalis, Pachygrapsus crassipes and Anthopleura elegantissima in the outer fringe of the outfall plume hypothetically is due to their ability to utilize sewage as a food source. A critical effect of the outfall may be to decrease environmental stability thereby favoring rapid-colonizers and more sewage-tolerant organisms. The outfall macrophytes were characterized by relatively higher net primary productivities, smaller growth forms, simpler and shorter life histories, and most were components of early successional stages.     

Vertical and horizontal distribution of sub-littoral meiofauna in Algoa Bay,South Africa

Meiofauna was sampled using SCUBA along 4 transects from 5 to 30 m depth in Algoa Bay, South Africa. Substrates were well-sorted medium to fine sands with traces of sewage pollution in some areas. Meiofauna numbers recorded in the upper 10 cm of sediment were 55 to 584 10 cm^-2, but total numbers, including deeper-living animals, were 680 to 2090 10 cm^-2 at 6 stations. Longer cores showed meiofauna to be abundant down to at least 35 cm, and samples of interstitial water taken from this depth in the sediment were 7% saturated with oxygen. This is the first detailed record of meiofauna penetration into sub-littoral sand and stresses the need for long cores for quantitative work. Nematode numbers were found to be significantly related to nitrogen in the sand while interstitial harpacticoid numbers were related to median particle diameters, which determine pore space. Effects of sewage were slight and only one station showed notable enrichment, increased meiofaunal numbers and extreme dominance by nematodes.     

Vertical distribution and feeding patterns of midwater fish in the central equatorial Atlantic

Fishes and zooplankton were obtained (March–April 1979 and partly in August 1974) from 45 hauls taken during the day and at night in the central equatorial Atlantic between Latitude 3°N and 2°S from the surface to 1250-m depth, using the RMT 1+8, a combined opening-closing plankton and micronekton trawl. The vertical distribution of 30 myctophid species is described. All species migrate in a diel pattern, Ceratoscopelus warmingii and Lampanyctus photonotus down to at least 1250 m. During daytime most species aggregated at 400-to 700-m depth, therefore only partly occupying the depth of the Deep Scattering Layer (400 to 500 m at 15 kHz). The feeding patterns of seven of the most abundant species were compared, with a total of 1 905 stomach contents being analysed. All seven species are regarded as opportunistic predators, which feed predominantly during the night on calanoid copepods. A total of 66 species of calanoid copepods were identified among the prey items, with smaller species definitely being in the minority. Stomachs of C. warmingii (700 to 1 250 m depth) and Lepidophanes guentheri (500 to 900 m depth) from daytime samples contained copepod species restricted to the upper 150 m of the water column, including Undinula vulgaris, Nannocalanus minor, and Euchaeta marina, thereby confirming an extended vertical migration of predators. Differences in diet and preferences between species in their total food spectrum are described.     

Facilitation drives local abundance and regional distribution of a rare plant in a harsh environment

The importance of facilitation to local community dynamics is becoming increasingly recognized. However, the predictability of positive interactions in stressful environments, the balance of competition and facilitation along environmental gradients, and the scaling of local positive interactions to regional distributions are aspects of facilitation that remain unresolved. I explored these questions in a habitat specialist, Delphinium uliginosum, and a moss, Didymodon tophaceus, both found in small serpentine wetlands. I tested three hypotheses: (1) moss facilitates germination, growth, and/or fecundity of D. uliginosum; (2) facilitation is stronger at the harsher ends of gradients in soil moisture, toxicity, and/or biomass; and (3) facilitation is reflected in positive associations at the levels of local abundance and regional occurrence. Although considerable competitive interactions occurred in later life stages, moss strongly facilitated D. uliginosum seedling emergence. There was no evidence that this facilitative effect weakened, or switched to competition, in benign environments. D. uliginosum was more locally abundant and more frequently present, across a large portion of its range, with than without moss, indicating a net facilitative effect in the face of competitive influences. Facilitated recruitment, possibly by seed retention, was found to be an important control on abundance and distribution in this rare species.     

A mathematical model for the distribution and abundance of benthic algae in a Norwegian fjord

A mathematical model has been developed to study the distribution and abundance of benthic algae species in a Norwegian fjord. The main forcing functions are the physical factors which have well defined gradients in this area, but biotic interactions are also accounted for in the model.The distribution of algae along vertical transects in the intermediate fjord area has been simulated, and the observed distribution is reproduced fairly well. This indicates that the major factors determining the equilibrium elevation between intertidal and subtidal vegetations in this area are adequately represented in the model.Based on observations in a fjord branch with a high level of freshwater influx and polluted by heavy metals, assumptions are made of the combined influence of these contaminants on growth characteristics of the species considered. The resulting effects on community development and community patterns are simulated. For a certain level of contamination, the decrease in abundance, community development rate and species separation have been determined. It is also shown that the fluctuations in biomass during a year are more pronounced than under unaffected conditions.The relative importance of external growth regulating factors and self-shading is demonstrated for different degrees of community development, and we have indicated that this may be an important factor in the assessment of transient and long-term responses to “natural” and man-made influences on the shore-line vegetation.One of the main problems during model development was the formulation of the interaction function for factors influencing growth parameters. Several alternatives were examined.The differences between the most frequently used forms were small with respect to abundance and not very large with respect to possible changes in distribution. It was noted that even by including only the most limiting factor at each instant, (Liebig's form) a high percentage of the potentially limiting factors did actually limit growth during periods of the year.The model is intended as a working tool for the studies of changes in the shore-line vegetation caused by man-made interferences like heavy metal and oil pollution, and we believe that the results presented demonstrate that it can successfully be used for this purpose.     

Vertical profiles of bacterial abundance,productivity and growth rates in coastal sediments of the central Great Barrier Reef lagoon

Vertical patterns of bacterial densities, productivity and specific growth rates in coastal muds, quartz sands and muddy sands of the central Great Barrier Reef lagoon were examined in summer (February) and autumn (May) 1988. Variations in these parameters with station location, sediment depth and season were complex, exhibiting significant main and interaction effects in most instances. Some trends were apparent despite the large and complex variations. Bacterial densities did not vary seasonally, ranging from 2.9 to 38.1×10⁹ cells g^-1 dry wt, averaged over sediment depth (0 to 20 cm) and seasons. Trend analysis revealed that densities decreased with increasing sediment depth. Bacterial production (tritiated thymidine incorporation into DNA) was high, ranging from 0.4 to 5.7 gCm^-2 d^-1 (integrated over 10 cm depth), as were specific growth rates (grand mean, =0.25 d^-1; range=0.004 to 1.3 d^-1). Both were generally higher in summer than in autumn. Vertical profiles of productivity and specific growth rates revealed actively growing bacterial assemblages down to 20 cm depth. Factors which may account for these very abundant and productive communities are: (1) subsurface accumulations of detritus exported from adjacent mangrove forests, and (2) physical disturbance from tidal scouring and severe climate (e.g. cyclones, wet-season floods). Disturbance events occur frequently enough to inhibit the development of highly sulphidic conditions, but stimulate production of bacterial types (aerobes, fermenters) capable of incorporating labelled thymidine into their DNA.     

Larval bloom of the oviparous sponge Cliona viridis: coupling of larval abundance and adult distribution

 We performed an intensive year-round sampling with the aim of studying the abundance of sponge larvae in four Mediterranean benthic communities: photophilic algae, sciaphilous algae, semi-obscure (i.e. low light-intensity) caves and sandy bottoms. We record here for the first time, a larval bloom of Cliona viridis (Schmidt 1862), the most common excavating sponge in the Mediterranean, which took place simultaneously in several rocky communities of the Blanes sub-littoral (NE Spain), and discuss the role of restricted larval dispersal in the distribution of adult sponges. In the communities studied, C. viridis larvae bloomed synchronously once, in June. Spawning and consequent embryo development presumably occurred in May, when water temperature was 16 °C. The free larva is a small, evenly ciliated, weakly swimming parenchymella with low dispersal capabilities. The number of larvae m⁻³ and sponge abundance (as percent cover and biomass) were significantly higher in the community of sciaphilous algae than in the other communities studied. Because of limited larval dispersal, larval and adult abundance in the communities were positively correlated. Larvae developed into juvenile sponges 10 to 15 d after settlement. Settlers displayed distinctive features: a peripheral cuticle, vacuolar etching-like cells at the sponge base, absence of oscular chimneys, and the presence of zooxanthellae, which were presumably transmitted during oocyte maturation. Received: 24 January 2000 / Accepted: 4 July 2000     

Vertical distribution of mesoplankton in the open area of the Black Sea

In April–May 1984 mesoplankton vertical distribution in the Black Sea was studied by sampling with a 150-l waterbottle, vertical plankton nets with mesh-sizes of 180 and 500 mkm and by direct counting of the jelly-fish Aurelia aurita, the ctenophore Pleurobrachia pileus, Calanus helgolandicus and the chaetognath Sagitta setosa from the manned submersible Argus. During daytime throughout the whole deep-water body of the sea near the lower oxycline boundary, plankton forms a layer of high concentration (from 2.5 to 38 g m^-3); its thickness varies from 5 to 10–20 m and it has an unchangeable vertical structure; its upper portion is formed by the ctenophore P. pileus, its middle portion by V–VI copepodites of C. helgolandicus, and its lower portion by the population of S. setosa. The lower boundary of this layer coincides with 0.4 to 0.5 ml O₂ l^-1 isooxygen surface, and the depth of its location varies in different areas of the sea from 150 to 50 m, depending on the depth location of 0.5 ml O₂ l^-1 isooxygen surface. By night the animals, which form this layer, migrate towards the surface.     

Partitioning of \alpha and \beta diversity using hierarchical Bayesian modeling of species distribution and abundance

Diversity partitioning is becoming widely used to decompose the total number of species recorded in an area or region \((\gamma )\) into the average number of species within samples \((\alpha )\) and the average difference in species composition \((\beta )\) among samples. Single-value metrics of \(\alpha \) and \(\beta \) diversity are popular because they may be applied at multiple scales and because of their ease in computation and interpretation. Studies thus far, however, have emphasized observed diversity components or comparisons to randomized, null distributions. In addition, prediction of \(\alpha \) and \(\beta \) components using environmental or spatial variables has been limited to more extensive data sets because multiple samples are required to estimate single \(\alpha \) and \(\beta \) components. Lastly, observed diversity components do not incorporate variation in detection probabilities among species or samples. In this study, we used hierarchical Bayesian models of species abundances to provide predictions of \(\alpha \) and \(\beta \) components in species richness and composition using environmental and spatial variables. We illustrate our approach using butterfly data collected from 26 grassland remnants to predict spatially nested patterns of \(\alpha \) and \(\beta \) based on the predicted counts of butterflies. Diversity partitioning using a Bayesian hierarchical model incorporated variation in detection probabilities by butterfly species and habitat patches, and provided prediction intervals for \(\alpha \) and \(\beta \) components using environmental and spatial variables.     

Vertical distribution of bivalve larvae along a cross-shelf transect during summer upwelling and downwelling

Previous time-series studies of meroplankton abundances in the LEO-15 research area off Tuckerton, New Jersey, USA (39°28′N, 74°15′W) indicated short-lived (6–12 h) pulses in larval surfclam (Spisula solidissima Dillwyn) concentration often associated with the initiation of downwelling. To examine possible larval surfclam (and other bivalve) concentrating mechanisms during upwelling and downwelling, six sets of adaptive mobile zooplankton pump samples were taken in July 1998 at different depths at five to six stations along a 25-km transect perpendicular to the coastline and crossing Beach Haven Ridge at LEO-15. Sampling was guided by near real-time, satellite imagery of sea surface temperature overlain by sea surface currents from a shore-based ocean surface current radar (OSCR) unit. A Seabird CTD on the mobile pump frame near the intake provided information on thermocline depth, and sampling depths were adjusted according to the temperature profiles. Near shore, the thermocline was tilted down during downwelling, and up during upwelling. The highest concentrations of surfclam larvae occurred near the bottom at a station near Beach Haven Ridge during downwelling, and just above the thermocline 3 km further offshore during well-developed upwelling. For other bivalve taxa, the larvae were concentrated near the thermocline (Anomia simplex Orbigny and Pholadidae spp.) or concentrated upslope near the bottom (Mytilidae spp.) during upwelling, and the larvae were concentrated near the bottom or were moved downslope during downwelling. Donax fossor Say larvae were found near the surface or above the thermocline during upwelling and downwelling. The general patterns of larval bivalve distribution appear to be influenced by water mass movement during upwelling and downwelling. The larval concentration patterns of individual species are likely a consequence of advection due to upwelling and downwelling circulation, vertical shear in the front region, species-specific larval behaviors, and larval sources.     

Vertical distribution and environmental significance of PAHs in soil profiles in Beijing,China

Vertical distribution of both the concentration and composition of polycyclic aromatic hydrocarbons (PAHs) in ten profiles in Beijing has been investigated. The results showed that PAH concentrations and compositions in topsoil from different sampling sites were different. PAH concentrations were much higher in topsoil of the investigated urban area, industrial region, and paddy field with wastewater irrigation than in other areas. Moreover, PAH concentrations in topsoil were much higher than those at greater depth, where the concentrations were relatively consistent in most soil profiles. The fingerprints of PAHs in the samples from topsoil (0–30 cm) in the same profiles were similar and were obviously different from those at greater depth, suggesting that PAH sources were consistent in topsoil samples and were discriminating between topsoil and deeper soils. PAHs in topsoil mainly arose from mixed sources of combustion of liquid fuel, coal, and/or wood, as well as wastewater irrigation, while those at greater depth were derived from soil genesis and the process of soil formation.