Response of C:N:P stoichiometry to long-term drainage of peatlands: Evidence from plant, soil, and enzyme.

Drought induced by climate warming and human activities regulates carbon (C) cycling of peatlands by changing plant community composition and soil properties. Estimating the responses of peatlands C cycling to environmental changes requires further study of C: nitrogen (N): phosphorus (P) stoichiometric ratios of soil, plants, and enzyme activities. However, systematic studies on the stoichiometry of above-ground and below-ground ecosystems of peatlands post drainage remain scarce. This study compared stoichimetric ratios of plant and soil and stoichimetric ratios of enzyme activities with different functions in two different parts of a minerotrophic peatland, a natural undisturbed part and a part that had been drained for almost 50 years, in Northern China. For the shrub plants, the average C:N:P ratios of leaf in natural and drained peatland were 448:17:1 and 393:15:1, respectively. This indicated that the growth rate of shrub plants is higher in the drained peatland than in the natural peatland, which makes P element more concentrated in the photosynthetic site. However, from the perspective of the dominant plant, the mean C:N:P ratio of Carex leaf was 650:25:1 in the natural peatland, but was 1028:50:1 for Dasiphora fruticosa in drained peatland. This indicated that the intensification of P-limitation of plant growth after drainage. Soil C:N:P ratios of above water table depth (AWT) were 238:15:1 and 277:12:1, but were 383:17:1 and 404:19:1 for below water table depth (BWT) in the natural and the drained peatland, respectively. Soil C:P ratios were greater than the threshold elemental ratio of C:P (174:1), but the soil C:N ratios were less than the threshold elemental ratio of C:N (23:1), which suggested that P was the most limiting nutrient of soil. The soil microbial activities were co-limited by C&P in Baijianghe peatlands. However, the microbial metabolic P limitation was intensified, but the C limitation was weakened for the above water table depth soil after long-term drainage. There are connection between plant-microbe P limitation in peatlands. The P limitation of microbial metabolism was significant positively correlated with soil C:N but negatively with soil moisture. The increase in the lignocelluloses index suggested considerable decomposition of soil organic matter after peatland drainage. These results of stoichiometric ratios from above- to below ground could provide scientific base for the C cycling of peatland undergone climate change.

[Effects of Conservation Tillage on Herbicide Residues in Maize Field Soil].

It is well known that conservation tillage can improve soil quality, such as soil organic matters. However, limited information on the conservation tillage impacts on pesticides has been reported, which is important to food security. To explore the specific effects of conservation tillage on herbicide residues in soils, parallel soil samples from seven sites under traditional tillage and conservation tillage were collected, respectively, in Jilin Province, Northeast China. The soil properties and characteristics of three herbicides(acetochlor, atrazine, and MCPA-Na) were measured. The results showed that conservation tillage significantly increased total organic carbon(TOC) content, soil water content, and the average particle size of soil aggregates[(2.1±0.1)%, (19.1±1.2)%, and (82.2±3.0) µm increased to(2.9±0.3)%, (22.3±1.5)%, and (97.2±4.2) µm, respectively]. The results also showed that different herbicides were correlated with different soil properties. For example, TOC content and soil water content were positively correlated with atrazine, whereas micro-aggregate content was negatively correlated with acetochlor. Therefore, the effects of conservation tillage on the three herbicide residues were different. For instance, conservation tillage significantly increased the residual amount of atrazine[from(3.8±0.3) ng·g-1 to (17.7±3.0) ng·g-1] in the Dongfeng site by increasing TOC content, whereas it significantly reduced the residual amount of acetochlor[from (50.6±10.3) ng·g-1 to (9.2±2.5) ng·g-1] in the Dehui site by increasing the average particle size of soil aggregates. Generally, this study suggests conservation tillage indeed affected herbicide residues in soils by affecting soil properties. However, the influence of conservation tillage on herbicide residue was dependent on the types of herbicides due to the complex effects of different soil properties on herbicide migration and degradation.

Cobalt and nitrogen co-doped monolithic carbon foam for ultrafast degradation of emerging organic pollutants via peroxymonosulfate activation.

Cobalt-based catalysts are expected as one of the most promising peroxymonosulfate (PMS) activators for the removal of organic pollutants from industrial wastewater. However, the easy agglomeration, difficult separation, and secondary pollution of cobalt ions limit their practical application. In this study, a novel, highly efficient, reusable cobalt and nitrogen co-doped monolithic carbon foam (Co-N-CMF) was utilized to activate PMS for ultrafast pollutant degradation. Co-N-CMF (0.2 g/L) showed ultrafast catalytic kinetics and higher total organic carbon (TOC) removal efficiency. Bisphenol A, ciprofloxacin, 2,4-dichlorophenoxyacetic acid, and 2,4-dichlorophenol could be completely degraded after 2, 4, 5, and 5 min, and the TOC removal efficiencies were 77.4 %, 68.9 %, 72.8 %, and 79.8 %, respectively, corresponding to the above pollution. The sulfate radical (SO4•-) was the main reactive oxygen species in Co-N-CMF/PMS based on electron paramagnetic resonance. The ecological structure-activity relationship program analysis via the quantitative structure activity relationship analysis and phytotoxicity assessment revealed that the Co-N-CMF/PMS system demonstrates good ecological safety and ecological compatibility. The Co-N-CMF catalyst has good catalytic activity and facile recycling, which provides a fine method with excellent PMS activation capacity for 2,4-dichlorophenol elimination from simulated industrial wastewater. This study provides new insights into the development of monolithic catalysts for ultrafast wastewater treatment via PMS activation.

Does Shift in Vegetation Abundance After Nitrogen and Phosphorus Additions Play a Key Role in Regulating Fungal Community Structure in a Northern Peatland?

Soil fungal communities are key players in biogeochemical processes of peatlands, which are important carbon stocks globally. Although it has been elucidated that fungi are susceptible to environmental changes, little is known about the intricate and interactive effect of long-term nitrogen (N) and phosphorus (P) enrichment on fungal community structure in northern peatlands. In this study, we compared a short- (2 years) with a long-term (10 years) fertilization experiment in a peatland complex in northeastern China to assess how N and/or P additions influence fungal community structure. The results showed that fungal community composition and diversity were altered by N addition, without a significant interactive effect with P addition. Not only the long-term but also the short-term nutrient addition could change the abundance of different plant functional types. However, there were no strong cascading effects on the fungal community in any of the fertilization experiments. Long-term nutrient addition showed a stronger effect on the relative abundance of different fungal functional guilds; an increase in the relative abundance of saprotrophs after fertilization did not jeopardize mycorrhizal fungi. Moreover, the decline in Sphagnum cover after long-term N addition did not parallel changes in the relative abundance of Sphagnum-associated fungi (Clavaria sphagnicola, Galerina tibiicystis, G. sphagnicola, and G. paludosa). Given that short- and long-term fertilization showed strongly contrasting effects on fungal community structure, our study highlights the necessity of assessing the long-term effects of nutrient enrichment on the association between vegetation and fungal community in peatland ecosystems. Future research priorities should emphasize the connection between the community structure of fungal functional guilds and their functionality, which is of paramount importance to better understand their influences on C storage in the face of uncertain N and P deposition regimes.

The temporal distribution of platinum group elements (PGEs) in PM2.5.

In this paper, Changji, Xinjiang, northwest China, was selected as the study area, and platinum group elements (PGEs) in PM2.5 were quantified by ICP-MS using microwave digestion. The results indicated that the average concentrations (and range) of Rh, Pd, and Pt in PM2.5 were 0.21 (n.d. -1.41) ng/m3, 8.09 (n.d. -59.50) ng/m3, and 0.12 (n.d. -0.83) ng/m3, respectively. The concentration of Pd was significantly higher than Rh and Pt. Moreover, the seasonal variations of Rh and Pd were the same: highest in summer and lower in other seasons. However, the seasonal variation of Pt was opposite to that of Rh and Pd: highest in winter and lower in other seasons. Seasonal differences in emission sources of PGEs and the climatic characteristics of arid regions played important roles in the seasonal changes of PGEs. Rh and Pd had a common source and similar diurnal variation. The major influencing factors were traffic volume and meteorological conditions. The diurnal variation regularity of Pt was different from Rh and Pd. The superimposed effect of vehicle exhaust emissions and coal-fired emissions was the main reason why the diurnal variation of Pt was more complicated than those of Rh and Pd. The diurnal concentration of Pt varied with the seasons. It is caused by seasonal coal combustion and meteorological conditions.

Induced defense and its cost in two bryophyte species.

PREMISE: Current knowledge about defense strategies in plants under herbivore pressure is predominantly based on vascular plants. Bryophytes are rarely consumed by herbivores since they have ample secondary metabolites. However, it is unknown whether bryophytes have induced defenses against herbivory and whether there is a trade-off between growth and defense in bryophytes. METHODS: In an experiment with two peatland bryophytes, Sphagnum magellanicum Brid. and S. fuscum (Schimp.) H. Klinggr., two kinds of herbivory, clipping with scissors and grazing by mealworms (Tenebrio molitor L.) were simulated. At the end of the experiment, we measured growth traits, carbon-based defense compounds (total phenolics and cellulose) and storage compounds (total nonstructural carbohydrates) of these two Sphagnum species. RESULTS: Grazing but not clipping increased total phenolics and C:N ratio and reduced biomass production and height increment. A negative relationship between biomass production and total phenolics was found in S. magellanicum but not in S. fuscum, indicating a growth-defense trade-off that is species-specific. Grazing reduced the sugar starch content of S. magellanicum and the sugar of S. fuscum. Either clipping or grazing had no effect on chlorophyll fluorescence (including actual and maximum photochemical efficiency of photosystem II) except that a significant effect of clipping on actual photochemical efficiency in S. fuscum was observed. CONCLUSIONS: Our results suggest that Sphagnum can have induced defense against herbivory and that this defense can come at a cost of growth. These findings advance our knowledge about induced defense in bryophytes, the earliest land plants.

Effects of drainage on dissolved organic carbon (DOC) characteristics of surface water from a mountain peatland.

Dissolved organic carbon (DOC) plays an important role in regulating the carbon cycles in the peatland. In this study, we collected surface water once or twice a month from natural and drained areas of peatland in the Changbai Mountain, northeastern China, and determined the concentrations, spectral information, and composition of DOC, as well as the concentrations of other elements. The results showed that the concentrations of total N and NH4+ in the drained area were significantly higher than those in the natural area in most cases, but concentrations of total dissolved Fe were significantly lower. The DOC concentrations in the natural and drained area ranged from 31.0 mg L-1 to 320.8 mg L-1 and from 33.2 mg L-1 to 105.8 mg L-1, respectively. It is shown that DOC concentration in the drained area was generally lower than those in the natural area in mid-growing season, but it was higher in early- and end-growing seasons. SUVA254 (Abs254/DOC concentration) in the drained area was generally higher than in the natural area, indicating more aromatic DOC fraction in drained area. No consistent difference in other spectroscopy was observed between natural and drained areas. In contrast, molecular analysis of DOC not only confirmed an increase in the fraction of aromatic compounds in DOC but also showed different compositions of DOC between the natural and drained areas on molecular level, suggesting enhanced decomposition of peat organic matters after drainage. Notably, the average percentage of protein-like structures in DOC in drained area was significantly higher than that in natural area (14.9 ± 1.7% vs. 12.8 ± 0.8%), indicating preferential release of dissolved organic nitrogen from peat organic matter. Overall, this study suggests drainage can enhance decomposition of peat organic matters, resulting in more protein-like structures released into water.

Response of palladium in receiving water bodies to rainfall-runoff.

Palladium (Pd) is widely used in automotive catalytic converters to reduce toxic gas emissions. The input of Pd in the rainfall-runoff is an important contributing factor to the accumulation of Pd in receiving water bodies. In this study, the Meishe River in Haikou, Hainan Province, China, was used as the research area, and palladium (Pd) was selected as the target pollutant. This study explored the response of Pd in the receiving water body to rainfall-runoff and to analyze the influencing factors. The results showed that the dissolved Pd concentration in the receiving water body had a corresponding relationship with that in rainfall-runoff. The response of suspended Pd in the receiving water body to rainfall-runoff was closely related to the location of the drainage outlet. Compared with that of suspended Pd, the response of dissolved Pd in the receiving water body to that in the rainfall-runoff was more obvious. Seven meters downstream from the outfall was the most sensitive response distance of dissolved Pd in receiving water bodies to rainfall-runoff, and the response time was approximately 0-10 min. The suspended Pd at 3 m downstream from the outfall also had a certain response to the rainfall-runoff, and the response time was approximately 15-25 min. The response time of the suspended Pd in the receiving water body depended largely on the first flush ability of the runoff. There was a moderately positive correlation between the dissolved Pd and Cl- in the receiving water body (r = 0.687; p < 0.05). The effects of pH, Eh, and total suspended solids (TSS) on suspended Pd were reduced in the response process of the receiving water body. The synergistic effect of multiple factors increased the uncertainty of the Pd response.

Shift in nitrogen transformation in peatland soil by nitrogen inputs.

Inputs of nitrogen (N) to peatlands in the form of fertilizers have rapidly increased due to the intensification of agricultural systems, impacting ecological processes, and the carbon storage function of peatland. However, detailed information on the impacts of long-term N inputs on the individual steps of N transformation processes in peatland soils still needs to be fully understood. We investigated N mineralization and nitrification rates as well as nitrite dependent anaerobic methane oxidation (n-damo), anaerobic ammonium oxidation (anammox), denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) in a peatland affected by N inputs for >50 years, using isotope tracing technique and quantitative PCR. Based on the results, N inputs increased N mineralization and nitrification rates by 77 and 43%, respectively. Notably, the contributions of n-damo and anammox to N2 production were enhanced by 242 and 170%, accounting for 30 and 12%, respectively. The contributions of denitrification and DNRA to N2 production decreased by 27 and 52%, accounting for 48 and 10% of N2 production, respectively. Nitrifier abundance increased significantly, with AOA being the dominant prokaryote (from 696 to 1090 copies g-1), but AOB responded more strongly to N inputs (from 5 to 68 copies g-1). The N inputs also promoted the growth of n-damo and anammox bacteria, whose abundances increased by 3.7% (from 565 to 586 copies g-1) and 85.7% (from 305 to 567 copies g-1), respectively, while denitrifier abundance was significantly reduced, with nirK and nirS abundances decreasing by 58% (from 738 to 308 copies g-1) and 50% (from 218 to 109 copies g-1), respectively. Soil pH was the key environmental factor influencing N transformations. We show that n-damo plays important roles in N cycling in peatland subjected to N inputs, providing a scientific basis for improved peatland management.

Characteristics of polycyclic aromatic hydrocarbons (PAHs) in soil horizon from high-altitude mountains in Northeastern China.

Previous studies have reported that soils from high altitude mountains act as primary reservoirs of polycyclic aromatic hydrocarbons (PAHs). This study aims to investigate the spatial distribution and illuminate the behaviors of PAHs in soil profiles from Mt. Wangtiane in Northeastern China. Soil samples were collected by different soil genetic horizon rather than by depths at 10 sites, with altitudes from 1000 m to 2022 m. Results showed significantly (p < 0.05) higher concentrations of total PAHs (16 PAHs) in O-horizons (371 ±â€¯32 to 2224 ±â€¯207 ng g-1) than those in A- and B-horizons (362 ±â€¯30 to 666 ±â€¯58 ng-1 and 289 ±â€¯23 to 571 ±â€¯50 ng g-1, respectively). An increasing trend of PAH concentrations with altitude was observed from elevation ca. 1000 m to ca. 1800 m, but no correlation between PAH concentrations and altitude along transect was found. Total organic carbon (TOC) was strongly correlated (p < 0.05) with PAH concentrations in O-horizons but showed no relation with those in A- and B-horizons. Low molecular weight (LMW) PAHs were dominated in each soil horizon, and decreased percentage of high molecular weight (HMW) PAHs with depths in soils profiles was observed. Principle component analysis (PCA) separated O-horizons and A-/B-horizons based on PAH compositions, again suggesting different PAH compositions among soil horizons. These results reflect various processes of PAHs, including deposition, vertical motion, degradation and photolysis. This study suggests it is better to investigate characteristics of PAHs in soils by horizon rather than by depths.

Mercury and arsenic in the surface peat soils of the Changbai Mountains, northeastern China: distribution, environmental controls, sources, and ecological risk assessment.

The potential toxic risk of mercury (Hg) and arsenic (As) in the soils of mining regions and other artificially disturbed lands receives considerable research attention. However, limited investigation has been conducted into the surface soils of natural globally distributed ecosystems, for example peatlands. In this study, we examine the distribution, controlling factors, sources, and potential ecological risks of Hg and As in 96 samples from 42 peatlands in the Changbai Mountains of northeastern China. The results showed that average concentrations (dry weight) of Hg and As at the samples sites were 169.1 ± 0.1 µg kg-1 and 13.0 ± 7.7 mg kg-1, respectively. The distribution of Hg is largely determined by latitude and altitude, while As is controlled more by pH, total organic carbon (TOC), and ratio of TOC and nitrogen (C/N) at the regional scale. Variations in TOC, C/N ratio, and redox conditions contribute to determining the distribution of Hg, while TOC and redox conditions mainly affected the distribution of Arsenic at the local scale. Mercury mostly comes from regional atmospheric wet deposition, whereas elevated concentrations of As are related to local anthropogenic activities. Overall, Hg and As in the peatlands of the Changbai Mountains pose a moderate level of potential risk to ecological health.

Degradation of polycyclic aromatic hydrocarbons (PAHs) during Sphagnum litters decay.

The dynamics of polycyclic aromatic hydrocarbon (PAH) degradation in Sphagnum litters and the decomposition of the litters were investigated. PAH concentration decreased to approximately half of the initial concentration as Sphagnum litters decayed. The initial PAH concentration was 489.2 ± 72.2 ng g-1, and the concentration after 120 days of incubation was 233.0 ± 5.8 ng g-1. The different PAH compositions changed concentrations at different times. The low-molecular-weight (LMW) and high-molecular-weight (HMW) PAHs started to be degraded after incubation and after 40 days of incubation, respectively. PAH concentrations in the Sphagnum litters correlated with the total organic carbon (TOC) content (p < 0.05), indicating that PAHs were associated with the TOC of the Sphagnum litters and were degraded as organic matter decayed. The positive relationship between LMW PAH concentration and the soluble carbohydrate content (p < 0.05) indicated that LMW PAHs and the readily decomposed organic carbon fractions were cometabolized, or that LMW PAHs were mainly absorbed by soluble carbohydrate. The weak negative correlation between fulvic acid (FA) and PAH concentrations (p < 0.1) indicated that FA may enhance PAH degradation. Redundancy analysis suggested that the contents of both soluble carbohydrate and cellulose significantly affected the changes in PAH concentrations (p < 0.05), and that FA content and C/N ratios may also contribute to the changes in PAH concentrations (p < 0.1). However, the polyphenol that was related to microbial activities was not associated with changes in PAH concentrations. These results suggested that litter quality is more important than microbial activities in PAH degradation in Sphagnum litters.

Assessment of polycyclic aromatic hydrocarbons in indoor dust from varying categories of rooms in Changchun city, northeast China.

Sixteen polycyclic aromatic hydrocarbons (PAHs) were isolated from indoor dust from various categories of rooms in Changchun city, northeast China, including dormitory, office, kitchen, and living rooms. PAH concentrations ranged from 33.9 to 196.4 µg g-1 and 21.8 to 329.6 µg g-1 during summer and winter, respectively, indicating that total PAH concentrations in indoor dust are much higher than those in other media from the urban environment, including soils and sediments. The percentage of five- to six-ring PAHs was high, indicating that PAHs found in indoor dust mainly originate from pyrolysis rather than a petrogenic source. Rooms were divided into three groups using cluster analysis on the basis of 16 PAH compositions, namely smoke-free homes, homes exposed to smoke and offices. Results showed that the source of PAHs in smoke-free residential homes is primarily the burning of fossil fuels. In addition to the burning of fossil fuels, biomass combustion and cooking contributed to PAHs in houses exposed to smoke (including kitchens). Motor vehicles are an additional source of PAHs in offices because of greater interactions with the outdoor environment. The results of health risk assessment showed that the cancer risk levels by dermal contact and ingestion are 104- to 105-fold higher than that by inhalation, suggesting that ingestion and dermal contact of carcinogenic PAHs in dust are more important exposure routes than inhalation of PAHs from air. Although the results showed high potential of PAH concentrations in indoor dust in Changchun for human health risk, caution should be taken to evaluate the risk of PAHs calculated by USEPA standard models with default parameters because habitation styles are different in various categories of rooms.

The impact of drying on structure of sedimentary organic matter in wetlands: Probing with native and amended polycyclic aromatic hydrocarbons.

Wetland sediments undergo dry-wet cycles that may change their structural properties and affect geochemical behavior of associated organic compounds. In this study, we examined the effect of drying on particle size distributions and the rapid (24h) sorption reactions of polycyclic aromatic hydrocarbons (PAHs) with salt marsh sediments in Nueces Delta, South Texas. Drying reduced the fraction of fine particles in organically richer sediments, indicating structural rearrangement of organic matter and mineral aggregates. Among the 16 EPA priority PAHs examined, dried sediment preferentially released 1.0-7.5% of phenanthrene, fluoranthene and pyrene to added seawater (solid: water mass ratio of 1/100) - significantly greater than release from sediments maintained in the wet state. On the other hand, drying also increased the affinity of sedimentary organic matter (SOM) for experimentally amended (deuterated) phenanthrene relative to continually wet sediments. Further, deuterated phenanthrene was even more effectively retained when it was added to wet sediment that was subsequently dried and rewetted. These apparently contradictory results can be reconciled and explained by SOM having a heterogeneous distribution of hydrophobic and hydrophilic zones - e.g., a zonal model. We propose that drying changed the orientation of amphiphilic SOM, exposing hydrophobic zones and promoting the release of some of their native PAHs to water. Freshly amended PAHs were only able to penetrate into the surface hydrophobic zone and/or deeper but rapidly accessible ("kinetic") zone in wet sediments due to the brief adsorption contact time. Subsequent drying presumably then induced structural changes in SOM that isolated these amended PAHs in sites inaccessible to water exchange in the next rewetting. These results provide insights into structural changes of SOM upon drying, and help predict the fate of compounds such as organic contaminants during drought/flood oscillations.

Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico.

BACKGROUND: Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5 cm) of the northern Gulf of Mexico. RESULTS: PAH concentrations in this region ranged from 100 to 856 ng g-1, with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5-6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments. CONCLUSION: PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels.

Effects of crude oil exposure on bioaccumulation of polycyclic aromatic hydrocarbons and survival of adult and larval stages of gelatinous zooplankton.

Gelatinous zooplankton play an important role in marine food webs both as major consumers of metazooplankton and as prey of apex predators (e.g., tuna, sunfish, sea turtles). However, little is known about the effects of crude oil spills on these important components of planktonic communities. We determined the effects of Louisiana light sweet crude oil exposure on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in adult stages of the scyphozoans Pelagia noctiluca and Aurelia aurita and the ctenophore Mnemiopsis leidyi, and on survival of ephyra larvae of A. aurita and cydippid larvae of M. leidyi, in the laboratory. Adult P. noctiluca showed 100% mortality at oil concentration ≥20 µL L(-1) after 16 h. In contrast, low or non-lethal effects were observed on adult stages of A. aurita and M. leidyi exposed at oil concentration ≤25 µL L(-1) after 6 days. Survival of ephyra and cydippid larva decreased with increasing crude oil concentration and exposition time. The median lethal concentration (LC50) for ephyra larvae ranged from 14.41 to 0.15 µL L(-1) after 1 and 3 days, respectively. LC50 for cydippid larvae ranged from 14.52 to 8.94 µL L(-1) after 3 and 6 days, respectively. We observed selective bioaccumulation of chrysene, phenanthrene and pyrene in A. aurita and chrysene, pyrene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]anthracene in M. leidyi. Overall, our results indicate that (1) A. aurita and M. leidyi adults had a high tolerance to crude oil exposure compared to other zooplankton, whereas P. noctiluca was highly sensitive to crude oil, (2) larval stages of gelatinous zooplankton were more sensitive to crude oil than adult stages, and (3) some of the most toxic PAHs of crude oil can be bioaccumulated in gelatinous zooplankton and potentially be transferred up the food web and contaminate apex predators.

Interactions between zooplankton and crude oil: toxic effects and bioaccumulation of polycyclic aromatic hydrocarbons.

We conducted ship-, shore- and laboratory-based crude oil exposure experiments to investigate (1) the effects of crude oil (Louisiana light sweet oil) on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in mesozooplankton communities, (2) the lethal effects of dispersant (Corexit 9500A) and dispersant-treated oil on mesozooplankton, (3) the influence of UVB radiation/sunlight exposure on the toxicity of dispersed crude oil to mesozooplankton, and (4) the role of marine protozoans on the sublethal effects of crude oil and in the bioaccumulation of PAHs in the copepod Acartia tonsa. Mortality of mesozooplankton increased with increasing oil concentration following a sigmoid model with a median lethal concentration of 32.4 µl L(-1) in 16 h. At the ratio of dispersant to oil commonly used in the treatment of oil spills (i.e. 1∶20), dispersant (0.25 µl L(-1)) and dispersant-treated oil were 2.3 and 3.4 times more toxic, respectively, than crude oil alone (5 µl L(-1)) to mesozooplankton. UVB radiation increased the lethal effects of dispersed crude oil in mesozooplankton communities by 35%. We observed selective bioaccumulation of five PAHs, fluoranthene, phenanthrene, pyrene, chrysene and benzo[b]fluoranthene in both mesozooplankton communities and in the copepod A. tonsa. The presence of the protozoan Oxyrrhis marina reduced sublethal effects of oil on A. tonsa and was related to lower accumulations of PAHs in tissues and fecal pellets, suggesting that protozoa may be important in mitigating the harmful effects of crude oil exposure in copepods and the transfer of PAHs to higher trophic levels. Overall, our results indicate that the negative impact of oil spills on mesozooplankton may be increased by the use of chemical dispersant and UV radiation, but attenuated by crude oil-microbial food webs interactions, and that both mesozooplankton and protozoans may play an important role in fate of PAHs in marine environments.

Distribution of PAHs in tissues of wetland plants and the surrounding sediments in the Chongming wetland, Shanghai, China.

Polycyclic aromatic hydrocarbons (PAHs) concentrations were determined in sediments and three types of wetland plants collected from the intertidal flats in the Chongming wetland. The concentration of total PAHs in sediments ranged from 38.7 to 136.2 ngg(-1). Surface sediment concentrations were higher in regions with plant cover than in bare regions. Rhizome-layer sediments (56.8-102.4 ngg(-1)) contained less PAHs than surface sediments (0-5 cm). Concentrations of PAHs in plant tissues ranged from 51.9 to 181.2 ngg(-1), with highest concentrations in the leaves of Scirpus. Most of the PAHs in the leaves and other plant tissues were low molecular weight compounds (LMW, 2-4 rings), and a similar distribution pattern of PAHs in different types of plants was also observed. Source analysis indicated that plants and sediments both came from pyrogenic sources, but plants had additional petroleum contamination. The low ratio of benzo[a]anthracene over chrysene suggests that the wetland PAHs came mainly from long-distance atmospheric transportation. Significant bioaccumulation of PAHs from the sediments into plants was not observed for high molecular weight PAHs (HMW, 5-6 rings) in Chongming wetland. The small RCFs (root concentration factor from sediments) for HMW PAHs and large RCFs for LMW PAHs suggested that roots accumulated LMW PAHs selectively from sediments in Chongming wetland.

Multiple 'hits' during postnatal and early adulthood periods disrupt the normal development of sensorimotor gating ability in rats.

In the present study, we evaluated a multiple-hit animal model of schizophrenia in an attempt to capture the complex interactions among various adverse developmental factors in schizophrenia. Sprague-Dawley rats were assigned to receive either repeated daily 3-h maternal separation for eight days (first 'hit') on postnatal days (PND) 3 to 10, and/or avoidance conditioning for six days (second 'hit') on PND 49-56, and/or repeated phencyclidine treatment (third 'hit', 3.0 mg/kg, sc) immediately after each daily avoidance conditioning. Prepulse inhibition (PPI) of acoustic startle reflex was assessed at late adolescence (PND 41-43) and early adulthood (PND 62-63). The change in %PPI from the adolescence phase to adulthood phase was used to index the maturation-related improvement of sensorimotor gating ability. Maternal separation, avoidance conditioning and PCP treatment had a complex three-way interaction on the functional improvement of sensorimotor gating. Maternal separation impaired PPI improvement preferentially in the saline rats that were not subjected to avoidance conditioning. Avoidance conditioning had no effect on PPI improvement in the non-maternally separated rats, but restored the maternal separation-induced disruption. However, this restoration effect was abolished by PCP treatment. The present study also identified a number of behavioral, emotional and learning abnormalities caused by these three developmental insults which may precede their interactive disruption of normal development of sensorimotor gating ability.