Spatiotemporal distributions and relationships of phosphorus content, phosphomonoesterase activity, and bacterial phosphomonoesterase genes in sediments from a eutrophic brackish water lake in Chile.

Phosphorus (P) cycling by microbial activity is highly relevant in the eutrophication of lakes. In this context, the contents of organic (Po) and inorganic (Pi) phosphorus, the activity of acid (ACP) and alkaline (ALP) phosphomonoesterase (Pase), and the abundances of bacterial Pase genes (phoD, phoC, and phoX) were studied in sediments from Budi Lake, a eutrophic coastal brackish water lake in Chile. Our results showed spatiotemporal variations in P fractions, Pase activities, and Pase gene abundances. In general, our results showed higher contents of Pi (110-144 mg kg-1), Po (512-576 mg kg-1), and total P (647-721 mg kg-1) in sediments from the more anthropogenized sampling sites in summer compared with those values of Pi (86-127 mg kg-1), Po (363-491 mg kg-1) and total P (449-618 mg kg-1) in less anthropogenized sampling sites in winter. In concordance, sediments showed higher Pase activities (µg nitrophenyl phosphate g-1 h-1) in sediments from the more anthropogenized sampling sites (9.7-22.7 for ACP and 5.9 to 9.6 for ALP) compared with those observed in less anthropogenized sampling sites in winter (4.2-12.9 for ACP and 0.3 to 6.7 for ALP). Higher abundances (gene copy g-1 sediment) of phoC (8.5-19 × 108), phoD (9.2-47 × 106), and phoX (8.5-26 × 106) genes were also found in sediments from the more anthropogenized sampling sites in summer compared with those values of phoC (0.1-1.1 × 108), phoD (1.4-2.4 × 106) and phoX (0.7-1.2 × 106) genes in the less anthropogenized sites in winter. Our results also showed a positive correlation between P contents, Pase activities, and abundances of bacterial Pase genes, independent of seasonality. The present study provided information on the microbial activity involved in P cycling in sediments of Budi Lake, which may be used in further research as indicators for the monitoring of eutrophication of lakes.

Heavy metal pollution in coastal wetlands: A systematic review of studies globally over the past three decades.

Coastal wetlands are ecosystems lying between land and ocean and are subject to inputs of heavy metals (HMs) from terrestrial, oceanic and atmospheric sources. Although the study on HM pollution in coastal wetlands has been rapidly developing over the past three decades, systematic reviews are still unavailable. Here, by analyzing 3343 articles published between 1990 and 2019, we provided the first holistic systematic review of studies on HM pollution in coastal wetlands globally. The results showed a trend of rapid increases in publications in this field globally, especially over the past ten years. Trends varied greatly among coastal countries, and global trends were primarily driven by the US before 2000, and in China after 2010. We also found that mercury (Hg), cadmium (Cd), and copper (Cu) were the most widely studied HM elements globally, but patterns differed geographically, with Hg being most widely examined in the Americas, Cd in China and India, and lead (Pb) in the western Europe and Australia, respectively. Among different types of coastal wetlands, salt marshes, mangrove forests, and estuaries were the most widely studied, in contrast to seagrass beds and tidal flats. As for ecosystem components, soils/sediments and plants were most extensively investigated, while algae, microbes, and animals were much less examined. Our analysis further revealed rapid emergence of topics on anthropogenic sources, interactions with other anthropogenic environmental changes (climate change in particular), and control and remediation methodology in the literature in the recent ten years. Moving forward, we highlight that future studies are needed to i) better understand the impacts of HM pollution in less studied coastal wetland systems and species, ii) deepen current understanding of the biogeochemical behaviors of HMs under anthropogenic activities, iii) examine interactions with other anthropogenic environmental changes, iv) conceive ecological remediation (i.e., "ecoremediation" as compared to traditional physiochemical remediation and bioremediation) strategies, and v) develop advanced analysis instruments and methods. The perspectives we brought forward can help stimulate many new advances in this field.

Dynamics of phosphorus fractions and potential bioavailability along soil profiles from seasonal-flooding wetlands in a Chinese estuary.

Soil phosphorus fractions in wetland ecosystems have received increasing attention due to its high eutrophication risks. Soil samples were collected to 40 cm depth in three sampling seasons to investigate the seasonal dynamics of organic and inorganic phosphorus fractions, bioavailability, and relationship between those and soil properties in a seasonal-flooding wetland in the Yellow River Estuary. The results showed that inorganic phosphorus (IP) and organic phosphorus (OP) contents exhibited much higher levels in the top 10 cm soils, and declined along soil profiles in spring. IP kept constant along soil profiles in fall, while OP decreased in summer and fall. They were greatly affected by water content (WC), pH, Cl-/SO42-, soil organic matter (SOM), and electrical conductivity (EC). Middle labile organic phosphorus (MLOP) and non-labile organic phosphorus (NLOP) accounted for higher percentages of total OP in summer and fall respectively than labile organic phosphorus (LOP) in spring. MLOP and NLOP levels showed a decrease along soil profiles in spring and in spring/fall, respectively, while NLOP significantly increased with depth in summer. Ca-P was the dominant IP fraction in all soils in three sampling seasons, declined with depth in spring/fall and increased in summer. Comparatively, soluble/loosely-P(S/L-P) generally decreased with depth along soil profiles in three sampling seasons. And residual P (Res-P) kept little change with depth in spring. Fe/Al-P levels decreased firstly and then increased with depth in spring and summer. Available phosphorus and potential bioavailable phosphorus contents decreased with depth in spring and summer not in fall, and had a strong significant positive correlation with WC and SOM. Alkaline phosphatase not acid phosphatase was the key factor influencing soil MLOP levels. Generally, the fractions and bioavailability of phosphorus as well as phosphatase in this region were affected by soil depth, sampling seasons, and soil properties (e.g., WC, pH, Cl-/SO42-, SOM, and EC).

Phosphorus alleviation of nitrogen-suppressed methane sink in global grasslands.

Grassland ecosystems account for more than 10% of the global CH4 sink in soils. A 4-year field experiment found that addition of P alone did not affect CH4 uptake and experimental addition of N alone significantly suppressed CH4 uptake, whereas concurrent N and P additions suppressed CH4 uptake to a lesser degree. A meta-analysis including 382 data points in global grasslands corroborated these findings. Global extrapolation with an empirical modelling approach estimated that contemporary N addition suppresses CH4 sink in global grassland by 11.4% and concurrent N and P deposition alleviates this suppression to 5.8%. The P alleviation of N-suppressed CH4 sink is primarily attributed to substrate competition, defined as the competition between ammonium and CH4 for the methane mono-oxygenase enzyme. The N and P impacts on CH4 uptake indicate that projected increases in N and P depositions might substantially affect CH4 uptake and alter the global CH4 cycle.

Leaf metabolites profiling between red and green phenotypes of Suaeda salsa by widely targeted metabolomics.

The Chenopodiaceae Suaeda salsa (L.) Pall. is a traditional Chinese medicine and food with green and red phenotypes in the Yellow River Delta. We identified 521 metabolites using widely targeted metabolomics, of which 165 were selected as significantly differential metabolites which could be related to the leaf traits of different phenotypes of S. salsa. Two anthocyanins (i.e. cyanidin O-acetylhexoside and delphinidin-3-O-(6'-O-α-rhamnopyranosy l-ß-glucopyranoside)) were responsible for red colour in red leaves of S. salsa. Gallic acid, which existed only in red one, was the main reason for leaf succulence. D-arabitol and ribitol were two significantly upregulated carbohydrates in red phenotype. Four alkaloids (i.e. harmaline, aminophylline, pipecolate and trigonelline) were upregulated in red leaves. Hormonal changed involved a decrease in indoleacetic acid-valine (IAA-Val), N6-isopentenyladenosine-5'-monophosphate (iPRMP), isopentenyladenineriboside (iPR), trans-abscisic acid (S-ABA), salicylic acid O-hexoside, methyl jasmonate, N6-isopentenyladenine (iP), trans-zeatin riboside-O-glucoside iso2, trans-zeatin riboside-O-glucoside, and a tendency for dihydrozeatin 9-O-glucoside (DZ9G) down accumulation. In addition, the regulation of amino acids and lipids also contributed to the adaptation of red phenotype to harsh environment. Generally, our findings provide a comprehensive comparison of the metabolites between two phenotypes of S. salsa and an interpretation of phenotypic differences from the point of metabolomics.

In-situ organic phosphorus mineralization in sediments in coastal wetlands with different flooding periods in the Yellow River Delta, China.

In-situ incubation experiments were performed in typical tidal flooding wetlands and seasonal flooding wetlands in the Yellow River Delta of China to investigate sediment organic phosphorus (OP) mineralization and its influencing factors. The results showed that the sediment net P mineralization rate (RNPM) exhibited consistent seasonal variations in both wetlands, and it was more stable in the tidal flooding wetlands than in the seasonal flooding wetlands. Sediment P mineralization was greatly influenced by plant uptake and flooding erosion, and the freshwater input by flow-sediment regulation replenished the inorganic phosphorus (IP) pool in the wetland sediments. The OP, IP and total P in the sediments of the tidal flooding wetlands were in a state of dynamic equilibrium throughout the plant growing season, and plant uptake peaked during the period from August to September. In the seasonal flooding wetlands, rainfall and flow-sediment regulation were the key factors influencing the conversion between OP and IP. Besides sediment salinity and pH, microbial biomass and enzyme activities were also the key factors influencing the sediment RNPM in both wetlands. The findings of this study indicated that flooding frequencies and salinity could highly impact sediment P mineralization, and that the IP levels in sediments might be influenced by wetland hydrology and salinity.

Phosphorus sorption-desorption and effects of temperature, pH and salinity on phosphorus sorption in marsh soils from coastal wetlands with different flooding conditions.

Wetland soils act as a sink or source of phosphorus (P) to the overlaying water due to phosphorus sorption-desorption processes. Litter information is available on sorption and desorption behaviors of phosphorus in coastal wetlands with different flooding conditions. Laboratory experiments were conducted to investigate phosphorus sorption-desorption processes, fractions of adsorbed phosphorus, and the effects of salinity, pH and temperature on phosphorus sorption on soils in tidal-flooding wetlands (TW), freshwater-flooding wetlands (FW) and seasonal-flooding wetlands (SW) in the Yellow River Delta. Our results showed that the freshly adsorbed phosphorus dominantly exists in Occluded-P and Fe/AlP and their percentages increased with increasing phosphorus adsorbed. Phosphorus sorption isotherms could be better described by the modified Langmuir model than by the modified Freundlich model. A binomial equation could be properly used to describe the effects of salinity, pH, and temperature on phosphorus sorption. Phosphorus sorption generally increased with increasing salinity, pH, and temperature at lower ranges, while decreased in excess of some threshold values. The maximum phosphorus sorption capacity (Qmax) was larger for FW soils (256 mg/kg) compared with TW (218 mg/kg) and SW soils (235 mg/kg) (p < 0.05). The percentage of phosphorus desorption (Pdes) in the FW soils (7.5-63.5%) was much lower than those in TW (27.7-124.9%) and SW soils (19.2-108.5%). The initial soil organic matter, pH and the exchangeable Al, Fe and Cd contents were important factors influencing P sorption and desorption. The findings of this study indicate that freshwater restoration can contribute to controlling the eutrophication status of water bodies through increasing P sorption.

Morphological and transcriptional responses of Lycopersicon esculentum to hexavalent chromium in agricultural soil.

The carcinogenic, teratogenic, and mutagenic effects of hexavalent chromium (Cr[VI]) on living organisms through the food chain raise the immediate need to assess the potential toxicological impacts of Cr(VI) on human health. Therefore, the concentration-dependent responses of 12 Cr(VI)-responsive genes selected from a high-throughput Lycopersicon esculentum complementary DNA microarray were examined at different Cr concentrations. The results indicated that most of the genes were differentially expressed from 0.1 mg Cr/kg soil, whereas the lowest-observable-adverse-effect concentrations of Cr(VI) were 1.6 mg Cr/kg soil, 6.4 mg Cr/kg soil, 3.2 mg Cr/kg soil, and 0.4 mg Cr/kg soil for seed germination, root elongation, root biomass, and root morphology, respectively, implying that the transcriptional method was more sensitive than the traditional method in detecting Cr(VI) toxicity. Dose-dependent responses were observed for the relative expression of expansin (p = 0.778), probable chalcone-flavonone isomerase 3 (p = -0.496), and 12S seed storage protein CRD (p = -0.614); therefore, the authors propose the 3 genes as putative biomarkers in Cr(VI)-contaminated soil. Environ Toxicol Chem 2016;35:1751-1758. © 2015 SETAC.

Spatial distribution of inorganic nitrogen contents of marsh soils in a river floodplain with different flood frequencies from soil-defrozen period.

Contents of inorganic nitrogen (NH4(+)-N and NO3(-)-N) in soil profiles were measured in five typical zones ( including permanently flooded floodplain(B), 1-year floodplain (O), 5-year floodplain (F),10-year floodplain (T), and 100-year floodplain (H) )from Huolin River floodplain in Erbaifangzi, Jilin Province of China, in the soil-defrosted period (Mayof 1999). Contour maps and profile maps were constructed to describe the spatial distributions of NH4(+)-N and NO3(-)-N) in order to identify the influences of flood frequencies on them. Results showed that NH4(+)-N generally increased with depth in soil profiles from the five areas, but NH4(+)-N contents in T or H areas significantly differed from those in other areas. For NO3(-)-N, with the exception that there was a significant cumulative peak (6.77 +/- 0.08 mg kg(-1)) at 15-cm depth (10-20 cm) in B area, no significant difference was observed between NO3(-)-N contents in soil profiles from the other four areas. The horizontal distributions of NH4(+)-N and NO3(-)-N in top soils (0-10 cm) were different in the five areas,which were greatly influenced by flood frequencies. The highest content of NH4(+)-N or NO3(-)-N did not appear in B area but in the floodplain with certain flood frequency. For example, NH4(+)-N content (16.81 mg kg-(1)) in 5-year floodplain wetland was highest, and the highest content of NO3(-)-N(1.69 mg kg(-1)) appeared in 1-year floodplain wetland. In addition, NH4(+)-N contents were significantly correlated with soil pH, and NO3(-)-N contents had significant correlation with inorganic carbon, but there were no significant correlations between inorganic nitrogen and other selected soil properties.