Effect of reforestation on nitrogen and phosphorus dynamics in the catchment ecosystems of subtropical China: the example of the Hanjiang River basin.

BACKGROUND: To enable effective management and decision making for the sustainable use of water resources, we successfully integrated factors such as dams, land use and soil properties as well as management factors in the Hanjiang River basin, a subtropical catchment of China, into the SWAT model to simulate water cycles as well as the distribution, movement, and transformations of nutrients. RESULTS: The accuracy of the model was validated by monitoring data over the Hanjiang River. The validated model was then used to evaluate the effects of the Reforestation of Cultivated Land (RFCL) initiative. The simulation results showed that RFCL would cause an obvious decrease in surface runoff (-23.6%, P < 0.01) but an increase in groundwater (71.8%, P < 0.01) and percolation out of the soil (24.7%, P < 0.01). The total water yield does not change significantly (-4.4%), but the decrease in total sediment loading is substantial (-56.2%, P < 0.01). The simulation results also show that RFCL would greatly decrease the organic N (-42.6%, P < 0.01), NO(3) yield in surface flow (-37.1%, P < 0.01), and the NO(3) yield in subsurface flow (-25.5%, P < 0.01), whereas the NO(3) yield in groundwater flow would increase (107%, P < 0.01). In terms of phosphorus, RFCL would cause both organic phosphorus (-38.2%, P < 0.01) and the phosphorus yield from the soil (-33.3%, P < 0.01) to decrease. CONCLUSION: The results suggest that RFCL is an effective policy for watershed environment management, which might have a relatively small effect on river discharge but that the purification effects on water quality in the river would be remarkable.

Quantification of microcystis in a eutrophic lake by simple DNA extraction and SYBR green real-time PCR.

A simple extraction method and real-time PCR with SYBR-Green I were combined to monitor Microcystis 16S rRNA gene (16S rDNA) concentrations over a wide range. A Fast DNA SPIN Kit (MP Biomedicals) was used to extract rDNA quantitatively. Real-time PCR amplified Microcystis rDNA for quantification with the forward primer Micro229f, which was newly designed by us and was highly specific for Microcystis, and the reverse universal primer 342r. The method developed here can detect Microcystis at concentrations as low as 3 cells mL(-1). The rDNA concentration and cell count were highly correlated in the range from 1.2×10(4) to 1.1×10(6) copies mL(-1) and from 9.5×10(2) to 1.0×10(5) cells mL(-1), respectively, in a canal where Microcystis algal blooms occur annually. The Microcystis rDNA concentration in Lake Kasumigaura was measured by the application of our method to water samples collected monthly from April 2004 to March 2006. Microcystis was not detected by microscopy from January to June 2005, except in May, but our method detected 1.0×10(3) to 1.0×10(4) copies mL(-1) of Microcystis rDNA during this period. This result clearly showed that our method is useful for clarifying the annual fluctuation in Microcystis concentration, especially when concentrations are low.

Abundance and population structure of ammonia-oxidizing bacteria that inhabit canal sediments receiving effluents from municipal wastewater treatment plants.

A polyphasic, culture-independent study was conducted to investigate the abundance and population structure of ammonia-oxidizing bacteria (AOB) in canal sediments receiving wastewater discharge. The abundance of AOB ranged from 0.2 to 1.9% and 1.6 to 5.7% of the total bacterial fraction by real-time PCR and immunofluorescence staining, respectively. Clone analysis and restriction endonuclease analysis revealed that the AOB communities influenced by the wastewater discharge were dominated by Nitrosomonas, were similar to each other, and were less diverse than the communities outside of the immediate discharge zone.

Characterization and quantification of ammonia-oxidizing bacteria in eutrophic coastal marine sediments using polyphasic molecular approaches and immunofluorescence staining.

Tokyo Bay, a eutrophic bay in Japan, receives nutrients from wastewater plants and other urban diffuse sources via river input. A transect was conducted along a line from the Arakawa River into Tokyo Bay to investigate the ecological relationship between the river outflow and the distribution, abundance and population structure of ammonia-oxidizing bacteria (AOB). Five surficial marine sediments were collected and analysed with polyphasic approaches. Heterogeneity and genetic diversity of beta-AOB populations were examined using restriction fragment length polymorphism (RFLP) analysis of 16S rRNA and amoA genes. A shift of the microbial community was detected in samples along the transect. Both 16S rRNA and amoA genes generated polymorphisms in the restriction profiles that were distinguishable at each sampling site. Two 16S rRNA gene libraries were constructed using the reverse transcription polymerase chain reaction (RT-PCR) method to determine the major ammonia oxidizers maintaining high cellular rRNA content. Two major groups were observed in the Nitrosomonas lineage; no Nitrosospira were detected. The effort to isolate novel AOB was successful; the isolate dominated in the gene libraries. For quantitative analysis, a real-time PCR assay targeting the 16S rRNA gene was developed. The population sizes of beta-AOB ranged from 1.6 x 10(7) to 3.0 x 10(8) cells g(-1) in dry sediments, which corresponded to 0.1-1.1% of the total bacterial population. An immunofluorescence staining using anti-hydroxylamine oxidoreductase (HAO) antibody was also tested to obtain complementary data. The population sizes of ammonia oxidizers ranged between 2.4 x 10(8) and 1.2 x 10(9) cells g(-1) of dry sediments, which corresponded to 1.2-4.3% of the total bacterial fraction. Ammonia-oxidizing bacteria cell numbers deduced by the two methods were correlated (R = 0.79, P < 0.01). In both methods, the number of AOB increased with the distance from the river mouth; ammonia-oxidizing bacteria were most numerous at B30, where the ammonium concentration in the porewater was markedly lower and the nitrite concentration was slightly higher than nearby sites. These results reveal spatial distribution and shifts in the population structure of AOB corresponding to nutrients and organic inputs from the river run-off and phytoplankton bloom.

Crude oil bioremediation field experiment in the Sea of Japan.

Experimental bioremediation of crude oil was conducted for approximately 3 months in the intertidal zone of the Sea of Japan, Hyogo Prefecture. Artificial mixtures of weathered Arabian light crude oil and sand taken from the experimental site were wrapped in polyester net envelopes. The envelopes were placed in drum-shaped acrylic vessels with perforated sides to facilitate seawater exchange. The vessels were laid in the intertidal area. Slow release nitrogen and phosphorus synthetic fertilizer granules were added to the oil-sand mixtures in three different amounts. Some oil-sand mixtures were unfertilized controls. The oil-sand mixtures were periodically sampled and changes in the composition of the residual oils were monitored. Oil samples were subjected to gas chromatography coupled with mass spectrometry for analysis of some representative semi-volatile aliphatic and aromatic compounds. All values for each analyte were normalized against that of hopane to evaluate the extent of oil biodegradation. Significant increases in the concentrations of both nitrogen and phosphorus were found in the fertilized sections in accordance with the amounts of added fertilizers. Although significant natural attenuation of oil was observed in the unfertilized sections, fertilization stimulated the degradation rate of the oil in the early stage of the experimental term. The extent of the oil biodegradation increased as the amount of added fertilizer increased. However, the final degradation efficiencies for each oil component in the fertilized sections were not significantly different from those in the unfertilized sections, and the degradation of each oil component had almost ceased after 6 weeks. We conclude that excessive amounts of macronutrients are required to accelerate oil biodegradation and that fertilization is only effective in the early stages.

Natural water-purification system observed in a shallow coastal lagoon: Matsukawa-ura, Japan.

Field surveys and in situ experiments were conducted in the shallow Matsukawa-ura in summer to evaluate the biological efficiencies of shallow-water areas for preserving coastal ecosystems. In Matsukawa-ura (5.8 km(2)), the suspension-feeding bivalves Ruditapes philippinarum and Crassostrea gigas were the dominant animals--their total biomasses (wet weight) were estimated to be 3.4 x 10(6) and 2.3 x 10(6) kg, respectively. Ulva sp. and Zostera marina were the dominant macrophyte species during the summer, with standing crops estimated to be 0.29 x 10(6) and 0.20 x 10(6) kg, respectively. The dissolved inorganic nitrogen (DIN) uptake rates for Ulva sp. and Z. marina were determined by in situ experiments. An ecological model calculated on the basis of the observed dataset showed that, in comparison with tidal exchange, a significant amount of particulate organic matter was removed by bivalve filtration and a considerable quantity of DIN was removed by macrophyte species.