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Characterization of phosphorus (P) pools is vital to understanding the contribution of P to water eutrophication. In this study, dissolved and particulate P classes during an algae bloom in Lake Taihu, as well as their relationships with the main environmental factors, were analyzed based on solution 31 P NMR. The results showed that dissolved P was dominated by orthophosphate (Ortho-P) in heavily polluted regions and by orthophosphate monoester (Mono-P) and orthophosphate diester (Diester-P) in lightly polluted regions, indicating that the main dissolved P classes varied with the degree of lake pollution. The difference in the temporal variation patterns of dissolved P classes revealed that dissolved Ortho-P is the preferred class, and its concentration may be affected by major primary producers. It also revealed that dissolved Mono-P is prone to accumulation under the effects of algal blooms, especially in heavily polluted regions. The main particulate P classes were similar to those of dissolved P, but their variation trends were the same in different lake regions. There were significant positive correlations between the major particulate P classes and Chl a during the majority of the sampling period, indicating that living algal cells have a major contribution to particulate P. Obvious temporal variations of P classes may affect the bioavailability and dynamics of P in the water of Lake Taihu, but the particle reactivities of the main inorganic and organic P classes were similar. Therefore, they have little effect on P partitioning between the dissolved and particulate phases. [ABSTRACT FROM AUTHOR]

Algal blooms (ABs) can affect the migration of phosphorus (P) among sediments, interstitial water and overlying water. It is important to analyze the characteristics of P and their interactions in the three media during ABs. A 5-month field study (June to October in 2016) was conducted in Zhushan Bay of Lake Taihu. P fractions, P adsorption characteristics and P diffusion fluxes at the sediment-water interface (SWI) were investigated. During the outbreak period of ABs from June to August, labile P concentrations in the sediment measured by diffusive gradients in thin films (DGT-labile P) and its diffusion fluxes across the SWI increased significantly. The equilibrium P concentration (EPC 0) of the sediment was higher than the PO 4 3--P concentration in the overlying water. During the period of decline of ABs from September to October, the concentrations and diffusion fluxes of DGT-labile P sharply decreased. However, the sediment total P (TP), overlying water TP, total dissolved P (TDP) and PO 4 3--P concentrations increased. These results show that the ability of sediment solids to supplement interstitial water labile P was significantly enhanced by the outbreak of ABs. Labile P was then intensively released into the overlying water by interstitial water. Degraded algae became a crucial P source during the period of decline of ABs. P from the degraded algae was re-released to the sediment and overlying water. The observed DGT-labile P and DGT-labile Fe coupling in June, September and October confirmed the Fe redox-driven P release mechanism in sediment during these periods. The decoupling of DGT-labile P and DGT-labile Fe was observed in July and August and was probably caused by algal decomposition, labile organic P degradation and/or sulfate reduction in sediment stimulated by the ABs outbreak. [Display omitted] • Sediment P was strongly influenced by the outbreak and decline of algal blooms. • Labile P diffusion flux at SWI increased first and then decreased during algal blooms. • The decoupling of labile P and labile Fe occurred in July and August. • P migration in sediment, pore water, overlying water was accelerated by algal blooms. [ABSTRACT FROM AUTHOR]

Organic phosphorus (P) fractions in surface sediments from a large shallow, eutrophic Lake Taihu, China, were extracted with 0.1 M NaOH after pre-treatment of the sediments with a solution composed of 0.1 M EDTA and 2% (w/v) Na2S2O4. Composition of organic P in the extracts was then characterized by 31P nuclear magnetic resonance spectroscopy (31P NMR). Several P species, including phosphonates, orthophosphate, orthophosphate monoesters, phospholipids, DNA, pyrophosphate and polyphosphate, were detected in the NaOH extracts. The proportion of extracted organic P to total P in sediments was negatively correlated with total P in the water column, as were the proportions for orthophosphate monoesters and DNA. This implies that the majority of organic P in surface sediments is likely stabilized in some way, and does not directly contribute to the internal loading of P from sediments. [Copyright &y& Elsevier]

Human disturbance is one of the essential forces affecting changes in landscape patterns. Studying the relationship between human disturbances and landscape patterns is of significance for regional conservation and ecosystem management. An understanding of this relationship is also crucial for the mitigation of conflicts between socioeconomic development and environmental protection. In this study, using remote sensing data and geographical information system technology, we created a quantitative method to assess the intensity of human disturbance on the landscape by introducing the concept of hemeroby. By means of the measurement of hemeroby and statistical approaches, we quantitatively analyzed the temporal and spatial changes of human disturbances and their effects on landscape patterns in the Jiangsu coastal zone, China, from 1995 to 2013. The results showed that the intensity of human disturbance gradually increased from 1995 to 2013. While the increasing rate of intensity of human disturbance has slowed down from early period (1995–2002) to later period (2002–2013) because of differences in exploitation activities and regional development policies. Spatially, the hemeroby increased most obviously in the southern counties and northern Ganyu County, resulting from port construction and tidal flat reclamation. Depending on the different degrees of human disturbance, landscape patterns showed obvious differences. Compared with low-level and high-level human disturbance, mid-level human disturbance contributed to more fragmented landscape, more complex patch shape, lower connectivity, and higher diversity. A correlation analysis between landscape indices and hemeroby suggested that the landscape patterns in regions with high-level human disturbance were relatively sensitive to changes in the intensity of human activities. The findings in this paper provide additional spatial information and theoretical guidance for regional conservation and ecosystem management in the Jiangsu coastal zone, China. [ABSTRACT FROM AUTHOR]

The need for minimizing water eutrophication makes controlling phosphorus (P) release and/or loss from sediments/soil an urgent matter. This research seeks to develop methods to predict P release in sediments. We first studied the P adsorption in 10 sediments from a sub lake of Taihu Lake, China for 80 days. After adsorption, the sediments were extracted with 0.01 M CaCl 2 and 0.5 M pH 8.5 NaHCO 3 solutions. We found strong linear relationships between the equilibrium concentration and CaCl 2 -P (R 2 = 0.91) and between P adsorbed and NaHCO 3 -P (R 2 = 0.90). This result suggests that: (I) CaCl 2 -P can be used as a proxy for the P concentration between the sediment interface and overlying water when it is difficult to measure P; (II) NaHCO 3 -P is able to evaluate the newly adsorbed P in the sediments which may reflect the enriched process. The results indicate that we could link CaCl 2 -P and NaHCO 3 -P further using common isotherm models. This hypothesis was tested for our sediment data and soil data from published literature. Models derived from Langmuir and Temkin isotherms could successfully fit the data. In more general applications, our models are also capable of describing the relationship of NH 4 Cl-P and TP. They are routine indexes to assess the status of sediment P. The fact that the models predict P loss in soils or P release from sediment well makes them potentially useful in areas of wide P risk assessment. [ABSTRACT FROM AUTHOR]

• Stable isotope technique was applied to study water use strategy of wetland plant. • The main water source of Carex cinerascens was changed from lake water to soil water. • Water conditions strongly adjusted WUE and water niche of Carex cinerascens. • Carex cinerascens had obvious adjustability and adaptability. Water is a key factor in maintaining plant growth and determining plant species distribution. Studying the water use strategies of plants under different water conditions is of great significance for understanding the wetland vegetation patterns and performing ecological regulation of wetlands. The present study aims to quantify the contribution rates of potential water sources to Carex cinerascens in the Poyang Lake Wetland using stable isotope techniques and to assess water use efficiency (WUE) and water niche breadth to reveal the water use strategy of C. cinerascens and its response to water condition changes. The results showed that soil water in the 0–20 cm soil layer replaced lake water, becoming the main source of water for C. cinerascens during the growing season as a result of the decrease in the lake water levels and the change in soil water contents. The contribution rates of soil water in the 0–20 cm soil layer to the development of C. cinerascens in the 12-, 13-, and 14-m elevation zones increased by 31.4, 11.0, and 21.1 %, respectively. In addition, the contribution rate of soil water from the 20–40 cm soil layer was lower than that from the 0–20 cm soil layer, while rainwater exhibited the lowest contribution rates to the development of C. cinerascens. The aboveground parts exhibited higher WUE values than those of belowground parts at the growth stage, except in the 14-m elevation zone, and lower WUE values than those of the belowground parts at the maturation and wilting stages of C. cinerascens. According to the calculated Levins index, the water niche breadths of C. cinerascens were reduced and increased under abundant and insufficient water amounts, respectively. C. cinerascens adjusted the water source, WUE, and water niche breadth during the entire growing season to adapt to changing water conditions in the Poyang Lake Wetland, thereby reflecting the strong adjustability and adaptability of C. cinerascens. This study provides further insights into the relationships between wetland vegetation and hydrological changes, as well as a scientific basis for wetland ecological and hydrological regulation and vegetation restoration in the Poyang Lake Wetland. [ABSTRACT FROM AUTHOR]