Currently, wetland stability is under threat due to the joint effects of global climate change and human activity, especially in lakes. Hence, it is necessary to evaluate the health status of wetland ecosystems such as lakes, identify the variables causing the wetland degradation and work to protect the wetlands from the identified variables in the future. Based on fourteen high-resolution autumn remote sensing images from 1989–2013, the classification characteristics and spatial distribution patterns of wetland landscapes in Poyang Lake were studied through quantitative interpretation technology. An established health assessment index system named the EHCI (Ecological Health Comprehensive Index) was used to assess the health status of Poyang Lake. Additionally, the relationship between water regime and health status of wetland landscape distribution of Poyang Lake were investigated by multivariate statistical analysis. The results demonstrated: (1) The total area of three first level (or six second level) types of wetland landscapes showed a stable status, which was long-term maintaining at about 3026 km² from 1989–2013. (2) The water area shows a downward trend, while the areas of vegetation and land-water transition zone show upward trends. (3) The proposed EHCI of the Poyang Lake wetland presented a downward trend. According to the EHCI results from 1989–2013, the health status of Poyang Lake wetland was healthy for two years, unhealthy for four years and sub-healthy for eight years. (4) The water level fluctuation greatly affected the EHCI, and the effect became greater as the water level increased. These results contribute to the understanding of specific effects of hydrological process on the health status of the Poyang Lake wetland. In addition they provide a scientific reference for the maintenance of stable ecosystem functions of the seasonal freshwater lake. These results contribute to the understanding of specific effects of hydrological process on the health status of the Poyang Lake. In addition they provide a scientific reference for the maintenance of stable ecosystem functions of the seasonal freshwater lake.

Water regime was one of the most important driving factors in the formation of wetland landscape and the growth and distribution pattern of wetland vegetation. Currently, research on the relationship between wetland landscape and water regime was mostly focused in autumns and winters in Poyang Lake, and lack of research in springs. Based on the nine high-resolution spring remote sensing images during 2000–2010, the classification characteristics of wetland landscape and spatial distribution pattern of vegetation and their succession trends in Poyang Lake were studied through quantitative interpretation technology and multivariate statistical analysis. Combined with water level fluctuations characteristics of the five monitoring hydrological stations (i.e., Hukou, Xingzi, Duzhan, Tangyin and Kangshan) at the Poyang Lake, the inter-annual and intra-annual water level variations of Poyang Lake were analyzed. The study was aimed to investigate the quantitative effects of water regime on the spring wetland landscape and spatial distribution pattern of vegetation and their succession trends in Poyang Lake. The results showed that: (1) the maximum scope of water levels of the five monitoring stations varied from 8.5 m to 13.57 m, and the water level of Poyang lake showed a downward trend, declining at an average rate of 0.16 m per year during 2000–2010; (2) the total area of the 10 types of the landscapes did not change significantly, which was always maintained at about 3026 km $2^{}$ and the total area of vegetation coverage showed increasing trend during 2000–2010 in Poyang Lake, with a maximum area in 2008 and a minimum area in 2010; (3) The water level change was consistent with the area of the lake water, and was inconsistent with the areas of the mudflat, vegetation and land-water transition zone. The highest linear fitting degree with water level was the area of the land-water transition zone, followed by the lake water and vegetation. The results were helpful to further explore the eco-hydrology process and its trend at Poyang Lake wetland, a scientific reference for the maintenance of stable ecosystem functions of the seasonal freshwater lake wetland.

Transparent exopolymer particles (TEP) are essential for the carbon cycle in aquatic environments. However, the distribution of TEP, its precursor, and the contribution to the organic carbon pool in the large freshwater lake remain inadequately understood. Here, we focused on the spatial distribution of TEP and dissolved acidic polysaccharides (dAPS) in four typical seasons in Lake Taihu, the third-largest lake in China. TEP concentrations in Lake Taihu ranged from 0.05 to 5.19 mg Xeq/L, with a mean value of 1.31 ± 1.08 mg Xeq/L. The concentration of dAPS in the lake averaged 3.7 ± 2.19 mg Xeq/L (range, 0.19–13.12 mg Xeq/L). Higher content of TEP and dAPS was found in summer, and their distributions appeared to be influenced by the cyanobacterial blooms, as they showed significant correlations with chlorophyll-a content in Lake Taihu in summer. In addition, TEP accounted for an average of 24.3% of particulate organic carbon, and dAPS represented 25.9% of dissolved organic carbon. These results provide valuable insights into the contribution of TEP to organic carbon pools in inland waters and highlight the role of TEP in the carbon cycling of large freshwater lakes.

Dissolved organic matter (DOM) is a kind of dissolved materials containing humic-like, protein-like and carbohydrates, which distributed widely in various kinds of water body. Due to the complex components, it is hard to analyze fully specific organic fraction. Due to three dimensional excitation-emission fluorescence (3DEEM) technique with the merits of high sensitivity, high selectivity, simple operation, and non-destructive and less sample, it has become one reliable method to study DOM. This study gave a brief introduction for 3DEEM technique, and reviewed from the characterization of DOM and the relationship between DOM and heavy meta ls. Additionally, we also summarized the application of 3DEEM in DOM from natural water environment and wastewater treatment to provide the theoretical basis and technical support for geochemical cycling of pollutants and water environmental protection and control.