Quantifying the Impact of Hydrological Connectivity on Salt Marsh Vegetation in the Liao River Delta Wetland.

Salt marshes play a critical role in ecological functioning and have significant economic value. Hydrological elements are considered to be one of the major contributors to salt marsh degradation. However, how hydrological connectivity affects salt marshes remains poorly investigated at fine scales. This paper used spatial analysis and statistical methods to investigate the impact of hydrological connectivity on the spatial and temporal distribution characteristics of salt marsh vegetation in two natural succession areas of the Liao River Delta wetland in 2020 and 2021 by selecting vegetation area, NDVI, tidal creeks area, distance to tidal creeks, and the Index of Connectivity, using 1 m Gaofen-2 data and 0.2 m aerial topographic data. The study found that the area and growth status of vegetation and the overall connectivity in 2021 were better than that in 2020, while the west bank of the Liao River was better than that on the east bank. Phragmites australis showed a round island distribution pattern primarily at the end of tidal creeks. The differences between different hydrological connectivity and vegetation area were significant in 2021. The vegetation area was the largest under poor and moderate connectivity. We also found that within a distance range of 0-6 m from tidal creeks, the vegetation area increased with increasing distance, but beyond 6 m, the vegetation area decreased with increasing distance. Our results showed that poor and moderate connectivity conditions were more suitable for vegetation growth. The threshold value of 6 m can provide an important reference for wetland vegetation restoration in the Liao River Delta wetland. Supplementary Information: The online version contains supplementary material available at 10.1007/s13157-023-01693-4.

Why did the world's largest green tides occur exclusively in the southern Yellow Sea?

The world's largest green tide, caused by the nuisance green algae Ulva prolifera, has occurred in the southern Yellow Sea for 16 consecutive years. It is puzzling why the extensive floating green tide occurs exclusively in the southern Yellow Sea, rather than other waters. We speculate that the transition of U. prolifera from a sessile state to a surface-floating one is the underlying cause of the floating green tide. Here we founded that the floating of U. prolifera was attributed to detachment from substrata and appropriate desiccation. The convergence of unreasonable green algae disposal, geographical features and farming patterns of Porphyra (economic red algae) in Subei Shoal contributed to mass production of floating U. prolifera, resulting in the exclusive occurrence of the floating green tides. Inducing the natural inactivation of green algae to prevent the floating of U. prolifera may effectively mitigate the extensive Ulva bloom at zero cost.

Radioactivity concentrations in soils in the Qingdao area, China.

The specific activity concentrations of radionuclides (238)U, (232)Th, and (40)K of 2300 sampling points in the Qingdao area were measured by an FD-3022 gamma-ray spectrometer. The radioactivity concentrations of (238)U, (232)Th, and (40)K ranged from 3.3 to 185.3, from 6.9 to 157.2, and from 115.8 to 7834.4 Bq kg(-1), respectively. The air-absorbed dose at 1 meter above ground, effective annual dose, external hazard index, and radium equivalent activity were also calculated to systematically evaluate the radiological hazards of the natural radioactivity in Qingdao. The air-absorbed dose, effective annual dose, external hazard index, and radium equivalent activity in the study area were 98.6 nGy h(-1), 0.12 mSv, 0.56, 197 Bq kg(-1), respectively. Compared with the worldwide value, the air-absorbed dose is slightly high, but the other factors are all lower than the recommended value. The natural external exposure will not pose significant radiological threat to the population. In conclusion, the Qingdao area is safe with regard to the radiological level and suitable for living.

[Inorganic nitrogen and phosphate and potential eutrophication assessment in Liaodong bay].

On basis of field data measured during 4 cruises from June to September in 2002, variation feature of inorganic nitrogen and phosphate in Liaodong Bay was analyzed. Regression analyses of NH4+(-)N, NO3-(-)N, NO2-(-)N and PO4(3-)-P versus pH as well as inorganic nitrogen and phosphate versus salinity were also conducted. Finally, potential eutrophication of Liaodong Bay was assessed. It is shown that inorganic nitrogen and phosphate in Liaodong Bay vary with different months and different locations. In coast areas inorganic nitrogen and phosphate are mainly affected by rivers, while in central areas of the bay, they are subject to marine biochemical process. Ratio of inorganic nitrogen to phosphate rises to 60.6 from 52.5 in early June, then drops to 39, all far above Redfield value 16. Inorganic nitrogen and phosphate versus pH as well as salinity show different correlation. For example, the correlation coefficient of NO2(-)-N and pH even reaches 0.93. During 4 cruises in Liaodong Bay the total inorganic nitrogen is 212.0 microg/L, phosphate 10.1 microg/L, N/P 50.77. Potential eutrophication assessment indicates that during the survey period Liaodong Bay can be classified as a phosphate-limiting moderate-level nutrient area.