Multi-scale variability of water discharge and sediment load into the Bohai Sea from 1950 to 2011

Abstract

This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales: 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.

Incorporation of Microbial Functional Traits in Biogeochemistry Models Provides Better Estimations of Benthic Denitrification and Anammox Rates in Coastal Oceans

“…The BS and NYS basins are profoundly influenced by freshwater, sediment, and nutrient inputs, especially from the Yellow River, the sixth longest river in the world. The Yellow River discharges approximately 4.2 × 10 10 m 3 of freshwater and 1.34 × 10 10 t of sediments into these basins annually, of which the fluxes in the flood season (July–September) account for 70–80% (Ren et al, ). Additionally, the two basins receive a large amount of domestic, industrial, agricultural, and aquacultural wastewater discharges from the Bohai Economic Rim.…”

Temporal variations of the two oxygen depleted zones in the Bohai Sea

“…As a key physical factor, a strong wind can destroy the stratification, promote the ventilation of the water column, and thus alleviate the oxygen depletion of bottom water (Goodrich et al, 1987;Ni et al, 2016;Li et al, 2021a). Under the influence of the East Asian Monsoon, northwest winds are prevailing in winter in the BS with strong wind speed, while southeast winds are prevalent in summer with relatively small wind speeds, and strong wind events often occur (Ren et al, 2017). In late summer and early autumn, the increase in sea surface wind speed will destroy the stratification (Figure 9), and the ventilation of the water column will be enhanced to promote oxygen replenishment to the bottom water.…”

Extraction and spatiotemporal evolution analysis of tidal flats in the Bohai Rim during 1984–2019 based on remote sensing

“…Tidal flats play key roles not only in providing land resources for urban development but also in protecting biodiversity, degrading environmental pollutants, and buffering storm surges (Polte et al, 2005;Temmerman et al, 2013;Chen et al, 2016;Ghosh et al, 2016;Sagar et al, 2017;Zhang et al, 2019). However, a significant downward trend in the tidal flat area at both regional and global scales was reported (Wang et al, 2018;Murray et al, 2019), combined with continuous natural and human factors in the fragile intertidal zone, such as sea-level rise (Luo et al, 2011;Passeri et al, 2015), land subsidence (Xue et al, 2005;Zhang et al, 2015), reclamation (Robert et al, 2007;Ding et al, 2019) and reduction in the river sediment supply (Blum and Roberts, 2009;Ren et al, 2015). It is thus necessary to monitor the distribution and explore the spatiotemporal evolution characteristics of coastal tidal flats for scientific protection and development purposes.…”