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Using a laboratory simulation experiment, we studied the trend of change in methylmercury (MeHg) content of sediments in response to the changing salinity of flooding water (deionized water, 0.5%, 1.0%, 1.5%, and 2.0%) and sulfate-reducing bacteria (SRB) content for both the surface layer (0–10 cm) and the bottom layer (10–20 cm) of Suaeda heteroptera wetland sediments in the Liaohe estuary under anaerobic and aerobic conditions, respectively. The results showed that under AAC (anaerobic conditions), the MeHg content in the surface and bottom sediment layers increased first and then decreased over time and was highest at the 14th day. In contrast, under AC (aerobic conditions), the MeHg content in sediments of both layers increased slowly with increasing test time. The MeHg content in sediments increased first and then decreased with rising salinity and was highest at a salinity of 1.0%. Among the samples collected at different experimental stages, the SRB content in the sediments showed a decreasing trend with rising flooding salinity under AAC and AC. The MeHg and SRB contents were higher under anaerobic conditions than under aerobic conditions. Linear fitting results showed that there was no linear correlation between MeHg contents and SRB quantities in surface and bottom sediments under AAC and AC (R 2 < 0.1). Collectively, these results suggest an important role for flooding salinity and anaerobic-aerobic conditions in the production of MeHg in S. heteroptera wetlands of the Liaohe estuary, and may predict the ecological risk of methylmercury according to the change of salinity. • MeHg in sediments response to the change of salinity (CK, 0.5%, 1.0%, 1.5%, and 2.0%) of water was studied. • The highest MeHg occurred at 1.0% salinity of water and MeHg in all sediment increased substantially. • MeHg in sediment increased in less extent in the aerobic conditions compared to the anaerobic conditions. • Other bacteria apart from SRB might be responsible for the MeHg change in such estuary environment. [ABSTRACT FROM AUTHOR]

• Spatial heterogeneity of LUCC and ecosystem service (ES) changes driven by policies. • Spatial characteristics of synergies and trade-offs between ES. • The drivers of synergies and trade-offs between ES. • Contrasting effects of multi-policies on ES in northeastern China. Understanding the spatial patterns and temporal dynamics in ecosystem services can provide scientific guidance to promote the sustainable management of ecosystems. Comprehensive and detailed information of ecosystem services response to multiple development and conservation policies is needed for Liaoning. Therefore, this study examined land cover changes and documented ecosystem service dynamics associated with diverse policies in this region. The results revealed that agricultural development was considered to be the most significant factor leading to the degradation of natural vegetation. Moreover, large-area croplands recovered to natural vegetation under the guidance of ecological restoration policies, resulting in a net woodland area increase by 220.45 km2. Built-up land expanded markedly at the expense of cropland, while newly formed cropland was primarily converted from wetland and woodland. Furthermore, ecosystem carbon stock, soil retention and water yield were enhanced at the Liaoning scale, while habitat suitability experienced a slight decline. Ecological rehabilitation programs enhanced synergies between ecosystem services, while urban development strategy may be responsible for the trade-offs between supply services and regulation services. In terms of current policy and ecosystem service dynamics, it is worth considering how to weaken policy-driven natural ecosystem losses and promote the efficacy of ecological rehabilitation programs. The findings in this study are expected to benefit both ecological protection and socio-economic prosperity in Liaoning. [ABSTRACT FROM AUTHOR]