Coastal wetlands are a type of unique ecosystem, in which rhizosphere microorganisms of vegetation play a significant role in the overall ecology. Rhizosphere soil samples from the vegetation of Liaohekou Coastal Wetlands, Northeast China (40°54′44″ N, 121°47′51″ E), were collected in seven habitats (Suaeda and Phragmites community in different coverage, aquaculture ponds and farmland biotopes) to evaluate the diversity and structure of bacterial community using high throughput sequencing. Soil physicochemical characteristics and bacterial communities were found to be affected by vegetation coverage by ANOVA tests. As and Ni were the main heavy metal variables affecting the bacterial communities as demonstrated by RDA tests, while NO₃⁻-N were important variables in nutrient factors. Proteobacteria was the predominant phylum in all soils. Gillisia and Woeseia were the two most dominant genera peculiarly in Suaeda and Phragmites community. Meanwhile SparCC showed that Woeseia play a dominant role in wetland rhizosphere bacterial communities. The Chemoheterotrophic function was dominant in all communities with FAPROTAX results, while in wetland the cycle of Sulfur and Nitrogen were significantly affected by vegetation type and coverage. In conclusion, this study revealed the structural composition and diversity of rhizosphere bacterial communities under different vegetation types and coverage. This research could help deepen our understanding of the microbial ecology on the wetlands and provide information on bacterial communities in various habitats.

Semi-enclosed bays are significantly influenced by the interactions between land and sea, as well as human activities. One notable human activity, land reclamation, impacts water exchange within these bays. However, the variability of sediment transport and cross-bay transport following reclamation remains poorly understood. This study aims to enhance the understanding of sediment dynamics and the responses of cross-bay transport to reclamation. A well-validated three-dimensional numerical model was developed in the Laizhou Bay (LB). Following reclamation, tidal currents suspended sediment concentration, and erosion increased seaward, while these factors decreased landward. In LB, surface and bottom subtidal currents flowed in opposite directions, with the direction of volume transport primarily determined by bottom currents. In the western LB, volume and sediment transport exhibited an anticyclonic pattern, with pronounced seasonal variations observed elsewhere. During summer, volume and sediment transport predominantly occurred from the northeast to the southwest. In winter, volume transport in northern LB was directed westward, while it was eastward in the southern part; sediment transport was primarily eastward. Advection played a significant role in sediment transport dynamics. The pathway of cross-bay sediment transport was primarily located in the central part of the bay. Notably, the cross-bay sediment transport flux in winter was approximately 3.5 times greater than in summer, with reclamation resulting in a reduction in cross-bay transport flux by about 22.17%.

The field of seawater desalination faces some challenges. For example, at present, site selection and layout of water intakes and outlets are often not carefully considered. This can easily result in the degradation of water quality due to coastal sea pollution and sudden brine discharge, which can be hazardous and can negatively impact marine development and activities such as aquaculture. By using the MIKE21 numerical simulation software, this paper establishes a two-dimensional mathematical tidal current model of the engineered sea area and a mathematical convection diffusion model after brine discharge. The tidal current field of the Laoshan Bay waters and the salinity field distribution after brine discharge in different water intake-outlet arrangement schemes in desalination plants are calculated and analyzed. In view of the various control factors affecting the layout and location selection of water intakes and outlets, combined with the current situation of marine development and utilization, calculation results and layout advantages and disadvantages of the primary schemes are compared and analyzed, the scheme with the best water intake-outlet layout is recommended, and relevant optimization suggestions are presented.

Globally, coastal regions are vital areas of human activity and, as such, are centers of population growth and urban and economic development. Long-term human development has had a major impact on the ecological environment of coastal zones. Therefore, exploring the distribution and provenance of marine sediment types in coastal areas heavily influenced by human activities can provide scientific evidence and references for the current and future ecological management of these sensitive environments. For this reason, we conducted an analysis of the sediment grain size, endmembers, and organic matter content and geochemical elements in the Lu’erhuan River-Malan Island-Sandun Island area in the eastern part of Qinzhou Bay, a region heavily influenced by human activities. The sediment grain size clearly differs throughout the study site and the material provenances and hydrodynamic conditions also vary, likely due to the local environmental conditions and the significant impact that human activities have had on the area. The finest-grained sediment is imported from either inland or coastal areas via rivers and weak tidal currents, the next finest component comes from coastal areas through weak tidal currents, and the moderately coarse component mainly originates from nearby beaches. The two coarsest-grained sediment components are influenced by the combination of human activities, tidal currents and waves and enter the water via erosion. The organic matter provenance resembles that of the sediment components, exhibiting varied characteristics. Due to the combination of natural and human activities in the bay, the organic matter in the upper reaches of the Lu’erhuan River originates from the river and coastal paddy fields, with obvious terrigenous characteristics; the organic matter in northern Malan Island mainly comes from external sources related to oyster farming, while the organic matter in eastern Sandun Island is mainly produced endogenously by marine plankton. Al, Ti, Fe, Mg, K, Ga and other elements indicate that terrestrial sediments are significantly disturbed by human activities. However, Mn reflects the marine distribution of terrestrial sediments from the Lu’erhuan River to Jishuimen. Ca and Sr, which are indicators of marine sediments, are distributed in the eastern offshore area of Sandun Island, which is connected to open waters. Due to the influence of human activities, As and Cd are highly enriched in the study area, while Cu is less affected by human activities.

Coastal zones, which serve as transitional areas between land and sea, possess unique ecological values. Sandy coasts, celebrated for their distinctive natural beauty and ideal recreational settings, have garnered significant attention. However, uncontrolled human activities can exacerbate erosion or even trigger more severe erosion along these coasts. This study utilizes unmanned aerial photography and typical beach profile survey data collected from the main areas of Wanmi Beach over the past eight years to quantify annual changes in beach erosion and elucidate the erosion characteristics and their variations across different shore profiles. Additionally, the impact of various types of human activities in different regions is analyzed, revealing the erosion patterns prevalent in the main areas of Wanmi Beach. The findings indicate that the eastern research area (ERA) has been in a continuous state of erosion, primarily due to a reduction in sediment supply in the region, with severe erosion observed on the foreshore of Fengxiang Beach and Wanmi Bathing Beach (WBB). In contrast, the central research area (CRA), particularly around Yangjiao Bay, has experienced significant siltation in recent years, with the highest siltation volume recorded between 2021 and 2023, totaling 90,352.91 m³. Nevertheless, the foreshore areas at both ends of the research area, distant from Yangjiao Bay, have been subject to erosion. The western research area (WRA) is notably impacted by surrounding aquaculture activities, leading to alternating periods of erosion and siltation on the beach surface. Consequently, due to the influence of human activities on different shore profiles, most of Wanmi Beach, except for the area near Yangjiao Bay, is experiencing erosion.