Comparing Wetland Ecosystems Service Provision under Different Management Approaches: Two Cases Study of Tianfu Wetland and Nansha Wetland in China

Effects of salinity on nitrogen reduction pathways in estuarine wetland sediments

Denitrification, anammox, and DNRA are three important nitrogen (N) reduction pathways in estuarine sediments. Although salinity is an important variables controlling microbial growth and activities, knowledge about the effects of changing salinity on those three processes in estuarine and coastal wetland sediments are not well understood. Herein, we performed a 60-d microcosms experiment with different salinities (0, 5, 15, 25 and 35 ‰) to explore the vital role of salinity in controlling N-loss and N retention in estuarine wetland sediments. The results showed that sediment organic matter, sulfide, and nitrate (NO3-) were profoundly decreased with increasing salinity, while sediment ammonium (NH4+) and ferrous (Fe2+) varied in reverse patterns. Meanwhile, N-loss and N retention rates and associated gene abundances were differentially inhibited with increasing salinity, while the contributions of denitrification, anammox, and DNRA to total nitrate reduction were apparently unaffected. Moreover, denitrification rate was the most sensitive to salinity, and then followed by DNRA, while anammox was the weakest among these three processes. In other words, anammox bacteria showed a wide range of salinity tolerance, while both denitrification and DNRA reflected a relatively limited dynamic range of it. Our findings could provide insights into temporal interactive effects of salinity on sediment physico-chemical properties, N reduction rates and associated gene abundances. Our findings can improve understanding of the effects of saltwater incursion on the N fate and N balance in estuarine and coastal sediments.

Anthropogenic impact on ecosystem service value of urban blue space in Old Malda Municipality of eastern India

Present study attempted to quantify the anthropogenic impact on blue space (BS) and potential ecosystem service value (ESV) and link them. A small urban area of eastern India was taken as a case. To fulfill the purpose, the primary data extracted from the field was used. Firstly, an anthropogenic impact score (AIS) comprising eight components was calculated using rank compositing. ESV was estimated with the help of the Rapid Assessment of Wetland Ecosystem Services (RAWES) approach of the Ramsar convention. Rank correlation was carried out for linking AIS and ESV. Results show that 70% of BS is characterized by moderate to high levels of anthropo-driven impacts. Landscape, habitat, and pollution were detected as prime vectors behind these impacts. The impacts were higher in the core urban area. Contrarily, the potential ESV was found to be higher in the peripheral BS units. Most of the blue space failed to offer remarkable provisions and cultural services. However, the regulating services were recorded to have better status. The study clearly reported a negative association between AIS and ESV in BS. Conversion of BS, habitat alteration, pollution, and lack of restoration were found to have very prominent negative effects on ESV. Minimizing such anthropogenic impacts could improve the ESV credibility of urban blue spaces.

Construction of Ecological Security Patterns Based on Circuit Theory under the Resistance Distance Principle

Against the background of China’s advocating ecological civilisation construction, an urgent task and a major challenge are to identify key places for ecological protection and restoration and then propose optimisation strategies for future land use, especially in the Pearl River Delta (PRD), one of the regions in China that has the highest urbanisation level. In this study, we find the key places by constructing ecological security patterns and proposing optimisation strategies for future land use by analysing land-use status. We also propose a source identification method based on the resistance distance principle. Results show that forty-six sources were mainly distributed in the mountainous areas surrounding PRD but were less distributed along both sides of the Pearl River estuary. The difference in the spatial distribution of sources is remarkable. Eighty-four corridors generally had spider-like shapes. In the central plain of PRD, corridors were relatively long and narrow. Ninety pinch points were concentrated on existing rivers. Three barriers were located in the corridors between adjacent sources. Two artificial corridors were proposed to be established, which can improve the ecological network connectivity. The method for extracting sources based on the resistance distance principle is proven to be advantageous for improving the integrity of source extraction results and making ecological security patterns more reasonable.