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Blue carbon can be transferred from primary producers to primary consumers through oyster filter feeding. Understanding the carbon (food) sources is crucial for understanding coastal food webs and management of oyster aquaculture ecosystems. In the present study, Bayesian stable isotope mixing models (MixSIAR) were used to identify and quantify food composition within a cultured oyster ecosystem at six sites along a salinity gradient in the estuarine bay of Zhenhai (ZHB). The carbon stable isotope (δ13C) signatures of oyster Crassostrea hongkongensis ranged from −22.06 to −27.27‰, with significant spatial differences (p < 0.001), indicating variations in food resources along the salinity gradient. The primary food source for cultured oysters was suspended particle organic matter across ZHB (55.7–90.6%), with sedimentary organic matter contributing more in the mid-estuary (28.9–44.3%). Partial least squares regression (PLSR) was used to explore the effects of habitat environment and human disturbance on spatial variation in oyster diets. The results indicated that dissolved oxygen, sediment particle size, elevation, and mangrove-related landscape indices were the main factors influencing oyster diet in ZHB. The findings provide insights into the dietary composition of cultured oysters and the underlying factors in a typical shallow bay in southern China, with particular emphasis on the role of terrestrial landscape features. In addition, the findings validate PLSR as a reasonable tool for predicting the food composition of consumers in estuarine bays. • Providing the carbon isotope data in a typical oyster culture region of South China. • The MixSIAR model was employed to quantify the spatial distribution of oyster diets. • Food resources of cultured oysters changed spatially along the salinity gradient. • Coastal land use patterns in aquaculture areas could influence oyster diets. • Managing oyster aquaculture production using partial least squares regression. [ABSTRACT FROM AUTHOR]

Plant growth-promoting rhizobacteria (PGPR) inoculation is a crucial strategy for maintaining the sustainability of agriculture and presents a promising solution for seagrass ecological restoration in the face of disturbances. However, the possible roles and functions of PGPRs in the seagrass rhizosphere remain unclear. Here, we isolated rhizosphere bacterial strains from both reef and coastal regions and screened two PGPR isolates regarding their in vivo functional traits. Subsequently, we conducted microcosm experiments to elucidate how PGPR inoculation affected seagrass photosynthesis and shape within each rhizosphere microbiome. Both screened PGPR strains, Raoultella terrigena NXT28 and Bacillus aryabhattai XT37, excelled at expressing a specific subset of plant-beneficial functions and increased the photosynthetic rates of the seagrass host. PGPR inoculation not only decreased the abundance of sulfur-cycling bacteria, it also improved the abundance of putative iron-cycling bacteria in the seagrass rhizosphere. Strain XT37 successfully colonized the seagrass rhizosphere and displayed a leading role in microbial network structure. As a nitrogen-fixing bacteria, NXT28 showed potential to change the microbial nitrogen cycle with denitrification in the rhizosphere and alter dissimilatory and assimilatory nitrate reduction in bulk sediment. These findings have implications for the development of eco-friendly strategies aimed at exploiting microbial communities to confer sulfide tolerance in coastal seagrass ecosystem. • Two PGPR strains were screened from different seagrass species in both reef and coastal regions. • PGPR strains increased the photosynthetic rates of seagrass host. • PGPR inoculation inhibited and enriched the abundance of iron- and sulfur-cycling bacterial taxa, respectively. • The colonization of the seagrass rhizosphere by Bacillus aryabhattai XT37 played a leading role in the microbial network. [ABSTRACT FROM AUTHOR]

• The interaction mechanism between the station and the network is studied. • A collaborative optimization method for DDES station-network is proposed. • GA method is combined with DA to optimizes the calculation order of user nodes. • Sensitivity analysis is conducted on the number of energy stations and fluid flow velocity inside the pipeline. District distributed energy systems (DDESs) are widely used worldwide due to their environmentally-friendly and energy-saving characteristics. The strong correlation and coupling of energy stations and pipeline networks lead to difficulties in the collaborative optimization design of the DDES. To minimize the total annual cost of the system, this research proposed a collaborative optimization model to realize the integrated design of the DDES. The energy distance method is combined with the K-means cluster method to solve the problem of locating and sizing energy stations. The pipelines planning algorithm based on "Dijkstra algorithm (DA) + genetic algorithm (GA)" is used to optimize the pipeline layout and diameter simultaneously. The improved DA method continuously updates the cost full adjacency matrix and pipe diameter matrix of each pipe segment by optimizing the access sequence of user nodes, and finally obtains the optimal layout and pipe diameter of the pipe network at the same time. Moreover, this paper reveals the influence factors that should be considered in the planning of DDES, such as the number of energy station and flow velocity. The results indicate that compared to traditional optimization processes, the collaborative method proposed in this paper reduced the total annual cost of the pipeline network by 20.5 %. The improved DA method solves the problem of pipeline sharing while preventing the system from falling into local optima. Moreover, optimizing the number of energy stations and flow velocity can reduce annual cost of pipelines by 0–14 % and 0–20 %, respectively. This study provides theoretical guidance and technical support for researchers in the planning and designing of DDES. [ABSTRACT FROM AUTHOR]

Scleractinian corals are the main framework-building groups in tropical coral reefs. In the coral holobiont, nitrogen-cycling mediated by microbes is fundamental for sustaining the coral reef ecosystems. However, little direct evidence characterizing the activities of microbial nitrogen removal via complete denitrification and anaerobic ammonium oxidation (anammox) in stony corals has been presented. In this study, multiple incubation experiments using 15N-tracer were conducted to identify and characterize N 2 production by denitrification and anammox in the stony coral Pocillopora damicornis. The rates of denitrification and anammox were recorded up to 0.765 ± 0.162 and 0.078 ± 0.009 nmol N 2 cm−2 h−1 respectively. Denitrification contributed the majority (∼90%) of N 2 production by microbial nitrogen removal in stony corals. The microbial nitrogen removal activities showed diel rhythms, which might correspond to photosynthetic oxygen production. The N 2 production rates of anammox and denitrification increased with incubation time. To the authors' knowledge, this study is the first to confirm and characterize the activities of complete denitrification and anammox in stony corals via stable isotope techniques. This study extends the understanding on nitrogen-cycling in coral reefs and how it participates in corals' resilience to environmental stressors. [Display omitted] • Anammox activity in stony corals is proved by isotope tracer for the first time. • Denitrification contributed ∼90% of N 2 production in stony corals. • Variations in anammox and denitrification in corals are significantly consistent. • Microbial nitrogen removal activity in stony corals shows diel rhythms. • Microbial nitrogen removal is influenced by coral photosynthetic oxygen production. [ABSTRACT FROM AUTHOR]