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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]

Discarded plastic bag is a main component of marine debris, posing potential threats to marine biota. This study was conducted to assess the potential effects of microplastics on juvenile Lates calcarifer. Fish were exposed via diet to two microplastic types from conventional polyethylene (PE) and biodegradable (Bio) plastic bags for 21 days. Antioxidative enzymes activity, intestinal microbiome and proteome were determined. PE and Bio microplastics were found to accumulate in gastrointestinal tracts, and no mortality was observed. Microplastics exposure did not induce significant antioxidant response except for the glutathione reductase (GR) modulation. Intestinal microbiome diversity decreased significantly in PE group based on Simpson index. Both types of microplastics induced proteome modulation by down-regulating proteins associated with immune homeostasis. Bio microplastics maintained higher intestinal microbial diversity and induced more proteins alteration than PE microplastics. This study provides toxicological insights into the impacts of conventional and biodegradable microplastics on juvenile L. calcarifer. [Display omitted] • Both polyethylene and biodegradable microplastics could be consumed by juvenile Lates calcarifer. • Short-term microplastics exposure did not cause significant antioxidant response except for glutathione reductase modulation. • Polyethylene microplastics caused intestinal microbiome diversity reduction. • Both types of microplastics caused liver proteome alteration. • Few significant differences were observed between different microplastics. [ABSTRACT FROM AUTHOR]

• High connection between pelagic and benthic origin both in Wanshan Island and Wailingding Island with shallow waters. • Both fishes and macroinvertebrates are largely fueled by pelagic production in Wanshan Island. • Key environmental factors influencing the isotopic niches of fishes and macroinvertebrates were identified. Artificial reefs are frequently deployed in marine ecosystems to increase fishery yields and enhance the production of reef-associated fauna. However, information regarding trophic structures and pathways of faunal assemblages in artificial reef ecosystems in Pearl River Estuary were still in scare. To this end, we compared the abundances and isotopes of functional groups of fishes and macroinvertebrates in three offshore islands, including Wanshan Island with shallow artificial reefs, Miaowan Island with deep artificial reefs, and Wailingding Island with no reef. The results showed that high connection between pelagic and benthic origin in Wanshan and Wailingding Islands, with pelagic production dominating in Wanshan Island and benthic production dominating in Wailingding Island, respectively. The δ13C value of fishes was significantly lower in Wanshan Island compared to Miaowan Island and Wailingding Island, whilst the δ 15N value of macroinvertebrates was highest in Miaowan Island. Based on the trophic niches, Wanshan Island displayed higher trophic diversity and lower trophic redundancy in fish assemblages, while Miaowan Island was the same in macroinvertebrate assemblages. In addition, four key environmental indicators (i.e., salinity, pH, phosphate, and chemical oxygen demand) and five key environmental indicators (i.e., depth, dissolved oxygen, chlorophyll a , total phosphate, and transparency) were the best at explaining the niche variation of fishes and macroinvertebrates, respectively. Our findings provide an understanding of ecosystem functioning within and around the artificial reef systems to further enhance effective management. [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]

Deployment of artificial reefs (ARs) has become popular technique to create new hard-bottom habitats, increase biodiversity and richness for fisheries. We compared the faunal community structure and food web structure associated with before and after fishing moratorium between ARs and non-ARs in Wanshan Island, Pearl River Estuary using stable isotope techniques. Community composition showed higher differences between ARs and non-ARs. The range of δ13C and δ15N of different functional groups can distinguish the pelagic and benthic trophic pathways of the food web in reef-or-not area before and after fishing moratorium. The isotopic niches of entire faunal, as well as individual functional groups, overlapped less between ARs and non-ARs in Wanshan Island, which makes the isotopic functional indices non-equivalent. The total convex hull area (TA) of ARs was larger than that of non-ARs, indicating that nutrient pathways of ARs were more diverse. Overall, however, these results suggest that trophic structure was convergence between ARs and non-ARs, and differences before and after fishing moratorium, possibly due to seasonal differences. Finally, it was shown that the construction of ARs had a weak effect on the restoration of fishery resources in this area, which might be related to lack of further management, or even similar community composition to non-ARs areas. • The differences in community composition between artificial reef and non-artificial reef. • The value of niche overlap for artificial reef or not (16.14%) was greater than that before and after fishing moratorium (11.73%), indicating that the differentiation of niches was more obvious before and after fishing moratorium. • The analysis of the nutritional contribution of baseline consumers to high trophic consumers revealed that artificial reefs had no significant effect on the acquisition of high trophic prey. However, the implementation of the fishing moratorium resulted in a slight change in the feeding strategy. [ABSTRACT FROM AUTHOR]

• Lates calcarifer effectively eliminated polyethylene fibers after ingestion. • Fibers exposure induced oxidative stress. • Fibers ingestion caused intestinal microbiome dysbiosis. • Lactobacillus reuteri and L. intestinalis were sensitive to fibers exposure. • Slight intestinal histological damage was found. Microplastic fibers originating from fishing ropes and nets are persistent and ubiquitous marine environmental pollutants that pose potentially threat to the health of aquatic species. Therefore, assessing their potential effects on marine biota has become an urgent research topic. In this study, the fate of fibers ingested by L. calcarifer and its consequence on intestine health were analyzed. A total of 150 fish was fed with polyethylene (PE) fibers at 1% concentration for 56 days. Retention of fibers, oxidative stress indicator malondialdehyde (MDA), intestinal permeability indicator diamine oxidase (DAO), intestine microbiome modulation and histological damage were evaluated. The results indicated that the consumption of fibers-contained food did not influence the growth of the fish. Low retention of fibers was observed, indicating effective elimination of fibers from the body of the fish and no significant accumulation after successive exposure. However, intestine oxidative stress was observed, indicated by an up regulation of MDA level. Whereases, DAO level was not influenced by the treatment. Fiber exposure induced intestine microbiome dysbiosis by decreasing alpha diversity especially community richness and inhibiting the growth of Lactobacillus and short-chain fatty acid producing bacteria. Lactobacillus reuteri and L. intestinalis were inhibited significantly, we suggested they can be sensitive indicators for fibers toxicity evaluation in future studies. Slight intestinal damage was observed after the feeding period. We concluded that dietary exposure to PE fibers did not induce acute harm to L. calcarifer. However, chronic effects were observed after the feeding period, including oxidative stress, intestine microbiome alterations, and intestinal damage. These findings provide valuable data for ecological risks assessment of fishing rope fiber in the marine environment. [ABSTRACT FROM AUTHOR]