State Key Laboratory of Marine Pollution

Diatoms and dinoflagellates are two major bloom-forming phytoplankton groups in coastal ecosystems and their dominances will notably affect the marine ecosystems. By analyzing an 18-year monthly monitoring dataset (2000-2017) in the Pearl River Estuary (one of the most highly urbanized and populated estuarine in the world), we observe an increasing trend of the diatom to dinoflagellate ratio (Diatom/Dino). As revealed by multiple statistical models (generalized additive mixed model, random forest, and gradient boosting algorithms), both groups are positively correlated with temperature. Diatoms are positively correlated with nitrate and negatively correlated with ammonium while dinoflagellates show an opposite pattern. The Diatom/Dino trend is explained by an altered nutrient composition caused by a decadal increase in anthropogenic input, at which nitrate increased rapidly while ammonium and phosphate were relatively constant. Regarding the interaction of warming and nutrient dynamics, we observe an additive effect of warming and nitrate enrichment that promotes the increase in diatom cell density, while the dinoflagellate cell density only increases with warming when nutrients are depleted. Our models predict that the Diatom/Dino ratio will further increase with increasing anthropogenic input and global warming in subtropical estuarine ecosystems with nitrate as the dominant inorganic nitrogen; its ecological consequences are worthy of further investigation.

Abstract Tuning the interfacial structure of metal oxide substrates is an essential strategy to induce electronic structure reconstruction of supported catalysts, which is of great importance in optimizing their catalytic activities. Herein, vanadium oxides‐supported Ir catalysts (Ir‐V 2 O 3 , Ir‐VO 2 , and Ir‐V 2 O 5 ) with different interfacial bonding environments (Ir‐V, Ir‐O bri , and Ir‐O, respectively) were investigated for hydrogen evolution reaction (HER). The regulating mechanism of the influence of different interfacial bonding environments on HER activity was investigated by both experimental results and computational evidence. Benefiting from the unique advantages of interfacial Ir‐V direct metal bonds in Ir‐V 2 O 3 , including enhanced electron transfer and electron donation ability, an optimized HER performance can be obtained with lowest overpotentials of 16 and 26 mV at 10 mA cm −2 , high mass activities of 11.24 and 6.66 A mg −1 , and turnover frequency values of 11.20 and 6.63 s −1 , in acidic and alkaline conditions respectively. Furthermore, the assembled Ir‐V 2 O 3 ||RuO 2 anion exchange membrane (AEM) electrolyzer requires only 1.92 V to achieve a high current density of 500 mA cm −2 and realizes long‐term stability. This study provides essential insights into the regulating mechanism of interfacial chemical bonding in electrocatalysts and offers a new pathway to design noble metal catalysts for different applications.

Mixotrophic protists are widely observed in the aquatic ecosystems, while how they respond to inorganic nutrient imbalance and ocean warming remains understudied. We conducted a series of experiments on a mixotrophic dinoflagellate Lepidodinium sp. isolated from subtropical coastal waters to investigate the combined effect of temperature and medium nitrate to phosphate ratio (N:P ratio) on the ingestion activities of mixotrophic protists. We found Lepidodinium sp. displayed selective feeding behaviour with a higher ingestion rate on high-N prey (N-rich Rhodomonas salina ) when the ambient inorganic N:P ratio was equal to or below the Redfield ratio. The Chesson selectivity index α increased with increasing temperature, suggesting that warming exacerbated the selective feeding of Lepidodinium sp. Under inorganic nitrogen sufficient conditions (N:P ratio = 64), no selective feeding was observed at 25 and 28°C, while it occurs at 31°C, which also indicates that warming alters the feeding behaviour of Lepidodinium sp. In addition, our results revealed that the total ingestion rate of Lepidodinium sp. under the condition with normal inorganic nutrients (Redfield ratio) was significantly lower than that under nutrient-imbalanced conditions, which indicates that Lepidodinium sp. developed compensatory feeding to balance their cellular stoichiometry and satisfy their growth. Our study is the first attempt on revealing the selective feeding behaviours of mixotrophic protists on prey under different inorganic nutrient environments and rising temperatures, which will contribute to our understanding of the response of marine plankton food web to projected climate changes.

Mixotrophs are widely distributed in aquatic ecosystems and play critical roles in the planktonic food web. However, how mixotrophs respond to projected ocean warming remains a debatable topic. To close the knowledge gap, we investigated the thermal responses of growth rate and functional traits of a mixotrophic dinoflagellate ( Lepidodinium sp.) isolated from subtropical coastal waters. We found that Lepidodinium sp. is a facultative mixotroph with an obligate phototrophic lifestyle that adjusts its phagocytotic feeding according to inorganic nutrient concentrations. The thermal sensitivity in terms of activation energy ( E a , eV) of Lepidodinium sp. grown in mixotrophic mode (with sufficient prey, 0.69-0.89 eV) was significantly higher than in autotrophic mode (without prey, 0.30-0.37 eV). This finding is consistent with the results of predominantly heterotrophic mixotrophs, providing experimental evidence for the hypothesis that mixotrophs shift towards more heterotrophy with rising temperatures. Warming stimulated a higher growth rate of Lepidodinium sp. grown in mixotrophic conditions than in autotrophic conditions, indicating that mixotrophic dinoflagellates may benefit substantially from mixotrophy when temperature increases and prey is sufficient. Moreover, the cell size of both autotrophic and mixotrophic Lepidodinium sp. decreased with increasing temperature. The N:P and C:P ratios of Lepidodinium sp. did not vary with temperature, while the C:N ratio slightly increased. Our results suggest that mixotrophs like Lepidodinium sp. would become more heterotrophic with higher growth rates in warming oceans. The subsequent changes in their functional role from primary producers to consumers may affect food web dynamics and carbon and nutrient cycling.

Abstract Tuning the interfacial structure of metal oxide substrates is an essential strategy to induce electronic structure reconstruction of supported catalysts, which is of great importance in optimizing their catalytic activities. Herein, vanadium oxides‐supported Ir catalysts (Ir‐V 2 O 3 , Ir‐VO 2 , and Ir‐V 2 O 5 ) with different interfacial bonding environments (Ir‐V, Ir‐O bri , and Ir‐O, respectively) were investigated for hydrogen evolution reaction (HER). The regulating mechanism of the influence of different interfacial bonding environments on HER activity was investigated by both experimental results and computational evidence. Benefiting from the unique advantages of interfacial Ir‐V direct metal bonds in Ir‐V 2 O 3 , including enhanced electron transfer and electron donation ability, an optimized HER performance can be obtained with lowest overpotentials of 16 and 26 mV at 10 mA cm −2 , high mass activities of 11.24 and 6.66 A mg −1 , and turnover frequency values of 11.20 and 6.63 s −1 , in acidic and alkaline conditions respectively. Furthermore, the assembled Ir‐V 2 O 3 ||RuO 2 anion exchange membrane (AEM) electrolyzer requires only 1.92 V to achieve a high current density of 500 mA cm −2 and realizes long‐term stability. This study provides essential insights into the regulating mechanism of interfacial chemical bonding in electrocatalysts and offers a new pathway to design noble metal catalysts for different applications.

PTs in the eastern Indian Ocean (EIO), surface water of Strait of Malacca (SSM), and coastal waters of Sri Lanka (SSL). All the detected PTs were phycourobilin (PUB) containing PT 3 and showed distinct distribution patterns. Low PUB PT 3a and partial chromatic acclimater PT 3eA dominated in coastal and shallow waters (SSM and SSL). In contrast, high PUB and chromatic acclimaters PT 3dA and PT 3c/3dB were mainly distributed in open ocean (EIO). PT 3dA and PT 3c/3dB occurred at similar depths of the lower euphotic layers but showed distinct distribution pattern that are partially exclusive, indicating that they compete with each other for the same light niche. Interestingly, the newly described PT 3f was detected with high relative abundances at all stations and particularly dominated in the upper euphotic layer in EIO, which was confirmed with PT-specific quantitative polymerase chain reaction (qPCR). The relative abundance of PT 3f was negatively correlated with nutrient level, implying that PT 3f is adapted to oligotrophic waters. Pronounced niche partition of different PTs was observed in the upper and lower layers of euphotic zone in EIO and SSM/SSL. Light, nutrients, and strong stratification may play important roles in the niche partition of different PTs. Further analysis about ecologically significant taxonomic units revealed high diversity within each PT at different locations, which provided insights for understanding specific PT with wide range of niches.

Low-cost and convenient methodologies to produce uniform droplets are demanded for the detection and quantification of environmental DNA (eDNA). In this work, we demonstrate that hydrogel-beads templated emulsification is applicable to generate monodispersed droplets within one minute via vortexing and pipetting. Compartmentalized reactions via the beads-templated digital PCR (bdPCR) have been further conducted to amplify the targeted region of a seahorse species genome. The results from bdPCR have shown a similar limit of detection compared with the traditional water-in-oil based droplet digital PCR (ddPCR). SYBR green staining results further demonstrated the successful amplification of target templates through bdPCR. Finally, the bdPCR platform was adopted to amplify eDNA from marine water and the results showcased the successful detection of a seahorse species.

Domoic acid (DA) is a neurotoxin produced by certain species of Pseudo-nitzschia (PSN) that can cause damage to neural tissues and can be fatal to marine animals. Copepods, direct consumers of PSN, exhibit remarkable resistance to DA. Given that gut microbiota facilitate various detoxification processes in copepods, we hypothesize that gut microbiota may play a crucial role in aiding copepods in DA detoxification. In this study, we investigated the detoxification capability of copepod gut microbiota by feeding both wild-type and gut-microbiota-free Acartia erythraea toxic PSN. Our results demonstrated that the presence of gut microbiota enhanced the survival of copepods exposed to a DA diet. We subsequently feed A. erythraea both toxic and non-toxic PSN, and explored the potential mechanisms of DA detoxification through amplicon and metatranscriptome approaches. We identified Aureispira sp., Oceanospirillum sp., and Tenacibaculum sp. as key DA detoxification taxa because they not only exhibited high relative abundance in the toxic diet but also played an important role in two established DA biotransformation pathways. We speculate that the gut microbiota of A. erythraea transform DA into non-toxic substances through these two established pathways via decarboxylation, dehydrogenation, carboxylation, and multiple oxidation processes. Overall, our findings elucidate the mechanisms by which copepod gut microbiota detoxify DA, thereby advancing our understanding of copepod resilience in the face of a toxic diet.

Abstract Mesoscale eddies are found almost everywhere in global ocean. They can last for weeks to months with scales up to over 100 km and play important roles in global biogeochemical cycles. In this study, we analyzed the phylogenetic and pigment type composition of Synechococcus in a cyclonic eddy (CE, cold eddy) and an anticyclonic eddy (ACE, warm eddy) located in western South China Sea in summer, 2018. Nutrients pumping enhanced Synechococcus abundance markedly in the upper euphotic layers of CE. High diversity of both phylogenetic clades and pigment types of Synechococcus were discovered in the sampling area, with clear composition difference between CE and ACE. The chromatic acclimating pigment type (PT) 3dA dominated in CE while PT 3dB dominated in ACE. The potential weak chromatic acclimator PT 3eA contributed a significant proportion in both CE and ACE. To better understand the difference of PT composition in CE and ACE, we further investigated the phylogenetic composition of Synechococcus in CE and ACE. Clade CRD 1, which were the main strains in upwelling regions, were dominant in CE, where cooler and nutrient rich subsurface water was pumped to the upper layers. Warm water adapted clade II and clade III dominated in ACE. Our study, for the first time, indicated that chromatic acclimation was important in shaping the vertical profile of Synechococcus community in mesoscale eddies of the subtropical oceans.

Abstract L‐RNA aptamers have been developed to target G‐quadruplexes (G4s) and regulate G4‐mediated gene expression. However, the aptamer selection process is laborious and challenging, and aptamer identification is subject to high failure rates. By analyzing the previously reported G4‐binding L‐RNA aptamers, we found that the stem‐loop (SL) structure is favored by G4 binding. Herein, we present a robust and effective G4‐SLSELEX‐Seq platform specifically for G4 targets by introducing a pre‐defined stem‐loop structure library during the SELEX process. Using G4‐SLSELEX‐Seq, we identified an L‐RNA aptamer, L‐Apt1‐12, for the Epstein–Barr nuclear antigen 1 ( EBNA1 ) RNA G4 (rG4) in just three selection rounds. L‐Apt1‐12 maintained the stem‐loop structure initially introduced, and possessed a unique G‐triplex motif that is important for the strong binding affinity and specificity to EBNA1 rG4. L‐Apt1‐12 effectively downregulated endogenous EBNA1 protein expression in human cancer cells and showed selective toxicity towards Epstein–Barr virus (EBV)‐positive cancer cells, highlighting its potential for targeted therapy against EBV‐associated cancers. Furthermore, we demonstrated the robustness and generality of G4‐SLSELEX‐Seq by selecting L‐RNA aptamers for the amyloid precursor protein ( APP ) rG4 and the hepatitis C virus subtype 1a ( HCV‐1a ) rG4, obtaining high‐affinity aptamers in three selection rounds. These findings demonstrated G4‐SLSELEX‐Seq as a robust and efficient platform for the selection of rG4‐targeting L‐RNA aptamers.

Industrial activities increasingly release toxic pollutants into water bodies, threatening ecological and human health. Harmful algal blooms (HABs) are a critical concern, often resistant to traditional water treatment methods, highlighting the need for innovative, eco-friendly solutions. This study evaluates advanced materials, including layered Fe 3 O 4 @ZIF8, core-shell Fe 3 O 4 @ZIF8, FeCN, BiOBr, and CuBDC, to inhibit bloom-forming algae under visible and UV light. BiOBr demonstrated superior performance at low concentrations, effectively inactivating Microcystis aeruginosa. Chlorophyll pigment and phycobiliprotein content analysis revealed its mechanism of action. As a cost-effective and sustainable solution, BiOBr offers promise for mitigating HABs, protecting ecosystems, and enhancing water quality. This research highlights the transformative potential of novel materials in addressing global water pollution challenges.