Dead Algae Research Articles

Removal of levofloxacin from aqueous solutions by using micro algae: optimization, isotherm, and kinetic study

This study was focused on the response surface methodology modeling of the removal of levofloxacin residue using microalgae as adsorbent. The microalgae categories Cladophora was characterized by Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) analysis techniques. The efficacy of LEV removal was evaluated by the historical data of different variables (time, pH, algal dosage, and LEV concentration) using Central Composed Design (CCD). The predicted results of the model demonstrated that the expected responses are reasonably close to the actual data, demonstrating the efficiency of this method in producing an accurate prediction. The model was found to be significant based on its coefficient of determination, which was 0.914, along with the fitted and projected values of 0.9029 and 0.8967. Furthermore, the results of the predicted reaction optimization showed that the maximum LEV elimination could be achieved within a time of 90 min, a pH of 6 and 0.2 g/L of micro algae. The model was validated experimentally with 95.45 % of LEV elimination efficiency. In addition, it is observed that the LEV removal process followed Langmuir model and pseudo-second order kinetic in majority of the cases with R2 of 0.9959. As a result of the dead algae's simple use and high adsorption effectiveness, the results demonstrated the possible use of antibiotics in aqueous solutions.

Kinetic and thermodynamic investigations of copper (II) biosorption by green algae Chara vulgaris obtained from the waters of Dal Lake in Srinagar (India)

Intake of copper (II) heavy metal ions beyond certain permissible limit raises the risk of cancer, liver damage, stomach discomfort and kidney failure. In present study dead green algae Chara vulgaris was used as a sorbent for the elimination of copper (II) from eutrophicated water of Dal Lake in Srinagar India. The roles of pH, equilibrium time and initial copper (II) concentration were evaluated in the said biosorption process. Various analyses, including FTIR, FE-SEM/EDX, HR TEM, XRD, and BET tests, were conducted to understand the copper (II) biosorption mechanism. In present investigation the adsorption of copper (II) ions (from 100 ppm concentration of copper (II) solution) was maximum (about 70 %± 1.5) under conditions; pH 5, equilibrium time 60 min, adsorbent dosage 0.5 g in 50 mL of copper (II) solution, and temperature of 20 °C. The adsorption was better fitted by the pseudo-second-order rate model. The experimental findings indicated the Langmuir model was better suited to the given adsorption processes. The said model demonstrated the involvement of both physical and chemical factors underlying the mechanism of process. The values of thermodynamic parameters ΔG0, ΔH0, and ΔS0under given experimental conditions indicated the process to be spontaneous. Moreover, this work presents a fresh approach for environmentally friendly and affordable extraction of copper (II) from wastewater, utilizing algae Chara vulgaris as a biosorbent. The unique biochemical composition of Chara vulgaris demonstrates a remarkable affinity for copper (II) ions, offering a sustainable approach to mitigate copper pollution.

Mapping the distribution of sea urchin (Echinoidea) and benthic habitat using drone in the waters of Lancang Island

Sea urchins are valuable marine creatures that live in the waters of Indonesia, and typically found in seagrass and coral reefs. This study aimed to determine the distribution of sea urchins and the benthic characteristics that serve as their habitat using high resolution drone images. Object-based image analysis (OBIA) with a support vector machine algorithm is used to identify benthic habitats, while the distribution of sea urchins is determined by thresholding pixel values. A total of 812 aerial photos with a spatial resolution of 3.98 cm/px were obtained and mapped into five classes of benthic habitat (sand, rubble, seagrass, living coral, and dead coral algae). The dominant habitat class obtained was dead coral algae, with an area of 234,035 m2 (29.63%), whereas seagrass was the smallest, with an area of 74,149 m2 (9.39%). The overall accuracy of the benthic classes was 65.44%, with kappa coefficient value of 0.57. The study found that the total number of sea urchins on Lancang Island was 61,551. The dominant distribution of sea urchins was found in the living coral class with 18,094 individuals, but the highest density was in the rubble class with 1358 individuals/ha.

Tracking coral loss in the Spermonde Archipelago of Indonesia: 32 years of satellite monitoring from 1990 to 2022

ABSTRACT An alarming amount of damage has occurred to coral reefs in Indonesia, with the causes of such damage either from human activities (anthropogenic causes) or natural processes. This study investigated the long-term dynamic changes in coral reef habitats in eight selected islands in the Spermonde archipelago, Indonesia, using remote sensing and historical information. A series of Landsat images recorded in different years (i.e. 1990, 1996, 2002, 2008, 2013, 2016, 2018, 2019, and 2022) were used to map the benthic habitats of each island (i.e. live coral, dead coral, seagrass, sand, rubble, mix bottom). The analysis estimated a total of 303.47 hectares or 76.26% loss of live coral in studied islands since 1990. In contrast, there was a substantial increase in dead coral algae and rubble, estimated at around 108.63 and 101.91 hectares, respectively. Strong and similar negative coefficient determination between live coral cover with both dead coral algae (R2 = 0.96, Y = -2.95) and rubble (R2 = 0.94, Y = -2.85) suggested that human activities (e.g. destructive fishing activities, damage from anchors, coral mining) and natural processes (e.g. sedimentation, coral bleaching, coral diseases, and coral predation) played comparable roles in coral reef degradation in Spermonde Archipelago. Furthermore, this study revealed that destructive fishing occurred on the island regardless it was inhabited or uninhabited and was influenced by the extent of its live coral cover. This study overall highlighted the ongoing degradation and factors contributing to coral loss in the Spermonde archipelago. Further research and monitoring efforts are necessary to understand the mechanisms driving the decline in live coral and the factors contributing to increases in dead coral algae and rubble. This knowledge will aid in developing targeted conservation strategies and management plans to protect the coral reef ecosystem in the Spermonde Archipelago and other affected regions in Indonesia.

Shallow sea waters habitat mapping in 2018 and 2022 using Sentinel-2 Imagery with OBIA Method at Kelapa Dua Island, Seribu Island, Jakarta Province, Indonesia

Shallow sea habitat has a very important role as a place to live and shelter for various types of organisms. Mapping this area needs to be done regularly considering the many benefits it has and the tendency for this area to change, one of them is by using remote sensing technology with the object-based image analysis (OBIA) method. OBIA classification includes the process of image segmentation and classification of all segmentation results. In the segmentation process using scale 100 at level 1 and scale 10 at level 2. Furthermore, at the classification process, 6 (six) habitat classes are obtained, namely sand, coral, macroalgae, sea grass, rubble and dead coral algae. The overall accuracy value in 2018 showed a value of 70%, and in 2022, it showed a value of 70.77%. The kappa coefficient value is 0.617 in the 2018 image acquisition and 0.612 in the 2022 image acquisition. The analysis carried out showed that there was a change in each habitat with the habitat that experienced the greatest changes are sand and dead coral algae class.

Electrokinetic motion and viability assessment of algae with a polyethylene glycol-dextran interface.

At present, there is still limited report on the electrokinetic (EK) behavior of bioparticles at the interface of an aqueous two-phase system. In this paper, the EK motion and viability assessment of live algae mixed with the NaClO treated dead algae were carried out at the interface formed by polyethylene glycol (PEG)-rich phase and dextran (DEX)-rich phase in a straight microchannel. The experimental results show that both the live and dead algae at the PEG-DEX interface migrate from the negative electrode to the positive electrode, and the EK velocity of live algae at the interface is slightly larger than that of the dead ones with similar diameters. For either live or dead algae, the EK velocity at the interface decreases with the increase in diameter. A size-velocity curve was used to evaluate the viability of the algae. As most of the microorganisms in ballast water are algae, the method in this paper provides a promising way to detect and evaluate the live microorganism in treated ballast water of a ship.

Visible light photocatalysis alleviates ceramic membrane fouling caused by intracellular organic matter of Microcystis aeruginosa

Ultrafiltration (UF) is an effective technology for treating algae-containing water. The algal intracellular organic matter (IOM) released by dead algae during an excessive algae growth phase causes more serious membrane fouling than viable algal cells and algal extracellular organic matter (EOM), which seriously restricts stable operation of UF. This paper studied the removal of IOM by a Bi2O3–TiO2/PAC (Bi-doped TiO2 nano-composites supported by powdered activated carbon) photocatalytic oxidation-ceramic ultrafiltration membrane, the inhibitory effect of membrane fouling at different photocatalytic oxidation times, and the fouling mechanism. The results show that both the adsorption and photocatalytic oxidation of Bi2O3–TiO2/PAC can significantly remove proteinoids and humic acid-like fluorescent components present in IOM, with removals of UV254 and DOC reaching up to 81.8% and 44.0%. The generated superoxide radicals and hydroxyl radicals positively affect the degradation of organic compounds of various molecular weights, and holes mainly degrade acidic low-molecular weight organic compounds. When the photocatalytic oxidation time was extended to 60 min, the membrane flux increased by 70.7% and the reversible resistance and irreversible resistance decreased by 83.4% and 90.1%, respectively. Under these conditions, the fouling mechanism changed from complete blockage to intermediate blockage. In the late stage of photocatalytic oxidation (90–120min), part of the high and medium molecular weight organic components were oxidized to produce low-molecular weight organic compounds (LMW acidic and neutral organic compounds), and blockage of filter cake became the main fouling mechanism. After photocatalysis, the zeta potential decreases significantly and the interaction forces between pollutants and pollutants are transformed into repulsive forces. Application of an appropriate photocatalytic oxidation time can alleviate the ultrafiltration membrane fouling caused by algal-derived organics.

Vitality of mycobionts and photobionts after passing through the digestive tract of Constrictotermes cyphergaster (Isoptera) workers.

Termites are among the insects that consume lichens and may be potential dispersers of these symbionts. This study evaluated the vitality of photobionts and mycobionts after passing through the digestive tract of Constrictotermes cyphergaster. The percentage of live and dead algae was verified throughout the alimentary canal of 450 workers, originating from five sampled colonies in the Caatinga Dry Forest, NE, Brazil. A progressive growth in algae mortality was observed in the crop, paunch and rectum, however more than 40% of the algae found in faeces presented signs of vitality. Photobiont morphology was different between cells extracted from thallus in natura and algae present in termite faeces. The photobiont cells presented more shrunken cytoplasms after passing through the alimentary canal of C. cyphergaster. There was also an increase between the cell wall space and the cytoplasm membrane of algae found in the termite faecal pellets. Only four broken spores were found in the intestine, which made the vitality analysis unfeasible for these cells. The record of photobiont vitality in termite faecal pellets is indicative of endozoochoric dispersal, suggesting that this relationship between insects and lichens extends beyond a trophic interaction.

Consortiums «tumbleweeds» of the Amurskii liman

For the first time, the «tumbleweeds» – consortia of the Amur estuary were studied. The determinants of consortia are fragments of brown algae-macrophytes thalli and colonies of hydroid polyps, rolled up into a ball by currents, and the consorts are amphipods inhabiting it. It was show that the reason for the emergence of consortative relationships is the hydrological conditions of the estuary and features of it bottom landscape, under which amphipods are forced to seek shelter. In the diet of the kaluga Huso dauricus and Amur sturgeon Acipenser schrenckii in the Amur Estuary, amphipods were found together with plant remains, which indicates the feeding of sturgeons by consortia. Kaluga, in comparison with the Amur sturgeon, consumes such type food much more often and in greater quantities. Animals associated with the aggregation of dead algae and polyps play a significant role in the formation of the food base for sturgeons in the Amur Estuary.

Fluorescent signatures of autochthonous dissolved organic matter production in Siberian shelf seas

The East Siberian Sea is an area of high biogeochemical activity caused by multiple factors, such as an influence of river runoff, Atlantic, and Pacific waters, formation and melting of sea ice, and internal circulation. Extensive amounts of carbon are accumulated in sub-sea permafrost within the Arctic shelf in East Siberia. Thawing permafrost and resulting microbial decomposition of frozen carbon pool is a potential feedback process affected global climate dynamics. Several studies of dissolved organic carbon (DOC) distribution in the East Siberian Sea have demonstrated untypical for other Arctic shelf seas pronounced non-conservative DOC behavior. Using seawater samples from the 69th cruise of R/V Akademik Mstislav Keldysh conducted in the Laptev and East Siberian seas in September 2017, this study examines the distribution of fluorescent dissolved organic matter (FDOM) along the shelf-crossing transects including the areas affected by the Khatanga, Lena, Indigirka, and Kolyma river runoff. The set of 137 excitation-emission matrices (EEMs), analyzed with Parallel Factor analysis (PARAFAC), was described by a 4-component model demonstrating Tucker’s congruence coefficient above the 0.95 threshold. Spectral characteristics of the resulting components allowed identifying them as well-known humic-like A and C, protein-like B/T, and marine humic-like M fluorophores. Component C1 (A fluorophore) showed a good correlation with salinity for different river plume influenced regions. As well as chromophoric DOM (CDOM) absorption, it can be used as marker of input of terrestrial DOM to the Arctic Ocean. A distinctive feature of the East Siberian Sea shelf waters in comparison with the Laptev Sea is the higher content of the C2 and C4 components, exhibiting protein-like and marine humic-like fluorescence. Component C3 (C fluorophore) which is usually identified as terrestrial-derived material, was found to be produced locally on the East Siberian Sea shelf and in the continental slope region of the Khatanga transect. Destruction of dead algae cells, production of marine biota and dissolved organic matter (DOM) reworking are considered as possible autochthonous FDOM sources in the Siberian shelf seas.

Mathematical study of Algae as a bio-fertilizer using fractal–fractional dynamic model

Algae plays a vital role as bio-fertilizer and soil stabilizer in the field of agriculture. This paper considers a fractal–fractional dynamics model in sense of Caputo derivative that study the reuse of detritus generated by the dead algae as fertilizer for crop. In particular, we study dynamics model in which algae recovers nitrogen and phosphorus (waste nutrients) from water and is reused to enhance agricultural production. The theoretical results are established for the considered model with the aid of fixed point theory, whereas Ulam–Hyers approach is used for the stability of system. The numerical simulations are computed by using the well-known technique of fractional Adams–Bashforth. For simulation of the problem we consider different values for fractional order and fractal dimension by using some pre-existing data. Several graphical representation is given to understand the system at different fractional order and fractal dimension.

Community of juvenile hard corals (Scleractinia) in different geomorphological type and reef benthic communities

Juvenile corals are an important stage in the life history and demographics of coral populations in nature however, their survival is influenced by the physical environment and benthic coral reef communities. The study of juvenile coral communities with a maximum size of 10 cm on the reefs of Pulau Weh, Sabang, Aceh was conducted to observe juvenile coral communities and determine their relationship with geomorphological types and benthic reefs communities. A total of 9 sites with 72 sampling squares were distributed in different geomorphological; tectonic type with hard substrates of lava and limestone, volcanic type with predominantly sand substrate, and dead coral with algae with the presence of hot springs in the vicinity. In total, we found 25 genera of juvenile corals from 12 families, and the abundance reached 449 colonies with an average of 37.41 colonies per site. The mean density was 6.66 ± 5.99 colonies/m2 (±SD) and varied significantly between sites (p=4.878-7; <0.05), which was dominated by the genera Porites, Pavona, Acropora, Montipora, and Favia. Live coral cover (HC), dead coral algae (DCA), and hard rock substrate (RK) did not affect, however rubble coral (R) was significantly affected (p=1.9-2; <0.05). Geomorphological conditions and benthic reef cover did not show a significant effect (p = 0.48; < 0.05), although juvenile corals were very common and better in the tectonic type than the volcanic type. The survival of juvenile corals was low, where the smaller size was significantly high compared to the larger size (p=4.5-5; <0.05). Our study provides up-to-date information and data on juvenile coral communities based on geomorphological conditions and local benthic reef communities.

A techno-economic approach for eliminating dye pollutants from industrial effluent employing microalgae through microbial fuel cells: Barriers and perspectives

Microbial fuel cells are biochemical factories which besides recycling wastewater are electricity generators, if their low power density can be scaled up. This also adds up to work on many factors responsible to increase the cost of running a microbial fuel cell. As a result, the first step is to use environment friendly dead organic algae biomass or even living algae cells in a microbial fuel cell, also referred to as microalgal microbial fuel cells. This can be a techno-economic aspect not only for treating textile wastewater but also an economical way of obtaining value added products and bioelectricity from microalgae. Besides treating wastewater, microalgae in its either form plays an essential role in treating dyes present in wastewater which essentially include azo dyes rich in synthetic ions and heavy metals. Microalgae require these metals as part of their metabolism and hence consume them throughout the integration process in a microbial fuel cell. In this review a detail plan is laid to discuss the treatment of industrial effluents (rich in toxic dyes) employing microbial fuel cells. Efforts have been made by researchers to treat dyes using microbial fuel cell alone or in combination with catalysts, nanomaterials and microalgae have also been included. This review therefore discusses impact of microbial fuel cells in treating wastewater rich in textile dyes its limitations and future aspects.

Status Terkini Tutupan Terumbu Karang di Perairan Dangkal Pulau Bedil, Desa Labuan Bajo, Kabupaten Sumbawa, NTB

Bedil Island is included in the Keramat, Bedil, and Temudong Small Island Park (TPK), which was approved by the Regent of Sumbawa. Administratively, this island is included in the Labuan Bajo Village area, Sumbawa, NTB. There is the existence of coral reef ecosystems in these waters that form a reef flat and reef slope profile, that stretches to the southwest and northeast. By its designation as a small island park, the coral reefs in Bedil Island are used as an underwater tourism object. This study aims to determine the current condition of coral reef cover in the waters around Bedil Island, especially in the eastern and southern parts of the island. Coral reefs in the north and west area are limited and there is the existence of seagrass beds. The line intercept transect method is carried out by spreading the roll meter as far as 50 meters on the east and south sides of the island with a depth of 2-3 meters. The coral lifeform that is tangent with the roll meter is then recorded and then analyzed for the average percent cover, clustering status, and coral mortality index. Coral reefs in the eastern and southern parts of Bedil Island are classified as very good/excellent because they have a percent cover value above 75%. In addition, the coral mortality index value is also relatively small which indicates that the corals are living well. Clearwater conditions and locations far from human settlements are thought to be factors that support coral survival. However, the presence of dead coral algae and rubble still indicates a threat of damage even though the value is small. Algae life on the surface of dead coral also indicates that the coral has been dead for a long time.

Revisiting the isolation source after half a century: Emericellopsis mirabilis on a yellow-green alga.

Fungi-algae interactions, such as lichen-forming fungi and parasitic chytrids on phytoplankton, are common in ecosystems. In contrast, interactions between filamentous fungi and soil algae that can be observed with the naked eye have been given little attention and remain unexplored. Here, we report a fungus that was associated with a visible symptom of dead algae on a soil surface in Sugadaira-kogen, Nagano, central Japan. Acremonium-like conidiophores were growing on vesicles and dead bodies of a yellow-green alga, Botrydium granulatum. The fungus was identified as Emericellopsis mirabilis based on its morphology by microscopic observation, phylogenetic analysis, and the similarity of the isolation substrate with the first description of the species. Co-culture experiments showed a filamentous cell differentiation of the alga by the fungus, but no harmful or beneficial effects on algal growth. Therefore, we speculate that E. mirabilis is a facultative parasite of B. granulatum under natural conditions.

The exacerbation of mercury methylation by Geobacter sulfurreducens PCA in a freshwater algae-bacteria symbiotic system throughout the lifetime of algae

Mine-polluted wastewater with mercury (Hg) poses severe environmental pollution since Hg(II) can be converted to highly neurotoxic methylmercury (MeHg) under anaerobic conditions. Previous studies on Hg methylation have focused on aquatic sediments, but few have investigated the MeHg formation in water layers containing algae. In this study, we investigated the dynamic effect of algae on Hg methylation throughout the lifetime of algae. We found that Chlorella pyrenoidosa was a non-methylating alga and exhibited good tolerance to Hg stress (1–20 μg/L); thus Hg(II) could not inhibit the process of eutrophication. However, the presence of C. pyrenoidosa significantly enhanced the Hg methylation by Geobacter sulfurreducens PCA. Compared to the control sample without algae, the MeHg production rate of algae-bacteria samples remarkably exacerbated by 62.3–188.3% with the algal growth period at cell densities of 1.5 × 106–25 × 106 cells/mL. The increase of algal organic matter and thiols with the algal growth period resulted in the exacerbation of MeHg production. The Hg methylation was also enhanced with the presence of dead algae, of which the enhancement was ~62.4% lower than that with the presence of live algae. Accordingly, the potential mechanism of Hg methylation in a freshwater algae-bacteria symbiotic system throughout the algal lifetime was proposed.

Electrokinetic detection and separation of living algae in a microfluidic chip: implication for ship's ballast water analysis.

Detecting living algae from treated ship's ballast water is an important task for port state control (PSC) under the requirement of the International Ballast Water Convention. In this paper, electrokinetic detection and separation of living algae from NaClO- and UV-treated ship's ballast water in a microfluidic chip are presented. The electrokinetic movement of algae in a straight poly ethylene glycol (PEG)-modified PDMS microchannel filled with 10% PEG solution was measured by using an optical microscope. The experimental results show that the moving velocity of dead algae is lower by more than 80% in comparison with living algae. The decreased velocity is larger for larger dead algae and the velocity is decreased to zero for dead algae larger than 6μm in diameter. A curve was obtained to evaluate the vitality of algae with similar moving velocity but different sizes. Electrokinetic separation of living algae from a mixture sample in a straight channel was also achieved. The method presented in this paper provides a moving velocity-based approach for quickly evaluating the living status of algae in treated ship's ballast water.

Identification of living and dead microalgae cells with digital holography and verified in the East China Sea

The death of microalgae plays an important role in ocean energy flow and material circulation. The existing methods for the identification of dead and living microalgae cells all have defects such as the need for staining and pre-treatment. In this work, a label-free method to identify living and dead algae cells based on digital holography microscopy and machine learning was designed. At the stage of model training, ten feature vectors were extracted from the holograms, and twelve classification models of machine learning algorithm were trained. Compared with the staining method results, the accuracy of this method can reach 94.8%. At the stage of field verification, the death rate calculated by this method was also consistent with staining method. The method proposed in this paper provides a new method for the study of marine microalgae death which has the advantages of label-free, non-invasive, high accuracy and potential for in-situ application.

Green and Cost-Effective Synthesis of Metallic Nanoparticles by Algae: Safe Methods for Translational Medicine.

Metal nanoparticles (NPs) have received much attention for potential applications in medicine (mainly in oncology, radiology and infectiology), due to their intriguing chemical, electronical, catalytical, and optical properties such as surface plasmon resonance (SPR) effect. They also offer ease in controlled synthesis and surface modification (e.g., tailored properties conferred by capping/protecting agents including N-, P-, COOH-, SH-containing molecules and polymers such as thiol, disulfide, ammonium, amine, and multidentate carboxylate), which allows (i) tuning their size and shape (e.g., star-shaped and/or branched) (ii) improving their stability, monodispersity, chemical miscibility, and activity, (iii) avoiding their aggregation and oxidation over time, (iv) increasing their yield and purity. The bottom-up approach, where the metal ions are reduced in the NPs grown in the presence of capping ligands, has been widely used compared to the top-down approach. Besides the physical and chemical synthesis methods, the biological method is gaining much consideration. Indeed, several drawbacks have been reported for the synthesis of NPs via physical (e.g., irradiation, ultrasonication) and chemical (e.g., electrochemisty, reduction by chemicals such as trisodium citrate or ascorbic acid) methods (e.g., cost, and/ortoxicity due to use of hazardous solvents, low production rate, use of huge amount of energy). However, (organic or inorganic) eco-friendly NPs synthesis exhibits a sustainable, safe, and economical solution. Thereby, a relatively new trend for fast and valuable NPs synthesis from (live or dead) algae (i.e., microalgae, macroalgae and cyanobacteria) has been observed, especially because of its massive presence on the Earth’s crust and their unique properties (e.g., capacity to accumulate and reduce metallic ions, fast propagation). This article discusses the algal-mediated synthesis methods (either intracellularly or extracellularly) of inorganic NPs with special emphasis on the noblest metals, i.e., silver (Ag)- and gold (Au)-derived NPs. The key factors (e.g., pH, temperature, reaction time) that affect their biosynthesis process, stability, size, and shape are highlighted. Eventually, underlying molecular mechanisms, nanotoxicity and examples of major biomedical applications of these algal-derived NPs are presented.

Mechanism for the enrichment of organic matter in the Liushagang Formation of the Weixinan Sag, Beibuwan Basin, China

Eocene lacustrine organic-rich shales, mudstones and shales in the middle member of Liushagang Formation (designated as LS2) are the most important source rocks in the Beibuwan Basin located in the northwest of the South China Sea. In this study, we explored the mechanisms responsible for the accumulation of organic matter in source rocks from LS2 of Weixinan Sag by investigating the paleoclimate, paleoredox, paleoproductivity and lithological characteristics of the parent rocks using biomarkers and elemental geochemistry data. Based on our analytical data, the deposition of the source rocks from LS2 occurred in a warm, humid paleoclimate with moderate chemical weathering, as indicated by CIA indexes and Sr/Cu ratios. The Sr/Ba ratios and gammacerane indexes indicated that the source rocks from LS2 were deposited in a freshwater paleolake. The Corg/P ratios and Redox Sensitive Elements (RSEs) -TOC bivariate diagrams demonstrated that the organic-rich shales and mudstones/shales deposited under anoxic and oxic-suboxic conditions, respectively. The levels of TOC, copper (Cu), molybdenum (Mo) and C30 4-methylsterance index in the organic-rich shales were higher than those of the mudstones and shales, indicating greater algae bloom and paleoproductivity during the deposition of the organic-rich shales compared to during the sedimentation of the mudstones and shales. Combined with La/Yb-∑REE, SiO2–TiO2, Al2O3/TiO2, Nb/Ta and Cr/Co ratios, it is considered that the parent rocks of the organic-rich shales were granite of relatively intermediate lithological compositions, with greater levels of nutrients such as phosphorus (P), Mo, Cu, compared to those of the mudstones and shales. Large-scale decomposition of dead algae led to oxygen depletion, which created favorable conditions for the preservation of organic matter and the release of P from the sediments to water. The increased content of P in water subsequently aggravated algal blooms. Such a positive feedback loop was conducive to the formation of organic-rich shales. The inter-relationships of algal blooms (controlled by P), paleoproductivity and paleoredox conditions play an important role in the accumulation of organic matter in organic-rich shales from LS2 of Weixinan Sag, Beibuwan Basin.