Green Algae Research Articles

Dynamics of Phytoplankton Communities and Environmental Drivers in Chinese Mitten Crab Aquaculture Ponds: Highlighting the Need for Cyanobacteria Control

Pond culture is the primary method for cultivating Chinese mitten crab (Eriocheir sinensis), with phytoplankton significantly influencing their growth. Green algae benefit crab growth by serving as supplementary food, while cyanobacteria, particularly during blooms, hinder it and pose health risks. Environmental changes in nutrient levels, temperature, and light significantly affect phytoplankton communities in ponds, impacting both ecosystem stability and crab growth. However, there is a limited understanding regarding the patterns of phytoplankton changes within adult Chinese mitten crab culture ponds. This study conducted monthly collection and analysis of phytoplankton throughout the culture cycle in typical adult Chinese mitten crab culture ponds, concurrently measuring physical and chemical water parameters to explore the correlation between phytoplankton changes and environmental factors. The results revealed distinct seasonal variations in phytoplankton composition. Chlorophyta and Bacillariophyta, such as Chlorella, Pediastrum, and Cocconeis, predominated in spring, while Chlorophyta and cyanobacteria, such as Volvox, Anabaena, and Microcystis, dominated in summer, and cyanobacteria and Bacillariophyta, such as Microcystis, Dolichospermum, and Cocconeis, prevailed in autumn. Total phytoplankton density consistently increased throughout the culture period. Microcystis constituted the majority of cyanobacteria biomass throughout most months. Although the total phytoplankton biomass fluctuated, cyanobacteria biomass consistently rose each month, reaching a peak of 61.7 mg/L in October. Water temperature and pH emerged as the primary environmental drivers influencing changes in phytoplankton community structure. Cyanobacteria density reached its peak between 18 and 26 °C and at a pH range of 7.5–8.5. These findings highlight the need for environmental regulation and cyanobacteria control in Chinese mitten crab culture ponds, thus promoting the health and sustainability of the Chinese mitten crab culture.

Photostasis and photosynthetic adaptation to polar life.

Photostasis is the light-dependent maintenance of energy balance associated with cellular homeostasis in photoautotrophs. We review evidence that illustrates how photosynthetic adaptation in polar photoautrophs such as aquatic green algae, cyanobacteria, boreal conifers as well as terrestrial angiosperms exhibit an astonishing plasticity in structure and function of the photosynthetic apparatus. This plasticity contributes to the maintenance of photostasis, which is essential for the long-term survival in the seemingly inhospitable Antarctic and Arctic habitats. However, evidence indicates that polar photoautrophic species exhibit different functional solutions for the maintenance of photostasis. We suggest that this reflects, in part, the genetic diversity symbolized by inherent genetic redundancy characteristic of polar photoautotrophs which enhances their survival in a thermodynamically challenging environment.

Green Seaweed Caulerpa racemosa as a Novel Non-Small Cell Lung Cancer Inhibitor in Overcoming Tyrosine Kinase Inhibitor Resistance: An Analysis Employing Network Pharmacology, Molecular Docking, and In Vitro Research.

The marine environment provides a rich source of distinct creatures containing potentially revolutionary bioactive chemicals. One of these organisms is Caulerpa racemosa, a type of green algae known as green seaweed, seagrapes, or green caviar. This organism stands out because it has great promise for use in medicine, especially in the study of cancer. Through the utilization of computational modeling (in silico) and cellular laboratory experiments (in vitro), the chemical components included in the green seaweed C. racemosa were effectively analyzed, uncovering its capability to treat non-small cell lung cancer (NSCLC). The study specifically emphasized blocking SRC, STAT3, PIK3CA, MAPK1, EGFR, and JAK1 using molecular docking and in vitro. These proteins play a crucial role in the EGFR Tyrosine Kinase Inhibitor Resistance pathway in NSCLC. The chemical Caulersin (C2) included in C. racemosa extract (CRE) has been identified as a potent and effective agent in fighting against non-small cell lung cancer (NSCLC), both in silico and in vitro. CRE and C2 showed a level of inhibition similar to that of osimertinib (positive control/NSCLC drug).

Novel indazolylchromones: synthesis, fungicidal evaluation, molecular docking and aquatic toxicity prediction.

Fungal diseases cause substantial loss to agricultural crops, affecting both quantities and quality. Although several methods are used for preventing disease incidence, fungicides remain crucial for higher yields and better quality. But in the past, the efficacy of several fungicides has decreased due to increased cases of fungicide resistant. In our pursuit of new effective fungicides, we synthesised a series of twenty 2-Indazol-1-yl-chromen-4-one derivatives (6a- 6t). The characterization of synthesized compounds was performed by several spectroscopic methods including Infrared, Nuclear Magnetic Resonance (1H and 13C) and HRMS. Out of 20 synthesised compounds, 19 (6b- 6t) were found to be novel. All synthesised indazolylchromones showed very good antifungal activity against Sclerotium rolfsii and Fusarium oxysporum. Among the tested compounds, 6t and 6f exhibited very good fungicidal activity against S. rolfsii with an ED50 of 10.10mgL-1 and 16.18mgL-1, respectively. In case of Fusarium oxysporum compound 6f displayed good' activity with an ED50 value of 27.82mgL-1. Molecular docking study was done to predict the binding sites of most active compounds, 6t and 6f with Cytochrome P450 14alpha -sterol demethylase (CYP51) enzyme using molsoft software. The acute toxicity predictions the of synthesized compounds for fish (LC50,96 Hr), daphnid (LC50, 48 Hr) and green algae (EC50, 96Hr) and the chronic toxicity predictions (ChV) were assessed using Ecological Structure Activity Relationship (ECOSAR) model. As per ECOSAR prediction, all the chemicals are inside AD and not missing predictions.

Surface displayed MerR increases mercury accumulation by green microalga Chlamydomonas reinhardtii

Mercury is a highly toxic trace metal that can accumulate in aquatic ecosystems and when resent at high concentrations can pose risks to both aquatic life and humans consuming contaminated fish. This research explores the use of the metalloregulatory protein MerR, known for its high affinity and selectivity toward mercury, in a novel application. Through a cell surface engineering approach, MerR was displayed on cells of green alga Chlamydomonas reinhardtii. A hydroxyproline-rich GP1 protein was used as an anchor to construct the engineered strains GP1-MerR that expresses the fluorescent protein mVenus. The surface engineered GP1-MerR strain led up to five folds higher Hg2+ accumulation compared to the WT strain at concentration range from 10-9 to 10-7 M Hg2+. The binding of Hg2+ via MerR was specific and did not get significantly affected by major freshwater water quality variables such as Ca2+ and dissolved organic matter. The presence of other trace metals (Zn2+, Cu2+, Ni2+, Pb2+, Cd2+) in a same concentration range even resulted in 30–40 % increase in the accumulated Hg. Further, the engineered cells also demonstrated the ability to accumulate Hg2+ from the water extracts of the Hg-contaminated sediment samples. These results demonstrate a novel approach utilizing the cell surface display system in C. reinhardtii for its potential application in bioremediation.

Marine macroalgae and their associated bacterial communities affect larval settlement and survivorship of the coral Pocillopora damicornis

Macroalgae play crucial roles as major habitat-forming organisms in marine ecosystems, having significant impacts on coral recruitment and reef recovery. However, the interactions between marine macroalgae and coral larvae remain poorly understood. Furthermore, little is known whether differences in bacterial assemblages associated with macroalgae may play roles in this process. Here, we comprehensively investigated the impacts of different macroalgae and their associated microbiomes on larval settlement and survival of coral Pocillopora damicornis. The results revealed significant variations in larval settlement and survival rates when exposed to different macroalgal species. The highest settlement rate, reaching 90%, was observed in the presence of the red alga Hypnea pannosa, followed by green algae Caulerpa serrulata, C. racemosa, and brown algae Turbinaria gracilis, Sargassum polycystum. Correspondingly, similarities in bacterial compositions were observed between H. pannosa and C. racemosa, as well as between T. gracilis and S. polycystum, implying associated bacterial may be related with the algal functions. Furthermore, macroalgae that facilitate larval settlement exhibited higher abundances of amplicon sequence variants (ASVs) associated with the metabolism of dimethylsulfoniopropionate or the antagonism of known coral pathogens. However, the brown alga Padina boryana failed to induce larval settlement with survival rate of zero after 120 h. The algal species harbored more abundances of ASVs related to Rhizobiaceae. These findings highlight the significant impact of macroalgae and their associated microbiomes on coral recruitment, as they influence both larval settlement and survival rates.

Characterization of the far-red light absorbing light-harvesting chlorophyll a/b binding complex, a derivative of the distinctive Lhca gene family in green algae.

Prasiola crispa, an aerial green alga, exhibits remarkable adaptability to the extreme conditions of Antarctica by forming layered colonies capable of utilizing far-red light for photosynthesis. Despite a recent report on the structure of P. crispa's unique light-harvesting chlorophyll (Chl)-binding protein complex (Pc-frLHC), which facilitates far-red light absorption and uphill excitation energy transfer to photosystem II, the specific genes encoding the subunits of Pc-frLHC have not yet been identified. Here, we report a draft genome sequence of P. crispa strain 4113, originally isolated from soil samples on Ongul Island, Antarctica. We obtained a 92 Mbp sequence distributed in 1,045 scaffolds comprising 10,244 genes, reflecting 87.1% of the core eukaryotic gene set. Notably, 26 genes associated with the light-harvesting Chl a/b binding complex (LHC) were identified, including four Pc-frLHC genes, with similarity to a noncanonical Lhca gene with four transmembrane helices, such as Ot_Lhca6 in Ostreococcus tauri and Cr_LHCA2 in Chlamydomonas reinhardtii. A comparative analysis revealed that Pc-frLHC shares homology with certain Lhca genes found in Coccomyxa and Trebouxia species. This similarity indicates that Pc-frLHC has evolved from an ancestral Lhca gene with four transmembrane helices and branched out within the Trebouxiaceae family. Furthermore, RNA-seq analysis conducted during the initiation of Pc-frLHC gene induction under red light illumination indicated that Pc-frLHC genes were induced independently from other genes associated with photosystems or LHCs. Instead, the genes of transcription factors, helicases, chaperones, heat shock proteins, and components of blue light receptors were identified to coexpress with Pc-frLHC. Those kinds of information could provide insights into the expression mechanisms of Pc-frLHC and its evolutional development.

Ecotoxicological assessment of cyclic peptides produced by a Planktothrix rubescens bloom: Impact on aquatic model organisms

Cyanobacterial blooms, a natural phenomenon in freshwater ecosystems, have increased in frequency and severity due to climate change and eutrophication. Some cyanobacteria are able to produce harmful substances called cyanotoxins. These metabolites possess different chemical structures and action mechanisms representing a serious concern for human health and the environment. The most studied cyanotoxins belong to the group of microcystins which are potent hepatotoxins. Anabaenopeptins are another class of cyclic peptides produced by certain species of cyanobacteria, including Planktothrix spp. Despite limited knowledge regarding individual effects of anabaenopeptins on freshwater organisms, reports have identified in vivo toxicity in representatives of freshwater zooplankton by cyanobacterial extracts or mixtures containing anabaenopeptins. This study focused on the isolation and toxicity evaluation of the cyanotoxins produced in the 2022 Planktothrix rubescens bloom in Averno lake, Italy. The three main cyclic peptides have been isolated and identified by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and optical analyses as anabaenopeptins A and B, and oscillamide Y. Ecotoxicological tests on the aquatic model organisms Daphnia magna (crustacean), Raphidocelis subcapitata (algae), and Aliivibrio fischeri (bacterium) revealed that anabaenopeptins A and B do not generate significant toxicity at environmentally relevant concentrations, being also found a stimulatory effect on R. subcapitata in the case of anabaenopeptin A. By contrast, oscillamide Y displayed toxicity. Ecological implications based on ECOSAR predictions align with experimental data. Moreover, long-term exposure bioassays on different green unicellular algae species showed that R. subcapitata was not significantly affected, while Scenedesmus obliquus and Chlorella vulgaris exhibited altered growth patterns. These results, together with the already-known background in literature, highlight the complexity of interactions between organisms and the tested compounds, which may be influenced by species-specific sensitivities, physiological differences, and modes of action, possibly affected by parameters like lipophilicity.

An Arctic sea ice spring bloom driven and dominated by Dinoflagellates - a harbinger of the future sea ice?

The sea ice spring bloom is crucial for sustaining Arctic marine food webs, with sea ice algae serving as primary carbon sources for higher trophic levels. Despite the prevailing dominance of diatom species in sea ice spring blooms, our study highlights a notable deviation, showcasing a bloom driven by dinoflagellates. Through field sampling of first-year sea ice cores and subsequent analysis of physical and biogeochemical parameters, combined with amplicon sequencing of the 18S rRNA gene, we investigated the occurrence and implications of this significant dinoflagellate bloom, with a particular focus on Polarella glacialis. Our findings reveal that high irradiances at the top of the ice core, coupled with elevated nutrient availability and warm ice conditions, are key drivers of this phenomenon, as elucidated by redundancy analysis. Moreover, our results suggest a potential climate-driven decline in snow cover on sea ice, increased open leads, and thinner sea ice, which may favor the proliferation of dinoflagellates over diatoms. This alternative dinoflagellate-dominated bloom could have profound ecological consequences, given the enriched omega-3 fatty acid content of dinoflagellates, thereby influencing energy transfer within the Arctic marine food web. Furthermore, our study identifies the presence of not only Polarella glacialis but also Chytridinium, an ectoparasite on copepod eggs, and the green algae Ulothrix in relatively high abundances within the sea ice. These findings shed light on the intricate interplay between environmental factors and microbial community dynamics within Arctic sea ice ecosystems.

Co‐pyrolysis of cypress sawdust and green algae over Ni/ZrO2 catalyst: Syngas yield and carbon emission

AbstractIn order to promote syngas yield and reduce carbon emission, Ni loaded ZrO2 (Ni/ZrO2) catalysts were prepared for the co‐pyrolysis of cypress sawdust and green algae in a two stage fixed bed reactor. The syngas yield, syngas component, and carbon emission were investigated. The results showed that Ni/ZrO2 catalyst could obviously increase the combustible gas component in syngas. H2 content was increased from 7.5% (single component) and 8.12% (co‐pyrolysis) to 16.56% (catalytic pyrolysis). CO content was also increased from 19.62% (single component) and 19.46% (co‐pyrolysis) to 25.94% (catalytic pyrolysis). However the catalyst had a little effect on the syngas yield compared with single component pyrolysis and co‐pyrolysis. The pyrolysis temperature could make great influence on the carbon emission. The carbon emission reduction was increased from 33.32 to 234.25 g CO2 and from 105.94 to 369.23 g CO2, respectively for green algae and cypress sawdust.

Effects of Prolonged Leaching on the Acute Ecotoxicity of Spruce-Pine Oriented Strand Board for Plants

In this study, the ecotoxicological effects of a selected OSB material on three model plants (green freshwater algae Desmodesmus subspicatus, duckweed Lemna minor, and seeds of lettuce Lactuca sativa) were tested. A 24 h and 168 h leachate of the same OSB material was prepared. Mg, Si, Ca, K, Fe, Zn, Mn, and Na were found in the samples. Their higher residues were measured in the 168 h leachate. Biogenic elements (N, P, C) were not detected. The acute effect was relatively slow (for algae up to 26%, for duckweed up to 20%, and for lettuce seeds with stimulation up to 37%). Prolongation of the leaching time did not show any effect on the results of the plant tests. Acute toxicity for the three plant species used was slow.

Physiological and Biochemical Responses of the Green Tide-Forming Algae, Ulva Species, under Different Nutrient Conditions on Jeju Island, Korea

Physiological and Biochemical Responses of the Green Tide-Forming Algae, Ulva Species, under Different Nutrient Conditions on Jeju Island, Korea

WHIRLY proteins, multi-layer regulators linking the nucleus and organelles in developmental and stress-induced senescence of plants.

Plant senescence is an integrated programme of plant development that aims to remobilize nutrients and energy from senescing tissues to developing organs under developmental and stress-induced conditions. Upstream in the regulatory network, a small family of single-stranded DNA/RNA-binding proteins known as WHIRLYs occupy a central node, acting at multiple regulatory levels and via trans-localization between the nucleus and organelles. In this review, we summarize the current progress on the role of WHIRLY members in plant development and stress-induced senescence. WHIRLY proteins can be traced back in evolution to green algae. WHIRLY proteins trade off the balance of plant developmental senescence and stress-induced senescence through maintaining organelle genome stability via R-loop homeostasis, repressing the transcription at a configuration condition, and recruiting RNA to impact organelle RNA editing and splicing, as evidenced in several species. WHIRLY proteins also act as retrograde signal transducers between organelles and the nucleus through protein modification and stromule or vesicle trafficking. In addition, WHIRLY proteins interact with hormones, reactive oxygen species and environmental signals to orchestrate cell fate in an age-dependent manner. Finally, prospects for further research and promotion to improve crop production under environmental constraints are highlighted.

Element composition of several marine macrophytes (Crimea, Black Sea) and correlations with the element abundances in sediments and seawater

The study of the element accumulation in marine plants against the backdrop of permanently increasing environmental pollution is of particular importance due to the participation of these plants in biogeochemical cycles. The element abundances are highly variable and depend on both the macrophyte species and environment. The purpose of this study was to analyze the elemental composition of widespread marine plants of different taxonomic affiliations collected in the same area of the Black Sea coast. The contents of 74 elements in three species of lower (red, brown, green algae) and one species of higher plants (seagrass) were analyzed using inductively coupled plasma mass spectrometry. High contents of most elements were found in the red alga Ceramium ciliatum and in rhizomes of the seagrass Zostera noltei. In C. ciliatum, high metal bioaccumulation factors were found, which are dependent also on their concentration in the environment. Compared to the higher plant, all the macroalgae accumulated increased amounts of As and I. The seagrass proved to be a good concentrator of Mo and Sb, and relatively high contents of Mn, Co, Ni, Zn, Cd and Ir were registered in its leaves. High contents of Mg, S, Ge, Se and Ta were found in the green alga Ulva rigida, and elevated levels of Al, As, Sr, Zr, Ru, Rh, Pd, Ag, Ba and Re were noted in the brown alga Gongolaria barbata. The enrichment factors for most elements in the sediments were well above 1 with respect to both the local Late Pleistocene sediments and the upper continental crust. The strength of correlations between the element contents in the plants and sediments was found to decrease with the specific surface area growth and appeared to have a lower asymptotic limit of the sediments–seawater correlation strength.

Modeling the reactive oxygen species (ROS) wave in Chlamydomonas reinhardtii colonies

Reactive oxygen species (ROS) play a crucial role as signaling molecules in both plant and animal cells, enabling rapid responses to various stimuli. Among the many cellular mechanisms used to generate and transduce ROS signals, ROS-induced-ROS release (RIRR) is emerging as an important pathway involved in the responses of various multicellular and unicellular organisms to environmental stresses. In RIRR, one cellular compartment, organelle, or cell generates or releases ROS, triggering an increased ROS production and release by another compartment, organelle, or cell, thereby giving rise to a fast propagating ROS wave. This RIRR-based signal relay has been demonstrated to facilitate mitochondria-to-mitochondria communication in animal cells and long-distance systemic signaling in plants in response to biotic and abiotic stresses. More recently, it has been discovered that different unicellular microorganism communities also exhibit a RIRR cell-to-cell signaling process triggered by a localized stress treatment. However, the precise mechanism underlying the propagation of the ROS signal among cells within these unicellular communities remained elusive. In this study, we employed a reaction-diffusion model incorporating the RIRR mechanism to analyze the propagation of ROS-mediated signals. By effectively balancing production and scavenging processes, our model successfully reproduces the experimental ROS signal velocities observed in unicellular green algae (Chlamydomonas reinhardtii) colonies grown on agar plates, furthering our understanding of intercellular ROS communication.

Detailed observations of the life history and phylogenetic placements of the freshwater green alga Oocystaenium elegans (Oocystaceae, Trebouxiophyceae), with an emended description

SUMMARYOocystaenium elegans Gonzalves & Mehra (Oocystaceae, Trebouxiophyceae) was collected from a paddy field in Japan. Its life history was reexamined based on detailed observations of cultured material, and an emended description is given. This species is a large spindle‐shaped green alga that grows in puddles and paddy fields and has been reported in India, Nepal and Cuba. Reproduction occurs asexually via autospore formation and sexually via oogamy. Although this oogamy is considered to involve fertilization by globular egg cells and antherozoids, the results of the present study revealed that the egg cells (female cells) remained spindle‐shaped and became globular zygotes after fertilization. The place on the egg cells where the antherozoid attached swelled to become a receptive papilla, after which the antherozoid invaded. Phylogenetic analysis based on nuclear 18S small subunit ribosomal RNA gene sequences showed that O. elegans is included in the family Oocystaceae.

Lipid Characterization of Beach-Cast Seaweeds from Gran Canaria Island: Potential Use in Human and Animal Nutrition

Macroalgal wracks can be considered unpleasant for beach users and, consequently, they are usually collected from most touristic beaches and discarded. However, seaweeds are an important source of bioactive lipid compounds, such as phospholipids, glycolipids, and n-3 polyunsaturated fatty acids (n-3 PUFA), displaying multiple health-promoting properties, including antioxidant and antimicrobial activities. The aim of this study is to characterize the lipid composition of twelve marine seaweed species (two green, six red, and four brown species) from macroalgal wracks of Gran Canaria Island, and to evaluate their potential use for several purposes, including human and animal nutrition. Lipid content, lipid classes, and fatty acid profiles of isolated specimens from the macroalgal wracks were determined. Lipid contents ranged between 0.27 and 3.17% of dry weight, with all species showing high phytosterols proportions and balanced omega-6/omega-3 (n-6/n-3) ratios. In addition, Cymopolia barbata, Asparagopsis sp., and Hypnea spinella seem to be an attractive source of both mono- and di-galactosyl-diacylglycerols, while A. stellata, Jania sp., and Lobophora sp. are relatively rich in n-3 LC−PUFA. Finally, both green algae showed the most favorable values for the nutritional indicators of cardiovascular health promotion. Overall, the macroalgal species analyzed could be considered as interesting sources for human and animal nutrition.

Charophytic Green Algae Encode Ancestral Polymerase IV/Polymerase V Subunits and a CLSY/DRD1 Homolog.

In flowering plants, euchromatic transposons are transcriptionally silenced by RNA-directed DNA Methylation, a small RNA-guided de novo methylation pathway. RNA-directed DNA Methylation requires the activity of the RNA Polymerases IV and V, which produce small RNA precursors and noncoding targets of small RNAs, respectively. These polymerases are distinguished from Polymerase II by multiple plant-specific paralogous subunits. Most RNA-directed DNA Methylation components are present in all land plants, and some have been found in the charophytic green algae, a paraphyletic group that is sister to land plants. However, the evolutionary origin of key RNA-directed DNA Methylation components, including the two largest subunits of Polymerase IV and Polymerase V, remains unclear. Here, we show that multiple lineages of charophytic green algae encode a single-copy precursor of the largest subunits of Polymerase IV and Polymerase V, resolving the two presumed duplications in this gene family. We further demonstrate the presence of a Polymerase V-like C-terminal domain, suggesting that the earliest form of RNA-directed DNA Methylation utilized a single Polymerase V-like polymerase. Finally, we reveal that charophytic green algae encode a single CLSY/DRD1-type chromatin remodeling protein, further supporting the presence of a single specialized polymerase in charophytic green algae.

Molecular organic geochemistry and origin of oil in the Potwar Basin, Pakistan

The Potwar Basin (PTB) is a prominent geological feature located in northern part of Pakistan, and is considered as one of the active and productive regions for petroleum and gas exploration in Pakistan. In this study, eight crude oil specimens originating from three distinct fields within the PTB were comprehensively examined to decipher the environmental conditions, source of organic matter (OM) and oil-oil correlations using gas chromatography coupled with flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC–MS). The molecular marker and hierarchical cluster analysis of PTB oils reveal two different crude oil families. Family-I showed relatively low values of Pr/Ph, C19TT/C23TT and C25TT/C24TeT, C27-C29 regular steranes, dibenzothiophene (DBT), fluorene (FL) and dibenzofuran (DBF), as well as C26/C28 TAS (20S) and C27/C28 TAS (20R). These results suggest that Family-I crude oils derived from marine environment of suboxic water bodies with higher contribution from green algae or planktonic microbes. However, Family II contains comparatively high values of the aforementioned molecular parameters, indicating that crude oils mainly originated from a lacustrine environment with a higher contribution of plant organisms under oxidizing conditions. Saturated hydrocarbon maturity parameters such as CPI and OEP, and C3122S/(C3122S + C3122R) and C3222S/(C3222S + C3222R) indicate PTB crude oils are thermally mature, while aromatic indices reveal that Family-II crude oils are high mature. The present research defines that PTB crude oils contributed from mixed organic matter sources of marine and lacustrine majorly from marine sedimentary environment with the bloom of algae and/or higher plants.

Reconstructing the palaeoecology of a middle Permian alkaline lake using molecular fossils, case study of the Lucaogou Formation in the Junggar Basin, NW China

The lacustrine Lucaogou Formation was deposited during the middle Permian in the Junggar Basin, northwestern China. The depositional environment was an alkaline, brackish to saline lake. The biological diversity of the Lucaogou Formation was reconstructed using biologically informative molecules such as n-alkanes, steranes, and hopanes, and the δ13C composition of organic matter. C30 4α-methyl-24-ethylsterane, C31 lanostane, and abundant C30 − C31 3β-methylhopanes were detected in the organic matter, suggesting the presence of type Ⅰ aerobic methanotrophs including the Methylococcaceae. C30 − C31 2α-methylhopanes and 7- and 8-methylheptadecanes are suggestive of the presence of cyanobacteria. Cyanobacteria and green algae are proposed to have made the dominant contribution to the organic matter. The presence of more 13C-enriched hopanoids in the lower unit compared to the upper unit of the Lucaogou Formation suggest a greater contribution of cyanobacteria to the organic matter in the lower unit. The high abundances of C28 and C29 steranes relative to C27 steranes are likely due to green algae from the Chlorophyta, including the class Chlorophyceae. Dinosteranes that are diagnostic for dinoflagellates were not detected. The low concentrations of C40 isorenieratane, renieratane, β-isorenieratane, renierapurpurane, and β-renierapurpurane that are indicative of photosynthetic green and purple sulfur bacteria indicate a minor contribution from Chlorobiaceae and Chromatiaceae to the organic matter. It is inferred that low to moderate amounts of ciliates grew at or below the relatively unstable chemocline in the lake. The presence of C19-norisopimarane, 8β(H)-labdane, and 4β(H)-19-norisopimarane suggests the presence of coniferous plants growing around the lake, probably including Pinaceae, Araucariaceae, Cupressaceae.