Primary Production Of Organic Matter Research Articles

Wide ecological niches ensure frequent harmful dinoflagellate blooms

Harmful algal blooms (HABs) and their consequences cause multiple devastating effects in various freshwater, brackish and marine ecosystems. However, HAB species at moderate population densities have positive ecological roles as primary producers of organic matter and food for zooplankton and fish. They also enhance benthic-pelagic coupling and participate in the biogeochemical cycles. The consequences of HABs are transported across the conventional environmental boundaries by numerous cascade effects in the food webs and beyond. Meanwhile, forecasts of bloom events are still limited, largely because of scarcity of reliable information on ecological niches of the bloom-forming algae. To fill up this knowledge gap, this study focused on dinoflagellates, a diverse group of mostly photosynthesizing protists (unicellular eukaryotes) capable of mixotrophy, since they play a key role in primary production and formation of blooms in marine and brackish waters worldwide. In this study, ecological niches of 17 abundant bloom-forming dinoflagellate species from coastal regions of the southern Baltic Sea were identified for the first time. It was hypothesized that wider ecological niches ensure more frequent dinoflagellate blooms compared to the species with narrower niches. This hypothesis was verified using the long-term (44 years) database on phytoplankton abundance and physical-chemical characteristics of the environment. It were analyzed 4534 datasets collected from 1972 to 2016. Fourteen abiotic parameters (water temperature, salinity, Secchi depth, pH, Chl a, and concentration of basic nutrients) were considered as ecological niche dimensions. The Principal Component Analysis presented the dissolved inorganic nitrogen, total nitrogen, Chl a, and temperature as principal niche dimensions of dinoflagellates. The algal bloom criteria were refined. It was for the first time proved statistically that HAB frequency of dinoflagellate species robustly correlated with the width of their ecological niches.

Multi-method characterization of the recent sediment from the Dibi subsidence lake in the tropical Adamawa region (central Cameroon): Implications for the palaeoenvironmental reconstruction

The evolution and functioning of various tropical ecosystems is poorly understood due to a lack of quantitative techniques to characterize the physicochemical composition of soils and sediment. Here, a detailed multi-method study of lithological changes is provided from a core taken from the silted-up Dibi subsidence lake (central Cameroon). To unravel the provenance of sediment, mineral constituents, and organic matter sources, an array of tools are applied including a spectrophotometer, a laser particle sizer, Rock-Eval pyrolysis, X-ray diffractometer (XRD), a portable X-ray fluorescence (XRF) spectrometry, and an inductively coupled plasma-atomic emission spectroscopy (ICP-AES) instruments. The studied core consists of light-colored deposits at the base (Unit 1) overlain by dark humic deposits (Unit 2). The sediment is very well graded (grading index Sd < 0.35Ф), indicative of bottom suspended to rolling transport. Unit 1 is characterized by relatively low values of total organic carbon (TOC: 2%–5%) whereas the dark Unit 2 has high contents of TOC (10%–33%). The core shows a high oxygen index (OI) value (average = 207 mg carbon dioxide (CO2)/g TOC) and a low hydrogen index (HI) value (average = 107 mg hydrocarbon (HC)/g TOC). This indicates highly altered organic matter (OM), likely from decomposed terrestrial plants. The chlorophyll-α fingerprint (peak around 675 nm) also reveals an autochtonous primary production of organic matter. The mineralogical assemblage of Unit 2 comprises kaolinite, quartz, feldspars, montmorillonite, ilmenite, siderite, gibbsite, rutile, and anatase whereas that of Unit 1 is similar but differs with the presence of illite and the absence of gibbsite. The high titanium dioxide (TiO2) and zirconium (Zr) contents confirm that the source rocks also are comprised of granites, and gneiss without volcanic rocks, such as basalts and trachytes. The source rocks have been intensively weathered using some parameters such as ln(Al2O3/Na2O), K2O/Rb, K/Al, and weathering indices, where Al2O3 denotes aluminum oxide, Na2O denotes sodium oxide, K2O denotes potassium oxide, Rb denotes rubidium, K denotes potassium, and Al denotes aluminum. The enrichment factors (EF) of redox-sensitive trace elements and their relation with TOC, the negative values of manganese/iron ratio (Mn∗) associated to three elemental ratios (cupper/zinc (Cu/Zn), thorium/uranium (Th/U), and vanadium/chromium (V/Cr)) attest to the predominance of sub-oxic to anoxic bottom waters in Dibi lake during sediment deposition. The data also show low primary productivity at the base of the core, followed by an increase towards the top, linked to the intensification of weathering and facilitated by humid climatic conditions, usually increase terrestrial input and palaeoproductivity. The petrological data show a generally warm and humid palaeoclimate. This climatic variation has contributed to the large spread of the savannah and disappearance of the forest. This study sheds light on the late Pleistocene to Holocene palaeoenvironment evolution of the Adamawa region which could be integrated into the context of the Pleistocene to Present regional evolution of the tropical palaeoenvironment.

Organic matter enrichment mechanism in saline lacustrine basins: A review

Organic‐rich shale in saline lacustrine basins holds significant importance as a source rock for conventional hydrocarbon exploration and has emerged as a prominent target for unconventional hydrocarbon exploration and development in recent years. Based on saline lacustrine basins, this paper provides a summary of the organic matter enrichment mechanisms in saline lacustrine basins, considering sedimentary characteristics, biological activities, factors for the organic matter enrichment and consumption, and hydrocarbon generation. The implications for these factors are discussed in relation to the distribution prediction of high‐quality lacustrine shale district settings and the exploration and development of shale oil. Saline lacustrine basins undergo distinct evolutionary stages, each corresponding to different sedimentary stages involving carbonate minerals, sulphate minerals, and alkaline minerals. Moreover, these basins exhibit diverse biological types and experience extensive biological activities. The prosperity of organisms and the accumulation of sedimentary organic matter are ensured by halophilic organisms. Organic matter enrichment in saline lacustrine basins is influenced by two main aspects: the primary productivity of organic matter, which is promoted by the proliferation of halophilic organisms, and the efficient preservation of organic matter facilitated by the strong reducing environment resulting from promoted water salinity stratification. The organic matter consumption in saline lacustrine basins involves bacterial sulphate reduction (BSR) in the early stages, thermochemical sulphate reduction (TSR) in the late stages, and dilution of salt minerals with higher depositional rates. of the presence of salt beds and saline minerals positively influences hydrocarbon generation and expulsion in organic‐rich shale within saline lacustrine deposition. Consequently, continental saline lacustrine basins in China offer favourable conditions for the formation of organic‐rich shale and present broad prospects for the exploration of shale oil and gas resources.

ВЛИЯНИЕ СОЛЕНОСТИ ВОДЫ НА РАЗВИТИЕ ПРИДОННОЙ ГИПОКСИИ И УРОВЕНЬ ПЕРВИЧНОГО ПРОДУЦИРОВАНИЯ ОРГАНИЧЕСКОГО ВЕЩЕСТВА В ТАГАНРОГСКОМ ЗАЛИВЕ

At present, the Azov Sea ecosystem exists in the context of continuously decreasing continental runoff and increasing water salinity, which reached in 2020-2021 the highest values for the entire period of observations since 1962. The increase in water salinity inevitably leads to the transformation in the composition of biological communities, which has a pronounced effect on the environment and fisheries. This paper discusses the long-term impact of water salinity on the development of near-bottom hypoxic phenomena and on the volume of primary production of organic matter by phytoplankton in the Taganrog Bay during the summer season (1962-2021). A statistical ecosystem analysis describing the contribution of the major hydrological and hydrochemical factors into the processes of hypoxia formation in the bottom water layer of the Taganrog Bay has been performed. It is shown that the desalinization of the waters of the Taganrog Bay in 1993-2008 was accompanied by the increase in the size of hypoxic zones in the bottom water layer. During the modern period of salinization extending from 2009 to the present, there has been recorded a decrease in the scale of oxygen deficiency in the Taganrog Bay. The most crucial contribution to the hypoxic processes in the Taganrog Bay is provided by the stability of water masses, water temperature, organic nitrogen concentration, and the water salinity (due to the effect of salinity on the stability of water masses). During the streaks of the Taganrog Bay salinization, the decrease in the stability of water masses and in the content of organic nitrogen and phosphorus in the water (crucial factors in the formation of hypoxic zones) has been recorded. The highest rates of the primary production of organic matter by phytoplankton in the Taganrog Bay were observed during the desalinization period of 1962-1968, and the lowest ones were recorded during the salinization periods. The results of this assessment have exposed the significant relationship: the primary production of organic matter depends on the average annual runoff of the Don River, the water salinity, and the concentration of mineral nitrogen.

The comprehensive effect of copper oxide nanoparticles on the physiology of the diatom microalga Thalassiosira weissflogii.

The high rate of production and use of copper oxide nanoparticles (CuO NPs) results in its accumulation in the environment. However, the effect of large quantities of CuO NPs on aquatic ecosystems is not fully known. In aquatic ecosystems, phytoplankton is the primary producer of organic matter and the basis of all the trophic interactions; accordingly, the potential effect of CuO NPs on the microalgae community is of great concern. This study established the main patterns of changes in morphological, structural, functional, fluorescent and cytometric parameters in the marine diatom Thalassiosira weissflogii after adding CuO NPs to the medium at concentrations of 250-2500μgL-1. As shown, the investigated pollutant has cytotoxic, genotoxic and mechanical effect on the microalga covering almost all the aspects of cell functioning. A two-fold decrease in the culture abundance relative to the control is observed at the toxicant content of 550μgL-1 in the medium. At CuO NPs content above 750μgL-1, a pronounced inhibition of the alga growth is recorded, as well as a decrease in the efficiency of its photosynthetic apparatus, a disturbance of membrane integrity, an increase in cell volume, a rise in abundance of dead/inactive cells in the culture, enlargement and deformation of nuclei, an increase in reactive oxygen species production, and depolarisation of the mitochondrial membrane. Our results show that high CuO NPs concentrations in water can cause serious disruptions in phytoplankton functioning and in equilibrium of aquatic ecosystems in general.

The effects of secondary bacterial metabolites on photosynthesis in microalgae cells.

Secondary metabolites of bacteria are regulatory molecules that act as "info-chemicals" that control some metabolic processes in the cells of microorganisms. These molecules provide the function of bacteria communication in microbial communities. As primary producers of organic matter in the biosphere, microalgae play a central ecological role in various ecosystems. Photosynthesis is a central process in microalgae cells, and it is exposed to various biotic and abiotic factors. Various secondary metabolites of bacteria confer a noticeable regulatory effect on photosynthesis in microalgae cells. The main purpose of this review is to highlight recent experimental results that demonstrate the impact of several types of common bacterial metabolites (volatile organic compounds, non-protein amino acids, and peptides) on photosynthetic activity in cells of microalgae. The use of these molecules as herbicides can be of great importance both for practical applications and for basic research.

Identification of sulfur–oxidizing Thiothrix bacteria on microcrustaceans from the sulfidic groundwaters of Mangalia (southeastern Romania)

Movile Cave, located in southeastern Romania close to the Black Sea, is one of the most remarkable diversity hotspots worldwid with 52 species of invertebrates of which 37 are endemic (Brad et al. 2021). Due to the high concentration of hydrogen sulfide in its water, the primary production of organic matter in Movile Cave relies almost entirely on the chemoautotrophic activity of microorganisms, notably sulfur-oxidizing gammaproteobacteria belonging to the genus Thiothrix. In the presence of oxygen, these filamentous bacteria can oxidize hydrogen sulfide and reduce it into various sulfidic compounds, generating energy in the process. In sulfidic ecosystems, Thiothrix bacteria are frequently found free-living but also as epibionts or ectosymbionts growing on other organisms, such as amphipods (Flot et al. 2014). However, it is unclear whether Thiothrix bacteria also grow on microcrustaceans such as copepods or ostracods, of which several species are known from the sulfidic mesothermal aquifer of Mangalia, where Movile Cave is located. To find it out, we combined DNA sequencing using the reference bacterial 16S ribosomal RNA gene with morphological observations (including fluorescence microscopy). Our results reveal that Thiothrix bacteria are indeed present on microcrustaceans from Movile Cave and surrounding wells in the Mangalia region, highlighting the versatility of Thiothrix-crustacean associations in sulfidic ecosystems. This is the first report of an association between Thiothrix and groundwater microcrustaceans, and the second report of an association between Thiothrix and a nonmarine ostracod (Khalzov et al. 2021).

Technogenesis and Ecological State of Natural Waters in Eastern Transbaikalia

The research on the state of water ecosystems is significant in terms of future biological impacts of natural and anthropogenic effects. The key branches of natural resources management in Eastern Transbaikalia (agriculture, hydraulic power industry) are based on using water resources. The findings show that technogenesis affects surface waters of the region. Alluvial gold mining represents a significant part of mining industry. Gold mining in river channels results in run-of-stream diversion and interferes with the ecosystem of watercourses. A newly formed structure of a water ecosystem is not favourable for self-purification capacity of rivers. This leads to pollutants accumulation in water objects and deteriorates ecological state of watercourses. Natural components in the technoecosystem of hydropower objects in Eastern Transbaikalia are Lake Kenon and the Kharanor Reservoir. Although the catchment area is polluted by TPP-1, the ecosystem of the lake is still capable of self-purification due to biodiversity of hydrobionts. Under the dry climate in recent years, the Kharanor Reservoir ecosystem turned as rather unstable due to constant refilling from the Onon River. However, generally, pigment indices show physiological activity of primary producers of organic matter.

Metatranscriptomic outlook on green and brown food webs in acid mine drainage.

Acid mine drainages (AMDs), metal-rich acidic effluents generated by mining activities, are colonized by prokaryotic and eukaryotic microorganisms widely distributed among different phyla. We compared metatranscriptomic data from two sampling stations in the Carnoulès AMD and from a third station in the nearby Amous River, focussing on processes involved in primary production and litter decomposition. A synergistic relationship between the green and brown food webs was favoured in the AMD sediments by the low carbon content and the availability of mineral nutrients: primary production of organic matter would benefit C-limited decomposers whose activity of organic matter mineralization would in turn profit primary producers. This balance could be locally disturbed by heterogeneous factors such as an input of plant debris from the riparian vegetation, strongly boosting the growth of Tremellales which would then outcompete primary producers. In the unpolluted Amous River on the contrary, the competition for limited mineral nutrients was dominated by the green food web, fish and bacterivorous protists having a positive effect on phytoplankton. These results suggest that in addition to direct effects of low pH and metal contamination, trophic conditions like carbon or mineral nutrient limitations also have a strong impact on assembly and activities of AMDs' microbial communities.

Geochemical, petrographic and reservoir characteristics of the transgressive systems tract of lower Silurian black shale in Jiaoshiba area, southwest China

In recent years, lithofacies identification and classification have been a hot topic in shale gas research. Even if some previous works are considering the distribution characteristics of lithofacies in different system tracts (third-order sequences), only few studies systematically reveal the lithofacies distribution and reservoir characteristics. In this study, we focus on transgressive systems tract (TST) section which is characterized by high TOC content and highest gas content in the Long-1 member and divided the third-order TST into five Units (parasequences) according to graptolite biozonation, gamma ray (GR) and acoustic (AC) logging data. Twenty-six samples were analyzed for total organic carbon (TOC) content, mineral and elemental composition, porosity, pore type, pore size distribution and pore connectivity. The results show that Unit 1 is predominantly composed of S-3 and S-4 lithofacies, and Units 2–5 is predominantly composed of S-4 and M-2 lithofacies. The S-4 lithofacies was associated with high primary productivity of organic matter, and anoxic bottom water conditions. Redox conditions changed from anoxic to dysoxic condition and the productivity decreased through Unit 1 to Unit 5. Compared to other units, Units 1 and 2 are characterized by higher porosity and better pore connectivity. The S-3/S-4 and M-2 lithofacies exhibit different reservoir quality, especially in pore structure. Mineralogical composition is the key factor to determine lithofacies type and affects the characteristics of pore structure. Besides, TOC plays an important role in the development of organic matter pores. Anoxic bottom water conditions and high paleo-salinity contributed to the preservation of organic matter.

ASSESSMENT METHODOLOGY OF GREEN PLANTATIONS VITALITY IN THE CONDITIONS OF TECHNOGENIC-TRANSFORMED ECOSYSTEMS

The most informative parameters of woody plants living condition are analyzed, which should be used for ecological monitoring of urbanized and oil-contaminated areas. The reactions of the plant organism at different levels of the biosystem organization in response to the action of priority pollutants of the technogenic-transformed environment - heavy metals and oil products - are given. The relevance of the study of oil pollution as one of the main environmental problems of today is substantiated. Adaptive-protective reactions characteristic of resistant plant species and destructive changes in stress-sensitive phytoobjects are highlighted. It is established that the widest range of plant reactions to man-made environmental influences can be found at the molecular, cellular and organ levels of biosystems organization. Based on a set of morphological, physiological, cytological, histological and phenological processes of plants, it is recommended to use indicator species in biomonitoring studies, and remediative species - in reclamation measures of anthropogenically altered areas. Methodical approaches to the assessment of the ecological condition of urbanized and oil-contaminated ecosystems, based on the specifics of zoning and the choice of background area, are highlighted. The classes of vitality and the categories of plant stability are characterized on the basis of the percentage deviation of the analyzed plant parameters with the background values. The prospects of green plantations as primary producers of organic matter and recipients of complex influence of biotic, abiotic and anthropogenic environmental factors are substantiated. The criteria for sampling plant material for bioindication studies in order to obtain reliable factual data are described. The relationship between the processes that occur at all levels of the biosystem hierarchy of the plant organism - from molecular to ecosystem – is highlighted. Based on the establishment of the living condition of green areas of urbanized and oil-contaminated areas, it is possible to timely record the slightest changes in the ecological state of the environment and prevent further negative trends in it.

Description of biological wastewater treatment plants of city of Odesa as sources of marine environment nutrient pollution in current period

Biological wastewater treatment plants (the BTPs) of city of Odesa (Northern and Southern Plants) are the most powerful permanent sources of nutrient pollution of coastal waters of Odesa Region of the north-western part of the Black Sea (the NWPBS) and the Khadzhybei Liman. The article includes a comparative analysis of changes, taking place since the beginning of the 21st century, related to the qualitative composition of return water of the Northern and Southern BTPs and the amount of nutrients reaching the marine environment together with such water, as well as the analysis of possible influence of such changes on eutrophication of coastal waters of Odesa Region of the NWPBS and the Khadzhybei Liman. It was established that despite significant decrease (by 1.7 - 2 times) of return water discharged from the BTPs the amount of nitrates and nitrites reaching the marine environment together with such water increased by 4-6 times. At the same time the reduced inflow of organic matter, ammonium nitrogen and phosphates can be observed.&#x0D; Treatment facilities of Odesa were put into operation back in the 1970s. They use a then typical technology of biological cleaning of wastewater from nutrient compounds in aeration tanks providing aerobic conditions. The technology is considered as incomplete in terms of nitrogen compounds treatment since its final product includes nitrate nitrogen in large quantities. When reaching the marine environment it is absorbed by algae at the stage of primary production of organic matter and thus is transformed in organic nitrogen again. It was noted that since the coastal waters of Odesa Region of the NWPBS and the Khadzhybei Lyman have a high level of trophicity and currently there is a disbalance between mineral nitrogen and phosphorus concentrations in the water towards insufficiency of mineral nitrogen reserves (as compared with the standard Redfield stoichiometric ratio), additional inflow of nitrates and nitrites in the marine environment together with return water from the BTPs would, in certain circumstances, lead to algal bloom and aggravation of negative eutrophication-related consequences.&#x0D; The research allowed making a conclusion that a modern flow sheet of advanced biological cleaning (treatment) of wastewater from nitrogen compounds should be implemented at the Northern and Southern BTPs in order to reduce the inflow of nitrates in the marine environment. Such flow sheet should ensure both nitrification and denitrification processes.

СОВРЕМЕННЫЕ ПРОБЛЕМЫ ИССЛЕДОВАНИЯ ЦИКЛА УГЛЕРОДА В АЗОВСКОМ МОРЕ

A review of the carbon cycle studies in the coastal waters of the World Ocean was carried out. The authors of the literature reviews emphasize the importance of regional studies to refine estimates of the contribution of coastal waters to the global carbon balance, as well as their response to global climate change. In addition, understanding the carbon cycle in coastal waters is necessary to address a range of environmental, social and economic issues. This work presents the results of the synthesis of scientific knowledge about different elements of the carbon cycle in the Sea of Azov: primary production of organic matter (OM), OM and calcium carbonate content in water and bottom sediments of the sea, lateral sources of organic carbon and carbonates. The highly productive Sea of Azov was mainly considered earlier in terms of its fish resources. Current understanding of the balance of organic carbon, the saturation of the waters of the Sea of Azov with free carbonic acid, and the exchange of CO2 with the atmosphere are based on estimates made in the middle of the 20th century, while changes in the ecosystem of the Sea of Azov associated with climate fluctuations and anthropogenic stress have been well documented since the mid-1980s. The following questions become relevant. Does the Sea of Azov continue to be a source of CO2 into the atmosphere? If so, why is this happening and what are the main factors; how this process is distributed in time and space; what should be expected in the future? If this is not the case, then it is important to understand what and why influenced it the most? A number of scientific hypotheses are formulated that require further development.

Fatty Acids of Marine Mollusks: Impact of Diet, Bacterial Symbiosis and Biosynthetic Potential.

The n-3 and n-6 polyunsaturated fatty acid (PUFA) families are essential for important physiological processes. Their major source are marine ecosystems. The fatty acids (FAs) from phytoplankton, which are the primary producer of organic matter and PUFAs, are transferred into consumers via food webs. Mollusk FAs have attracted the attention of researchers that has been driven by their critical roles in aquatic ecology and their importance as sources of essential PUFAs. The main objective of this review is to focus on the most important factors and causes determining the biodiversity of the mollusk FAs, with an emphasis on the key relationship of these FAs with the food spectrum and trophic preference. The marker FAs of trophic sources are also of particular interest. The discovery of new symbioses involving invertebrates and bacteria, which are responsible for nutrition of the host, deserves special attention. The present paper also highlights recent research into the molecular and biochemical mechanisms of PUFA biosynthesis in marine mollusks. The biosynthetic capacities of marine mollusks require a well-grounded evaluation.

Определение скорости роста и элиминации отдельных видов и популяций в сообществе фитопланктона бухты Севастопольская (Чёрное море)

Актуальность исследования определяется ключевой ролью фитопланктона в функционировании морских экосистем: одноклеточные водоросли образуют начальное трофическое звено в пищевой цепи, осуществляя первичную продукцию органического вещества в процессе фотосинтеза. Важными задачами являются определение значения скорости чистого (видимого) роста фитопланктона в целом и составляющих его элементов, включая популяции отдельных видов, и изучение возможности оценивать скорость их действительного роста и выедания на основе регулярных короткопериодных определений численности и биомассы фитопланктона в природных сообществах. Для решения данной задачи использованы как полученные ранее материалы подекадного мониторинга состояния фитопланктона в прибрежной зоне, так и результаты недавно проведённых экспериментов. Выполненные в течение 2007 г. подекадные определения в зоне устья б. Севастопольская включали измерения численности и биомассы фитопланктона, а также концентрации хлорофилла a с периодичностью в несколько суток, что позволило рассчитывать скорость чистого удельного роста биомассы (видимый рост, k) согласно её изменениям, фиксированным за этот период. Путём сопоставления численности отдельных видов в ближайших по времени определениях рассчитаны 29 значений скорости видимого роста для 9 массовых видов. Видимый рост, являясь разницей между действительным ростом и выеданием, может быть использован для определения этих величин. Закономерности, которые связывают значения скорости видимого и действительного роста клеток водорослей с их размерами, выявлены в экспериментах, проведённых по методу разбавления, изначально предназначенному для исследования суммарного фитопланктона, но адаптированному нами для определения функциональных параметров отдельных видов, что и позволило выявить связующие их закономерности. Используя найденные закономерности, мы получили 22 значения скорости роста µ и скорости выедания m для 7 массовых видов фитопланктона в зоне устья б. Севастопольская. Показано, что скорость роста отдельных видов фитопланктона, объём клеток которых составляет до 1000 мкм³, может достигать значений свыше 1 сут−1. Для водорослей, объём клеток которых превышает 1500 мкм³, значения µ приближаются к значениям k, а значения m ― к нулю. Для этой группы скорость действительного роста µ принимается равной скорости видимого роста k, а скорость выедания m ― равной нулю. В действительности в естественной популяции мелкие виды преимущественно выедаются в верхнем освещённом слое; крупные виды оседают на дно или в глубинные горизонты. Полученные нами сравнительно высокие значения k свидетельствуют, возможно, о низких значениях элиминации, в том числе о низкой выедаемости. По результатам эксперимента, при увеличении объёма клеток водорослей до 1600 мкм³ значения k возрастают до уровня значений µ, в то время как значения m падают до нуля. Это означает, что выеданию подвержены прежде всего популяции фитопланктона с мелкими клетками; виды с более крупными клетками не выедаются. Между тем с таким заключением не согласуются показатели скоростей видимого роста, измеренных in situ, которые включают как положительные, так и отрицательные значения для всех популяций независимо от размера клеток. Это противоречие объясняется тем, что в эксперименте отмирающие и оседающие на дно сосуда крупные клетки учитывают наравне с живыми, что скрывает эффект элиминации.

Form III RubisCO-mediated transaldolase variant of the Calvin cycle in a chemolithoautotrophic bacterium

The Calvin-Benson-Bassham (CBB) cycle assimilates CO2 for the primary production of organic matter in all plants and algae, as well as in some autotrophic bacteria. The key enzyme of the CBB cycle, ribulose-bisphosphate carboxylase/oxygenase (RubisCO), is a main determinant of de novo organic matter production on Earth. Of the three carboxylating forms of RubisCO, forms I and II participate in autotrophy, and form III so far has been associated only with nucleotide and nucleoside metabolism. Here, we report that form III RubisCO functions in the CBB cycle in the thermophilic chemolithoautotrophic bacterium Thermodesulfobium acidiphilum, a phylum-level lineage representative. We further show that autotrophic CO2 fixation in T. acidiphilum is accomplished via the transaldolase variant of the CBB cycle, which has not been previously demonstrated experimentally and has been considered unlikely to occur. Thus, this work reveals a distinct form of the key pathway of CO2 fixation.

How marine incursion influences the quality of lacustrine source rocks: The Paleogene Nanxiang Basin, eastern China

The impact of marine incursions during transgression (i.e., sea level rises and the shoreline moves landward) on the formation and quality of lacustrine source rocks is an important and contentious issue. In this study, we present a case study of the Paleogene Hetaoyuan Formation in the Biyang sag, Nanxiang Basin, eastern China. Paleontological, trace-element, and biomarker data indicate that the Hetaoyuan source rocks in this region were influenced by a marine incursion. The paleontological evidence indicates that the marine incursion resulted in the introduction of red and brown algae, which commonly inhabit marine environments. Trace-element analyses yielded representative evidence of marine incursion (e.g., equivalent boron content >300 ppm and B/Ga ratio >4.2). Biomarker evidence for marine incursion includes C26/C25 tricyclic terpanes ratios of 1:3, which is the threshold for distinguishing marine organic matter from lacustrine. Using the B/Ga ratio as a typical paleosalinity indicator, it was determined that the influence of marine incursion decreased from the Biye 1 to Cheng 2 to An 3006 wells, with the B/Ga ratio average decreasing from 7.51 to 6.81 to 3.73, respectively. With an increasing extent of marine incursion (e.g., distance landward, overall water depth, and marine–freshwater mixing), the primary productivity of organic matter increased, and the preservational environment became more reducing. These changes resulted in higher contents of organic matter (total organic carbon e 2–8 wt. %) and a more favorable type of organic matter for oil generation (kerogen type I–II), indicating that the marine incursion had a positive effect on the formation of source rocks. Therefore, the formation mechanism of high-quality source rocks in coastal lacustrine basins during high sea-level periods and associated resource potential might need to be reevaluated (e.g., the Campanian lower Neslen Formation along the margins of the Western Interior Seaway of North America and the terminal Oligocene–early Miocene in the fluvial Saldanha Bay at the southwestern tip of Africa). The results also provide useful data for regional oil and gas exploration.

Correction for the siderite effect on Rock-Eval parameters: Application to the sediments of Lake Barombi (southwest Cameroon)

Originally developed for use in the petroleum industry, Rock-Eval pyrolysis is a technique commonly applied to lake sediments to infer paleoenvironmental reconstructions. The standard Rock-Eval parameters provide information on the amount of total organic and inorganic carbon (TOC and MinC, respectively), and are usually interpreted as proxies for the source (aquatic or terrestrial) of the primary production of organic matter (Hydrogen Index vs Oxygen Index). Although this method usually provides valuable evidence, the common presence of siderite in tropical lake sediments can alter the primary signal of the sedimentary organic matter (SOM). Indeed, the CO2 and CO released by the pyrolysis of siderite are integral to the calculation of the SOM-related standard Rock-Eval parameters. In this study, we analyze sediments from a core collected in the Lake Barombi (southwest Cameroon) and describe the impact of siderite on standard Rock-Eval parameters. We propose a workflow that allows standard Rock-Eval parameters to be corrected, based on the analysis of thermograms. The proposed corrections provide siderite-effect-free parameters, accurately reflecting the changes in sedimentary organic matter composition.

The Influence of Phytoplankton Primary Production on the Cycle of Biogenic Elements in the Coastal Waters off Sevastopol, Black Sea

The phytoplankton primary production and the biogenic elements content of the coastal waters off Sevastopol have been studied as a result of 2-year monitoring. It has been found that mineral phosphorus is a key factor of chemical limitation of the production processes. During primary production of organic matter, the habitat conditions for phytoplankton in the photic layer are in accordance with the Le Chatelier–Braun principle of negative feedback.

Hydrocarbon Potential of Paleo- and Modern Suprasubduction Provinces: Tectonic, Geodynamic, Mineralogical-Geochemical, and Biochemical Aspects

The paper is devoted to the integrated analysis of the interdisciplinary problem of the genesis of hydrocarbon potential in suprasubduction provinces. A geodynamic model is proposed for the formation of petroleum pools on the shelves of the Meso-Cenozoic back-arc basins in the western Pacific Ocean. Original data on the tectonics and composition of the mantle peridotites of the Polar Ural ophiolite complexes are given for comparison. These data are used to consider the low-temperature lizardite–chrysotile and high-temperature antigorite types of peridotite serpentinization in the back-arc basins and in the mantle wedges above the subduction zones of the paleozoic Paleouralian ocean. It is established that these processes are responsible for the abiogenic synthesis of hydrogen and methane. Of great theoretical and applied importance are the conclusions concerning the high antiquity of serpentinization as a hydrogen source, the possible relationships of the origin of life and its early evolution with hydrogen emission in the benthal, the predominance of chemoautotrophic prokaryotes with hydrogen exchange among the primary producers of organic matter in anaerobic conditions, and the high probability of naphthidogenesis based on the prokaryotic communities in the Archean and Proterozoic. The origin of hydrocarbons in the framework of the considered model is regarded from a viewpoint of a polygenetic paradigm of oil and gas generation.