Primary Production Processes Research Articles

Microbial and mineralogical characterization of the alkaline Chae Son hot spring, Northern Thailand.

Early characterizations by morphological identification through light microscopy only revealed the presence of a few microbial lineages and the majority of microbial community at the Chae Son hot spring remains uncharacterized. Therefore, this study aims to examine thermophilic microbial communities at the Chae Son hot spring using next-generation sequencing, including investigating hot spring mineralogy. Results suggest that the Chae Son hot spring (49-75°C, pH = 6.5-7.0) precipitates digitate structures which comprise mainly silica, and that microbial permineralization is primarily through silicification. Alternating layers of mineralized microbial biofilms and silica were observed in digitate sinter cross-sections, contributing to the build-up of microstromatolites. Molecular results revealed that phylogenetically distinct members of photoautotrophic taxa, Chloroflexota and Cyanobacteriota, dominated spring microbial communities (63.19% relative abundance). Potential primary production processes were mainly through photoautotrophy, with minor lithoautotrophic activities (e.g., sulfur cycling and nitrogen cycling). Moreover, overall microbial community and Cyanobacteriota population alpha diversities significantly decreased with increased temperatures. However, no significant correlation was identified between Chloroflexota population diversity and temperatures. This study provides an update on the microbial community using a high-throughput next-generation sequencing technology, including the mineralogy of the Chae Son hot spring, Northern Thailand.

Larger, Not Leaner? Agencification and the Size of the Administrative Overhead in Local Governments

ABSTRACTGovernments establish agencies to enhance public service efficiency, aiming to improve government performance. However, agencification makes governments' service delivery more complex by putting service providers at arm's length from governments' control. To retain their capacity to support frontline service delivery, governments may expand their central administrative overhead. Conceptually, overhead constitutes resources available to support primary production processes in the organization, such as managerial coordination and technical support. This study, based on survey and registry data from 296 Norwegian local governments, analyses whether agencification correlates with the size of administrative overhead across political systems. The findings reveal lower central administrative overhead in local governments with higher degrees of agencification, suggesting a challenge in providing central support for an increasingly disaggregated service delivery. Importantly, the study underscores the difficulty governments face in mobilizing adequate resources to achieve their stated goals.

Impacts of shellfish and macroalgae mariculture on the seawater carbonate system and air-sea [formula omitted] flux in Haizhou Bay, China

China is the largest mariculture country, and shellfish and algae output ranks first, showing high carbon sink capacity. In recent years, the single cultivation of macroalgae (Pyropia yezoensis) has been changed to macroalgae-shellfish mariculture in Haizhou Bay to increase the yield of P. yezoensis and improve the water environment quality. In this study, four surveys were carried out in July 2022 during the monoculture period of oyster (Magallana gigas), as well as at different stages of P. yezoensis culture (head-crop period, November 2022, peak growing season, January 2023, and end of harvesting, March 2023) in the mariculture and the surrounding waters of Haizhou Bay. The effects of different stages of culture on the seawater environment and seasonal and spatial variations in the carbonate system were analyzed, and the carbon sink capacity was preliminarily estimated. The results showed that in summer, the calcification of M. gigas and the primary production process of phytoplankton effectively reduced the dissolved inorganic carbon (DIC) level in the culture area. The culture area acts as a CO2 sink, with an average air-sea CO2 flux of −4.5 mmol m−2 d−1. During the polyculture period, the P. yezoensis culture activities maintained the stability of the seawater carbonate system, and the culture area shows strong CO2 sinks, with the average air-sea CO2 flux of −24.10 mmol m−2 d−1, -37.68 mmol m−2 d−1, and -38.99 mmol m−2 d−1, respectively. The absorption of CO2 by large-scale cultured P. yezoensis through the "biological pump" effect is the main factor affecting the CO2 exchange process at the air-sea interface, and the absorption rate of CO2 by P. yezoensis at the mature stage is higher than that at the growth stage before harvesting. The study revealed that macroalgae-shellfish mariculture could promote mutual growth, alleviate environmental pressure, and enhance the carbon sink of the culture area. The relationship between mariculture and the carbon cycle of a mariculture ecosystem is very complicated, and its biochemical process should be given great attention for further study.

Dual benefits of biofouling reduction in non-fed aquaculture: On-site heat treatment enhances oyster production and mitigates local environmental impacts

We experimentally evaluated the biofouling reduction by on-site heat treatment in enhancing oyster aquaculture production and mitigating its environmental impacts. Specifically, we compared oyster growth, settling flux of particulate organic matter (POM), and its oxygen consumption rate (OCR) between heat-treated (HT) and non-treated (N) sections within suspension oyster farms in a temperate bay. HT demonstrated a substantial reduction of 81–99% in fouling mussel biomass and approximately 20–30% increases in cultivated oysters’ growth and condition index. The settling flux of POM was 10–57% smaller in HT mainly due to the reduction in biodeposition from fouling mussels. However, OCR of settling POM at a unit mass was 6–62% higher in HT than in N; overall, the short-term oxygen consumption by settling POM did not significantly differ between HT and N. The increase in OCR of settling POM in HT may be attributable to the decrease in biodeposits from fouling organisms and increase in the relative contribution of fresh POM entering from unfarmed areas. Meanwhile, from the longer-term perspective, the substantial reduction in settling POM by the heat treatment lower the potential for oxygen consumption in the bottom layers over the half-year farming operation by 31%. In conclusion, on-site heat treatment is a simple tactic for controlling nutrient and POM flows at production sites, simultaneously enhancing oyster production and mitigating the local environmental impact of non-fed oyster aquaculture. Furthermore, this approach exemplifies an effective tactic to enhance the sustainability of primary food production processes.

Evaluation of fluoride emissions and pollution from an electrolytic aluminum plant located in Yunnan province

The monitoring and evaluation of fluoride pollution are essentially important to make sure that concentrations do not exceed threshold limit, especially for surrounding atmosphere and soil, which are located close to the emission source. This study aimed to describe the atmospheric HF and edaphic fluoride distribution from an electrolytic aluminum plant located in Yunnan province, on which the effects of meteorological conditions, time, and topography were explored. Meanwhile, six types of solid waste genereted from different electrolytic aluminum process nodes were characterized to analyze the fluoride content and formation characteristics. The results showed that fluoride in solid waste mainly existed in the form of Na3AlF6, AlF3, CaF2, and SiF4. Spent electrolytes, carbon residue, and workshop dust are critical contributors to fluoride emissions in the primary aluminum production process, and the fluorine content is 17.14 %, 33.30 %, and 31.34 %, respectively. Unorganized emissions from electrolytic aluminum plants and solid waste generation are the primary sources of fluoride in the environment, among which the edaphic fluoride content increases most at the sampling sites S1 and S7. In addition, the atmospheric HF concentration showed significant correlations with wind speed, varying wildly from March to September, with daily average and hourly maximum HF concentrations of 4.32 μg/m3 and 9.0 μg/m3, respectively. The results of the study are crucial for mitigating fluorine pollution in the electrolytic aluminum industry.

20th century climate warming and human disturbance triggered high aquatic production and strong water-column mixing in maar Lake Xiaolongwan, northeastern China

Lake ecosystems in northeastern (NE) China are sensitive to global environmental change, and are currently under threats of eutrophication and hypolimnetic anoxia. However, the lack of long-term records of lake production and anoxia in this region makes it difficult to discriminate the impacts of recent anthropogenic activity on lake ecosystems from natural ecosystem variability. This study investigates varved sediments from remote maar Lake Xiaolongwan, NE China and reconstructs high-resolution changes in lake primary production, anoxia, nutrient cycling and catchment processes over the past 1500 years using hyperspectral imaging inferred sedimentary total chlorophyll-a and bacteriopheophytin-a (Bphe-a), combined with sedimentary iron and phosphorus fractions data. Results show that, prior to discernible human impacts in this area from ∼600 CE to 1900 CE, lake primary production was higher during warm periods and reduced during cold periods. Bphe-a records show that hypolimnetic anoxia persisted regardless of temperature variability. Cluster analysis suggests that lake algal communities and biogeochemical conditions in the twentieth-century warm period are unprecedented and significantly different from any other time over the past 1500 years. This phenomenon mostly results from global warming and stronger local catchment disturbance in the early 1900s, combined with atmospheric pollution after the 1950s. Human-driven climate warming has caused stronger seasonal mixing (due to shortened ice-cover duration) and overall better oxygenation in the lake. This study demonstrates clear anthropogenic impacts to lake ecosytems in a relatively pristine region in NE China. We anticipate that our findings will have implications for understanding the status of aquatic ecosystems in NE China under future interacting stressors of anthropogenic climate warming and pollution.

Functional biodiversity and agroecological selfregulation for sustainable food

Functional biodiversity is a determining factor in the agroecological transformation towards sustainable food systems. The agroecological design and management of productive, associated and auxiliary biodiversity accumulates agroecological self-regulation capacities from the primary production process to food ingestion

Nutritional Qualities and Valorization Trends of Vegetable and Fruit Byproducts: A Comprehensive Review

Vegetable and fruit byproducts are different parts of vegetables and fruits plus secondary products derived from primary agrofood production processes. With the increasing growth of global vegetable and fruit production, utilization of their byproducts for recovery of health benefit dietary nutrients required emphasis. The current food system and manufacturers are inadequate to maximize the existing food or plant resources’ public demand concurrently to minimize environmental pollution. Important sources of nutritional qualities of these byproducts and their valorization trends are getting research interests. In this review, we have summarized the nutritional qualities and their means of valorization of vegetable and fruit byproducts which have maximum global production from the FAO (2021) published data. The nutritional qualities of the main byproducts are highlighted and the current trends to valorize them into innovative health‐promoting products were assessed. Valorization investigations conducted on these byproducts into food additives (dietary fiber concentrates), nutraceuticals, edible food packaging materials, fermented beverages, and natural dyes were mainly focused on in this review. There are limitations in valorizing technologies of vegetable and fruit byproducts. Hence, further studies are vital to develop novel processing techniques for each of these byproducts. Benefiting from the food waste is a pearl of wisdom and ignoring the value can be participating in pollution.

Взвешенное вещество в Гданьской впадине в кислородных и бескислородных условиях в 2018—2023 годах

The spatial and temporal distribution of suspended matter in the southeastern part of the Baltic Sea was studied in the context of the transition from oxygenated to anoxic conditions. Semi-enclosed water bodies, such as the shallow Baltic Sea, play a key role in the global carbon cycle. Carbon-containing particles, both organic and inorganic, settle within the total suspended matter, making it important to understand the patterns of its distribution. The main sources of suspended matter in the southeastern part of the Baltic Sea are primary production and abrasion processes in the coastal zone. From the intensively mixed coastal zone, the suspended matter is transported to the Gdańsk Deep, where benthic nepheloid layers indicate complex sedimentation conditions, suggesting that this area cannot be considered a simple carbon sink. Intermediate nepheloid layers form during the seasonal shift from oxygenated to anoxic conditions, especially when local maxima of dissolved hydrogen sulfide detach from the seabed. The concentration of dissolved oxygen in the water varies significantly depending on the season, both in the surface and bottom layers, reaching its peak in winter and spring and its minimum in summer and autumn.

Predictive maintenance on ball mill liner using 3D scanner and its analysis in the mining industry of Papua Indonesia

In the mining industry, the primary production process entails transforming large ore deposits into valuable concentrates. To get minerals from large ores, a grinding machine is needed to reduce the size of the ore, and then the minerals can be extracted. The ball mill is an important part of the grinder in the mining industry. Maintenance is required for the machine to continue to work effectively and optimally. One method of preventing ball mill failures and minimizing company losses on a large scale is to predict the life of ball mill liners or predictive maintenance. Using a 3D laser scan, it is possible to determine the ball mill liner's wear and tear. On the basis of liner wear analysis, this information can then be used to generate a liner replacement schedule or estimate the remaining life of the ball mill liner or relining and lifetime forecast. This study aims to compare the 3D laser scan method and ultrasonic testing method in terms of liner wear analysis and forecasting. This study also demonstrates that the laser scanning method will be more effective and efficient than ultrasonic testing.

Clearing the air: unraveling past and guiding future research in atmospheric chemosynthesis.

Atmospheric chemosynthesis is a recently proposed form of chemoautotrophic microbial primary production. The proposed process relies on the oxidation of trace concentrations of hydrogen (≤530 ppbv), carbon monoxide (≤90 ppbv), and methane (≤1,870 ppbv) gases using high-affinity enzymes. Atmospheric hydrogen and carbon monoxide oxidation have been primarily linked to microbial growth in desert surface soils scarce in liquid water and organic nutrients, and low in photosynthetic communities. It is well established that the oxidation of trace hydrogen and carbon monoxide gases widely supports the persistence of microbial communities in a diminished metabolic state, with the former potentially providing a reliable source of metabolic water. Microbial atmospheric methane oxidation also occurs in oligotrophic desert soils and is widespread throughout copiotrophic environments, with established links to microbial growth. Despite these findings, the direct link between trace gas oxidation and carbon fixation remains disputable. Here, we review the supporting evidence, outlining major gaps in our understanding of this phenomenon, and propose approaches to validate atmospheric chemosynthesis as a primary production process. We also explore the implications of this minimalistic survival strategy in terms of nutrient cycling, climate change, aerobiology, and astrobiology.

Developing a Comprehensive Mathematical Model for Aluminium Production in a Soderberg Electrolyser

The technological process of aluminium electrolysis is a complex scientific and technical task. This is due to a large number of internal, external and resultant factors. The aim of this work is to analyse these factors, assess them and their influence on the technological process of electrolysis and develop a comprehensive and mathematical model of aluminium production in the Soderberg electrolyser. The work analyses the technological process of primary aluminium production on the basis of the Bayer method and then on the basis of the Hall–Eru method. The existing methods and technologies for computer modelling of the technological process are analysed. The modern methods of analysis for thermal and electromagnetic fields in electrolysers are considered. On the basis of an in-depth analysis, a number of factors influencing the process of primary aluminium production are identified. Using the methods of system analysis to analyse the identified factors, a ranked list of factors according to the degree of influence is obtained. Using the Pareto diagram, we obtain a list of factors with maximum impact. A conceptual model of the technological process is derived. Based on the obtained conceptual model, the mathematical model of the technological process is derived. The conducted research may be useful to specialists in the field of metallurgy for the analysis of the technological processes of primary aluminium production.

(Invited) Electrowinning of Aluminium and Carbon Footprint

Primary aluminium is produced by the Hall-Heroult process which is based on electrolysis in molten fluoride electrolyte, Na3AlF6-AlF3, at ~960 oC in which the raw material alumina is dissolved and decomposed into pure aluminium and CO2 gas due to the use of carbon anodes. The current efficiency with respect to aluminium can be as high as 96 % in Hall-Heroult cells. The total cell reaction is: Al2O3 (diss) + 3/2 C (s) = 2 Al (l) + 3/2 CO2 (g) The electrical energy consumption is around 12 - 15 kWh/kg Al, which corresponds to an energy efficiency of about 50 - 60 %. The main losses are due to a large ohmic voltage drop in the electrolyte and high anodic overvoltage. There are considerable emissions of CO2 from generation of electricity and the anode reaction. In addition there are emissions of CF4 and C2F6 (PFC gases) during so-called anode effect. Several efforts are under way to reduce the carbon footprint of the electrolysis process. One approach is to develop inert anodes to produce oxygen to eliminate the direct emissions of CO2 and PFC. The most promising inert anode candidates are based on alloys (Fe, Ni, Cu) in an electrolyte rich in KF with a lower liquidus temperature. Another idea is to produce aluminium based alloys directly during electrolysis by adding metal oxides in order to co-deposit alloying elements such as silicon, titanium and manganese. Such a method may give significant savings also in terms of carbon footprint since the current method for producing alloys is to add pure metals to liquid aluminium before casting. These alloying metals are associated with high emissions of CO2 durning their primary production processes.

Population connectivity and dynamics in early-life stages of Atlantic fish communities

IntroductionMany hypotheses have been suggested to explain recruitment variability in fish populations. These can generally be divided into three groups, either related to: larval food limitation, predation, or transport. Transport mechanisms are central for reproduction in pelagic species and three physical processes, concentration, enrichment, and retention are commonly referred as the fundamental “ocean triads” sustaining larval survival and thus success of reproductive effort. The aim of this study is to investigate linkages between primary production and transport processes of eggs and larvae for the most important commercial fish species in the Atlantic Ocean.MethodsWe simulated eggs and larvae dispersion using an individualbased model and integrating information on the fish ecology of the major fish stocks. Our work included a review on spawning ground locations, spawning time, eggs and larvae duration. Simulations were performed over a 10-year time period for 113 stocks (17 species) in order to assess variability in dispersion and common trends and factors affecting transport.ResultsThe level of primary production from initial to final position, i.e. from spawning to larval settlement, increased for some stocks (n=31), for others it declined (n=64), and for a smaller group (n=18) there was no substantial changes in level of primary production.DiscussionThis result implies that larval transport will not necessarily introduce larvae into areas of enhanced food availability expressed by the primary production at the site. These findings thus suggest marked differences in how physical and biological processes interact in the early life of major fish groups in the Atlantic Ocean. The results provide a further insight into fish larval drift and the potential role of primary production in emergence of spawning strategies.

The influence of biochemical parameters on primary production in the Gulf of Gdańsk region: A model study

Understanding the changing levels of biochemical parameters and the factors that influence them throughout the seasons is crucial for comprehending the dynamics of marine ecosystems. It also helps us identify potential threats that could harm their condition, aiding decision-making processes related to their protection. This study focuses on examining the variations in nutrients (such as nitrates, phosphates, and silicates), dissolved oxygen, and phytoplankton within the Gulf of Gdańsk. Additionally, we analyze the primary production process at three representative locations. To achieve this, we used data from the EcoFish biochemical numerical model. To ensure the model's accuracy, we compared its results with in situ data from the ICES database. The comparison revealed high correlations and minimal errors. Furthermore, we investigated how limiting factors impact primary phytoplankton production and demonstrated how the intensity of spring diatom blooms influences the nature of cyanobacterial blooms in the summer.

Институт «товарищеских начал» и субсидиарные конфигурации управления первичным производственным звеном в российской экономике

This work is devoted to the concept of partnership in the interpretation of A. A. Bogdanov. We are talking about comradely principles in the socio-economic system, that is, about comradely relations, a comradely organization, a comradely collective, a comradely society. The author makes an attempt to highlight the distinctive features and signs of “partnership”, so that in the future, with the help of these signs, it would be possible to select and consider specific forms of organizational relations on a comradely basis, as well as to conduct a comparative analysis of these forms of comradely organization of the economy Using examples of specific business units. The object of the study was the organization and structure of primary production processes, independent management. We are talking only about partnerships engaged in simple forms of production labor, the primary production process, about those subsidiary configurations for which the sign of the notorious “friendliness” is supposedly a key social criterion. The following forms of comradely economic relations are consistently considered in the work: Old Believer farms, monastic (temple) farms, Cossack communities, peasant farms, volunteer movement, as well as formal and informal associations of citizens engaged in creative practice in the field of folk art crafts and local associations “on interests”, and family business associations that legally exploit the statute of the subject of relations of taxation of professional activity (self-employment). The authors draw conclusions about the reason for the stability of the functioning of economic partnerships, which lies in the fact that economic practice is influenced by social institutions: the original way of life, religious beliefs, professional hobbies, high citizenship, blood ties, labor collectives that ensure friendly relations. “Friendly principles” are more typical of forms of organization, which are subsidiary configurations of management of the primary link of production, in contrast to the joint-stock form of organization of social production – a combination of labor law and entrepreneurial relations with the motivation of survival and enrichment.

A new procedure for autonomous acquisition of photosynthesis-irradiance curves on a microphytobenthic biofilm

Despite their high productivity and their key role in coastal processes, microphytobenthic biofilm studies remain relatively scarce because in situ, meteorological hazards make it difficult to acquire reproducible measurements, also due to difficulties in properly reproducing field conditions in the laboratory. Therefore, in order to better understand the processes of microphytobenthic primary production, we have developed an automated laboratory system and procedure with variable light intensity, with a large number of replicates. This article aims to provide a description of the creation of a P-I curve based on a total of 128 vertical profiles recorded on a sediment core taken in situ, placed in the automated system and studied under controlled conditions of temperature and air humidity while light intensity was varied automatically, thus allowing to work in standard and replicable conditions. With measured production levels of up to 14.68 ± 3.70 mmol O2.m-2.h-1 and a productivity of 0.06 ± 0.01 mmol O2.m-2.h-1 per gram of Chl a corresponding to what is generally found in temperate environments, we have shown that our system is suitable for high frequency measurements and, by combining surficial measurements of modulated fluorescence and oxygen microprofiling in sediments, complementary information from a large dataset on photosynthetic and microphytobenthic migratory activity may be obtained under standard conditions. The development of this tool has made it possible to highlight a stabilization time for oxygen fluxes. For our study conducted in a temperate environment, we observed a time lag of a few minutes that should be considered when acquiring PE curves in the laboratory to study microphytobenthic photosynthetic capacities. This tool also allowed to describe microphytobenthic migration in response to light exposure, with successive steps observed through fluorescence and oxygen profiles. First, microphytobenthos migrated towards the surface until the optimal intensity of production at 475 µmol photons.m-2.s-1, then from this intensity as well as towards 780 µmol photons.m-2.s-1, downwards migratory movements were detected. This system is a working basis which can open interesting perspectives for the study of the effect of other abiotic (or biotic) parameters.

DYNAMIC OF CHANGING AREA OF SUSPENDED SOLID BY UTILIZING LANDSAT 8 OIL IMAGES IN LAKE SINGKARAK, WEST SUMATRA PROVINCE, 2017 and 2022

TSS is suspended materials (diameter > 1 µm) retained on a millipore filter with a pore diameter of 0.45 µm. TSS consists of silt and fine sand and micro-organisms. The main cause of TSS in waterways is soil erosion or soil erosion that is carried into water bodies. If the TSS concentration is too high, it will inhibit the penetration of light into the water and result in disruption of the photosynthesis process (Effendi in Lestari, 2009:4). Many activities cause turbidity that affects the penetration of sunlight into water bodies, so it can hinder the process of photosynthesis and primary production of waters. Turbidity usually consists of an organic particle originating from watershed erosion and resuspension from the lake bottom. Keywords : Normalized Difference Vegetation Index, Normalized Burn Ratio, Landsat 8, Severity Level of Forest and Land Fires. Based on the results of the study, researchers have obtained TSS values ​​in 2017 and 2022 at Lake Singkarak with the Landsat 8 image data processing method using the Syarif Budiman algorithm with several stages, namely first combining image data bands from band 1 to band 7 then cropping which serves to determine the area to examine then performs masking which functions to separate land from water and then enter the Syarif Budiman algorithm formula then classify the TSS values ​​in Lake Singkarak. It can be seen that the predicted TSS concentration has not been too much different from the TSS concentration in the field. researchers have obtained TSS values ​​in 2017 and 2022 at Lake Singkarak with the Landsat 8 image data processing method using the Syarif Budiman algorithm with several stages, namely first combining image data bands from band 1 to band 7 then cropping which functions to determine the area which will be examined then do masking which functions to separate land from water and then enter the Syarif Budiman algorithm formula then classify the TSS values ​​in Lake Singkarak. It can be seen that the predicted TSS concentration has not had too much difference in the concentration in the field. researchers have obtained TSS values ​​in 2017 and 2022 at Lake Singkarak with the Landsat 8 image data processing method using the Syarif Budiman algorithm with several stages, namely first combining image data bands from band 1 to band 7 then cropping which functions to determine the area which will be examined then do masking which functions to separate land from water and then enter the Syarif Budiman algorithm formula then classify the TSS values ​​in Lake Singkarak. It can be seen that the predicted TSS concentration has not to have o much difference with wififrameS concentration in the field.

PHYTOPLANKTON PRIMARY PRODUCTIVITY

Primary productivity is an important integral parameter describing energy potential of aquatic organisms’ vital activity. Primary productivity determines the quality of water environment, its self- purifying capacity – from the Global Ocean to various continental ecosystems (Odum 1953, Williams et al. 2002, Bott et al. 2006, Kuehl and Troelstrup 2013).
 Primary productivity is a bioenergy process transforming the solar energy into the energy of chemical bonds in organic matter, newly synthesized by the autotrophic link. The autotrophic link is mainly formed by algae from different ecological groups (phytoplankton, phytobenthos, phytoperiphyton) and higher aquatic plants.
 As any process of energy production and transition, primary production in aquatic ecosystems is regulated by the laws of thermodynamics: the first law – the Lomonosov-Lavoisier law, the second law – the entropy law (Odum 1953). It is necessary to state clearly, that green plants do not transform the total amount of the Sun’s radiant energy, but only a part of it, within the spectral range between 480 and 720 nm (within the wavelength band of photosynthetically active radiation).A simplified equation describing the primary production process can be represented as follows:Proceeding from the above equation, primary productivity may be considered equivalent to (analogous to) the photosynthesis intensity.
 There is a range of various methods for estimating PP: according to algal cell number, according to nutrient dynamic in water, according to diurnal dynamics of dissolved oxygen, according to chlorophyll a content, light-and-dark bottle method in oxygen or radiocarbon modification. With consideration taken of these methods’ advantages and disadvantages, researchers will be able to obtain the most reliable and unbiased primary productivity data.

Origin, composition, and accumulation of dissolved organic matter in a hypersaline lake of the Qinghai-Tibet Plateau

Inland saline lakes are widely distributed and commonly exist in arid and semi-arid regions. Dissolved organic matter (DOM) in saline lakes plays an important role in the global carbon cycle and is a key regulator of saline lake ecosystem functions through biotic and abiotic processes. However, the origin, composition, and cycling of DOM in saline lakes, especially hypersaline lakes, remain largely unknown. In this study, two lake brine DOM samples and three input river DOM samples from a hypersaline lake, Da Qaidam Lake (DQL) in the Qaidam Basin of the Qinghai-Tibet Plateau (QTP), were isolated and analyzed using a multi-analytical approach. The results indicated that, although terrestrial in origin, the DOM composition and features of DQL were dominated by indigenous in-lake processes owing to the very long water residence time of the lake brine. Lake DOM contained more aliphatic compounds but fewer aromatic compounds than DOM from the rivers. Lake DOM also exhibited more chemodiversity and contained highly saturated and oxidized components that were incorporated with heteroatoms. Despite the limited contributions from riverine DOM, some special features of lake DOM, such as the high content of sulfur-bearing components, may be partly related to the long-term accumulation of hotspring riverine input. Flocculation, photodegradation, microbial degradation, evapo-concentration, and primary production processes were considered synergistic factors in the persistence and features of the hypersaline lake DOM. The results of this study can further our knowledge of the transformation and long-term turnover of DOM in hypersaline lakes and how DOM chemodiversity changes across wide aquatic ecosystems.