Oxygen Concentration In Water Research Articles

Innovative multi-layered biocement development and marine implementation research that contributes to the creation of resilient eelgrass beds

Eelgrass (Zostera marina) beds are important sites of marine biodiversity. Professor Masataka Kusube, National Institute of Technology, Wakayama College, Japan, has extensive experience in this area of research. He focuses on the development of bio-cements created from locally sourced sea sand and bacteria and collaborates with chemicals and plastics manufacturers and local governments in his research on eelgrass meadows. Hydrogen sulfide interferes with cellular respiration and is therefore toxic to humans and animals. Recent research has suggested toxicity to plants, and it could be linked with a recent widespread decline in eelgrass meadows. Kusube has been developing bio-cements and utilises scanning electron microscopy (SEM) to visually examine its surface structure, as well as using PCR (polymerase chain reaction), 16S multigenomic sequencing, SYBR green staining and cell counts to further investigate and gather data on the growth and germination rates of eelgrass with and without his interventions. In the creation of bio-cements, Kusube and his team used urea-degrading bacteria isolating strains of bacteria that were able to provide the functions required. Using urea-degrading bacteria meant that the researchers could easily isolate them with phenol red staining as these colonies break down urea to produce ammonia, generating a distinct red colouration around colonies when using this indicator. So far, the team has found that water temperature and oxygen concentration can significantly affect germination rates, while Eelgrass growth can be promoted in the presence of organic matter and iron. This suggests the potential to enhance growth by manipulating these elements.

A phosphate-rich marine reservoir in the redox stratified Ediacaran ocean

AbstractPhosphorus (P) is the key nutrient thought to limit primary productivity on geological timescales, and hence P bioavailability exerted a major influence on Earth’s surface oxygenation dynamics through the Precambrian, with ensuing implications for biological evolution. Here, we document highly elevated P contents in non-glacial Ediacaran (635–541 Ma) iron formations from Northwestern China, with P dominantly occurring as carbonate fluorapatite formed during early diagenesis. These analyses, in combination with marine sediment P contents and phosphorite abundance data, point to a state change in oceanic P concentrations during the Ediacaran, which we attribute to enhanced recycling from marine sediments under redox-stratified conditions. Subsequent elevated rates of primary productivity and organic carbon production may have sustained the contemporaneous first appearance of complex deep marine habitats, and would have increased the extent and stability of surface water oxygen concentrations, leading to conditions conducive to the subsequent evolution of more complex animals.

Comprehensive Evaluation of Tomato Growth Status under Aerated Drip Irrigation Based on Critical Nitrogen Concentration and Nitrogen Nutrient Diagnosis.

In order to provide a theoretical basis for the rational application of nitrogen fertilizer for tomatoes under aerated drip irrigation, a model of the critical nitrogen dilution curve was established in this study, and the feasibility of the nitrogen nutrition index (NNI) for the real-time diagnosis and evaluation of the nitrogen nutrient status was explored. The tomato variety "FENOUYA" was used as the test crop, and aerated drip irrigation was adopted by setting three levels of aeration rates, namely, A1 (dissolved oxygen concentration of irrigation water is 5 mg L-1), A2 (dissolved oxygen concentration of irrigation water is 15 mg L-1), and A3 (dissolved oxygen concentration of irrigation water is 40 mg L-1), and three levels of nitrogen rates, namely, N1 (120 kg ha-1), N2 (180 kg ha-1) and N3 (240 kg ha-1). The model of the critical nitrogen concentration dilution of tomatoes under different aerated treatments was established. The results showed that (1) the dry matter accumulation of tomatoes increased with the increase in the nitrogen application rate in a certain range and it showed a trend of first increase and then decrease with the increase in aeration rate. (2) As the reproductive period progressed, the nitrogen concentration in tomato plants showed a decreasing trend. (3) There was a power exponential relationship between the critical nitrogen concentration of tomato plant growth and above-ground biomass under different levels of aeration and nitrogen application rate, but the power exponential curves were characterized by A1 (Nc = 15.674DM-0.658), A2 (Nc = 101.116DM-0.455), A3 (Nc = 119.527DM-0.535), N1 (Nc = 33.819DM-0.153), N2 (Nc = 127.759DM-0.555) and N3 (Nc = 209.696DM-0.683). The standardized root mean square error (n-RMSE) values were 0.08%, 3.68%, 3.79% 0.50%, 1.08%, and 0.55%, which were less than 10%, and the model has good stability. (4) The effect of an increased nitrogen application rate on the critical nitrogen concentration dilution curve was more significant than that of the increase in aeration rate. (5) A nitrogen nutrition index model was built based on the critical nitrogen concentration model to evaluate the nitrogen nutritional status of tomatoes, whereby 180 kg ha-1 was the optimal nitrogen application rate, and 15 mg L-1 dissolved oxygen of irrigation water was the optimal aeration rate for tomatoes.

Biomonitoring as an Effort to Monitor River Water Quality with Parameters of BOD, DO, pH, TDS and the Presence of Macrozoobenthos in the Rolak River Area, Surabaya City

Many of the person who built settlements in riverbank areas, this allows residents in riverbank areasto become accustomed to disposing of waste directly into the river. In the end, this waste threatens the success of river flow, polluted river water has a serious impact on the health and quality of the environment around the riverbanks, such as the negative impact caused by this pollution, for example, such as health which has an impact on the surrounding environment or others. Because it is important to understand the natural health relationship, this study chose a river area that is located around the Rolak area of Surabaya, this place was chosen because the area is around a densely populated area and an industrial area. So that it can be used as research because the area certainly has a high level of pollution. As a result of the impact of the many residential and industrial areas around the river, the biomonitoring method is carried out to identify river pollution from its physical habitat by monitoring environmental health using living organisms in the river. Therefore the biomonitoring method can be applied because the advantages of this method can also be used including helping identify by using test parameters such as measuring pH, temperature and oxygen content in river water. that has been done before. Then the biotic examination can be used as a guide that can represent the quality of a body of water, from observations at several points the river is known to have a color that tends to be brownish due to turbidity levels, the pH parameters at each sample point are classified as normal and for Total Dissolved Solid (TDS) there is content of 339 mg/l, this is thought to be due to the source of domestic waste pollution from residents' settlements around the river banks. For DO test results there are only five points that meet quality standards. As for the diversity of bioindicators at each point, such as the presence of weeds at the first point, while the presence of water hyacinth can only be seen at the third and fourth points, the macrozoobenthos that are commonly found in the mangrove area are from the Mollusca, Annelida, and Arthropoda.

First screening of bacteria assemblages associated with the marine polychaete Melinna palmata Grube, 1870 and adjacent sediments

Bacteria associated with marine invertebrate play a fundamental role in the biology, ecology, development and evolution of their hosts. Although many studies have been focused on the microbial populations of benthic and pelagic habitats, little is known about bacteria colonizing tube-dwelling polychaete. In this context, the current study provided the first characterization of the Melinna palmata Grube, 1870 microbiome based on Illumina sequencing of 16S rRNA gene of the polychaete tissue and proximate sediments collected from the Black Sea, Romania, along a 24.2 m – 45.4 m depth-gradient. The diversity, taxonomic composition and deduced functional profile of the tissue and sediments associated bacterial communities were compared and analyzed in relation with the environmental parameters. This polychaete harbored a distinct bacterial assemblage as compared to their sediments and independent on the depth of their habitat, including 8 phyla in tissues dominated by Proteobacteria, and 12 phyla in sediments majorly represented by Actinobacteriota, respectively. At order level, Synechococcales, Rhodobacterales and Actinomarinales were highly represented in the M. palmata microbiome, while Microtrichales, Anaerolineales and Caldilineales were mostly found in sediments. A significant correlation was observed between Cyanobacteria taxa and the dissolved oxygen concentrations in shallow waters impacted by the Danube inputs. Meanwhile, this phylum showed a positive correlation with Planctomycetota colonizing the invertebrate tissues, and a negative one with Actinobacteriota and Chloroflexi found in sediments. The deduced functional profile of these bacterial assemblages suggested the prevalence of the amino acid and carbohydrate metabolism for both analyzed matrices. This pioneering report on the M. palmata microbiome highlighted the environment contribution to bacterial species enrichment of the polychaete, and provided a glimpse on the putative role of microbial communities associated with this marine organism.

Metals and biogenic substances’ migration ability in the «bottom sediments – water» system under natural and experimental conditions


 
 
 The paper considers the results of long-term studies on some chemical elements’ migration (Al, Fe, Ti, Mn, Cu, Zn, Pb, N, P, Si) in the «bottom sediments – water» system of surface water bodies under the effect of different aquatic environment factors. The greatest effect is made by water bodies’ oxygen regime, pH, and presence of dissolved organic substances, in particular humic substances. The migration of manganese, iron, inorganic nitrogen and phosphorus from bottom sediments is controlled mostly by oxygen regime. Migration of these chemical elements significantly increases, when there is oxygen deficiency and anaerobic conditions are formed in the bottom water layer. It has been observed in both natural and experimental conditions. Man- ganese concentration increases in bottom water in 25–50 times, iron – in 1.3–13, inorganic nitrogen – in 5.3–19.3, and inorganic phosphorus – in 2.8–23 times. The dissolved oxygen concentration hardly has any effect on the migration of aluminium, titanium, copper, zinc, lead, and silicon from bottom sediments into the water. The chemical elements’ migration is significantly affected by a decrease in pH of water contacting with bottom sediments and the presence of humic substances in it. High humic substances concentrations promote a reduction in water pH and oxygen content, which is consumed for their oxidation. A case study of several water bodies illustrates the cumulative effect of water pH lowering, anaerobic conditions at the solid and liquid phases’ interface, as well as complexation with humic substances on chemical elements’ migration from bottom sediments. Experimental modeling has shown that the metal migration from bottom sediments occurs both due to their labile fractions and complex compounds with dissolved organic matter, especially with humic substances of low molecular weight (≤2.0 kDa). The share of the metal labile fraction gets higher, when water pH decreases. Under recent climate change, the probability of water’s secondary pollution with different chemicals increases significantly in summer. This is mainly caused by oxygen deficiency, water pH lowering, and reducing conditions at the «bottom sediments – water» interface with hydrogen sulphide being formed. This is especially true for highly eutrophic water bodies subject to human impact. The aquatic environment toxicity can get considerably higher due to the migration of chemicals with strong toxic properties from bottom sediments, as well as labile metal fractions, marked by higher bioavailability for hydrobionts.
 
 

Spatial differentiation of bottom waters in the geosystem of the Chita TPP-1 cooling reservoir

The aim of the study was to identify the spatial differentiation of the hydrophysical parameters of the bottom waters of the Chita TPP-1 cooling reservoir. On October 24 2022 hydrophysical parameters were studied using the YSI EXO 2 instrument: temperature, oxygen concentration in water, specific electrical conductivity, hydrogen index, redox potential and turbidity at the research stations. It was found that all indicators for the lake research stations are homogeneous, with the exception of temperature. Based on the data obtained, three clusters are identified: 1 – the main part of the cooling reservoir with the same hydrophysical parameters; 2 – the thermal part of the cooling reservoir with high temperature and relatively low oxygen content; 3 - the coastal zone of the cooling reservoir with increased turbidity.

Digital models for assessing the impact of aeration processes on reservoir aquaculture

The dissolved oxygen level in a water body is one of the problems affecting all its processes and living organisms. The article identifies the problems associated with insufficient oxygen concentration in water and affecting the ecosystem both within a water body and in the surrounding area. A system dynamics model is developed to predict such changes. The key objects and processes established through structural analysis, observation, synthesis, and mathematical statistics are at the heart of such a model. The application of simulation modeling methods to the obtained results allowed the creation of a model reflecting the dependence of parameters affecting the rate of processes and changes in their states, affecting the population of fish and other living organisms in the reservoir.

Ocean Oxygen, Preformed Nutrients, and the Cause of the Lower Carbon Dioxide Concentration in the Atmosphere of the Last Glacial Maximum

AbstractAll else equal, if the ocean's “biological [carbon] pump” strengthens, the dissolved oxygen (O2) content of the ocean interior declines. Confidence is now high that the ocean interior as a whole contained less oxygen during the ice ages. This is strong evidence that the ocean's biological pump stored more carbon in the ocean interior during the ice ages, providing the core of an explanation for the lower atmospheric carbon dioxide (CO2) concentrations of the ice ages. Vollmer et al. (2022, https://doi.org/10.1029/2021PA004339) combine proxies for the oxygen and nutrient content of bottom waters to show that the ocean nutrient reservoir was more completely harnessed by the biological pump during the Last Glacial Maximum, with an increase in the proportion of dissolved nutrients in the ocean interior that were “regenerated” (transported as sinking organic matter from the ocean surface to the interior) rather than “preformed” (transported to the interior as dissolved nutrients by ocean circulation). This points to changes in the Southern Ocean, the dominant source of preformed nutrients in the modern ocean, with an apparent additional contribution from a decline in the preformed nutrient content of North Atlantic‐formed interior water. Vollmer et al. also find a lack of LGM‐to‐Holocene difference in the preformed 13C/12C ratio of dissolved inorganic carbon. This finding may allow future studies to resolve which of the proposed Southern Ocean mechanisms was most responsible for enhanced ocean CO2 storage during the ice ages: (a) coupled changes in ocean circulation and biological productivity, or (b) physical limitations on air‐sea gas exchange.

Залежність лінійного зростання та виживання личинок субтропiчної прiсноводної креветки (Мacrobrachium nipponense Dе Haan, 1849) від температури і солоності

Purpose. Studies of the growth and survival of Oriental river prawn (Macrobrachium nipponense) larvae depending on water temperature and salinity during cultivation. Methodology. Experimental studies were carried out at the Aquatic Department of Aquatic Bioresources and Aquaculture of the Odesa State Ecological University in 2020-2021. Brood Oriental river prawns (Macrobrachium nipponense) were caught in the lower Dniester river and placed into a 0.8 m3 RAS. The larvae were stocked in separate aquariums with automatically maintained specified temperature regime. The first series of experiments in fresh water investigated the influence of water temperatures of 20–22, 22–24, 24–26, and 28–31°C on the growth of shrimp larvae (from the 1st stage to the Pl stage). Cultivation in water with a salinity of 5, 7, 12 ‰ was carried out at a temperature of 20–22, 22–24, 28–31 °C. Ten prawn larvae were measured daily under a binocular microscope (MBS-10) using an eyepiece-micrometer. The stage of larval development and the survival rate were determined. Water salinity was determined using an ATAGO-100 refractometer, and an Azha-101M thermal oximeter was used to determine the oxygen content in water. Statistical processing of data was carried out in Microsoft Excel. Findings. It was established that at a temperature of 24–26°C, the duration of the transition from one stage of larval development to another in Oriental river prawn (Macrobrachium nipponense) increased as the larvae grew and developed. It lasted 4–5 days in the first stages (1-3), then stages from 6 to 9 days in the later stages. High temperature stimulated the growth of larvae and accelerated their development. In fresh water at a temperature of 29–31°C, the length of postlarvae (Pl) reached 6.69±1.15 mm in 28 days of rearing. Cultivation at high temperature resulted in a significant variation in larval sizes (from 4.4 to 8.6 mm CV–25,27). At lower temperatures (25-27, 22-24 and 20-22°C), the average sizes of prawn postlarvae were smaller (5.83±0.78, 4.56±0.15, 4.43±0.15), and the survival rates increased (46, 49 and 54%, respectively). Survival of larvae was inversely dependent on temperature r = –0.89. It was minimal (32%) at a temperature of 29–31°C. The higher the growing temperature, the lower the output of postlarvae. Water salinity, like temperature, significantly affected the growth, survival and size uniformity of postlarvae. In water with a salinity of 5‰, postlarvae reached their maximum length (6.56±0.15 mm) at a temperature of 29-31 °C. At temperatures of 20-22 and 22-24 °C, the size of the postlarvae did not reliably differ among themselves. The maximum survival of postlarvae (52%) was noted at a temperature of 22-24°. Regardless of water temperature, salinity of 5‰ ensured high uniformity of larvae size (CV: 6.11–9.09). At a salinity of 7‰, the maximum length of postlarvae was reached at a temperature of 29-31oC, and the highest survival rate of prelarvae (34%) was noted at a temperature of 20-22oC. The size of the larvae and their survival at other growing temperature conditions did not differ significantly (Р<95). A salinity of 7‰ also ensured the uniformity of postlarvae sizes (CV: 6.12-8.97). At a salinity of 12‰, high water temperature stimulated the growth of larvae with relative uniformity of their linear sizes, but in all variants of the experiment the survival rate of postlarvae was very low (4–9%). Originality. Experimental data on the growth and survival of larvae of the Oriental river prawn (Macrobrachium nipponense) depending on temperature and salinity are presented for the first time. The influence of the salinity of the environment on the size uniformity of the larvae was established. Practical value. The obtained results can be used for the development and improvement of methods of artificial reproduction and cultivation of the Oriental river prawn (Macrobrachium nipponense) under controlled conditions in recirculation aquaculture systems (RAS).

The role of seasonal hypoxia and benthic boundary layer exchange on iron redox cycling on the Oregon shelf

AbstractWidespread hypoxia occurs seasonally across the Oregon continental shelf, and the duration, intensity, and frequency of hypoxic events have increased in recent years. In hypoxic regions, iron reduction can liberate dissolved Fe(II) from continental shelf sediments. Fe(II) was measured in the water column across the continental shelf and slope on the Oregon coast during summer 2022 using both a trace metal clean rosette and a high‐resolution benthic gradient sampler. In the summer, Fe(II) concentrations were exceptionally high (40–60 nM) within bottom waters and ubiquitous across the Oregon shelf, reflecting the low oxygen condition (40–70 μM) at that time. The observed inverse correlation between Fe(II) and bottom water oxygen concentrations is in agreement with expectations based on previous work that demonstrates oxygen is a major determinant of benthic Fe fluxes. Rapid attenuation of Fe(II) from the benthic boundary layer (within 1 m of the seafloor) probably reflects efficient cross‐shelf advection. One region, centered around Heceta Bank (~ 44°N) acts a hotspot for Fe release on the Oregon continental shelf, likely due to its semi‐retentive nature and high percent mud content in sediment. The results suggest that hypoxia is an important determinant of the inventory of iron is Oregon shelf waters and thus ultimately controls the importance of continental margin‐derived iron to the interior of the North Pacific Basin.

Root-zone aeration improves fruit yield and quality of tomato by enhancement of leaf photosynthetic performance

Heavy irrigation and soil compaction cause hypoxic stress in plant roots, which limits crop growth. This issue can be solved by root-zone aeration, but the photophysiological responses of crop plants to the dissolved oxygen (DO) concentration in irrigation water remain unclear. Here, a greenhouse plot experiment was conducted to investigate the changes in leaf photosynthesis and plant growth of tomato (Solanum lycopersicum L. cv. ‘Omanda 3′) under aerated irrigation with various DO concentrations. Plants were treated with three different levels of aeration: 5 mg L–1 DO (conventional subsurface irrigation as a non-aeration control), 15 mg L–1 DO (low aeration treatment), and 30 mg L–1 DO (high aeration treatment). Compared with the control, the aeration treatments promoted electron transport from the primary to secondary plastoquinone acceptors (QA to QB) of photosystem II (PSII) and increased leaf net photosynthetic rate in plants at the seedling, fruit expansion, and maturation stages. The opposite effects of aeration treatments were observed at the flowering and fruit-setting stage. The enhancement of leaf photosynthetic performance contributed to improved plant growth, fruit yield, and quality of tomato as a result of increased oxygen supply in the root zone. The aeration treatments additionally facilitated the biosynthesis and transport of photosynthetic carbon assimilates in plant tissues, as evidenced by increased starch and sucrose contents in the leaves and sucrose content in the roots. However, under the high aeration level, excessive transport of sucrose from leaves to roots hindered further improvements in tomato yield and biomass at the maturation stage. Based on plant photophysiological and yield performance, aerated irrigation with a low concentration of DO (15 mg L–1) is recommended for greenhouse tomato crops during the seedling, fruit expansion, and maturation stages, and there is no need of root-zone aeration at the flowering and fruit-setting stage.

Revisiting the relationship between the pore water carbon isotope gradient and bottom water oxygen concentrations

Reconstructing the oxygen content at the ocean floor provides insight into ocean circulation, ventilation, and carbon storage in the deep sea. The microbial breakdown of organic carbon within marine sediment through aerobic respiration consumes oxygen in the pore fluid and releases dissolved inorganic carbon. The offset in the carbon isotopic composition, δ13C, of epifaunal and infaunal foraminifera, Δδ13C, is considered to reflect the aerobic respiration of organic carbon and can be used to reconstruct the oxygen content of the bottom water. Previous work provided an empirical calibration that was suggested to be valid for oxygen reconstructions between 55 and 235 μmol kg−1. In this study, we apply a biogeochemical reactive transport model (RTM) to extend and update this calibration, allowing for the reconstruction of oxygen concentrations ([O2]) up to ∼300 μmol kg−1. Using the RTM and new bottom water [O2] and pore fluid measurements from Iberian Margin sediment cores, we also demonstrate that the calibration between the Δδ13C and bottom water [O2] must account for the coupled changes in the carbon system due to the respiration of organic carbon in the overlying ocean including the concentration and carbon isotopic composition of the dissolved inorganic carbon, and the δ13C of the organic carbon within the sediment column. We apply the improved calibration to reconstruct the changes in oxygen content at International Ocean Discovery Program (IODP) Site U1385 in the deep North Atlantic over the past 1.5 Myr.

Anoxia begets anoxia: A positive feedback to the deoxygenation of temperate lakes.

Declining oxygen concentrations in the deep waters of lakes worldwide pose a pressing environmental and societal challenge. Existing theory suggests that low deep-water dissolved oxygen (DO) concentrations could trigger a positive feedback through which anoxia (i.e., very low DO) during a given summer begets increasingly severe occurrences of anoxia in following summers. Specifically, anoxic conditions can promote nutrient release from sediments, thereby stimulating phytoplankton growth, and subsequent phytoplankton decomposition can fuel heterotrophic respiration, resulting in increased spatial extent and duration of anoxia. However, while the individual relationships in this feedback are well established, to our knowledge, there has not been a systematic analysis within or across lakes that simultaneously demonstrates all of the mechanisms necessary to produce a positive feedback that reinforces anoxia. Here, we compiled data from 656 widespread temperate lakes and reservoirs to analyze the proposed anoxia begets anoxia feedback. Lakes in the dataset span a broad range of surface area (1-126,909 ha), maximum depth (6-370 m), and morphometry, with a median time-series duration of 30 years at each lake. Using linear mixed models, we found support for each of the positive feedback relationships between anoxia, phosphorus concentrations, chlorophyll a concentrations, and oxygen demand across the 656-lake dataset. Likewise, we found further support for these relationships by analyzing time-series data from individual lakes. Our results indicate that the strength of these feedback relationships may vary with lake-specific characteristics: For example, we found that surface phosphorus concentrations were more positively associated with chlorophyll a in high-phosphorus lakes, and oxygen demand had a stronger influence on the extent of anoxia in deep lakes. Taken together, these results support the existence of a positive feedback that could magnify the effects of climate change and other anthropogenic pressures driving the development of anoxia in lakes around the world.

Water environment response of urban water networks in the Pearl River Delta (China) under the influence of typhoon rain events

Abstract Identifying water quality parameter concentrations and their drivers is important for the prevention and control of water environment pollution. In this study, we constructed an inverse model of water quality parameters based on measured water quality parameters and remote sensing spectral data for this study area using artificial neural networks. We investigated the water environment response of the urban water network in the Pearl River Delta under the influence of typhoon rain events and explored their spatial heterogeneity using a multiscale geographically weighted regression model. The results indicate that in regions with a high level of urbanization, the dissolved oxygen (DO) concentration in river water is lower, and the ammonia nitrogen (NH3-N) concentration is higher. Under the influence of typhoon rain events of varying intensities, the response of water quality parameters in the urban water network of Zhongshan City varies. The intensity of rainfall determines the impact of typhoon rain events on water quality parameter concentrations. Our results are expected to improve the understanding of water quality trends under the influence of typhoon rain events and help policymakers and planners better develop water environment control strategies during typhoon transit.

Modeling the Water Temperature Profile of Lakes: A Physics Informed Neural Network (PINN) Approach

Water temperature plays an important role in our environment and is applicable to nearly all limnology research, as the temperature of a body of water affects biological activity and growth of organisms such as algae and bacteria. Certain organisms have a preferred temperature range within which they can survive, while others become dormant or die when the water reaches extreme temperatures. The temperature of water also governs the maximum dissolved oxygen concentration of water. Dissolved oxygen in water is important for aquatic life because of its vital role in cellular respiration. Predicting water temperature is also an important factor in determining whether a body of water is acceptable for human use. Warm bodies of water may contain pathogens that can be dangerous to humans.
 
 Our research presents a computational method of determining lake water temperature through a novel technique known as physics-informed neural networks (PINNs). PINNs can be used to model and forecast the temperature of water over a specific time period by training a neural network using the data points derived from the discrete form of a partial differential equation and taking into account the boundary conditions. Several factors such as wind, precipitation, and solar energy effects on water temperature were investigated. By using a computer simulation in place of an analytical mathematical model, a tremendous increase in run time speed can be achieved. The results can be used to determine the patterns in water temperature throughout a year, demonstrating the advantages of a PINN over an analytical model.

Analyzing the response distribution of DO concentration and its environmental factors under the influence of typhoon rain events with remote sensing

Typhoon rain events are important factors that trigger changes in dissolved oxygen concentrations in watersheds. The direction of the typhoon driving force is clear, but the mode of action and mechanism are complex. Moreover, quantifying the relationship between these actions and dissolved oxygen is challenging. This study collected measured data from water quality monitoring and remote sensing during the 2022 typhoon rain events. By analyzing the changes in typhoon driving factors and dissolved oxygen (DO) concentrations in water under various typhoon storms, extended MOORA plus the full multiplicative form (MULTIMOORA), Multiscale Geographic Weighted Regression (MGWR), and spatial autocorrelation analysis were used to evaluate the response of DO concentration. Furthermore, the effects of the atmospheric environment under the influence of human activities on the response distribution of the urban water environment were analyzed. The results of the study showed that under the effect of a typhoon with higher rainfall intensity, the response of DO concentration in the water body of the river in the center of the city was better. However, the response of DO concentration in the water body at the mouth of the sea had a tendency to become worse. Under the influence of typhoon rain events with smaller intensity, the scouring effect of rainwater dominated, and the DO concentration response in the water body had a tendency to become worse. The analysis of spatial heterogeneity under the influence of human activities showed that the ranking values of DO concentration response in rivers in the city area of Zhongshan, under the influence of typhoon rain events, were positively correlated with the distribution of ozone (O3) concentration and sulfur dioxide (SO2) concentration in the eastern, central, and western parts of Zhongshan. Conversely, it was negatively correlated with the distribution of O3 concentration and SO2 concentration in the northern and southern parts of Zhongshan. Based on the research results, we constructed a technique to evaluate the response of dissolved oxygen concentration during the typhoon transit period, which can provide an indicator reference for urban managers in water environment management.

Artificial reef biofouling community impacts on ecosystem metabolism and biogeochemical cycling in estuarine waters of the northern Gulf of Mexico

Artificial reefs increase hard bottom habitat and bolster shoreline protection in coastal waters. Reefs are rapidly colonized by biofouling communities which can potentially alter ecosystem metabolism. Despite the high biomass and ubiquitous nature of biofouling communities, little is known about their ecosystem metabolism or role in biogeochemical nutrient cycling. Using a combination of laboratory and field-based methods, this study focused on the metabolic activity of artificial reef biofouling communities and their potential to contribute to water column hypoxia in a shallow subtropical estuary. Study objectives aimed to (1) measure in situ dissolved oxygen (DO) concentrations in surface and bottom waters along reef transects during summer months when episodic hypoxic events typically occur, (2) estimate respiration rates in relation to nutrient regeneration in the absence versus presence of biofouling communities, and (3) examine seasonal shifts in trophic structure by relating elemental C:N ratios and stable nitrogen isotope (δ15N) values of the biofouling community across eight sample periods. In situ DO in bottom waters was low near high profile reefs. Water column respiration and nutrient regeneration rates were comparable to other estuaries. Respiration and regeneration rates of ammonium and phosphate were all manifestly higher in the presence of a biofouling community. Biofouling metabolic-driven processes were higher at low profile reefs than at high profile reefs. Seasonal shifts in biofouling elemental composition indicated by higher C:N and lower δ15N during cooler months and lower C:N and higher δ15N during warmer months reflected a transition from a more autotrophic community in winter to a more heterotrophic community during the rest of the year. Our results demonstrate that artificial reef biofouling communities can potentially contribute to hypoxic conditions in coastal waters of the northern Gulf of Mexico.

Paleoproductivity and deep-sea oxygenation in Cosmonaut Sea since the last glacial maximum: impact on atmospheric CO2

The paleoproductivity in the Southern Ocean plays a crucial role in controlling the atmospheric CO2 concentration. Here, we present the sediment record of gravity core ANT37-C5/6-07, which was retrieved from the Cosmonaut Sea (CS), Indian Ocean sector of the Southern Ocean. We found that the change in the oxygen concentration in the CS bottom water is strongly correlated with the atmospheric CO2 fluctuations since the Last Glacial Maximum (LGM). Based on the change in the export production, we reconstructed the evolution history of the deep-water ventilation/upwelling in the study area. During the LGM, a large amount of respiratory carbon was stored in the deep Southern Ocean due to the effect of the low export productivity and restricted ventilation. The oxygen concentration was also low at this time. Despite the increase in paleoproductivity, the biological pump efficiency remained at a low level during the Last Deglaciation. Vast quantities of CO2 were released into the atmosphere through enhanced upwelling. The recovery of ventilation during this period facilitated the supply of oxygen-rich surface water to the deep ocean. Moreover, signals were identified during the transitions between the Heinrich Stage 1 (HS1), Antarctic Cold Reverse (ACR), and Younger Drays (YD) periods. During the Holocene, the productivity increased overall, and the oxygen in the bottom water was consumed but still remained at a high level. This may have been caused by the enhanced ventilation and/or the prevalence of East Cosmonaut Polynya (ECP) near Cape Ann.

Understanding Nutrient Loads from Catchment and Eutrophication in a Salt Lagoon: The Mar Menor Case

Eutrophication is a significant threat to aquatic ecosystems worldwide, and the Mar Menor hypersaline lagoon exemplifies a coastal lagoon at risk of algal blooms due to excessive nutrient loads, nitrogen, and phosphorus. These nutrients originate from various sources within the lagoon’s catchment area, including urban, agricultural, and livestock activities. Regular and occasional loads—during flood events—produce algal blooms that can significantly reduce the water oxygen content and cause massive mortalities, as observed in recent years. A daily algal growth model (Mmag) was developed to better understand the processes and determine key elements such as the phosphorus water–sediment interchange and deep water plants that effect the entire ecosystem and algal growth. The analysis developed can be applied in other wetlands around the world facing similar challenges. In the Mar Menor, both nitrogen and phosphorus have high relevance depending on the period of the year and the phosphorus legacy in the sediments. Floods are the main phosphorus input to the lagoon (80–90%), which goes to the sediment and is released after during the warm months in the following years. At the end of summer, phosphorus released from the sediment and the regular nitrate inputs to the lagoon increase the algal bloom risk. The good status of deep water plants, which reduces the phosphorus release in summer, is a key element to reduce the algal bloom risk. An integrated set of measures is required to reduce the mean chlorophyll to levels under 1 or 0.5 µgChla/L that can make the Mar Menor more robust and resilient.