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Surface modification of various polymer foils was achieved by UV activation and chemical grafting with cysteamine to improve surface properties and antimicrobial efficacy. UVC activation at 254 nm led to changes in surface wettability and charge density, which allowed the introduction of amino and thiol functional groups by cysteamine grafting. X-ray photoelectron spectroscopy (XPS) confirmed increased nitrogen and sulfur content on the modified surfaces. SEM analysis revealed that UV activation and cysteamine grafting resulted in distinct surface roughness and texturing, which are expected to enhance microbial interactions. Antimicrobial tests showed increased resistance to algal growth (inhibition test) and bacterial colonization (drop plate method), with significant improvement observed for polyethylene terephthalate (PET) and polyetheretherketone (PEEK) foils. The important factors influencing the efficacy included UV exposure time and cysteamine concentration, with longer exposure and higher concentrations leading to bacterial reduction of up to 45.7% for Escherichia coli and 55.6% for Staphylococcus epidermidis. These findings highlight the potential of combining UV activation and cysteamine grafting as an effective method for developing polymeric materials with enhanced antimicrobial function, offering applications in industries such as healthcare and packaging. [ABSTRACT FROM AUTHOR]

The water quality and resources of Lake Ontario's nearshore ecosystem undergo heightened stress, particularly along the northwest shoreline. Hydrodynamic processes linking the distinct nearshore and offshore trophic structures play a crucial role in transporting nutrient-loaded water along and across the shore. Despite the pivotal connection between algae growth and the development of nuisance proportions, the scales over which these processes operate remain poorly understood. This study delves into the exchange dynamics between nearshore and offshore areas of Lake Ontario throughout 2018, employing a validated three-dimensional numerical model. A virtual passive age tracer is utilized to discern horizontal mixing time scales between nearshore regions of the lake (water depth < 30 m) and offshore locations. The dispersal pattern, as revealed by a passive tracer released from eight points around the model lake's perimeter, indicates more extensive diffusion in late summer when lake-wide stratification is established, compared to the mixed period. Coastal upwelling events, leading to intrusions of hypolimnetic waters, significantly contribute to net cross-shore transport, with the most pronounced effects observed in May and June when the offshore thermocline is shallow. In the northern part of the lake, dispersal predominantly occurs alongshore, mirroring the prevailing cyclonic (counterclockwise) coastal circulation during the stratified season. This pattern is a consequence of a 45% increase in upwelling events compared to three decades ago. In the northwestern and southern sectors of the lake, elevated cross-shore mixing is attributed to geomorphology-induced cross-basin currents. [ABSTRACT FROM AUTHOR]

Yessotoxin (YTX) is a disulfated toxin produced by harmful dinoflagellates and causes risks to aquatic animals. Polystyrene (PS) microplastics could absorb toxins in seawaters but pose threats to organism growth. In this study, the combined toxic effects of YTX (0, 20, 50, and 100 µg L−1) and PS (0, 5, and 10 µg mL−1) on the survival, reproduction, and population growth of marine rotifer Brachionus plicatilis at 20 °C, 25 °C, and 30 °C were evaluated. Results indicated that the survival time (S), time to first batch of eggs (Ft), total offspring per rotifer (Ot), generational time (T0), net reproduction rate (R0), intrinsic growth rate (rm), and population growth rate (r) of rotifers were inhibited by YTX and PS at 25 °C and 30 °C. Low temperature (20 °C) improved the life-table parameters T0, R0, and rm at YTX concentrations less than 100 µg L−1. Temperature, YTX, and PS had interactive effects on rotifers' S, Ft, Ot, T0, R0, rm, and r. The combined negative effects of YTX and PS on rotifers' survival, reproduction, and population growth were significantly enhanced at 30 °C. These findings emphasized the importance of environmental temperature in studying the interactive effects of microplastics and toxins on the population growth of zooplankton in eutrophic seawaters. [ABSTRACT FROM AUTHOR]

The Indonesian seas are a renowned global biodiversity hotspot, yet nutrient sources and fluxes (especially the vertical flux) sustaining this richness remain unclear. Here, we used non‐atmospheric helium‐3 (3He) to constrain the vertical diffusion coefficient (Kd) in the Indonesian seas, which ranges from 5.2 × 10−5 to 2.3 × 10−3 m2 s−1 and averages 6.6 × 10−4 m2 s−1, a value notably higher than those found in the open ocean and in most marginal seas. We estimated that 6.9 ± 7.9 mmol m−2 d−1 of nitrate (NO3−) is vertically transported into the surface mixed layer, that is, >90% of the total NO3− required to support a net community production (NCP) of 470 ± 467 mg‐C m−2 d−1. Regions with narrow straits, steep topography and dynamic circulation with strong vertical mixing display high NCP and chlorophyll‐a, suggesting that vertical nutrient transport dominates biological productivity. Findings highlight the importance of vertical mixing in supplying nutrients and maintaining the extraordinary biological productivity and diversity in the Indonesian seas. Plain Language Summary: The Indonesian seas, at the center of the Indo‐Pacific Intersection, are recognized as a global hotspot of marine biodiversity. However, nutrient (e.g., nitrate) cycling in the Indonesian seas is poorly understood, such that nutrient sources and fluxes sustaining biological production remain unknown. The Indonesian seas lie on a plate tectonic belt, where intense submarine hydrothermal venting releases abundant primordial isotopic helium (3He) into the ocean interior that outgasses at surface providing an ideal tracer of vertical transport. We find that vertical diffusion in the Indonesian seas is notably stronger than those found in the open ocean and in most marginal seas, with a mean vertical diffusion coefficient (Kd) of 6.6 × 10−4 m2 s−1. Nitrate is vertically transported into the surface mixed layer at a rate of 6.9 ± 7.9 mmol m−2 d−1, which supports >90% of net community production (NCP) in the Indonesian seas. Here, narrow straits, steep and irregular topography and dynamic circulation with strong vertical mixing result in high chlorophyll‐a concentrations (a measure of primary producers' biomass) and NCP. This vertical nutrient transport supplies essential conditions for algal growth and "fuels" food web biological productivity. Thus, we suggest that strong vertical mixing plays a key role in making the Indonesian seas a global biodiversity hotspot. Key Points: The Indonesian seas present strong and spatially variable vertical mixingVertical mixing supplies >90% of nutrients in the surface mixed layer of Indonesian seasHere, vertical nutrient supply provides essential biogenic elements supporting high net community production and a biodiversity hotspot [ABSTRACT FROM AUTHOR]

Recent observations document increased abundance of algae in the headwater streams of Hubbard Brook Experimental Forest (HBEF). It is possible that this “greening up” of HBEF streams may be due to climate change, with rising temperatures, altering terrestrial phenology, and shifting hydrologic regimes. Alternatively, stream “greening” could be from the slow recovery of stream chemistry after decades of acid rain, which has led to rising pH, declining concentrations of toxic Al3+, and low solute concentrations. Four years of weekly algal measurements on artificial moss and ceramic tiles, along with six nutrient enrichment experiments, revealed new insights about the interactions between these two autotrophs. We found that in protected weir ponds and in stream channels, algal biomass was higher on artificial moss substrates than on tiles—with this effect amplified in the stream channels. These results suggest that bryophytes can provide physical protection from flood scour or may trap nutrients to support algal growth. In stream channels, algal biomass was higher in well‐lit habitats and time periods indicating strong light limitation. We only measured nitrogen and phosphorus limitation of algal biomass in nutrient enrichment experiments conducted within weir ponds, with higher light availability and lower flow. By comparison, results from the remaining four instream experiments provided little evidence for nutrient limitation, with only one trial showing increased algal growth in response to nutrient addition. The most striking implication of our study is the role of bryophytes in providing refugia, and potentially nutrients, to algae in shaded and oligotrophic headwater streams. [ABSTRACT FROM AUTHOR]

The production of hydrogen via dark fermentation generates carbon dioxide, which needs to be separated and re-utilized to minimize the environmental impact. This research investigates the potential of utilizing algae for carbon dioxide sequestration in hydrogen production via dark fermentation. However, algae alone cannot fully use all the carbon dioxide produced, necessitating the implementation of a multistage separation process. This study proposes a purification approach that integrates membrane separation with a photobioreactor in a multistage design layout. Mathematical models were used to simulate the performance efficiency of multistage design layout using MATLAB 2015b (Version 9.3). A detailed parametric analysis and the key parameters influencing the separation efficiency were conducted for each stage. This study explores how reactor geometry, operational dynamics (such as gas transfer rates and light availability), and algae growth impact both CO2 removal and hydrogen purity. An optimization strategy was used to obtain the set of optimal operating and design parameters. Our results have shown a significant improvement in hydrogen purity, increasing from 55% to 99% using this multistage separation process, while CO2 removal efficiency rose from 35% to 85% over a week. This study highlights the potential of combining membrane technology with photobioreactors to enhance hydrogen purification, offering a more sustainable and efficient solution for hydrogen production. [ABSTRACT FROM AUTHOR]

ABSTRACT Metabarcoding is a rapidly developing field for studying aquatic life and provides a promising alternative to microscopy. However, accurate assessments require that database errors and species boundaries be addressed, yet the use of only a short gene sequences in metabarcoding, may be insufficient for accurate species identification. This study examines the potential of metabarcoding in replacing traditional microscopic methods in planktic diatom identification. Phytoplankton samples were collected monthly from May 2021 to April 2022 at 13 sites on the Hungarian section of the River Danube. Environmental variables were measured, and electron microscopy and metabarcoding analyses were conducted. Both morphological and DNA analysis methods were used to study the Thalassiosirales order. Although there was some overlap in the taxa identified by both methods, there were also discrepancies, with certain taxa detected exclusively by one method. P‐distance analysis and BLAST search were used to correct misidentifications, revealing mismatches between database sequences and observed species. Phytoplankton community exhibited varying temperature and nutrients optima and tolerance ranges, which influenced their distribution patterns. During spring, diatoms—particularly Thalassiosirales—dominated the phytoplankton, with proportions decreasing in summer. Algal biomass in the Danube was highest in March, decreasing sharply by the end of summer and remaining low until the end of the growing season, the decrease relating to changes in the TN:TP ratio, which was very low in the warm water period (mostly below 10), leading to nitrogen limitation. Discrepancies between bioinformatic analysis and SEM observations revealed errors in the reference database. Our results clarify the functional group (FG) classification, which is important for both ecological status assessment and understanding of ecosystem functioning. Temperature is one of the most fundamental drivers of microbial nitrogen dynamics in rivers. Global warming is driving up the average temperature of the Danube, creating more favourable conditions for denitrification since the speed of microbial processes is higher in warm water. The increasingly common nitrogen limitation could potentially limit algal growth. Environmental factors, especially temperature and nutrient concentrations, significantly influenced the Danube's phytoplankton communities, with implications for ecosystem health and water quality assessment. Integrated approaches combining molecular techniques with traditional morphological analysis are needed for comprehensive ecological assessments, but accurate species identification and ecological status assessment require completeness in reference databases and the correction of database errors. [ABSTRACT FROM AUTHOR]

The present work reports a study on the interactive response of algae and other microorganisms coexisting in a natural water body to ultrasonic treatment for effective algal growth inhibition using ultrasonic treatments. The cellular damage caused by treatment was also visualised through SEM imaging. For an ultrasonic exposure of 10–30 min at 30 kHz frequency with ultrasonic power dissipated in the range of 4.2–12.5 W, the reduction in the algal cell density was changed from 37.82 to –52.73% after 7 days of observation period. The gradual decrease in the chlorophyll concentration signified the reduced photosynthetic activity after treatment. The damage created on the cell membrane by ultrasound was evaluated through the increased permeability of electrolytes from the cells and the rise in the conductivity of water. Following the lab-scale experimental studies and interpretation of the results obtained, field trials were carried out at a local natural pond (40*35 sq. metre) for 6 months and secondary clarifier in a local industry (20 m diameter) for 2 months, with some system working based on low power ultrasonic transmitters (power ∼ 25 W/h and frequency 20–40 kHz) and promising improvement in water quality could be observed with 85% and more than 95% algae removal efficiency, respectively. [ABSTRACT FROM AUTHOR]

The use of plant growth regulators is a new strategy for the industrial cultivation of microalgae to enhance growth performance and bioproduct synthesis. In the presented study, the changes in growth rate, final abundance, photosynthetic apparatus efficiency, cell metabolic activity and specific lipid content were evaluated in the haptophyte alga Isochrysis galbana in response to exposure to the herbicide glyphosate (25–100 µg L−1). The results showed that glyphosate at concentrations of 25–75 µg L−1 stimulated the growth and final biomass of I. galbana. Stimulation of algal growth was associated with an increase in the metabolic activity of cells and the efficiency of their photosynthetic apparatus. An intensive accumulation of lipids was observed in I. galbana at a glyphosate concentration of 50–75 µg L−1. Overall, the study demonstrates a potential strategy to utilise I. galbana to remove high concentrations of glyphosate from the medium while producing lipid-rich algal biomass. [ABSTRACT FROM AUTHOR]

The red alga Asparagopsis taxiformis has recently been recognized for its unique ability to significantly reduce methane emissions from ruminant animals when fed in small quantities. The main obstacle in using this seaweed as a methane‐mitigating feed supplement is the lack of commercially available biomass. Little is known about how best to grow this red alga on a commercial scale, as there are few published studies that have investigated the factors that influence growth, physiology, and overall performance. This study examined the effects of temperature and CO2 enrichment on the growth, photophysiology, and concentration of bromoform, the secondary metabolite largely responsible for methane reduction in A. taxiformis. A series of single and multifactor closed culture experiments were conducted on A. taxiformis collected, isolated, and cultured from populations in Southern California. We identified the optimal temperature range to be between 22 and 26°C, with significant short‐term stress observed below 15°C and above 26°C. Carbon dioxide addition resulted in increased performance, when accounting for growth per CO2 use. In general, we observed the highest bromoform concentrations in algae with the highest growth rates, but these results varied among experiments. These findings indicate that through environmental control and by addressing limiting resources, significant increases in biomass production and quality can be achieved. [ABSTRACT FROM AUTHOR]

Efforts to reduce the frequency, extent, and toxicity of harmful algal blooms (HABs) require knowledge about drivers of algal growth, toxin production, and shifts in phytoplankton community composition to cyanobacterial dominance. Although labile nitrogen (N) and phosphorus (P) fuel primary production, micronutrients also play roles as the enzymatic engines that facilitate rapid and efficient growth and toxin production. Macro‐ and micronutrient availability can shape community composition and function by selecting for particular taxa. To address how phytoplankton in two Great Lakes subbasins respond to macro‐ and micronutrients, we conducted bottle incubation enrichment experiments using water collected from two blooming and two nonblooming sites in Lakes Erie and Michigan during late summer (August). Three of the four sites exhibited multi‐nutrient limitation of growth. Both blooming sites responded strongest to NH4+ enrichment. Both nonblooming sites responded the strongest to PO43− enrichment, and three of the four sites responded in some way to a mix of micronutrients (Fe, Mn, Mo, Ni, and Zn). Microcystis aeruginosa relative abundance increased most with N enrichment, while P enrichment increased the abundance of diatoms and chlorophytes. At the Fox River, N‐enriched communities grew 10%–20% more than non‐N enriched communities (measured as chlorophyll a), and N‐enriched communities had, on average, over twice as much microcystin (non‐N communities average MC = 2.45 μg · L−1, +N communities MC = 5.35 μg · L−1). These overarching trends support the idea that control of HABs may not be effective with a P‐only approach. [ABSTRACT FROM AUTHOR]

In the present study, CeO2 nanoparticles were synthesized using one-pot green route with high yield using microalgae Chlorella sorokiniana. The synthesized CeO2 nanoparticles (CeO2-np) exhibited rapid photocatalytic degradation 98.2% of doxycycline (DC) (20 mg/L) in only 30 min under visible light at pH7 in water. It was encouraging that CeO2-np did not demonstrate a loss of photocatalytic activity up to five repeated cycles, confirming its stability during the degradation process. Moreover, cytotoxicity evaluation of CeO2-nps on the green alga Chlorella sorokiniana advocated its non-toxic nature by supporting algal growth (0.52 g/L biomass) with 13% total lipids after 12 days in DC treated water. Ultimately, the produced algal biomass could be further utilized as a feedstock of biofuel production. [ABSTRACT FROM AUTHOR]

Light is a crucial factor that influences algal production. Red and blue light have been widely utilized in two-stage cultivation approaches due to their significant roles in promoting algal growth and pigment accumulation. To investigate the effects of light on the growth of an isolated wild strain of Haematococcus pluvialis (H. pluvialis) and its astaxanthin production, white light (30 μmol photons m−2 s−1) mixed with various light intensities of red or blue light were applied to the algal culture during the stationary phase. The results indicate that white light combined with low-intensity red light (5 μmol photons m−2 s−1) significantly enhanced algal growth, achieving a maximum biomass of 0.43 g/L. The pH values in cultures exposed to all treatments involving red-light intensities were lower than those under solely white light conditions. Furthermore, the combination of white light and low-intensity red light improved photosynthetic efficiency, carbonic anhydrase (CA) activity, and the rate of CO2 fixation. In contrast, the mixture of white light with blue light at 15 μmol photons m−2 s−1 facilitated astaxanthin production, resulting in a maximum astaxanthin content of 6.75 mg/L. Blue light was found to increase reactive oxygen species levels, leading to elevated malondialdehyde (MDA) concentrations and enhanced catalase (CAT) activity. These findings suggest that red light plays a crucial role in activating CA activity and promoting cellular CO2 fixation, which helps maintain the stability of the culture medium pH and ultimately supports algal growth. Conversely, blue light contributes to photoprotective processes by accumulating protective pigments and enhancing the activity of protective enzymes; together, these mechanisms mitigate reactive oxygen species generated by blue light exposure. Our experimental results provide valuable insights for optimizing two-stage cultivation practices for isolated strains of H. pluvialis. [ABSTRACT FROM AUTHOR]

Coccolithophorid Emiliania huxleyi was isolated to clonal culture from plankton of coastal waters of the Black Sea in February, 2023. Algal virus strain EhV-SS2 affecting this algal species was isolated from coastal waters in May, 2023. By means of scanning electron microscopy, it was shown that viral particles were 124–174 nm in diameter with an icosahedral symmetry. Supercapsid was detected in this strain and its titer was determined (2.5 × 105 virions/mL). The effect of algal virus on E. huxleyi growth and efficiency of PS II (Fv/Fm) at different levels of biogenic elements in the medium was investigated. Throughout the latent period of algal virus (0–101 h), we observed a decrease in the Fv/Fm ratio in the algae as compared with control values. Within time interval from 101 to 168 h, first cells lysed by the virus were revealed in the culture by means of light and scanning electron microscopy. Over the period from 168 to 264 h, lysis intensified and its rate on full f/2 medium was five times greater than in the case of nitrogen or phosphorus deficit. The rate of cell lysis on seawater lacking nutrient elements was two times lower than on the full medium. By the end of the experiment (in 264 h), infected culture displayed functionally active cells sheeted with coccoliths and without them. The percentage of the latter on f/2 medium was 95%, whereas in the case of nitrogen and phosphorus deficit their proportion was small. [ABSTRACT FROM AUTHOR]

Urban and storm water retention ponds eventually become eutrophic after years of receiving runoff water. In 2020, a novel biological and chemical treatment was initiated to remove accumulated nutrients from an urban retention pond that had severe algae and weed growth. Our approach installed two 6.1 m × 6.1 m floating treatment wetlands (FTWs) and two airlift pumps that contained slow-release lanthanum composites, which facilitated phosphate precipitation. Four years of treatment (2020–2023) resulted in median nitrate-N concentrations decreasing from 23 µg L−1 in 2020 to 1.3 µg L−1 in 2023, while PO4-P decreased from 42 µg L−1 to 19 µg L−1. The removal of N and P from the water column coincided with less algae, weeds, and pond muck (sediment), and greater dissolved oxygen (DO) concentrations and water clarity. To quantify the sustainability of this bio-chemical approach, we focused on quantifying nitrate removal rates beneath FTWs. By enclosing quarter sections (3.05 × 3.05 m) of the field-scale FTWs inside vinyl pool liners, nitrate removal rates were measured by spiking nitrate into the enclosed root zone. The first field experiment showed that DO concentrations inside the pool liners were well below the ambient values of the pond (<0.5 mg/L) and nitrate was quickly removed. The second field experiment quantified nitrate loss under a greater range of DO values (<0.5–7 mg/L) by including aeration as a treatment. Nitrate removal beneath FTWs was roughly one-third less when aerated versus unaerated. Extrapolating experimental removal rates to two full-sized FTWs installed in the pond, we estimate between 0.64 to 3.73 kg of nitrate-N could be removed over a growing season (May–September). Complementary laboratory mesocosm experiments using similar treatments to field experiments also exhibited varying nitrate removal rates that were dependent on DO concentrations. Using an average annual removal rate of 1.8 kg nitrate-N, we estimate the two full-size FTWs could counter 14 to 56% of the annual incoming nitrate load from the contributing watershed. [ABSTRACT FROM AUTHOR]

This study investigates the effects of continuous and short-term direct current (DC) stimulation on the growth and nutrient composition of Nitzschia closterium f. minutissima, a marine diatom with significant potential in aquaculture feed. We explored the optimal conditions of DC stimulation by applying both short-term and continuous treatments at varying voltages (0 V, 1 V, 3 V, 5 V, 10 V for short-term; 0 V, 0.05 V, 0.5 V, 1 V for continuous). The results demonstrated that short-term DC stimulation significantly enhanced cell density and lipid accumulation, with maximum cell density increasing by 13.14% under 1 V stimulation compared to the control. However, continuous stimulation was less effective and showed growth inhibition in several cases. Nutrient analysis revealed that short-term stimulation, particularly at 3 V, led to a 67.66% increase in lipid content, while moderate continuous stimulation (0.5 V) showed a 39.47% increase in biomass dry weight. These findings suggest that short-term DC stimulation is a promising approach to optimize microalgal growth and nutrient accumulation for large-scale aquaculture production. [ABSTRACT FROM AUTHOR]

The world population is expected to increase up to 9.6 billion by 2050. This triggers the demand for food security and its nutritional value. Despite the advancements in the field of medicine, current research focuses on investigating natural‐origin functional foods with tremendous health‐supporting properties. It includes various natural sources such as animals, plants, algae, fungi, and bacteria. The Algae group is still under investigation to find the best alternative to other previously explored sources. Algae possess remarkable potential for synthesizing natural metabolites, including primary metabolites (polysaccharides, proteins, and lipids) and secondary metabolites (Flavonoids, bromophenols, phenolic compounds, and polyphenols). These bioactive compounds have enormous anticancer, antimicrobial, and neuroprotection applications. This provokes researcher interest in exploring algae strains to optimize their metabolite production to utilize them as a functional food. Metabolomics techniques can be utilized to investigate biological samples. It will create new ways to explore algae strains that have not yet been investigated. A closed pond cultivation system is attractive to enhance algae growth in highly controlled conditions. This review emphasizes algae metabolism, cultivation methods, metabolomics analysis, genetic engineering, and advanced genome editing tools such as the CRISPR CAS9 system, which can be utilized to manipulate the algae genome for increased production. [ABSTRACT FROM AUTHOR]

Inorganic carbon acquisition is essential to algal growth, while the limitations of dissolved inorganic carbon (DIC) on phytoplankton are still less known in lakes. Sediment is an active hot spot for microbial metabolism, driving the migration and transformation of elements in shallow lakes, which may control the DIC availability to influence algal spatiotemporal dynamics. Hence, we investigated the spatiotemporal changes of phytoplankton, DIC and sediment respiration rates in a eutrophic shallow freshwater lake under non-bloom conditions. There was a widespread deficiency of DIC in the lake, except the estuary. Sediment respiration was positively associated with changes in DIC concentrations, indicating that carbon metabolic activity of sedimentary microorganisms was an important inorganic carbon source for water columns. The availability of DIC in water columns regulated by sediment microbial respiration influenced the algal biomass, composition and productivity. The synergistic effects of seasonal temperature changes and sediment microbial respiration influenced the vertical distribution and migration of phytoplankton. Our results emphasized that carbon metabolic intensity of sediment microorganisms might play a key role in dynamics of phytoplankton, further impacting the spatiotemporal pattern and formation of algal bloom in eutrophic shallow freshwater lakes. [ABSTRACT FROM AUTHOR]

ABSTRACT As the exploration of deep‐seated oil and gas resources in the Turpan‐Hami Basin intensifies, there is an urgent need to thoroughly depict the geological characteristics of newly uncovered, underexplored strata in sub‐sag centers. This study undertakes the inaugural systematic geochemical analysis of mudstones atop the Sangonghe Formation, including palynological identification, maceral identification, biomarker analysis, total organic carbon (TOC) analysis, and pyrolysis. The findings reveal that the mudstone sequence, as the target layer, was deposited in a warm and moist paleoclimate and a weakly reducing to weakly oxidising saline water environment, fostering the growth of prolific algae and bacteria, thus ensuring substantial foundational materials for source rock formation. The organic matter in the mudstone sequence displays pronounced laminar accumulation. Despite the overall modest abundance, the organic matter features notable hydrocarbon‐generating potential per unit of organic carbon and favourable types. Humic‐sapropelic kerogens (type II1) are found in the mudstones, with organic matter generally reaching a mature to highly mature stage. These characteristics establish the mudstones as effective source rocks, furthermore, the hydrocarbon expulsion in the Xishanyao Formation precedes that of the Sangonghe Formation and that both formations constitute a sequential process in terms of hydrocarbon generation and expulsion timing and hydrocarbon contribution. Reanalyzing this mudstone sequence not only revises prior geological understanding of it as direct cap rocks, but also facilitates the reclassification of deep‐seated strata into three distinct petroleum systems. Centered around this source rock layer, dual modes, namely the “lower‐source rock and upper‐reservoir” and the “ lower‐reservoir and upper‐source rock” modes can be formed. These new insights will offer profound implications for hydrocarbon resource evaluation and future hydrocarbon exploration endeavours in the Shuixigou Group within the Taibei sag. [ABSTRACT FROM AUTHOR]

In this study, the Aquasim model has been applied and developed to simulate the processes occurring in the sediments of the eutrophic system at Quinte Bay, Canada. The findings reveal that phosphorus (P) retention varies both spatially and temporally across the three basins of the Bay. These variations are influenced by factors such as sedimentation history, the chemical form of P, topography, and historical land use. According to the model, recent data indicates a decline in accumulated P at two shallow sediment sites (B and N), potentially leading to increased P release from these sediments. In contrast, the deeper sediment site (HB) continues to show high and stable P accumulation, resulting in consistently low and relatively unchanged P release. This explains why P levels in the Bay remain high, contributing to the growth of algae. The study also highlights the importance of adequately reducing external P loading. Internal P loads only play a supportive role in achieving the desired ecological conditions of the Bay. [ABSTRACT FROM AUTHOR]

Phosphorus removal is critical for effective water treatment and the prevention of eutrophication. This study focuses on the modification of attapulgite, an economical clay material, with zirconium (Zr@ATP) to enhance its phosphorus adsorption capacity. Zr@ATP was comprehensively characterized, and its phosphorus-removal mechanisms were investigated. Additionally, its performance in water treatment was evaluated using a lake water-sediment system. Zr@ATP exhibited a high surface area of 329.29 m2/g. The static adsorption experiments revealed that Zr@ATP achieved a phosphorus-removal efficiency of 95.8% at an adsorbent dosage of 5 g/L. Kinetic studies indicated that the adsorption followed a pseudo-second-order model, with the primary mechanism being chemisorption via ion exchange. Application of Zr@ATP in a lake water-sediment system resulted in an 83.6% reduction in total phosphorus. The chlorophyll concentration significantly decreased from 32.33 μg/L to 8.56 μg/L, and the algal density decreased by 84.6%, effectively inhibiting algal growth. These results suggest that Zr@ATP is a promising adsorbent for sustainable phosphorus removal and eutrophication control in aquatic environments. [ABSTRACT FROM AUTHOR]

The Chlorophyceae algae, specifically Chlorella spp., have been extensively researched for biodiesel production. This study focused on the alga Chlorella variabilis RSM09, which was isolated from a brackish-water environment at Raksamae Bridge in Klaeng District, Rayong Province, Thailand. The effects of the carbon dioxide gas (CO2) concentration (0.03%, 10%, 20%, 30%, 40%, and 50% v/v), light intensity (3000, 5000, and 7000 Lux), and photoperiod (12:12, 18:6, and 24:0 h L/D) on algal growth and lipid production were investigated. The results indicated that C. variabilis RSM09 achieved optimal growth under 20% v/v CO2 aeration, with an optical density of approximately 2.91 ± 0.27, a biomass concentration of 1.32 ± 0.14 g/L, and a lipid content of 21.96 ± 0.29% (wt.). Among the three different light intensities, higher optical density (4.20 ± 0.14), biomass (1.79 ± 0.25 g/L), and lipid content (20.75 ± 2.0% wt.) were at the 5000 Lux of light intensity. Additionally, the photoperiod of 24:0 h (L/D) produced the highest biomass at 1.86 ± 0.21 g/L, followed by the 18:6 h light/dark photoperiod with a biomass of 1.65 ± 0.17 g/L, and the 12:12 h light/dark photoperiod with 1.35 ± 0.43 g/L. In contrast, the 18:6 h L/D photoperiod yielded a higher lipid concentration of 25.22 ± 2.06% (wt.) compared to the others. All cultured microalgae showed significant effects on fatty acid composition. Palmitic (16:0), linoleic (C18:2), and linolenic (C18:3) acids were predominant in C. variabilis RSM09 under all photoperiods. This study exhibited that the microalga C. variabilis RSM09 has great potential as a feedstock for biodiesel production. [ABSTRACT FROM AUTHOR]

The present study analyzes the potential propagation trajectories and fate of floating microplastic particles released on the Kara Sea shelf. The transport of microplastics is described using a Lagrangian model based on daily 2016–2020 data obtained from numerical modeling of Arctic Ocean dynamics. A particle biofouling model is used to simulate the submergence of floating microplastic particles in the water column. The model includes a parameterization of the processes of biofilm accumulation (via collision with algae in surrounding water, algae growth) and degradation (via respiration, mortality). The behavior of microplastic particles of different sizes (0.5 and 0.01 mm) during the sinking process and subsequent rising due to biofilm degradation is examined. The simulation results reveal that particles of 0.01 mm in size display a tendency to sink immediately during the process of biofouling. However, when the biofilm degraded, the particles exhibited a rising velocity, comparable to the current vertical velocity, and the particles remained submerged in the water for long periods. In contrast, the 0.5 mm particles remained at the surface for a longer period before sinking, accumulating biofilm. Subsequently, their behavior was oscillatory in response to changes in the biofilm, rising rapidly when the biofilm decayed and sinking rapidly again as a result of biomass accumulation. In winter, the 0.5 mm particles were mostly frozen into the ice. The phenomenon of biofouling, whereby microplastic particles of various sizes sink at different depths, results in considerable variation in the subsequent pathways of these particles in the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Caulerpa is a genus of green macroalgae that lives in tropical and subtropical coastal waters. It is an intriguing organism because, despite having plant-like structures, it is one giant cell – which, next to multiple nuclei, chloroplasts, and mitochondria, also contains endo- and epiphytic bacteria. The role of these bacteria is unknown, but they might impact the growth and development of the host, adaptation to environmental parameters, and, hence, the ecological success of these algae. We hypothesised that increased sulphide concentrations would trigger a significant shift in the microbial community composition associated with C. prolifera rhizoids, favouring sulphide-oxidizing bacteria. To test this hypothesis, we conducted a mesocosm experiment incubating C. prolifera in sediments with different sulphide concentrations and analysed the algal photosynthesis, growth, and microbiome composition. While photosynthesis was not affected, the Caulerpa weight-based growth rate decreased linearly with increasing sulphide concentration. To analyse the microbiome, we extracted DNA and RNA from the fronds, rhizoids, and the accompanying sediments and performed 16S amplicon sequencing. The microbiome of the fronds was unaffected in both the DNA and RNA samples. However, an increase in sulphide concentration coincided with a decrease in the relative abundance of sulphate-reducing bacteria associated with Caulerpa rhizoids, particularly from the family Desulfocapsaceae. In the RNA samples, potential sulphide oxidisers of the rhizoid-associated members of the Beggiatoaceae were detected. Our results suggest that the rhizobiome of Caulerpa plays a significant role in its adaptation to sulphide-rich environments, offering new insights into the complex interactions within marine holobionts. [ABSTRACT FROM AUTHOR]

ABSTRACT The marine microalga Emiliania huxleyi is widely distributed in the surface oceans and is prone to infection by coccolithoviruses that can terminate its blooms. However, little is known about how global change factors like solar UV radiation (UVR) and ocean warming affect the host‐virus interaction. We grew the microalga at 2 temperature levels with or without the virus in the presence or absence of UVR and investigated the physiological and transcriptional responses. We showed that viral infection noticeably reduced photosynthesis and growth of the alga but was less harmful to its physiology under conditions where UVR influenced viral DNA expression. In the virus‐infected cells, the combination of UVR and warming (+4°C) led to a 13‐fold increase in photosynthetic carbon fixation rate, with warming alone contributing a change of about 5–7‐fold. This was attributed to upregulated expression of genes related to carboxylation and light‐harvesting proteins under the influence of UVR, and to warming‐reduced infectivity. In the absence of UVR, viral infection downregulated the metabolic pathways of photosynthesis and fatty acid degradation. Our results suggest that solar UV exposure in a warming ocean can reduce the severity of viral attack on this ecologically important microalga, potentially prolonging its blooms. [ABSTRACT FROM AUTHOR]

Internal phosphorus loading (IPL), as an important part of lake phosphorus cycle and the key to solve the eutrophication problem, is still an important cause of regional and seasonal algal blooms for some mesotrophic lakes located in plateau areas. We investigated the composition, distribution of P fractions in sediments and suspended particulate matter (SPM) of Erhai Lake, southwest China, and explored the relationships between environmental variables and spatial-temporal variations of P fractions. The total P (TP) in surface sediments ranged from 817 to 1216 mg/kg, with inert Ca-P (32%) and Res-P (24%) predominating, at a moderate level. The comparison of short-term release fluxes (0.08 mg/(m2·d)) and long-term release fluxes (0.09 mg/(m2·d)) reflected that the northern region was recovering slowly from the previous P pollution. Mobile-P (the sum of loosely adsorbed P, iron bound P, and organic P) accounted for 52.3% of the TP in SPM and showed high spatial-temporal variations, which were closely related to the growth of algae throughout the investigation. The results suggested that sediments could make a sustained contribution to IPL, and that the P in SPM was highly active and significantly contributed to eutrophication in Erhai Lake especially at the time of seasonal alternations. Our data provided important theoretical bases for the relationship between internal phosphorus loading and eutrophication in plateau lakes. [ABSTRACT FROM AUTHOR]

A raceway pond is a type of closed-loop recirculation channel that is long and shallow and is commonly used for large-scale microalgae cultivation. A key issue with the incorrect design of a raceway pond is the presence of a dead zone, where the flow velocity is low or non-uniform. This can have a negative impact on the growth of algae and reduce the efficiency of the cultivation process. To address this issue, this study focused on analyzing the hydrodynamic performance of the pond by examining the effect of different aspect ratios on velocity uniformity. Aspect ratio refers to the ratio of the length/width. This study found that an aspect ratio greater than 15 provides better uniformity in flow velocity, improving microalgae growth in the pond. This paper also investigated the impact of the location of the paddle wheel, which is used to create flow and minimize dead zones. Two different locations of the paddle wheel were considered, and computational fluid dynamics and k-ω and large eddy simulation (LES) turbulence closure equations were used to simulate the hydrodynamics of the pond. This study found that the efficiency of the raceway pond is better when the paddle wheel is placed in the middle of the total length of the pond. After simulating the raceway pond using both the k-ω and LES turbulence models, it was found that the LES model provided better results. This suggests that the LES model was able to capture the turbulent flow characteristics more accurately in the raceway pond as compared to the k-ω model. [ABSTRACT FROM AUTHOR]

Long‐term carbon sequestration by the ocean's recalcitrant dissolved organic carbon (RDOC) pool regulates global climate. Algae and bacteria interactively underpin RDOC formation. However, on the long‐term scales, the influence of their persistent interactions close to in situ state on ocean RDOC dynamics and accumulation remains unclear, limiting our understanding of the oceanic RDOC pool formation and future trends under global change. We show that a Synechococcus‐bacteria interaction model system viable over 720 days gradually accumulated high DOC concentrations up to 84 mg L−1. Concurrently, the DOC inertness increased with the RDOC ratio reaching > 50%. The identified Synechococcus‐bacteria‐driven RDOC molecules shared similarity with over half of those from pelagic ocean DOC. Importantly, we provide direct genetic and metabolite evidence that alongside the continuous transformation of algal carbon by bacteria to generate RDOC, Synechococcus itself also directly synthesized and released RDOC molecules, representing a neglected RDOC source with ~0.2–1 Gt y−1 in the ocean. However, we found that although ocean warming (+4°C) can promote algal and bacterial growth and DOC release, it destabilizes and reduces RDOC reservoirs, jeopardizing the ocean's carbon sequestration capacity. This study unveils the previously underestimated yet significant role of algae and long‐term algae‐bacteria interactions in ocean carbon sequestration and its vulnerability to ocean warming. [ABSTRACT FROM AUTHOR]

Simple Summary: The rapid development of turtle breeding leads to the risk of aquaculture wastewater pollution. The microalgal strain Desmodesmus sp. CHX1 has shown great potential in removing nutrients from wastewater. This study investigated the effects of temperature and light on the growth of Desmodesmus sp. CHX1 and its nutrient removal in turtle aquaculture wastewater to find the optimal conditions for growth and nutrient removal efficiency. This study was relevant to the development of new strategies for the resource utilization of turtle aquaculture wastewater based on microalgae cultivation. The aim of this study was to explore the effects of temperature and light on microalgal growth and nutrient removal in turtle aquaculture wastewater using a single-factor experiment method. Results showed that the growth process of Desmodesmus sp. CHX1 in turtle aquaculture wastewater exhibited three stages, namely adaptation, logarithmic, and stable periods. Temperature and light significantly influenced the growth and protein and lipid accumulation of Desmodesmus sp. CHX1. The optimal conditions for the growth and biomass accumulation of Desmodesmus sp. CHX1 included a temperature of 30 °C, a photoperiod of 24L:0D, and a light intensity of 180 μmol photon/(m2·s). Increased temperature, photoperiod, and light intensity enhanced nutrient removal efficiency. Maximum nitrogen removal was achieved at a temperature of 30 °C, a photoperiod of 24L:0D, and a light intensity of 180 μmol photon/(m2·s), with the removal efficiency of 86.53%, 97.94%, 99.57%, and 99.15% for ammonia, nitrate, nitrite, and total phosphorus (TP), respectively. Temperature did not significantly affect TP removal, but increased photoperiod and light intensity improved the removal efficiency of TP. The development of microalgae biomass as a feed rich in protein and lipids could address feed shortages and meet the nutritional needs of turtles, offering a feasible solution for large-scale production. [ABSTRACT FROM AUTHOR]

Highlights Local algae outdoor production on undiluted anaerobic digestate over 1-year. Dominating eukaryotes transitioned from Coelastrum to Chlorella in warmer season. Culture collapsed when pretreatment on digestate was purposefully stopped. Low cyanobacteria abundance observed in the consortium. Growing algae on anaerobic digestate could decrease the algal production cost while reducing nutrient pollution. In past work, we developed a successful biological pretreatment for digestate that enables rapid algal growth on digestate without dilution. The objective of this work was to test the effectiveness of this pretreatment in outdoor algae cultures over a year-long timeframe. The study was conducted in semi-continuous, replicated bubble column photobioreactors in Auburn, AL, USA. Algae could grow successfully in pretreated digestate during the fall, spring, and summer, achieving average growth rates of 30, 42, and 66 mg L-1 d-1, respectively. Although the cold temperatures in winter suppressed algal growth, external heating was not required to keep the cultures alive. For two weeks during the summer, the system was challenged with 100% digestate that did not undergo pretreatment, and the algal community suffered a culture collapse with a significant (p < 0.001) decrease in productivity compared to the previous batches in which pretreatment was used. Nitrogen, phosphorus, and sulfur removal were observed during robust algal growth. There was no nitrification in the photobioreactors during the initial 200 days, but evidence of nitrification emerged during the summer and persisted into the fall. Nitrospirae were detected by 16S rRNA sequencing, proving that nitrifying bacteria could adapt to high ammonium (462 - 1502 mg/L). The eukaryotic community was dominated by Coelastrum (>90%) in the cold season, and the dominance transitioned to Chlorella in the warm season (>95%) based on 18S rRNA sequencing. The low relative abundance of cyanobacteria showed that green algae were the favored photosynthetic organisms in the system. [ABSTRACT FROM AUTHOR]

Genus Microcystis is the most common dominant species of bloom-forming cyanobacteria. Growth and colony formation are critical processes for the occurrence of Microcystis blooms. To identify allelochemicals that can inhibit the growth and colony formation of Microcystis, Microcystis aeruginosa was cultivated and treated with various concentrations of gramine, catechol, berberine, and sanguinarine in laboratory. Results indicate that the growth, colony formation, and extracellular polysaccharides (EPS) content of Microcystis were significantly inhibited when treated with gramine, catechol, and berberine in appropriate concentrations at high iron level (6.8 mg/L). Microcystis growth was inhibited and colony formation and EPS content were promoted when treated with sanguinarine at high iron level. These findings suggest that cyanobacterial blooms can be controlled by regulating the input of gramine, catechol, and berberine. Furthermore, this study revealed that plant allelochemicals could affect the growth and morphology of algae in aquatic ecological restoration, which may be potentially important for improving water quality. [ABSTRACT FROM AUTHOR]

We evaluated the thermal and chemical stratifications of Paldang Lake using Schmidt's stability index (SSI) and the chemical stratification index (IC-i) with weekly data from 2013 to 2022. The temporal trends of stratification were analyzed alongside correlations with meteorological, hydrological, and water quality variables. Thermal stratification intensified with rising air temperature and sunshine duration, while hydrological factors like discharge and retention time affected SSI during periods with less than five days of water retention. During summer, fewer occurrences of intense rainfall or early rainfall before August led to stronger stratification. In fall, nutrient influx from external sources during summer stimulated algal growth, increasing Chlorophyll-α (Chl-α) concentrations. Summer rainfall had a significant impact on the strength and duration of stratification in Paldang Lake. Annual rainfall patterns and subsequent changes in discharge were key factors affecting the physical environment of the lake, which in turn determined water quality and the extent of algal blooms. We provide insights into the seasonal stratification and water quality variations in temperate river-type reservoirs like Paldang Lake. SSI and IC-i from this research can be applied to understand stratification and mixing dynamics in other lakes. [ABSTRACT FROM AUTHOR]

Tropical carbonate systems are valuable archives of paleoenvironments, as the carbonate growth is intimately affected by water depth and climatic conditions. Geochemical data from the Burdigalian interval in IODP Site U1468 in the Maldives, northern Indian Ocean, were integrated with sedimentological and paleontological data for a more detailed reconstruction of depositional history. Generally, the Sr/Ca values of slope sediments record highstand progradation in both sequence unit and whole Burdigalian interval, while the absence of higher Sr/Ca ratio close to the sequence boundary during the early Burdigalian could be related to the erosion of deeper-water sediments due to the activity of bottom current. From 20.5 to 19.1 Ma and from 17.9 to 17.2 Ma, nutrient level and productivity were moderately elevated due to the terrigenous input by the intensified South Asian Proto-Monsoon, which also helped cause more reducing conditions in the distal slope. Moreover, increased nutrient level facilitated the growths of calcareous algae and sponges, while it was not favorable for coral development. The elevated nutrient level, higher sea level, and monsoon-induced current contributed to the backstepping of the outer margin during the late Burdigalian. Our study shows an example on how a tropical carbonate platform evolved in response to the interplay of sea-level and paleoclimatic conditions. Findings are expected to be applicable to other tropical carbonate platforms. [ABSTRACT FROM AUTHOR]

Microalgae have demonstrated biostimulant potential owing to their ability to produce various plant growth-promoting substances, such as amino acids, phytohormones, polysaccharides, and vitamins. Most previous studies have primarily focused on the effects of microalgal biostimulants on plant growth. While biomass extracts are commonly used as biostimulants, research on the use of culture supernatant, a byproduct of microalgal culture, is scarce. In this study, we aimed to evaluate the potential of Chlorella vulgaris culture as a biostimulant and assess its effects on the growth and drought tolerance of Arabidopsis thaliana, addressing the gap in current knowledge. Our results demonstrated that the Chlorella cell-free supernatant (CFS) significantly enhanced root growth and shoot development in both seedlings and mature Arabidopsis plants, suggesting the presence of specific growth-promoting compounds in CFS. Notably, CFS appeared to improve drought tolerance in Arabidopsis plants by increasing glucosinolate biosynthesis, inducing stomatal closure, and reducing water loss. Gene expression analysis revealed considerable changes in the expression of drought-responsive genes, such as IAA5, which is involved in auxin signaling, as well as glucosinolate biosynthetic genes, including WRKY63, MYB28, and MYB29. Overall, C. vulgaris culture-derived CFS could serve as a biostimulant alternative to chemical products, enhancing plant growth and drought tolerance. [ABSTRACT FROM AUTHOR]

Settlement induction potential of two red algae, Sahlingia subintegra and Rhodosorus marinus, and one green macroalgae, Ulvella leptochaete was examined to identify potential alternative algal species to improve reliability and reproducibility of Haliotis tuberculata sp. settlement. CCA was used as a positive control. Settlement rates, post-larval survival and growth of Haliotis tuberculata sp. were evaluated for different algal species tested. Results showed that Sahlingia subintegra induced significantly higher settlement rates (58.17 ± 12.71%) compared to CCA, Ulvella leptochaete and Rhodosorus marinus. In all treatments, post-larvae were weekly fed a mix of diatoms (Amphora sp., and Navicula incerta). At four weeks post settlement, post-larval survival rates were significantly higher on CCA and Sahlingia subintegra substrates compared to the other two algal species tested. However, at four and five weeks post settlement there were no significant differences in post-larval shell length and growth rates between CCA and Sahlingia subintegra substrates. These findings suggest that Sahlingia subintegra could be a promising alternative red macroalgae providing settlement cue for abalone hatchery stages, particularly for Haliotis tuberculata sp. and could contribute to improve abalone breeding techniques through the selection of alternative settlement substrates that could be easily managed in abalone farms environments. [ABSTRACT FROM AUTHOR]

Abalone is one of the most important small-scale fisheries in Mexico and is challenged by multiple stressors. For example, the loss of the native main food, Macrocystis pyrifera, and the subsequent takeover of non-indigenous algae species represent a major threat to abalone growth and survival. In Baja California, Mexico two introduced macroalgae, Undaria pinnatifida and Sargassum horneri have become common in the past decade with unknown consequences on native herbivores. In this work, we explored the effect of these invasive algae on the growth and survival of juvenile red abalone, Haliotis rufescens. One hundred and ten juvenile red abalone were tagged and fed with invasive algae U. pinnatifida and S. horneri, and a control with M. pyrifera. Then, the shell length, body weight, and survivorship were assessed monthly for 90 days. Results show that abalone fed U. pinnatifida had a total growth in length, weight, and survivorship, similar to those fed native M. pyrifera. In contrast, abalone fed S. horneri had significantly lower overall performance. Marine heatwaves and other climatic impacts are expected to favour the establishment of invasive species. These results may be relevant to inform local fisheries and management efforts in this area under future scenarios. [ABSTRACT FROM AUTHOR]

Nutrient enrichment can impair the biotic integrity of steams and rivers. Nutrients derived from land use practices have been identified as sources of water quality impairment in several Central California Coast watersheds resulting in excess algal growth. We developed an algae-based multi-metric index to assess the biotic integrity of streams and rivers in this region because algae often respond directly to changes in nutrient levels. Additionally, we apply the algal index of biotic integrity to the development of an effects-based nitrogen reduction target. Eleven individual metrics based on diatom autecologies, community structure, ecological guilds, tolerance, and intolerance were incorporated into the index. All algal production metrics failed reproducibility criteria for inclusion in the index. The index of biotic integrity was highly correlated with human disturbance (r = − 0.6213) and was significantly different between classes of least-, intermediate-, and most-disturbed sites. Piecewise linear regression showed a steep negative relationship between nitrate–N and the index with a breakpoint of 0.505 mg/L nitrate–N, above which the negative trend became insignificant. This change in the relationship between nitrate and the index of biotic integrity suggests that this breakpoint can aid the development of a reasonable effects-based criterion for nitrate–N in this region. [ABSTRACT FROM AUTHOR]

• The accuracy of the eDNA method of planktic algae in the Tuojiang River Basin was higher than that of conventional survey methods. • SEM analysis showed algae growth was significantly affected by N/P ratio, and was mainly limited by phosphorus. At the same time, SEM also obtained the causal relationship of each water environment and water quality parameters. • Mantel analysis showed the phytoplankton in TRB water exhibits strong correlations with NH 3 -N, COD, TDS, TN, and TP and all of which were statistically significant relationships. • The factors influencing phytoplankton growth in the TRB were consistent with the observed and monitored data. Tuojiang River Basin is a first-class tributary of the upper reaches of the Yangtze River—which is the longest river in China. As phytoplankton are sensitive indicators of trophic changes in water bodies, characterizing phytoplankton communities and their growth influencing factors in polluted urban rivers can provide new ideas for pollution control. Here, we used direct microscopic count and environmental DNA (eDNA) metabarcoding methods to investigate phytoplankton community structure in Tuojiang River Basin (Chengdu, Sichuan Province, China). The association between phytoplankton community structure and water environmental factors was evaluated by Mantel analysis. Additional environmental monitoring data were used to pinpoint major factors that influenced phytoplankton growth based on structural equation modeling. At the phylum level, the dominant phytoplankton taxa identified by the conventional microscopic method mainly belonged to Bacillariophyta, Chlorophyta , and Cyanophyta , in contrast with Chlorophyta, Dinophyceae , and Bacillariophyta identified by eDNA metabarcoding. In α-diversity analysis, eDNA metabarcoding detected greater species diversity and achieved higher precision than the microscopic method. Phytoplankton growth was largely limited by phosphorus based on the nitrogen-to-phosphorus ratios > 16:1 in all water samples. Redundancy analysis and structural equation modeling also confirmed that the nitrogen-to-phosphorus ratio was the principal factor influencing phytoplankton growth. The results could be useful for implementing comprehensive management of the river basin environment. It is recommended to control the discharge of point- and surface-source pollutants and the concentration of dissolved oxygen in areas with excessive nutrients (e.g., Jianyang–Ziyang). Algae monitoring techniques and removal strategies should be improved in 201 Hospital, Hongrihe Bridge and Colmar Town areas. [Display omitted] [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) represent anomalously warm temperature conditions of seawater that may affect marine life and ocean biogeochemistry. Under such conditions, phytoplankton communities may modify their structure and functions, and their resilience is not assured. This study characterizes the impact of MHWs on the phytoplankton spring bloom in the North‐Western Mediterranean Sea. Here, we synergistically combine autonomous observations from BioGeoChemical‐Argo floats, satellite‐based and marine ecosystem model data, and show that MHW events occurring during winter drastically inhibit phytoplankton carbon biomass in spring by up to 70%. Such reduction is related to the enhanced stratification of the water column under MHWs which hinders the renewal of nutrients from deep‐ocean reservoirs, thus preventing surface phytoplankton from blooming. This process negatively impacts particulate organic carbon stocks within the mixed layer, while severe events cause an earlier shift of phytoplankton phenology that provokes changes in zooplankton biomass distribution. Plain Language Summary: Marine heatwaves (MHWs) are described as an abnormal and prolonged increase of ocean temperatures. These events may occur in all the oceans, and are becoming more frequent than before. Such increase in water temperature might not be tolerated by organisms, which must need to adapt themselves to the new environmental conditions. Consequently, marine ecosystem health is endangered. Here, we analyze the effect that MHWs have on the growth of small algae called phytoplankton. Phytoplankton are vital microscopic organisms for ecosystems that use sunlight to produce organic carbon through photosynthesis. At middle and high latitudes, phytoplankton massively grows (i.e., blooms) once a year at the sea surface, and introduces a major carbon flux into the ecosystem that sustains larger animals. Through combining observations acquired by different platforms (satellites, autonomous in situ BioGeoChemical‐Argo robots, and ecosystem models), we comprehensively study how MHWs affect phytoplankton carbon production during spring blooms and trophic chains at mid‐latitudes. Results show that MHW events occurring in winter lead to a large decrease in phytoplankton carbon biomass (up to 70%) in spring. Winter MHW events, driven by local atmospheric conditions, intensify water column stratification thus hindering the deep‐ocean nutrient transport to the surface, which is essential for phytoplankton to bloom. Key Points: Marine heatwaves (MHWs) intensify water stratification leading to reduction in nutrient supply which inhibits surface phytoplankton spring bloomMHWs lead to a phytoplankton community shift toward smaller cells, while increasing the transparency of surface watersMHWs decrease carbon stocks within the mixed layer, while intense ones shift phytoplankton phenology and affect zooplankton [ABSTRACT FROM AUTHOR]

Bioturbation (sediment disturbance by animal actions) effects on nutrient cycling and nutrient levels in surface waters are difficult to quantify, in part because the diversity and magnitude of species‐specific influences are poorly understood. These influences may have consequences for the management of the trophic state of freshwater ecosystems. Fish cause bioturbation in freshwater and marine ecosystems by digging in benthic sediments, manipulating periphyton mats while searching for prey and scraping hard substrates while feeding. We used experimental enclosures (2.25 m2) to quantify bioturbation‐mediated phosphorus (P) and nitrogen (N) regeneration from sediment by three species of fish that differ in interactions with the benthos (largemouth bass, Micropterus salmoides; tilapia, Oreochromis spp.; and sailfin catfish, Pterogoplichthys spp.) in shallow eutrophic wetlands in Southern Florida. Tilapia are omnivores that include detritus in their diet (winnowing or ingesting sediments) and dig nests in soft sediments year round, sailfin catfish actively burrow into substrate and consume detritus (digging and ingesting sediments), and largemouth bass are piscivores that do not routinely interact with the benthos when feeding but may dig nests in soft sediment in spawning season (January–April). We quantified the amount of suspended flocculent organic matter and changes in water column nutrients (total phosphorus [TP] and total nitrogen [TN]) in 2‐week trials for each species and estimated the portion of nutrient increases relative to fishless controls that could be attributed to bioturbation‐mediated internal nutrient loading through suspension of organic matter (as opposed to excretion or other sources of nutrient loading). Water column nutrient concentrations increased with increasing biomass for all species, but the bioturbation contribution differed by species. Largemouth bass increased water column nutrient concentrations (TP: 86% and TN: 5% relative to controls) but did not influence water column suspended particulate matter through bioturbation of sediment. Tilapia increased water column nutrients a modest amount (TP: 8%; TN: 15%), of which a small portion was attributed to bioturbation (c. 18% of TP). Sailfin catfish raised water column nutrients substantially (TP: 105%; TN: 46%) and up to 100% of the increased TP was attributed to bioturbation. Sailfin catfish also suppressed algal growth and TP accumulation on the sides of the enclosures and reduced nutrient concentrations of the flocculent sediments. Our results were consistent with our hypothesis that behaviour and foraging traits affect bioturbation contributions to nutrient loading. The results also demonstrated that species with similar net effects like largemouth bass and sailfin catfish, added nutrients via different mechanisms (i.e. excretion vs. bioturbation). Considering the feeding strategies and interactions with the substrate of common fish species may assist managers in meeting nutrient reduction goals for eutrophic wetlands and managed freshwater systems. [ABSTRACT FROM AUTHOR]

Sexual coral propagation faces a significant bottleneck due to high post‐settlement mortality, impeding large‐scale reef restoration. This study assessed the effectiveness of co‐culturing Diploria labyrinthiformis settlers with the herbivorous gastropod Cerithium lutosum and supplementing their diet with a commercially available food source, Reef‐Roids, to enhance settler survival and growth. Settlers were reared for 10 weeks under controlled conditions in one of four treatments: Control (C), Feeding with Reef‐Roids (F), Grazing by C. lutosum (G), and combined Feeding + Grazing (FG). Settlers in the Grazing treatment exhibited the highest survival at 87% after 10 weeks, significantly outperforming those in the Control (43%) and Feeding (48%) treatments. The combined feeding and grazing treatment improved survival rates to 74% and resulted in the highest growth rates, with settlers in this group averaging 11.98 ± 2.38 mm2, approximately 3.4‐fold larger than the control and 2.6‐fold larger than the feeding group. The feeding treatment alone did not significantly enhance survival or growth, underscoring the critical role of grazing in mitigating algal competition and promoting settler development. The results highlight the efficacy of grazing by C. lutosum (G and FG) in improving both survival and growth of coral settlers, substantially surpassing the outcomes of ungrazed treatments (F and C). This study highlights the potential of integrating microherbivores, such as C. lutosum, in ex situ coral nurseries. By regulating algal growth, these grazers minimize the need for labor‐intensive maintenance, offering a scalable and cost‐effective strategy to mitigate the high mortality rates of coral settlers. [ABSTRACT FROM AUTHOR]

Biodeterioration is a significant problem in the conservation of stone heritage buildings. In this study, 10 plant essential oils were assessed for their effectiveness in biofilm inhibition on stone heritage building surfaces under laboratory and in situ conditions, and were compared with traditional biocides such as benzalkonium chloride. The plant extracts were tested against algae and mosses. The effect on algae removal was evaluated by measuring the color of the surface before treatment, after 24 h and after 1 month of treatment. The effect on mosses was assessed by measuring the photosynthetic pigment content of mosses after 24 h of treatment. The results showed that the different plant extracts exhibited different levels of antibiotic activity. Benzalkonium chloride, S. aromaticum and C. cassia extracts showed strong antibiotic activity against all algae and mosses tested. T. mongolicus extracts showed antibiotic activity against only some of the algae and mosses, while the application of P. cablin extracts increased chlorophyll b content in the mosses. The other plant extracts were less effective at inhibiting the growth of algae and mosses. GC–MS compositional analysis further indicated that the higher antibiotic activity of S. aromaticum and C. cassia extracts was related to the high content of eugenol and cinnamaldehyde. [ABSTRACT FROM AUTHOR]

For fish oil-free aquafeed development, a photoautotrophic microalga Tisochrysis lutea is believed to be the candidate source of n-3 highly unsaturated fatty acid (n-3 HUFA) because of its docosahexaenoic acid (DHA) biosynthesis. While DHA contents of T. lutea vary during the cultivation periods depending on algal growth phase, little is mentioned about how this dependence should be taken into consideration when evaluating the suitability of microalgae as an alternative to fish oil-formulated diets. Here, we compared nutritionally maximized cells of deceleration growth phase T. lutea and fish oils-formulated product (n-3 HUFA-enriched Chlorella) as a rotifer enrichment diet for enhancement in Japanese flounder Paralichthys olivaceus larviculture. T. lutea had higher concentrations of DHA in the polar lipids than those for enriched Chlorella. Such higher concentrations of T. lutea were estimated only in the deceleration growth phase (not in the logarithmic growth or stationary phase). When deceleration growth phase T. lutea were fed to Brachionus plicatilis rotifers previously cultured on unenriched Chlorella, the DHA of the rotifers was boosted up to the level in those fed with enriched Chlorella. Furthermore, use of T. lutea-fed rotifers for initial feeding of fish larvae enhanced the growth, survival, n-3 HUFA levels, and final juvenile productivity of the larvae as much as feeding the larvae with enriched Chlorella-fed rotifers. We propose that T. lutea in the deceleration growth phase are efficacious, fish oil-free sources of n-3 HUFA for marine fish larviculture. Highlights: Polar lipid DHA % was high in the deceleration growth phase of Tisochrysis lutea. DHA % was high in rotifers fed either T. lutea or fish oil-enriched Chlorella. Rotifers enriched with T. lutea improved marine fish larviculture performance. [ABSTRACT FROM AUTHOR]

Introduction: Glacier ice algae, mainly Ancylonema alaskanum and Ancylonema nordenskiöldi, bloom on Greenland Ice Sheet bare ice surfaces. They significantly decrease surface albedo due to their purple-brown pigmentation, thus increasing melt. Little is known about their metabolic adaptation and factors controlling algal growth dynamics and pigment formation. A challenge in obtaining such data is the necessity of melting samples, which delays preservation and introduces bias to metabolomic analysis. There is a need to evaluate the physiological response of algae to melting and establish consistent sample processing strategies for metabolomics of ice microbial communities. Objectives: To address the impact of sample melting procedure on metabolic characterization and establish a processing and analytical workflow for endometabolic profiling of glacier ice algae. Methods: We employed untargeted, high-resolution mass spectrometry and tested the effect of sample melt temperature (10, 15, 20 °C) and processing delay (up to 49 h) on the metabolome and lipidome, and complemented this approach with cell counts (FlowCam), photophysiological analysis (PAM) and diversity characterization. Results and Conclusion: We putatively identified 804 metabolites, with glycerolipids, glycerophospholipids and fatty acyls being the most prominent superclasses (> 50% of identified metabolites). Among the polar metabolome, carbohydrates and amino acid-derivatives were the most abundant. We show that 8% of the metabolome is affected by melt duration, with a pronounced decrease in betaine membrane lipids and pigment precursors, and an increase in phospholipids. Controlled fast melting at 10 °C resulted in the highest consistency, and is our recommendation for future supraglacial metabolomics studies. [ABSTRACT FROM AUTHOR]

Innovative powder coating system for hydraulic steel construction Unprotected steel corrodes in the atmosphere, water and soil. In order to ensure structural safety and maintain fatigue strength, steel structures of all kinds must be protected from corrosion. Hydraulic steel structures such as locks, gates, canal bridges, ship lifts and water power plants largely characterize our waterways, coastal fortifications and port facilities. They are exposed to a particularly high level of corrosive attack because, in addition to atmospheric influences such as wind and weather, they are particularly affected by water, constant water changes and aggressive substances such as salts and minerals. Since such constructions and buildings usually represent investments of the century, their preservation, use and operational safety over generations is an economic necessity. But it′s not just corrosion that poses a problem for hydraulic steel construction; the formation of biofilms and the growth of algae and mussels can also lead to problems that can even lead to a restriction in the functionality of the systems. The newly developed powder coating system prevents both and thus helps to extend maintenance intervals, increase the lifecycle of steel components in hydraulic steel construction and reduces the lifecycle costs. The new powder coating system thus makes an innovative and sustainable contribution to the preservation of structures in hydraulic steel construction. [ABSTRACT FROM AUTHOR]

Aim Ammonium chloride (NH4Cl) is one of the nitrogen sources for microalgal cultivation. An excessive amounts of NH4Cl are toxic for microalgae. However, combining mixotrophic conditions and excessive quantities of NH4Cl positively affects microalgal biomass and lipid production. In this study, we investigated the impact of NH4Cl on the growth, biomass, and triglyceride (TAG) content of the green microalga Chlamydomonas reinhardtii especially under mixotrophic conditions. Methods and results Under photoautotrophic conditions (without organic carbon supplementation), adding 25 mM NH4Cl had no significant effect on microalgal growth or TAG content. However, under mixotrophic condition (with acetate supplementation), NH4Cl interfered with microalgal growth while inducing TAG content. To explore these effects further, we conducted a two-step cultivation process and found that NH4Cl reduced microalgal growth, but induced total lipid and TAG content, especially after 4-day cultivation. The photosynthesis performances showed that NH4Cl completely inhibited oxygen evolution on day 4. However, NH4Cl slightly reduced the F v/ F m ratio indicating that the NH4Cl supplementation directly affects microalgal photosynthesis. To investigate the TAG induction effect by NH4Cl, we compared the protein expression profiles of microalgae grown mixotrophically with and without 25 mM NH4Cl using a proteomics approach. This analysis identified 1782 proteins, with putative acetate uptake transporter GFY5 and acyl-coenzyme A oxidase being overexpressed in the NH4Cl-treated group. Conclusion These findings suggested that NH4Cl supplementation may stimulate acetate utilization and fatty acid synthesis pathways in microalgae cells. Our study indicated that NH4Cl supplementation can induce microalgal biomass and lipid production, particularly when combined with mixotrophic conditions. [ABSTRACT FROM AUTHOR]