Algal Growth Research Articles

Effects of CO2 Aeration and Light Supply on the Growth and Lipid Production of a Locally Isolated Microalga, Chlorella variabilis RSM09

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.

Geology of Mudstones Atop the Sangonghe Formation, Shuixigou Group, Turpan‐Hami Basin: New Insights and Their Implications for Petroleum Geology

ABSTRACTAs 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.

Zirconium-Modified Attapulgite Composite for Phosphorus Removal and Algae Control in Lake Water

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.

Exploring the potential of native sea urchins as ex situ coral propagation allies

Caribbean coral reefs face unprecedented decline due to anthropogenic and environmental stressors, necessitating active restoration efforts. Among the strategies to conserve and restore reef ecosystems, land‐based sexual propagation of corals is crucial for preserving genetic diversity and population resilience. This study explores the efficacy of utilizing native sea urchin herbivory to control benthic macroalgal proliferation and enhance coral growth in land‐based propagation systems. Three captive‐reared urchin species—Lytechinus variegatus, Tripneustes ventricosus, and Diadema antillarum—were evaluated for their influence on algal cover and growth of sexually propagated brain coral Pseudodiploria strigosa. Juveniles of each urchin species were co‐cultured with 6‐month‐old coral colonies over a 105‐day experiment. Results indicated that all urchin treatments effectively reduced algal cover compared to controls; however, only T. ventricosus significantly increased coral growth rate, while the other urchin species did not have a notable effect. Despite differences in growth, coral survival was consistently high across all treatments. Benthic community analysis revealed shifts in algal composition, with D. antillarum grazing associated with increased crustose coralline algae. However, overgrazing by D. antillarum may have resulted in mild peripheral tissue damage to some corals. Urchin survival remained high, suggesting potential for downstream utilization in restoration (e.g. urchin population enhancement). This study highlights the potential of native urchins as biocontrol agents in coral propagation, emphasizing the importance of species‐specific interactions in shaping benthic communities and promoting coral resilience.

Variations of phosphorus in sediments and suspended particulate matter of a typical mesotrophic plateau lake and their contribution to eutrophication

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.

A multi-dimensional comparative study on the performance of algae removal using various flotation

Flotation is considered the most cost-effective and efficient algae-water separation technology. However, there are various flotation techniques for algae removal, such as coagulation-flotation (CF), foam flotation (FF), and positively charged bubble flotation (PF). It remains unclear which method is most suitable for removing algae from water bodies and under what specific conditions each technique is most effective. This study systematically compares CF, FF, and PF in terms of algal cell removal efficiency, concentration ratio, flotation kinetics, impact on algal cells, removal efficiency of algal organic matter (AOM) and microcystins (MC-LR), as well as economic cost analysis. CF is better suited for algae removal in water bodies, including drinking water sources, using fixed installations on shore due to its high removal efficiency, high concentration ratio, low chemical dosage, and minimal residuals. FF is more appropriate for non-drinking water sources as it can remove algae and further control algal growth; however, its residual CTAB may pose a threat to drinking water safety. PF is most suitable for in situ algae removal within water bodies, primarily because it does not require stirring or coagulation. Instead, modified bubbles can be directly introduced into the algal distribution layer, where they adhere to algal cells, facilitating algae-water separation. All three flotation methods are economically feasible for algae removal. For FF, the costs of chemicals and electricity are nearly equal, while for CF and PF, the primary cost is electricity. This study provides data to support the selection of appropriate flotation technologies for emergency removal of algal blooms in water bodies.

Enhancing Aquaculture Productivity through Integrated Farming Systems: A Comparative Study of Fish-Pig and Fish-Duck Systems

Integrated farming systems involving fish-animal are of high relevance in current scenario. Studies like this asses the suitability of such systems in improving the aquaculture productivity and overall benefits to the ecosystem. It plays a crucial role in optimizing the use of small water resources in rural areas to enhance animal production. Given the potential of pig and duck manure as nutrient inputs in fish culture, a grow-out trial was conducted in a 0.1 ha earthen pond located in Elangitampatty, Kezhisenkattupatti, and Asakkattuppatti villages of Kollihills Taluk in Namakkal district, Tamil Nadu. The pond was stocked with four carp species: Catla, Rohu, Mrigal, and Grass carp in a ratio of 40:20:30:10 at a density of 7500 fish per hectare. Three treatments were employed: (1) Control (T0), where fish were fed with commercial feed, (2) Integrated fish-duck farming (T1), and (3) Integrated pig-fish farming (T2). In the control group (T0), fish were fed commercial fish feed (24% crude protein, 4 mm pellet size) at 4% of body weight, while in T1 and T2, fish received 50% of the commercial feed and were supplemented with duck and pig excreta, respectively. After an 8-month grow-out period, fish weights and total production in each group were recorded. Water quality parameters, such as pH, dissolved oxygen, free carbon dioxide, alkalinity, and hardness, were measured using standard methods (APHA, 2019). Results showed that pond fertilization with pig and duck excreta promoted the growth of algae, phytoplankton, and zooplankton, providing a natural food source for the fish. Total fish production was highest in the fish-pig integration system (T2), with a recorded yield of 4960.09 kg. Catla (Catla catla) had the highest individual species yield, with a total harvested weight of 2225.98 kg, followed by Grass carp (Ctenopharyngodon idella) at 1490.37 kg. The final average weight of Grass carp in T0, T1, and T2 was 1047 ± 13.27 g, 1151.10 ± 12.85 g, and 1490.37 ± 13.52 g, respectively. For Catla, the final average weight in T0, T1, and T2 was 910 ± 9.45 g, 960 ± 10.26 g, and 980 ± 12.20 g, respectively. Similarly, Rohu in T0, T1, and T2 weighed 850 ± 7.98 g, 900 ± 11.23 g, and 910 ± 11.16 g, respectively, while Mrigal in T0, T1, and T2 weighed 600 ± 6.04 g, 720 ± 8.50 g, and 730 ± 10.56 g, respectively. The results highlight that the fish-pig system outperformed the fish-duck system in terms of fish productivity, which may be due to the better nutrient composition in pig manure and the genetic potential of the fish species. An economic analysis revealed that the fish-pig integration system generated the highest net income (Rs. 555,353.90) and benefit-cost ratio (2.12), indicating that integrated fish-pig farming is more profitable than both fish-duck farming and the control group without integration.

Linking fish bioturbation to life history in a eutrophic wetland: An analysis of fish contributions to internal nutrient loading

Abstract 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.

Linking land use and precipitation changes to water quality changes in Lake Victoria using earth observation data

Due to the continued increase in land use changes and changing climatic patterns in the Lake Victoria basin, understanding the impacts of these changes on the water quality of Lake Victoria is imperative for safeguarding the integrity of the freshwater ecosystem. Thus, we analyzed spatial and temporal patterns of land cover, precipitation, and water quality changes in the Lake Victoria basin between 2000 and 2022 using global satellite products. Focusing on chlorophyll-a (Chl-a) and turbidity (TUR) in Lake Victoria, we used statistical metrics (correlation coefficient, trend analysis, change budget, and intensity analysis) to understand the relationship between land use and precipitation changes in the basin with changes in Chl-a and TUR at two major pollution hotspots on the lake, i.e., Winam Gulf and Inner Murchison Bay (IMB). Results show that the Chl-a and TUR concentrations in the Winam gulf increase with increases in precipitation. Through increases in precipitation, the erosion risks are increased and transport of nutrients from land to the lake system, promoting algal growth and turbidity. In the IMB, Chl-a and TUR concentrations decrease with an increase in precipitation, possibly due to dilution, but peak during moderate rainfall. Interestingly, changes in land use and land cover (LULC) at 5-year intervals showed no substantial correlation with water quality changes at selected hotspots even though a broader LULC change analysis over the past two decades indicated a notable 300% increase in built-up areas across the Lake Victoria basin. These findings underscore the dominant influence of precipitation changes over LULC changes on the water quality of Lake Victoria for the selected hotspot areas.

Seasonal Variations in the Thermal Stratification Responses and Water Quality of the Paldang Lake

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.

Valorization of abattoir water discharge through phycoremediation for enhanced biomass and biodiesel production

Phycoremediation has been discussed as a multipurpose strategy to refine various waste streams for sustainable algal biomass, value-added compounds, and biodiesel production. While phycoremediation has been explored for various wastewaters, there is still a research gap in systematical understanding the impact of abattoir water discharge (AWD) on both algal growth and biodiesel quality. The present study evaluated the potential of Chlorella sorokiniana to grow at different ratios of AWD, 30–90 %, v/v with conventional growth medium. Results showed that nutrient removal efficiency after 12 days of cultivation reached up to 85 % for total nitrogen, 78 % for total phosphorus, 70 % for potassium, and 65 % for sodium. Thus, all algae-treated AWD samples showed Kelly ratio (KR) values less than 1, confirming their suitability for direct application in soil irrigation. In addition, there were insignificant variations in algal growth and biomass yield across all treatments. Interestingly, carotenoids yield showed significant increase in all AWD ratios, with the highest recorded value of 0.750 mg L−1 at day 12 using 90 % AWD, compared to 0.523 mg L−1 in the control. Among various treatments, C. sorokiniana grown in 90 % AWD exhibited the highest lipid content of 201.6 mg g−1 algal dw (comparing to 180.6 mg g−1 dw in the control). The biodiesel derived from C. sorokiniana at different AWD ratios demonstrated promising characteristics due to enhancement of saturated fatty acids proportion, which resulted in lower iodine value, longer oxidation stability, and higher cetane number than the control.

Eutrophication and Dissolved Organic Matter Exacerbate the Diel Discrepancy of CO2 Emissions in China's Largest Urban Lake.

The large variability in the emissions of carbon dioxide (CO2) from urban lakes remains a challenge for partitioning these sources at meaningful spatial and temporal scales. Dissolved organic matter (DOM) governs the spatial and temporal variations in CO2, yet relationships of the CO2 concentration (cCO2) and emission flux (FCO2) with DOM in urban lakes have rarely been reported. In this study, we monitored levels of cCO2, FCO2, and the composition of DOM over a 24 h period at three sites during the dry and wet seasons in China's largest urban lake, Tangxun Lake. Our study found the ratio of day/night FCO2 (millimoles per square meter per day) decreased from the dry season (0.79; 7.68/9.68) to the wet season (0.25; 6.05/24.16), averaging 0.42 (6.77/15.97), implying that accounting for nighttime CO2 emissions can increase regional estimates by 70%. This study revealed that eutrophication affected diurnal CO2 emissions with greater algal growth enhancing daytime CO2 uptake and subsequently increasing nighttime CO2 emissions via DOM degradation (larger protein-like DOM fraction). We anticipate that the relative magnitude of FCO2 between day and night from lakes is likely to increase due to urbanization and climate change, underscoring the importance of treating urban lakes as a distinct group and integrating DOM dynamics into carbon cycling in future research.

Isolation, Identification and Characterization of the Algicidal Micromycete Penicillium chrysogenum SR–1.3

A novel strain SR–1.3 with algicidal properties and the ability to remove microcystin-LR was isolated from the water of Lake Sestroretskij Razliv during the active cyanobacteria vegetation. Based on the morphological and cultural characteristics and the results of sequencing of the ITS DNA region strain SR–1.3 was identified as Penicillium chrysogenum. The SR–1.3 strain exhibited algicidal activity against cyanobacteria and green algae. A dose-dependent and species-specific nature of the algicidal action of the P. chrysogenum SR–1.3 strain has been established. Cyanobacteria showed the highest sensitivity to strain SR–1.3. The complete lysis (100%) of cyanobacteria cells was observed when 10% (vol.) of the culture liquid or the micromycete filtrate were added to the medium. The algicidal effect of strain SR–1.3 on green algae was 30–70%, depending on the culture. According to the level of sensitivity to the algicidal effect SR–1.3, the test cultures can be arranged in the series Planktothrix agardhii Microcystis aeruginosa Aphanizomenon flos-aquae = Anabaena cylindrica Scenedesmus quadricauda Oocystis parva. The inhibitory effect of the strain SR-1.3 mycelium on the cyanobacteria and green algae growth did not exceed 3–6%. Based on the obtained results a conclusion was made about the indirect mechanism of the algicidal action of P. chrysogenum SR–1.3 by excretion into the medium of metabolites that inhibit and/or lyse cells of cyanobacteria and green algae. When toxigenic strains of M. aeruginosa and P. agardhii were cultivated on a medium containing exometabolites of strain SR–1.3, the concentrations of microcystins in the medium decreased by 3.3 and 1.8 times, respectively, compared with control variants. The ability of P. chrysogenum SR–1.3 to remove highly toxic microcystin-LR from the cultivation medium was revealed. The MC-LR content was found to decrease from 1.2 μg/ml to 0.79 μg/ml over 48 hours during the cultivation of strain SR–1.3 on medium with microcystin.

Treating liquid anaerobic digestate using natural zeolite and Arthrospira platensis cyanobacteria: From laboratory to pilot-scale

Over the past decade, using liquid digestate as a nutrient source for microalgae cultivation has gained considerable attention. However, its high ammonium concentration and turbidity often inhibit algal growth. To address this, natural zeolite was explored as a novel approach to reduce digestate toxicity before microalgae cultivation at both laboratory and pilot-scales. Clinoptilolite, a type of natural zeolite, was applied in adsorption columns at a ratio of 0.5 kgzeolite.L-1 to treat 0.45 L of liquid digestate. After 24 h of treatment, ammonium levels decreased significantly from 2273 to 115 mgN.L-1, corresponding to a 95 % removal efficiency and an adsorption capacity of 4.31 mg.gzeolite-1. Arthrospira platensis demonstrated strong growth in the treated digestate with minimal dilution (≤5x), in contrast to the high dilution (≥20x) required for the untreated digestate. Laboratory-scale results were effectively scaled up to pilot scale, detoxifying 15.5 L of digestate with similar performances. The pretreated digestate was subsequently used as a culture medium for Arthrospira platensis in flat panel photobioreactors without further dilution, achieving a final concentration of 0.82 gDW.L-1 and a biomass productivity of 33 mg.L-1.d-1. These findings underscore the potential of natural zeolite in enhancing microalgae-based processes for digestate detoxification and CO2 mitigation.

Algal Growth and Morphogenesis-Promoting Factors Released by Cold-Adapted Bacteria Contribute to the Resilience and Morphogenesis of the Seaweed Ulva (Chlorophyta) in Antarctica (Potter Cove)

AbstractMacroalgae are found in a variety of marine vegetation ecosystems around the world, contributing significantly to global net primary production. In particular, the sea lettuce species, i.e., members of the genus Ulva (Chlorophyta), are located in many ecological niches and are characterized by excellent adaptability to environmental changes but depend on essential associated bacteria, which release algal growth and morphogenesis-promoting-factors (AGMPFs). Our work investigated the hypothesis that bacteria need to be stress-adapted to provide sufficient amounts of AGMPFs for the growth and morphogenesis of Ulva throughout its life cycle, even under severe environmental conditions. Our study thus aimed to understand which bacteria contribute to overcoming a variety of stressors in polar regions. Green macroalgae were collected from Potter Cove, King George Island (Isla 25 de Mayo), Antarctica, to study the associated microbiome and, subsequently, to identify AGMPFs releasing bacteria. Therefore, microbiome analysis was combined with morphogenetic bioassays and chemical analysis, identifying bacteria essential for algal growth under Antarctic conditions. Hereby, axenic cultures of Ulva compressa (cultivar Ulva mutabilis, Ria Formosa, Portugal), previously developed as a model system for bacteria-induced algal growth and morphogenesis, were inoculated with freshly isolated and cultivable Antarctic bacteria to determine their morphogenetic activity. The exploratory microbiome investigation identified numerous cold-adapted AGMPF-producing bacteria. Unlike the temperate-adapted bacterial strains originally isolated from the U.mutabilis holobiont, the cold-adapted isolates Maribacter sp. BPC-D8 and Sulfitobacter sp. BPC-C4 released sufficient amounts of AGMPFs, such as thallusin and still unknown compounds, necessary for the morphogenesis of the Antarctic Ulva even at 2 °C. Our results illustrate the role of chemical mediators provided by bacteria in cross-kingdom interactions under cold conditions within aquatic systems. The newly isolated bacteria will enable further functional studies to understand the resilience of the holobiont Ulva and might be applied in algal aquaculture even under adverse conditions. The study highlights the importance of eco-physiological assays in microbiome analysis.

The Effect of Polyethylene Microplastics on Growth and Antioxydant Response of Oscillatoria Princeps and Chlorella Pyrenoidosa.

This study investigated the impacts of polyethylene microplastics (PE-MPs) with varying particle sizes (13μm and 6.5μm) on the growth and antioxidant responses of two freshwater algae species, Oscillatoria princeps (O. princeps) and Chlorella pyrenoidosa (C. pyrenoidosa). The results revealed a significant reduction in chlorophyll a content in both algal species upon exposure to PE-MPs, indicating a disruption of photosynthesis. Furthermore, Superoxide Dismutase (SOD) activity decreased in O. princeps, while Catalase (CAT) activity increased in both species, indicating complex physiological responses to microplastic stress. Notably, phycotoxin levels in O. princeps decreased with PE-MP exposure, while those in C. pyrenoidosa increased, particularly with 6.5μm PE-MPs. These findings underscore the potential toxic effects of PE-MPs on freshwater algal growth and metabolism, as well as their influence on toxin production. This study contributes valuable insights into the ecotoxicological impacts of microplastics in freshwater environments, highlighting the need for further research on their biological effects and environmental health implications.

Green slag cement with nano copper oxide and nano silica: Enhanced antimicrobial and structural properties

The global construction industry is facing challenges related to sustainability, environmental impact, and the demand for innovative materials with multifunctional properties. A major concern is the durability of cement structures, which is often compromised by harmful bacteria and algae. These microorganisms accelerate the deterioration of structures, increase maintenance costs, and pose safety risks. Addressing these issues is essential to prolong the life of cement-based structures and reduce their environmental and carbon footprint. Cement in moist environments is particularly vulnerable to microbial growth, leading to structural weaknesses and degradation. This degradation necessitates costly repairs, shortens the lifespan of infrastructure, creates a threat to human lives, and contributes to increased carbon emissions. To tackle these challenges, researchers have tried to develop low-carbon cement ((green cement) with antimicrobial properties. Nanomaterials like nano-copper oxide (nCuO) and nano-silica (nSiO₂) have shown great potential in enhancing both the structural performance and microbial resistance of green cement. When nanomaterials, nCuO is incorporated into Portland slag cement (PSC), which already has a lower carbon footprint compared to traditional cement, enhances antibacterial and antialgal properties but adversely impacts the mechanical performance and to counter the adverse effect of nCuO, nSiO2 added to improve the mechanic performance. PSC is known for its ability to reduce industrial waste and CO₂ emissions, and the addition of nCuO and nSiO₂ makes it an even higher-performance material. Effects of nCuO and nSiO₂ on PSC have been studied by using isothermal calorimetry to assess hydration kinetics, X-ray diffraction to observe composition changes during hydration, scanning electron microscopy (SEM) to analyze microstructural changes, and mechanical testing to evaluate the strength of the material. The effectiveness of antimicrobial properties is studied in lab and field experiments. The results revealed improved compressive strength and significant resistance to bacterial and algal growth. The combination of nCuO's antimicrobial properties and nSiO₂'s ability to enhance the cement's strength created a synergistic effect that optimizes both performance and durability. Additionally, the study proposed a model to better understand the interaction between these nanomaterials, offering valuable insights into the mechanisms of hydration and microbial inhibition.

Synergistic management of nitrogen contamination in overflow wastewater and algal proliferation in lake receiving wastewater based on electrochemical oxidation process

Urban lake eutrophication, largely driven by overflow wastewater, plays a pivotal role in precipitating algal proliferation due to heightened nitrogen levels in aquatic ecosystem. In addressing this question, this study investigated the chloride-mediated electrochemical oxidation system as a promising solution for controlling nitrogen contamination in overflow wastewater and inhibiting algal proliferation in wastewater-receiving urban lakes, and also evaluated the influence of essential operational parameters on the performance of system. The results indicated that, under the environmental conditions set by this experiment, the removal efficiency ranges of ammonia nitrogen and total nitrogen were 14.91 % - 100 % and 13.98 % - 99.62 %, respectively; meanwhile, the maximum algae inhibition rate could reach 100 % at a capacity ratio of 0.01. Response Surface Method analysis highlighted current density as the preeminent factor in nitrogen removal and algae inhibition, surpassing the influence of initial chloride ion and nitrogen concentrations within the system. Notably, an excessive current density could inadvertently lead to the nitrate nitrogen accumulation (up to 29 %), thereby diminishing the total nitrogen removal efficiency, particularly in low nitrogen-concentrated overflow wastewater scenarios. With respect to algae inhibition, a direct correlation was identified between higher residual total chlorine concentrations in the receiving lake and increased algae inhibition rates (R = 0.90, P < 0.05), and the residual total chlorine was found to exert pronounced inhibition on cyanobacteria compared to other algal forms. However, caution was advised regarding potential algal growth stimulation if the initial received total chlorine concentration in the urban lake receiving wastewater below 0.5 mg/L. These findings not only affirm the feasibility of this synergistic approach but also elucidate critical aspects for process optimization and control.

A multi-disciplinary approach based on chemical characterization of foreshore sediments, ecotoxicity assessment and statistical analyses for environmental monitoring of marine-coastal areas

The present work aims at providing a multi-disciplinary approach for environmental monitoring in marine-coastal areas. A monitoring campaign of 13 months (October 2022–October 2023) was carried out on sandy foreshore sediments (SFSs). The SFSs were analysed for potentially toxic elements (PTEs) and rare earth elements (REEs) content determination. In the investigated area, variable contamination trends were assessed through Friedman and Nemenyi tests. Further results also indicated the usefulness of statistical data elaboration in the identification of potential contamination sources. In fact, from Spearman test, significant positive correlations (between 0.650 and 0.981) were observed among PTEs of possible anthropogenic origin (such as Co, Cr, Cu, Pb, V, and Zn). For REEs, La and Nd showed strong correlations with Ce (0.909 and 0.920, respectively). The study also integrated luminescence inhibition (Aliivibrio fischeri), algal growth inhibition (Phaeodactylum tricornutum), and embryotoxicity assessment (Paracentrotus lividus) on sediment elutriates showing varying degrees of toxicity. Also these data were analysed through statistics in order to highlight possible correlations between contaminants and observed ecotoxicological effects on the involved bioindicators. The results outline an approach useful for more comprehensive monitoring of marine areas quality and identification of suitable environmental restoration strategies.

Integrating grazing and food supplementation in coral restoration to enhance settler survival and growth

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.