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Microplastics and nanoplastics pose a severe threat to organisms and the environment. Algae are important primary producers in aquatic ecosystems, providing nutrients for a wide range of species, so the toxic effects of pollutants on algae have negative effects on organisms at higher trophic levels. The toxic effects of micro/nanoplastics (MNPs) on algae have been the subject of many studies, with varying conclusions due to differences in experimental design. Thus, the objective of this review is to summarize the effects of MNPs on algal populations considering algal growth, pigments, photosynthesis, and oxidative stress parameters. Moreover, we provide insight into how MNPs affect algae based on the current studies. Removing MNPs has been a much less popular research topic than describing the MNPs. Algae is a promising eco-friendly method to remove MNPs. Algae have many advantages over conventional methods. Microalgal cells adsorb MNPs and are used as a source of nutrients to regulate metabolic processes to produce biomass. Therefore, this review provides methods for removing MNPs using algae. This approach will promote the development of methods to remove MNPs and contribute towards sustainability for the development of an algal-based future. [ABSTRACT FROM AUTHOR]

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, asexual reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages since its discovery in 1981 offshore of Oʻahu, Hawai'i. Field observations suggest this species is spreading via vegetative reproduction. To characterize the reproductive system of A. lacerata in Hawai'i, we developed seven microsatellite loci and genotyped 321 blades collected between 2018 and 2023 from three intertidal sites at Maunalua Bay and ʻEwa Beach. We observed one to four alleles at multiple loci, suggesting A. lacerata is tetraploid. Each site was characterized by high genotypic richness (R > 0.8). However, clonal rates were also high, suggesting the vegetative spread of A. lacerata plays a significant role. The importance of clonal reproduction for the persistence of A. lacerata in Hawai'i is consistent with the ecological data collected for this species and observations of other abundant macroalgal invaders in Hawai'i and other regions of the world. These data demonstrate the necessity for implementing appropriate population genetic methods and provide insights into the biology of this alga that will contribute to future studies on effective management strategies incorporating its reproductive system. This study represents one of the few that investigate green algal population genetic patterns and contributes to our understanding of algal reproductive system evolution. [ABSTRACT FROM AUTHOR]

This work aimed to characterize the impact of copper (Cu), at environmentally relevant concentrations, using the freshwater microalga Raphidocelis subcapitata. Algae were incubated with 33 or 53 µg/L Cu, in OECD medium, and toxic impacts were evaluated over 72 h, using different cellular and biochemical biomarkers. The exposure to 33 µg/L Cu had an algistatic effect: slowing growth and reducing algal population (53%, at 72 h) without compromising the cell membrane. This Cu concentration promoted a transient reduction in chlorophyll a (chla) content and typical markers of oxidative stress: increased levels of reactive oxygen species (ROS), augmented catalase (CAT) activity, and lipid peroxidation (malondialdehyde, MDA). Algae exposed to 53 µg/L Cu, suffered a severe effect with a 93% reduction in the number of cells, 50% decrease in chla content, and diminished (17%) maximum photochemical quantum yield of PSII (Fv/Fm). This population also presented increased levels of ROS and MDA, 33 and 20 times higher than the control, respectively, at 72 h, augmented CAT activity, and permeabilized cell membrane (5%, at 72 h). These findings provide valuable insights into Cu toxicity in aquatic ecosystems, highlighting the biochemical and physiological impacts at environmentally relevant concentrations. [ABSTRACT FROM AUTHOR]

Due to rapid urbanization, population growth, industrialization, and agricultural activities, there is an increasing demand for freshwater resources, leading to heightened pressure on watershed ecosystems. This study focused on the Nishan Reservoir, Qufu Sihe River, and Qufu Yihe River, conducting field investigations on these water bodies during the spring of 2021 and 2022. Water samples were collected and analyzed for key water quality indicators, including chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (AN), chlorophyll A, and algal cell density. This study unveiled notable correlations among various water quality parameters, including positive associations between BOD and COD, chlorophyll A and algal cell density, and inverse relationships with total phosphorus. Moreover, significant positive correlations were identified between total nitrogen and ammonia nitrogen, as well as between ammonia nitrogen and chlorophyll A. The study highlighted that the TP concentration surpassed the threshold of 0.20 mg/L in 2021, potentially exacerbating the proliferation of algae, leading to algal blooms and adversely affecting the aquatic ecosystem. This study emphasizes the significance of broadening the geographical scope and utilizing long-term datasets to discern trends, determinants, and management approaches pertinent to water quality. Furthermore, this study underscores the imperative of investigating the influence of nitrogen-to-phosphorus nutrient ratios on the composition and proliferation of algal populations, while also taking into account the potential impact of additional factors like light availability, temperature, and water flow on the dynamics of algal communities. [ABSTRACT FROM AUTHOR]

Plankton parasites such as viruses, bacteria, fungi, and unicellular eukaryotes are associated symbionts colonizing algal groups in aquatic ecosystems. They occur within a network of microbe–microbe interactions in which they parasitize phytoplankton and seaweeds, i.e., primary producers generating organic carbon and forming the basis of marine food webs. These parasites use algae as a source of nutrients and reproduce at the expense of their host, causing infectious symptoms leading to disease and death. Plankton parasites can reduce the algal populations, and the infection of one specific species may, in turn, favor the development of another, influencing the seasonal succession of algal blooms in oceans, seas, and lakes. Many parasites have free-living stages that zooplankton graze upon, representing a significant trophic link in food webs. The biology and life cycle of plankton parasites are well investigated in marine and freshwater algal hosts. Still, the chemical signaling mediating these microbial interactions and the effect of co-occurring symbionts remain underexplored. This review focuses on the diversity of plankton parasites infecting algae, with a particular emphasis on unicellular eukaryotes. The ecological role of plankton parasites, the mechanisms regulating cellular infection and host resistance, and the interplay of alga-parasite interactions with coexisting microorganisms are discussed. [ABSTRACT FROM AUTHOR]

Interactions such as mutualism and facilitation are common in ecosystems established by foundation species; however, their outcomes vary and show conditionality. In a Mexican Caribbean Bay, a seagrass-coralline algae (rhodoliths) mutualism protects the seagrass Thalassia testudinum from green turtle overgrazing. We postulate that the state of the seagrass meadow in this bay depends on the strengths of the interactions among seagrasses, green turtles, and coralline algae. Spatio-temporal changes through satellite imagery showed rhodolith bed developed rapidly from 2009 (undetected) to 2016 (bed of 6934 m2). Typically, such rapid expansion of the rhodoliths does not occur in seagrass meadows. An in situ growth experiment of coralline algae showed that a combination of reduction in light and wave movement (usual in dense seagrass meadows) significantly reduced their growth rates. In the rhodolith beds, the growth rates of the coralline algae Neogoniolithon sp. and Amphiroa sp. were high at 9.5 mm and 15.5 mm per growth tip y−1, respectively. In a second experiment, we found lower mortality in coralline algae within a rhodolith bed compared to algae placed outside the bed, likely explained by the reduced resuspension that we found in a third experiment, and this positive feedback may explain the high population increase in the rhodoliths, once established when the turtles grazed down the seagrass canopy. Therefore, the grazing-protection mutualism between seagrasses and coralline algae is thus conditional and came into existence under a co-occurrence of intensive grazing pressure and rapid population growth of coralline algae facilitated by positive feedback from increased growth and reduced sediment resuspension by the dense rhodolith bed. [ABSTRACT FROM AUTHOR]

Sex is a crucial process that has molecular, genetic, cellular, organismal, and population‐level consequences for eukaryotic evolution. Eukaryotic life cycles are composed of alternating haploid and diploid phases but are constrained by the need to accommodate the phenotypes of these different phases. Critical gaps in our understanding of evolutionary drivers of the diversity in algae life cycles include how selection acts to stabilize and change features of the life cycle. Moreover, most eukaryotes are partially clonal, engaging in both sexual and asexual reproduction. Yet, our understanding of the variation in their reproductive systems is largely based on sexual reproduction in animals or angiosperms. The relative balance of sexual versus asexual reproduction not only controls but also is in turn controlled by standing genetic variability, thereby shaping evolutionary trajectories. Thus, we must quantitatively assess the consequences of the variation in life cycles on reproductive systems. Algae are a polyphyletic group spread across many of the major eukaryotic lineages, providing powerful models by which to resolve this knowledge gap. There is, however, an alarming lack of data about the population genetics of most algae and, therefore, the relative frequency of sexual versus asexual processes. For many algae, the occurrence of sexual reproduction is unknown, observations have been lost in overlooked papers, or data on population genetics do not yet exist. This greatly restricts our ability to forecast the consequences of climate change on algal populations inhabiting terrestrial, aquatic, and marine ecosystems. This perspective summarizes our extant knowledge and provides some future directions to pursue broadly across micro‐ and macroalgal species. [ABSTRACT FROM AUTHOR]

Diversity and its drivers and consequences are at the heart of ecological research. Mostly, studies have focused on different species, but if the causes for increases or decreases in diversity are general, the observed patterns should also be observable within genotypes. As previous research shows that there is higher variability in nitrogen to phosphorus ratios (N/P) between slow-growing unicellular algal populations, compared to fast-growing ones, we expected to observe similar patterns within genetically identical strains growing at different rates. We tested this hypothesis in a laboratory experiment performed with a monoculture of the diatom Phaeodactylum tricornutum. Using a growth rate gradient obtained with 10 chemostats, we were able to determine the effect of growth rate on the diatom's elemental stoichiometry as well as on selected traits, such as cell size and shape. Our results showed indeed less intercellular variability (in the selected traits assessed on single-cell level) in the faster-growing populations, which was accompanied by a downward trend in bulk N/P ratios. We pose that this higher variability at lower growth rates potentially results in higher variability of the food sources available for higher trophic levels with potential consequences for the transfer efficiency of energy and matter in marine food webs. [ABSTRACT FROM AUTHOR]

Background: Dark pigmented snow and glacier ice algae on glaciers and ice sheets contribute to accelerating melt. The biological controls on these algae, particularly the role of viruses, remain poorly understood. Giant viruses, classified under the nucleocytoplasmic large DNA viruses (NCLDV) supergroup (phylum Nucleocytoviricota), are diverse and globally distributed. NCLDVs are known to infect eukaryotic cells in marine and freshwater environments, providing a biological control on the algal population in these ecosystems. However, there is very limited information on the diversity and ecosystem function of NCLDVs in terrestrial icy habitats. Results: In this study, we investigate for the first time giant viruses and their host connections on ice and snow habitats, such as cryoconite, dark ice, ice core, red and green snow, and genomic assemblies of five cultivated Chlorophyta snow algae. Giant virus marker genes were present in almost all samples; the highest abundances were recovered from red snow and the snow algae genomic assemblies, followed by green snow and dark ice. The variety of active algae and protists in these GrIS habitats containing NCLDV marker genes suggests that infection can occur on a range of eukaryotic hosts. Metagenomic data from red and green snow contained evidence of giant virus metagenome-assembled genomes from the orders Imitervirales, Asfuvirales, and Algavirales. Conclusion: Our study highlights NCLDV family signatures in snow and ice samples from the Greenland ice sheet. Giant virus metagenome-assembled genomes (GVMAGs) were found in red snow samples, and related NCLDV marker genes were identified for the first time in snow algal culture genomic assemblies; implying a relationship between the NCLDVs and snow algae. Metatranscriptomic viral genes also aligned with metagenomic sequences, suggesting that NCLDVs are an active component of the microbial community and are potential "top-down" controls of the eukaryotic algal and protistan members. This study reveals the unprecedented presence of a diverse community of NCLDVs in a variety of glacial habitats dominated by algae. [ABSTRACT FROM AUTHOR]

Host–parasite interactions can cause strong demographic fluctuations accompanied by selective sweeps of resistance/infectivity alleles. Both demographic bottlenecks and frequent sweeps are expected to reduce the amount of segregating genetic variation and therefore might constrain adaptation during co‐evolution. Recent studies, however, suggest that the interaction of demographic and selective processes is a key component of co‐evolutionary dynamics and may rather positively affect levels of genetic diversity available for adaptation. Here, we provide direct experimental testing of this hypothesis by disentangling the effects of demography, selection and their interaction in an experimental host–parasite system. We grew 12 populations of a unicellular, asexually reproducing algae (Chlorella variabilis) that experienced either growth followed by constant population sizes (three populations), demographic fluctuations (three populations), selection induced by exposure to a virus (three populations), or demographic fluctuations together with virus‐induced selection (three populations). After 50 days (~50 generations), we conducted whole‐genome sequencing of each algal host population. We observed more genetic diversity in populations that jointly experienced selection and demographic fluctuations than in populations where these processes were experimentally separated. In addition, in those three populations that jointly experienced selection and demographic fluctuations, experimentally measured diversity exceeds expected values of diversity that account for the cultures' population sizes. Our results suggest that eco‐evolutionary feedbacks can positively affect genetic diversity and provide the necessary empirical measures to guide further improvements of theoretical models of adaptation during host–parasite co‐evolution. [ABSTRACT FROM AUTHOR]

Aquatic weeds, including invasive species, are a worldwide problem. The presence of aquatic weeds poses several critical issues, such as hindering the continuous flow of water in irrigation channels and preventing the proper distribution of adequate water quantities. Therefore, effective control measures are vital for agriculture and numerous downstream industries. Numerous methods for controlling aquatic weeds have emerged over time, with herbicide application being a widely used established method of weed management, although it imposes significant environmental risks. Therefore, it is important to explore nonchemical alternative methods to control existing and emerging aquatic weeds, potentially posing fewer environmental hazards compared with conventional chemical methods. In this review, we focus on nonchemical methods, encompassing mechanical, physical, biological, and other alternative approaches. We primarily evaluated the different nonchemical control methods discussed in this review based on two main criteria: (1) efficiency in alleviating aquatic weed problems in location-specified scenarios and (2) impacts on the environment, as well as potential health and safety risks. We compared the nonchemical treatments with the UV-C-radiation-mediated aquatic weed control method, which is considered a potential novel technique. Since there is limited published literature available on the application of UV-C radiation used exclusively for aquatic weed control, our review is based on previous reports of UV-C radiation used to successfully control terrestrial weeds and algal populations. In order to compare the mechanisms involved with nonchemical weed control methods, we reviewed respective pathways leading to plant cell death, plant growth inhibition, and diminishing reemergence to justify the potential use of UV-C treatment in aquatic habitats as a viable novel source for aquatic weed control. [ABSTRACT FROM AUTHOR]

Toxicological effects of silver nanoparticles (SNPs) in different organisms have been studied; however, interactions of SNPs with other environmental pollutants such as mercury are poorly understood. Herein, bioassay tests were performed according to ΟECD 201 guideline to assess the toxic effects induced by mercury ions (mercury chloride, MCl) on the marine microalga Chaetoceros muelleri in the presence of SNPs or silver ions (silver nitrate, SN). Acute toxicity tests displayed that the presence of SNPs or SN (0.01 mg L−1) significantly reduced the toxicity of MCl (0.001, 0.01, 0.1, 1, 10, and 100 mg L−1) and increased the IC50 of MCl from 0.072 ± 0.014 to 0.381 ± 0.029 and 0.676 ± 0.034 mg L−1, respectively. In the presence of SN or SNPs, the mercury-reducing effect on algal population growth significantly decreased. Considering the increase of IC50, the mercury toxicity decreased approximately 5.44 and 9.66 times in the presence of SNPs or SN, respectively. The chlorophyll a and c contents decreased at all exposures; however, the decrease by MCl-SNPs and MCl-SN was significantly less than MCl except at 1 mg L−1. The lowering effect of MCl-SN on chlorophyll contents was less than MCl and MCl-SNPs. MCl exposure induced significant raises in total protein content (TPC) at concentrations < 0.01mg L−1, with a maximum of ~ 70.83% attained at 100 mg L−1. The effects of MCl-SNPs and MCl-SN on TPC were significantly less than MCl. Total lipid content (TLC) at all MCl concentrations was higher than the control, while at coexposure to MCl-SN, TLC did not change until 0.01 mg L−1 compared with the control. The effects of MCl-SN and MCL-SNPs on TPC and TLC were in line with toxicity results, and were significantly less than those of MCl individually, confirming their antagonistic effects on MCl. The morphological changes of algal cells and mercury content of the cell wall at MCl-SN and MCl-SNPs were mitigated compared with MCl exposure. These findings highlight the mitigatory impacts of silver species on mercury toxicity, emphasizing the need for better realizing the mixture toxicity effects of pollutants in the water ecosystem. [ABSTRACT FROM AUTHOR]

Cauvery Delta is the major rice-growing tract of Tamil Nadu. Continuous waterlogging is inevitable in the delta region due to unexpected heavy rain, leading to stunted crop growth and poor soil conditions. The present study aimed to alleviate the waterlogging-associated problems of stunted growth, crop nutrition deficiency, heavy algal growth and poor soil aeration issues in the heavy clayey soils of deltaic region of Tamil Nadu. Field experiments were laid out with the treatments viz., CuSO4, (5kg/ha) (T1), Gypsum (500 kg/ha) (T2), Conoweeding+Alternate Wetting and Drying Irrigation(AWDI) (T3), microbial consortia (K and Zn solubilising Bacteria 500 ml/ha) (T4) control (T5) and combination of all (T6) except CuSO4 along with control. The results indicated that the T6 recorded higher plant height (110.2 cm), productive tillers/m2 of 332, filled grains of 118.3 and less chaffy grains of 20.3 nos, high nutrient status of 265 kg/ha of available N,35.4 kg/ha of available P,342 kg/ha of available K, 21.1meq/100 g of Ca,8.2 meq/100 g of Mg and root length and volume. The algal population in terms of dry biomass was reduced to 3.1 (g/m2) from the control group of 11.2 (g/m²) at 15 days after imposing treatment. The per cent increase of 26.0 % grain yield was also recorded in the combination treatment over control. From the present research, combined application of gypsum @500 kg/ha +Cono weeding twice +AWDI and microbial consortia of Zn and K solubilising bacteria @500ml/ha could be recommended for better soil environment and rice production in the delta region. [ABSTRACT FROM AUTHOR]

Biological processes in the Proterozoic Ocean are often inferred from modern oxygen‐deficient environments (MODEs) or from stable isotopes in preserved sediment. To date, few MODE studies have simultaneously quantified carbon fixation genes and attendant stable isotopic signatures. Consequently, how carbon isotope patterns reflect these pathways has not been thoroughly vetted. Addressing this, we profiled planktonic productivity and quantified carbon fixation pathway genes and associated organic carbon isotope values (δ13CPOC) of size‐fractionated (0.2–2.7 and >2.7 μm) particulate matter from meromictic Fayetteville Green Lake, NY, USA. The high‐O2 Calvin‐Benson‐Bassham (CBB) gene (cbbL) was most abundant in the <2.7 μm size fraction in shallow oxic and deep hypoxic waters, corresponding with cyanobacterial and eukaryote algal populations. The low‐O2 CBB gene (cbbM) was most abundant near the lower oxycline boundary in the larger size fraction, coincident with purple sulfur bacteria populations. The reverse citric acid cycle gene (aclB) was equally abundant in both size fractions in the deepest photic zone, coinciding with green sulfur bacteria populations. Methane coenzyme reductase A (mcrA), of anaerobic methane cyclers, was most abundant at the lower oxycline boundary in both size fractions, coinciding with Methanoregula populations. δ13CPOC values overlapped with the high‐O2 CBB fixation range except for two negative excursions near the lower oxycline boundary, likely reflecting assimilation of isotopically‐depleted groundwater‐derived carbon by autotrophs and sulfate‐reducers. Throughout aphotic waters, δ13CPOC values of the large size fraction became 13C‐enriched, likely reflecting abundant purple sulfur bacterial aggregates. Eukaryote algae‐ or cyanobacteria‐like isotopic signatures corresponded with increases in cbbL, cbbM, and aclB, and enrichment of exopolymer‐rich prokaryotic photoautotrophs aggregates. Results suggest that δ13CPOC values of preserved sediments from areas of the Proterozoic Ocean with sulfidic photic zones may reflect a mixture of alternate carbon‐fixing populations exported from the deep photic zone, challenging the paradigm that sedimentary stable carbon isotope values predominantly reflect oxygenic photosynthesis from surface waters. [ABSTRACT FROM AUTHOR]

Microalgae play a crucial role in various sectors, such as biofuel production or environmental monitoring. The ability to accurately classify and analyze microalgae species from optical images is vital for advancing research and applications. Generally, the data regarding the population of microalgae constitute a valuable input for machine-learning algorithms whose aim is to classify real data derived from optical images of microalgae cells. However, obtaining a diverse dataset of microalgae populations to train machine-learning models can be challenging and resource-intensive. This paper presents a machine-learning algorithm based on a dataset of algal records generated by a simulation model. The simulation model uses a combination of mathematical models, probabilistic distributions, and biological knowledge to create realistic data on microalgae populations. The dataset generated from the developed model serves as a resource for training and validation of the subsequent machine-learning model proposed for the microalgae classification task. The machine learning model, trained on this synthetic data, can subsequently be applied to efficiently classify and analyze optical images of real microalgae populations, leading to improved precision and reliability in the identification of species useful to produce biofuels. [ABSTRACT FROM AUTHOR]

Biogenic volatile organic compounds (VOCs) play key roles in coral reef ecosystems, where, together with dimethylated sulfur compounds, they are indicators of ecosystem health and are used as defense strategies and infochemicals. Assessment and prediction of the exchange rates of VOCs between the oceans and atmosphere, with implications for atmospheric reactivity and climate, are hampered by poor knowledge of the regulating processes and their temporal variability, including diel cycles. Here, we measured the variation over 36h of the concentrations of DMSPCs (dimethylsulfoniopropionate (DMSP)-related compounds, namely DMSP, dimethylsulfoxide, acrylate, dimethylsulfide, and methanethiol as dimethyl disulfide) and VOCs (COS, CS2, isoprene, the iodomethanes CH3I and CH2ClI, and the bromomethanes CHBr3 and CH2Br2), in surface waters inside the shallow, northern coral-reef lagoon of Mo'orea (French Polynesia) and 4 km offshore, in the tropical open ocean. Comparisons with concurrent measurements of sea surface temperature, solar radiation, biogeochemical variables (nutrients, organic matter), and the abundances and taxonomic affiliations of microbial plankton were conducted with the aim to explain interconnections between DMSPCs, VOCs, and their environment across diel cycles. In open ocean waters, deeper surface mixing and low nutrient levels resulted in low phytoplankton biomass and bacterial activity. Consequently, the diel patterns of VOCs were more dependent on photochemical reactions, with daytime increases for several compounds including dissolved dimethylsulfoxide, COS, CS2, CH3I, and CH2ClI. A eukaryotic phytoplankton assemblage dominated by dinoflagellates and haptophytes provided higher cell-associated DMSP concentrations, yet the occurrence of DMSP degradation products (dimethylsulfide, dimethyl disulfide) was limited by photochemical loss. Conversely, in the shallow back reef lagoon the proximity of seafloor sediments, corals and abundant seaweeds resulted in higher nutrient levels, more freshly-produced organic matter, higher bacterial activity, and larger algal populations of Mamiellales, diatoms and Cryptomonadales. Consequently, DMSP and dimethylsulfoxide concentrations were lower but those of most VOCs were higher. A combination of photobiological and photochemical processes yielded sunny-daytime increases and nighttime decreases of dimethylsulfide, dimethyl disulfide, COS, isoprene, iodomethanes and bromomethanes. Our results illustrate the important role of solar radiation in DMSPC and VOC cycling, and are relevant for the design of sampling strategies that seek representative and comparable measurements of these compounds. [ABSTRACT FROM AUTHOR]

Harmful algal blooms (HABs) are a primary environmental concern, threatening freshwater ecosystems and public health and causing economic damages in the billions of dollars annually. These blooms, predominantly driven by phytoplankton species like cyanobacteria, thrive in nutrient-rich, warm, and low-wind environments. Because of the adverse impacts of HABs, this review examines various control methods, focusing on biological strategies as sustainable solutions. While effective in disrupting algal populations, traditional chemical and physical interventions carry ecological risks and can be resource-intensive. Biological control methods, including biomanipulation and using algicidal microorganisms such as Streptococcus thermophiles, Myxobacteria, and Lopharia spadicea, emerge as eco-friendly alternatives offering long-term benefits. Additionally, barley and rice straw application has demonstrated efficacy in curbing HAB growth. These biological approaches work by inhibiting algal proliferation, disrupting cellular structures, and fostering algal cell aggregation. Despite their advantages over conventional methods, biological controls face challenges, including intricate ecological interactions. This article delves into the latest biological techniques aimed at eradicating HABs, intending to diminish their frequency and reduce toxin levels in aquatic environments. While most research to date has been confined to laboratory settings, scaling these methods to field applications presents hurdles due to the variability and complexity of natural ecosystems. The review underscores the need for further research and development in this critical area of environmental science. [ABSTRACT FROM AUTHOR]

Purpose. Software development to quantify the population growth for the microalgae Chlorella. Methods. Software was developed using Python programming language, external libraries: Numpy, Xlsxwriter, Matplotlib and PIL. The developed software suitability to quantify the population growth of the microalgae Chlorella and its verification was determined. During this verification, the population growth of the microalgae with different stages of biomass growth were evaluated. Samples of the microalgae Chlorella were obtained over a period of several weeks' population growth. Results. Software that allows estimating the population growth of the microalgae Chlorella in the aquatic environment has been developed. Using this software, data dependence of the heterogeneity coefficient of microalgae Chlorella vulgaris biomass growth was obtained. The population growth leads to a decrease in this heterogeneity. This effect can be due the optimal conditions presence for the cultivation of microalgae Chlorella vulgaris. Scientific novelty. The effect of microalgae Chlorella population growth on the system homogeneity has been determined. The increase of microalgae Chlorella vulgaris biomass content within 4 weeks leads to coefficient of heterogeneity decrease from 92% to 47%, due to the aggregation of microalgae Chlorella vulgaris in the aquatic environment. Practical significance. Developed software allows quantify the growth of the microalgae Chlorella vulgaris population in the aquatic environment and can be used to control the algae biomass rise in industrial production. Conclusion. Software that allows assessing the uniformity distribution of Chlorella vulgaris microalgae biomass population growth has been developed. It is applicable to study the level of microorganisms' concentration in the aquatic environment. The results of its verification indicate the developed software suitability for practical use. Using the developed software, the influence of Chlorella vulgaris microalgae biomass population growth in the aquatic environment was determined. It is shown that microalgae Chlorella vulgaris population growth from 1 to 4 weeks leads to decrease in the mixing index from 93% to 47%, which is due optimal conditions presence for the cultivation of the microalgae Chlorella vulgaris. The research methodology can be used in the automated monitoring complexes development for the ecological state of water resources and for controlling the industrial production microalgae Chlorella vulgaris population. [ABSTRACT FROM AUTHOR]

In this study, isolate Spirulina sp. from Vellar Estuary; maintain the micro-algal culture under laboratory conditions, perform the mass culture of Spirulina sp., give food as ornamental fishes, check the color enhancement of fishes, check the length and weight of fishes. The collected spirulina was dried at a low temperature, and the spirulina sample ware given to the fish as feed. Microalgae are mass-produced in three different ways for aquaculture: batch (or discontinuous or multistep backup system) culture, semi-continuous culture, and continuous culture. A small axenic stock culture produces a series of cultures of increasing volume in which the algal population of each culture vessel is harvested at or near its peak density, i.e. while still retaining good growth potential, to be used as inoculums for other culture vessels. Growth performance and feed utilization of Goldfish (Carassius auratus) and Guppy fish after 60 days of feeding on experimental diets. There were significant differences in length and weight gain between fish-fed Spirulina sp. supplements and the control diet, although the group supplemented with 1% spirulina sp. had higher body length and weight than the control group. The results of this study showed that spirulina sp. as a feed additive does not influence Goldfish (Carassius auratus) and Guppy growth performance, except for a diet supplemented with 1% Spirulina, which has obvious antioxidant defense and innate and humoral immunity status. Spirulina sp. can potentially be used as a natural antioxidant supplement in the diet. Furthermore, because of its high protein content and lack of detrimental effects on fish performance, Spirulina sp. can be utilized as a fishmeal replacement in Goldfish (Carassius auratus) and Guppy diets. In both Goldfish (Carassius auratus) and Guppy, the skin color content and chroma were found to be considerably higher in the experimental diet than in the control diet. The findings of this study revealed that carotenoids in fish feeds are strongly linked to fish body coloration and that phycocyanin is also involved in fish pigmentation. [ABSTRACT FROM AUTHOR]

In recent years, the total consumption of antibiotics to cure infections has widely increased. Consequently, the concentration of antibiotics in aquatic environments has remarkably heightened. Cefazolin sodium (CFZS) is a first-generation cephalosporin antibiotic with significant bactericidal activities. Immense consumption of CFZS for years along with its persistence in various environments led to its growing deposit in different ecosystems. In this study, the model microalga Chlorella vulgaris was chosen to evaluate the impacts of different concentrations of CFZS on aquatic organisms. Notably, the cell number of the microalgae has declined with the rising concentrations of CFZS. Prepared SEM images and flow cytometry charts confirmed the harmful effects of the antibiotic on the cells of C. vulgaris. Furthermore, CFZS caused an increase in the content of pigments (chlorophyll a, b, carotenoids and anthocyanins), level of non-enzymatic antioxidant compounds (total phenol and flavonoid) and activity of enzymatic antioxidants (CAT, SOD and APX) in C. vulgaris. However, C. vulgaris displayed remarkable potential to remove CFZS from the culture medium. The obtained data may shed light on the establishment of the possible risks of antibiotics to algal populations and also microalgae ability in antibiotics removal. [ABSTRACT FROM AUTHOR]

Autocalibration techniques have the potential to enhance the efficiency and accuracy of intricate process-based hydrodynamic and water quality models. In this study, we developed a new R-based autocalibration toolkit for the Environmental Fluid Dynamics Code (EFDC) and implemented it into the recalibration of the Yuqiao Reservoir Water Quality Model (YRWQM), with long-term observations from 2006 to 2015, including dry, normal, and wet years. The autocalibration toolkit facilitated recalibration and contributed to exploring how a model recalibrated with long-term observations performs more accurately and robustly. Previously, the original YRWQM was calibrated and validated with observations of dry years in 2006 and 2007, respectively. Compared to the original YRWQM, the recalibrated YRWQM performed just as well in water surface elevation, with a Kling–Gupta efficiency (KGE) of 0.99, and water temperature, with a KGE of 0.91, while performing better in modeling total phosphorus (TP), chlorophyll a (Chl a), and dissolved oxygen (DO), with KGEs of 0.10, 0.30, and 0.74, respectively. Furthermore, the KGEs improved by 43 %–202 % in modeling the TP–Chl a –DO process when compared to the models calibrated with only dry, normal, and wet years. The model calibrated in dry years overestimated DO concentrations, probably explained by the parameter of algal growth rate that increased by 84 %. The model calibrated in wet years performed poorly for Chl a , due to a 50 % reduction in the carbon-to-chlorophyll ratio, probably triggered by changes in the composition of the algal population. Our study suggests that calibrating process-based hydrodynamic and water quality models with long-term observations may be an important measure to improve the robustness of models under severe hydrological variability. The newly developed general automatic calibration toolkit and a possible hierarchical autocalibration strategy will also be a powerful tool for future complex model calibration. [ABSTRACT FROM AUTHOR]

Aquatic ecosystems play an important role in global methane cycling and many field studies have reported methane supersaturation in the oxic surface mixed layer (SML) of the ocean and in the epilimnion of lakes. The origin of methane formed under oxic condition is hotly debated and several pathways have recently been offered to explain the "methane paradox." In this context, stable isotope measurements have been applied to constrain methane sources in supersaturated oxygenated waters. Here we present stable carbon isotope signatures for six widespread marine phytoplankton species, three haptophyte algae and three cyanobacteria, incubated under laboratory conditions. The observed isotopic patterns implicate that methane formed by phytoplankton might be clearly distinguished from methane produced by methanogenic archaea. Comparing results from phytoplankton experiments with isotopic data from field measurements, suggests that algal and cyanobacterial populations may contribute substantially to methane formation observed in the SML of oceans and lakes. Plain Language Summary: Methane plays an important role in atmospheric chemistry and physics as it contributes to global warming and to the destruction of ozone in the stratosphere. Knowing the sources and sinks of methane in the environment is a prerequisite for understanding the global atmospheric methane cycle but also to better predict future climate change. Measurements of the stable carbon isotope composition of carbon—the ratio between the heavy and light stable isotope of carbon—help to identify methane sources in the environment and to distinguish them from other formation processes. We identified the carbon isotope fingerprint of methane released from phytoplankton including algal and cyanobacterial species. The observed isotope signature improves our understanding of methane cycling in the surface layers of aquatic environments helping us to better estimate methane emissions to the atmosphere. Key Points: Stable carbon isotope values of methane emitted from six phytoplankton cultures incubated in the laboratoryIsotope fractionation between methane source signature and biomass of widespread algal and cyanobacterial speciesIsotopic patterns of methane released by phytoplankton may be clearly distinguished from methane formed by methanogenic archaea [ABSTRACT FROM AUTHOR]

Paired measurements of phytoplankton absorption and backscatter, the inherent optical properties central to the interpretation of ocean colour remote sensing data, are notoriously rare. We present a dataset of Chlorophyll a (Chl a) -specific phytoplankton absorption, scatter and backscatter for 17 different phytoplankton groups, derived from first principles using measured in vivo pigment absorption and a well-validated semi-analytical coated sphere model which simulates the full suite of biophysically consistent phytoplankton optical properties. The optical properties of each simulated phytoplankton cell are integrated over an entire size distribution and are provided at high spectral resolution. The model code is additionally included to enable user access to the complete set of wavelength-dependent, angularly resolved volume scattering functions. This optically coherent dataset of hyperspectral optical properties for a set of globally significant phytoplankton groups has potential for use in algorithm development towards the optimal exploitation of the new age of hyperspectral satellite radiometry. [ABSTRACT FROM AUTHOR]

Pest outbreaks, harmful algal blooms and population collapses are extreme events with critical consequences for ecosystems. Therefore, understanding the ecological mechanisms underlying these extreme events is crucial. We evaluated theoretical predictions on the size scaling and variance of extreme population abundance by combining (i) the generalized extreme value (GEV) theory and (ii) the resource‐limited metabolic restriction hypothesis for population abundance. Using the phytoplankton data from the L4 station in the English Channel, we showed a negative size scaling of the expected value of maximal density, whose confidence interval included the predicted metabolic scaling (α = −1) supporting theoretical predictions. The role of resources and temperature in the distribution of the size–abundance pattern and residuals was well characterized by the GEV distribution. This comprehensive modelling framework will allow to elucidate community structure and fluctuations and provide unbiased return times estimates, thereby improving the prediction accuracy of the timing of the population outbreaks. [ABSTRACT FROM AUTHOR]

Glacier algae, which are photosynthetic microbes growing on ice, considerably reduce the surface albedo of glaciers and accelerate their melting rate. Although the growth of glacier algae can be suppressed by parasitic chytrids, the impact of chytrids on algal populations is still largely unknown. In this study, we described the morphology of the chytrid infecting the glacier alga Ancylonema nordenskioeldii and quantified the prevalence of infection in different habitats on a mountain glacier in Alaska, USA. Microscopic observations revealed three different morphological types of chytrids with distinct rhizoid shapes. Variations in the size of the sporangia were probably because of their different growth stages, indicating that they actively propagated on the glacier. The prevalence of infection did not vary among sites with different elevations but was substantially higher in cryoconite holes (20%) than on ice surfaces (4%) at all sites. This indicates that cryoconite holes are hot spots for chytrid infections of glacier algae, and the dynamics of cryoconite holes might affect the host–parasite interactions between chytrids and the glacier algae, which may in turn alter surface albedo and ice melting. [ABSTRACT FROM AUTHOR]

Over recent years, the dramatic hydrological variability has challenged the robustness of process-based hydrodynamic and water quality models to long-term continuous biogeochemical processes. In this study, we developed a new R-based autocalibration toolkit for the Environmental Fluid Dynamics Code (EFDC) and implemented it into the recalibration of the Yuqiao Reservoir Water Quality Model (YRWQM) with long-term observations from 2006 to 2015, including dry, normal, and wet years. The autocalibration toolkit facilitated recalibration and contributed to exploring how the model recalibrated with long-term observations performs more accurately and robustly. Previously, the original YRWQM was calibrated and validated with observations of dry years in 2006 and 2007, respectively. Compared to the original YRWQM, the recalibrated YRWQM performed as well in water surface elevation with a Kling-Gupta Efficiency (KGE) of 0.99 and water temperature with a KGE of 0.91, while better in modeling total phosphorus (TP), chlorophyll a (Chl a), and dissolved oxygen (DO) with KGEs of 0.10, 0.30, and 0.74 respectively. Furthermore, to analyze the impact of different hydrological years as calibration periods on the model accuracy and robustness, we also calibrated the model in dry, normal, and wet years. The model calibrated in dry years overestimated DO concentrations, probably explained by the parameter of algal growth rate increased by 84%. The model calibrated in wet years performed poorly for Chl a due to a 50% reduction in the carbon-to-chlorophyll ratio probably triggered by changes in the composition of the algal population. Our study suggests that calibrating process-based hydrodynamic and water quality models with long-term observations may be an important measure to improve the robustness of models under severe hydrological variability. The newly developed general automatic calibration toolkit and a possible hierarchical autocalibration strategy will also be a powerful tool for future complex model calibration. [ABSTRACT FROM AUTHOR]

Climate change stressors, including warming and heatwaves, can alter plankton composition and dominance patterns in temperate shallow lakes, which can disrupt ecosystem function and curtail ecosystem services. Understanding how these alterations could take place under future climates is therefore important.To understand such changes, we performed a year‐long mesocosm experiment with controls reflecting present temperature conditions and a treatment reflecting a future climate change scenario, including heatwaves of 5–8°C above ambient water temperatures.In the warmer conditions, the predatory invertebrate Mesostoma, exerted a strong top‐down control on Daphnia, resulting in a switch in herbivore dominance to Ceriodaphnia in contrast to the controls where Daphnia remained dominant. A complementary predation experiment revealed that Mesostoma fed at a higher rate on Daphnia than on Ceriodaphnia and cyclopoid copepods. Cyclopoids were the least affected taxon but showed tendencies to sustain populations longer into the winter at elevated temperatures. Moreover, both total algal and cyanobacteria biomass increased with warming.Our experiments suggest that predator–prey dynamics may alter plankton community composition and dominance patterns in a warmer climate because thermophilic predatory invertebrates have the potential to induce cascading food‐chain effects and alter the herbivore dominance patterns in lake zooplankton. This may have implications for the algal population dynamics and overall ecosystem function and processes in shallow lakes. [ABSTRACT FROM AUTHOR]

This study exploited the different combinations of nutritional modes (autotrophic, mixotrophic and heterotrophic) of the green alga Scenedesmus obliquus in a two-stage cultivation process to remediate wastes as well as maximise the production of high-protein algal biomass. The alga was first cultivated autotrophically in Stage-one, using 0.5% of digestate as a nutrient source and natural light to support the growth; afterward, the culture was concentrated and used in Stage-two cultivation under the different nutritional modes. 2.5% of anaerobic digestate from food waste was used to provide inorganic nutrients; waste sugar recovered from a confectionery manufacturer was used as the organic carbon source to support mixo- and hetero-trophic growth. In Stage-one, the algae removed ammonium and phosphate at 9.1 mg L−1 day−1 and 3.8 mg L−1 day−1, respectively, and the algal yield approached a carrying capacity of 1 g dry weight per liter. In Stage-two, the algal population increased faster in mixotrophic and heterotrophic modes, reaching a final dry weight concentration of 7.2–10.5 g L−1, than in autotrophic mode. Ammonium and phosphate were consumed at about twice the rate as in autotrophic mode, and 90–100% of the waste sugar was removed within 48–72 h. The final algal biomass had a protein content of 44% in mixotrophic mode, compared to only 32% in autotrophic mode. This study demonstrated that a two-stage cultivation process coupling autotrophic and mixotrophic growth of S. obliquus can be used to remediate both inorganic and organic wastes and boost the production of protein-rich algal biomass, which can be beneficial to a sustainable circular bioeconomy. [ABSTRACT FROM AUTHOR]

Atrazine and S-metolachlor are herbicides widely used on corn and soybean crops where they are sometimes found in concentrations of concern in nearby aquatic ecosystems, potentially affecting autotrophic organisms. The aim of this study was to investigate the response of the green algae Enallax costatus , the diatom Gomphonema parvulum and a culture of the cyanobacteria Phormidium sp. and Microcystis aeruginosa , to atrazine and S-metolachlor alone and in mixture (0, 10, 100 and 1000 µg.L−1, for 7 days). For each culture, chlorophyll fluorescence and effective quantum yield of photosynthesis were determined and compared with lipid and methyl-ester fatty acid profiles. In general, the green algae was most strongly affected by atrazine and S-metolachlor. In particular, atrazine led to a total inhibition of photosynthesis and a sharp decrease in triacylglycerols (TAGs), while S-metolachlor caused a partial decrease in photosynthesis in the green algae and a sharp increase in reserve lipids in the diatom when the herbicide was in mixture. The effect of the mixture of compounds depended on the descriptor considered. Indeed, atrazine seemed to explain the toxicity of the mixture for photosynthetic parameters, while certain lipid classes showed intermediate responses between compounds. The results suggest mechanisms of shade adaptation, algal population increase and lipid remodeling in response to compound exposure. The results reveal differences in sensitivity between species after 7 days exposure to the two compounds alone and in mixture. These results support the value of using the study of lipid and fatty acid profiles as complementary information to traditional descriptors for the assessment of pesticide exposure on photoautotrophic organisms. [Display omitted] • Atrazine and S-metolachlor significantly impacted photosynthesis parameters. • Atrazine and S-metolachlor significantly impacted lipids and fatty acids profiles. • Environmental concentration of S-metolachlor decreased C18:3n-3 content in green algae. • Mixture effects were driven by atrazine and S-metolachlor according to their mode of action. • Ecotoxicological studies should consider the response of multiple species to various descriptors. [ABSTRACT FROM AUTHOR]

Bloom-forming phytoplankton are key players in aquatic ecosystems, fixing carbon dioxide and forming the base of the marine food web. Diverse stresses, such as nutrient depletion, temperature increase, and pathogen emergence can influence the health and dynamics of algal populations. While population responses to these stressors are welldocumented in the aquatic ecosystems, little is known about the individual cellular adaptations. These are however the key to an in-depth physiological understanding of microbiome dynamics in the plankton. Finding solutions to disease control in aquaculture also depends on knowledge of infection dynamics and physiology in algae. Single-cell metabolomics can give insight into infection processes by providing a snapshot of small molecules within a biological system. We used a single-cell metabolome profiling workflow to track metabolic changes of diatoms and dinoflagellates subjected to parasite infection caused by the oomycete Lagenisma coscinodisci and the alveolate Parvilucifera spp. We accurately classified the healthy phenotype of bloom-forming phytoplankton, including the diatoms Coscinodiscus granii and Coscinodiscus radiatus, and the toxic dinoflagellate Alexandrium minutum. We discriminated the infection of the toxic dinoflagellate A. minutum with the alveolate parasitoids Parvilucifera infectans and P. rostrata down to the single-cell resolution. Strain and species-specific responses of the diatom hosts Coscinodiscus spp. Infected with the oomycete pathogen Lagenisma coscinodisci could be recognized. LC-HRMS and fragmentation pattern analysis enabled the structure elucidation of metabolic predictors of infection (guanine, xanthine, DMSP, and pheophorbide). The purine salvage pathway and DMSP lysis could be assigned as regulated processes during host invasion. The findings establish single-cell metabolome profiling with LDI-HRMS coupled with classification analysis as a reliable diagnostic tool to track metabolic changes in algae. [ABSTRACT FROM AUTHOR]

The influence of viruses on nutrient cycles and energy transfer in aquatic systems is important, yet still being determined. We developed a dynamic model to capture the population dynamics of algal hosts and their viruses. The model was fitted to literature data of population dynamics during laboratory one‐step infection experiments. Model parameters that underlie population dynamics were quantified in diverse algal groups, covering 7 different algal classes, 14 different host genera, and 32 different virus genotypes. The hypothesis that trade‐offs exist between traits that underlie population dynamics was evaluated. We report a possible virus size‐dependent trade‐off between the rate at which viruses can initiate infection, and the efficiency of carbon transfer from hosts to viruses upon lysis. We hypothesize that slower rates of infection in large viruses, due to slower rates of molecular diffusion, are compensated by enhanced utilization of host resources. Our approach provides a quantitative trait‐framework for understanding and quantifying virus activity in diverse natural communities. [ABSTRACT FROM AUTHOR]

Coastal benthic communities in temperate regions have been influenced by climate change, including increasing sea-surface temperature. Nevertheless, scleractinian coral Alveopora japonica Eguchi, 1968, is thriving in shallow subtidal hard bottoms around Jeju Island, off the southern coast of Korea. The presence of this corals has negatively impacted subtidal kelp populations in Jeju Island. However, there is no study to document how the presence or absence of this coral relates to other benthic communities. This study investigated the benthos in three shallow subtidal sites (Shinheung (SH), Bukchon (BC), and Seongsan (SS)) in northern Jeju using underwater photography. Macro-benthic organisms appearing on a 1 × 20 m line transect installed at depths of 5, 10, and 15 m at each site were analyzed. Results showed that of the three sites investigated, A. japonica colonies were most abundant at BC, accounting for 45.9% and 72.8% of the total transect area at 10 m and 15 m, respectively. At SS, A. japonica occupied 15.3% of the total area at 15 m and less than 1% at 5 m and 10 m. The same at SH accounted for 10% of the total area at 5 m, and less than 1% at 10 m and 15 m. Dead and bleached colonies accounted for 1.2–11.5% and 1.8–5.7%, respectively, at 5, 10, and 15 m at three sites. At SS, canopy-forming brown algae Ecklonia cava and Sargassum spp. accounted for 20.2 and 24.3% of the total transect area, respectively, at 5 m depth. In contrast, the percent cover of E. cava and Sargassum spp. at SH and BC ranged from 0.1 to 1.8%, respectively. Moreover, non-geniculate coralline algae dominated the subtidal substrate at SH, ranging between 60.2 and 69% at 15 and 10 m. The low cover of A. japonica in SS (at 5 m) coincided with a high percent cover of canopy-forming brown algae. However, canopy-forming brown algae were rare at all depths at SH and BC and were dominated instead by coralline algae and the scleractinian corals. This study, by utilizing a non-destructive method, provides a baseline qualitative and quantitative information for understanding the site and depth-dependent distribution of A. japonica and algal populations, which is important to understand climate change related changes in benthic communities in Jeju and elsewhere. [ABSTRACT FROM AUTHOR]

Molecular investigations have raised concerns about the ecological risks of green tides caused by alien Ulva species in new habitats. The green tide-forming species U. californica Wille was generally considered to be native to North America, but new records have been widely reported in Europe, Asia, and Oceania in recent decades, indicating a strong dispersal capacity of the species. In this study, the first record of U. californica on the coastline of mainland China was reported, following a combined identification with multi-molecular markers and morphological characterization. It was shown that this species has a discontinuous distribution pattern along the coast of mainland China, with northern populations in the Yellow Sea and southern populations in the East China Sea and South China Sea. According to results of examination for life cycles and identification with mating type (MT) genetic markers, it was indicated that all U. californica samples were male gametophytes, and reproduced themselves through parthenogenesis solely. Combined with the fact that southern and northern populations are highly genetically identical, here we believed that U. californica was a recent alien species to mainland China with a rapid local spread. This finding provided evidences that the ability to reproduce in a variety of ways may play an important role in the spread of Ulva species, as well as essential basic data for marine risk management of green tides in China. In addition, according to the phylogeographic analysis, the possible geographical origin and global dispersal routes of U. californica were also proposed. [ABSTRACT FROM AUTHOR]

Nitrogen pollution in the oligotrophic Chaihe Reservoir leads to reconsideration of whether nitrogen control is necessary. Does this mean that eutrophication control has the potential to create "cleaner lakes that are dirtier lakes?" The Chaihe Reservoir is a typical case of a water body with high nitrogen and low algal populations. The relationship between the chlorophyll a (Chla) and nutrients (total nitrogen [TN] and total phosphorus [TP]) in the reservoir was analyzed using the filtering trajectory method (FTM). The results showed that the Chaihe Reservoir recovered to an oligotrophic state after the TP concentration greatly decreased, but it faces a new dilemma of nitrogen pollution. This provides further empirical support for the role of phosphorus in controlling the nitrogen cycle and fate in freshwater ecosystems. The contour plot and Chla-TN/TP diagram indicated that a higher TN/TP contributed to a reduction in Chla. The thresholds for TP and TN in the reservoir were proposed using the double probability method (DPM). It is recommended to remove nitrogen at the end of a drinking water supply system due to the nitrogen pollution of the Chaihe Reservoir. The TN threshold for buffering control provides a quantitative basis for implementing a nutrient management plan. [ABSTRACT FROM AUTHOR]

Global warming has accelerated the degradation of permafrost and glaciers on the Tibetan Plateau, resulting in a substantial release of meltwater that is affecting the regional ecosystem. Despite the significant environmental effects of meltwater, there is a lack of comprehensive studies on the historical changes in meltwater. The key is to obtain reliable quantitative records of meltwater changes. Here, we present Holocene δDwax records from a loess and a peatland on the northeastern Tibetan Plateau, documenting the hydrogen isotopic composition of the regional summer precipitation and surface water affected by meltwater respectively. The two records together reveal substantially increased meltwater during the middle to late Holocene transition, lasting for approximately 1500 years. The meltwater event coincides with a series of exceptional warmth during 5-3 ka across the mid-latitude inland Asia, suggesting that the regional warming was the primary driver of the increased meltwater. This meltwater event had a considerable influence on regional ecology, leading to dramatic fluctuations in algal and bacterial populations and biomass. In addition, this meltwater event may have occurred over a larger area of glaciers and permafrost, where the water isotope records during 5 ka and 3 ka differ from low-latitude regions. This meltwater event, as a crucial aspect of the climatic changes during the middle to late Holocene transition in inland Asia, its driving mechanism and environmental impacts warrant further investigation. • Loess and peat δDwax records on the northeastern Tibetan Plateau are presented. • Meltwater causes discrepancies in δD of precipitation and peatland surface water. • Warmth drivers the meltwater event during the middle to late Holocene transition. [ABSTRACT FROM AUTHOR]

• A review of the diversity, toxicity and distribution of Antarctic Pseudo-nitzschia. • Two new Pseudo-nitzschia species, P. meridionalis and P. glacialis , are described. • Of the eight Antarctic Pseudo-nitzschia species, only P. subcurvata is known toxic. • Limited knowledge exists on the toxicity of Antarctic Pseudo-nitzschia. • Future climate change may increase the risk of harmful Pseudo-nitzschia blooms. Diatoms of the genus Pseudo-nitzschia , known for their potential toxicity, are integral to the phytoplankton community of the Southern Ocean, which surrounds Antarctica. Despite their ecological importance, the diversity and toxicity of Pseudo-nitzschia in this region remain underexplored. Globally, these diatoms are notorious for forming harmful algal blooms in temperate and tropical waters, causing significant impacts on marine life, ecosystems, and coastal economies. However, detailed information on the diversity, morphology, and toxicity of Pseudo-nitzschia species in Antarctic waters is limited, with molecular characterizations of these species being particularly scarce. During three research expeditions to the Southern Ocean, monoclonal strains of Pseudo-nitzschia were isolated and cultivated. Stored samples from a fourth expedition, the Brategg expedition, were used to complete the description of particularly P. turgidula. Through electron microscopy and molecular analysis, two novel species were identified— Pseudo-nitzschia meridionalis sp. nov. and Pseudo-nitzschia glacialis sp. nov.—alongside the previously described species P. subcurvata, P. turgiduloides , and P. turgidula. Toxin assays revealed no detectable levels of domoic acid in P. turgiduloides, P. turgidula, P. meridionalis sp. nov. and P. glacialis sp. nov. Conversely, P. subcurvata was reported in a related study to produce domoic acid and its isomer, isodomoic acid C. These findings emphasize the need for comprehensive research on the phytoplankton of Antarctic waters, which is currently a largely uncharted domain. With the looming threat of climate change, understanding the dynamics of potentially harmful algal populations in this region is becoming increasingly critical. [Display omitted] [ABSTRACT FROM AUTHOR]

Although many studies have focused on the effects of elevated atmospheric CO2 on algal growth, few of them have demonstrated how CO2 interacts with carbon absorption capacity to determine the algal competition at the population level. We conducted a pairwise competition experiment of Phormidium sp., Scenedesmus quadricauda, Chlorella vulgaris and Synedra ulna. The results showed that when the CO2 concentration increased from 400 to 760 ppm, the competitiveness of S. quadricauda increased, the competitiveness of Phormidium sp. and C. vulgaris decreased, and the competitiveness of S. ulna was always the lowest. We constructed a model to explore whether interspecific differences in affinity and flux rate for CO2 and HCO3− could explain changes in competitiveness between algae species along the gradient of atmospheric CO2 concentration. Affinity and flux rates are the capture capacity and transport capacity of substrate respectively, and are inversely proportional to each other. The simulation results showed that, when the atmospheric CO2 concentration was low, species with high affinity for both CO2 and HCO3− (HCHH) had the highest competitiveness, followed by the species with high affinity for CO2 and low affinity for HCO3− (HCLH), the species with low affinity for CO2 and high affinity for HCO3− (LCHH) and the species with low affinity for both CO2 and HCO3− (LCLH); when the CO2 concentration was high, the species were ranked according to the competitive ability: LCHH > LCLH > HCHH > HCLH. Thus, low resource concentration is beneficial to the growth and reproduction of algae with high affinity. With the increase in atmospheric CO2 concentration, the competitive advantage changed from HCHH species to LCHH species. These results indicate the important species types contributing to water bloom under the background of increasing global atmospheric CO2, highlighting the importance of carbon absorption characteristics in understanding, predicting and regulating population dynamics and community composition of algae. [ABSTRACT FROM AUTHOR]

Eco-friendly anti-algal agents are in demand for preventing the growth of unwanted algae. Green synthesized nanoparticles exhibit antimicrobial properties and have been used as a better alternative against chemical and physical processes. In the present study, treatment of silver nitrate with leaf extracts (5% w/v) of Tinospora cordifolia, a plant with proven antimicrobial effects, exhibited UV-visible absorption maxima between 440-460 nm after 1h indicating bioreduction of silver to nanoparticles. The green synthesised silver nanoparticles (5 mgl-1) exhibited inhibition zones against Chlamydomonas reinhardtii in in vitro agar assays. Treatment with green synthesised silver nanoparticles during exponential phase of algal growth resulted in significant reduction in algal population, carbohydrate, protein and chlorophyll contents confirming the anti-algal potential. This is the first report on the growth inhibitory potential of green synthesised silver nanoparticles against green algae. [ABSTRACT FROM AUTHOR]

Coccolithophores are a diverse group of calcifying microalgae that have left a prominent fossil record on Earth. Various coccolithophore relics, both organic and inorganic, serve as proxies for reconstruction of past oceanic conditions. Emiliania huxleyi is the most widely distributed representative of the coccolithophores in modern oceans and is known to engage in dynamic interactions with bacteria. Algal–bacterial interactions influence various aspects of algal physiology and alter algal alkenone unsaturation (UK'37), a frequently used organic coccolithophore‐derived paleo‐temperature proxy. Whether algal–bacterial interactions influence inorganic coccolithophore‐derived paleo‐proxies is yet unknown. A commonly used inorganic proxy for past productivity and sea surface temperature is the Sr/Ca ratio of the coccolith calcite. Interestingly, during interactions between bacteria and a population of calcifying algae, bacteria were shown to physically attach only to non‐calcified algal cells, suggesting an influence on algal calcification. In this study, we explore the effects of algal–bacterial interactions on calcification and coccolith Sr/Ca ratios. We find that while bacteria attach only to non‐calcified algal cells, coccolith cell coverage and overall calcite production in algal populations with and without bacteria is similar. Furthermore, we find that Sr/Ca values are impacted only by water temperature and algal growth rate, regardless of bacterial influences on algal physiology. Our observations reinforce the robustness of coccolith Sr/Ca ratios as a paleo‐proxy independent of microbial interactions and highlight a fundamental difference between organic and inorganic paleo‐proxies. [ABSTRACT FROM AUTHOR]

Jebakumar, J.P.P.; Nandhagopal, G.; RajanBabu, B.; Ragumaran, S.; Kiran, A.S., and Ravichandran, V., 2022. Ecological appraisal of geotextiles in coastal erosion protection engineering. Journal of Coastal Research, 38(2), 345–354. Coconut Creek (Florida), ISSN 0749-0208. The emergence of geotextiles in coastal erosion protection as an alternative material to stone boulders and concrete tetrapods is evident in the recent past. The submergence of geotextiles being colonized by epibiotic organisms on their surface is called marine growth, similar to all other materials inundated in seawater. It includes organisms of the primary producers of algal populations, secondary consumers, and filter feeders of benthic-fouling communities crusting geotextiles' surface. In-situ experimental studies of more than a year of research at a fishing harbour along Chennai coast, India, projected a typical pattern of epibiotic encrustation and its impact on tensile strength nonwoven geotextiles fabrics. Results demonstrated a patchy-mosaic design of marine growth on the geotextile comprising 41 species of sessile invertebrates, including seaweeds, showing a natural succession of biotic density and diversity. Noted distinct stages in colonization were commencing with the domination of deposit feeders, followed by filter feeders, secondary consumers, and primary producers, where later filter feeders subjugated them. The incidence of fundamental ecological succession based on food availability, nature of trophic consumers, and intra/interspecific competition lead to dynamic population shifts on geotextiles. The monolayer settlement pattern of marine growth on the surface is dominated by the benthic filter-feeding community, forming an inverted trophic pyramid structure. Significant differences in tensile strength between geotextile with and without marine growth (p = 0.042) and the progressive improvement in tensile strength indicated no adverse impact on the erosion protection structure's stability. Thus, a harmonious relationship between population density and tensile strength (r = 0.8) represents a mutual relationship between encrusting biota and geotextile substrate, resulting in camouflaging with the coastal background ecosystems as an innovative ecodesign for coastal erosion protection engineering. [ABSTRACT FROM AUTHOR]

Antibiotics are used to treat bacterial infections in humans and animals and also act as a growth promoter for poultry. Due to incomplete metabolism, these antibiotics are excreted in the environment in their parental forms and accumulates in the aquatic ecosystem. Besides the evolution of antibiotic resistant bacteria, these drugs can damage non-target organisms. Green algae are highly sensitive to different antibiotics. Damage in the algal population will cause imbalances in the ecosystems. Till now, the mechanisms of antibiotic toxicity towards algae have not been completely elucidated. It was observed that antibiotics mainly affected the photosynthetic machinery and decreased the carbon fixation process, finally resulting in algal growth inhibition. This present review deals with antibiotics classification, various routes of antibiotics exposure to the freshwater environment, sensitivity towards the different classes of antibiotics, possible Mode-of-Action (MOA) on algal systems, and gaps that need to be filled. Significant gaps include the unavailability of proper eco-toxicological data for antibiotics. Moreover, they exist in nature as complex mixtures, and their behavior in the ecosystem may vastly differ from the parent molecules. To improve our understanding of antibiotic responses mechanism in real-life scenarios, mixture toxicity studies may be the first step. [ABSTRACT FROM AUTHOR]

The macroinvertebrates associated with algae casts light on the possibility of coevolution in a specific environmental context. The understanding of how biological and environmental factors could favor, or limit such interactions and represent an important step for the comprehension of river socio-ecology dynamics. The aim of this study is to establish convergences and recurrent relationships between the most frequent algal groups and associated macroinvertebrates in temperate and tropical rivers from Mexico and Spain. We collected algal population from sixteen rivers, identifying that environmental factors and the algae characteristics that influence the biotic associations with macroinvertebrates and their implications in conservation from a biological and functional perspective. We found that habitat preference is guided by algae as a provider of food and shelter and that environmental factors were secondary. Paralemanea and Lemanea spp. (Rodophyta) recorded the greatest structural complexity, promoting more diverse but less specific associations, which could be a factor that limits co-evolution. Conversely, Phormidium and Nostoc (Cyanobacteria) recorded less diversity but greater specificity; in particular, Cricotopus (Chironomidae) was dominant, suggesting a recurrent association with the possibility of coupled life cycles. The algal structural complexity was the preponderant factor in determining the specificity of associated macroinvertebrates. The associations were in turn related to a river's specific environmental context, for example, Nostoc and Cricotopus were characteristic of oligotrophic waters, while Paralemanea and Lemanea with Hydroptilidae and Hydrobiosidae (Trichoptera) were recurrent in meso-eutrophic waters. Implications for insect conservation: Changes in aquatic ecosystem quality can affect the establishment of populations of algae and insects, affecting species conservation and coexistence relationships mediated by evolutionary coupling events. [ABSTRACT FROM AUTHOR]

A one- year seasonal study was carried out to estimate the algal population and its biochemical contents in Lake Qarun in Egypt. Twelve samples representing Lake Qarun and two drains (El-Bats and El-Wadi) were examined. Bacillariophyta was the most dominant in phytoplankton assemblages. The highest seasonal phytoplankton density was recorded during summer, whereas the lowest was in autumn. The lowest spatial phytoplankton density, chlorophyll (a), and carotenoid concentrations were recorded in drains. ANOVA revealed significant differences between seasons and stations in the density of phytoplankton species, protein, carbohydrate, and lipid. Principal component analysis (PCA) results showed that water temperature was positively correlated with Ochrophyta, Cyanobacteria, Cryptophyta and some dominant phytoplankton species, meanwhile; water temperature was negatively correlated with Bacillariophyta, some dominant phytoplankton species, Chl (a), carotenoid, protein, carbohydrate, and lipid. Hence, water temperature and nutrients (NO3 and PO4), drained into the lake, play a major role in the trophic state changes of Lake Qarun, and its effect on the phytoplankton community and other environmental conditions was detected during the seasons of the year. [ABSTRACT FROM AUTHOR]

Mathematical modeling offers an avenue to predict distributions of microplastics in the ocean. With this goal in mind this study presents a simple analytic model describing the deterministic dynamics of long‐time vertical motion of buoyant microplastics that have succumbed to biofouling in a quiescent ocean. The model couples equations governing vertical particle position and algal population dynamics and is formulated in a nondimensional frame work to determine the minimum number of system parameters. We present results which give a comprehensive understanding of the system's key dynamics when varying four parameters. Previous studies have shown that biofouling causes microplastic particles to oscillate below the ocean's surface; however, for the first time we are able to identify the fundamental processes that govern the microplastic trajectories. The model demonstrates that plastic particle properties are the biggest factor in determining the period and characteristics of the oscillation profile, while the algal population dynamics determine the maximum depth reached. As the fouled particles cross the pycnocline their long‐term behavior is to become trapped within a subsurface layer, bounded by the depth of the euphotic zone and the seasonal pycnocline. The smallest particles are extremely sensitive to algal cell attachment and growth suggesting they are always submerged at depths surrounding the base of the euphotic zone or could become trapped in large algal colonies. In general, the results suggest that a higher concentration of biofouled microplastic is expected to be found subsurface, trapped close to the euphotic zone depth rather than at the ocean's surface. [ABSTRACT FROM AUTHOR]

The brown bull-kelp Durvillaea antarctica (Chamisso), is an ecosystem engineer species distributed from Coquimbo to Cape Horn in the rocky intertidal and subtidal. This resource is of high commercial importance in central and southern Chile and is an artisanal fishery that operates mainly under an open-access regime. This resource provides the domestic market with direct food and the international market with raw materials for the alginate industry. In recent years, the algal population has exhibited a sharp increase in landings due to increased exports, which could negatively affect the sustainability of this fishery. In this study, the situation of the D. antarctica algae fishery on the coast of the Maule Region in central Chile during the last two decades (2000–2021) was evaluated using the Driver-Pressure-State-Impact-Response (DPSIR) conceptual framework. The findings show that the dynamics of the fishery are influenced by high international demand, which has promoted an increase in landing (pressure) from 2005 to the present, with the maximum recorded in 2017, of 732 tonnes. This, as a reaction to driving forces constituted by social (increase in the number of fisher) and economic (first sale price) factors. Furthermore, the negative effects on the "state" of the resource population and the species with which it interacts have not been fully examined, and the negative economic "impacts" are a consequence of the reduction in fishermen's revenues, high percentage of informal labor, and the delayed "response" of the fishery's governance. Efforts should be redoubled to integrate —within a holistic analytical framework— the variables and interactions that improve our ability to understand and anticipate unexpected responses. • The DPSIR assessed the status of Durvillaea antarctica in Chile's central coastline. • The indicator selection procedure was quite complex due to incomplete data recording. • Number of fishers and first sale-price were main reasons for the rise in fishing pressure. • Increased fishing pressure affects the status of the D. antarctica population. • DPSIR reveals weaknesses in knowledge output and fishery operations. [ABSTRACT FROM AUTHOR]

Cyanobacteria are oxygenic photosynthetic microorganisms known for their agricultural and industrial importance. Unavailability of efficient and fast isolation and purification methods of cyanobacteria has impeded our understanding of cyanobacterial diversity. A number of techniques for isolation and purification of cyanobacteria are available, but most of them are cumbersome as well as time-consuming. In the present study, we modified and validated a uni-algal isolation technique named as Microscope Assisted Uni-algal isolation through Dilution (MAU-D) which used dilution of mixed algal population on slide and isolation of single type of cyanobacterial cells using light microscope. Using this technique, we obtained 81 cyanobacterial isolates belonging to various species from 19 different genera from soil and water samples collected from rice fields of Uttar Pradesh, India. This technique also resulted in isolation of six distinct genera, viz., Cyanobacterium, Toxopsis, Desertifilum, Chroococcidiopsis, Halomicronema, and Alkalinema, which were previously not reported from rice fields of India. Hence, the MAU-D technique presents a simple, comparatively fast method of isolation and purification of cyanobacteria which can help to isolate those cyanobacteria which are difficult to isolate through routine sub-culturing. [ABSTRACT FROM AUTHOR]

Formation of oxygen-based free radicals from photochemical decomposition of hydrogen peroxide (H2O2) on Mars may be a key factor in the potential survival of terrestrial-like organisms on the red planet. Martian conditions that generate reactive oxygen species involve the decomposition of H2O2 at temperatures of around 278 K under relatively high doses of C-band ultraviolet radiation (UVC). This process is further amplified by the presence of iron oxides and perchlorates. Photosynthetic organisms exhibit a number of evolutionary traits that allow them to withstand both oxidative stress and UVC radiation. Here, we examine the effect of free radicals produced by the decomposition of H2O2 under emulated martian conditions on the viability of Scenedesmus dimorphus, a unicellular alga that is resistant to UVC radiation and varying levels of perchlorate and H2O2, both of which are present on Mars. Identification and quantification of free radicals formed under these conditions were performed with Electron Paramagnetic Resonance spectroscopy. These results were correlated with the viability of S. dimorphus, and the formation of oxygen-based free radicals and survival of the alga were found to be strongly dependent on the amount of H2O2 available. For H2O2 amounts close to those present in the rarefied martian environment, the products of these catalytic reactions did not have a significant effect on the algal population growth curve. [ABSTRACT FROM AUTHOR]