Occurrence Of Blooms Research Articles

Risk assessment of cyanobacteria toxic metabolites on freshwater ecosystems applying molecular methods.

Cyanobacteria, ancient prokaryotes, interfere with ecosystem water quality through the production of cyanotoxins and bloom formation. Therefore, for water safety and public health reasons, the application of faster, sensitive, and specific tools on its risk assessment is demanded. Polymerase chain reaction (PCR) coupled with DNA sequencing can be a helpful tool for the presence and potential to cyanotoxicity. To achieve these, seven waterbodies located on the North and Center regions of Portugal were sampled for two monitoring periods (2017 and 2018). Thus, given the five risk levels proposed (none up to four cyanotoxins - mcyA, cyrC, anaC, sxtI - being detected per risk level), results showed that the great majority of the ecosystems analyzed on the presence of blooms and under climate change phenomenon (heat waves) had an elevated risk (up to four cyanotoxins being detected) corresponding to a situation of high potential of cyanotoxicity. In the opposite conditions (i.e., absence of blooms and heat waves), the risk was lowered to none or only one cyanotoxin being detected. Two ecosystems escaped this trend and demonstrated little to no alterations among risk levels from 1 year to another corresponding to a high potential of cyanotoxicity and cyanotoxins persistence in comparison to other studied ecosystems. Overall, the risk assessment undertaken suggests that other ecosystems ecological variables (physical, hydrological, or chemical) are interfering on the occurrence and persistence of cyanotoxins biosynthesis genes. Given the observed conditions (eutrophic status, bloom occurrence, and heat waves) of the analyzed ecosystems, cyanobacterial potential for toxicity seems to have increased, suggesting a need of the incorporation of other cyanotoxins apart of the regulated microcystins-LR on cyanotoxins surveillance programs of Portugal.

Sulfate radical-based advanced oxidation process for algal toxin mineralization in seawater desalination

The effects of discharged brine from desalination plants, particularly brine containing algal toxins during harmful agal bloom (HAB) occurrence, are a major concern for marine life and, as a result, human health. Therefore, removing algal toxins from desalination brine is critical for safeguarding both human health and the marine environment. The present work examined the mineralization of domoic acid (DA), an algal toxin, in highly concentrated seawater for the first time using an ultraviolet light activated peroxymonosulfate (UV/PMS) system. Mineralization efficiencies, effects of various anion concentrations, and reaction by-products were investigated. The presence of anions such as chloride, bromide, and bicarbonate reduces the mineralization efficiency of the UV/PMS system, with bromide being the most detrimental. Although DA can be effectively degraded in synthetic seawater (35,000 ppm), total mineralization is not possible within 180 min of reaction time, with only 38.4 %, 44.8 %, and 41 % TOC removal in pH 3, 5, and 7, respectively, when 1 mM of PMS was used. Analyses of treated hypersaline seawater using ultra-high-resolution liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and ion chromatography revealed that DA was completely degraded in synthetic seawater and that, in the presence of algal organic matter, no toxic by-product was generated during the detoxification process. Overall, the UV/PMS system has the potential to be an effective treatment strategy for algal toxins in seawater during HAB events in the SWRO desalination process.

Karenia brevis bloom patterns on the west Florida shelf between 2003 and 2019: Integration of field and satellite observations

Harmful algal blooms of the toxic dinoflagellate Karenia brevis occur almost annually on the West Florida Shelf (WFS) of the eastern Gulf of Mexico. To date, however, comprehensive assessments of K. brevis bloom spatial extent and temporal occurrence are lacking due to limitations in the two primary bloom monitoring techniques: microscopy evaluation of field-collected water samples and satellite remote sensing of ocean color. This is despite community efforts in expanding sampling coverage statewide and developing remote sensing algorithms to interpret color changes of surface waters. In this work, an approach is developed to combine the strengths of both techniques to estimate mean bloom occurrence frequency and bloom intensity as well as bloom extent at weekly, bi-weekly, monthly, and annual intervals between 2003 and 2019. Here, due to technical constraints on ocean color remote sensing, a bloom is defined as waters with K. brevis concentrations greater than 1.5 × 105 cells L−1. While microscopy examination of surface water samples provides K. brevis cell concentrations to help delineate bloom locations from Moderate Resolution Imaging Spectrometer on Aqua (MODIS/A) images, the imagery provides far more synoptic and frequent observations to make the bloom characterization statistically meaningful. Such derived bloom statistics often show bloom patterns that are not always known previously or at the time of the event, and in some years, they also differ from those determined from microscopic taxonomy data alone. For example, in terms of bloom size, two major bloom periods are observed in 2005 – 2007 and 2014 – 2018, respectively, when annual cumulative bloom size exceeded ∼50,000 km2. While preliminary in nature, the approach and results from this work may represent a first step to integrate water sample analysis and satellite remote sensing towards an improved characterization of K. brevis blooms on the WFS.

Salinization as a driver of eutrophication symptoms in an urban lake (Lake Wilcox, Ontario, Canada)

Lake Wilcox (LW), a shallow kettle lake located in southern Ontario, has experienced multiple phases of land use change associated with human settlement and residential development in its watershed since the early 1900s. Urban growth has coincided with water quality deterioration, including the occurrence of algal blooms and depletion of dissolved oxygen (DO) in the water column. We analyzed 22 years of water chemistry, land use, and climate data (1996–2018) using principal component analysis (PCA) and multiple linear regression (MLR) to identify the contributions of climate, urbanization, and nutrient loading to the changes in water chemistry. Variations in water column stratification, phosphorus (P) speciation, and chl-a (as a proxy for algal abundance) explain 76 % of the observed temporal trends of the four main PCA components derived from water chemistry data. MLR results further imply that the intensity of stratification, quantified by the Brunt-Väisälä frequency, is a major predictor of the changes in water quality. Other important factors explaining the variations in nitrogen (N) and P speciation, and the DO concentrations, are watershed imperviousness and lake chloride concentrations that, in turn, are closely correlated. We conclude that the observed in-lake water quality trends over the past two decades are linked to urbanization via increased salinization associated with expanding impervious land cover, rather than increasing external P loading. The rising salinity promotes water column stratification, which reduces the oxygenation of the hypolimnion and enhances internal P loading to the water column. Thus, stricter controls on the application and runoff of de-icing salt should be considered as part of managing eutrophication symptoms in lakes of cold climate regions.

Cyanobacterial blooms in earthen aquaculture ponds and their impact on fisheries and human health in Bangladesh

Cyanobacteria can form intense and sometimes toxic blooms in all kinds of aquatic ecosystems, typified as cyanobacterial bloom. Cyanobacterial blooms can create a range of harmful toxins, which may disturb water sources, successively posing serious health threat to living organisms, and at this stage they are termed as cyanobacterial harmful algal blooms (CyanoHABs). The occurrence of cyanobacterial blooms and cyanobacterial toxins are globally reported, so is the evident in Bangladesh, mainly trigged by increased anthropogenic eutrophication and global climate change. Cyanobacterial blooms and the accumulation of several toxins in human's drinking water, recreational water and aquatic biota such as zooplankton, fish larvae and juveniles interrupt aquaculture, aquatic ecosystem and public health in Bangladesh. As the management measures of toxic cyanobacteria and cyanotoxin are insufficient in Bangladesh, and the proper management for mitigating the worldwide occurrence of toxic cyanobacterial blooms is crucial for maintenance and sustainable development of functional ecosystems, some recommendations are illustrated. Further appropriate research on biology and ecology of cyanobacteria, cyanobacterial toxins and their relationship with environmental factors as well as nutrient management in fish ponds to manage noxious and harmful algae is essential to minimize their adverse impacts on aquaculture and public health for the country.

Evolution of harmful algal blooms in the East China Sea under eutrophication and warming scenarios

Harmful algal blooms (HABs) worldwide are experiencing obvious changes under the combined impacts of global warming, eutrophication, and other driving forces. In the East China Sea (ECS), large-scale blooms caused by dinoflagellates occurred since 2000 and there has been an apparent shift of bloom-causative microalgae from diatoms to dinoflagellates. To predict the future evolution of HABs in this region, a model was developed based on the competition between diatoms and dinoflagellates, which would serve to reproduce the seasonal succession of microalgal blooms driven by multiple environmental factors. The evolution features of HABs were then projected under different scenarios of eutrophication and global warming. Under the ‘business as usual’ scenario, dinoflagellate blooms are expected to become more frequent with higher peak biomass concentrations over the next 30 years. Changes in nutrient composition of the Changjiang riverine discharge may largely give rise to this phenomenon, and accelerated warming associated with climate change may result in earlier occurrence of dinoflagellate blooms. To prevent further intensification of dinoflagellate blooms, efforts could be made to reduce nitrogen inputs and maintain or even increase silicate inputs from the Changjiang river.

Deciphering the potential of Ba/Ca, Mo/Ca and Li/Ca profiles in the bivalve shell Pecten maximus as proxies for the reconstruction of phytoplankton dynamics

Shells of the fast-growing bivalve Pecten maximus serve as a geochemical archive for the reconstruction of past phytoplankton dynamics. Specifically, high-resolution, temporally accurately aligned molar barium-to-calcium (Ba/Cashell), molybdenum-to-calcium (Mo/Cashell) and lithium-to-calcium ratios (Li/Cashell) of the shell calcite revealed distinct peaks which are closely linked to phytoplankton dynamics. Yet, the development and applicability of these geochemical proxies is still at an early stage and needs further calibration. In this study, we examined the relationship between the timing and magnitude of Ba/Cashell, Mo/Cashell and Li/Cashell peaks of P. maximus and the occurrence of various phytoplankton species (diatoms and dinoflagellates) from a statistical perspective. Studied shell samples (three specimens per calendar year) as well as detailed phytoplankton observation data were derived from the well-studied costal ecosystem of the Bay of Brest (France) over three years (2011, 2012 and 2019). An algorithm-based pseudo-random sampling simulation technique was established that analyzed the complex phytoplankton datasets with respect to the profiles of Ba/Cashell, Mo/Cashell and Li/Cashell to identify potential patterns between phytoplankton and trace element time-series. The simulation results indicate that the timing and magnitude of Ba/Cashell, Mo/Cashell and Li/Cashell peaks agreed best with the occurrence of specific phytoplankton blooms that developed ca. one to two weeks earlier. The data suggest that the formation of transient Ba/Cashell peaks had a plurispecific origin, i.e., potentially linked to blooms of ingestible diatom, dinoflagellate and flagellate species enriched in Ba that occurred 8 to 12 days earlier. Observed peaks in Mo/Cashell profiles demonstrably followed the timing and intensity of blooms of the dominant dinoflagellate genus Gymnodinium spp. after a short time lag of around 8 days, potentially linked to an enhanced enzyme activity of nitrate reductase that requires the presence of Mo in the dinoflagellate cells. In addition, Mo/Cashell peaks agreed with periods of diatom aggregate formation which were hypothesized to induce the formation of Mo/Cashell peaks in scallop shells. Li/Cashell profiles revealed similar patterns as large blooms of the diatom Chaetoceros spp. as well as to neurotoxin producing diatoms of the genus Pseudo-nitzschia when considering a short time lag of 8 to 12 days. These findings highlight the great potential of using Ba/Cashell, Mo/Cashell and Li/Cashell chronologies in P. maximus shells as proxies of past phytoplankton dynamics.

Functional Groups of Phytoplankton and Their Relationship with Environmental Factors in Lake Maninjau, West Sumatra, Indonesia

Lake Maninjau is a eutrophic lake indicated by the frequent occurrence of cyanobacterial blooms. The phytoplankton functional groups (FGs) reflect the environmental characteristics and can be useful to monitor the trophic state and evaluate lake’s environmental conditions. This study aims to perceive the composition of phytoplankton FGs and their relation to the environmental factors in Lake Maninjau. The data including phytoplankton and environmental factors were collected in 2001, 2005, 2009, 2014, 2015, 2016, and 2018. There were 21 FGs of phytoplankton recorded in Lake Maninjau. FGs of D, J, F, and NA were commonly found in this Lake. The phytoplankton FGs reflected the dynamic of the environmental characteristics of the lake. The FGs NA representative of oligo to mesotrophic habitat type were predominated accounting for 66.3% to 67.69 % in May 2005 with the lake’s conditions characterized by low TP concentration, high Secchi depth and TN: TP ratio. The FGs of M representative of eutrophic to hypereutrophic habitat type were predominated accounting for 74.14 % to 94.96 % in April 2018 with the lake’s conditions characterized by high TP concentration, low TN: TP ratio, and Secchi depth. A canonical correspondence analysis (CCA) showed that temperature, conductivity, and total phosphorus are important environmental factors to have influenced the succession of phytoplankton FGs in Lake Maninjau.

A high-resolution time series of particulate matter fatty acids reveals temporal dynamics of the composition and quality available to zooplankton in a temperate coastal ocean

Particulate organic matter (POM) forms the base of the pelagic food web, but is a complex category of material that undergoes substantial changes in quantity and quality across different time scales. As the primary consumers of POM, zooplankton are influenced by these fluctuations, resulting in shifts in the food web pathways that contribute to the production of higher trophic levels. We measured POM fatty acids, which are critical nutritional components in marine food webs, along with a suite of associated biotic and abiotic environmental conditions at a temperate coastal site over four years. Using these data, we investigated the co-occurring patterns of prey quality, quantity, and size, to develop a holistic understanding of how the prey field for zooplankton varies over the seasonal cycle and inter-annually. The seasonal pattern of POM fatty acids corresponded to the succession of phytoplankton taxa, but displayed stronger relationships to size-fractionated Chl a than taxonomic observations. Times with high micro-Chl biomass (spring and fall blooms) had the greatest concentrations of high quality food, but fatty acid levels remained high throughout the summer when Chl a concentrations dropped and the size distribution shifted towards pico-Chl. The 18-carbon polyunsaturated fatty acids 18:3ω3 (α-linolenic acid) and 18:4ω3 (stearidonic acid) increased during this time and were correlated with pico-Chl. In addition, the important nutritional factor for zooplankton and fish, the fatty acid ratio DHA:EPA (22:6ω3/20:5ω3), peaked during the middle of summer separately from the peak in Chl a. These seasonal patterns resulted in tradeoffs among the abundance, size, and nutritional quality of prey for zooplankton. We validated the basal sources of several fatty acids used as trophic markers within food web studies and in particular note their power for resolving size-based trophic connections. Interannual variability, e.g., the occurrence of fall diatom blooms and the timing of community shifts, is also discussed. This work lays the foundation for future studies of the zooplankton community at this location and the incorporation of realistic prey conditions into zooplankton studies.

Fungal community dynamics associated with harmful cyanobacterial blooms in two Great Lakes

Harmful algal blooms (HABs) impose major costs on aquatic ecosystems worldwide, including the Laurentian Great Lakes. Microbial consumers, including fungi, can have important interactions with bloom-forming algae and cyanobacteria, although relatively few studies have investigated the relationship between fungi and HABs. We examined changes in the aquatic fungal community coincident with the occurrence of large cyanobacterial blooms in two areas of the Great Lakes (western Lake Erie and Saginaw Bay, Lake Huron). We collected water samples over the course of bloom development, peak, and decline from 3 sites in western Lake Erie on 11 dates and 2 sites in Saginaw Bay on 4 dates. Single molecule sequencing (PacBio RS II) with two molecular markers (the internal transcribed spacer (ITS) of the rRNA locus using fungal-specific primers and the 18S rRNA with primers targeting early-diverging lineages of fungi) was used to estimate fungal community composition. Results indicate a diverse fungal community within the lakes, including several major fungal phyla. The Chytridiomycota were particularly well-represented (54.8% and 45.4% of ITS and 18S sequences, respectively), and we also found representation from both Cryptomycota and Aphelidiomycota, which are putatively obligate intracellular parasites. Further, we found associations between the fungal community (alpha diversity; community composition) and measures of bloom magnitude (chlorophyll a, phycocyanin, and microcystin concentrations) in western Lake Erie. Our results suggest potentially important spatial and temporal heterogeneity in the fungal community that motivates further research on functional importance of fungi in the Great Lakes and consequences for HABs and freshwater ecosystems more broadly.

Inhibitory Effect of Isolated Bacteria from the Phycosphere of Levanderina fissa on the Growth of Different Microalgae

Levanderina fissa (formerly Gyrodinium instriatum) frequently causes blooms in the Pearl River Estuary and has few advantages in interspecific competition with other bloom-forming algal species. Phycosphere bacteria, which closely interact with algal cells, may play an ecologically functional role in the population dynamics and bloom occurrence. To test this hypothesis, we isolated and identified cultivable bacteria coexisting in different growth stages of L. fissa by the gradient dilution method and investigated the characteristics of the bacterial interactions with three diatom species (Chaetoceros curvisetus, Skeletonema dohrnii, and Phaeodactylum tricornutum) and three dinoflagellate species (Scrippsiella acuminata, Karenia mikimotoi, and the host algae) after screening for functional bacteria. One of the isolated bacterial strains, Lf7, which was phylogenetically identified as an Alteromonas species, showed significant inhibitory effects on different algal species except its host. Moreover, all algal species, especially their hosts, showed significant stimulatory effects on bacterial Lf7 growth. These results indicate that the phycosphere bacterium Lf7 may play some ecological roles in the competition between its host alga L. fissa and other phytoplankton. The study also highlights the complicated interactions between phycosphere bacteria and host algae.

Spatial and temporal distributions of microplastics and their macroscopic relationship with algal blooms in Chaohu Lake, China

Microplastics are emerging pollutants with sizes less than 5 mm, and they are ubiquitous. The occurrence of algal blooms has become a major problem affecting water quality in Chaohu Lake. To understand the relationship between the microplastic distribution and algal bloom density from a macroscopic point of view in Chaohu Lake, we collected microplastic samples from water and sediments during the wet and dry seasons and collected satellite remote sensing images of the algae density in recent years. The research results showed that the spatial and temporal distributions of microplastics were uneven and varied greatly. The average abundances of microplastics in the water samples were 2133 ± 1534 n•m−3 in the dry season and 1679 ± 1577 n•m−3 in the wet season, and the average abundance of microplastics in sediments was 308 ± 231 n•kg−1. The abundance of microplastics in the estuaries was higher than those in other locations, and it was higher in the western part of the lake than in the eastern part. The microplastics in water and sediments presented different sizes, colors, shapes and compositions. The abundance, distribution and migration of microplastics were mainly affected by population density, rainfall, runoff, hydrodynamic force and wind direction. At a more macroscopic level, the distribution of microplastics was similar to that of algal blooms, TN and TP to some extent, especially in the early stage of algal bloom outbreaks, and the algal density was significantly positively correlated with the flux of microplastics into the lake. Microplastics, as carriers of algae, could promote the growth of algae blooms in the early stage, while in the later stage, microplastics and algal blooms could aggregate and coprecipitate through adsorption or adhesion and then inhibit the growth of algae.

Removal of Cylindrospermopsin by Adsorption on Granular Activated Carbon, Selection of Carbons and Estimated Fixed-Bed Breakthrough

Climate change and the increase in the availability of nutrients in aquatic environments have increased the occurrence of cyanobacterial blooms which can produce cyanotoxins such as cylindrospermopsin (CYN). Activated carbon adsorption have been proved to be efficient for CYN removal. In the present study, a carbon with high CYN adsorption capacity was identified between two granular activated carbons. For this carbon was estimated the operating time of a full-scale granular activated carbon column under different empty bed contact times (EBCT). The fixed-bed breakthrough was estimated using the Homogeneous Surface Diffusion Model (HSDM). Wood carbon showed greater capacity to remove CYN. The experimental equilibrium data best fitted Langmuir isotherm model, in which wood carbon had a maximum adsorption capacity of 3.67 μg/mg and Langmuir adsorption constant of 0.2791 L/μg. The methodology produced satisfactory results where the HSDM simulated the fixed-bed breakthrough with a coefficient of determination of 0.89, to the film diffusion coefficient (Kf) of 9 × 10−6 m/s and surface diffusion coefficient (Ds) of 3 × 10−16 m2/s. It was observed that the increase in EBCT promotes a reduction in the carbon use rate. The best carbon use rate found was 0.43 kg/m3 for a EBCT of 10 min and breakthrough time of 183.6 h.

A Review of Climate Change Impact Studies on Harmful Algal Blooms

The occurrence of harmful algal blooms (HABs) in coastal and inland waters has a significant impact on societies. This complex biogeophysical phenomenon becomes further complicated due to the impact of climate change. This review summarizes the research performed in recent years in the direction of climate change on three lake parameters, viz. lake temperature, precipitation, runoff, and lake ice, which impacts the lake ecology and, in turn, impacts the HABs. The present paper also reviews the research work related to the relationship between climate change and HABs. The purpose of this study is to provide the researchers with the opportunity to understand the current research in the direction of climate change and HABs so they can contribute effectively to one of the most important phenomena that will severely impact water quality in the future warmer climate, in coastal as well as inland water bodies. Furthermore, this work aims to discuss how HABs will change in the future warmer climate.

Daily Samples Revealing Shift in Phytoplankton Community and Its Environmental Drivers during Summer in Qinhuangdao Coastal Area, China

Rapid urbanization and economic development in coastal regions have significantly increased coastal nutrient pollution and remarkably changed the phytoplankton community and developed some species into bloom, resulting in large economic losses and serious threats to public health. Therefore, it is indispensable to reveal the shift in the phytoplankton community and phytoplankton abundance, and phytoplankton’s environmental drivers. However, previous studies could not present the details of the environmental drivers of phytoplankton due to samples being collected with low temporal resolution. Here, high-temporal-resolution (daily) samples were collected to investigate the influence of environmental factors on phytoplankton in Qinhuangdao for 44 days. Phytoplankton communities showed a rapid succession, with predominant genera changing in the order Skeletonema–Chaetoceros–Skeletonema–Thalassiosira. Similarly, Thalassiosira pacifica, Skeletonema costatum, Chaetoceros tortissimus, and Chattonella marina were identified as the dominant species and were abundant in 0–1.27 × 107 cells·L−1, 0–9.34 × 106 cells·L−1, 0–6.49 × 106 cells·L−1, and 0–3.64 × 106 cells·L−1, respectively. Moreover, inflows facilitate the rapid succession of the phytoplankton community. Dissolved inorganic phosphorus (DIP) was found to remarkably influence the succession of phytoplankton communities and the bloom of the top three dominant species, i.e., Thalassiosira pacifica, Skeletonema costatum, and Chaetoceros tortissimus. Overall, our results provide high-temporal-resolution observations of phytoplankton community succession and reveal its environmental drivers. This contributes to our current understanding of the occurrence of algae blooms and supports the development of management strategies to control algae bloom in coastal waters.

Disentangling the lifestyle of bacterial communities in tropical soda lakes

Microbial lifestyles may reveal niche-specific signatures and can contribute to detecting the effects of abiotic fluctuations on biogeochemical cycles. Microorganisms make a tradeoff between optimizing nutrient uptake, improving biomass yield, and overcoming environmental changes according to environmental hostility. Soda lakes are natural environments rich in carbonate and bicarbonate water, resulting in elevated pH and salinities that frequently approach saturation. We hypothesized that during the dry period (elevated pH and salinity), microorganisms try to overcome this harshness by allocating energy to the cellular maintenance process. As these environmental conditions improve during the wet period, microorganisms will begin to invest in nutrient uptake. To test this hypothesis, we evaluated four soda lakes in two different seasons by applying metagenomics combined with flow cytometry (estimate heterotrophic bacterial biomass). The natural occurrence of cyanobacterial blooms in some lakes is the main driver of carbon. These primary producers provide organic carbon that supports heterotrophic bacterial growth and, consequently, a high biomass yield. Under harsh conditions (dry season), cyanobacteria invest in nutrient uptake mechanisms, whereas heterotrophic bacteria allocate energy to survive at the expense of biomass yield. Lakes without cyanobacteria blooms invest in nutrient uptake independent of environmental hostility. This study clarifies the microbial tradeoffs in hostile environments and the impact of this choice on carbon and energy flux in tropical alkaline lakes.

Effects of Light and Temperature on the Metabolic Profiling of Two Habitat-Dependent Bloom-Forming Cyanobacteria.

Rapid proliferation of cyanobacteria in both benthic and suspended (planktonic) habitats is a major threat to environmental safety, as they produce nuisance compounds such as cytotoxins and off-flavors, which degrade the safety and quality of water supplies. Temperature and light irradiance are two of the key factors in regulating the occurrence of algal blooms and production of major off-flavors. However, the role of these factors in regulating the growth and metabolism is poorly explored for both benthic and planktonic cyanobacteria. To fill this gap, we studied the effects of light and temperature on the growth and metabolic profiling of both benthic (Hapalosiphon sp. MRB220) and planktonic (Planktothricoides sp. SR001) environmental species collected from a freshwater reservoir in Singapore. Moreover, this study is the first report on the metabolic profiling of cyanobacteria belonging to two different habitats in response to altered environmental conditions. The highest growth rate of both species was observed at the highest light intensity (100 μmol photons/m²/s) and at a temperature of 33 °C. Systematic metabolite profiling analysis suggested that temperature had a more profound effect on metabolome of the Hapalosiphon, whereas light had a greater effect in the case of Planktothricoides. Interestingly, Planktothricoides sp. SR001 showed a specialized adaptation mechanism via biosynthesis of arginine, and metabolism of cysteine and methionine to survive and withstand higher temperatures of 38 °C and higher. Hence, the mode of strategies for coping with different light and temperature conditions was correlated with the growth and alteration in metabolic activities for physiological and ecological adaptations in both species. In addition, we putatively identified a number of unique metabolites with a broad range of antimicrobial activities in both species in response to both light and temperature. These metabolites could play a role in the dominant behavior of these species in suppressing competition during bloom formation. Overall, this study elucidated novel insights into the effects of environmental factors on the growth, metabolism, and adaptation strategies of cyanobacteria from two different habitats, and could be useful in controlling their harmful effects on human health and environmental concerns.

Distribution of the Mesozooplankton Community in the Western Ross Sea Region Marine Protected Area During Late Summer Bloom

The spatio-temporal distributions of the epipelagic mesozooplankton community in the western Ross Sea region marine protected area (RSR MPA) were investigated. Mesozooplankton surveys were conducted in February 2018, January 2019, and March 2020 from an approximate depth of 200 m to address the essential environmental factors influencing the mesozooplankton community structure. Our results showed that the mesozooplankton community of the western RSR MPA could be affected by the various ecological factors, depending on their temporal and spatial variations. The community structure in 2018 was distinguished by its chlorophyll-a (Chl-a) concentration during the summer bloom phase in the late summer. Taxa observed in 2019 were divided into four significantly different groups according to the body size of the community composition. This differentiation could be derived from predation pressure, inducing a trophic cascade. Taxa in the 2020 samples were separated into five different groups based on temperature; during the 2020 survey, the water temperature was low and sea ice covered the whole continental shelf in the Ross Sea. Additionally, comparing the results from the three interannual surveys, although the communities clustered according to the survey period, the continental shelf groups were quite dissimilar despite overlapping geographically. Taken all together, the mesozooplankton community of the western RSR MPA changed according to changes in several ecological factors, such as temperature, Chl-a concentration, and predation pressure. The occurrence of summer blooms and the decline in water temperature mainly regulated the mesozooplankton community structure in the late summer.

Amination of Non-Functional Polyvinyl Chloride Polymer Using Polyethyleneimine for Removal of Phosphorus from Aqueous Solution

The eutrophication of freshwater environments caused by an excess inflow of phosphorus has become a serious environmental issue because it is a crucial factor for the occurrence of harmful algal blooms (HABs) in essential water resources. The adsorptive removal of phosphorus from discharged phosphorus containing effluents has been recognized as one of the most promising solutions in the prevention of eutrophication. In the present study, a polyvinyl chloride (PVC)-polyethyleneimine (PEI) composite fiber (PEI-PVC) was suggested as a stable and recoverable adsorbent for the removal of phosphorus from aqueous phases. The newly introduced amine groups of the PEI-PVC were confirmed by a comparison between the FT-IR and XPS results of the PVC and PEI-PVC. The phosphorus sorption on the PEI-PVC was pH dependent. At the optimum pH for phosphorus adsorption (pH 5), the maximum adsorption capacity of the PEI-PVC fiber was estimated to be 11.2 times higher (19.66 ± 0.82 mg/g) than that of conventional activated carbon (1.75 ± 0.4 mg/g) using the Langmuir isotherm model. The phosphorus adsorption equilibrium of the PEI-PVC was reached within 30 min at pH 5. From the phosphorus-loaded PEI-PVC, 97.4% of the adsorbed amount of phosphorus on the PEI-PVC could be recovered by employing a desorption process using 1M HCl solution without sorbent destruction. The regenerated PEI-PVC through the desorption process maintained a phosphorus sorption capacity almost equal to that of the first use. In addition, consistently with the PVC fiber, the PEI-PVC fiber did not elute any toxic chlorines into the solution during light irradiation. Based on these results, the PEI-PVC fiber can be suggested as a feasible and stable adsorbent for phosphorus removal.

Basin-scale distribution of salps and doliolids in the transition region of the North Pacific Ocean in summer: Drivers of bloom occurrence and effect on the pelagic ecosystem

The large-scale distribution of thaliaceans in relation to environmental variables was investigated over 4500 km in the transition region of the North Pacific (36°N–43.6° N, 141.5° E–164.5° W) in the summer of 2016–2019. Three main patterns occurred in the thaliacean bloom formations with specific and annual variabilities. Thalia democratica, the most dominant thaliacean species in this region, formed an intensive bloom (>100 ind m−3) of up to 300 km, mainly south of the subarctic boundary between 160° E and 180°. The bloom was accompanied by a dense water mass which was associated with high nutrient concentration and N/P ratio, indicating that this species thrived under the influence of the HNLC water mass from the subarctic region. A Dolioletta gegenbauri bloom was observed east of 180° and the north of the subarctic boundary in association with higher chlorophyll a levels. Doliolum denticulatum and Doliolum nationalis increased with sea surface temperature and pico-sized chlorophyll a, suggesting adaptation to oligotrophic subtropical waters. Estimated grazing and downward flux by Thalia democratica bloom corresponded to 63–80% and 20–26% of daily primary production, respectively, indicating that the bloom enhanced the biological pump in the HNLC-like environment dominated by small phytoplankton. Doliolids function as important components of the microbial food web through the consumption of varied organic matter. Thaliaceans utilise the specific niche which suspension-feeding copepods find difficult to colonise, indicating that bottom-up control of oceanographic conditions determines the mesozooplankton community and food-web structure in the transition region.