Algal Growth Research Articles

Coralline Algal Population Explosion in an Overgrazed Seagrass Meadow: Conditional Outcomes of Intraspecific and Interspecific Interactions

AbstractInteractions 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.

Bioremediation potential of microalgae for copper ion from wastewater and its impact on growth and biochemical contents: Equilibrium isotherm studies

Abstract In this study, the green microalgae Chloroidium ellipsoideum and Desmodesmus subspicatus were used to study copper uptake from nutrient media and its effect on algal growth and metabolism. The growth of C. ellipsoideum and D. subspicatus generally decreased with increasing copper concentrations. There was a decrease in the carbohydrate content of C. ellipsoideum , but an increase was observed in D. subspicatus by treatment with various copper concentrations. Low concentrations of copper helped to increase the protein content of C. ellipsoideum , but a decline in protein content was reported for D. subspicatus. By increasing the copper concentrations, an increase in the free amino acids and a decrease in the total lipid content of C. ellipsoideum and D. subspicatus were recorded. At 0.1 mgl–1,the maximum reduction of Cu2+ was 68.66% and 59.52% for C. ellipsoideum and D. subspicatus. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models were applied to describe the isothermal biosorption of Cu2+ ions in studied algae. The Dubinin–Radushkevich model indicated that the copper biosorption mechanism was physical in nature. Cu2+ has a greater affinity for D. subspicatus than C. ellipsoideum , suggesting that C. ellipsoideum was relatively more resistant to Cu2+ toxicity than D. subspicatus. FT-IR analysis revealed that carboxyl, amide, amino, carbonyl, hydroxyl, methyl and alkyl groups were the key groups responsible for the biosorption process. Therefore, D. subspicatus and C. ellipsoideum are efficient biosorbents for Cu2+ and can be used as biosorbents for heavy metals removal from wastewater.

Altered biotoxicity of cadmium to freshwater green algae by different concentrations of polystyrene

Microplastic pollution has become a global problem, threatening water bodies and aquatic organisms around the world. Heavy metal pollution in the aquatic environment is an environmental issue of long-term concern, and relatively few studies have been conducted on the compound toxic pollution of freshwater algae by microplastics and heavy metals. Therefore, in this study, Cd and polystyrene (PS) were selected as representative heavy metals and microplastics in the environment, and the toxic effects of the two pollutants on freshwater algae were investigated by determining the biomass of algal growth, chlorophyll a content, and the bioconcentration of heavy metals. It was found that the two pollutants alone could inhibit the growth and photosynthesis of the algae, and the toxicity increased with the increase of concentration. When the two pollutants were combined, the toxicity of Cd depended on the concentration of PS, and both low (1 mg/L) and high (100 mg/L) concentrations of PS increased the toxicity of Cd in a synergistic manner, whereas the medium concentration (10 mg/L) of PS showed an antagonistic effect, which was able to inhibit the toxicity of Cd.

Analysis of Meteorological Drivers of Taihu Lake Algal Blooms over the Past Two Decades and Development of a VOCs Emission Inventory for Algal Bloom

Cyanobacterial blooms represent a common environmental issue in aquatic systems, and these blooms bring forth numerous hazards, with the generation of volatile organic compounds (VOCs) being one of them. Global climate change has led to alterations in various climatic factors affecting algal growth, indirectly impacting the quantity of VOCs released by algae. With advancements in remote sensing technology, exploration of the spatiotemporal distributions of algae in large water bodies has become feasible. This study focuses on Taihu Lake, characterized by frequent occurrences of cyanobacterial blooms. Utilizing MODIS satellite imagery from 2001 to 2020, we analyzed the spatiotemporal characteristics of cyanobacterial blooms in Taihu Lake and its subregions. Employing the LightGBM machine learning model and the (SHapley Additive exPlanations) SHAP values, we quantitatively analyzed the major meteorological drivers influencing cyanobacterial blooms in each region. VOC-related source spectra and emission intensities from cyanobacteria in Taihu Lake are collected based on the literature review and are used to compile the first inventory of VOC emissions from blue-green algae blooms in Taihu Lake. The results indicate that since the 21st century, the situation of cyanobacterial blooms in Taihu Lake has continued to deteriorate with increasing variability. The relative impact of meteorological factors varies across different regions, but temperature consistently shows the highest sensitivity in all areas. The VOCs released from the algal blooms increase with the proliferation of the blooms, posing a continuous threat to the atmospheric environment of the surrounding cities. This study aims to provide a scientific basis for further improvement of air quality in urban areas adjacent to large lakes.

Metabolic relationships between marine red algae and algae-associated bacteria

AbstractMutualistic interactions between marine phototrophs and associated bacteria are an important strategy for their successful survival in the ocean, but little is known about their metabolic relationships. Here, bacterial communities in the algal sphere (AS) and bulk solution (BS) of nine marine red algal cultures were analyzed, and Roseibium and Phycisphaera were identified significantly more abundantly in AS than in BS. The metabolic features of Roseibium RMAR6-6 (isolated and genome-sequenced), Phycisphaera MAG 12 (obtained by metagenomic sequencing), and a marine red alga, Porphyridium purpureum CCMP1328 (from GenBank), were analyzed bioinformatically. RMAR6-6 has the genetic capability to fix nitrogen and produce B vitamins (B1, B2, B5, B6, B9, and B12), bacterioferritin, dimethylsulfoniopropionate (DMSP), and phenylacetate that may enhance algal growth, whereas MAG 12 may have a limited metabolic capability, not producing vitamins B9 and B12, DMSP, phenylacetate, and siderophores, but with the ability to produce bacitracin, possibly modulating algal microbiome. P. purpureum CCMP1328 lacks the genetic capability to fix nitrogen and produce vitamin B12, DMSP, phenylacetate, and siderophore. It was shown that the nitrogen-fixing ability of RMAR6-6 promoted the growth of P. purpureum, and DMSP reduced the oxidative stress of P. purpureum. The metabolic interactions between strain RMAR6-6 and P. purpureum CCMP1328 were also investigated by the transcriptomic analyses of their monoculture and co-culture. Taken together, potential metabolic relationships between Roseibium and P. purpureum were proposed. This study provides a better understanding of the metabolic relationships between marine algae and algae-associated bacteria for successful growth.

Tri-layered core-shell structured deferoxamine magnetic particles promote Microcystis aeruginosa growth

This experiment prepared magnetic composite siderophores (DMPs) with strong magnetism, excellent adsorption capacity, and high specific surface area. Exploring the synergistic effect of magnetic nanoparticles and siderophores on Microcystis aeruginosa growth under iron-deficient condition, by utilizing the characteristics of the three-layer core-shell structure of DMPs. This study elucidated the potential mechanism by which DMPs promote the cyanobacterial growth through physiological indicators and transcriptome analysis. On the experiment's final day, cell density in DMPs treatment group at 2, 4, and 8 mg/L were 1.10, 1.14 and 1.16 times higher than those in the control group (Ct), respectively. Similarly, chlorophyll and photosynthetic efficiency results showed improved algae growth with increasing DMPs dosage. The microcystin content in DMPs experimental groups at low, medium, and high concentration were 0.91, 0.86, and 0.83 times that of Ct, indicating alleviation of iron deficiency stress. Additionally, based on extracellular polymers, intracellular and extracellular siderophores, and visualization techniques, DMPs nanoparticles captured free iron sources in the environment, promoting algae growth by entering algal cells and facilitating the uptake and utilization of free iron ions from the solution. During the experiment, the iron uptake and transport genes (feoA and feoB) were significantly upregulated, whereas the algal siderophore synthesis gene (pchF) and the TonB-dependent transport system gene (TonB_C) were significantly downregulated, suggesting heightened activity in intracellular iron uptake and transport. This indicates an abundance of intracellular iron, eliminating the need for secrete siderophores to overcome iron deficiency. Microcystis aeruginosa increased iron bioavailability by using iron transported through DMPs in the environment while internalizing these DMPs. This study explored the mechanism of this synergistic effect to boost algal growth, and provided new ideas for elucidating the mechanism of cyanobacterial bloom outbreaks as well as the innovative application of biotechnology.

Land Use Impact on Water Quality and Phytoplankton Community Structure in Danjiangkou Reservoir

The composition and intensity of land use significantly influence the aquatic ecological environment, further affecting the physicochemical attributes of the water body, and indirectly modulating the phytoplankton community structure. This study centers around the Danjiangkou Reservoir, investigating the correlation between land use, water environment, and phytoplankton alongside varying intensities of anthropogenic activities, based on the review of land use, phytoplankton, and water quality data of 2021. Firstly, an analysis was conducted over five circular buffer zones generated around sampling points with radii set at 500 m, 1000 m, 1500 m, 2000 m, and 2500 m, wherein the intensity of human activity was categorized into low, medium, and high, in accordance with the human activity intensity level score (HAILS). This study proceeded to explore the correlation between land use and the water environment across different scales, compared phytoplankton density and community structure differences across varied levels of human activity, and analyzed the association between phytoplankton communities in the Danjiangkou Reservoir and environmental variables under various intensities. The findings showed: The land use within the 500 m circular buffer zone has the greatest impact on the water quality of the Danjiangkou Reservoir, especially with the increase in human activities leading to elevated nutrient levels in the water, thereby promoting the growth and reproduction of algae, and increasing the risk of algal blooms. This research scrutinizes the relationship between land use, water environment, and plankton under varying human activity intensities, serving as a foundation for environmental management sectors to make informed decisions and promote the sustainable development of the catchment water environment.

IoT ENBALED SMART AQUARIUM FOR MONITORING THROUGH SENSORS

The development of an IoT-enabled smart aquarium system offering real-time monitoring and automated control of crucial environmental parameters. The core of the system lies in the ESP8266 microcontroller, facilitating seamless internet connectivity and data processing. Water quality assessment is achieved through a turbidity sensor, detecting suspended particles indicative of potential pollution. Environmental conditions are monitored using a DHT11 sensor, providing data on both temperature and humidity – essential factors for maintaining a healthy habitat for specific fish species. For automated lighting control mimicking natural day/night cycles and preventing excessive algae growth, a Light-Dependent Resistor (LDR) is implemented. The LDR adjusts aquarium lighting based on ambient light levels. Finally, a relay module controls the operation of a water pump, ensuring optimal water circulation and distribution of nutrients throughout the aquarium. While an I2C LCD connected to an Arduino Nano provides local data visualization within the aquarium setup, the ESP8266 transmits sensor readings to a user-friendly platform accessible remotely through a mobile application or web interface. This allows for convenient real-time monitoring of water quality, temperature, humidity, and lighting conditions. The system can be further programmed to generate alerts when critical parameters deviate from the ideal range, enabling proactive user intervention to maintain a healthy environment. This project demonstrates the potential of IoT technology to create a more automated, efficient, and user-friendly system for maintaining a thriving aquatic ecosystem. KEYWORDS: IoT (Internet of Things), Smart Aquarium, ESP8266, Turbidity Sensor, DHT11 Sensor, LDR(Light-Dependent Resistor), Relay Module, Water Pump, I2C LCD, Arduino Nano, Real-Time Monitoring, Automated Control, Remote Access, Mobile Application, Web Interface, Water Quality, Temperature, Humidity, Light Control, Aquatic Environment.

Si-doped (AlGa)2O3 growth on a-, m- and r-plane α-Al2O3 substrates by molecular beam epitaxy

We reported the growth of (AlGa)2O3 layers on (11 2¯ 0), (10 1¯ 0), and (10 1¯ 2) α-Al2O3 substrates using MBE, and the electrical characterization of Si-doped (AlGa)2O3 layers. The Ga2O3 layers grown on (10 1¯ 0) and (10 1¯ 2) α-Al2O3 were α-phase single crystals, while the Ga2O3 layer grown on (11 2¯ 0) α-Al2O3 consisted of (11 2¯ 0) α-Ga2O3 and ( 2¯ 01) β-Ga2O3. The Al composition of the (11 2¯ 0) and (10 1¯ 0) (AlGa)2O3 layers was controlled by varying the Al flux. The Si-doped (10 1¯ 0) α-(Al x Ga1-x )2O3 layers with x = 0–0.41 were electrically conducting.

Phosphorus depletion is exacerbated by increasing nitrogen loading in the Bohai sea

Phosphorus (P) is an essential nutrient for algal growth in nearshore ecosystems. In recent years, there has been a shift in nutrient dynamics in nearshore areas, leading to an exacerbation of P limitation, although the underlying mechanisms remain unclear. This study analyzed the P species and budget in the Bohai Sea (BS) from 2011 to 2020, aiming to explore the intrinsic mechanisms of P limitation in the BS. The results show that the main external source of P in the BS was river transport (89%), and the primary fate of P was burial (96%) into the sediment. Due to excessive nitrogen (N) input and biological processes in the BS, the P budget in the BS is unbalanced, resulting in an increase in the N/P ratio, particularly in nearshore areas. Nearshore areas typically have lower concentrations of dissolved inorganic P (DIP) in the water and higher concentrations of reactive P (Reac-P) in the sediments. This pattern is particularly evident in Bohai Bay and the northwest nearshore region, where harmful algal blooms occur frequently. To cope with enhanced P limitation, the biologically driven P regeneration and cycling processes within the BS are accelerated. From 2011 to 2020, the concentration of DIP in the BS during autumn increased, while the content of Reac-P in sediments slightly decreased. Historical data indicate that P depletion in the BS is intensifying and expanding, primarily due to N enrichment and algal production. N enrichment alters the structure and composition of primary production, potentially exacerbating P depletion in the BS. Excessive N may have significant impacts on the P pool, potentially influencing the stability of future coastal ecosystems.

Growth, nutrient removal, and lipid productivity promotion of Chlorella sorokiniana by phosphate solubilizing bacteria Bacillus megatherium in swine wastewater: Performances and mechanisms

Effects of a phosphorus-solubilizing bacteria (PSB) Bacillus megatherium on growth and lipid production of Chlorella sorokiniana were investigated in synthesized swine wastewater with dissolved inorganic phosphorus (DIP), insoluble inorganic phosphorus (IIP), and organic phosphorus (OP). The results showed that the PSB significantly promoted the algal growth in OP and IIP, by 1.10 and 1.78-fold, respectively. The algal lipid accumulation was also greatly triggered, respectively by 4.39, 1.68, and 1.38-fold in DIP, IIP, and OP. Moreover, compared with DIP, OP improved the oxidation stability of algal lipid by increasing the proportion of saturated fatty acids (43.8 % vs 27.9 %), while the PSB tended to adjust it to moderate ranges (30.2–41.6 %). Further, the transcriptome analysis verified the OP and/or PSB-induced up-regulated genes involving photosynthesis, lipid metabolism, signal transduction, etc. This study provided novel insights to enhance microalgae-based nutrient removal combined with biofuel production in practical wastewater, especially with complex forms of phosphorus.

Green Synthesis and Characterization of CaO Nanoparticles using Hen Eggshells and its Impact on Biomass Concentration, Chlorophyll-a and Lipid Content of Chlorella sp.

Biodegradable wastes e.g. the outer cover of a boiled hen egg generally haphazardly discarded by humans in different locations of the country and generates problems for the local creatures. Although different researchers reported different methods to utilize the waste through the nanotechnological approach. Here, green synthesis of calcium oxide (CaO) nanoparticles from the hen eggshells was  carried out and characterized them by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectrophotometer (UV). Further application of the synthesized nanoparticles was done on Chlorella sp. to investigate the impact on algal growth, lipid and chlorophylls. Synthesized CaO nanoparticles were applied in different concentration (0, 10, 20 and 30 mg L–1) and readings were monitored for 20 days. The highest biomass concentration 242.56 mg L–1 was achieved for the nanoparticle concentration of 20 mg L–1 and the lipid content increased up  to 35.71% in 20 mg L–1. These results pave the way for enhanced algal biofuel production. 

Atlas of phytoplankton phenology indices in selected Eastern Mediterranean marine ecosystems.

Phytoplankton is a fundamental component of marine food webs and play a crucial role in marine ecosystem functioning. The phenology (timing of growth) of these microscopic algae is an important ecological indicator that can be utilized to observe its seasonal dynamics, and assess its response to environmental perturbations. Ocean colour remote sensing is currently the only means of obtaining synoptic estimates of chlorophyll-a (a proxy of phytoplankton biomass) at high temporal and spatial resolution, enabling the calculation of phenology metrics. However, ocean colour observations have acknowledged weaknesses compromising its reliability, while the scarcity of long-term in situ data has impeded the validation of satellite-derived phenology estimates. To address this issue, we compared one of the longest available in situ time series (20 years) of chlorophyll-a concentrations in the Eastern Mediterranean Sea (EMS), along with concurrent remotely-sensed observations. The comparison revealed a marked coherence between the two datasets, indicating the capability of satellite-based measurements in accurately capturing the phytoplankton seasonality and phenology metrics (i.e., timing of initiation, duration, peak and termination) in the studied area. Furthermore, by studying and validating these metrics we constructed a satellite-derived phytoplankton phenology atlas, reporting in detail the seasonal patterns in several sub-regions in coastal and open seas over the EMS. The open waters host higher concentrations from late October to April, with maximum levels recorded during February and lowest during the summer period. The phytoplankton growth over the Northern Aegean Sea appeared to initiate at least a month later than the rest of the EMS (initiating in late November and terminating in late May). The coastal waters and enclosed gulfs (such as Amvrakikos and Maliakos), exhibit a distinct seasonal pattern with consistently higher levels of chlorophyll-a and prolonged growth period compared to the open seas. The proposed phenology atlas represents a useful resource for monitoring phytoplankton growth periods in the EMS, supporting water quality management practices, while enhancing our current comprehension on the relationships between phytoplankton biomass and higher trophic levels (as a food source).

Seasonal effects and trophic pressure shape the responses of species interactions in a tropical seagrass meadow to marine heatwaves

Species interactions are influenced by changes to the environment, such as seasonal variations in temperature, and human‐driven warming including marine heatwaves (MHWs). Alteration of species interactions, particularly those involving foundation species, can shape ecosystem structure, stability and dynamics. Marine habitats, notably seagrass meadows, are threatened by human‐driven environmental changes including MHWs which have the potential to alter trophic interactions through effects on various community members including seagrasses, epiphytic algae, and epiphytic algae grazers. Here we examined the effects of a simulated marine heatwave (control versus + 4°C) in different seasons and grazer occurrence on seagrass traits, epiphytic algae growth, grazer biomass and grazing rate. We found the season in which the MHW occurred affected the seagrass response and grazer influence. In winter, the MHW had positive effects on seagrass growth and nitrogen content and caused significant decreases in epiphytic algae growth. However, in summer, grazer presence increased seagrass growth and biomass, but growth was reduced by the interaction with the MHW. The season in which the MHW occurred affected the magnitude of change in leaf tissue isotopic values and C:N ratio, with greater changes occurring in summer. Epiphytic algal growth was markedly reduced by the interaction between all three factors, leading to the near lack of epiphyte growth in summer with grazers present under the MHW. Summer was also associated with a greater increase in snail biomass (most notably under MHW conditions), and increased snail grazing rate. From these results, we show that winter MHWs can drive increased growth of seagrasses but minimal impacts on grazers, while in summer increased grazer activity can interact with elevated temperatures from a MHW to increase their algal consumption. By examining responses across multiple trophic levels and distinct seasons, we achieve a more representative and realistic depiction of human‐induced environmental impacts on ecosystems.

A high throughput array microhabitat platform reveals how light and nitrogen colimit the growth of algal cells

A mechanistic understanding of algal growth is essential for maintaining a sustainable environment in an era of climate change and population expansion. It is known that algal growth is tightly controlled by complex interactive physical and chemical conditions. Many mathematical models have been proposed to describe the relation of algal growth and environmental parameters, but experimental verification has been difficult due to the lack of tools to measure cell growth under precise physical and chemical conditions. As such, current models depend on the specific testing systems, and the fitted growth kinetic constants vary widely for the same organisms in the existing literature. Here, we present a microfluidic platform where both light intensity and nutrient gradients can be well controlled for algal cell growth studies. In particular, light shading is avoided, a common problem in macroscale assays. Our results revealed that light and nitrogen colimit the growth of algal cells, with each contributing a Monod growth kinetic term in a multiplicative model. We argue that the microfluidic platform can lead towards a general culture system independent algal growth model with systematic screening of many environmental parameters. Our work advances technology for algal cell growth studies and provides essential information for future bioreactor designs and ecological predictions.

Microalgal-bacterial treatment of ice-cream wastewater to remove organic waste and harvest oil-rich biomass.

The diversity of microalgae and bacteria allows them to form beneficial consortia for efficient wastewater treatment and nutrient recovery. This study aimed to evaluate the feasibility of a new microalgal-bacterial combination in the treatment of ice cream wastewater for biomass harvest. The bacterium Novosphingobium sp. ICW1 was natively isolated from icecream wastewater and the microalga Vischeria sp. WL1 was a terrestrial oil-producing strain of Eustigmatophyceae. The ice cream wastewater was diluted 4 folds for co-cultivation, which was relatively less inhibitory for the growth of Vischeria sp. WL1. Four initial algal-bacterial combinations (v:v) of 150:0 (single algal cultivation), 150:1, 150:2, and 150:4 were assessed. During 24days of co-cultivation, algal pigmentation was dynamically changed, particularly at the algal-bacterial combination of 150:4. Algal growth (in terms of cell number) was slightly promoted during the late phase of co-cultivation at the combinations of 150:2 and 150:4, while in the former the cellular oil yield was obviously elevated. Treated by these algal-bacterial combinations, total carbon was reduced by 67.5 ~ 74.5% and chemical oxygen demand was reduced by 55.0 ~ 60.4%. Although single bacterial treatment was still effective for removing organic nutrients, the removal efficiency was obviously enhanced at the algal-bacterial combination of 150:4. In addition, the harvested oils contained 87.1 ~ 88.3% monounsaturated fatty acids. In general, this study enriches the biotechnological solutions for the sustainable treatment of organic matter-rich food wastewater.

الآثار البيئية والاقتصادية والاجتماعية لظاهرة المد الأحمر على مجتمع الصيادين في ولاية بركاء بسلطنة عمان

Red tide is not a recent phenomenon. Rather, it is linked to the development and bloom of plankton and phytoplankton that accompanied ancient geological times and climate changes. Japan is the first country that was able to monitor this phenomenon more than 300 years ago, while its appearance in the countries of the Arabian Peninsula was in 1976 in the Sultanate of Oman. Natural and human factors contribute to the growth of harmful algae, which is the main cause of red tide, especially Dinotlagellates, which represents 78% of the samples analyzed in the Sultanate of Oman. Red tides damage ecosystems and coastal communities. This study mainly aims to highlight the economic, social and environmental impacts of the red tide phenomenon on the fishing community in the Wilayat of Barka in the Sultanate of Oman, and to develop appropriate solutions for fishing communities to mitigate the negative effects of this phenomenon. The study relied in its methodology on a review of previous studies, a field study, and direct interviews with fishermen in Barka State, in addition to questionnaires distributed to 120 fishermen using a random sampling method. One of the most prominent findings of this study is that red tide directly causes air pollution through the spread of unpleasant odors in the region, according to 99% of the sample population. However, what should be noted is that fishermen are completely unaware of the effects of red tide on public health related to the possibility of fish poisoning. As to the economic impacts, 94% of the study population pointed out to cost of cleaning equipment used in the fishing process. The problem was compounded by expatriate workers exploitation of situation by raising the costs of cleaning. Among the most prominent recommendations that came out of the study: conducting further studies and research, raising awareness on negative impacts of red tide and establishing fishermen associations to mitigate the effects of red tide.

Evaluation of metrics and thresholds for use in national-scale river harmful algal bloom assessments

The spatiotemporal distribution of harmful algal blooms (HABs) in rivers remains poorly understood, and there is an urgent need to develop a consistent set of metrics to better document HAB occurrences and forecast future events. Using data from seven sites in the Illinois River Basin, we computed metrics focused on HAB conditions related to excess algal growth and hypoxia. Daily mean chlorophyll and dissolved oxygen (DO) concentrations, gross primary productivity (GPP), and net ecosystem productivity (NEP) rates, focused on water quality status, identifying the timing of the transition from a clear-water to an algal dominated state. Early warning indicators (EWIs), the first-order autoregressive process (Ar1) and standard deviation (SD) of chlorophyll concentrations, focused on future events, forecasting blooms. Metrics were compared to either literature-derived or statistical-based thresholds and were normalized by total number of daily samples for an exceedance rate. Exceedances of a daily mean chlorophyll concentration averaged 50 % across all sites using a 10 µg L−1 threshold but increasing the threshold to 50 μg L−1 reduced the average exceedance rate to 5 %. The average exceedance rate for GPP (∼8 g O2 m2d−1 threshold) was 15 %, similar to the daily amplitude DO concentration (∼3 mg L−1 threshold), but the average for NEP (0 g O2 m2 d−1 threshold) was higher, at 28 %. The number of days with at least 1 continuous DO concentration below the threshold of 5, 3, or 2 mg L−1, had basin wide exceedance rates of 9 %, 3 %, and 2 %, respectively. Thresholds for EWIs, Ar1 and SD, were exceeded at 5 of the 7 sites with high chlorophyll concentrations and GPP rates. The correlation between proxies for algal biomass (chlorophyll concentration) and productivity (GPP) was strongest for sites in the middle region of the basin, with R2 values between 0.54 and 0.74. Although, cyanotoxin concentrations are the most commonly used metrics by states to define an inland water HAB, there is a paucity of publicly available data. The wider availability of chlorophyll and oxygen data combined with the results from this study suggest that biomass and productivity state and event-based metrics may be a promising way to assess and predict the vulnerability of rivers to some of the deleterious effects of HABs at broad spatial scales.

The phycosphere and its role in algal biofuel production

Oleaginous microalgae have become a focus for large-scale biofuel production due to their ability to accumulate large quantities of lipids. However, production is currently limited by cost and predation. At present, algal biofuel cultivation is optimized through starvation, supplementing media with nutrients, or genetic engineering; these methods can often be costly with little to no increase in lipid production or the culture’s defense. Investigating the phycosphere of algal-bacterial interactions may overcome these current barriers to large-scale production. The phycosphere of algal-bacterial interactions have formed over millions of years through mutualistic and symbiotic relationships and can provide a more direct source of nutrients compared to adding the nutrients in bulk. The most promising of these interactions include the production of phytohormones and quorum signaling compounds that alter the behaviors of the consortia. Phytohormones can improve algal growth rates, lipid production, and stress resistance. Quorum signaling could create consortia capable of warding off invaders—such as rotifers—while self-regulating and altering behavior based on population density. Mechanisms within the algal phycosphere present many opportunities for the development of novel engineering strategies to further improve algal lipid production and operational costs. This review outlines previous preliminary phycosphere research as well as posing possible opportunities to be pursued in future biofuel production.

Physiological responses of the microalgae Thalassiosira weissflogii to the presence of the herbicide glyphosate in the medium.

We evaluated changes in growth, chlorophyll fluorescence and basic physiological and biochemical parameters of the microalgae Thalassiosira weissflogii cells under the influence of the herbicide glyphosate in concentrations 0, 25, 95 and 150μgL-1 . The toxic effect of glyphosate on algae is weakly dependent on the level of cell mineral nutrition. High concentrations of the herbicide do not lead to the death of microalgae but block the process of algae cell division. An increase in the glyphosate concentration in the medium leads to a slowdown or stop of algal growth, a decrease in their final biomass, an increase in the production of reactive oxygen species (ROS), depolarisation of mitochondrial membranes and metabolic activity of algae. Glyphosate inhibits the photosynthetic activity of cells and inhibits the relative rate of electron transport in the photosynthetic apparatus. Glyphosate at the studied concentrations does not affect the size characteristics of cells and the intracellular content of chlorophyll in T. weissflogii . The studied herbicide or products of its decay retain their toxic properties in the environment for at least 9days. This result shows the need for further in-depth studies to assess the physiological response and possible acclimation changes in the functional state of oxygenic phototrophs in response to the herbicide action. The species specificity of microalgae to the effects of glyphosate in natural conditions is potentially dangerous due to a possible change in the species structure of biocoenoses, in particular, a decrease in the contribution of diatoms.