Algal Growth Dynamics Research Articles

Endometabolic profiling of pigmented glacier ice algae: the impact of sample processing

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

Combatting cyanobacteria: unraveling the potency of 316L-Cu stainless steel in inhibiting Microcystis aeruginosa growth.

Harmful algal blooms, particularly those of Microcystis aeruginosa, present significant ecological and health risks. To address this issue, this study utilized a custom static algal growth assessment apparatus to investigate the anti-algal performance of a copper-alloyed 316L stainless steel (SS), named 316L-Cu SS. This material was compared with traditional 316L SS, which is widely utilized in freshwater systems for its corrosion resistance. Algal growth dynamics were monitored through optical density (OD) and chlorophyll A concentration measurements. Notably, 316L-Cu SS exhibited superior inhibitory effects on Microcystis aeruginosa growth compared to 316L SS and control groups. Inductively coupled plasma mass spectrometry (ICP-MS) confirmed that the copper ion release from 316L-Cu SS played a critical role in this algal suppression, which interfered with photosynthesis, induced oxidative stress, and damaged algal cell membranes. In contrast, other metal ions (Ni, Cr, Fe) had a negligible impact on algal growth. The study highlights 316L-Cu SS as a promising material for mitigating harmful algal blooms, thereby offering potential benefits for both aquatic ecosystem conservation and public health protection.

A low-cost edge AI-chip-based system for real-time algae species classification and HAB prediction

Harmful Algal Blooms (HAB) are damaging to ecosystem functions and pose challenges to environmental and fisheries management. The key to HAB management and understanding the complex algal growth dynamics is the development of robust systems for real-time monitoring of algae populations and species. Previous algae classification studies mainly rely on the combination of an in-situ imaging flow cytometer and an off-site lab-based algae classification model such as Random Forest (RF) for the analysis of high-throughput images. An on-site AI algae monitoring system on top of an edge AI chip embedded with the proposed Algal Morphology Deep Neural Network (AMDNN) model is developed to achieve real-time algae species classification and HAB prediction. Based on a detailed examination of real-world algae images, dataset augmentation is first performed: consisting of orientation, flipping, blurring, and Resizing with Aspect ratio Preserved (RAP). The dataset augmentation is shown to significantly improve classification performance which is superior to that of the competitive RF model. And the attention heatmaps show that for relatively regular-shaped algal species (e.g., Vicicitus), the model weights the color and texture information heavily; while the shape-related features are more important for complex-shaped algae (e.g., Chaetoceros). The AMDNN is tested on a dataset of 11,250 algae images containing the 25 most common HAB classes in Hong Kong subtropical waters with 99.87% test accuracy. Based on the fast and accurate algae classification, the AI-chip-based on-site system is applied to a one-month dataset in February 2020; the predicted trends of total cell counts and targeted HAB species counts are in good agreement with observations. The proposed edge AI algae monitoring system provides a platform for the development of practical HAB early warning systems that can effectively support environmental risk and fisheries management.

High-value lipids accumulation by Pavlova pinguis as a response to nitrogen-induced changes

The challenges of exploring the potential of microalgal strains for biotechnological applications include the optimization of their cell growth and chemical composition. To overcome this, it is essential to understand the mechanisms that lead to the accumulation of desired products within microalgal cells. In this study, a gradient of nitrogen as nitrate (NO3−−N) concentrations was used for the preparation of P. pinguis growth medium. The algal growth dynamics, pigments, nutrient uptake, and detailed lipid composition across treatments were assessed. Increasing the NO3−−N level led to higher lipid content (21%), a higher cell uptake rate (0.20 pg NO3−−N cell−1 d−1) and more accumulation of chlorophylls, carotenoids, and high-value lipids. Eicosapentaenoic acid, essential fatty acids, phytol and stigmasterol were the key high-value lipids that were positively influenced by higher NO3−−N levels. High NO3−−N conditions induced an increase of 54% in total sterol content, while low NO3−−N conditions resulted in increased proportions of saturated fatty acids (66% more) and decreased proportions of polyunsaturated fatty acids (14% less). The low NO3−−N level also led to higher amounts of monoglyceride (1.60 mg g−1; 64% more). The analysis of P. pinguis lipids before and after hydrolysis provided an insight into the composition of the esterified lipids across treatments. NO3−−N supplementation was revealed to be an effective strategy for enhancing P. pinguis lipid composition, for nutraceutical and pharmaceutical industries (high NO3−−N level). A greater understanding of the NO3−−N uptake and the use efficiency by P. pinguis was reached, showing its potential for further biotechnological applications.

A comprehensive mechanistic model for simulating algal growth dynamics in photobioreactors

A comprehensive mechanistic model for describing algal growth dynamics in a photobioreactor was developed in this work with state of the art understanding and realistic assumptions for major associated processes. The model included 27 state variables related to various algal processes. This model was validated with extensive experimental data obtained from independent growth experiments in batch reactors, and was able to simulate system performance reasonably well. The comprehensive nature of the formulation also highlights the complex inter-relationship between all processes, and provides a tool for gaining more systematic insights into algal behavior in photobioreactors and other such systems.

The color of mass culture: spectral characteristics of a shallow water column through shade-limited algal growth dynamics(1).

It is envisioned that mass algal cultivation for commercial biofuels production will entail the use of large raceway pond systems, which typically have shade-limited photosynthetic growth within depths of 20-30cm. The attenuation of light and spectral qualities of red, green, and blue wavelengths in a 20-cm water column as a function of Chl-a concentration during exponential and linear phases of growth dynamics for the marine diatom Thalassiosira pseudonana was examined under laboratory conditions. While photosynthetically available radiation (PAR) was in excess throughout the water column during the phase of exponential growth, PAR became rate limiting differently for red, green, and blue wavelengths during the phase of linear growth. The transition from exponential to linear growth occurred at 1-2mg Chl-a·L-1, whereby a scalar ~5μmol photons·m-2·s-1 at 20-cm depth was found to occur as would be anticipated having the compensation point for where rates of photosynthesis and respiration are equal. During the phase of linear growth, red wavelengths became increasingly dominant at depth as Chl-a concentrations increased, being contrary to the optical conditions for those natural bodies of water that forced the evolution of phytoplankton photosynthesis. It is hypothesized this dramatic difference in water column optics between natural and synthetic environments could influence a variety of biological reactions, importantly non-photochemical quenching capacities, which could negatively impact crop yield.

A cumulative eutrophication risk evaluation method based on a bioaccumulation model

Water pollution problems related to rapid economic development have received considerable attention in recent years, and water eutrophication has become one of the greatest threats to aquatic environments around the world. In this study, we introduce a eutrophication risk assessment method to address the urgent need for simple but effective modeling tools to support environmental management. This method is based on a bioaccumulation model and algal growth dynamics. The water eutrophication risk is expressed by the ratio of the algal concentration in a water body and the critical algal concentration for eutrophication. The combined and cumulative effects of meteorological factors (e.g., temperature and light intensity), water quality factors (e.g., TN, TP, and NH3-N), and biological factors (e.g., algal settlement and normal death) on eutrophication are considered. We examine the advantages of our eutrophication risk assessment model using the seasonal, mesotrophic Xikeng Reservoir (Shenzhen City, China) as a case study and analyze three typical sets of meteorological and water quality conditions. Prior parameter distributions were chosen based on both a literature survey and experimental research. The results indicate that the combined actions of multiple external factors have a long impact on the eutrophication risk of the Xikeng Reservoir. Eutrophication was observed on the 6th day of the simulation time in the Xikeng Reservoir under the influence of higher temperature (T=28.3°C), higher light intensity (I=6037lx), and higher pollutants concentration (CTN=5.40mg/L, CTP=0.391mg/L, CNH3-N=4.18 mg/L). These findings indicate that Xikeng Reservoir influence by similar environmental conditions should receive more of our attention to prevent eutrophication. Finally, we highlight the benefits of the new eutrophication risk assessment model, including its simple calculation process, reduced parameter set, and accurate prediction of eutrophication tendency. These features make the model perfectly suited for stakeholders and policy makers who need to make risk management assessment of environmental water, especially for the environmental management of areas where data are unavailable.

Carbohydrate-degrading bacteria closely associated with Tetraselmis indica: influence on algal growth

This investigation was conducted in order to examine the interactions between an algal species, Tetraselmis indica (a new species described, manuscript under consideration elsewhere), collected in the wild and strains of bacteria with which it is closely associated. Three bacterial strains were isolated and sequence analysis of the 16S rDNA indicated that the organisms belonged to the genera Pseudomonas, Acinetobacter and Ruegeria. Morphologies of the bacterial strains were studied using epifluorescence microscopy and scanning electron microscopy. Re-association experiments were conducted with axenic cultures inoculated with the three bacterial strains in concentrations comparable to natural conditions, and the effect of each bacterial population on the growth of T. indica was determined. Tetraselmis indica exhibited differential growth success with the various bacterial cultures, and in particular Acinetobacter sp. was observed to promote growth of the algae. These experiments revealed that microbes associated with the alga differentially influence algal growth dynamics. Bacterial presence on the cast off cell wall products of alga suggested the likely utilisation of algal cell wall by bacteria. The bacterial strains were tested for carbohydrate metabolism using various sugars and screened for carbohydrase activity. Bacterial strains were found to produce carbohydrases for degradation of polysaccharides generally present in the cell wall of T. indica (glucans, galactans, galactomannans and pectins), whereas no such utilisation was observed for other wall substrates such as cellulose, arabinoxylan, rhamnogalacturonan). The Pseudomonas sp. and the Acinetobacter sp. showed carbohydrase activity with Glucans, galactans, galactomannans and pectin, whereas the Ruegeria sp. showed much less carbohydrase activity and only with pectin. The carbohydrate utilisation studies using artificial substrates suggested the potential utilisation of cast-off algal cell wall products.

Diel patterns of algae and water quality constituents in the San Joaquin River, California, USA

The San Joaquin River (SJR) is a hypereutrophic river that contributes to hypoxia in the downstream Stockton Deep Water Ship Channel. Oxidizable materials, in the form of algal biomass from upstream sources, contribute to the hypoxic conditions, especially from July to October. Our earlier work demonstrated the existence of strong chlorophyll- a diel cycles which complicated the calculation of algal loads for the watershed-scale monitoring program, necessary to address the total maximum daily load (TMDL) for dissolved oxygen (DO). The purpose of this study was to determine if diel patterns existed for other water quality constituents, and to determine the role of algal growth dynamics in driving these diel changes. Studies conducted between 30 June and 15 October 2004 evaluated temporal changes for several water quality constituents over four, 48 h studies at two sites along the mainstem of the SJR. Strong diel (24 h) patterns were observed for chlorophyll- a and pheophytin- a (algal pigments), temperature, DO, pH, dissolved inorganic nitrogen (DIN, NH 4 +-N + NO 3 −-N), soluble reactive phosphorus (SRP), and volatile suspended solids (VSS). Patterns of DIN and SRP were inverse of those observed for algal pigments, temperature, DO, pH, and VSS. The observed diel patterns of algal pigments and temperature were greater in the beginning of the summer (June/July) and diminished by the end of summer (September/October) due to the decreased photoperiod. Within a 24 h period the fluctuations observed in algal pigments and nutrients suggest that growth of algae during daylight hours and depletion at night are largely responsible for the observed diel patterns. Due to the observed diel variability in these water quality constituents, the samples collected for TMDL programs may not be representative unless samples are collected at the daily mean for a system.

Nutrient Bioassays of Growth Parameters for Algae in the North Bosque River of Central Texas1

Abstract: Nutrient dose‐response bioassays were conducted using water from three sites along the North Bosque River. These bioassays provided support data for refinement of the Soil and Water Assessment Tool (SWAT) model used in the development of two phosphorus TMDLs for the North Bosque River. Test organisms were native phytoplanktonic algae and stock cultured Pseudokirchneriella subcapitata (Korshikov) Hindak. Growth was measured daily by in vivo fluorescence. Algal growth parameters for maximum growth (μmax) and half‐saturation constants for nitrogen (KN) or phosphorus (KP) were determined by fitting maximum growth rates associated with each dose level to a Monod growth rate function. Growth parameters of native algae were compared between locations and to growth parameters of P. subcapitata and literature values. No significant differences in half‐saturation constants were indicated within nutrient treatment for site or algal type. Geometric mean KN was 32 μg/l and for KP 7 μg/l. A significant difference was detected in maximum growth rates between algae types but not between sites or nutrient treatments. Mean μmax was 1.5/day for native algae and 1.2/day for stock algae. These results indicate that watershed‐specific maximum growth rates may need to be considered when modeling algal growth dynamics with regard to nutrients.

Integrated water quality management in Tolo Harbour, Hong Kong: a case study

Tolo Harbour is an almost land-locked semi-enclosed sea inlet with a narrow outlet in the South China Sea. With the rapid growth in economic development and urbanization, evidence of increasing eutrophication is seen by the drastic increase in the severity and frequency of algae blooms, which are closely correlated to the excessive nutrient loading. The bottom waters in Tolo Harbour exhibit serious dissolved oxygen depletion. A co-ordinated sequence of pollution control activities are being undertaken by the Hong Kong Government. Technological advances can be utilized in effective water quality management in the coastal zone. This paper presents the application of a robust three-dimensional numerical eutrophication model, integrating hydrodynamics with water quality, for simulation of the algal growth dynamics and water quality processes. After calibration and verification, the tool is used to predict different eutrophication scenarios as well as the effectiveness of alternative management solution strategies.

FUNDAMENTAL STUDY ON APPLICATION OF THEORY OF POPULATION DYNAMICS TO HABITAT EVALUATION METHOD

Population dynamics is one of the important topics of ecology. It has been employed to simulate changing situation of living species by using mathematical models. Today, it is introduced to the field of environmental engineering. By the way, there is another model that discuss about habitat evaluation method in the river engineering. Each of the models has been progressed individually.In this study, we tried to innovate the population dynamics to develop the habitat evaluation method. By discussing about the dynamics of algal growth and the habitat suitability of algae in the middle reach of the Yahagi River, we may identify the theory of population dynamics as one of the necessary viewpoints for habitat evaluation.

Depth-averaged, two-dimensional eutrophication modelling for Tolo Harbour, Hong Kong

A depth-averaged 2-D finite-difference numerical modelling for eutrophication in coastal waters, based upon a numerically generated boundary-fitted orthogonal curvilinear grid system, is developed. The present eutrophication model is run simultaneously with a hydrodynamic model to capture advection and diffusion due to tidal flow. A grid “block” technique is employed to handle the areas submerged intermittently. The model simulates the transport and transformation of up to nine water quality constituents associated with eutrophication in the waters. Some kinetic coefficients are calibrated with the measured data in Tolo Harbour, Hong Kong. Descriptive inputs for Sediment Oxygen Demand (SOD) and nutrient releases from sediment, based on relevant in situ sampling analysis, are used. The computed results are compared with other long-term field data in Tolo Harbour. It shows that the computational results by the present model agree with the field data well, i.e., the present model could reasonably describe the depth-averaged algal growth dynamics and water quality time-variations in Tolo Harbour.

Water Quality Model for Mariculture Management

In marine fish farms located in subtropical eutrophic coastal waters, the dissolved oxygen (DO) level is often intimately related to algal growth dynamics. For effective mariculture management, a simple, tractable model that can elucidate the dependence of water quality on the important hydrographic, meteorological, and ecological parameters is required. A quasisteady water quality model is formulated herein to predict the long-term (seasonal) average concentrations of phytoplankton, organic nitrogen, dissolved inorganic nitrogen, and potential dissolved oxygen drop (PDOD) for fish farms located in weakly flushed tidal embayments. The fish culture zone is treated as a completely mixed nitrogen-limited system in which algal carbon is decomposed and nutrients regenerated continuously. The model assumes Monod-growth type relations for algal growth and nutrient uptake and incorporates algal settling and respiration, and tidal flushing. Using realistic estimates of light and temperature limiting factors and kinetic rate coefficients, model predictions of seasonally averaged water quality and qualitative features are well supported by field data.

Effects of nitrogen fertilizer and pesticide management on floodwater ecology in a wetland ricefield

This paper is the first in a series reporting a study on the effects of N fertilizer, green manure, and pesticide applications on the floodwater ecology of a tropical ricefield. Algal, zooplankton, and mollusc popu- lations were monitored during a crop cycle in plots sub- jected to various methods of N management and differ- ent pesticide regimes. This paper presents the experimen- tal design, general features of the statistical methods for data analysis, and the dynamics of algal growth in the floodwater. Transient green algal blooms and increases in floodwater dissolved O2 concentrations were observed after the broadcast application of N fertilizer 7 days after transplanting. These effects were less pronounced after the second N application 55 days after transplanting. Photosynthetic activity in the floodwater of planted plots decreased as the crop season progressed. Mucilaginous colonial blue-green algae proliferated in the zero-N con- trol and unplanted plots, but were inhibited by the broad- cast N fertilizer and green manure incorporation. Deep placement of urea supergranules reduced the negative im- pact of N fertilizer on blue-green algal populations. There was limited evidence that the application of pesticides promoted the development of blue-green algal popula- tions in the absence of readily available N.

BOUNDARIES OF ECOLOGICAL SUSTAINABILITY OF PRAIRIE LAKES AND RESERVOIRS

The dynamics of algal growth and algal bloom development in eutrophic prairie lakes and reservoirs offers an opportunity to assess the negative consequences of exponential growth and its sustainable and unsustainable phase. Extreme situations of ecological perturbation and instability, where the structure and function of an aquatic ecosystem breaks down, are demonstrated on summary results from lakes undergoing collapse (crashes) of algal blooms or winter anoxia as a result of unsustainable productivity. Algal blooms provide warning signals during their development to indicate various levels of ecological sustainability. Phytoplankton biomass was found to be a measure of ecological sustainability with chlorophyll a levels less than 50 μg/L being sustainable and over 100 μg/L unsustainable.Due to high natural input of nutrients from prairie soils and advanced eutrophication, the carrying capacity of many prairie lakes and reservoirs is often fully utilized and leaves little room for further loads from popu...

Time-lag algal growth dynamics: biological constraints on primary production in aquatic environments

Changes in the nutrient regime of phytoplankton cells induce variable time lags before the onset of cell division (quasi-instantaneous response to more than 24 h lags), dependent mainly on the algal species and the magnitude of the nutrient pulse. The latter parameter appears to be a main controlling factor in algal growth dynamics under transient conditions, overriding other variables such as temperature, irradiance and nutritional state. The presence of such phenomena puts intrinsic limits on primary production in a variable nutrient environment because algal cells are not made up of synthetic components only (sensu Williams 1971), but also of structural and genetic material. Under these conditions, high nutrient uptake rates over short time periods do not necessarily lead to high growth rates (defined as increase in cell numbers) over comparable time scales, even ~f cell quota increase very rapidly follow~ng nutrient resupply. Data from different groups of investigators on uptake-growth coupling, internal nutrient pools, growth lag, and carbon-nitrogen uptake interactions show consistent patterns as follows. for phytoplankton in a vanable nutrient environment, 2 essential strategies emerge at the genus level. One is the 'growth' response, exhibited by the genera Durialiella and Chaetoceros, which do not accumulate internal pools of inorganic nutrients, whose uptake and growth are closely coupled, and which therefore process nutrient pulses very rapidly into new cells. The other is the 'storage' response, found in genera such as Thalassiosira or Amphidinium, which have the capability of accumulating large internal nutrient pools, present extensive uncoupling between uptake and growth, and exhibit lags in cell v the first response type would provide a competitive advantage at high frequency pulses.

Algal growth dynamics under light interaction: A nonlinear evolution problem

A mathematical model for interaction of algae with light is presented. This model consists of a couple of nonlinear integro-differential equations dealing with the evolution of algae concentration due to absorption of light and the evolution of light intensity due to absorption and scattering by algae and water. The model is formulated as a nonlinear abstract Cauchy problem in a Banach space suited to describe the physical features of the problem. By using techniques and results of semigroups theory, it is proved that the system has a unique global strict solution.