Algal Particles Research Articles

Optimizing Algal Oil Extraction and Transesterification Parameters through RSM, PCA, and MRA for Sustainable Biodiesel Production

This study presents a comprehensive optimization of algal oil extraction and transesterification for sustainable biodiesel production. Freshwater Spirogyra algae underwent Soxhlet extraction using n-hexane. response surface methodology (RSM), principal component analysis (PCA), and multivariate regression analysis (MRA) were employed to investigate the effects of biomass–solvent ratio (BSR), algae particle size (APS), and extraction-contact time (E-CT) on algal oil yield (AOY). The extracted oil was then converted to biodiesel via transesterification, and the impacts of the methanol–oil ratio (MOR) and transesterification-contact time (T-CT) on biodiesel conversion efficiency (BCE) were analyzed. Results demonstrate that optimal BSR, APS, and E-CT for maximal AOY are 1:7, 400 µm, and 3–4 h, respectively. For transesterification, a MOR of 12:1 and a T-CT of 4 h yielded the highest BCE. Predictive models exhibited exceptional accuracy, with R2 values of 0.916 and 0.950 for AOY and BCE, respectively. The produced biodiesel complied with ASTM D6751 and EN 14214, showcasing its potential for renewable energy applications.

Multiscale effects of radial mixing on mixotrophic microalgal growth and macromolecular synthesis in tubular bubble-column photobioreactors

Extremophillic microalga Chlorella sorokiniana is grown mixotrophically in a 5 L externally-illuminated tubular bubble-column photobioreactor with an external light intensity of 10,500 lx (≈195 μmol-photons.m−2.s−1) at atmospheric (0.04 %), 1 %, 2 %, 3 %, 4 %, and 5 % CO2 concentrations, with acetic acid and urea as the organic carbon and nitrogen sources, respectively, for 6–8 days. Two different setups are employed: one permits axial air flow, and another promotes radial mixing of algal particles, dissolved CO2 and nutrients along with axial sparging. We show that radial mixing increases biomass yields by reducing both photo-limitation and photo-inhibition up to CO2 concentrations <3 %, above which substrate (CO2) inhibition necessitates lower reactor mixing. Radial mixing increases the lipid yield from 1.06 and 1.61 g/L to 1.27 and 1.78 g/L at 2 % and 3 % CO2, respectively, in nitrogen-limited cases, resulting in a 10–20 % increase. We show that complete reactor mixing, facilitated by the dual effects of branched (radial) and axial sparger, is preferred only in the absence of substrate (CO2) inhibition. Subsequently, we stratify the tubular photobioreactor design strategy into two regimes based on CO2 inlet concentrations. In one regime (for inlet CO2 < 3 %), we recommend the deployment of branched sparger to facilitate both radial and axial mixing simultaneously, thereby creating a well-mixed reactor at lower CO2 concentrations. In the other regime (for inlet CO2 > 3 %), axial sparging alone is recommended since complete mixing of CO2 increases substrate inhibition by reducing the reactor pH below 7.5.

Effects of light intensity and salinity on formation and performance of microalgal-bacterial granular sludge

Photosynthetic microorganisms in microalgal-bacterial granular sludge offer advantages in wastewater treatment processes. This study examined the effects of light intensity and salinity on microalgal-bacterial granular sludge formation and microbial changes. Activated sludge was inoculated into three bioreactors and operated in batch treatment mode for 100 days under different light intensities (0, 60, and 120 μmol m−2 s−1) and staged increases in salinity concentration (0, 1, 2, and 3%). Results showed that microalgal-bacterial granular sludge was successfully formed within 30 days, and high light exposure increased algal particle stability and inorganic nitrogen removal (63, 66, 71%), while chemical oxygen demand removal (>95%) was similar across groups. High-throughput sequencing results showed that the critical algae were Chlorella and diatoms, while the main bacteria included Paracoccus and Xanthomarina with high extracellular polymeric substance production. This study aims to enhance the comprehension of MBGS processes in saline wastewater treatment under varying light intensities.

An integrated approach for the extraction of lipids from marine macroalgae consortium using RSM optimization and thermo-kinetic analysis

This work presents an integrated approach for the extraction of lipids from marine macroalgae using RSM optimization and thermo-kinetic analysis. The lipids were extracted from marine macroalgal biomass using a Soxhlet extractor. The Soxhlet extraction parameters, including temperature (60–80 °C), solvent-to-algae ratio (3:1–7:1), algal particle size (0.05–0.25 mm), and extraction time (60–180 min), were optimized using RSM to achieve the maximum possible lipid extraction yield from marine macroalgae. The highest lipid extraction yield of 12.76% was obtained using the optimized conditions, which included an extraction temperature of 72 °C, a solvent-to-algae ratio of 5:1, an algal particle size of 0.16 mm, and an extraction time of 134 min. The kinetic analysis revealed an activation energy of 52.79 kJ mol−1 for the Soxhlet extraction process. The thermodynamic analysis of the Soxhlet extraction process demonstrated the following results: ΔH = 49.98 kJ mol−1, ΔS = −128.24 J K−1 mol−1, and ΔG = 93.98 kJ mol−1. The GC-MS analysis confirmed that the extracted algal lipids exhibited a composition of 14.20% palmitic acid, 4.89% stearic acid, and 76.97% oleic acid. The physiochemical analysis ensured that the extracted algal lipids possess excellent qualities, making them desirable for sustainable biofuel production.

Modification of PVDF membrane for harvesting of Nannochloropsis sp. and its cleaning results

One of the biggest challenges in implementing microalgae-based biofuels is the effective harvesting process. Filtration membrane has become one of the flexible methods in microalgae harvesting. This study investigated the harvesting of Nannochloropsis sp. using a modified PVDF membrane at various LiCl as an additive with N-methyl-2-pyrrolidone (NMP) solvent. Harvesting of Nannochloropsis sp. with PVDF membrane has never been reported before. The addition of LiCl can improve the performance of PVDF membrane due to LiCl has a great affinity for water, resulted in inducing the formation of the pore structure of membrane. The optimum membrane composition was determined at various LiCl additive from 1% to 3% (w/w). The hydrophilicity of the membrane increased as indicated by the increasing of water permeance, which were 516, 546, 660, and 614 l m−2h−1 bar−1 for neat PVDF, PVDF/LiCl-1, PVDF/LiCl-2, and PVDF/LiCl-3 membrane, respectively. PVDF/LiCl-2 membrane showed the highest water permeance and the highest total average permeance (150 l m−2h−1 bar−1) with 100% rejection of Nannochloropsis sp. harvesting. The membranes was cleaned using sodium hypochlorite, citric acid, and nitric acid. The SEM results showed that the membrane after cleaning appears the algae particles in the membrane pore. Furthermore, algae particles were almost not visible on cleaned membrane. The FTIR results showed an absorption at 3401 cm−1, which was a characteristic of the hydrogen N–H bond, also including a typical amide uptake (C=O) at 1648 cm−1 indicating protein appearance. Moreover, the cleaned membrane did not appear any absorption that indicates the foulant.

Reflection Spectra Coupling Analysis and Polarized Modeling of Optically Active Particles in Lakes

The coupling between optically active substances of algae particles and inorganic suspended solids of water makes the characteristics of reflection spectra of water complex and changeable. This makes modeling and inversion of polarization remote sensing in class II water difficult. In our study, considering the influence of the mixing ratio of algae particles and inorganic suspended solids, the sensor incidence angle, and the solar zenith angle on the polarization reflection spectrum, we analyzed the coupling characteristics of the polarized bidirectional reflectance of particulate matter through control experiments of mixed components of water particles in the laboratory. With Chaohu Lake in China as an example, the polarized reflectance coupling characteristics of water particles was investigated by the water-leaving radiation. The results showed that in the characteristic bands of 570, 675, and 705 nm, the degree of linear polarization (DOLP) was sensitive to the water-leaving radiation of the particles rather than to the reflectance. With the variation of observation angle, the reflection spectra were strongly interfered with by solar flare when the sensor zenith angle was close to 50° on the meridian plane with an azimuth angle of 180°, but DOLP was less affected, while also having a low correlation in the high concentration region. Combined with the coupling characteristics of particles at 675 and 705 nm, the model of DOLP ratio was established by partial least squares regression (PLSR) with a determination coefficient (R2) of 0.91, root mean square error (RMSE) 0.035, and a verification accuracy of 0.959. This shows that the model has better prediction ability for the coupling characteristics of water particles by the polarization reflection spectra and provides good support for mixed spectral unmixing of class II water.

A classification-based approach to mapping particulate organic matter (POM) in inland water using OLCI images.

Particulate organic matter (POM) plays a major role in freshwater ecosystems by serving as a bridge for the conversion of various nutrients. The composition and sources of POM in inland lakes are complex, making it difficult to estimate its concentration accurately via remote sensing. Therefore, a classification-based method based on the sources and composition of POM is proposed for estimating POM concentrations in inland lakes. In this study, 379 samples were collected from ten lakes in the Yangtze River Delta (YRD) at different times. A water-type classification method based on OLCI [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] was developed for POM estimation based on biological and optical characteristics. Water type 1 is relatively clear, and POM may originate from aquatic vegetation or sediment. Water type 2 was dominated by inorganic suspended matter, and POM mainly originated from the attachment and entrainment of inorganic minerals. Water type 3 is an algae-dominated water body, and POM is mainly derived from fresh algal particles and the microbial degradation of phytoplankton. Therefore, specific POM estimation algorithms were developed for each water type. OLCI [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] were used for water type 1; [Formula: see text], [Formula: see text], and [Formula: see text] were adopted for water type 2; and [Formula: see text], [Formula: see text], and [Formula: see text] were selected for water type 3. Using an independent dataset to evaluate the estimation accuracy of the developed algorithm, the results show that the estimation performance of this algorithm is significantly improved compared to the two other algorithms used; the mean absolute percentage errors (MAPE) decreased from 72.56% and 52.21% to 32.61%, and the root mean square errors (RMSE) decreased from 3.05mg/L and 2.24mg/L to 1.75mg/L. A random error analysis of the atmospheric correction demonstrated that this algorithm is robust and can still perform well within a random error of 30%. Finally, this method was successfully applied to map the POM concentrations in the YRD using OLCI images acquired on November 12, 2020.

Technological Evaluation of Algae-Based Fillers for Polymer 3D Printing

One approach to reducing the environmental footprint of conventional polymers is to compound them with bio-based fillers. Plant-based materials have already been successfully used as polymer fillers. In this context, algae-based fillers received minor attention. Due to their unique growth efficiency and ability to capture large amounts of CO2, the use of algae-based fillers could have economic and ecologic advantages. In this work, a possible use of algae as a sustainable filler for filament materials was technologically evaluated. In practical investigations, conventional polyethylene-terephthalate-glycol (PETG) was mixed with the microalgae spirulina platensis and chlorella vulgaris and extruded to 3D printing filaments. Based on printed test specimens and material samples, the printability, mechanical, and thermal properties of the composite were determined. Filaments with a homogeneous distribution of algae particles and stable diameters up to a filler content of 30 wt.% could be produced. All filaments had good printability and adequate moisture sensitivity for higher algae contents. For 30 wt.% the tensile strength of the produced filaments decreases from 54 MPa to 24 MPa, the flexural strength decreases from 87 MPa to 69 MPa, and the material operating temperature decreases slightly from 70 °C to 66 °C. The addition of smaller amounts of algae results in minor changes regarding the overall performance. The properties of the material were comparable to those of other natural fillers such as wood, bamboo or cork. The main objective of adding bio-based materials to polymeric matrices can be achieved. Our results suggest that algae-based filaments can be produced as a more sustainable and low-cost material.

Trojan horse effects of microplastics: A mini-review about their role as a vector of organic and inorganic compounds in several matrices

&lt;abstract&gt; &lt;p&gt;The "Trojan horse effect" of microplastics for organic and inorganic contaminants is an interesting topic. So far, the scientific community has focused on microplastics strictly as contaminants, but their role as vectors is still undefined. Adsorption of pollutants follows the Freundlich model by physisorption mechanism. Furthermore, ages and types of microplastics influence the adsorption of pollutants onto microplastics. Moreover, natural particles, like algae particles, present in the environment can interfere in the adsorption mechanisms. Due to their chemical composition of mainly O and N, it has been suggested that natural particles have a stronger adsorption affinity for some pollutants. Furthermore, microplastic's role as vector of pollutants into organisms is controversial. In fact, it has been suggested that the release is species-specific. In &lt;italic&gt;T. japonicus&lt;/italic&gt;, accumulation of Hg loaded onto microplastics increased by 2.5 times, whereas a reduction of bioavailability of Hg was observed in &lt;italic&gt;R. lens&lt;/italic&gt;.&lt;/p&gt; &lt;/abstract&gt;

Nitrogen loading increases both algal and non-algal turbidity in subtropical shallow mesocosms: Implication for nutrient management

Excess nitrogen (N) loading in summer often boosts phytoplankton growth and increase algal turbidity. In eutrophic shallow lakes, the increased algal production may also augment the abundance of deposit-feeding tubificid worms and thereby sediment resuspension and non-algal turbidity. However, few studies have explored the effects of high N loading on this benthic process in eutrophic shallow lakes. Here, we conducted an outdoor mesocosm experiment in a summer-winter season (177 days) on the shore of subtropical Lake Taihu, China. Each mesocosm contained a 10 cm layer of lake sediment and 450 L of lake water. Nitrate was added weekly to three of the mesocosms, while another three functioned as controls. Our results showed that N addition significantly increased algal particles as water chlorophyll a (Chl-a) increased significantly following N addition. Moreover, significantly higher levels of inorganic suspended solids (ISS) were observed in the mesocosms with added N, indicating elevation of non-algal turbidity as well by the N addition. We attribute the latter to increased sediment resuspension as the abundance of tubificid worms was significantly higher in the N addition mesocosms. Accordingly, our study indicates that high N loading in subtropical shallow lakes may boost both algal and non-algal turbidity in part via benthic-pelagic coupling processes. Our results suggest that alleviation of eutrophication in shallow eutrophic lakes may require a strategic approach to adequately control both N and phosphorus.

Pengaruh Variasi Komposisi Dekomposer EM4 Dan Molase pada Pembuatan Pupuk Organik Cair Dari Limbah Budidaya Lele

Catfish cultivation is widely cultivated by the Indonesian people and generally uses intensive methods so as to produce high stocking densities. Fish farming activities will produce wastewater in which organic residues can accumulate from feeding fish, manure, particles of fish feed residue, bacteria, and algae. In addition, catfish cultivators utilize the remaining water from catfish cultivation as plant fertilizer without further processing. This will affect other organisms in the soil, so it is necessary to research and manufacture liquid fertilizer from water left over from catfish farming. Liquid organic fertilizer is a fertilizer derived from organic materials from plants and animals that have undergone decomposition and have a liquid form of product. Liquid organic fertilizer is made by comparing the composition of the remaining water from catfish farming, EM4, and molasses. This aims to determine the effect of bioactivators for liquid organic fertilizer with water as a base material from catfish cultivation. The composition made is 1 liter of pure wastewater (sample A); 1 liter of pure waste, 20 ml of EM4, and 20 ml of molasses (sample B); 1 liter of pure waste, 10 ml of EM4, and 30 ml of molasses (sample C); and 1 liter of pure waste, 30 ml of EM4, and 10 ml of molasses (sample D) which were then kept in the mixture for 15 days in a closed manner. From these 4 variations, the results of testing pH, temperature and also organic C content were obtained where the temperature and pH tests met the quality standards for liquid organic fertilizers, while the organic C values did not meet the quality standards for liquid organic fertilizers.

Scattering of Laguerre-Gaussian Vortex Beams by Underwater Suspended Spherical Algal Particle Swarms

Scattering of Laguerre-Gaussian Vortex Beams by Underwater Suspended Spherical Algal Particle Swarms

Copper Adsorption to Microplastics and Natural Particles in Seawater: A Comparison of Kinetics, Isotherms, and Bioavailability.

The growing use of plastics has led to microplastics (MPs) being ubiquitously distributed in marine environments. Although previous studies have emphasized MPs as important metal-transport vectors, few have considered the differences between these anthropogenic particles and their coexisting natural counterparts in sequestering metals in seawater. Here, we compared Cu adsorption to pristine and naturally aged MPs (polystyrene and polyethylene) with that to algae particles and sediments and assessed the bioavailability of the adsorbed Cu by a gut juice extraction assay. Adsorption kinetics and isotherms consistently showed that natural particles bound far more Cu to their surfaces than MPs. The rougher surfaces, greater specific surface areas, and lower ζ-potentials of natural particles contributed to their stronger Cu adsorption capacity than pristine or aged MPs. Natural particles also contained more diverse functional groups for binding Cu, with oxygen-containing groups playing a dominant role. Adsorbed Cu on natural particles was less extractable by sipunculan gut juice than that on MPs, indicating their higher Cu affinity. Overall, our study suggests that natural particles outcompete MPs in carrying metals in the water column and transferring them to marine organisms in today's environmental context. This work provides new insights for assessing the risks of MPs in marine environments.

Digestion and nutrition in freshwater bryozoans (Phylactolaemata)

AbstractAs suspension feeders, freshwater bryozoans (Phylactolaemata) ingest a wide variety of particles. After this material is processed in the gut, the remaining wastes are ejected in a pellet. Curiously, fecal pellet contents appear perfectly intact, often still alive, and apparently unharmed. This raises questions about the true sources of bryozoan nutrition and the entire digestive process itself. This article summarizes the results of controlled feeding experiments as well as findings from gut examination by scanning electron microscopy. Extensive feeding tests with bryozoan species in three families show that colonies ingesting protozoans and small rotifers grow much faster than those on any other diet. There is no evidence for digestion of green algae or bacteria, including cyanobacteria. Close observations reveal muscular contractions of the stomach crushing and abrading fragile prey organisms, with possible assistance from indigestible algal particles. A dense carpet of microvilli lines the walls of the stomach and intestine. In most instances, these are organized in a three‐dimensional matrix that offers an extensive surface area. Because all food is handled in sequential batches, there is limited time for many particles to be digested.

Changes in Algal Particles and Their Water Quality Effects in the Outflow River of Taihu Lake

Connected rivers are a common engineering method to ensure the ecological health of urban water. However, for the lakes with serious cyanobacteria blooms, the algal particles are carried by the outflow of the lake and will have a significant impact on water quality. The location at which the Liangxi river meets Meiliang Bay of Lake Taihu was selected to explore the influence of the eutrophic lake on the connected rivers, and high-frequency monitoring was conducted in summer for three consecutive years to analyze the changes in the flux of cyanobacterial bloom particles in rivers and their impact on river water quality. The results show that:① The improvement of the algal cyanobacteria bloom in Meiliang Bay and the operation of the pressure-controlled algae well at the entrance of the river significantly reduced the concentration of chlorophyll a and the flux of algae particles in the Liangxi River. The average value of the concentration of chlorophyll a and the flux of algae particles in the river in summer 2019 were 54.34 μg·L-1 and 84.7 t·d-1, respectively, and significantly lower than those of 2017; ② Water diversion had a significant effect on improving the water quality of the receiving water. Except for DTP, the nitrogen and phosphorus concentrations of the remaining forms of the Liangxi River showed a downward trend from 2017 to 2019, indicating that the water quality of the Liangxi river improved after water transfer; ③ A large amount of cyanobacterial blooms entering the channel significantly increased the particulate nitrogen and phosphorus content of the water. From 2017 to 2019, the nitrogen and phosphorus in the Liangxi River were mainly PN and PP, accounting for 62.5% and 70.8% of TN and TP, respectively; ④ The water quality of the Beijing-Hangzhou Grand Canal and other connected rivers has not been affected by the algal particles in Meiliang Bay. In August 2019, the chlorophyll a content in the canal water decreased by 65% compared with that of June, indicating that cyanobacterial bloom particles have not accumulated in the Grand Canal; ⑤ On the premise that the cyanobacteria bloom in the lake has not been effectively improved, the algae particles carried by the water diversion will have an impact on the water quality and landscape of the local reach connecting the river.

Spatial Temporal Anisotropic Transport of the Microalgae Chlorella Vulgaris in the Microfluidic Channel

Transport of biomaterials in confined geometry exhibit complex dynamics, both in spatial and temporal scales. In this work, we examined the transport behavior of microalgae Chlorella Vulgaris inside the microfluidic channel under pressure-driven Poiseuille flow environment. The microalgae system is treated as the spherical naturally buoyant particles. The algae particles trajectories are visually traced using particle imaging techniques and the sample paths are resolved in stream wise (flow) and perpendicular directions. In order to understand boundary wall effects on the flow, we partitioned the microfluidic channel into three different regions, namely the center region and two near-wall boundary regions based on the velocity flow profile. Time-averaged mean square displacement (MSD), probability density function (PDF), skewness, and kurtosis of finite ensembles of particle trajectories are determined for these regions. In addition to the spatial dependencies, we also examined the transient characteristics of the algae transport at early-time and long-time. We found the existence of the mixed types for transport dynamics irrespective of flow region separation often assumed in many laminar flow simulations. This finding will be useful for optimization of mixing of algae culture in micro-scale photobiore actor as the productivity of cell growth depends critically on the cell dispersion or transport

Multiscale integration of mixotrophic microalgal cultivation, lipid synthesis, rapid biomass harvesting, and nutrient recycling in pilot-scale photobioreactors

This work presents an acetic acid mediated energy-efficient process that integrates mixotrophic cultivation of extremophilic microalga Chlorella sorokiniana at the photobioreactor (macro) scale, with algal lipid accumulation at the molecular (micro) scale, and rapid biomass harvesting at the algal particle (meso) scale, followed by multiple recycling of nutrient-rich harvested broth. Chlorella sorokiniana is grown mixotrophically in Tris-Acetate-Phosphate medium using Tris buffer as nitrogen source, CO2 and acetic acid as inorganic and organic carbon sources, respectively, at light intensities of 5600–11,000 lx and an optimized photoperiod of 18:6 (Light: Dark) in 25-l bubble-column photobioreactors for 138 h. Acetic acid is used as an organic carbon source to integrate the processes occurring at the three scales; acetic acid ionizes to acetate ions in the culture media, which are enzymatically assimilated inside the alga's cytosol to acetyl-CoA that enhance fatty acid synthesis at the molecular scale and biomass yield at the reactor scale. The excess acetate ions in the culture medium react with the ions formed by the hydrolysis of potash alum to form complexes that react with the ions on algal cell surfaces to facilitate rapid flocculation at the meso (particle) scale. This multiscale integration results in maximum biomass and overall productivity 4.16 g/L and 0.70 g/L/day, respectively, with 25.8% lipid content, obtained at 2% CO2 and 11,000 lx, while reducing the harvesting time to 18–28 min, at a harvesting efficiency and cost of 98%, and 0.064$ per kg of dry biomass, respectively. The first and the second recycles of nutrient-rich broth lower the biomass yield by 9.8% and 14.2%, respectively, while increasing the harvesting time by 8.2% and 15.3%, respectively, as compared to fresh broth. Such multiscale integration of algal growth, macromolecular synthesis and biomass harvesting, followed by broth recycling, offers a novel, cost-effective technology for mixotrophic mass cultivation of extremophilic microalgae.

Large batch bench-scale dissolved air flotation system for simulating full-scale turbidity removal

ABSTRACT One of the expected outcomes of global warming is increased algal and cyanobacterial blooms. Based on its ability to separate algal particles, dissolved air flotation (DAF) is considered as a climate change adaptation technology for water treatment. The feasibility of DAF treatment is often assessed using DAF jar tests; however, they are not particularly good at predicting a full-scale DAF system’s turbidity removals. Therefore, our group has developed a more reliable larger-diameter/larger-volume batch apparatus (LB-DAF), which was optimized by comparison with a full-scale DAF plant treating a low turbidity, highly coloured river water (SUVA ∼ 4.3). The objective of this study was to verify that the LB-DAF was capable of simulating full-scale DAF systems treating two significantly different waters. One was water from a large eutrophic bay in Lake Ontario (SUVA ∼2.6) and the second was a river water (SUVA ∼3.5). The turbidity removals achieved by the full-scale DAF systems treating these waters were compared with those for the LB-DAF tests conducted using different flocculation velocity gradients, saturated water pressures, recycle ratios and water depth to diameter ratios. The LB-DAF tests are good predictors of the full-scale DAF turbidity removals, the average difference for the two waters tested were 2% and 6%. The LB-DAF natural organic matter (NOM) removals for both waters differed by less than 1% from that measured at the corresponding treatment plants. In addition, as in our previous LB-DAF study, varying the different LB-DAF operational variables did not have a significant impact on turbidity and NOM removals.

Influence of Wind Currents on Spectral Light Attenuation in Water

The paper deals with wind current dependences of spectral light attenuation measured in natural waters of lakes in the south of West Siberia. To reveal the significance of abiotic, i.e., physical factors affecting water transparency, we calculate relative spectral contributions of individual optically active water components in freshwater lakes established during hydrophysical research of 2019. In addition, the published data on the daily dynamics of spectral water transparency obtained by researchers of IWEP SB RAS for Lake Krasilovskoye in 2016 are partially analyzed. The greatest spectral contribution to the total light attenuation falls on suspension consisting mainly of phytoplankton algae particles and yellow matter. Wind current velocity is a determining factor affecting light attenuation dynamics because the upward redistribution of particle concentration in upper layers of the lake caused by wind-induced turbulent mixing occurs faster than the change in the yellow matter content as a result of physical-chemical processes responsible for its formation. In such cases, the intensity of turbulence (turbulent mass exchange) is usually characterized by flow (integral) Richardson number Ri, which is directly dependent on wind current velocity. In our experiment, Ri equals to 1.5.

Elevated algal and sedimentary turbidity alter prey consumption by emerald shiner (Notropis atherinoides)

AbstractAnthropogenic increases to turbidity (suspended particulates) in the water column can alter the underwater visual environment, resulting in disruptions to visual signals in fishes exposed to these conditions. However, dissimilar turbidity types (e.g. sedimentary or algal particles) are expected to influence the visual environment in different ways as they exhibit differing physical characteristics. The main objective of this study was to determine the influence of elevated turbidity on prey consumption in emerald shiner (Notropis atherinoides). A secondary goal was to determine the relationship between visual morphological structures (i.e. eyes and optic lobe of brain) and prey consumption in different visual environments. We tested emerald shiner consumption of Daphnia magna in three turbidity types (sedimentary, algal and sedimentary + algal) at two different levels (20 NTU and 40 NTU) as well as in a clear (&lt;5 NTU) control. We found that prey consumption decreased in high turbidity (40 NTU) across turbidity types relative to the control treatment. Further, consumption was lower in each treatment relative to the control with the exception of the moderate (20 NTU) sedimentary turbidity treatment. This study indicates that for emerald shiner, while high levels of turbidity are likely to suppress foraging, moderate levels of sedimentary turbidity may be slightly beneficial for foraging success. Further, it is likely that increases in algal turbidity via cultural eutrophication are likely to result in reductions in prey consumption.