Browsing by Author "Fujino, Takeshi"

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Cyanotoxins availability and detection methods in wastewater treatment plants: A review
(Elsevier Ltd., 2024) Manjitha, K.G.L.; Sewwandi, B.G.N.; Takahashi, Toshinori; Fujino, Takeshi
Research interest in ecological significance, toxicity, and potential applications of cyanobacterial metabolites has grown as a result of the current extensive cyanobacterial blooms in water bodies. Under favourable conditions, specific cyanobacterial species release cyanotoxins, hepatotoxins, dermatoxins, neurotoxins, and cytotoxins, creating a heightened threat to aquatic ecosystems and human health. Wastewater treatment plants (WWTPs) offer one of the best culture media for cyanobacterial development and synthesis of cyanotoxins by providing optimum environmental conditions, including temperature, light intensity, lengthy water residence time, and nutrient-rich habitat. To discover the intricate relationships between cyanobacterial populations and other living organisms, it is important to comprehend the cyanobacterial communities in the ecology of WWTPs. Monitoring strategies of these cyanotoxins typically involved combined assessments of biological, biochemical, and physicochemical methodologies. Microscopic observations and physicochemical factors analysis cannot be carried out for toxicity potential analysis of blooms. Due to their high sensitivity, molecular-based approaches allow for the early detection of toxic cyanobacteria, while biological analysis is carried out by using water bloom material and cell extracts to screen cyanotoxins build up in organisms. As each approach has benefits and drawbacks, the development of an integrated multi-method laboratory system is essential to obtain trustworthy results and accurate detection of cyanotoxin levels in WWTPs allowing us to take necessary proactive and preventative approaches for effective wastewater treatment.
Cytogenotoxicity of raw and treated dairy manure slurry by two-stage chemical and electrocoagulation: An application of the Allium cepa bioassay
(Elsevier Ltd., 2024) Meetiyagoda, Thenuwara Arachchige Omila Kasun; Samarakoon, Thilomi; Takahashi, Toshinori; Fujino, Takeshi
Livestock farming is an essential agricultural practice. However, the improper management of livestock wastes and discharge of untreated or partially treated livestock manure slurry poses significant environmental problems. In this study, we aimed to compare the cytogenotoxic potential of untreated and treated dairy manure slurry treated with a two-stage chemical and electrocoagulation (EC) using the Allium cepa bioassay. The A. cepa bioassay is a well-established standard tool for assessing the cytogenotoxic effects of environmental contaminants, especially those that are occurred as complex contaminant mixtures. The dairy manure slurry was subjected to chemical treatment utilizing polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) at optimized conditions, followed by EC utilizing either aluminum (Al) or steel anodes. The treated and untreated samples were then evaluated for their potential cytogenotoxicty using the A. cepa bioassay, by measuring the nuclear abnormalities (NAs) and chromosomal aberrations (CAs), along with the mitotic indices (MIs). Our findings revealed a significant reduction in cytogenotoxic indicators in the treated liquid fraction compared to the untreated dairy manure slurry. Specifically, the frequency of total NAs showed a significant reduction from 154 ‰ to 37 ‰ when the dairy manure slurry was treated with chemical coagulation followed by EC utilizing an Al anode. Moreover, the MI exhibited a significant improvement from 7 ‰ to 123 ‰, suggesting the mitigation of toxic effects. These results collectively demonstrate the effectiveness of the two-stage chemical and EC treatment under optimal conditions in treating diary manure slurry while reducing its cytogenotoxicity for living systems. The A. cepa bioassay proved to be a sensitive and reliable method for assessing the toxicity of the treated samples. The efficient solid–liquid separation and the reduction of toxicity in the liquid fraction for biological systems achieved through this treatment process highlight its potential for sustainable management of livestock waste and the preservation of water quality. Nevertheless, further studies are required to assess the toxicity of solid fraction.
Detection of Zn2+ ions using a high-affinity low-molecular-weight fluorescence probe in two freshwater organisms
(Korean Society of Environmental Risk Assessment and Health Science, 2023) Shrestha, Ashok K.; Samarakoon, Thilomi; Fujino, Takeshi; Hagimori, Masayori
Objective The objective of this study was to determine the uptake and distribution of zinc ions (Zn2+) in two freshwater organisms, Moina macrocopa and Rheocricotopus larvae using a high-affinity low-molecular-weight Zn2+-ion-selective fluorescence probe. Methods M. macrocopa and Rheocricotopus larvae were exposed separately to dissolved Zn2+ (0.1 and 1 mg/L) for 12, 24, and 48 h in three replicates along with a control. Later, the organisms were incubated with the fluorescence probe in six-well plates in the dark at room temperature. At the end of the incubation period, the organisms were washed with a phosphate buffer solution (0.01 M). The live organisms were then imaged using a fluorescence microscope and the fluorescence inten- sities of the images were determined. Results The results revealed that the Zn2+ ions are uptaken and internalized into the bodies of the organisms exposed to Zn2+ ion concentrations, as indicated by a significant increase in the fluorescence intensities of the fluorescence images of the organisms. According to the fluorescence images, the Zn2+ ions were mainly localized in the lower gut region of M. macrocopa at the end of 48 h. However, in Rheocricotopus larvae, the Zn2+ ions were detected in the midgut region of the digestory tube after 48 h of exposure. Therefore, this was dependent upon both the Zn2+ concentration in the exposure media and the exposure duration. Conclusion Taken together, the distribution of Zn2+ ions in different aquatic species is species-specific. Furthermore, the present study provides insight into the potential use of high-affinity low-molecular-weight Zn2+-ion-selective fluorescence probes to detect labile Zn2+ in aquatic organisms and the toxicological implications of zinc pollution in aquatic environments.
Individual and combined effects of humic acid on life-history characteristics of the water flea Moina macrocopa upon whole-lifespan cadmium exposure
(Springer Nature Switzerland AG, 2023) Samarakoon, Thilomi; Fujino, Takeshi
Investigation of the effects of natural compounds in aquatic ecosystems on the modula- tion of toxicity of coexisting xenobiotics is impor- tant for realistic ecological risk assessments. We investigated the individual and interactive effects of sublethal cadmium (Cd) concentrations and environ- mentally realistic humic acid (HA) concentrations on several life-history characteristics of Moina mac- rocopa. Female individuals were exposed to Cd and HA for their entire lifespan from the neonatal stage. The survival and reproductive output were recorded daily, and the growth and swimming velocity were determined upon maturity. Cd at the tested concentra- tions in single treatments did not significantly affect the growth and lifespan. But 5 μg/l Cd significantly decreased the swimming velocities and reproduction. Greater than 20 mg/l HA in single treatments signifi- cantly increased the individuals’ growth, reproduc- tion, and lifespan. Swimming velocities were signifi- cantly increased at 10 mg/l HA in single treatments. In combined treatments, such beneficial effects on all life-history characteristics were still seen under the co-occurrence of 1 μg/l Cd, but with 5 μg/l Cd, those beneficial effects on life-history characteristics except for swimming velocities were not observed. These dissimilar responses of different life-history charac- teristics indicate energy tradeoffs for maintenance, reproduction, and longevity, upon exposure to stress- ors in M. macrocopa.
Toxicity of triclosan, an antimicrobial agent, to a nontarget freshwater zooplankton species, Moina macrocopa
(Institute of Electrical and Electronics Engineers (IEEE), 2024) Samarakoon, Thilomi; Fujino, Takeshi
The toxicity of triclosan (TCS) on the freshwater cladoceran Moina macrocopa was investigated by acute and chronic toxicity assessments followed by genotoxicity and oxidative stress response analyses. The 48-h LC50 of TCS for ≤24-h-old M. macrocopa was determined as 539 μg L−1. Chronic exposure to TCS at concentrations ranging from 5 to 100 μg L−1 showed a stimulatory effect at low concentrations (≤10 μg L−1) and an inhibitory effect at high concentrations (≥50 μg L−1) on growth, reproduction, and population-growth-related parameters of M. macrocopa. The genotoxicity test results indicated that TCS concentrations ranging from 50 to 100 μg L−1 can alter individuals' DNA. Analysis of the antioxidant enzymes catalase (CAT) and glutathione s-transferase (GST) demonstrated increased levels of these enzymes at high TCS concentrations. Our results indicated that TCS concentrations found in the natural environment have minimal acute toxicity to M. macrocopa. However, TCS at even low concentrations can significantly affect its growth, reproduction, and population-growth-related characteristics. The observed responses suggest a hormetic dose–response pattern and imply a potential endocrine-disrupting effect of TCS. Our molecular and biochemical findings indicated that high concentrations of TCS have the potential to induce oxidative stress that may lead to DNA alterations in M. macrocopa.