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Xu S, Zhu P, Wang C, Zhang D, Zhang M, Pan X. Nanoscale exopolymer reassembly-trap mechanism determines contrasting PFOS exposure patterns in aquatic animals with different feeding habitats: A nano-visualization study. JOURNAL OF HAZARDOUS MATERIALS 2024; 478:135515. [PMID: 39178777 DOI: 10.1016/j.jhazmat.2024.135515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Revised: 08/12/2024] [Accepted: 08/12/2024] [Indexed: 08/26/2024]
Abstract
The behavior and fate of PFOS (perfluorooctanesulfonate) in the aquatic environment have received great attention due to its high toxicity and persistence. The nanoscale supramolecular mechanisms of interaction between PFOS and ubiquitous EPS (exopolymers) remain unclear though EPS have been widely-known to influence the bioavailability of PFOS. Typically, the exposure patterns of PFOS in aquatic animals changed with the EPS-PFOS interaction are not fully understood. This study hypothesized that PFOS exposure and accumulation pathways depended on the PFOS-EPS interactive assembly behavior and animal species. Two model animals, zebrafish and chironomid larvae, with different feeding habitats were chosen for the exposure and accumulation tests at the environmental concentrations of PFOS in the absence and presence of EPS. It was found that PFOS triggered the self-assembly of EPS to form large aggregates which significantly trapped PFOS. PFOS accumulation was significantly promoted in zebrafish but drastically reduced in chironomid larvae because of the nanoscale interactive assembly between EPS and PFOS. The decreased dermal uptake but increased oral uptake of PFOS by zebrafish with large mouthpart size could be ascribed to the increased ingestion of PFOS-enriched EPS aggregates as food. For the chironomid larvae with small mouthpart size, the PFOS-EPS assemblies reduced the dermal, oral and intestinal uptake of PFOS. The nano-visualization evidences confirmed that the PFOS-enriched EPS-PFOS assemblies blocked PFOS penetration through skin of both animals. These findings provide novel knowledge about the ecological risk of PFOS in aquatic environments.
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Affiliation(s)
- Shuyan Xu
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Pengfeng Zhu
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Caiqin Wang
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Daoyong Zhang
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Ming Zhang
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Xiangliang Pan
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, China.
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Penalva-Olcina R, Juan C, Fernández-Franzón M, Vehniäinen ER, Juan-García A. Daphnia magna model for the study of mycotoxins present in food: Gliotoxin, ochratoxin A and its combination. Food Chem Toxicol 2024; 189:114740. [PMID: 38759715 DOI: 10.1016/j.fct.2024.114740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 05/02/2024] [Accepted: 05/13/2024] [Indexed: 05/19/2024]
Abstract
Mycotoxins are low molecular weight compounds present in food and feed. Although their effects on human health have been widely described, their mechanisms of action are still undefined. Gliotoxin (GTX) and ochratoxin A (OTA) are among the most dangerous mycotoxins produced by Aspergillus spp. Therefore, their toxicity was studied in the Daphnia magna model, which has high capacity to predict cytotoxicity and assess ecotoxicity, comparable to mammalian models. The study consisted of a series of tests to evaluate the effects of mycotoxins GTX, OTA and their combinations at different dilutions on Daphnia magna that were conducted according to standardized OECD 202 and 211 guidelines. The following assays were carried out: acute toxicity test, heartbeat, delayed toxicity test, reproduction, growth rate test. Reproducibility was determined by observing the offspring after 21 days of GTX exposure. In acute and delayed toxicity transcript levels of genes involved in xenobiotic metabolism (mox, gst, abcb1, and abcc5), and oxidative stress (vtg-SOD) were analyzed by qPCR. GTX showed acute toxicity and decreased heart rate in D. magna compared to OTA. On the other hand, OTA showed a delayed effect as evidenced by the immobility test. Both mycotoxins showed to increase genes involved in xenobiotic metabolism, while only the mycotoxin mixture increased oxidative stress. These results suggest that the mycotoxins tested could have negative impact on the environment and human health.
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Affiliation(s)
- Raquel Penalva-Olcina
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy and Food Science, Av. Vicent Andrés Estellés S/n, 46100, Burjassot, University of Valencia, València, Spain; Department of Biological and Environmental Science, PO Box 35, FI-40014, University of Jyväskylä, Jyväskylä, Finland
| | - Cristina Juan
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy and Food Science, Av. Vicent Andrés Estellés S/n, 46100, Burjassot, University of Valencia, València, Spain
| | - Mónica Fernández-Franzón
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy and Food Science, Av. Vicent Andrés Estellés S/n, 46100, Burjassot, University of Valencia, València, Spain
| | - Eeva-Riikka Vehniäinen
- Department of Biological and Environmental Science, PO Box 35, FI-40014, University of Jyväskylä, Jyväskylä, Finland
| | - Ana Juan-García
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy and Food Science, Av. Vicent Andrés Estellés S/n, 46100, Burjassot, University of Valencia, València, Spain.
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Jing M, Lin J, Tao J, Yan H, Huang JH. Matrix in River Water, Sediments, and Biofilms Mitigates Mercury Toxicity to Medaka ( Oryzias Latipes). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:21337-21347. [PMID: 38059579 DOI: 10.1021/acs.est.3c05408] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Impacts of an environmental matrix on mercury (Hg) bioavailability and toxicity to medaka (Oryzias latipes) were investigated in matrix-free controls and treatments with a stepwise increased environmental matrix of river water, sediments, and biofilms. Generally, river water enhanced but the presence of sediments and biofilms reduced Hg bioavailability to medaka up to 105 times, so that Hgtotal concentrations/amounts among different environmental media cannot mirror Hg availability and toxicity to medaka. On average, 12.9 and 12.4% of Hg in medaka was, respectively, methylated to methylmercury (MeHg) in matrix-free and -containing treatments, indicating no influence of the environmental matrix on Hg methylation in medaka. All oxidative stress, inflammatory injury, and malformation parameters correlated strongly and significantly with Hgtotal and MeHg concentrations in medaka, notably with steeper slopes in matrix-free controls than in matrix-containing treatments, highlighting that the environmental matrix mitigated Hg and MeHg toxicity to medaka. Moreover, oxidative stress was more strongly mitigated than inflammatory injury according to the stronger decreases of the regression line slopes from matrix-free to -containing treatments. Here, we have newly identified that the potential of the environmental matrix to decrease Hg bioavailability and mitigate Hg toxicity to fish together could buffer Hg ecotoxicity in the aquatic environment.
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Affiliation(s)
- Min Jing
- School of Public Health, the Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, P. R. China
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
| | - Jing Lin
- School of Public Health, the Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, P. R. China
- Guiyang Center for Disease Control and Prevention, Guiyang 550025, P. R. China
| | - Junyan Tao
- School of Public Health, the Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, P. R. China
| | - Haiyu Yan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
| | - Jen-How Huang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
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Wu S, Zhong J, Lei Q, Song H, Chen SF, Wahla AQ, Bhatt K, Chen S. New roles for Bacillus thuringiensis in the removal of environmental pollutants. ENVIRONMENTAL RESEARCH 2023; 236:116699. [PMID: 37481057 DOI: 10.1016/j.envres.2023.116699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/04/2023] [Accepted: 07/17/2023] [Indexed: 07/24/2023]
Abstract
For a long time, the well-known Gram-positive bacterium Bacillus thuringiensis (Bt) has been extensively studied and developed as a biological insecticide for Lepidoptera and Coleoptera pests due to its ability to secrete a large number of specific insecticidal proteins. In recent years, studies have found that Bt strains can also potentially biodegrade residual pollutants in the environment. Many researchers have isolated Bt strains from multiple sites polluted by exogenous compounds and characterized and identified their xenobiotic-degrading potential. Furthermore, its pathway for degradation was also investigated at molecular level, and a number of major genes/enzymes responsible for degradation have been explored. At present, a variety of xenobiotics involved in degradation in Bt have been reported, including inorganic pollutants (used in the field of heavy metal biosorption and recovery and precious metal recovery and regeneration), pesticides (chlorpyrifos, cypermethrin, 2,2-dichloropropionic acid, etc.), organic tin, petroleum and polycyclic aromatic hydrocarbons, reactive dyes (congo red, methyl orange, methyl blue, etc.), and ibuprofen, among others. In this paper, the biodegrading ability of Bt is reviewed according to the categories of related pollutants, so as to emphasize that Bt is a powerful agent for removing environmental pollutants.
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Affiliation(s)
- Siyi Wu
- National Key Laboratory of Green Pesticide, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Jianfeng Zhong
- National Key Laboratory of Green Pesticide, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Qiqi Lei
- National Key Laboratory of Green Pesticide, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Haoran Song
- National Key Laboratory of Green Pesticide, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Shao-Fang Chen
- National Key Laboratory of Green Pesticide, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Abdul Qadeer Wahla
- National Institute for Biotechnology and Genetic Engineering College, Pakistan Institute of Engineering and Applied Sciences (NIBGE-C, PIEAS), Faisalabad 38000, Punjab, Pakistan
| | - Kalpana Bhatt
- Department of Food Science, Purdue University, West Lafayette, IN, USA.
| | - Shaohua Chen
- National Key Laboratory of Green Pesticide, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China.
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5
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Juan-García A, Pakkanen H, Juan C, Vehniäinen ER. Alterations in Daphnia magna exposed to enniatin B and beauvericin provide additional value as environmental indicators. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 249:114427. [PMID: 36516623 DOI: 10.1016/j.ecoenv.2022.114427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/08/2022] [Accepted: 12/11/2022] [Indexed: 06/17/2023]
Abstract
Mycotoxins beauvericin (BEA) and enniatin B (ENN B) affect negatively several systems and demand more studies as the mechanisms are still unclear. The simultaneous presence of contaminants in the environment manifests consequences of exposure for both animals and flora. Daphnia magna is considered an ideal invertebrate to detect effects of toxic compounds and environmental alterations. In this study, the potential toxicity and the basic mechanism of BEA and ENN B individually and combined were studied in D. magna. Acute and delayed toxicity were evaluated, and transcript levels of genes involved in xenobiotic metabolism (mox, gst, abcb1, and abcc5), reproduction, and oxidative stress (vtg-SOD) were analyzed by qPCR. Though no acute toxicity was found, results revealed a spinning around and circular profile of swimming, a strong decrease of survival after 72 h for BEA and ENN B at 16 µM and 6.25 µM, respectively, while for BEA + ENN B [8 + 1.6] µM after 96 h. The amount of mycotoxin remaining in the media revealed that the higher the concentration assayed the higher the amount remaining in the media. Differential regulation of genes suggests that xenobiotic metabolism is affected denoting different effects on transcription for tested mycotoxins. The results provide new insights into the underlying risk assessment of BEA and ENN B not only through food for consumers but also for the environment.
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Affiliation(s)
- Ana Juan-García
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy, University of Valencia, Av. Vicent Andrés Estellés s/n, 46100 Burjassot, València, Spain; Department of Biological and Environmental Science, University of Jyväskylä, Survontie 9C, FI-40014 Jyväskylä, Finland.
| | - Hannu Pakkanen
- Department of Biological and Environmental Science, University of Jyväskylä, Survontie 9C, FI-40014 Jyväskylä, Finland
| | - Cristina Juan
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy, University of Valencia, Av. Vicent Andrés Estellés s/n, 46100 Burjassot, València, Spain
| | - Eeva-Riikka Vehniäinen
- Department of Biological and Environmental Science, University of Jyväskylä, Survontie 9C, FI-40014 Jyväskylä, Finland
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6
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Lewis AJ, Yun X, Spooner DE, Kurz MJ, McKenzie ER, Sales CM. Exposure pathways and bioaccumulation of per- and polyfluoroalkyl substances in freshwater aquatic ecosystems: Key considerations. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 822:153561. [PMID: 35101505 DOI: 10.1016/j.scitotenv.2022.153561] [Citation(s) in RCA: 44] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/22/2022] [Accepted: 01/26/2022] [Indexed: 05/24/2023]
Abstract
Due to the bioaccumulative behavior, toxicity, and recalcitrance to degradation, per- and polyfluoroalkyl substances (PFAS) are a focus for many researchers investigating freshwater aquatic ecosystems. PFAS are a diverse set of chemicals that accumulate and transport quite differently in the environment depending on the length of their fluoroalkyl chains and their functional groups. This diversity in PFAS chemical characteristics combined with varying environmental factors also impact the bioaccumulation of these compounds in different organisms. In this review, we evaluate environmental factors (such as organic carbon, proteins, lipids, and dissolved cations) as well as PFAS characteristics (head group, chain-length, and concentration) that contribute to the significant variation seen in the literature of bioaccumulation metrics reported for organisms in aquatic ecosystems. Of the factors evaluated, it was found that PFAS concentration, dissolved organic matter, sediment organic matter, and biotransformation of precursor PFAS tended to significantly impact reported bioaccumulation metrics the most. Based on this review, it is highly suggested that future studies provide sufficient details of important environmental factors, specific organism traits/ behavior, and PFAS concentrations/compounds when reporting on bioaccumulation metrics to further fill data gaps and improve our understanding of PFAS in aquatic ecosystems.
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Affiliation(s)
- Asa J Lewis
- Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA 19104, USA.
| | - Xiaoyan Yun
- Civil and Environmental Engineering Department, Temple University, Philadelphia, PA 19122, USA
| | - Daniel E Spooner
- Department of Biology, Lock Haven University, Lock Haven, PA 17745, USA
| | - Marie J Kurz
- Academy of Natural Sciences of Drexel University, Philadelphia, PA 19103, USA
| | - Erica R McKenzie
- Civil and Environmental Engineering Department, Temple University, Philadelphia, PA 19122, USA
| | - Christopher M Sales
- Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA 19104, USA
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7
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Simmatis B, Rühland KM, Evans M, Meyer-Jacob C, Kirk J, Muir DCG, Smol JP. Metal contamination in alkaline Phantom Lake (Flin Flon, Manitoba, Canada) generates strong responses in multiple paleolimnological proxies. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 811:152299. [PMID: 34896499 DOI: 10.1016/j.scitotenv.2021.152299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 12/01/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
The copper-zinc smelter at Flin Flon (Manitoba) operated between 1930 and 2010 and emitted large amounts of metal(loid)s and sulphur dioxide into the atmosphere, damaging the surrounding terrestrial landscapes and depositing airborne industrial pollutants into aquatic ecosystems. However, the extent of biological impairment in regional lakes is largely unknown. Here, we analysed biological and geochemical proxies preserved in a dated sediment core from Phantom Lake, collected seven years after the smelter closed in 2010. Our objectives were to determine how smelting history affected long-term trends in (1) sedimentary elements, (2) biota across multiple trophic levels, and (3) spectrally-inferred chlorophyll a and lake-water total organic carbon. The effects of smelting activities were clearest in the diatom record, in concordance with modest responses in chironomid and cladoceran assemblages. Several metal(loid)s were naturally high and exceeded sediment quality guidelines during the pre-smelting era. With the opening of the smelter, metal(loid) concentrations in sediments increased through the 1930s, peaked in the 1960s, and declined thereafter with technological improvements but remained above background to this day. Although modest declines in inferred lake-water total organic carbon indicate reduced terrestrial carbon supply following sulphate deposition in the catchment, the diatom record showed no evidence of acidification as the lake was and remained well-buffered. Pre-smelting diatom and invertebrate assemblages were diverse and indicated oligo-mesotrophic conditions. Smelting was associated with the loss of metal-sensitive biological indicators and the emergence of assemblages dominated by metal-tolerant, generalist taxa. Diatoms tracked substantial reductions in aerial emissions since the 1990s, particularly after the smelter closed, but also indicated that the biological effects of metal pollution persist in Phantom Lake. Examining the effects of a base metal smelter on a well-buffered lake offered insights into multi-trophic level responses to severe metal contamination and potential recovery without the confounding effects of concurrent changes in lake acidity.
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Affiliation(s)
- Brigitte Simmatis
- Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, 116 Barrie St., Kingston, ON K7L 3N6, Canada.
| | - Kathleen M Rühland
- Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, 116 Barrie St., Kingston, ON K7L 3N6, Canada
| | - Marlene Evans
- Environment and Climate Change Canada, 11 Innovation Blvd., Saskatoon, SK S7N 3H5, Canada
| | - Carsten Meyer-Jacob
- Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, 116 Barrie St., Kingston, ON K7L 3N6, Canada
| | - Jane Kirk
- Environment and Climate Change Canada, 867 Lakeshore Rd., Burlington, ON L7S 1A1, Canada
| | - Derek C G Muir
- Environment and Climate Change Canada, 867 Lakeshore Rd., Burlington, ON L7S 1A1, Canada
| | - John P Smol
- Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, 116 Barrie St., Kingston, ON K7L 3N6, Canada
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Cao Z, Li P, Li ZH. A latest review on the application of microcosm model in environmental research. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:60438-60447. [PMID: 34537949 DOI: 10.1007/s11356-021-16424-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 09/05/2021] [Indexed: 06/13/2023]
Abstract
Microcosms are used experimentally to simulate ecosystems. This technology has received increasing attention and is widely used for environmental research. This review briefly introduces the origin and development of microcosm theory, summarizes classification and applications of microcosms across decades, and describes the advantages and limitations of microcosm technology in comparison with other methods. Finally, trends in the development of microcosm models are discussed.
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Affiliation(s)
- Zhihan Cao
- Marine College, Shandong University, Weihai, 264209, Shandong, China
| | - Ping Li
- Marine College, Shandong University, Weihai, 264209, Shandong, China.
| | - Zhi-Hua Li
- Marine College, Shandong University, Weihai, 264209, Shandong, China.
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9
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Issa S, Simonsen A, Jaspers VLB, Einum S. Population dynamics and resting egg production in Daphnia: Interactive effects of mercury, population density and temperature. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 755:143625. [PMID: 33221017 DOI: 10.1016/j.scitotenv.2020.143625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/02/2020] [Accepted: 11/08/2020] [Indexed: 06/11/2023]
Abstract
Toxicity studies on freshwater organisms are commonly conducted by quantifying effects on asexual (clonal) reproductive rates in Daphnia, whereas studies of effects on sexual reproductive rates remain relatively rare. Sexual reproduction in Daphnia and the associated production of resting eggs allows them to survive unfavorable environmental conditions and is thus a crucial component of their long-term fitness. It also maintains genetic diversity within Daphnia populations and hence their potential for adaptation to new environmental conditions. This aspect of their biology may therefore be important to consider in toxicity studies. The aim of this study was to investigate for the first time how mercury (Hg) affects sexual versus asexual reproduction in Daphnia under varying environmental conditions. Specifically, we experimentally tested the interactive effects of Hg and temperature on the population dynamics of Daphnia magna. For this purpose, we exposed D. magna to environmentally relevant concentrations (0 μg/L, 0.5 μg/L and 2 μg/L) of Hg (in the form of mercury (II) chloride) found in stream water and measured biomass growth rate resulting from asexual reproduction, and resting egg production resulting from sexual reproduction. This was done at both 17 °C and 24 °C. Biomass growth rate did not vary across Hg treatments and depended mainly on temperature and population density. Density dependence of biomass growth rate was indeed more pronounced at 24 °C than at 17 °C, as resource limitation from intraspecific competition was further exacerbated by the rise in feeding rates with temperature. Density dependence of resting egg production was unaffected by Hg and temperature, but resting egg production was higher under Hg exposure at low temperature. These findings show that depending on environmental conditions, rates of sexual reproduction in D. magna may respond to metal exposure at lower concentrations than those impacting population growth during the asexual phase.
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Affiliation(s)
- Semona Issa
- Centre for Biodiversity Dynamics (CBD), Department of Biology, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway.
| | - Ane Simonsen
- Department of Biology, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway
| | - Veerle L B Jaspers
- Department of Biology, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway
| | - Sigurd Einum
- Centre for Biodiversity Dynamics (CBD), Department of Biology, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway
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