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Ho Chi Minh City, Vietnam

Ortiz-Rodriguez R.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Son Dao T.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Son Dao T.,Institute for Environment and Resources | Wiegand C.,University of Southern Denmark
Journal of Experimental Biology | Year: 2012

Anthropogenic and climate factors increase the frequency of problematic cyanobacterial blooms in freshwater. Among other toxins, some cyanobacteria produce microcystins (MCs), which inhibit phosphatases type 1 and type 2A and provokes oxidative stress. Toxic cyanobacteria affect the growth, survival and reproduction of zooplankton, particularly those from the genus Daphnia, which have a central position in pelagic food webs. However, one possibility to ameliorate effects is to biotransform MC via glutathione S transferase (GST) to a less toxic glutathione conjugate. This process was hypothesised to underlie the ability of Daphnia to withstand MC and to explain the enhanced tolerance of the offspring from mothers exposed to toxic cyanobacteria. Thus we conducted multigenerational experiments with D. magna, exposing the parental generation to MC for 1 or 7?days and determining the enzyme-mediated tolerance to MC in their offspring by assessing the acute effect of MC on biotransformation and antioxidant and metabolism enzymes, and through 21?day chronic tests on toxicity and growth. Seven days of exposure of the parental generation to MC induced higher activity of GST and malate dehydrogenase in the offspring and enabled them to increment the catalase activity when challenged with MC, whereas 1?day of exposure of the parental generation did not. Offspring from non-exposed and 1-day-exposed mothers suffered decreased survival when exposed to MC compared with offspring from 7- day-exposed mothers; survival was correlated with the elevated activity of GST, malate dehydrogenase and catalase, suggesting maternal transfer of activation factors. However, increased survival occurred at the expense of individual growth. These results suggest that transgenerational effects are provoked by MC in D. magna, which may explain the observed acquirement of enhanced tolerance over generations. © 2012. Published by The Company of Biologists Ltd. Source


Duong T.T.,Vietnam Academy of Science and Technology | Le T.P.Q.,Vietnam Academy of Science and Technology | Dao T.-S.,Institute for Environment and Resources | Pflugmacher S.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | And 5 more authors.
Journal of Applied Phycology | Year: 2013

In order to understand the environmental variables which promote the proliferation of cyanobacteria and variation in microcystin concentrations in the Nui Coc reservoir, Vietnam, physicochemical parameters, the occurrence, and abundance of phytoplankton, cyanobacteria, and microcystin concentration were monitored monthly through the year 2009-2010. The relationships between these parameters were explored using principal component analysis (PCA) and Pearson correlation analysis. The phytoplankton community was mainly dominated by the cyanobacterium Microcystis with higher cyanobacteria abundance during summer and autumn season. PCA and Pearson correlation results showed that water temperature and phosphate concentration were the most important variables accounting for cyanobacteria, Microcystis, and microcystin occurrence. Analysis of the toxins by high-performance liquid chromatography demonstrated the presence of two microcystin variants: microcystin-LR (MC-RR) and microcystin-ddRR (MC-ddRR) with total concentrations of the toxins in filtered samples from surface water ranging from 0.11 to 1.52 μg MC-LR equiv L-1. The high concentrations of microcystin in the Nui Coc reservoir highlighted the potential risk for human health in the basin. Our study underlined the need for regular monitoring of cyanobacteria and toxins in lakes and reservoirs, which are used for drinking water supplies, not only in Vietnam but also in tropical countries. © 2012 Springer Science+Business Media Dordrecht. Source


Hoang T.T.T.,Hochiminh City University for Natural Resources and Environment | Tu L.T.C.,Hochiminh City University for Natural Resources and Environment | Le N.P.,Hochiminh City University for Natural science | Dao Q.P.,Institute for Environment and Resources
International Journal of Phytoremediation | Year: 2012

In Vietnam's coastal wetlands, fluoroquinolones, a widely used class of antibiotics in shrimp farming, are frequently detected in sediments of former shrimp farms. This phenomenon could lead to negative impacts on the aquatic ecosystem, since the antibiotic residues could induce changes in the microorganism communities of the water body. The potential of native wetland plants (Acrostichum aureum L. and Rhizophora apiculata Blume Fl. Javae) for phytoremediation of fluoroquinolones (ciprofloxacin and norfloxacin) was investigated. The half-life for each antibiotic was estimated at approximately 10 days in the planted sediment. With respect to the accumulation of ciprofloxacin and norfloxacin in plants, these antibiotics were found mainly in roots. Antibiotic translocation from root to stem and leaves occurred at a low rate. The results showed that A. aureum and R. apiculata can be valuable for the phytoremediation of antibiotic-contaminated sediments. Additionally, the initial findings of the presence of resistant bacteria indicated that bacteria could play a role in facilitating the phytodegradation. © 2012 Copyright Taylor and Francis Group, LLC. Source


Hoang T.T.T.,Hochiminh City University of Natural Resources and Environment | Tu L.T.C.,Hochiminh City University of Natural Resources and Environment | Le N.P.,Hochiminh City University of Natural science | Dao Q.P.,Institute for Environment and Resources | Trinh P.H.,Institute for Environment and Resources
Wetlands Ecology and Management | Year: 2012

Vietnamese coastal wetlands have traditionally been used for shrimp farming, but with the expansion of commercial shrimp farming and the associated clearance of mangroves, these valuable ecosystems have been rapidly degraded. The application of veterinary antibiotics in shrimp culture is one of the major threats to Vietnamese mangroves. These antibiotics are released into the environment through wastewater streams from shrimp ponds and cause environmental problems as well as the occurrence of antibiotic resistant bacteria. However, there is only a limited amount of information available on the occurrence and fate of antibiotics in Vietnamese mangroves. Ciprofloxacin and norfloxacin are two of most commonly fluoroquinolones used in shrimp culture. Laboratory experiments were therefore carried out using saline shrimp pond water to investigate the fate of both antibiotics in a coastal wetland ecosystem. Furthermore, two wetland plant species (Ceratophyllum demersum and Chrysopogon zizanioides), were used for studying phytoremediation of both antibiotics through a hydroponic experiment. Both ciprofloxacin and norfloxacin were photodegradable but at a slow rate, whereas the biodegradation seemed to be insignificant. If given at an initial concentration of 5 or 10 mg/L, a higher removal of antibiotics was achieved using C. demersum: 40 % for norfloxacin and 44-39 % for ciprofloxacin, respectively. With C. zizanioides, ciprofloxacin and norfloxacin were reduced by 40-38 and 36-34 %, respectively. These results indicated that phytoremediation could be effective in the removal of both antibiotics. © 2012 Springer Science+Business Media B.V. Source


Dao T.-S.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Dao T.-S.,Institute for Environment and Resources | Ortiz-Rodriguez R.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Do-Hong L.-C.,Vietnam National University, Ho Chi Minh City | Wiegand C.,University of Southern Denmark
International Review of Hydrobiology | Year: 2013

Cyanobacterial blooms affect aquatic ecosystems due to their capability of producing cyanotoxins (e.g., microcystins, MC; cylindrospermopsin, CYN) and other bioactive compounds. Filter feeding zooplankton are amongst the first organisms affected and research has mainly focused on their interactions with toxic cyanobacteria. We investigated oxidative stress, biotransformation and energetic responses of Daphnia magna after exposure to cyanobacterial extracts and behavioral changes of the animals exposed to living cells of non-MC and non-CYN producing strains. Enzyme and energetic responses were measured in time kinetic experiments, using extracts of Microcystis botrys, M. wesenbergii, Aphanizomenon aphanizomenoides, Cylindrospermopsis raciborskii, corresponding to 10mg DWL-1. In behavioral experiments, D. magna was exposed to living cells of Microcystis aeruginosa, A. aphanizomenoides, Dolichospermum circinalis, C. raciborskii, at the density of 400000cellsmL-1 using a Daphnia toximeter equipment. Despite not producing MC or CYN, some cyanobacterial extracts caused significant increase of biotransformation enzyme, especially catalase, activities from the exposed D. magna after a longer incubation. Total carbohydrates and glycogen contents were increased but the activity of one of the involved enzymes, the malate dehydrogenase, was not changed. Animals' behavior (e.g., swimming, position within water column) was altered in exposures to cultures of C. raciborskii and D. circinalis. These physiological and behavioral alterations indicate stress, which may impair overall performance of zooplankton at the environmental realistic chronic exposure scenario. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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