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Tropical coastal areas are increasingly exposed to temperature extremes from marine heatwaves and contaminants from anthropogenic activities. The interactive effects of these environmental changes on marine life are understudied. We investigated the direct and cross-generational effects of copper (Cu) on F0 and F1 generations of the common tropical copepod Pseudodiaptomus annandalei under extreme temperatures (30 and 34 °C). In F0, Cu exposure reduced survival and nauplii production; these patterns were more pronounced at 34 °C and in females. F0 Copepods produced more faecal pellets at 34 °C than 30 °C, indicating a higher energetic demand. In F1, the number of F1 adults was lower in CuF0 and at 34 °C. Cu-exposed F0 produced larger adult F1, while exposure to 34 °C resulted in smaller adult F1. Our results show that tropical copepods are highly vulnerable to the interactive effects of contaminants and extreme temperatures.

Metal contamination and pollution are of human and environmental concern Phytoremediation is one of the suitable high-efficiency means to treat metal pollution. This study aims to observe the responses of Pisum sativum L. in its early life stage to three metals, arsenic (As), copper (Cu) and lead (Pb) in laboratory conditions. Seeds of P. sativum were treated with water containing 0, 50, and 500 μg/l of these metals over a period of 7 days. The results show that the germination of seeds is similar for the control and metal treatments, ranging from 90-100% after 4 days of watering. Shoot development of the seeds exposed to the metals and the control were not significantly different, except that the samples which had undergone the treatment with 500 μg Pb/l had longer shoots. Our results evidence a high capacity for metal tolerance in this plant in the early stages of its life. Therefore, P. sativum may be a promising candidate for the phytoremediation of metal contamination and pollution.

International audience; The mass development and expansion of cyanobacteria release cyanotoxins in the aquatic environment and cause serious problems for grazers such as micro-zooplankton. In contrast to aquatic ecosystems in temperate regions, impacts of cyanobacteria and their toxins on tropical micro-crustaceans are relatively understudied. In this study, acute and chronic effects of pure microcystin-LR (MC-LR), a crude extract of water bloom sample with a dominance of Microcystis aeruginosa containing microcystins (MCE) and living cells of Cylindrospermopsis curvispora were tested on a tropical micro-crustacean, Daphnia lumholtzi. The 24 h- and 48 h-LC50 values for MC-LR ranged from 247–299, and 331–409 μg MCE L−1, respectively. Exposures to 1–25 μg MCE L−1 decreased survival, fecundity, and reproduction of D. lumholtzi. The impacts of C. curvispora cells on life-history traits of D. lumholtzi were density-dependent and more severe than the impacts of dissolved microcystins. It could be that the adverse effects of C. curvispora on D. lumholtzi are linked to a combination of potential toxic metabolites, mal-nutrients, feeding and swimming interference. Daphnia lumholtzi used in this study is more sensitive to microcystins compared to Daphnia species from temperate regions. Therefore, we highly suggest using D. lumholtzi as a model species for toxicity testing and monitoring on water quality, particularly in tropical countries.

International audience; Metal contamination is one of the major issues to the environment worldwide, yet it is poorly known how exposure to metals affects tropical species. We assessed the sensitivity of a tropical micro-crustacean Daphnia lumholtzi to three trace metals: copper (Cu), zinc (Zn) and nickel (Ni). Both, acute and chronic toxicity tests were conducted with metals dissolved in in situ water collected from two sites in the lower part of the Mekong River. In the acute toxicity test, D. lumholtzi neonates were exposed to Cu (3-30 mu g L-1), Zn (50-540 mu g L-1) or Ni (46-2356 mu g L-1) for 48 h. The values of median lethal concentrations (48 h-LC50) were 11.57-16.67 mu g Cu L-1, 179.3-280.9 mu g Zn L-1, and 1026-1516 mu g Ni L-1. In the chronic toxicity test, animals were exposed to Cu (3 and 4 mu g L-1), Zn (50 and 56 mu g L-1), and Ni (six concentrations from 5 to 302 mu g L-1) for 21 days. The concentrations of 4 mu g Cu L-1 and 6 mu g Ni L-1 enhanced the body length of D. lumholtzi but 46 mu g Ni L-1 and 50 mu g Zn L-1 resulted in a strong mortality, reduced the body length, postponed the maturation, and lowered the fecundity. The results tentatively suggest that D. lumholtzi showed a higher sensitivity to metals than related species in the temperate region. The results underscore the importance of including the local species in ecological risk assessment in important tropical ecosystems such as the Mekong River to arrive at a better conservational and management plan and regulatory policy to protect freshwater biodiversity from metal contamination. (C) 2016 Elsevier B.V. All rights reserved.

Heavy metal contamination is among the globally environmental and ecological concerns. In this study we assessed the development of the two green algae Schroederia setigera and Selenastrum bibraianum under exposures to 5 – 200 µg/L of Ni, Zn, and Cd in the laboratory conditions. Heavy metal removal efficiency of S. setigera was also tested in 537 µg Ni/L, 734 µg Zn/L, and 858 µg Cd/L. We found that the exposures with these heavy metals caused inhibitory on the growth of S. bibraianum. The S. bibraianum cell size in the 200 µg Zn/L treatment was around two times smaller than the control. However, Zn and Cd at the concentration of 200 µg/L did not inhibit the growth of S. setigera over 18 days of exposure. The S. setigera also grew well during 8 days exposed to Ni at the same concentration. Besides, the alga S. setigera could remove 66% of Zn, 18% of Cd and 12% of Ni out of the test medium after 16 days of incubation. The Vietnam Technical Regulation related to metals should be considered for ecological protection. We recommend to test the metal removal by the alga S. setigera at pilot scale prior to apply it in situ

Climate change and human activities induce an increased frequency and intensity of cyanobacterial blooms which could release toxins to aquatic ecosystems. Zooplankton communities belong to the first affected organisms, but in tropical freshwater ecosystems, this issue has yet been poorly investigated. We tested two questions (i) if the tropical Daphnia lumholtzi is capable to develop tolerance to an ecologically relevant concentration of purified microcystin-LR and microcystins from cyanobacterial extract transferable to F1 and F2 generations? And (ii) would F1 and F2 generations recover if reared in toxin-free medium? To answer these questions, we conducted two full factorial mutigenerational experiments, in which D. lumholtzi was exposed to MC-LR and cyanobacterial extract at the concentration of 1 μg L−1 microcystin continuously for three generations. After each generation, each treatment was spit into two: one reared in the control (toxin free) while the other continued in the respective exposure. Fitness-related traits including survival, maturity age, body length, and fecundity of each D. lumholtzi generation were quantified. Though there were only some weak negative effects of the toxins on the first generation (F0), we found strong direct, accumulated and carried-over impacts of the toxins on life history traits of D. lumholtzi on the F1 and F2, including reductions of survival, and reproduction. The maturity age and body length showed some inconsistent patterns between generations and need further investigations. The survival, maturity age (for extract), and body length (for MC-LR) were only recovered when offspring from toxin exposed mothers were raised in clean medium for two generations. Chronic exposure to long lasting blooms, even at low density, evidently reduces survival of D. lumholtzi in tropical lakes and reservoirs with ecological consequences. Exposure to environmentally relevant concentrations of cyanobacterial toxins for 3 generations tropical Daphnia lumholtzi developed no or marginal tolerance.

In this study, the chronic effects of Ampicillin on survival, reproduction and growth of Daphnia magna was monitored during 21 days exposure test. The results showed that Ampicillin strongly affected on life history traits of Daphnia magna, i.e. 47% reduction of survival proportion, lower 68% reproduction than the control, and reduction in body length and in the intrinsic population rate, especially at its highest concentration. The antibiotics especially Ampicillin should be included int the Vietnam guidelines for environmental and ecological protection.

In this study we evaluated the responses of the tropical micro-crustacean, Daphnia lumholtzi, to zinc (Zn). For a more environmentally realistic assessment on the Zn toxicity, water sample collected from Saigon River was used as medium for the daphnids and Zn was spiked into field water for exposures. River water was physically and chemically measured and analyzed, and the sufficient water quality was confirmed prior to be used for the acute and chronic experiments. Metal concentrations in the test water were determined with an inductively coupled plasma/ mass spectrometry (ICP/MS). In the acute test implementation, Zn concentrations were from 67 – 360 µg/L. In the chronic experiments, the animals were incubated in control (filtered field water only) or filtered field water added with Zn (28, 46, and 75 µg/L) over the period of 14 days. The life history traits of daphnids including the survival, maturation, reproduction were daily observed. The results showed that the value of median lethal concentrations (48h-LC50) was 136 µg Zn/L (95% CI = 107 – 165 µg Zn/L). Chronic exposures revealed that Zn caused the survival reduction, delayed maturity age and reproduction decrease. Our study suggested D. lumholtzi as a very good freshwater aquatic zooplankton for assessment on the toxicity of metals in tropics. Besides, the Vietnam guideline values regarding Zn should be re-considered and adjusted for the aquatic ecological protection.

Cyanobacteria are an essential part of aquatic ecosystems. However, they can cause detrimental impacts on other organisms of higher tropic levels in water bodies because of their potent toxic metabolites (e.g. microcystin) and other bioactive compounds. In this study we tested the long-term and negative effects of two non-microcystin producing cyanobacteria Cylindrospermopsis curvispora and Planktothrix sp. from Vietnam on Daphnia magna under the laboratory conditions. The animal was fed with mixtures of green alga, Scenedesmus sp., and C. curvispora or Planktothrix sp. at different ratios (100 % Scenedesmus, 10 % cyanobacteria + 90 % Scenedesmus, 50 % cyanobacteria + 50 % Scenedesmus, 100 % cyanobacteria) over a period of 21days. The results showed that the D. magna fed with from 10 to 100 % cyanobacteria reduced their survival with density dependence, delayed or postponed its maturation. Besides, the cyanobacteria also inhibited the reproduction of adult D. magna consequently strongly prevent the next population development of D. magna. The species C. curvispora had stronger effect on survival, but less impact on maturation and reproduction of D. magna than Planktothrix sp, negatively. To our knowledge, this is the first report on negative effects of C. curvispora and Planktothrix sp. from Vietnam on life history traits of D. magna. Additionally, our results revealed that even non-microcystin producing cyanobacteria at low density could also have negative impacts on zooplankton consequently ecological balance interference. In situ investigations on the effects of cyanobacteria on zooplankton are suggested for more understanding on the ecological interactions of the two trophic levels of aquatic ecosystem.