Acute and Chronic Toxicity to Daphnia magna of Diuron and Capsaicin Used in Antifouling Paints

We assessed the chronic toxicity of nitrite to Daphnia similoides and modeled the concentration–response function of nitrite on survival, molting, and reproduction. Survival time, number of molting, number of total offspring per female, number of broods per female, and number of offspring per brood decreased significantly with increasing NO2–N concentration during the 21-day experiment. The EC50s for number of total offspring per female, number of broods per female, and number of offspring per brood were 1.56, 3.99, and 1.71 mg L−1, respectively. A four-parameter logistic model was suitable for describing the concentration–response function and allows the estimation of reproduction indices of D. similoides at any given concentration of NO2–N.

Plastics have benefited our lives in many ways, but their long persistence in the environment causes serious problems. Rapid decomposition and detoxification of plastics after use are significant challenges. As a possible solution, biodegradable plastics have attracted attention, and for environmental risk assessment research on polymer toxicity, use of indicator organisms, like water fleas and fish, has increased globally. However, such research often focuses on standardized substances without considering changes in toxicity due to plastic degradation products. Additionally, tests generally focus on acute toxicity, while long-term effects on organismal reproduction and lifespan are largely unknown. Understanding the impact of degraded polymers on biological activities is crucial for accurate risk assessment. In this study, we investigated the biological toxicity of substances generated during degradation of polycaprolactone (PCL), a common biodegradable plastic, using the indicator organism, Daphnia magna. We examined PCL, oligocaprolactones (OCLs), and monomers resulting from polymer cleavage, as well as carbodiimides, added during polyester synthesis. As a result, PCL, which is insoluble in water, reduced individual survival and total number of offspring at an exposure concentration of 100 mg/L, while no toxicity was observed for water-soluble degradation products, OCLs, and monomers. Furthermore, carbodiimides, which are expected to be released during PCL degradation, showed strong toxicity, significantly reducing individual survival and total number of offspring at 0.1-10mg/L. These findings suggest that changes in physical properties due to polymer degradation and release of additives can significantly alter their toxicity.

The effects of 1-hexyl-3-methylimidazolium bromide on embryonic development and reproduction in Daphnia magna.

Summary Periods of hypoxia lasting up to weeks are now anticipated in fresh waters, owing to anthropogenic influences. However, the cumulative effects of hypoxia on Daphnia, over multiple broods, have received virtually no attention, and to establish and evaluate such responses there is a need to make measurements over a wide range of oxygen concentrations, potentially revealing non‐linear patterns. We predict that the effect of hypoxia on growth, survival and fecundity (i.e., production of new individuals) of Daphnia will increase over multiple broods, and with increasing oxygen these responses will approach asymptotic maxima, following a rectangular hyperbolic response. Daphnia similoides were exposed to 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 and 8.0 mg oxygen L−1. To determine effects on the first brood we examined: number of offspring; time to the first eggs; time to the first brood and size of the female at the first eggs and the first brood. To determine cumulative effects of oxygen over multiple broods (up to 8 broods over 21 days), we measured: total number of offspring produced by a female; survival time and total number of moults and broods. To investigate how the cumulative effects arose over the multiple broods, we examined the number of offspring per brood in each brood over eight broods. To assess treatment effects and indicate responses, functions were fit to data using the most parsimonious function that reflected trends in the data. Measurements associated with a single brood responded linearly, or not at all, with changing oxygen concentration, whereas measurements made over the 21 days followed a rectangular hyperbolic response, increasing to an asymptote as oxygen increased. For the first brood, as oxygen concentration was raised from 1 to 8 mg L−1 the number of offspring produced and the time required to produce the brood were not affected; the time required to produce eggs decreased ˜0.3‐fold; and the size of individuals at the time when the eggs and the brood were produced increased ˜0.1‐fold. Over the 21 days, between 1 and 8 mg L−1 the total number of offspring increased ˜3.4‐fold; individual survival and the number of moults increased ˜2‐fold, and the number of broods increased ˜1‐fold. For single‐brood responses, there was no effect of decreasing oxygen levels on the number of offspring in the first brood, but there were negative effects on the second‐to‐fourth broods; the number of offspring in the remaining broods was not significantly related to oxygen levels, as there were fewer data at low levels due to poor survival. We conclude that assessments of Daphnia demographics should not rely on estimates of the effect of oxygen concentration on single broods. Instead, studies should consider cumulative changes over multiple broods. Following our approach, researchers may now explore the impacts of hypoxia on congeners and other zooplankton, and investigate the mechanisms associated with multi‐brood responses.

Assessing the chronic toxicity of climbazole to Daphnia magna: Physiological, biochemical, molecular, and reproductive perspectives

The degradation of cyanobacterial blooms often causes hypoxia and elevated concentrations of ammonia, which can aggravate the adverse effects of blooms on aquatic organisms. However, it is not clear how one stressor would work in the presence of other coexistent stressors. We studied the toxic effects of elevated ammonia under hypoxia using a common yet important cladoceran species Daphnia similis isolated from heavily eutrophicated Lake Taihu. A 3 × 2 factorial experimental design was conducted with animals exposed to three un-ionized ammonia levels under two dissolved oxygen levels. Experiments lasted for 14 days and we recorded the life-history traits such as survival, molt, maturation, and fecundity. Results showed that hypoxia significantly decreased survival time and the number of molts of D. similis, whereas ammonia had no effect on them. Elevated ammonia significantly delayed development to maturity in tested animals and decreased their body sizes at maturity. Both ammonia and hypoxia were significantly detrimental to the number of broods, the number of offspring per female, and the number of total offspring per female, and significantly synergistic interactions were detected. Our data clearly demonstrate that elevated ammonia and hypoxia derived from cyanobacterial blooms synergistically affect the cladoceran D. similis.

Effects of polyvinyl chloride microplastics on reproduction, oxidative stress and reproduction and detoxification-related genes in Daphnia magna

Daphnia magna were exposed under semistatic conditions (i.e., conditions taking natural degradation into account) to a pesticide mixture consisting of a pyrethroid insecticide (cyfluthrin) and a pre-emergent herbicide (diuron) as well as pesticides individually using a full life cycle exposure (21days). Subsequently, offspring from the second reproductive brood were used to continue exposure for a second generation. Survival, time to first brood, total number of offspring produced, number of broods produced, growth rate, and population growth rate were recorded for each generation and concentration. Significant differences existed between F0 and F1 D.magna for survival, in which F1 were less sensitive to pesticide mixtures than F0. In addition, F1 D. magna were significantly smaller than F0, which resulted in longer time to first brood. There were no differences in any end point examined between D.magna exposed to the pesticide mixture and diuron alone, although differences existed in survival, total number of offspring, total number of broods, and population growth rate when F0 D.magna were exposed to cyfluthrin alone. This study illustrates the utility of a two-generation study design that may more fully reflect, and more accurately predict, population level effects of pesticide exposures to short-lived aquatic organisms.

Evaluation of the Daphnia magna reproduction test for detecting endocrine disruptors

In the present study, the 3-year breeding behavior of the parent dogs in a Pomeranian farm was followed, and the effects of season and insemination method on their reproductive performance were investigated. The gestation period was 62.4 days, the age at which sexual maturity is reached was 404.4 days and the average period between two estruses was found as 205.2 days. The mean number of offspring, and the mean number of male and female puppies were found as 3.4, 2.15 and 1.4 respectively. The stillbirth rate was found as 1.4% and the survival rate to 1 year was 83.3%. The pregnancy rate, the average number of female puppies, the number of stillbirths and the total number of offspring were found to be similar in naturally and artificially inseminated females (P>0.05). While 47.6% of estruses were seen in the spring-summer months, 52.4% were seen in the autumn-winter months (P>0.05). The mating season did not affect the number of female offspring, the stillbirth rate or the total number of offspring (P>0.05). However, when compared to the spring-summer months, the mortality rate of females up to 1 year of age showing estrus in the autumn-winter season was found to be significantly higher (P<0.01).

Progress of research on the toxicology of antibiotic pollution in aquatic organisms

Effects of microplastics on key reproductive and biochemical endpoints of the freshwater microcrustacean Daphnia magna

Toxicology of aquatic pollution: Physiological, molecular and cellular approaches: Edited by E.W. Taylor; Society for Experimental Biology, Seminar Series 57; Cambridge University Press, Cambridge; 1996; 283 pp.; GBP 55.00, US$ 85.00; ISBN 0-521-45524-3

Estimating genetic and environmental components of variance using sexual and clonal Artemia

Elevated temperature alleviates benzophenone-3 toxicity in Daphnia magna