Combined Effects of Temperature and the Microcystin MC-LR on the Feeding Behavior of the Rotifer Brachionus calyciflorus

Inhibitory Effects of Antipsychotic Chlorpromazine on the Survival, Reproduction and Population Growth Other Than Neurotransmitters of Zooplankton in Light of Global Warming

Global warming and environmental pollution have created a unique combination of abiotic and biotic stresses to zooplankton. However, little information is available on the effects of antipsychotic drugs commonly used to treat psychosis, such as chlorpromazine (CPZ), on non-target aquatic organisms in light of global warming. This study investigated how dopamine concentrations (DAC), acute toxicity and chronic toxicity of Brachionus calyciflorus changed in response to CPZ and gradually increasing temperatures. The results showed that the concentration range of rotifer DAC was 1.06~2.51 ng/g. At 18, 25 and 32 °C, the 24 h LC50 was 1.795, 1.242 and 0.833 mg/L, respectively. Compared to the control, exposure to CPZ significantly decreased life expectancy at hatching, the net reproduction rate, generation time, population growth rate and dopamine concentration of B. calyciflorus in all three temperatures (p < 0.05). The toxicity of CPZ to rotifers was increased by high temperature. These findings indicated that CPZ is highly toxic to rotifers, displaying high ecological risks to aquatic ecosystems.

Combined Effects of Warming and Imidacloprid on Survival, Reproduction and Population Growth of Brachionus calyciflorus (Rotifera)

Global warming and pesticide contamination are two stressors of high concern, but their combined effects on freshwater biota are controversial. This study investigated the combined effects of warming and imidacloprid (IMI) on survival (measured as life expectancy at hatching), reproduction (net reproductive rate), population growth (intrinsic rate of population increase) and sexual reproduction (proportion of sexual offspring) of Brachionus calyciflorus using a life table experiment. The results showed that compared with controls, treatments with IMI at 50-100 mg/L significantly decreased survival, reproduction and population growth of the rotifers at 20℃. The inhibiting effect at higher IMI concentrations on survival increased with increasing temperatures, but those on reproduction and population growth increased only when the temperature increased from 25℃ to 30℃. The proportion of sexual offspring decreased with increasing temperatures. When monitoring the ecological effects of pollutants, environmental temperature and the possible adaptation of rotifers to it should be taken into consideration.

Combined effects of increased water temperature and cyanobacterial compounds exert heterogeneous effects on survival and ecological processes in key freshwater species

Climate change is increasing water temperature and intensifying the incidence of cyanobacterial blooms worldwide. However, the combined effects of increased temperature and microcystin concentrations as co-stressors on survival and ecological processes in freshwater species are unclear. Here, using purified MC-LR and crude extract of toxigenic Microcystis aeruginosa, we tested the individual and combined effects of three water temperatures (15, 20, 25 °C) and a range of environmentally relevant concentrations of dissolved microcystin and crude extract (0.01–10 µg·L−1) on survival, growth inhibition, grazing and predation rates in three freshwater species: phytoplankton (Scenedesmus quadricauda), zooplankton (Daphnia pulex), and an invertebrate predator (Ischnura elegans). Purified MC-LR exerted a higher growth inhibitory effect on S. quadricauda compared to crude extract with the same concentration of MC-LR, while neither treatment affected its chlorophyll-a content or survival of D. pulex. Crude extract reduced grazing and survival of D. pulex and I. elegans, respectively. The combined effect of higher temperature and crude extract reduced I. elegans survival by 50%. Increased temperature reduced prey handing time in I. elegans by 49%, suggesting a higher predation rate. However, warming together with higher concentrations of crude extract jointly increased zooplankton grazing and reduced damselfly predation. Taken together, these results suggest crude extract, and not necessarily microcystin, can affect survival and productivity in freshwater species, although these effects may vary unevenly across trophic levels. Our findings highlight the importance of complex ecological mechanisms by which warming can exacerbate toxic effects of cyanobacterial bloom extracts on survival and functions among species in eutrophic freshwaters.

Progress on the usage of the rotifer Brachionus plicatilis in marine ecotoxicology: A review

The rotifer, Brachionus plicatilis, is a widely used model species in marine ecotoxicology for evaluating pollutions, toxins, and harmful algae. In this paper, the marine ecotoxicology of Brachionus plicatilis was reviewed, including toxicity measurements of harmful algae species and environmental stresses. In addition, marine pollution involving pesticides, heavy metals, drugs, petroleum, and petrochemicals were addressed. Methods for measuring toxicity were also discussed. The standard acute lethal assay and the chronic population dynamics test were indicated as common methods of toxicity evaluating using B. plicatilis. Research on other biomarkers, such as behaviour, enzyme activity, or gene expression, are also reported here, with potential applications for fast detection or the scientific exploration of underlying molecular mechanisms. It is suggested that the methods selected should reflect the experimental purpose. Additionally, series assays should be conducted for comprehensive evaluation of ecotoxicity as well as to elucidate the correct mechanisms. Genetic methods, such as transcriptomics, were suggested as useful tools for exploring the toxicity mechanism using the rotifer B. plicatilis.