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Rotifers are natural initial bait for fish larvae in freshwater. Here, the effects of various concentrations of acidified eggshell powder solutions (0, 20, 40, 80, 160, and 320 mg/L) on the growth and reproduction of the rotifer Brachionus calyciflorus were evaluated in culture experiments (11 days). The population density, catalase (CAT) and superoxide dismutase (SOD) activity, and Na and Mg contents in rotifers were significantly higher in the 20–160 mg/L groups than in the control group. A redundancy analysis showed that the Na, Mg, Cr, K, and Ca contents were positively correlated with the rotifer population density and CAT and SOD activity. Furthermore, the generation time and lifespan of F2 rotifers were significantly higher in the 20–40 mg/L treatment groups (82.0 ± 3.7 hr and 162.0 ± 2.7 hr, respectively) than in the control group (64.0 ± 4.0 hr and 128.0 ± 4.0 hr, respectively). Average egg production in F2 rotifers was significantly higher in the 20–80 mg/L treatment groups (15.2 ± 0.7 individuals) than in the control group (11.7 ± 1.2 individuals). These results indicate that 20 mg/L eggshell powder is optimal for growth and reproduction in B. calyciflorus, providing a theoretical basis for using new mineral sources in high-quality open bait for fish larvae.

Global climate changes are affecting organisms and their interactions in terrestrial and aquatic ecosystems, such as the increase in temperature and CO2 concentration. Herbivory interaction is a very important part of nutrient cycle and energy flow in freshwater ecosystem, and climate changes may directly or indirectly affect aquatic plants, aquatic herbivores and their interactions. In this study, we explored the effects of the rising temperature, elevated CO2 concentrations and herbivory by an herbivorous snail (Radix auricularia L.) on a submerged plant (Vallisneria natans L.). Our results showed that herbivory, temperature, and CO2 had specific effects on snail and plant growth, statistically there was only one interaction-a reduction in leaf number. Under different experimental conditions, snail herbivory always has negative effects on biomass accumulation and growth of V. natans. Moreover, the increases in temperature also inhibited its growth. Snail herbivory reduced the content of total carbon and total nitrogen of V. natans in all treatments, while the total phenols content increased. Our findings indicate that the rising temperature, elevated CO2 concentrations and herbivory have interactive effects on the growth and stoichiometry of submerged macrophytes, but further research is needed between aquatic plants and aquatic herbivores to aid prediction the impact of climate change on freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Aquatic plants and associated herbivores are expected to perform better under the rising atmospheric CO2 concentration brought about by climate change. However, it is not clear how increasing CO2 affects herbivory on aquatic macrophytes. In this research, we set four treatments (A group: ambient air without snails; AS group: ambient air with snails; E group: elevated CO2 without snails; and ES group: elevated CO2 with snails) and studied the effects of low (0-0.5 mg/L) and high (4-8 mg/L) CO2 concentration on the growth, morphology, and chemical traits of the macrophyte Vallisneria spiralis (Angiosperms: Hydrocharitaceae) and the snail Radix auricularia (Pulmonata: Lymnaeidae), and the relationships between them in the laboratory. We found that herbivory decreased the total biomass of V. spiralis by 28.6% and 25.3% under low and high CO2 conditions, respectively. Compared with A group, ES group reduced the total plant biomass by 43.3%. Elevated CO2 and herbivory both affected the growth of V. spiralis and change its resource allocation patterns. Total nitrogen content in V. spiralis leaves decreased under herbivory condition, and total phenols increased under the interactions condition between elevated CO2 and herbivory. However, total C content of R. auricularia increased under elevated CO2 condition. These results could provide valuable insights into how climate change affects plant-herbivore interactions and food web structure in shallow inland waters. [ABSTRACT FROM AUTHOR]