Cu2+

Scenedesmus obliquus

bioaccumulation

Brachionus calyciflorus

life table demography

Pollution

Heavy metals contamination of water

Metals toxicity

The algae- rotifer food chain plays a pivotal role in freshwater dynamics, as well as assessing toxicity in aquatic environments. We investigated the changes in algal cell density, photosynthetic pigments, superoxide dismutase (SOD) activity, and Cu²⁺ bioaccumulation after exposing Scenedesmus obliquus to 3.75, 7.5, 15, 30, and 60 μg/L Cu²⁺ for 72 h. We also studied the effects of Cu²⁺-exposed algae on the life table demographic parameters of Brachionus calyciflorus after 48 and 96 h of feeding. The results found that, when compared with the control, 3.75 μg/L Cu²⁺ significantly increased algal cell density after 48 h, while 60 μg/L Cu²⁺ significantly reduced algal cell density after 24 h. Increases in exposure time resulted in the chlorophyll-a, chlorophyll-b, and carotenoids showing an initial decrease and then increasing trend when compared to the control. Low concentrations of Cu²⁺ tended to induce increased SOD activity in algal cells, while high concentrations inhibited SOD activity. With increasing Cu²⁺ concentration and time, the Cu²⁺ bioaccumulation in algal cells increased proportionally. The highest bioaccumulation value was 1205 μg/g in 60 μg/L Cu²⁺ treatment after 72 h of exposure, 376.28% higher than pre-exposure level. Algae in the 3.75 μg/L Cu²⁺ treatment group significantly inhibited the population growth of B. calyciflorus, algae in the 60 μg/ Cu²⁺ group had the strongest inhibitory effect on the population growth of rotifers, and algae in the 30 μg/L Cu²⁺ group significantly increased the offspring mictic rate. The rotifer population produced adaptive responses to Cu²⁺-exposed algae stress after 96 h of feeding, unlike after 48 h.