Uptake and Effects of Yttrium on the Seaweed Ulva sp.: A Study on the Potential Risks of Rare Earth Elements in Aquatic Environments

Abstract

Technological proliferation relies on critical elements such as rare earth elements (REEs) and raises environmental problems associated with raw material extraction, industrial manufacturing, and the informal management of the growing e-waste. Algae are good bioindicators of contamination and have shown promise as biosorbents for remediating metal-contaminated environments. However, the effects of REEs on algae are still poorly documented and understood. This study investigated the uptake of yttrium (Y)—one of the most frequently used REEs, particularly in fluorescent lamps—by Ulva sp., as well as its effects on total chlorophyll content, relative growth rate, and biochemical performance. The algae were exposed to Y for 72 h at environmentally relevant concentrations, including levels found in e-waste leachates (0.5, 5.0, 50, and 500 mg/L). Ulva sp. removed 86% of Y within 72 h, with a bioconcentration factor of up to 621. EDTA analysis revealed that over 90% of yttrium was retained on the algal surface. SEM-EDS mapping showed crystal structures on the algae where Y was present. While the relative growth rate was unaffected by the tested Y gradient, photosynthesis was significantly impaired at 500 mg/L. Despite the activation of defence mechanisms, cell damage was observed at most Y concentrations tested, highlighting the potential risks associated with the presence of REEs in aquatic environments.