Metal ecotoxicity in sea anemones: Accumulation, effects, and knowledge gaps

Metals are a major class of legacy pollutants that end up in marine ecosystems, posing a significant threat to marine biota, including sea anemones. The current review critically synthesises studies published over the last 50 years on the uptake, tissue distribution, and biological effects of 20 metals across 18 sea anemone species in both field and laboratory settings, including interactions with climate change stressors (salinity and pH). Field studies have focused on bioaccumulation and report the high capacity of sea anemones to accumulate metals, mainly iron and barium, primarily in the pedal disk. Laboratory exposure studies reveal a dose- and time-dependent accumulation and highlight that symbionts take up and store essential metals (Cu, Fe, and Mn) due to their key biological roles. Available data point to Exaiptasia pallida as a promising model for metal ecotoxicology. Across studies, metals elicit alterations at molecular to behavioural/morphological levels, including transcriptome reprogramming, oxidative stress, and detoxification failures, as well as genotoxicity, cellular injury, immune dysfunction, metabolic and morphological disruption, reproductive impairment, and bleaching, which are generally amplified by climate change stressors. Ultimately, this review identifies key knowledge gaps and outlines future research directions on metal ecotoxicity in sea anemones. Collectively, these insights position sea anemones as informative sentinels of metal contamination in marine ecosystems.