The increasing deployment of offshore infrastructure has raised concerns about the environmental impact of corrosion protection systems, particularly galvanic anodes, which release trace metals such as zinc and aluminium into the marine environment. Traditional monitoring methods often fail to capture the bioavailable fraction of these contaminants or provide adequate temporal resolution. Here, we investigate the brown macroalga Saccharina latissima as a bioindicator of metal emissions from galvanic anodes. Laboratory and mesocosm experiments demonstrated linear relationships between environmental concentrations and metal accumulation, particularly for zinc. Compared to grab and passive sampling, S. latissima provided more consistent and representative exposure estimates. These findings highlight the potential of S. latissima as a cost-effective and reliable bioindicator for offshore trace metal contamination monitoring and its integration into environmental assessment frameworks.