Periphyton is a complex biological matrix that plays a key role in aquatic ecosystems, not only as the basis of the food web, but also as a potential bioindicator of pollution. In the context of monitoring emerging pollutants, the study of periphyton provides complementary information to that obtained from water and sediment, especially regarding bioaccumulation processes and associated ecological risks. Its ability to retain and accumulate contaminants over time makes it a valuable tool for assessing long-term exposure and environmental quality.

This study was carried out in the Douro River basin, in the region of Bragança (northeastern Portugal), where periphyton samples were collected from 14 sites during three seasonal campaigns throughout 2024. The samples were obtained by scraping hard substrates in river and reservoir systems, which were then preserved under cold conditions and freeze-dried for laboratory analysis. In addition to the development of a specific solid-phase extraction (SPE) and cleanup protocol for the detection of pharmaceutical compounds using high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS/MS), the periphyton samples were characterized to better understand their structure and composition as an environmental matrix.

Periphyton characterization revealed consistent patterns, with dry weight generally between ~4 and 90 g/m² and chlorophyll content ranging from ~0.02% to 5%. The assessment of pharmaceutical contamination is still in progress, as methodological improvements are being applied due to the lack of reliable results with existing approaches.

The methodological approach adopted will be presented, along with reflections on technical challenges and its potential contribution to integrated environmental assessment. Preliminary findings may also be included.