Integrating zooplankton biomarkers within the European Marine Strategy Framework Directive (MSFD) assessment

Biomarkers are increasingly recognized as sensitive indicators of physiological and ecological responses in marine organisms, offering new perspectives for monitoring and ecosystem status assessment. Traditional indices of species composition and biomass, though valuable, often fail to capture early sublethal or functional changes in zooplankton communities. To explore the potential of biomarkers as complementary tools for environmental monitoring within the European Marine Strategy Framework Directive (MSFD), the EuroMarine workshop BIOZOO gathered European experts to evaluate the use of enzyme activities, oxidative stress markers, fatty acids, and stable isotopes for zooplankton-based assessments. Participants identified methodological priorities, including protocol standardization, inter-laboratory calibration, and baseline development, to ensure comparability across regions. This synthesis highlights how integrating biochemical and physiological biomarkers into existing monitoring frameworks can improve the detection of ecosystem responses to environmental pressures such as warming, pollution, and eutrophication. Strengthening biomarker applications in European Seas represents a step toward a more functional, harmonized, and responsive approach to pelagic habitats assessment.