Oxidative Stress as a Biomarker of Pollution in Marine Bivalves

Oxidative stress arises when there is an imbalance between reactive oxygen species (ROS) production and the capacity of antioxidant defence to neutralize them. While ROS are critical for aerobic life, their excessive accumulation in the tissues of organisms may damages lipids, proteins, and DNA, compromising cellular and physiological functions. The evaluation of oxidative stress relies on a range of molecular biomarkers indicating ROS-driven oxidation in tissues or whole-body specimens. Marine ecosystems are particularly vulnerable to oxidative imbalance, as both environmental factors such as temperature and oxygen availability, together with chemical pollutants like heavy metals, nanoparticles and oil, can enhance ROS generation or weaken antioxidant defences. Among aquatic organisms, marine bivalves are popular sentinel species for monitoring environmental contamination, due to their filter-feeding lifestyle that highly exposes them to pollutants and makes them valuable models for biomonitoring. Target organs, for example, gills and digestive glands are especially affected, acting both as sites of contaminant accumulation and as responsive tissues where oxidative stress can be quantified. Generally, the oxidative stress biomarkers in bivalve species indicate useful information on the toxicity of contaminants along with the quality of the environment. To gain an inclusive perspective on pollutant effects on marine habitats, the application of several biomarkers becomes unavoidable.