Effects of Current and Future Summer Marine Heat Waves on Posidonia oceanica: Plant Origin Matters?

Marine heat waves (MHWs), prolonged discrete anomalously warm water events, have been increasing significantly in duration, intensity and frequency all over the world, associated with a variety of impacts including alteration ecosystem structure function. This study assessed effects current future MHWs on Mediterranean seagrass Posidonia oceanica performance, also testing importance thermal environment where plant lives. The were studied through mensurative experiment cold site (West North-West Sardinia, Italy, respectively). Future tested manipulative using P. shoots collected from sites transplanted common garden front power (North-West Sardinia): here plants exposed to longer duration stronger than natural last 20 years, resembling scenario. Morphological (total # leaves, maximum leaf length, percentage total necrotic length per shoot) biochemical variables (leaf proteins, carbohydrates, lipids) considered. Plants had similar sublethal responses both experiments for most variables, revealing that effect types, but different magnitude depending waves: general, number lipid content decreased, while necrosis carbohydrates increased. However, origin affected results, corroborating hypothesis context live affects their tolerance heat. Overall, this provided evidence about variations, such as carbohydrate levels, potentially good indicators stress.