Over the past 50 years, Mediterranean marine ecosystems are facing more threats than ever before, associated with human activity, climate change, and pollution. Among these environmental issues, pollution by inorganic contaminants such as nutrients and trace elements has devastating effects on coastal marine ecosystems by causing algal blooms and contaminating sediment and marine food web. These inorganic pollutants enter the Mediterranean Sea through sewage discharge and agriculture runoff and affect Posidonia oceanica seagrass growth and distribution. In order to overcome the negative impacts of these contaminants on marine life, P. oceanica fiber was recently proposed as a low-cost adsorbent material for the removal of inorganic pollutants from wastewater before discharge into the Mediterranean Sea. Such a promising strategy could reduce the concentration of pollutants entering the sea while ensuring the better management of huge quantities of Posidonia fibers depositing onto Mediterranean beaches. During the last decade, natural and modified Posidonia fibers were tested for their capacities to remove inorganic contaminants from both synthetic and real wastewater. Studies on Posidonia fibers’ adsorption capabilities have primarily focused on testing with synthetic solutions, where researchers have carefully examined key parameters such as pH, contact time, pollutant concentration, and the amount of adsorbent material used. However, research investigating how these fibers perform in removing inorganic pollutants from actual wastewater remains limited. In addition, further investigations should be performed under dynamic conditions using fixed bed columns to determine the economic viability and the effectiveness of this treatment approach at a larger scale.