Submarine Groundwater Discharge (SGD) has emerged as a critical factor in understanding sea-land interactions in coastal regions. SGD involves the release of nutrient-rich groundwater and recirculated seawater into marine environments, playing a vital but poorly understood role in coastal ecosystems. This process is especially significant in the oligotrophic Mediterranean Sea, where low nutrient levels make SGD a key driver of ecological dynamics in the sea-land transition zone. This study investigates the impact of SGD along the Catalan coast in the Western Mediterranean, a densely populated area where land-sea interactions and SGD effects on marine ecosystems are likely substantial. Using a 23-year dataset, the research aims to link SGD to coastal water quality by analyzing inorganic nutrient composition (NO3, NO2, NH4, PO4, and SiO4) and salinity at 70 coastal stations. A Compositional Data Analysis (CoDA) approach is employed to identify SGD locations and assess their influence. The study also considers land-based hydrogeological factors, such as aquifer characteristics, and explores relationships between nutrient composition and biological indicators, particularly chlorophyll levels, which reflect photosynthetic activity and potential ecological responses to SGD-driven nutrient changes. This approach, which takes into account the compositional structure of the data, enhances the identification of SGD locations and facilitates a deeper understanding of their ecological impacts. The findings from this study offer valuable insights that could support the design of more effective strategies for the management and conservation of coastal ecosystems. Acknowledgments This work was funded by the Spanish Government grant PID2022-140862OB-C21 and PID2021-125380OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe. This study was also funded by of the Horizon Europe GES4SEAS project HORIZON-CL6-2021-BIODIV-01-04