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Marine communities provide a variety of ecosystem services. The assessment of nutrients is key in order to evaluate its ecological status. We focus our attention on the Mediterranean Sea. It is considered an oligotrophic sea with very low nutrient concentrations and therefore it is important to consider the inputs from land-based water discharges in coastal areas as they may change the nutrient concentrations and composition. The contributions from rivers and marine outfalls have been extensively studied in the literature, but the effects of Submarine Groundwater Discharges (SGD) on marine ecosystems remain uncertain.

This work explores the impact of SGD along the Catalan coast (Western Mediterranean). This is a densely populated  area where land-sea interactions and the effects of SGD on marine ecosystems may be substantial. The goal of the study is to establish connections between SGD and the quality of the coastal area through the study of a  23-year dataset. The primary focus lies on the investigation of SGD locations through the analysis of inorganic nutrient composition (NO3, NO2, NH4, PO4, and SiO4) and salinity  at 70 coastal stations from a Compositional Data Analysis (CoDA) perspective. Other land-based hydrogeological factors, such as the geological nature of the aquifer are also considered.  The relationship between nutrient composition and biological indicators using CoDA techniques is also explored. For instance,  chlorophyll  as an indicator of photosynthetic activity, may serve as a marker for biological responses to nutrient changes induced by SGD.

The present approach takes into account the compositional nature of the data, helps the identification of SGD locations and enables the assessment of its ecological impacts. The results of this study have the potential to provide insights that are valuable for the improvement of coastal ecosystem management.

marine ecosystem, inorganic nutrient composition, balances, clr-biplot, log-ratio approach