Sea-land interaction along the Catalan coast (NW Mediterranean): Assessment of Submarine Groundwater Discharge (SGD) based on seawater nutrient concentrations 

Abstract

Submarine Groundwater Discharge (SGD) has garnered attention in the assessment of sea-land interactions within coastal regions. SGD plays a crucial yet uncertain role in coastal ecosystems, involving the release of nutrient-enriched groundwater and recirculation seawater in the geological matrix into the sea. Its significance is particularly relevant in the oligotrophic Mediterranean Sea, characterized by low nutrient concentrations, making SGD a pivotal process in sustaining life within the sea-land transition zone. This study explores the impact of SGD along the 580 km of the Catalan coast (Western Mediterranean) an area densely populated where land-sea interactions and the effects of SGD on marine ecosystems may be substantial. Leveraging a 23-year dataset, the study seeks to establish connections between SGD and the quality of the coastal area. The primary focus lies in investigate SGD locations through the analysis of salinity and inorganic nutrient composition (NO3, NO2, NH4, PO4, and SiO4) at 70 coastal stations. A novel perspective, Compositional Data Analysis (CoDa), is employed for this purpose. The study also integrates land-based hydrogeological factors, such as the geological nature of the aquifer. Furthermore, it explores the correlations between nutrient composition and biological indicators, specifically chlorophyll in the coastal area, utilizing CoDa techniques. Chlorophyll, as an indicator of photosynthetic activity, serves as a marker for biological responses to nutrient changes induced by SGD. This innovative approach, centered on the compositional nature of the data, streamlines the identification SGD locations and enables a comprehensive assessment of its ecological impact. The outcomes of this study have the potential to provide valuable insights for the improvement of coastal ecosystem management. Acknowledgments This work was funded by the Spanish Government grant no. PID2022-140862OB-C21/C22 and PID2021-125380OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe