Submarine groundwater discharge feedbacks on ecosystem services

Abstract

Humans have a notable ability to modify their surrounding environment for their own benefit. Nonetheless, some anthropogenic changes have led to global-scale consequences, causing the degradation of Earth's ecosystems. To analyze these human-nature interactions, the Ecosystem Services framework poses four categories of services referred to the benefits to society of using and modifying ecosystems toward their well-being (i.e., Supporting, Provisioning, Regulating and Cultural). Coastal areas are a crucial source of ecosystem services for humans, being both productive and sensitive. Coastal ecosystems, renowned for their diversity and productivity, depend on hydrological land-ocean connectivity regulated by processes such as rivers, streams, and Submarine Groundwater Discharge (SGD). Among them, SGD is recognized as a fundamental hydrological process that supports many coastal biogeochemical cycles and social-ecological systems. However, very little has been investigated about how SGD affects society and human well-being. To bridge this gap of knowledge, this thesis aims to advance the understanding of the social dimension of Submarine Groundwater Discharge, contributing to address the existing disconnection between the natural and social sciences in this field. To this aim, this thesis assesses both the impacts of highly polluting anthropogenic activities on SGD and the societal implications of this process by developing and applying the Ecosystem Services framework (a socio- ecological system approach) to SGD research. The results of this thesis demonstrate how polluting anthropogenic activities can induce large fluxes of dissolved metals and nutrients into the coastal ocean, having a significant impact on coastal marine ecosystems. In addition, the diversity of pathways of SGD play a relevant role on controlling the solutes fluxes supplied into the coastal ocean. The findings of this thesis also show that the high pressure exerted on coastal areas by tourism activities can lead to alterations in SGD fluxes, thereby endangering coastal ecosystems and the services they provide. To advance the understanding of the social implications of SGD, this thesis develops the first framework for identifying and classifying the Ecosystem Services provided by SGD and their effects on the well-being of local societies. Results show that SGD, from its use as a water resource to its cultural influence, is deeply rooted in many coastal societies at a global scale, and SGD-dependent ecosystems have a significant impact on the local communities. Additionally, results from the local perceptions of two Mediterranean societies (Mallorca and Salento) towards SGD, including its uses and its role in coastal communities, highlight the necessity of integrating data from the scientific literature, together with the information available in the grey literature and local knowledge for a complete understanding of the cultural dimension of SGD. Findings also show that the limited historical documentation on SGD causes bias in reporting present ecosystem services compared to the past in the two studied areas. The interdisciplinary approach followed in this thesis represents a novelty and brings new knowledge and evidence to guide policy and management strategies regarding SGD. In sum, this thesis is a walkthrough of the strong bounds between SGD and coastal societies' wellbeing, which provides both solid scientific evidence and robust methodological guidance on the influence of SGD on coastal societies from a social-ecological approach.