Coastal pollution of aquatic systems

Anthropocene is the current era in which human activities modify various environmental properties, which have implications for many coastal processes. Anthropogenic stressors increasingly affect coasts and push these environments to a new altered equilibrium state. However, monitoring such pollution is a challenging task because coastal systems are highly dynamic and integrate the physicochemical forces at work on freshwater bodies, estuaries and lagoons with the oceanographic characteristics of adjacent seas. The current thesis addresses pollution of coastal environments in a broad way, with special attention to the current and historic problematic of estuarine contamination by metals. Firstly, it introduces the chemical (e.g. metals, persistent organic pollutants, and emerging contaminants), physical (e.g. microplastics, sediment loads, temperature), and biological (e.g. microbiological contamination, invasive species) pervasive anthropogenic influence in coastal areas. This introductory chapter is followed by a discussion on the limitations towards holistic environmental health assessments that are imposed by the scarcity of tools and multidisciplinary approaches. At that juncture, we perform a deep investigation of metal fate and its effects in estuaries. The review of the scientific literature in the third chapter provides a transdisciplinary conceptual framework for the estuarine behaviour of metals and its impacts on fauna and flora. This comprehensive overview and conceptual model are further accompanied by an elaboration on empirical models, as well as discussion of data on metal behaviour under laboratory and field conditions. While our review postulates that most studies had observed a non- conservative behaviour of metals in estuaries, our data suggests that at local scale such phenomenon is greatly explained by a high metal mobilisation driven by biogeochemical gradients. In fact, our results demonstrate that iron mobilisation regulates the pollution levels of iron and potentially other metals in an intertidal area under strong anthropogenic influence. In summary, estuarine physicochemical gradients, biogeochemical processes, and organism physiology are jointly coordinating the fate and potential effects of metals in estuaries, and both realistic model approaches and attempts to postulate site-specific water quality criteria or water/sediment standards must consider such interactions.