Volatile organic compounds in aquatic ecosystems - Detection, origin, significance and applications

Volatile organic compounds (VOCs) include a broad range of compounds. Their production influences a large number of processes, having direct and secondary effects on different fields, such as climate change, economy and ecology. Although our planet is primarily covered with water (~70% of the globe surface), the information on aquatic VOCs, compared to the data available for the terrestrial environments, is still limited. Regardless of the difficulty in collecting and analysing data, because of their extreme complexity, diversification and important spatial-temporal emission variation, it was demonstrated that aquatic organisms are able to produce a variety of bioactive compounds. This production happens in response to abiotic and biotic stresses, evidencing the fundamental role of these metabolites, both in terms of composition and amount, in providing important ecological information and possible non-invasive tools to monitor different biological systems. The study of these compounds is an important and productive task with possible and interesting impacts in future practical applications in different fields. This review aims to summarize the knowledge on the aquatic VOCs, the recent advances in understanding their diverse roles and ecological impacts, the generally used methodology for their sampling and analysis, and their enormous potential as non-invasive, non-destructive and financeable affordable real-time biomonitoring tool, both in natural habitats and in controlled industrial situations. Finally, the possible future technical applications, highlighting their economic and social potential, such as the possibility to use VOCs as valuable alternative source of chemicals and as biocontrol and bioregulation agents, are emphasized.