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.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors

Studying photosynthesis under Far-Red light and simulated M-dwarf star light: new experimental tools and suitable eukaryotic organisms with different positions in the tree of life

Several recently discovered Earth-like exoplanets are orbiting the Habitable Zone of M-dwarf stars. These are the most abundant and long-lived stars known in the Milky Way, making them ideal to potentially harbour life. However, such stars have different spectral characteristics respect to the Sun. They are less luminous and generate a light spectrum with far-red and infrared as major components, while emitting at very low level in the visible. These characteristics do not seem suitable for most oxygenic photosynthetic organisms we know from Earth, that evolved to absorb only visible light. Many researchers discussed the possibility of oxygenic photosynthesis in these worlds so far, but no experimental research has been done testing organisms under simulated M-dwarf spectra. At the university of Padova, a collaboration between the Department of Biology, the Astronomical Observatory (INAF) and the Institute of Photonics and Nanotechnology (IFN-CNR) led to the construction and the development of a new experimental tool. The setup is composed by three main parts: 1) a Star Light Simulator, able to generate different light intensities and spectra, including those of nonsolar stars; 2) an Atmosphere Simulator Chamber where cultures of photosynthetic microorganisms can be exposed to different gas compositions; 3) a reflectivity detection system to measure from remote the Normalized Difference Vegetation Indexes (NDVI). Such a setup allows us to monitor photosynthetic microorganism\u2019s growth and gas exchange performances under selected conditions of light quality and intensity, temperature, and atmospheres simulating non-terrestrial environments. All parameters are detected by remote sensing techniques, thus without interfering with the experiments and altering the environmental conditions set. We initially focused on cyanobacteria as target microorganisms, due to their extraordinary capacities to withstand every kind of environment on the Earth as well as their ability to acclimate to Far-Red light. We are now selecting suitable eukaryotic photosynthetic organisms by testing at first their ability to acclimate to Far-Red light. The possibility of photosynthesis for prokaryotic and eukaryotic photosynthetic organisms under M-dwarfs light will be discussed

Is Far-Red Light Photoacclimation (FaRLiP) activated in cyanobacteria exposed to M-dwarf starlight simulated spectra?

Rocky terrestrial exoplanets in the Habitable Zone of M-dwarf stars are ideal to potentially harbour life. However, such stars have different spectral characteristics respect to stars like our Sun, with almost no visible light available and major components in the far-red and infrared. This doesn\u2019t seem suitable for oxygenic photosynthetic organisms, that evolved on Earth to absorb only VIS light. Thanks to the newly developed Star Light Simulator, an instrument able to simulate the emission spectra of different kinds of stars (Sun and M-dwarfs included), we were able to perform growth and photosynthetic analyses on a few species of cyanobacteria irradiated with M-dwarf simulated lights. We selected two strains of cyanobacteria, Chlorogloeopsis fritschii PCC6912 and Synechocystis sp. PCC6803. The first can perform the so-called Far-Red Light Photoacclimation (FaRLiP), that allows it to survive and evolve oxygen in environments rich in far-red lights, thanks to the production of peculiar chlorophylls (chl d and f) and far-red absorbing forms of phycobiliproteins. This makes it a perfect candidate to test the possibility of oxygenic photosynthesis in exoplanets irradiated by M-dwarf spectra. The second cyanobacterium is a model organism for photosynthetic research and was used as a control unable to perform such acclimation. We compared the growth and photosynthetic performances of the cyanobacteria exposed to the M-dwarf simulated light spectra. The results were compared with those obtained from the cyanobacteria exposed to a solar simulated light and a far-red light (730 nm LED). The possibility of oxygenic photosynthesis in exoplanets orbiting the habitable zone of M-dwarfs as well as the activation of the FaRLiP response under these simulated spectra is discussed