|PhotoDOM - Impact of solar radiation on dissolved organic matter photochemical and microbial processes in the estuarine environment|
Programme - PTDC/MAR-EST/2314/2012
Execution dates - 2013-05-01 - 2016-04-30 (36 Months)
Funding Entity - FCT
Funding for CESAM - 160.512 €
Total Funding - 160.512 €
Proponent Institution - Universidade de Aveiro
Photochemical and microbial processes act in concert on carbon recycle and transformation in aquatic ecosystems. Solar radiation induces several DOM chemical reactions resulting in lost of color (photobleaching) and their oxidation. The loss of colour leads to an increase of water column UV penetration with consequent harmful effects to the biological component. Several reactive species are produced and involved in these reactions, which amplify the degradation of organic molecules and inhibition of bacterial activity. However, these processes also lead to the release of nutrients and to the formation of biological labile compounds, which increase microbial activity and intensify carbon and energy transformation to trophic webs and ecosystems productivity. The major aim of this project is to evaluate the impact of solar radiation on carbon cycle in the estuarine environment. Therefore, the interactions between solar radiation, dissolved organic matter (DOM) and bacterioplankton will be investigated in the natural environment and simulated experimentally. In order to identify the factors that influence solar radiation penetration in water and the seasonal and spatial profiles of variation of bacterioplankton abundance, diversity and activity, field studies will be conducted in two different zones with distinct characteristics in the estuarine system Ria de Aveiro during one year. Additionally, laboratory experimental assays will be performed to elucidate the mechanisms involved in DOM photochemical reactions, the responses of bacterioplankton to DOM photochemical transformations and direct UV radiation exposure, and the role of different reactive species on DOM photoreactions and their impact on bacterial activity. The contributions of the different wavelength ranges (UV-B, UV-A and PAR) to DOM photochemical transformations will be also evaluate during the experimental procedures. Changes in the composition of the bulk DOM induced by photoreactions will be determined by UV/visible absorbance and excitation emission matrix fluorescence spectroscopy (EEMS).