Modelling the components of the vertical attenuation of ultraviolet radiation in a wetland lake ecosystem

The extinction of solar UV (290-400 nm) radiation in aquatic ecosystems is a complex phenomena. In this paper, we examine and model the attenuation of UV radiation in a shallow lake ecosystem. In particular we focus our analysis on the specific role of the fractions of dissolved and particulate matter in the water column in the attenuation of radiation. This analysis is aimed by representing the spatial distribution of each fraction making it possible to evidence the spatial variation in habitat quality. In situ and laboratory measurement are used to elaborate a UV attenuation model. The attenuation model distinguishes between the contribution of particulate and dissolved matter in the attenuation of the solar UV flux. In the studied wetland lake (Laguna Iberá, sub-tropical latitude, Argentina) the importance of dissolved matter is dominated in the UVB solar spectrum (290-320 nm) but the effects of the particulate fraction are not negligible, in particular in UVA (320-400 nm). The spatial representation of model results demonstrate the non homogeneous nature between attenuation of the two fractions. Local and global environmental change can have important impacts on dissolved and particulate matter concentrations, which cam have ecological consequences in relation to the high flux of incoming UV radiation. The model developed to examine the relative attenuation of the dissolved and particulate fractions and is a useful instrument to identify the role that these fractions have on the optical characteristics of aquatic ecosystems.