Caracterização espectral da água e da vegetação aquásubmersa no estuário da Lagoa dos Patos (RS, Brasil).

Abstract

Submerged aquatic vegetation (SAV) in Patos Lagoon estuary, composed by seagrasses and benthic macroalgae, shows a high temporal variability in its distribuition, abundance and composition, mainly related to fluvial discharge, sediment dynamics and water quality. However, most studies were punctual, and the techniques used are very limited in space. Remote sensing techniques have been recently applied for SAV monitoring and studying, in order to detect temporal changes and at same time providing a good resolution of spatial dynamics,allowing to evaluate the magnitude and persistence of the changes in abundande and structure. However, the success of such methodology depends on the comprehension of the spectral responses of the SAV and other water and sediment optical components. This study investigated the spectral responses of SAV in a Patos Lagoon shallow bay, by using radiometric techniques in situ. Although the high optical complexity of the estuarine region studied, the results allowed discriminating a vegetated shallow area from the adjacent deep waters. Under conditions of low turbity, and moderated to high biomass coverage, the present SAV community (mainly green macroalgae) was characterized by very low albedo, distinctive reflectance in 700nm, deep absorption in 660nm and high correlation with the green/blue reflectance ratio. The low sampling size did not allowed a good resolution of the spectral response of water parameters, particularly the chlorophyll. Further studies are focusing in obtain radiometric data under several hydrological and optical conditions, with a highly distribution in space.