@ElectronicSource{CostaTelmNovo::SpLiAt,
             abstract = "Amazonian waters are commonly classified coarsely as white, black, 
                         and clear, reflecting their differing composition of particulate 
                         and dissolved compounds. Accordingly, the water light field and 
                         the ecology of each of these water types also differ strongly. 
                         Recent changes in land use are causing changes in river water 
                         composition that cause shifts in the water light field. 
                         Consequently, the quality and distribution of ecological habitats 
                         must also be changing. We investigate and quantify changes in the 
                         light field by reporting the first in situ spectral diffuse 
                         attenuation and scalar irradiance measurements and accompanying 
                         water optical constituents, including pigments determined by HPLC, 
                         from a suite of large white, black, and clear rivers of the Amazon 
                         Basin. Using this dataset, we evaluate the potential shifts in the 
                         water light field of waters affected by thousands of small-scale 
                         gold miners. Sampling was done during the high-water period along 
                         a 500 km transect of the Amazon River and six of its larger 
                         tributaries. Water samples were collected from the subsurface and 
                         analyzed for chlorophyll a and other pigments, total suspended 
                         solids, and colored dissolved organic matter. At each station, 
                         vertical profiles of temperature, spectral downwelling irradiance 
                         and upwelling radiance were taken from the surface down to the 
                         depth of 1% light penetration (Zeu). Our results show that, for 
                         the different types of waters, the diffuse attenuation coefficient 
                         has different spectral and penetration depth behavior due to 
                         varying proportions of dissolved and particulate compounds. In 
                         white and black waters, the photosynthetic active radiation 
                         becomes spectrally dominated by red light as a result of the high 
                         attenuation by suspended sediments and colored dissolved organic 
                         matter, respectively. Blue radiation is non-existent below the 0.5 
                         depth. This is not the case for clear waters, which exhibit a 
                         mid-spectra green light peak within the deep Zeu, and blue light 
                         in only attenuated by 2.5 m. Applying these results to clear 
                         waters that have been muddied by the injection of sediment from 
                         mining, we show that significant changes in the distribution of 
                         spectral scalar irradiance must occur, and that this would result 
                         in a decrease (i) in photosynthetic activity, (ii) in the 
                         production of organic matter photoproducts, (iii) in the size of 
                         clear water habitats, and shifts in biological communities. .",
              address = "S{\~a}o Jos{\'e} dos Campos",
          affiliation = "University of Victoria, Department of Geography, Canada and 
                         University of Victoria, School of Earth and Ocean Sciences, 
                         Victoria, Canada and {Instituto Nacional de Pesquisas Espaciais 
                         (INPE)}",
               author = "Costa, Maycira P. F. and Telmer, Kevin and Novo, E. M. L. M.",
             keywords = "water types, attenuation coefficient, scallar irradiance.",
             language = "en",
       lastupdatedate = "2006-12-13",
            publisher = "Instituto and Nacional and de and Pesquisas and Espaciais",
                  ibi = "sid.inpe.br/ePrint@80/2006/12.12.17.56",
                  url = "http://urlib.net/ibi/sid.inpe.br/ePrint@80/2006/12.12.17.56",
           targetfile = "v1.pdf",
                title = "Spectral light attenuation in Amazonian waters",
         typeofmedium = "On-line",
        urlaccessdate = "20 maio 2024"
}