MAPPING OF PHOTOSYNTHETIC PIGMENTS IN SPANISH RESERVOIRS Ramón Peña-Martínez, José Antonio Domínguez-Gómez, Caridad de Hoyos, Antonio Ruiz-Verdú Centro de Estudios Hidrográficos del CEDEX, Pº Bajo de la Virgen del Puerto, 3 28005 Madrid (Spain). Email:
[email protected]
ABSTRACT We present the preliminary results of the first stage of the project AO-594, which comprises the development and calibration of algorithms for photosynthetic pigment mapping in Spanish reservoirs. In the years 2001-2002, an extensive field campaign was made in 36 reservoirs and lakes in order to obtain a database of Rrs spectra (400-1000 nm), photosynthetic pigments concentration and phytoplankton composition. The sampled water bodies cover a wide range of environmental conditions, trophic levels and phytoplankton communities. As a first approach in algorithm development, we have explored the relationships between ratios of MERIS bands and pigment concentrations through simple linear regression analysis. The bands have been selected based on the spectral properties of each pigment and a peak analysis of the Rrs spectra. For chlorophyll a, we have found a very good linear relationship (R2 =0.919) using the ratio between bands 9 and 7. Similar results are found using band 8 instead of 7. In any case, the model derived for the whole range of concentrations (0-500 mg m-3 ) fails for low values (
