Estimating the diffuse attenuation coefficient from moderatespatial resolution, multi-spectral satellite data in a seagrass environment

Currently, spatial light attenuation and water clarity can be estimated from diffuse attenuation coefficient at wavelength 490 nm (Kd₄₉₀) available from satellite data. In the present study, we investigated the performance of existing satellite Kd₄₉₀ algorithms in near-shore seagrass environment using available in situ data. We also examined the use of moderate-spatial resolution, multispectral imagery data of Landsat and ALOS AVNIR-2 to estimate both measured and calculated Kd₄₉₀. Finally, we demonstrated conceptually on how Kd₄₉₀ can be related to Kd of photosynthetically available radiation (K_dPAR). The results showed that existing Kd₄₉₀ algorithms can be used to estimate in situ Kd₄₉₀ for sites with Kd₄₉₀ <; 1 m^-1. Systematic and strong relationships were observed between blue-green ratio of Landsat and AVNIR 2 bands, and either in situ Kd₄₉₀ or calculated Kd₄₉₀ from MERIS/MODIS algorithms. For some selected sites K_dPAR can be well reconstructed from Kd₄₉₀ using empirical model from which correlation between Kd₄₉₀ and K_dPAR can then be developed.