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These images were created by combining the mean euphotic depth estimates to produce seasonal representations for winter, spring, summer and fall. Winter includes the months of January, February and March; spring includes the months of April, May and June; summer includes the months of July, August and September; fall includes the months of October, November and December. Euphotic depth estimates were originally obtained from the Naval Research Laboratory at the Stennis Space Center (NRL/SSC). NRL/SSC processed MODIS-Aqua satellite imagery covering the Gulf of Mexico, for a 5-year time period from January 2005 through December 2009. The Gulf of Mexico was divided into three regions, western, central and eastern. For purposes of this image, the three regions were joined in ArcMAP 10. To calculate euphotic depth (Zeu) from the satellite imagery, NRL first estimated the absorption and backscattering coefficients of the water from the satellite remote sensing reflectance (Rrs) values (Lee et al. 2002), and then used those coefficients to estimate Zeu and make image products. The diffuse attenuation coefficient was calculated two ways: at 490 nm using the NASA empirical KD2 algorithm and at 488 nm using the semi-analytical algorithm of Lee et al. (2005a). The Lee et al. (2005a) algorithm is accurate to about 15%, compared to in situ measurements (Lee et al. 2005b).