Fig. 2. Principal components analysis (PCA) plot of various swine manure storage system fatty acid methyl ester (FAME) profiles during July 1998. Values in parentheses indicate the contribution of PC1 or PC2 to the total variation in the FAME profiles. Circles were drawn to facilitate elucidation of the patterns. Two-stage first phototrophic lagoon (TS1PL) (); two-stage second phototrophic lagoon (TS2PL) (); single-stage phototrophic lagoon (SSPL) (); earthen nonphototrophic basin (ENPB) (); concrete nonphototrophic basin (CNPB) ().