To calibrate the hyperspectral imaging (HSI) index values from the sediments of Holzmaar (HZM19) to concentration, a spectrophotometrically measured pigment analysis (Butz et al., 2015; doi:10.1117/1.JRS.9.096031) was performed for 23 samples. These samples were selected to cover a wide range of pigment concentrations as documented by HSI scanning. Approximately 1 g of wet sediment was treated with 100 % acetone according to the method of Lami et al. (1994; doi:10.1007/BF00684032), and the extracts were measured with a Shimadzu UV-1800 spectrophotometer to obtain the mass concentration of Chl-a and Bphe-a in µg/g dry sediment using a mass extinction coefficient for Chl-a (Fiedor et al, 2002; doi:10.1562/0031-8655(2002)0760145POTBCS2.0.CO2) and for Bphe-a (Jeffrey and Humphrey, 1975; doi:10.1016/S0015-3796(17)30778-3).