Carbon and nitrogen isotopic compositions of three types of chloropigments from Lake Kaiike, Japan. Carbon (a) and nitrogen (b) isotopic compositions of chloropigments (i.e., chlorophyll a, bacteriochlorophyll a, and bacteriochlorophylls e) from the water column of meromictic Lake Kaiike, Japan. The water column of the lake is strongly stratified with a chemocline at a depth of around 5 m. Below the chemocline, oxygen is depleted but hydrogen sulfide is abundant. The isotopic compositions of bacteriochlorophylls e are the mean values for those of bacteriochlorophylls e
2, and e
3. Redrawn from Ohkouchi et al. (2005).