A population of the green sulfur bacterium Pelodictyon clathratiforme was monitored during the stratification period of Coromina Lake, a freshwater, holomictic pond of the Banyoles lacustrine area (Girona, NE Spain). The chromatographic analysis of this population revealed the presence of a wide variety of both bacteriochlorophyll (BChl) d and BChl c homologues. Isolation of chlorosomes from cultured Pelodictyon cells and their further analysis by steady-state fluorescence indicated that, although both pigment were present in chlorosomes, only BChl c gave rise to an emission signal, suggesting a fast energy transfer from BChl d to BChl c. Likewise, chlorosomes isolated from natural samples were significantly larger (60–70 nm in width and 115–120 nm in length) than those isolated from cells grown in laboratory under optimal light conditions (48±6.8 nm and 100±15.8 nm in width and length, respectively). The potential role of heterogeneous BChl c- and BChl d-containing chlorosomes and the differences in chlorosome size measured are discussed in terms of the severe light limitation (available light intensity <0.1 μmol photons m−2 s−1 at the bacterial plate) under which the population subsisted during the study period.