Determination and Occurrence of Retinoids in a Eutrophic Lake (Taihu Lake, China): Cyanobacteria Blooms Produce Teratogenic Retinal

Besides retinoic acids (RAs), some retinoids such as retinal (RAL) and retinol (ROH), which are considered as RA precursors in vertebrates, are also reported to be teratogenic agents. In this study we investigated four RA precursors including RAL, ROH, retinyl palmitate, and beta-carotene in the eutrophic Taihu Lake, China, by developing a sensitive analytical method. RAL and beta-carotene were widely detected in natural cyanobacteria blooms and lake water. Intracellular concentrations of RAL and beta-carotene in blooms were 9.4 to 6.9 x 10(3) and 3.4 to 1.8 x 10(5) ng L-1, respectively, and their concentrations in lake water were up to 1.4 x 10 ng L-1 (RAL) and 9.8 x 10(2) ng L-1 (beta-carotene). The good correlation between intracellular concentrations of RAL and RAs implied that PAL was involved in the production of RAs by cyanobacteria blooms. Further examination of 39 cyanobacteria and algae species revealed that most species could produce RAL and beta-carotene. The greatest amount of RAL was found in Chlamydomonas sp. (FACHB-715; 1.9 x 10(3) ng g(-1) dry weight). As the main cyanobacteria in Taihu Lake, many Microcystis species could produce high amounts of RAL and were thought to greatly contribute to the production of RAL measured in the blooms. Productions of RAL and beta-carotene by cyanobacteria were associated with species, origin location, and growth stage. The results in this study present the existence of a potential risk to aquatic animals living in a eutrophic environment from a high concentration of RAL in cyanobacteria blooms and also provide a clue for further investigating the mechanism underlying the biosynthetic pathway of RAs in cyanobacteria and algae.