Background: We had previously reported high androgenic and estrogenic activities in seawaters in
confined clusters close to Singapore. Further investigations revealed a hitherto unsuspected link between
estrogenic/androgenic activity and net phytoplankton count.
Objective: The primary objective of this study was to investigate the cause of a correlation between net
phytoplankton and endocrine activity, and corroborate this observation, and rule out other possible
confounding factors. Our secondary objective was to study if these estrogenic secretions can impact
human health.
Methods: Five species of phytoplankton, Gymnodinium catenatum, Prorocentrum minimum, Alexandrium
leei, Chattonella marina, and Fibrocapsa japonica, were isolated from Singapore waters and mass cultured
and the cells and culture media screened for estrogenic and androgenic activity using human cell-based
bioassays.
Results: The raphidophytes C. marina and F. japonica displayed significant estrogenic activity whilst the
dinoflagellates G. catenatum and P. minimum displayed significant androgenic activity in both the cell
extracts and the cell culture media extract.
Conclusions: Our data shows that selected phytoplankton isolates are potent secretors of estrogenic and
androgenic substances, which are potential endocrine disrupting chemicals (EDCs). As the harmful
nature of EDCs is largely due to their bioaccumulation in the aquatic food chain our findings imply that
the impact of these phytoplankton secretions needs to be investigated especially for seafoods, which are
only a single trophic level away from phytoplankton. Alternatively, should these phytoplankton-origin
EDCs not accumulate through marine food chains to significantly impact humans or marine mammals,
our results indicate that functional assays could greatly over-estimate the risk from naturally occurring
EDCs produced by marine phytoplankton. It remains to be determined if these EDCs affect zooplankton
and other organisms that directly feed on marine phytoplankton, or if the secreted EDCs can directly
impact other marine fauna.