title: Phytoplankton blooms: an overlooked marine source of natural endocrine disrupting chemicals.
abstract: 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.
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228; Tropical Marine Science Institute, National University of Singapore, S2S, 18 Kent Ridge Road, Singapore 119227.
authors.forename: Yinhan
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228.
authors.forename: Xiaochong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228.
authors.forename: Inthrani Raja
authors.initials: IR
authors.lastname: Indran
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228.
authors.forename: Shi-Jun
authors.initials: SJ
authors.lastname: Zhang
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228.
authors.forename: Zhengbing
authors.initials: Z
authors.lastname: Lv
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Tropical Marine Science Institute, National University of Singapore, S2S, 18 Kent Ridge Road, Singapore 119227.
authors.forename: Michael
authors.initials: M
authors.lastname: Holmes
authors.affiliation: School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.
authors.forename: Ying Zhong
authors.initials: YZ
authors.lastname: Tang
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228. Electronic address: obgyel@nus.edu.sg.
authors.forename: E L
authors.initials: EL
authors.lastname: Yong
mesh_terms: D000728:Androgens / Q000032:analysis; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004141:Dinoflagellida / Q000737:chemistry*; D052244:Endocrine Disruptors / Q000032:analysis*; D047628:Estrogen Receptor alpha / Q000819:agonists; D006801:Humans; D061986:MCF-7 Cells; D010839:Phytoplankton / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry / Q000469:parasitology*
chemical_list: D000728:Androgens; D017077:Culture Media, Conditioned; D052244:Endocrine Disruptors; D047628:Estrogen Receptor alpha
keywords: Androgens; Breast cancer; Endocrine disruptors; Estrogen; Phytoplankton