Inhibition of growth of Anabaena variabilis population by single and mixed steroid hormones

Abstract

Many contaminants which are toxic and adversely affect living organisms enter surface waters. Among them, there are endocrine compounds such as steroid hormones, which can disrupt the endocrine system causing an adverse effect on the physiology of aquatic organisms. In the literature, there is not enough information about the influence of steroid hormones on phytoplankton growth. Therefore, the aim of this research was to study the effect of estrogens (estrone, 17ß-estadiol, 17-α-ethinylestradiol, and estriol), progestagens (progesterone, 5-pregnen-3b-ol-20-one, and levonorgestrel), and androgens (testosterone) on the growth of the cyanobacterium Anabaena variabilis. To our best knowledge, the chronic toxicological effects of hormones on cyanobacteria are explored for the first time. From among single steroid hormones, progesterone and 17-α-ethinylestradiol are the most toxic (EC 50 48.59 and 82.95 mg L −1 ). On the other hand, incubation in the presence of 5-pregnen-3b-ol-20-one, testosterone, and 17ß-estadiol caused slight inhibition of growth (EC 50 283.50, 336.68, and 437.82 mg L −1 ), while estrone, estriol, and levonorgestrel showed no significant effect on the growth of this cyanobacterium. Hormone mixtures have been found to be more toxic than single substances and exposure to them leads to the potentiation of toxicity. The EC 50 after 14 days of the test duration for the mixed steroid hormones were 45.14, 37.00, and 89.46 mg L −1 . This research provides a basic understanding of hormone toxicity to aquatic organism, such as cyanobacteria, and asserts a more comprehensive view on ecological risk evaluation. [Figure not available: see fulltext.].