Uptake of estrone from the water column by a coral community

Abstract.

Estrogens and other steroids are present in coral tissues and are hypothesized to regulate reproductive processes. It is not known whether corals synthesize estrogens, accumulate them from dietary sources, or concentrate them from overlying seawater. To determine whether corals can remove estrogens from the water column, we conducted a series of experiments in a 24-m flume filled with 2 m² of scleractinian corals. In each experiment, the flume was spiked with estrone (initial concentrations 1,000–2,500 pg l^–1), water was recirculated, and water samples were collected intermittently for 1–7 days. Corals removed estrone from the water column at a rate proportional to concentration [rate=S(estrone)]; the estimated first-order rate constant (S) was 85×10^–6 m s^–1 (95% confidence limit ±24×10^–6 m s^–1). The reported rate constants are close to maximal uptake rates, based on mass transfer theory of nutrient uptake by corals. Incubations of coral tissue with tritiated estrone corroborated flume experiments and demonstrated that estrone was removed from the water column by live corals about twice as fast as estrone was adsorbed to the surface of dead coral. Given that concentrations of dissolved estrone are 50–1,000 pg l^–1 over coral reefs, uptake rates of estrogen into coral communities from the water column are in the range of 0.37–7.3×10⁶ pg estrone m^–2 day^–1 with estimated turnover times of 6–115 days. We conclude that estrogens can be removed from the water column by corals and can accumulate in coral tissue.