R4 PM Effects and Risk Assessment of Pharmaceutical and Other Emerging Wastewater Contaminants in Aquatic Systems
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in Ballroom 4

(KID-1117-827167) Responses of a freshwater food web to a potent estrogen.

Kidd, K^{1, 2}, Paterson, M.², Blanchfield, P.², Mills, K.², Findlay, D.², Salki, A.², ¹ University of New Brunswick, Saint John, New Brunswick, Canada² Fisheries and Oceans Canada, Winnipeg, Manitoba, Canada

ABSTRACT- A whole-lake study was conducted from 1999-2005 at the Experimental Lakes Area in northwestern Ontario to determine whether the potent synthetic estrogen 17 ethynylestradiol (EE2) affects freshwater food webs. EE2 was added continuously to Lake 260 in each of the summers of 2001-2003 to maintain surface water concentrations between 4 and 6 ng L^-1. Water chemistry and microbial, algal, and zooplankton populations were sampled in this lake bi-weekly in the two years before and after dosing and in the three years of EE2 additions, and compared to reference lake samples collected over the same time period. In addition, large and small fish species were monitored for population-level effects in the spring and fall of each year in the EE2 amended and reference lakes. Microbial abundances ranged from 0.04 to 0.3 mg L^-1 in the study lake, and were similar before and after the additions of the estrogen. In contrast, the algal biomass in Lake 260 was lowest in 2003 at 465 mg m^-3 compared to 600-900 mg m^-3 in previous years, and may be related to increased grazing due to changes in food web structure. Mean annual zooplankton biomass in the study lake was similar from 1999-2003 and ranged between 20 to 80 ug L^-1. In 2003, however, there was increased abundance of Daphnia pulex, Diaphanosoma birgei, and rotifers when compared to previous years' data. This change in the zooplankton community composition may be due to the effects of EE2 on the fish species in Lake 260. As one example, a loss of the smaller size classes was observed for the fathead minnow population. Results from this study suggest that a potent estrogen can have both direct and indirect effects on aquatic populations.

Key words: ethynylestradiol, freshwater food web, endocrine disruptors