Ecological Impacts of Industrial Effluent in Surface Waters and Fish

PROJECT OVERVIEW
Phytoestrogens are plant-based compounds that are discharged into surface water from wastewater treatment plants and certain industrial facilities. Phytoestrogens mimic the hormone estrogen and can therefore interfere with normal biological development. For example, it is known that they can feminize male fish. However, the broader effects of phytoestrogens have not been studied and almost nothing is known about their long-term fate or persistence in the environment. Through this appropriation scientists from the University of Minnesota and St Cloud State University will collaborate to examine the persistence of phytoestrogens in surface waters and their effects on fish. Findings will be used to enhance wastewater treatment and help facilitate continued industrial development and production in Minnesota done in an environmentally sensitive manner.

OVERALL PROJECT OUTCOME AND RESULTS
Phytoestrogens are plant-based compounds that mimic estrogen and can interfere with normal biological development. Research shows that phytoestrogens are discharged into surface water from wastewater treatment plants and certain industries. The biological effects of these compounds have not been well studied, although it is known that they can feminize male fish. Almost nothing is known about their environmental fate. When these compounds enter rivers and streams, it is likely that they will be degraded and therefore may have a lessened impact on biota, but this needs to be confirmed.

In this project, the persistence of two common phytoestrogens (genistein and daidzein) was studied. Fathead minnow exposure experiments at realistic environmental concentrations were also performed. Experiments demonstrated that genistein and daidzein reacted with sunlight. These two compounds also biodegraded rapidly in natural water samples; the rate of degradation depended on phytoestrogen concentration, water/incubation temperature, and the source of the water. Sorption experiments showed that phytoestrogens sorb to sediment, but this is not likely to be an important loss mechanism. Adult fathead minnow exposure experiments showed that only subtle effects on anatomy, physiology, and behavior of fathead minnows occurred as a result of exposure to phytoestrogens singly or in mixtures. The one exception to this was the fact that adult fathead minnows produced significantly more eggs when exposed to daidzein. Larval minnow exposures showed that exposure to genistein, formononetin (another common phytoestrogen), and a mixture of phytoestrogens had a negative impact on larval survival. Adult and larval exposures to microbiologically degraded phytoestrogens showed negative impacts on adult egg production. This research indicates that genistein, daidzein, and formononetin are unlikely to cause widespread ecological harm themselves in the absence of other stressors; nevertheless, caution should be exercised with respect to high concentration effluents due to the potentially anti-estrogenic effects of phytoestrogen degradates.

PROJECT RESULTS USE AND DISSEMINATION
Results have been disseminated at several conferences. In addition, one manuscript has been published, two additional manuscripts have been submitted, and a fourth is being revised and will be submitted for publication in August or September, 2013. This project also resulted in the generation of two Master's theses and one Ph.D. thesis.