Exposure of female juvenile rainbow trout to alkylphenolic compounds results in modifications to growth and ovosomatic index

Abstract

Abstract The alkylphenol ethoxylates (APEOs) are a major group of nonionic surfactants. Biodegradation of these compounds is incomplete during sewage treatment; thus, they are ubiquitous aquatic pollutants. All the main degradation products of APEOs were recently demonstrated to have estrogenic properties in vitro, but their effects in vivo remain to be established. In this study, female juvenile rainbow trout (Oncorhynchus mykiss Walbaum) were exposed to octylphenol, nonylphenol (NP), nonylphenol diethoxylate, and nonylphenol mono-carboxylic acid (NP1EC) at environmentally relevant concentrations (Experiment 1: 1, 10, and 50 μg/L; Experiment 2: 1, 10, and 30 μg/L). Exposure to APEOs commenced at hatch (day 0) and was terminated on day 22 (Experiment 1) or day 35 (Experiment 2). Body weight and fork length of representative samples offish from each treatment group were recorded at intervals up to 108 d (Experiment 1) or 466 d (Experiment 2). In Experiment 1, significant differences in size of the exposed fish, related to treatment, were still apparent on day 108, 86 d after withdrawal of the treatments. These observations were confirmed during Experiment 2, in which significant changes in body weight and fork length as a consequence of exposure to the compounds were observed approx. 15 d after exposure was terminated. These differences were sustained for at least 466 d in the case of NP and NP1EC. In addition, the ovosomatic index (OSI) offish exposed to NP and NP1EC was significantly affected zby the treatment. Survival of fish in the natural environment is strongly influenced by body size, and an appropriate OSI is a crucial factor in successful reproduction. Therefore, exposure of natural populations of fish to these chemicals at concentrations currently measurable in the aquatic environment may have an impact on the performance of those populations.