Department of Biology, University of Saskatchewan, 112 Campus Drive, Saskatoon, SK, Canada S7N 5E2.
Ecotoxicol Environ Saf. 2013 May;91:188-97. doi: 10.1016/j.ecoenv.2013.02.002. Epub 2013 Mar 1.
Metal mine effluents can impact fish in the receiving environment via both direct effects from exposure as well as indirect effects via food web. The main objective of the present study was to assess whether an indirect effect such as reduced food (prey) availability could influence metal accumulation and reproductive capacity in fish during chronic exposure to a metal mine effluent. Breeding pairs of fathead minnows (Pimephales promelas) were exposed to either reference water (RW) or an environmentally relevant metal mine effluent [45 percent process water effluent (PWE)] for 21 days and fed either low food quantities [LF (a daily ration of 6-10 percent body weight)] or normal food quantities [NF (a daily ration of 20-30 percent body weight)] in artificial stream systems. Fish in RW treatments were fed Chironomus dilutus larvae cultured in RW (Treatments: RW-NF or RW-LF), while fish in PWE treatments were fed C. dilutus larvae cultured in PWE (Treatments: PWE-NF or PWE-LF). Tissue-specific (gill, liver, gonad and carcass) metal accumulation, egg production, and morphometric parameters in fish were analyzed. Fathead minnows that were exposed to LF rations had significantly smaller body, gonad and liver sizes, and were in a relatively poor condition compared to fathead minnows exposed to NF rations, regardless of the treatment water type (RW or PWE) (two-way ANOVA; p<0.05). Although elevated concentrations of copper, nickel, rubidium, selenium, and thallium were recorded in C. dilutus cultured in PWE, only the concentrations of rubidium, selenium and thallium increased in tissues of fish in PWE treatments. Interestingly though, despite the greater abundance of metal-contaminated food in the PWE-NF treatment, tissue metal accumulation pattern were almost similar between the PWE-NF and PWE-LF treatments, except for higher liver barium, cobalt and manganese concentrations in the latter treatment. This indicated that a higher food ration could help reduce the tissue burden of at least some metals and thereby ameliorate the toxicity of metal-mine effluents in fish. More importantly, cumulative egg production in fish was found to be lowest in the PWE-LF treatment, whereas fish egg production in the PWE-NF treatment was not impacted. Overall, these findings suggest that decreased food abundance could have a greater impact than metal accumulation in target tissues on the reproductive capacity of fish inhabiting metal-mine effluent receiving environments.
金属矿山废水可通过直接暴露和食物网的间接途径影响受纳环境中的鱼类。本研究的主要目的是评估在慢性暴露于金属矿山废水中，食物（猎物）减少等间接效应是否会影响鱼类的金属积累和繁殖能力。采用人工溪流系统，将繁殖期的黑头呆鱼（Pimephales promelas）暴露于参考水（RW）或具有环境相关性的金属矿山废水中[45%工艺废水（PWE）]，并以低食物量[LF（每日体重的 6-10%）]或正常食物量[NF（每日体重的 20-30%）]喂养。RW 处理组的鱼以在 RW 中培养的摇蚊幼虫（Chironomus dilutus）为食（处理：RW-NF 或 RW-LF），而 PWE 处理组的鱼则以在 PWE 中培养的摇蚊幼虫为食（处理：PWE-NF 或 PWE-LF）。分析了鱼体组织特异性（鳃、肝、性腺和尸体）金属积累、产卵量和形态参数。与 NF 处理相比，暴露于 LF 处理的鱼的体质量、性腺和肝质量明显较小，身体状况较差，而与处理水类型（RW 或 PWE）无关（双因素方差分析；p<0.05）。尽管在 PWE 中培养的摇蚊幼虫中记录到铜、镍、铷、硒和铊的浓度升高，但只有铷、硒和铊的浓度在 PWE 处理组的鱼组织中增加。有趣的是，尽管 PWE-NF 处理中金属污染食物的丰度较高，但 PWE-NF 和 PWE-LF 处理之间的组织金属积累模式几乎相似，只是后者处理中的肝钡、钴和锰浓度较高。这表明较高的食物量可以帮助减少至少一些金属的组织负担，从而减轻鱼类对金属矿山废水的毒性。更重要的是，发现鱼的累积产卵量在 PWE-LF 处理中最低，而 PWE-NF 处理中鱼的产卵量没有受到影响。总体而言，这些发现表明，与目标组织中的金属积累相比，食物丰度的减少可能对栖息在金属矿山废水受纳环境中的鱼类的繁殖能力产生更大的影响。
