Growing human populations and increasingly intensive agriculture have resulted in widespread aquatic nitrate pollution. Freshwater mussel populations have been in decline for decades but often are underrepresented in data used for the development of ambient water quality criteria and acute toxicity of nitrate to mussel glochidia has not yet been established. Additionally, toxicity testing with aquatic species often is limited to a few model species; however, relatively little is known about how representative model species are of imperiled species. Therefore, to better define the acute toxicity of nitrate to common and rare aquatic species, we conducted 24-h nitrate acute toxicity tests with glochidia of four species of freshwater mussels, including a federally threatened species (Hamiota altilis) and 7-day tests with larval fish of three species: fathead minnow (Pimephales promelas), tricolor shiner (Cyprinella trichroistia), and tilapia (Oreochromis spp.), across a range of water hardness. Median effective concentrations (EC50s) in freshwater mussel glochidia ranged from 524 to 904 mg/L NO3-N in moderately hard water. In fish, median lethal concentrations (LC50s) ranged from 228 to 1725 mg/L NO3-N and varied with water hardness. Of the species tested, generally sensitivity of the common species was similar to the rare species, although relative sensitivity varied with water hardness. Based on these results, we can conclude that acute lethal effects are unlikely for the fish and mussel species considered here at current environmental levels, but the results of these standardized tests are useful for the development of ambient water quality criteria and other regulatory and management decisions regarding acute nitrate exposures.

中文翻译：

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硝酸盐对普通和濒危淡水贻贝Glochidia和幼虫鱼的比较毒性。

人口的增长和农业的集约化导致广泛的硝酸硝酸盐污染。淡水贻贝种群已经减少了数十年，但在用于制定环境水质标准的数据中却往往不足，而且尚未确定硝酸盐对贻贝贻贝的急性毒性。此外，对水生物种的毒性测试通常仅限于少数几个模型物种。但是，关于代表性的模型物种是濒危物种的了解却很少。因此，为了更好地确定硝酸盐对常见和稀有水生物种的急性毒性，我们对四种淡水贻贝的甲状目进行了24小时硝酸盐急性毒性测试，包括受到联邦威胁的物种（Hamiota altilis）以及为期7天的测试。三种幼体鱼：在整个水硬度范围内，黑头min鱼（Pimephales promelas），三色光泽（Cyprinella trichroistia）和罗非鱼（Oreochromis spp。）。在中度硬水中，淡水贻贝球藻的中位有效浓度（EC50s）为524至904 mg / L NO3-N。在鱼类中，NO3-N的致死浓度中位数（LC50）为228至1725 mg / L，并随水的硬度而变化。在测试的物种中，一般物种的敏感性通常与稀有物种相似，尽管相对敏感性随水硬度而变化。根据这些结果，我们可以得出结论，在目前的环境水平下，这里考虑的鱼类和贻贝不太可能具有急性致死作用，