Department of Natural Resources Management and Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Agricultural Sciences Room 218, 15th and Boston, Lubbock, TX 74909, USA.
Water Res. 2012 Dec 15;46(20):6638-51. doi: 10.1016/j.watres.2012.05.002. Epub 2012 May 23.
The Double Mountain Fork Brazos River (Texas, USA) consists of North (NF) and South Forks (SF). The NF receives urban runoff and twice-reclaimed wastewater effluent, whereas the SF flows through primarily rural areas. The objective of this study was to determine and compare associations between standard water quality variables and ichthyotoxicity at a landscape scale that included urban (NF) and rural (SF) sites. Five NF and three SF sites were sampled quarterly from March 2008 to March 2009 for specific conductance, salinity, hardness, pH, temperature, and turbidity; and a zebrafish (Danio rerio) embryo bioassay was used to determine ichthyotoxicity. Metal and nutrient concentrations at all sites were also measured in addition to standard water quality variables in spring 2009. Principal component analyses identified hardness, specific conductance, and salinity as the water variables that best differentiate the urban NF (higher levels) from rural SF habitat. Nutrient levels were also higher in the NF, but no landscape scale patterns in metal concentrations were observed. Ichthyotoxicity was generally higher in NF water especially in winter, and multiple regression analyses suggested a positive association between water hardness and ichthyotoxicity. To test for the potential influence of the toxic golden alga (Prymnesium parvum) on overall ichthyotoxicity, a cofactor known to enhance golden alga toxin activity was used in the bioassays. Golden alga ichthyotoxicity was detected in the NF but not the SF, suggesting golden alga may have contributed to overall ichthyotoxicity in the urban but not in the rural system. In conclusion, the physicochemistry of the urban-influenced NF water was conducive to the expression of ichthyotoxicity and also point to water hardness as a novel factor influencing golden alga ichthyotoxicity in surface waters.
得克萨斯州的双山叉布拉索斯河（Double Mountain Fork Brazos River，USA）由北叉（North Fork，NF）和南叉（South Fork，SF）组成。北叉接收城市径流和两次回收的废水污水，而南叉则流经主要的农村地区。本研究的目的是确定和比较景观尺度上标准水质变量与鱼类毒性之间的关联，该景观包括城市（NF）和农村（SF）地区。2008 年 3 月至 2009 年 3 月，每季度在北叉的五个地点和南叉的三个地点采集样本，以测定电导率、盐度、硬度、pH 值、温度和浊度；并使用斑马鱼（Danio rerio）胚胎生物测定法来确定鱼类毒性。除了在 2009 年春季测量所有地点的标准水质变量外，还测量了金属和营养物浓度。主成分分析确定硬度、电导率和盐度是将城市北叉（水平较高）与农村南叉生境区分开来的最佳水质变量。NF 中的营养物水平也较高，但未观察到金属浓度的景观尺度模式。鱼类毒性在 NF 水中通常较高，尤其是在冬季，多元回归分析表明水硬度与鱼类毒性之间存在正相关关系。为了测试有毒的金色藻类（Prymnesium parvum）对整体鱼类毒性的潜在影响，在生物测定中使用了已知增强金色藻类毒素活性的辅助因子。在 NF 中检测到金色藻类的鱼类毒性，但在 SF 中未检测到，这表明金色藻类可能对城市系统的整体鱼类毒性有贡献，但对农村系统没有贡献。总之，受城市影响的 NF 水的物理化学性质有利于鱼类毒性的表达，并指出水硬度是影响地表水中金色藻类鱼类毒性的新因素。
