Hill B H, Lazorchak J M, McCormick F H, Willingham W T
National Exposure Research Laboratory, US Environmental Protection Agency, 26W Martin Luther King Drive, Cincinnati, OH 45268, USA.
Environ Pollut. 1997;95(2):183-90. doi: 10.1016/s0269-7491(96)00123-6.
The effects of elevated metals (dissolved Zn, Mn and/or Fe) in a Rocky Mountain stream were assessed using measures of primary productivity, community respiration and water-column toxicity. Primary productivity was measured as rates of O2 evolution from natural substrates incubated in situ in closed chambers. Oxygen depletion within these chambers, when incubated in the dark, provided estimates of periphyton community respiration. Sediment community respiration on fine-grained sediments, collected and composited along each stream study reach, was measured on-site by incubating these sediments in closed chambers and measuring O2 depletion. Toxicity was measured as percent mortality of Ceriodaphnia dubia during 48 h acute tests. Gross (GPP) and net primary productivity (NPP) decreased significantly with increasing metal concentrations, from 10.88 +/- 1.46 g O2 m(-2) day(-1) to 0.83 +/- 0.20 g O2 m(-2) day(-1) and 9.85 +/- 1.43 g O2 m(-2) day(-1) to 0.81 +/- 0.20 g O2 m(-2) day(-1), respectively for the reference and most impacted site. Community respiration (CR) declined from 0.65 +/- 0.08 g O2 m(-2) day(-1) to 0.02 +/- 0.01 g O2 m(-2) day(-1) with increasing metal concentrations. Sediment community respiration (SCR) decreased from 0.26 +/- 0.02 g O2 m(-2) day(-1) to 0.01 +/- 0.01 g O2 m(-2) day(-1) at these same sites. Ceriodaphnia dubia mortality increased from 0% at the reference site to 95 +/- 5% at the most impacted sites. Net daily metabolism, quantum yield and assimilation ratio all decreased with increasing metal concentrations, suggesting that both autotrophic and heterotrophic components of the periphyton community were impaired. Overall, functional measures were able to discern sites receiving greater metal impacts from less-impacted sites, with combinations of dissolved metals explaining between 25 and 92% of the variance in the regression models. Using these regression models we were able to calculate lethal and inhibition concentrations of dissolved Zn in the Eagle River. The lethal concentration (LC50) of Zn for Ceriodaphnia dubia is 123 mg liter(-1). The concentrations of Zn which inhibited respiration (IC50) were 177 mg liter(-1) for CR and 199 mg liter(-1) for SCR. These results indicate functional measures may be as sensitive to metal concentrations as acute toxicity tests.
利用初级生产力、群落呼吸和水柱毒性指标，评估了落基山溪流中金属（溶解态锌、锰和/或铁）含量升高所产生的影响。初级生产力通过原位封闭培养箱中天然底物的氧气释放速率来衡量。在黑暗中培养时，这些培养箱内的氧气消耗可用于估算附生植物群落呼吸。沿着每条溪流研究河段收集并混合的细粒沉积物的沉积物群落呼吸，通过在封闭培养箱中培养这些沉积物并测量氧气消耗来现场测定。毒性通过在48小时急性试验中双齿大眼溞的死亡率来衡量。随着金属浓度的增加，总初级生产力（GPP）和净初级生产力（NPP）显著下降，参考站点和受影响最严重的站点分别从10.88±1.46克氧气·平方米⁻²·天⁻¹降至0.83±0.20克氧气·平方米⁻²·天⁻¹，以及从9.85±1.43克氧气·平方米⁻²·天⁻¹降至0.81±0.20克氧气·平方米⁻²·天⁻¹。随着金属浓度的增加，群落呼吸（CR）从0.65±0.08克氧气·平方米⁻²·天⁻¹降至0.02±0.01克氧气·平方米⁻²·天⁻¹。在这些相同的站点，沉积物群落呼吸（SCR）从0.26±0.02克氧气·平方米⁻²·天⁻¹降至0.01±0.01克氧气·平方米⁻²·天⁻¹。双齿大眼溞的死亡率从参考站点的0%增加到受影响最严重站点的95±5%。净日代谢、量子产率和同化率均随着金属浓度的增加而降低，这表明附生植物群落的自养和异养成分均受到损害。总体而言，功能指标能够区分受金属影响较大的站点和受影响较小的站点，溶解态金属的组合在回归模型中解释了25%至92%的方差。利用这些回归模型，我们能够计算出伊格尔河中溶解态锌的致死浓度和抑制浓度。双齿大眼溞对锌的致死浓度（LC50）为123毫克·升⁻¹。抑制呼吸的锌浓度（IC50），对于CR为177毫克·升⁻¹，对于SCR为199毫克·升⁻¹。这些结果表明，功能指标对金属浓度的敏感性可能与急性毒性试验一样高。
