(Table 1) Concentration of pollutants in hair of East Greenland polar bears (Ursus maritimus)

Hair sampled from 96 East Greenland polar bears (Ursus maritimus) over the periods 1892-1927 and 1988-2009 was analyzed for cortisol as a proxy to investigate temporal patterns of environmental stress. Cortisol concentration was independent of sex and age, and was found at significantly higher (p<0.001) concentrations in historical hair samples (1892-1927; n = 8) relative to recent ones (1988-2009; n = 88). In addition, there was a linear time trend in cortisol concentration of the recent samples (p< 0.01), with an annual decrease of 2.7%. The recent hair samples were also analyzed for major bioaccumulative, persistent organic pollutants (POPs). There were no obvious POP related time trends or correlations between hair cortisol and hair POP concentrations. Thus, polar bear hair appears to be a relatively poor indicator of the animal's general POP load in adipose tissue. However, further investigations are warranted to explore the reasons for the temporal decrease found in the bears' hair cortisol levels.

本研究对1892年至1927年、1988年至2009年间采集的96头东格陵兰岛北极熊（Ursus maritimus）毛发样本中的皮质醇进行了检测，以皮质醇作为替代标志物，探究环境压力的时间变化模式。研究发现，皮质醇浓度与北极熊的性别和年龄均无相关性，且历史毛发样本（1892-1927年，n=8）中的皮质醇浓度显著高于近期样本（1988-2009年，n=88），差异具有统计学意义（p<0.001）。此外，近期毛发样本的皮质醇浓度呈现线性时间下降趋势，年均降幅达2.7%，差异具有统计学意义（p<0.01）。本研究同时对近期毛发样本中的主要生物累积性持久性有机污染物（Persistent Organic Pollutants, POPs）进行了检测，未观察到明显的POPs相关时间趋势，且毛发皮质醇浓度与毛发POPs浓度之间也未发现显著相关性。由此可见，北极熊毛发并不能较好地反映该物种脂肪组织中总体POPs负荷水平。不过，仍需开展进一步研究以探明北极熊毛发皮质醇浓度随时间下降的内在原因。