Data from: Persistent organic pollution in a high-Arctic top predator: sex-dependent thresholds in adult survival

In long-lived species, any negative effect of pollution on adult survival may pose serious hazards to breeding populations. In the present study we measured concentrations of various organochlorines (OCs: PCB and organochlorine pesticides) in the blood of a large number of adult glaucous gulls (Larus hyperboreus) breeding on Bjørnøya (Bear Island) in the Norwegian Arctic, and modelled their local survival using capture–recapture analysis. Survival was negatively associated with concentrations of OCs in the blood. The effect of OCs was nonlinear and evident only among birds with the highest concentrations (the uppermost deciles of contamination). The threshold for depressed survival differed between the sexes, with females being more sensitive to contamination. For birds with lower OC concentration, survival was very high, i.e. at the upper range of survival rates reported from glaucous and other large gull species in other, presumably less contaminated populations. We propose two non-exclusive explanations. Firstly, at some threshold of OC concentration, parents (especially males) may abandon reproduction to maximise their own survival. Secondly, high contamination of OC may eliminate the most sensitive individuals from the population (especially among females), inducing a strong selection towards high-quality and less sensitive phenotypes.

对于长寿命物种而言，污染物对成体存活的任何负面影响，均可能对其繁殖种群构成严重威胁。本研究检测了挪威北极圈区域熊岛（Bjørnøya，Bear Island）上繁殖的大量成年北极鸥（Larus hyperboreus）血液中的各类有机氯污染物（organochlorines，OCs：多氯联苯（PCB）与有机氯农药）浓度，并通过捕获-再捕获分析对其局部种群存活情况进行了建模。研究结果显示，成体存活率与血液中OCs浓度呈负相关关系。有机氯污染物的影响呈非线性特征，且仅在污染物浓度最高的个体（即污染程度最高的十分位数组）中表现显著。存活率下降的阈值存在性别差异，雌性个体对污染更为敏感。对于血液OCs浓度较低的个体，其存活率极高，达到了已报道的北极鸥及其他大型鸥类在其他（推测污染程度更低的）种群中的存活率上限区间。我们提出两种非互斥的解释机制：其一，当OCs浓度达到某一阈值时，亲鸟（尤其是雄性亲鸟）可能会放弃繁殖，以最大化自身存活概率；其二，高浓度有机氯污染可能会将种群中最敏感的个体（尤其是雌性个体）淘汰，从而引发针对高质量、低敏感表型的强烈选择作用。