Short-Term and Long-Term Biological Effects of Chronic Chemical Contamination on Natural Populations of a Marine Bivalve

Understanding the effects of chronic chemical contamination on natural populations of marine organisms is complex due to the combined effects of different types of pollutants and environmental parameters that can modulate the physiological responses to stress. Here, we present the effects of a chronic contamination in a marine bivalve by combining multiple approaches that provide information on individual and population health. We sampled variegated scallops (Mimachlamys varia) at sites characterized by different contaminants and contamination levels to study the short and long-term (intergenerational) responses of this species to physiological stress. We used biomarkers (SOD, MDA, GST, laccase, citrate synthase and phosphatases) as indicators of oxidative stress, immune system alteration, mitochondrial respiration and general metabolism, and measured population genetic diversity at each site. In parallel, concentration of 14 trace metals and 45 organic contaminants (PAHs, PCBs, pesticides) in tissues were measured. Scallops were collected outside and during their reproductive season to investigate temporal variability in contaminant and biomarker levels. Our analyses revealed that the levels of two biomarkers (Laccase-type phenoloxidase and malondialdehyde) were significantly correlated with Cd concentration. Additionally, we observed significant seasonal differences for four of the five biomarkers, which is likely due to the scallop reproductive status at time of sampling. As a source of concern, a location that was identified as a reference site on the basis of inorganic contaminant levels presented the same level of some persistent organic pollutants (DDT and its metabolites) than more impacted sites. Finally, potential long-term effects of heavy metal contamination were observed for variegated scallops as genetic diversity was depressed in the most polluted sites.

由于不同类型污染物与可调节应激生理反应的环境参数共同作用，解析长期化学污染对海洋生物自然种群的影响颇具复杂性。本研究通过整合多种可获取个体与种群健康信息的研究方法，阐明了海洋双壳类受到长期污染的效应。我们在污染物类型与污染水平各异的采样点位采集杂色扇贝（Mimachlamys varia），以探究该物种对生理应激的短期与长期（跨世代）响应。本研究采用生物标志物（biomarker）——超氧化物歧化酶（SOD）、丙二醛（MDA）、谷胱甘肽S-转移酶（GST）、漆酶（laccase）、柠檬酸合酶（citrate synthase）与磷酸酶——作为氧化应激、免疫系统紊乱、线粒体呼吸与整体代谢的指示物，并测定了各采样点位的种群遗传多样性。同时，我们测定了扇贝组织中14种痕量金属与45种有机污染物（多环芳烃PAHs、多氯联苯PCBs、农药）的含量。我们分别在繁殖季与非繁殖季采集杂色扇贝，以探究污染物与生物标志物水平的时间变异性。分析结果显示，两种生物标志物——漆酶型酚氧化酶与丙二醛（MDA）的水平与镉（Cd）浓度显著相关。此外，我们观测到五种生物标志物中有四种存在显著的季节差异，这大概率与采样时扇贝的生殖状态相关。值得关注的是，一个基于无机污染物水平被划定为参照点位的区域，其部分持久性有机污染物（DDT及其代谢物）的含量与受污染程度更高的点位并无显著差异。最后，在污染程度最高的采样点位中，杂色扇贝的遗传多样性显著降低，这表明重金属污染可能对其产生长期潜在影响。