学位论文
学位类型博士
导师赵建民; 王清
2021-05-15
学位授予单位中国科学院烟台海岸带研究所
学位授予地点中国科学院烟台海岸带研究所
学位名称理学博士
学位专业海洋生物学
关键词微塑料双壳贝类毒理效应组学脂质代谢
摘要微塑料在海洋环境中无处不在，且由于其体积较小，可被多种海洋生物摄取，从而对海洋生物造成不利影响。因此，微塑料污染已引起世界各国越来越多的关注。据以往研究报道，我国沿海地区微塑料污染较严重，其中渤海尤为突出。然而，渤海区域微塑料污染特征尚未完全揭示。莱州湾是渤海的一个典型海湾，湾内河流众多，包括中国第二大河——黄河等20余条河流。莱州湾周边快速的城市化和工业化发展，以及大规模筏式水产养殖和温室蔬菜种植基地，导致各种污染物大量输入。由于微塑料体积小且可获得性高，因此会与海洋生物发生相互作用。目前，有很多室内暴露实验研究海洋环境中微塑料的生物可利用性，探讨微塑料对海洋生物的潜在影响。然而，多数暴露实验使用球形、单一聚合物和尺寸精确的商品化微塑料，并且所选择的暴露浓度通常远高于沿海水域中实际的微塑料浓度。此外，这些研究中使用的微塑料粒径小于野外环境中的实际样品，且未考虑环境微塑料样品通常以不同的尺寸存在。近年来，由于海洋双壳类生物广泛存在，且具有较强的滤水性和可食用等特点，其富集微塑料的问题受到人们的广泛关注。前期研究已经证实了微塑料在世界各地双壳类动物中的富集及其对这些生物的潜在毒性。然而，目前还缺乏对不同生态位的双壳类动物暴露于微塑料的比较研究。因此，本研究首先调查了莱州湾58个站位的表层水和沉积物、31个站位的鱼类以及养殖长牡蛎（Crassostrea gigas）、菲律宾蛤仔（Ruditapes philippinarum）和栉孔扇贝（Chlamys farreri）中的微塑料污染。然后以长牡蛎、菲律宾蛤仔和栉孔扇贝为研究对象，探讨了典型微塑料（聚乙烯（PE）和聚对苯二甲酸乙二醇酯（PET））的两种浓度（10和1000 μg/L）对双壳贝类的毒性效应及其作用机制，并运用综合生物标志物响应指数法（IBR）和证据权重（WOE）模型评估了微塑料对双壳贝类的潜在毒性风险。此外，利用代谢组和蛋白质组技术，分析了牡蛎消化腺组织对微塑料的响应情况，从分子水平上提供了PE和PET微塑料对牡蛎的毒性效应。研究结果如下：（1）微塑料在莱州湾分布广泛，形状以纤维为主。无论在表层水或沉积物中，微塑料的丰度在不同地区之间均无显著差异，表明海湾中存在多种微塑料污染源。空间热点（Getis-Ord Gi*）分析表明，微塑料污染主要集中在莱州-潍坊地区，而该地区又主要受洋流动态的影响。虽然沉积物中微塑料的空间分布与表层水不同，但也受到地形、水文和人类活动的影响。表层水中最常见的聚合物为PET，而在沉积物中则为玻璃纸（CP），这表明这些微塑料具有不同的沉降过程。低密度微塑料（PE和聚丙烯（PP））在表层水中的比例约为19.9%，但这些微塑料在沉积物中仅占约1.7%，表明低密度微塑料颗粒能够迁移至外海。微塑料在表层水、沉积物和鱼类之间的形状、大小和聚合物类型上存在显著差异（p ＜ 0.05）。聚类分析表明，孤东、黄河口和莱州-潍坊地区是微塑料的三个来源地，微塑料可能来源于河流输入、塑料回收和海洋筏式养殖。此外，远岸站点的沉积物中微塑料多样性更高，表明这些站点接收的微塑料有多个来源。本研究中，微塑料丰度在双壳贝类中存在较大差异，菲律宾蛤仔是单位重量软组织中微塑料丰度最高的物种，而牡蛎是单位个体中微塑料丰度最高的物种。造成这种现象的原因可能与生物个体大小、摄食机制以及环境中微塑料污染程度有关。本研究结果揭示了莱州湾微塑料污染的特征，将为该海域微塑料污染的风险评估和源头控制提供重要数据支撑。（2）在本研究中，在两种暴露浓度下，在长牡蛎的鳃和消化腺组织中均观察到了PE和PET微塑料的富集，证实了生物体对微塑料的摄入。PE和PET微塑料暴露后，牡蛎的摄食率和呼吸率下降，并诱导了氧化应激。此外，PE和PET微塑料都抑制了牡蛎的脂质代谢，而能量代谢酶的活性则被激活。同时，还观察到暴露的牡蛎出现消化管坏死、组织间质减少以及鳃丝上皮细胞溶解、鳃尖上皮细胞瓦解等组织病理学损伤。综合生物标志物反应（IBR）和证据权重（WOE）模型结果均表明，微塑料毒性随着浓度的增加而增大，且PET微塑料对牡蛎的毒性作用大于PE微塑料。研究结果可为揭示环境相关浓度微塑料对海洋双壳类动物的影响提供新认识，为评估现实条件下微塑料的生态风险提供数据支撑。（3）代谢组学分析表明，微塑料暴露导致牡蛎代谢谱的发生改变，从而引起能量代谢和炎症反应发生变化。对差异蛋白质的KEGG富集分析表明，微塑料暴露主要干扰了牡蛎的“花生四烯酸代谢”、“亚油酸代谢”和“甘油磷脂代谢”过程。基因本体（GO）富集分析表明，微塑料对氧化-还原过程、脂类代谢过程和磷酸戊糖途径均有影响。此外，微塑料暴露后，与脂质、有氧代谢以及细胞凋亡途径相关基因的mRNA表达量显著增加。可见，微塑料可以改变牡蛎的脂质和葡萄糖代谢过程。研究结果可以从分子水平上揭示PE和PET微塑料对牡蛎的毒性效应。（4）在本研究中，在菲律宾蛤仔（R. philippinarum）和栉孔扇贝（C. farreri）的消化腺和鳃组织中均检测到微塑料。微塑料暴露对两种双壳类动物的摄食率和呼吸率影响较小。然而，微塑料对蛤仔和扇贝造成了氧化应激、能量和脂类代谢紊乱。两种贝类的鳃和消化腺也出现了组织病理学损伤。IBR分析表明，随着微塑料浓度的增加，应激性呈升高趋势，PET微塑料对双壳类动物的毒性作用大于PE微塑料。此外，证据权重（WOE）模型分析表明，在蛤仔消化腺组织中，随微塑料浓度的增加，其危害程度增大，且PET微塑料的毒性作用大于PE微塑料。但在蛤仔和扇贝的鳃组织中，随着微塑料浓度的增加，PE微塑料的危害增加，而PET微塑料的危害程度则相反。以上结果揭示了不同种类双壳动物对环境相关浓度微塑料暴露的反应，并且发现扇贝对微塑料的敏感性高于蛤仔。本研究为环境条件下微塑料生态风险评估提供了新的见解。综上所述，微塑料在莱州湾海域的表层水、沉积物和生物体内普遍存在，其潜在污染源主要包括河流输入、塑料回收和海上筏式养殖等，且水文过程是导致莱州湾微塑料空间分布异质性的主要原因。选取代表性微塑料，并从多个层面研究了PE和PET对典型双壳贝类的毒理效应，发现微塑料暴露可引起双壳贝类的氧化应激、组织损伤以及能量和脂质代谢紊乱；结合综合生物标志物反应（IBR）和证据权重（WOE）模型，评估了微塑料对双壳贝类的潜在毒性风险，发现双壳贝类的应激反应随微塑料暴露浓度的增加呈现升高趋势，且PET微塑料对典型双壳贝类的毒性作用高于PE微塑料。本研究可为莱州湾环境介质中微塑料污染的潜在生态风险评估提供重要依据。
其他摘要Microplastics (MPs) are ubiquitous in the marine environment, and because of their small size, can be ingested by a variety of marine organisms, thus causing adverse effects on marine organisms. Therefore, microplastic contamination is attracting increasing attention worldwide. As reported by previous studies, the coastal area of China, especially the inner Bohai Sea, is one of the most seriously contaminated regions by microplastic pollution. However, the microplastic pollution characteristics in the bay area of the Bohai Sea have not been revealed. Laizhou Bay is one of the typical bays in the Bohai Sea, there are many rivers flowing into Laizhou Bay, including China's second largest river, the Yellow River, and more than 10 other rivers. Around Laizhou Bay, rapid urbanization and industrialization, as well as large-scale raft aquaculture and greenhouse vegetable cultivation bases, have led to a large input of various pollutants. Given the small size and high availability of microplastics, they are likely to interact with marine organisms. Therefore, an increasing number of laboratory exposure experiments involved the bioavailability of microplastics in the marine environment, showing the potential impacts of microplastics on marine animals. However, in most laboratory studies, commercialized microplastics with a spherical shape, single polymer and precise size are used. Moreover, the selected exposure concentrations are often very high and not representative of the expected microplastics concentrations in coastal waters. In addition, many of these studies used microplastics smaller than those reported from the field and without taking into account that microplastics are usually present in different sizes in the marine environment. In recent years, the accumulation of microplastics by marine bivalves has attracted widespread attention due to their widespread existence, high level of filter-feeding activity and edibility. Previous studies have confirmed the accumulation of microplastics in bivalves around the world and their potential toxicity toward these organisms. However, there is a lack of comparative studies on microplastics exposure to bivalves from different ecological niches. Therefore, in this study, the patterns of microplastic contamination in surface water and sediment from 58 sites, and living fish from 31 sites, and oysters (Crassostrea gigas), clams (Ruditapes philippinarum) and scallops (Chlamys farreri) were investigated in a semi-closed bay (Laizhou Bay, China). Then, the toxicities of typical microplastics (polyethylene (PE) and polyethylene terephthalate (PET)) at concentrations of 10 and 1000 μg/L and the modes of action were investigated in oysters, clams and scallops. Furthermore, the integrated biomarker response (IBR) and weight of evidence (WOE) model were employed to evaluate the potential toxic risk of microplastics on bivalves. In addition, the response of oyster digestive gland tissues to microplastics was analyzed using metabolomic and proteomic techniques to provide information on the toxic effects of PE and PET microplastics on oysters at the molecular level. The results were summarized as followed:(1) Microplastics in Laizhou Bay were pervasively distributed, particularly in the form of fibers. Microplastic abundance exhibited no significant differences among regions in either surface waters or sediment, indicating multiple sources of microplastics pollution in the bay. Spatial hotspot (Getis-Ord Gi*) analysis demonstrated that microplastic pollution was mainly concentrated in the Laizhou-Weifang area, which in turn was mainly affected by ocean current dynamics. Although the spatial distribution of microplastics in sediment was different from surface water, it was also affected by geology, hydrogeology, and anthropogenic activities. The most common polymer in the surface waters was PET, while cellophane (CP) was the most frequently observed polymer in sediment, suggesting different sinking behaviors of these microplastics. The proportion of low-density microplastics (PE and PP) in surface water was approximately 19.9%, but these microplastics accounted for only approximately 1.7% in the sediment, suggesting that low-density microplastic particles preferentially migrate to open sea. There were significant differences in shape, size and polymer type of the microplastics among surface water, sediment and biota (p < 0.05). Cluster analysis suggested that the Gudong, Yellow River Estuary and Laizhou-Weifang regions are three sources of microplastics, which might originate from river input, plastic recycling and marine raft aquaculture. Furthermore, microplastic particle diversity was greater in sediment at offshore sites, suggesting that these sites received microplastics from multiple sources. Our results characterized the microplastic pollution pattern, and will provide important information for risk evaluation and pollution control in this area.(2) In the present study, PE and PET microplastics were detected in the gills and digestive gland of oyster C. gigasfollowing exposure to both tested concentrations, confirming ingestion of microplastics by the organisms. Both PE and PET microplastic exposure decreased the clearance and respiration rates and induced oxidative stresses in the oysters. Moreover, both PE and PET microplastics inhibited lipid metabolism, while energy metabolism enzyme activities were activated in the oysters. Histopathological damage of exposed oysters was also observed in this study. Integrated biomarker response (IBR) results and the weight of evidence (WOE) model analysis showed that the toxicity induced by microplastics increased with increasing microplastics concentration, and the toxic effects of PET microplastics on oysters were greater than PE microplastics. In this study, there were significant differences in the abundance of microplastics in bivalves. The abundance of microplastics in R. philippinarum clams was highest per unit weight of soft tissues, while C. gigas oysters had the highest microplastic abundance per individual. The reasons for this phenomenon may be related to the size of individual organisms, feeding mechanisms and the degree of microplastic contamination in the environment. This study reports new insights into the consequences of microplastics exposure in marine bivalves at environmentally relevant concentrations, providing valuable information for ecological risk assessment of microplastics in realistic conditions.(3) Metabolomics analysis suggested that microplastics exposure induced alterations in metabolic profiles in oysters, with changes in energy metabolism and inflammatory responses. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis of DEPs revealed that microplastic exposure mainly disturbed the "arachidonic acid metabolism", "linoleic acid metabolism" and "glycerophospholipid metabolism" processes in oysters. Gene Ontology enrichment analysis revealed that microplastics affected the oxidation-reduction process, lipid metabolism process and pentose phosphate pathway. Moreover, a significant increase in the mRNA expression of genes related to lipid and aerobic metabolism and apoptosis pathways was observed after microplastic exposure. In summary, our results indicated that microplastics could alter lipid and glucose metabolism processes in oysters. This study provided the effects of PE and PET microplastic toxicity on oysters at the molecular level, which will contribute to better understanding the defense mechanisms of oysters against microplastic exposure.(4) In this study, microplastics were observed in the digestive glands and gills of clam R. philippinarum and scallop C. farreri. The clearance rates and respiration rate of both species of bivalves were not significantly affected by different MPs treatments. However, the MPs exposure had caused oxidative stress, energy and lipids metabolism disorder in clams and scallops. Histopathological damage was also observed in both gills and digestive gland of bivalves. Analysis of IBR values showed that a trend of increased stress with increasing MPs concentrations and the toxic effects of PET MPs on bivalves were greater than PE MPs. Additionally, the weight of evidence (WOE) model analysis suggested that the MP hazard increased with increasing MP concentration and the toxic effects of PET MPs on clam digestive glands were greater than those of PE MPs. However, in the gills of clams and scallops, the PE MPs hazard increased with increasing MP concentration, while the trend of PET MPs was the opposite. These results reported the response of different bivalves exposed in MPs at environmentally relevant concentrations. In terms of their histopathological damage and WOE analysis, the clams R. philippinarum are more sensitive to MPs than scallops C. farreri. This study provides new insights for the ecological risk assessment of MPs in realistic conditions.In conclusion, microplastics were ubiquitously detected in surface water, sediment and organism samples from Laizhou Bay. Its potential pollution sources mainly include river input, plastic recycling and marine raft culture. The hydrologic process is the main reason for the heterogeneity of microplastics spatial distribution in Laizhou Bay. By choosing PE and PET as representative microplastics, multi-level exploration towards toxicological effects of PE and PET to typical bivalves was conducted. It was found that exposure to PE and PET could cause oxidative stress, tissue damage, and disturbance of energy and lipid metabolism in bivalves. The potential toxicity risk of microplastics to bivalves was evaluated by integrated biomarker response (IBR) and the weight of evidence (WOE) model. It was found that the stress response of bivalves showed an increasing trend with increasing microplastic exposure concentration, and the toxic effect of PET microplastics was higher than that of PE microplastics. This research might provide an important basis for the potential ecological risk assessment of microplastics pollution in the environment of Laizhou Bay.
页数188
语种中文
文献类型学位论文
条目标识符http://ir.yic.ac.cnhttp://ir.yic.ac.cn/handle/133337/29343
专题中国科学院烟台海岸带研究所
推荐引用方式
GB/T 7714学位论文. 莱州湾微塑料污染特征及其对典型双壳贝类生态毒性效应研究[D]. 中国科学院烟台海岸带研究所. 中国科学院烟台海岸带研究所,2021.
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