胶州湾海洋生态系统国家野外研究站知识库

  作为新兴污染物，微塑料给海洋生物及生态系统的健康造成了一定的威胁。近年来微塑料污染已经引起了科学界和社会公众们的广泛关注。微塑料在海洋环境中分布较广，目前许多研究已经对海水、沉积物及生物中微塑料的污染进行了报道，但微塑料在海洋中的命运仍不清楚。厘清微塑料在海洋中的迁移过程、汇集区域及分布归趋对于控制微塑料污染十分重要。垂直运输作为微塑料在海洋环境中分布和命运的重要研究问题之一，生物介导的垂直迁移占据着重要地位，但目前基于不同类型的底栖动物对微塑料在沉积物中垂直分布的影响的研究仍较匮乏。胶州湾位于中国山东半岛南部，沿岸有十余条河流汇入，居民人口密度大，生态系统受人类活动影响十分严重，是中国近海典型的半封闭海湾。作为典型的化能自养生态系统，南海的F冷泉是中国最活跃的冷泉之一，已有许多地质和生物调查在此展开。本研究选取胶州湾及南海F冷泉区两大受人类活动影响迥异的典型海域为研究对象，基于野外调查和室内培养实验两种方式，调查了底栖动物群落中微塑料的赋存特征，探讨了底栖动物通过生物扰动活动对微塑料垂直迁移的影响及机制。得到的主要结论如下：

  为了探索胶州湾中典型底栖动物的微塑料赋存特征，本研究选取长牡蛎Crassostrea gigas和菲律宾蛤仔Ruditapes philippinarum两种重要经济物种作为研究对象，分别在2018年12月和2019年3月采集了样品，经过生物处理、碱性消解、抽滤分离、成分鉴定及统计分析等步骤，首次报道并比较了野生和养殖两种生长方式下生物摄入微塑料的情况。胶州湾贝类摄入微塑料的平均丰度为1.21个/g（或2.17个/个体），其中，菲律宾蛤仔体内的微塑料平均丰度为1.51个/g（2个/个体），长牡蛎为0.92个/g（2.34个/个体），蛤仔体内的含量显著高于牡蛎体内含量。与其他地区相比，胶州湾贝类的微塑料污染处于中等水平。对不同生长方式下的生物进行比较，发现养殖和野生两种生长方式对贝类摄食微塑料的影响并不显著。胶州湾贝类生物中大部分（92.97％）微塑料呈纤维状，主要颜色为黑色（42.97％），37.5%的微塑料尺寸在500 μm以下，且随着尺寸的增加，微塑料含量逐渐降低。赛璐玢（Cellophone）和聚对苯二甲酸乙二醇酯（Polyethylene terephthalate）为贝类体内主要的微塑料成分。通过中国人对贝类饮食的消费量推断，平均每人每年通过食用贝类摄入微塑料的风险较低，数量约为1.57×10³个。

  在摸排清胶州湾贝类微塑料污染的基础上，为进一步研究胶州湾底栖动物群落的微塑料赋存特征，评估生物储存库的作用，并分析影响生物摄食微塑料的因素，本研究在2018年12月-2019年9月按季度采集了胶州湾的大型底栖动物样品并分析了其体内的微塑料污染情况。研究将底栖动物分为六组：多毛类、软体类、甲壳类、棘皮类、鱼类和其他。研究发现：第一，胶州湾底栖动物群落中微塑料的赋存量约为36.4公斤，与沉积物中的赋存量和大气沉降量相比，该含量不可忽略。微塑料的平均丰度为1.00 ± 0.11个/个体（15.49 ± 3.49个/g），以个体为单位进行不同类群的微塑料污染比较，鱼类体内的微塑料含量明显多于其他类别的生物，而以质量为单位进行比较，甲壳类的微塑料含量最高；第二，底栖动物中的微塑料特征主要体现在形状呈纤维状，颜色以黑色为主，成分多为聚乙烯（Polyethylene），尺寸<500 μm的含量最高，所有底栖动物中微塑料的平均大小为1103.4 μm；第三，底栖动物对微塑料的摄食是一个复杂的问题，受生物和环境等多种因素的调节，生物的质量、周围海水环境、空间和时间变化均会对其产生影响。微塑料在底栖动物群落中进行了重新分配，即在一定区域中，不同生物类群的微塑料平均含量随类群生物密度的增加而下降。

  在完成海湾底栖动物微塑料污染调查的基础上，本研究继续对受人类活动较小的偏远地区——中国南海的F冷泉区（化能合成生态系统）展开了调查。结果显示冷泉底栖群落中的两种优势生物（深海偏顶蛤Gigantidas platifrons和柯氏潜铠虾Shinkaia crosnieri）体内均有微塑料的存在，但两种生物体内的丰度不存在显著差异。微塑料在两种底栖动物中的丰度分别为0.13和0.17个/个体，与胶州湾底栖动物相比，无论是生物的微塑料丰度还是微塑料的检出率，深海冷泉物种的结果均要低一些。通过扫描电镜对冷泉生物体内的微塑料表面形貌进行观察，发现微塑料出现了严重的磨损。这些化能合成共生体中微塑料的主要特征是呈现纤维形状（62.5%），主要成分为聚酯（54.2%），大多外观透明（45.8%），纤维状和碎片状的微塑料平均尺寸分别为1807 μm和483 μm。由于冷泉生态系统具有较高的生物密度，南海F冷泉区每平方米栖息的底栖生物(仅考虑深海偏顶蛤和柯氏潜铠虾两个优势物种）体内大约含有86.5个微塑料。该结果与人们所熟悉的近岸生物体内的微塑料赋存量相当，与南海及所在站点周围表层海水环境中微塑料的赋存量相比要高得多，因此冷泉底栖生态系统在区域海洋的微塑料迁移中可能扮演着重要储存库的作用。

  基于底栖动物对微塑料摄食的普遍现象，本研究还选取菲律宾蛤仔为研究对象，在实验室中模拟了蛤仔的生物扰动作用下聚苯乙烯（Polystyrene, PS）塑料微珠（规格为200 μm）在沉积物中迁移的现象。研究结果显示，菲律宾蛤仔在暴露于环境浓度相关的PS微珠中时，表现出了延长适应环境的时间的行为，但随后的掘穴行为（含埋栖率和掘穴速度）并未受到影响。经过14天的微塑料暴露，蛤仔的条件指数、清滤率和耗氧率也未表现出显著的胁迫性影响。在生物扰动作用下，微塑料可以迅速被转移到更深层次的沉积物中（沉积物表层以下6-8 cm处）。仔细分析生物扰动对微塑料迁移的过程及机制可以发现，蛤仔的掘穴、移动及摄食等行为均会对微塑料的垂直迁移产生影响。结果表明，在菲律宾蛤仔未受到微塑料暴露的胁迫性影响时，其生物扰动行为会促进微塑料在沉积物中的垂向迁移。

  本研究结果表明无论在近海海湾还是在深海中，底栖动物出于对微塑料的摄食作用，成为了微塑料迁移过程中的一个重要储存库，而生物栖息的环境、生物种类、自身的生物学特征及时空变化等因素均会影响生物对微塑料的摄食。今后在分析区域海洋中微塑料的分布时，底栖动物群落这一重要储存库的作用不可忽略；并且在研究微塑料摄食的影响因素及对生态系统或敏感物种的潜在影响时，基于物种水平的多种生物的采样策略更加值得提倡；除此之外，底栖动物在自身行为未受到显著影响时，可以通过生物扰动促进微塑料从沉积物表层到深层的快速迁移，进而改变沉积物中微塑料的分布。

      As emerging pollutants, microplastics (MP) pose a threat to marine life and ecosystems. In recent years, MP pollution has attracted extensive attention from the scientific community and the public. MPs are widely distributed in the marine environment and many studies have reported the MP contamination in seawater, sediments and marine biota. However, the fate of MPs in the ocean is still unclear, and it is important to clarify the transport, sink and fate of MPs to control the pollution. As an important research issues on the distribution and fate of MPs in the marine environment, bio-mediated processes play an important role in the vertical transport of MPs. But there is still a lack of research based on the effects of different types of benthic organisms on the vertical distribution of MPs in sediments. Jiaozhou Bay, which is located in the south of Shandong Peninsula, is a typical semi-enclosed bay offshore China, with more than ten rivers joining along the coast, a high population density, and the ecosystem is seriously affected by human activities. As a typical chemosynthetic ecosystem, the F cold seep in the South China Sea is one of the most active cold seeps in China, and many geological and biological investigations have already been carried out in this area. In this study, two typical sea areas, Jiaozhou Bay and the F cold seep in the South China Sea, which are very differently affected by human activities, were selected as the research objects. This study investigated the MP contamination in benthic communities and explored the roles of benthic organisms on the vertical transport of MPs and the mechanisms through bioturbation activities based on field surveys and laboratory experiments. The main conclusions are as follows:

   To explore the MP contamination in typical benthic organisms in Jiaozhou Bay, two economically important species, oyster (Crassostrea gigas) and clam (Ruditapes philippinarum), were selected in this study. Samples were collected in December 2018 and March 2019, and the steps of biological treatment, alkaline digestion, filtration and separation, identification and statistical analysis were carried out sequentially. The occurrence of MPs by the same species in Jiaozhou Bay under both wild and farmed conditions was reported and compared for the first time. The MP abundance of shellfish in Jiaozhou Bay ranged from 0.16 to12.09 items/g (soft tissue wet weight) or 1-9 items/ind. The average abundance of MPs in both shellfish was 1.21 items/g (or 2.17 items/ind.), of which the average abundance in clams was 1.51 items/g (or 2 items/ind.), and 0.92 items/g (or 2.34 items/ind.) in oysters. Compared with other regions, MP contamination of shellfish organisms in Jiaozhou Bay was at an intermediate level. Comparison of different species of shellfish revealed that MP levels in clams were significantly higher than those in oysters. Comparison of the same species of shellfish in different growth modes revealed that the effects of both farmed and wild modes on the ingestion of MPs by shellfish were not significant. Most of the MPs in shellfish from Jiaozhou Bay were in the form of fibers (92.97%). The main color was black (42.97%). With 37.5% of the MPs having a size of less than 500 μm, and the number gradually decreased with the increase of size. Cellophane and polyethylene terephthalate dominated the composition of the MPs. The study also extrapolated from the consumption of shellfish diet by Chinese and obtained that the average annual intake through shellfish consumption was about 1.57 × 10³ items per person, and the risk of MP intake was low.

     On the basis of MP contamination of shellfish, to further study the MP load in the benthic community and assess the role of biological sinks, this study collected macrobenthic organisms in Jiaozhou Bay using a grabber dredge in each quarter between December 2018 and September 2019, and analyzed the MP contamination. In this study, the benthos of Jiaozhou Bay were categorized into the following six groups: polychaetes, molluscs, crustaceans, echinoderms, fishes, and others. It was found that, firstly, the average abundance of MPs in all benthos of Jiaozhou Bay was 1.00 ± 0.11 items/ind. (or 15.49 ± 3.49 items/g), and the total MP load was about 36.4 kg, which is a non-negligible in comparison with the MP in the sediments and the atmosphere deposition. Comparison of MPs in different groups in terms of individual organisms showed that fish contained significantly more MPs than other organisms, while comparison in terms of unit mass showed that crustaceans contained the highest abundance of MPs. Secondly, MPs in benthic organisms were mainly characterized by fibers, predominantly black in color, and polyethylene in composition, with a size of <500 μm. The average size of MPs in all benthic organisms was 1103.4 μm. Thirdly, MP ingestion by benthic organisms is complex, which is regulated by a variety of factors, including biological and environmental factors. The mass of the organisms, the surrounding seawater, and spatial and temporal variations all have an impact on MP ingestion by organisms. MPs are redistributed in the benthic community, i.e., the average abundance of MPs in a taxon within a given area decreases gradually with the increase in the density of organisms.

    Based on the investigation of MP pollution in the benthos of offshore bays, this study investigated the cold seep, which is belong to chemosynthetic ecosystem, in the South China Sea, a remote area less exposed to human activities. The results showed that MPs were occurred in two dominant benthos in the community of cold seeps, namely the mussel (Gigantidas platifrons) and the squat lobster (Shinkaia crosnieri), but the abundance of MPs in the two organisms was not significantly different. The abundance of MPs in these two organisms was 0.13 and 0.17 items/ind., respectively. The results for the deep-sea cold-seep species were lower compared to the coastal benthos in terms of both MP abundance and the ingestion rate. Observation of the surface morphology of MPs in the cold-seep species by scanning electron microscopy revealed that the MPs showed severe abrasion. The main characteristics of MPs in these chemosynthetic symbiosis were that fibrous in shape (62.5%), the main component was polyester (54.2%), most of them were transparent in appearance (45.8%), the average length of the fibrous MPs was 1807 μm, and the average size of the fragmented ones was 483 μm. Due to the high biological density of the cold seep ecosystems, the estimated load of MPs at the site F cold seep in the South China Sea was 86.5 MPs per square meter of benthic organisms (considering only the two dominant species, the mussel and the squat lobster). This result is comparable to the MP load in familiar organisms in the offshore, and much higher than that in the surface seawater of the South China Sea and the location. Therefore, the cold seep ecosystems may play an important role as sinks in the transport of MPs in the regional oceans.

     Based on the common phenomenon of MP ingestion by benthos, the clam (Ruditapes philippinarum) was selected in this study to simulate the transportation of polystyrene (PS) microbeads (size in 200 μm) in sediments under the effect of bioturbation of clam in the laboratory. The results of the study showed that exposed to environmental concentration-related PS MPs, the clams presented a prolonged acclimatization time, but the subsequent burrowing behavior (including burrowing rate and burrowing velocity) was not affected. After 14 days of MP exposure, clams showed no significant coercive effects on conditioning index, clearance rate, or oxygen consumption rate. Under the effect of bioturbation, MPs can be rapidly transported to deeper levels of sediment (6-8 cm below the sediment surface). The mechanism of bioturbation on MP transport was obtained through careful analysis, and burrowing, movement and feeding behaviors of clam could all affect the vertical transport of MPs. The results suggest that when organisms are not subjected to the effects of MP exposure, the bioturbation behavior promotes vertical transport of MPs in sediments.

      The results of this study showed that benthos is an important reservoir in the transportation of MPs, both in bays and in deep sea. Factors such as habitat, species, biological characteristics and spatial and temporal variations could all affect MP ingestion by organisms. When analyzing the fate of MPs in the regional oceans in the future, the role of benthic organisms as a reservoir should not be ignored. In addition, when studying the factors of MP ingestion and the potential impacts on ecosystems or sensitive species, it is more worthwhile to advocate the sampling strategy of multiple organisms based on the species level. In addition, when the behavior of benthos is not significantly affected, bioturbation activities can promote the rapid transport of MPs from the surface to the deeper layers of the sediment, altering the distribution of MPs in the sediment.

第1章 绪论  1

1.1 塑料与微塑料污染 1

1.1.1 塑料污染的由来  1

1.1.2 微塑料的定义与来源  2

1.2 微塑料在海洋中的迁移过程  3

1.2.1 侧向迁移     3

1.2.2 垂向迁移     5

1.3 微塑料在海洋中的分布 7

1.3.1 海水中的微塑料分布与含量      7

1.3.2 海洋生物体内的微塑料含量      7

1.3.3 沉积物中的微塑料污染现状      12

1.4 微塑料的生态效应 12

1.4.1 微塑料对海洋生物的影响  15

1.4.2 微塑料对海洋生态系统的影响   16

1.5 研究目的、意义及研究内容  16

1.5.1 目的与意义  16

1.5.2 研究内容与技术路线  17

第2章 胶州湾贝类在不同生长方式下的微塑料污染特征      19

2.1 前言 19

2.2 材料与方法     19

2.2.1 贝类生物样品采集      19

2.2.2 微塑料获取和鉴定      20

2.2.3 质量控制     21

2.2.4 数据分析与统计  21

2.3 结果 21

2.3.1 贝类的生物特征与微塑料的摄入情况      21

2.3.2 贝类体内微塑料的化学成分      22

2.3.3 贝类体内微塑料的颜色      22

2.3.4 贝类体内微塑料的形状      22

2.3.5 贝类体内的微塑料尺寸      24

2.4 讨论 25

2.4.1 微塑料在不同贝类生物体内的丰度   25

2.4.2 微塑料在贝类生物体内的特征   27

2.4.3 贝类饮食的风险评估  29

2.5 小结 29

第3章 胶州湾底栖动物体内的微塑料赋存量及特征      30

3.1 前言 30

3.2 材料与方法     31

3.2.1 研究海区介绍      31

3.2.2 样品采集     31

3.2.3 生物体内的微塑料获取      32

3.2.4 微塑料鉴定  32

3.2.5 质量保证和质量控制  33

3.2.6 数据分析     33

3.3 结果 35

3.3.1 胶州湾底栖动物体内的微塑料丰度及特征      35

3.3.2 胶州湾底栖动物摄入微塑料的影响因素   40

3.3.3 胶州湾底栖动物的微塑料总赋存量估算   45

3.4 讨论 48

3.4.1 底栖动物体内的微塑料污染      48

3.4.2 生物摄入微塑料的影响因素      49

3.4.3 底栖生态系统的微塑料赋存量及季节变化      51

3.5 小结 52

第4章 南海冷泉底栖动物体内的微塑料赋存量及特征   53

4.1 前言 53

4.2 材料与方法     54

4.2.1 样品采集     54

4.2.2 生物体内的微塑料获取及特征分析   55

4.2.3 质量控制和质量保证  55

4.2.4 数据分析     55

4.3 结果 56

4.3.1 微塑料丰度  56

4.3.2 微塑料特征  56

4.3.3 南海冷泉底栖动物中的微塑料赋存量      58

4.4 讨论 58

4.4.1 冷泉底栖动物中的微塑料丰度   58

4.4.2 冷泉底栖动物中的微塑料特征   59

4.4.3 研究意义     60

4.5 小结 61

第5章 菲律宾蛤仔对沉积物中微塑料的迁移作用研究   62

5.1 前言 62

5.2 材料与方法     63

5.2.1 实验材料及准备  63

5.2.2 实验设计     64

5.2.3 微塑料暴露的生物学效应测定   64

5.2.4 沉积物分析  67

5.2.5 数据分析     68

5.3 结果 68

5.3.1 胶州湾沉积物中的微塑料污染   68

5.3.2 生物扰动作用下沉积物中微塑料的垂直分布   68

5.3.3 微塑料暴露下菲律宾蛤仔的生物响应      69

5.4 讨论 71

5.4.1 微塑料暴露对菲律宾蛤仔的影响      71

5.4.2 菲律宾蛤仔对沉积物中微塑料分布的影响机制      72

5.4.3 生物对微塑料迁移的作用  73

5.5 小结 74

第6章 结论与展望      75

6.1 主要结论 75

6.2 本研究的创新点     76

6.3 展望 76

参考文献       78

致  谢   101

作者简历及攻读学位期间发表的学术论文与其他相关学术成果    103