黄海微型和小型底栖生物群落结构与时空分布

	黄海微型和小型底栖生物群落结构与时空分布
	周百灵1,2
学位类型	博士
导师	徐奎栋
	2015-06-02
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	海洋生物学
关键词	微型底栖生物小型底栖生物纤毛虫浒苔暴发水母暴发黄海
摘要	微型底栖生物主要包括原核微生物、真核微藻及原生动物等类群，小型底栖生物主要包括线虫、多毛类、桡足类等后生动物类群，微型和小型底栖生物组成了底栖微/小食物网，在物质循环和能量流动中起着重要作用。但由于对微型底栖生物定量提取和定性分析存在方法上的障碍，微型底栖生物又具有功能和形态上的复杂性，所以目前对微型底栖生物的研究远落后于对微小型浮游生物的研究，且已有相关研究主要集中在河口和潮间带生境，对陆架海研究极少。本研究所关注的黄海海域近年来遭受了浒苔暴发和水母暴发，已有研究表明浒苔暴发对生态系统可以产生正面或负面影响，水母在死亡后会沉降到海底降解，目前缺乏对微型和小型底栖生物在这两种生态灾害发生时和发生之后的研究。本论文结合底栖环境因子，使用DAPI荧光计数法和Ludox-QPS方法，对2010、2011年7月和11月采自黄海的微型和小型底栖生物的分布、群落结构及多样性进行了研究，并探讨了微型和小型底栖生物对浒苔和水母暴发的响应。 0‒5 cm沉积物中，细菌丰度(10⁸cells/cm³)较蓝细菌(10⁵‒10⁶ cells/cm³)、自养微型鞭毛虫(PNFs，10⁶ cells/cm³)、异养微型鞭毛虫(HNFs，10⁵‒10⁶ cells/cm³)的丰度高2‒3个数量级，远高于硅藻、异养小型鞭毛虫(HMFs)和纤毛虫的丰度。生物量上，细菌同样是最优势类群，PNFs和HNFs生物量与细菌同数量级或低1个数量级，蓝细菌生物量较细菌低1个数量级。小型底栖生物的丰度远低于pico-(细菌、蓝细菌)和nano-级(PNFs和HNFs)底栖生物，低于硅藻的丰度，高于HMFs和纤毛虫的丰度。小型底栖生物的生物量同样远低于细菌、PNFs和HNFs，与蓝细菌生物量接近，高于其余微型底栖生物类群。与通常分布规律不同，2011年7月有浒苔堆积和沉降的近岸海域沉积物中值粒径减小，粉砂‒粘土含量增高，这样近岸沉积物颗粒大小就与南黄海中心接近；而在2010年7月，在同样有浒苔暴发的近岸海域，沉积物颗粒仍较粗，粉砂‒粘土含量仍较低，与通常分布规律接近。以上结果表明两年浒苔暴发对沉积环境影响不同。 2010年采集的生物样品因放置时间较长，可能存在低估，所以仅将2010年的生物数据做为背景资料。2011年夏季浒苔暴发和水母暴发均有发生，所以重点对2011年两个航次的数据进行分析。 2011年7月，在浒苔堆积和沉降的山东半岛南部近岸海域，蓝细菌和PNFs的数量均较低，与没有浒苔暴发的2007年6月的分布不同；硅藻虽在青岛近岸海域有高值区，但7月份南黄海硅藻丰度平均值均明显低于2007年6月。以上结果表明浒苔暴发抑制了沉积物中自养生物的生长。另一方面，2011年7月，异养的细菌、HNFs和纤毛虫的数量在山东半岛南部近岸海域较高，离岸海域较低，这与2007年6月这三者在南黄海近岸和中心海域均有较高数量不同。浒苔在近岸的堆积和降解对沉积物中微生物降解过程和碎屑食物网有促进作用，从而促进了细菌的生长。HNFs和纤毛虫作为细菌的捕食者，纤毛虫同时也是HNFs的捕食者，通过级联效应使数量增加。 2011年7月，小型底栖生物的分布规律与没有浒苔暴发的2007年6月一致，均在近岸海域有高的现存量，在离岸海域现存量较低。2011年7月南黄海小型底栖生物平均丰度高于没有浒苔暴发的2007年6月，山东半岛南部近岸海域的叶绿素a含量高，可能充足的食物保障了小型底栖生物的生长。另外，本论文使用的Ludox-QPS方法较离心分选法能获得更高的丰度，可能是造成2011年7月小型底栖生物丰度较2007年6月增加的另一个原因。通常，夏季南黄海的纤毛虫丰度和生物量均明显低于北黄海，而在2011年7月，南黄海纤毛虫平均生物量仍低于北黄海，但南黄海纤毛虫的平均丰度高于北黄海，表明有浒苔暴发2011年7月份南黄海小个体菌食性纤毛虫成为优势类群。2011年7月小个体的菌食性纤毛虫，例如中圆虫(Metacystis spp.)，游仆虫(Euplotes spp.)和盾纤类，其丰度和生物量在全部纤毛虫中的比例较2007年6月增加，菌食性纤毛虫比例增加可能是对浒苔沉降和降解的响应。虽然T检验未发现显著差异，2011年11月份南黄海沉积物中的总氮含量平均值较同年7月份和2010年11月份均增加了22%，可能是水母降解释放到沉积物中的。2011年11月南黄海PNFs生物量平均值较同年7月份增加了17%。在夏季未发生水母暴发的2010年，11月南黄海PNFs生物量平均值较同年7月下降16%。通过两年11月份数据的对比，可以推测水母降解过程释放营养物质到沉积物中，并从而促进了PNFs的生长。在夏季水母大量出现的山东半岛南部离岸海域和长江口附近海域，2011年11月份细菌、PNFs、HNFs和纤毛虫的数量均较多，与夏季没有水母暴发的2010年11月份的分布不同。与浒苔降解过程相似，水母降解同样可以促进底栖碎屑食物网的发展，但细菌生物量较7月份下降，细菌的低生物量可能主要是由于大量增加的HNFs对其的捕食压力造成的。与2011年7月份相比，2011年11月份底栖PNFs、HNFs和纤毛虫均增加，但小型底栖生物却减少。这可能是因为11月份叶绿素a含量的减少，叶绿素a含量通常可代表小型底栖生物的食物来源。与2007年6月一致，2011年两个月份肉食性纤毛虫生物量和物种数均最多，是最主要的摄食类型，然后依次为菌食性、藻食性和杂食性。此外，前口类和核残迹类均是生物量最多的类群。和2011年7月相比，11月份肉食性纤毛虫生物量所占比例升高，而菌食性纤毛虫所占比例下降。肉食性纤毛虫比例增加大部分是因为典型肉食性的钩刺类纤毛虫的增多，这样11月份肉食性纤毛虫在所有站位均是最主要的摄食类型。浒苔暴发和水母暴发的后续效应使HNFs增多，肉食性纤毛虫的增多可能是对沉积物中HNFs增多的响应。 2011年7月南黄海异养鞭毛虫对生物量和新陈代谢率的相对贡献较2007年6月增加，而小型底栖生物的相对贡献降低。2011年11月份南黄海异养鞭毛虫对生物量和新陈代谢率的相对贡献又较2011年7月增加，小型底栖生物的相对贡献更低。相对新陈代谢率在冷水团海域和北黄海表现出相近的变化趋势，冷水团外围海域和南黄海变化趋势接近。这些结果表明浒苔暴发和水母暴发使冷水团外围海域和南黄海的底栖消费者向小个体转变，并且使底栖生物群落结构和新陈代谢从自养向异养转变。南黄海和长江口这样的异养环境有助于水母的发生，微型和小型底栖生物在这些海域的积累为水母水螅体提供了充足的食物，可能因此促进了2012年水母的暴发。
其他摘要	The microbenthos mainly consist of unicellular prokaryotes, eukaryotic microalgae and protozoa. Meiobenthos usually refer to those small benthic metazoans, such as nematodes, polychaetes, and copepods. Micro- and meiobenthos are regarded as one complex, which is referred to as the benthic microbial food web, and play an important role in the energy flow from primary producers to higher trophic levels. However, because of methodological difficulties in the quantitative extraction of these fragile organisms from sediments and qualitative analysis, as well as the complex functions and forms of microbenthos, studies of microbenthos are scant and are mainly concentrated in intertidal habitat. Few studies concern the sediments in the shelf sea. This study focus on the Yellow Sea, which has suffered the green macroalgal Ulva prolifera and giant jellyfish Nemopilema nomurai blooms in recent years. Previous studies indicate the macroalgal bloom could have positive or negative effects on the ecosystem. The giant jellyfish sink to the seafloor and decompose after death. However, the patterns of micro- and meiobenthos during and after these events have never been evaluated. In combination with analyses of benthic environmental factors, using epifluorescence microscopy and the Ludox-QPS method, we investigated the distribution, community composition and diversity of micro- and meiobenthos in the sediments from the Yellow Sea in July and November of 2010 and 2011. The responses of micro- and meiobenthos to the blooms were also discussed. In the 0‒5 cm sediments, the abundance of bacteria (10⁸ cells/cm³) was about 2‒3 orders of magnitude higher than that of cyanobacteria (10⁵‒10⁶ cells/cm³), phototrophic (PNFs, 10⁶ cells/cm³) and heterotrophic nanoflagellates (HNFs, 10⁵–10⁶ cells/cm³), and was much higher than those of diatoms, heterotrophic microflagellates (HMFs) and ciliates. Bacteria was also dominant in biomass. The biomass of PNFs and HNFs were in the same order or 1 order of magnitude lower than bacterial biomass. The meiobenthic abundance was far lower than those of pico- (bacteria and cyanobacteria) and nano- sized (PNFs and HNFs) benthos, and also lower than abundance of diatoms, but higher than those of HMFs and ciliates. The meibenthic biomss was also much lower than those of bacteria, PNFs and HNFs, close to that of cyanobacteria, and higher than other microbenthos. The samples collected in 2010 were placed for a long time before analyzed, which might lead to undervalue of the organisms. So the results in 2010 was regarded as background data. There were green macroalgal and giant jellyfish blooms in the summer 2011, so we mainly focused on the data in 2011. Different from the usual pattern, the median grain size decreased and silt‒clay content increased in July 2011 in the inshore area, where macroalgae accumulated and subsided, thus the sediments in the inshore area became close to that in the central area in the southern Yellow Sea. While in July 2010, in the inshore area where macroalgal bloom also occurred, the sediment particles were still large and the silt‒clay contents were still low, which were similar to the usual pattern. These data indicate the effects of macroalgal bloom on the benthic environment are different in the two years. In July 2011, different from the distribution in June 2007 when no macroalgal bloom happened, the standing crops of cyanobacteria and PNFs were low in the inshore area of the southern Shandong Peninsula where macroalgae accumulated and subsided. Though diatoms had high quantity in the inshore area of Qingdao. The average abundance in the southern Yellow Sea in July 2011 were obviously lower than that in June 2007. These data indicate the macroalgal blooms inhibit the growth of phototrophic organisms in the sediments. On the other side, in July 2011, the standing crops of bacteria, HNFs and ciliates were high in the coastal area near the southern Shandong Peninsula, which were different from their distribution patterns in June 2007. The accumulation and decomposition of macroalgae in the inshore area might stimulate the microbial degradation and detritic trophic webs within the sediments, and induced the growth of bacteria. HNFs and ciliates are the predators of bacteria, and ciliates are also the predators of HNFs, so the quantities of HNFs and ciliates increased by cascade effects. In July 2011, the distribution patterns of meiobenthos were similar to that in June 2007, and standing crops were high in the inshore area and low in the offshore area. The average meiobenthic abundance in the southern Yellow Sea in July 2011 was higher than that in June 2007. The Chl-a concentrations were high in the inshore area in the southern Shandong Peninsula, the enough food might guarantee the growth of meiobenthos. Furthermore, the Ludox-QPS method used in this study could estimate higher abundance than the centrifugation method, which might be another reason for the higher abundance in July 2011 than June 2007. Generally, the abundance and biomass of benthic ciliates were lower in the southern than in northern Yellow Sea. In July 2011, the average biomass was still lower but the average abundance was higher in the southern than in northern Yellow Sea, indicating small sized ciliates became dominant in the southern Yellow Sea in July 2011 when macroalgal bloom happened. Compared with those in June 2007, the proportions of bacterivores, for example, Metacystis spp., Euplotes spp. and scuticociliates, in abundance and biomass increased in July 2011, which might be the response of ciliates to the decomposition of macroalgae. In spite of no significant difference according to the T-test, the average total nitrogen content in the southern Yellow Sea in November 2011 both increased 22% when compared to those in July 2011 and November 2010. The increased total nitrogen content might be the result of the decomposition of jellyfish. The average biomass of PNFs in the southern Yellow Sea increased 17% in November 2011 compared to July 2011. In 2010 when no giant jellyfish blooms in summer, the average biomass in the southern Yellow Sea decreased 16% in November compared to July. According to the data in the two years, the decomposition of jellyfish probably released nutrients to the sediments and thus increase the growth of PNFs in November 2011. In the area off the Shandong Peninsula and Yangtze Estuary where large quantity of jellyfish occurred in summer, the standing crops of bacteria, PNFs, HNFs and ciliates were high in November 2011. The patterns were different from those in November 2010 when no jellyfish occurred in summer. Similar to the decomposition of macroalgae, the decay of jellyfish also could induce the benthic detritic trophic webs. However，the bacterial biomass decreased in November compared to July. The low bacterial biomass was likely due to the increased predation pressure of HNFs, whose biomass was largely increased. Compared to those in July 2011, the quantities of PNFs, HNFs and ciliates were all increased, but that of meiobenthos decreased, This was likely related to the decrease in Chl-a concentrations, an important indicator of primary productivity, which serves as one of the main food supplies of meiobenthos. Consistent with June 2007, the biomass and species numbers of carnivorous ciliates were the most in July and November 2011. Carnivores were the primary feeding type, followed by bacterivores, algivores and omnivores. Prostomateans and karyorelicteans consistently constituted the first and second most important ciliate groups in biomass. Compared to those in July 2011, the proportion of carnivores in biomass increased, but the proportion of bacterivores decreased. The rise in carnivores is largely due to the substantial increase of haptorians, which are typically rapacious ciliates. Thus, carnivorous ciliates constituted the primary trophic type at all stations in November. The increasing dominance of carnivorous ciliates is likely a response to the increase of predominant heterotrophic nanoflagellates in the sediments of the Yellow Sea. The latter situation might be ascribed to the subsequent effects of the green macroalgal and giant jellyfish blooms. Compared to those in June 2007, the relative contributions of heterotrophic flagellates in biomass and metabolic rate increased, but those of meiobenthos decreased. Then the relative contributions of heterotrophic flagellates in biomass and metabolic rate further increased in November 2011, and those of meiobenthos further decreased. The YSCWM and the northern Yellow Sea showed a similar trend in the relative contribution, while the sea area outside the YSCWM and the southern Yellow Sea were similar. The data indicate that the green macroalgal bloom together with the giant jellyfish bloom induced regime shifts in the benthic community structure from larger benthos towards smaller sizes and in benthic metabolism from autotrophic to heterotrophic in the southern Yellow Sea as well as the sea area outside the YSCWM. Such environments may favour the occurrence of the obligatorily rapacious giant jellyfish Nemopilema nomurai in the surroundings of the southern Yellow Sea and Yangtze Estuary, where the giant jellyfish medusae were initially sighted. The accumulation of micro- and meiobenthic biomass in this region may provide a good food supply for the obligatorily carnivorous polyps of Nemopilema nomurai and likely initiate the mass occurrence of giant jellyfish the following year.
学科领域	海洋生物学
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/22791
专题	海洋生物分类与系统演化实验室
作者单位	1.中国科学院海洋研究所 2.中国科学院大学
第一作者单位	中国科学院海洋研究所
推荐引用方式 GB/T 7714	周百灵. 黄海微型和小型底栖生物群落结构与时空分布[D]. 北京. 中国科学院大学,2015.

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