【作者】 于婷婷；

【导师】 徐奎栋； 黄勇；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋生物学， 2014， 博士

【摘要】 于黄海冬季（2009年12月）和长江口及邻近海域盛夏（2012年7月）与秋末（2009年11月和2012年11月）采集了76个站位的沉积物样品，研究了小型底栖动物的类群组成、丰度、生物量和分布及其与沉积环境因子的关系；对2012年7月长江口及邻近海域12个站位的线虫进行了群落结构、多样性和分类学研究；对北黄海和长江口及邻近海域线虫的个体平均干重进行了估算。在北黄海和长江口及邻近海域，通过对总计1594条线虫样本的实测分析，利用体积换算法，估算得出北黄海冬季线虫个体干重的平均值为0.1960.140μg/ind，长江口及邻近海域在秋末和盛夏季节线虫个体干重的平均值分别为0.213μg/ind和0.214μg/ind。其中，线虫个体干重的最大值是最小值的1270倍。造成各站位线虫个体干重差异的主要因素是线虫的种类组成和幼体所占比例不同。由此，在利用31μm孔径网筛分选时，我国目前普遍使用的0.4μg/ind经验系数估算的线虫生物量将比实测值高一倍。因此，对线虫生物量的估计当以实测为最佳，如采用经验系数则建议采用0.2μg/ind进行估算。2009年12月黄海海域28个站位的小型底栖动物平均丰度和生物量分别为(1281±1020) ind/10cm2和(492±507) μg dwt/10cm2，整体上呈北高南低，近岸高外海低的分布特点。其中，北黄海4个站位小型底栖动物的平均丰度为(2878±1279) ind/10cm2；南黄海24个站位小型底栖动物的平均丰度为(1014±667)ind/10cm2。线虫是丰度(93.2%)和生物量(48.5%)上的最优势类群。垂直分布上，占总量70.8%的小型底栖动物和线虫分布于沉积物02cm表层。Spearman相关分析表明，小型底栖动物丰度与中值粒径、粉砂-粘土含量、水深和底层水盐度呈显著负相关。BIOENV分析显示与小型底栖动物类群组成和丰度相关性最高的环境因子组合为中值粒径、粉砂-粘土含量、叶绿素a含量和有机质含量。综合已有数据来看，黄海小型底栖动物冬季的丰度仅约为夏季的2/3，且同一季节数量上大致呈北高南低，近岸高于外海的分布特点。2009年11月（19站）和2012年11月（13站）两个航次中，长江口及邻近海域小型底栖动物丰度的分布整体上北高南低，近岸高外海低。受长江冲淡水的影响，河口群落小型底栖动物的丰度较高，两个航次分别为(1716±699)ind/10cm2和(1360±578) ind/10cm2。相比之下，东海离岸海域小型底栖动物的丰度较低，在2009年航次中仅为(509±234) ind/10cm2，不到同一航次河口群落的三分之一。两个航次中小型底栖动物丰度上的最优势类群均为线虫(分别占94.4%和94.3%)，生物量上的最优势类群分别为线虫（2009年航次，占51.6%）和多毛类（2012年航次，占56.5%）。垂直分布上，两个航次中占总量70.8%和73.4%的小型底栖动物分布于02cm表层。对2009年航次的Spearman相关分析表明，小型底栖动物丰度与叶绿素a含量呈显著正相关，与水深、底温和底盐呈显著负相关；BIOENV分析显示与小型底栖动物类群组成和丰度相关性最高的环境因子组合为水深和脱镁叶绿素a含量。对2012年航次的BIOENV分析显示与小型底栖动物类群组成和丰度相关性最高的环境因子组合为叶绿素a含量和有机质含量。该结果表明，影响两个年度小型底栖动物数量分布的环境因子并不相同。2012年7月长江口及邻近海域16个站位小型底栖动物的平均丰度和生物量分别为(1203±191) ind/10cm2和(496±152) μg dwt/10cm2，略低于自该海域11月两个航次的研究结果。线虫是丰度(94.1%)和生物量(45.6%)上的最优势类群。垂直分布上，占总量78.9%的小型底栖动物和76.2%线虫分布于沉积物02cm表层。近年来该海域小型底栖动物和线虫丰度在0-2cm表层中的比例逐渐升高，反映出环境恶化和底层缺氧的逐年加剧。Spearman相关分析表明，小型底栖动物的生物量、桡足类和涡虫类的丰度均与沉积物中的有机氮含量呈显著负相关。BIOENV分析显示与小型底栖动物类群组成和丰度相关性最高的环境因子组合为中值粒径和有机氮含量。该海域7月份小型底栖动物的丰度自长江口往东先增加后降低，至约40-45m等深线处达到最高，后随水深增加而降低的特点。这与该海域秋末小型底栖动物丰度的分布趋势有所不同，可能与长江冲淡水流向的季节变化有关。对2009年11月、2012年7月和11月三个航次的相关分析显示，底层水盐度、粉砂-粘土含量和沉积物中的叶绿素a含量是小型底栖动物丰度季节和年际变化的主要影响因子。2012年7月自长江口及邻近海域12个站位检获的线虫平均丰度为(1133±178) ind/10cm2，共鉴定出线虫430种，隶属于119属、24科、4目。其中，发现并描述了1个新属和5个新种：Paraelzalia gen. nov., Paraelzalia longiseta sp.nov., Paramonohystera sinica sp. nov., Linhystera breviapophysis sp. nov.,Linhystera longiapophysis sp. nov.和Trochamus falciformis sp. nov.。该航次线虫群落的主要优势种是Dorylaimopsis rabalaisi, Quadricoma sp.1, Sabatieria sp.1,Chromadorita sp.1, Prochromadorella sp.1, Daptonema sp.2, Parodontophora sp.3,Daptonema sp.7, Diplopeltoides sp.1和Microlaimus sp.1等。在摄食类型上，沉积食性者（1A+1B）占优势（物种数占58.8%，个体数占56.0%）；幼体占线虫总数的41.5%；雌雄比平均为1:1.17。聚类分析显示，该海域夏季沉积物中的线虫可划分为两个群落：河口群落和近海群落。两群落的线虫丰度接近，分别为(1161±185) ind/10cm2和(1103±163) ind/10cm2；但SIMPER分析显示，群落间线虫的种类组成差异显著。两群落在摄食类型上的差异表现为近海群落的非选择性沉积食性者数量高达河口群落的2.4倍，沉积物中脱镁叶绿素a含量的不同可以合理解释此现象。线虫群落多样性指数的分布与丰度类似，整体上北高南低，近岸高外海低；自长江口往东先增加后降低，至约40-45m等深线处达到最高值。Spearman相关分析显示，该海域线虫的多样性与底层水盐度呈显著正相关，即长江冲淡水是影响线虫多样性分布的根源所在。BIOENV分析显示，底层水温度、水深、脱镁叶绿素a含量和有机质含量的组合是对该海域线虫群落种类组成和多样性的最佳解释。更多还原

【Abstract】 Sediment samples were collected from76stations in the Yellow Sea inDecember2009and in the Yangtze Estuary and its adjacent sea waters (East ChinaSea) in November2009and July and December2012for the analyses of thecommunity structure and distribution of meiobenthos in relation to benthicenvironmental parameters. Based on three cruises, the taxonomy and diversity ofnematodes were studied using samples collected from twelve stations in the YangtzeEstuary and its adjacent waters in July. The average individual dry weights ofnematodes in the northern Yellow Sea and the Yangtze Estuary and its adjacentwaters were estimated.Based on the size measurement of a total of1594nematode samples, weobtained the average nematode individual dry weight of0.196μg/ind in the northernYellow Sea in December, and of0.213μg/ind and0.214μg/ind in the YangtzeEstuary and its adjacent waters in November and July, respectively, with themaximum value about1270times of the minimum. The species composition andjuvenile proportion are the main factors regulating the variability of the averageindividual dry weight of nematodes among stations. Accordingly, calculation usingthe simple0.4μg/ind will overestimate the actual biomass of nematodes to about onetime higher than that of direct measurements when meiobenthos as well asnematodes were sorted with a31μm sieve. For better estimation of nematodebiomass, it is suggested to calculate nematode biomass by direct measurement, whilesimple estimation using0.2μg/ind rather than0.4μg/ind is practical for theestimation of nematodes in this sea area.The average abundance of meiobenthos was (1281±1020) ind/10cm2at28stations in the Yellow Sea in December2009, and the biomass was (492±507) μgdwt/10cm2. There was an overall trend in both the abundance and biomassdecreasing from the north to the south and from the inshore to the offshore. The average abundance of meiobenthos was (2878±1279) ind/10cm2at four stations inthe northern Yellow Sea, and was (1014±667) ind/10cm2at24stations in thesouthern Yellow Sea. Among the12meiobenthos groups identified, Nematoda wasthe most abundant group, accounting for93.2%of the total abundance. In terms ofbiomass, nematodes accounted for48.5%. There were about70.8%of the totalmeiobenthos individuals as well as nematodes distributed in the surface0-2cm layer.Spearman correlation analysis showed that meiobenthos abundance was negativelycorrelated with median grain size and silt-clay content of the sediment, water depthand bottom water temperature. BIOENV analysis suggested that the combination ofenvironmental variables that best correlated with meiobenthos community consistsof median grain size, chlorophyll-a concentration, and silt-clay and organic mattercontent of the sediment. Considering all the available data obtained from the YellowSea, we came to the conclusion that: the abundances of meiobenthos in the YellowSea in winter is only about two thirds of those from the same sea area in summer;and there is an overall trend decreasing from the north to the south and from theinshore to the offshore in the same season, the value in the south Yellow Sea is lessthan half of that in the north Yellow Sea.As regards to the samples collected from19stations in November2009and13stations in November2012in the Yangtze Estuary and its adjacent waters, there wasalso an overall trend in both the abundance and biomass decreasing from the north tothe south and from the inshore to the offshore. Due to the influence of the Yangtzediluted water, the abundance of meiobenthos was high in the estuarine community,with the value of (1716±699) ind/10cm2in November2009and (1360±578)ind/10cm2in November2012. In contrast, the abundance was much lower in theoffshore sea areas, with the value of merely (509±234) ind/10cm2in November2009, only about two thirds of the mean abundance detected in the estuarinecommunity. Nematoda was the most abundant group of meiobenthos in both the yearof2009and2012(accounting for94.4%and94.3%, respectively). In terms of biomass, Nematoda was also the most dominant group in2009(accounting for51.6%), while in2012the most dominant group was replaced by Polychaeta(accounting for56.5%). There were on average70.8%and73.4%of the totalmeiobenthos individuals distributed in the surface0-2cm layer. Spearmancorrelation analysis showed that meiobenthos abundance in2009was positivelycorrelated with chlorophyll-a concentration of the sediment and negatively correlatedwith water depth and bottom water salinity and temperature. BIOENV analysissuggested that the combination of environmental variables that best correlated withmeiobenthos community in2009consists of water depth and sediment chlorophyll-aconcentration. BIOENV analysis suggested that the combination of environmentalvariables that best correlated with meiobenthos community in2012consists ofsediment chlorophyll-a concentration and organic matter content. It showed that theenvironmal parameters that influcing the abundance and distribution of meiobenthoswere different between the two years.The average abundance of meiobenthos was (1203±191) ind/10cm2at16stations in the Yangtze Estuary and its adjacent waters in July2012, and the biomasswas (496±152) μg dwt/10cm2, both of which were a little lower than that obtainedin November in the same sea area. Spearman correlation analysis showed thatbottom water salinity, silt-clay content and chlorophyll-a concentration of thesediment were the main factors regulating the variation of meiobenthos abundance.Nematoda was the most dominant group in both abundance (94.1%) and biomass(45.6%). There were about78.9%of the total meiobenthos individuals and76.2%ofthe nematodes distributed in the surface0-2cm layer. Generally, our study revealeda tendency of the meiobenthos congregating from the lower to the upper0-2cmsediment layer within the study areaover the past ten years, to some extent indicatingan increasing year by year degraded and anoxic benthic environment. Spearmancorrelation analysis showed that both the biomass of meiobenthos and the abundanceof Copepoda and Turbellaria were negatively correlated with organic nitrogen content of the sediment. BIOENV analysis suggested that the combination ofenvironmental variables that best correlated with meiobenthos community consistsof median grain size, and organic nitrogen content of the sediment. The horizontaldistribution of meiobenthos abundance in July was different from that in November:gradually increasing from the Yangtze Estuary to the eastern sea areas, reaching thehighest value at about40-45m depth contour, and then decreasing with the raisingof water depth. The difference might result from the seasonal change in the directionof Changjiang Diluted Water.The average abundance of nematodes was (1133±178) ind/10cm2at12stations in the Yangtze Estuary and its adjacent waters in July2012. A total of430species belonging to119genera,24families and four orders were identified. Amongthem, one new genus and five new species were discovered and described:Paraelzalia gen. nov., Paraelzalia longiseta sp. nov., Paramonohystera sinica sp.nov., Linhystera breviapophysis sp. nov., Linhystera longiapophysis sp. nov. andTrochamus falciformis sp. nov. The main dominant species were Dorylaimopsisrabalaisi, Quadricoma sp.1, Sabatieria sp.1, Chromadorita sp.1, Prochromadorellasp.1, Daptonema sp.2, Parodontophora sp.3, Daptonema sp.7, Diplopeltoides sp.1and Microlaimus sp.1. Nematode trophic type analysis showed that deposit feeders(1A+1B) were dominant in both species and individual number. Juveniles occupyabout41.5%of the total individuals. At the12stations, the average ratio of thenumber of female to male was1:1.17. CLUSTER analysis showed that thenematodes in this sea area could be classified into two communities: estuarinecommunity and offshore community. As concerns to the average abundance ofnematodes, there was little difference between the two communities, which was(1161±185) ind/10cm2and (1103±163) ind/10cm2, respectively. However, SIMPERanalysis showed much difference in the species composition of nematodes betweenthe two communities. From the aspect of trophic type, the number of non-selectivedeposite feeders in the offshore community was2.4times of that in the estuarine community, and Phaeophytin-a content of the sediment can explain the differencereasonably. The horizontal distribution of nematode diversity was similar to that ofthe abundance of meiobenthos as well as nematodes. Spearman correlation analysisshowed that the diversity of nematodes was positively correlated with bottom watersalinity, that is to say, Changjiang Diluted Water was the fundamental factor thatinflucing the diversity and distribution of nematodes. BIOENV analysis suggestedthat the combination of environmental variables that best correlated with nematodespecies composition and diversity consists of bottom water temperature, water depthand phaeophytin-a concentration of the sediment.更多还原