渤海表层沉积硅质藻类的分布特征及其环境指示意义 | |
刘丽雪 | |
学位类型 | 硕士 |
导师 | 刘东艳 |
2014-05 | |
学位授予单位 | 中国科学院研究生院 |
学位授予地点 | 北京 |
学位专业 | 环境科学 |
关键词 | 渤海 沉积物 硅藻 环境因子 |
摘要 | 本文研究区域为莱州湾、渤海中部及邻近海域,于2009年和2011年6月、8月采取了研究区域63个表层沉积物样品,分析鉴定了表层沉积物中藻类物种组成、生态组合和分布特征,并通过主成分分析和优势物种组成结构探讨了不同藻类组合对环境的指示意义,并筛选出指示物种。同时,于2012年5月和11月,对调查海域32个站点水样的温盐、营养盐和叶绿素a的分布特征进行了研究,并结合历史数据与沉积物藻类分布特征开展了对比研究。研究结果解释了上层水体数据与沉积物数据的差异及其形成原因,对于客观认识渤海沉积藻类的古环境反演意义和环境指示应用具有重要意义。 表层沉积物中藻类的分类鉴定结果表明,研究区域共发现藻类162种,其中硅藻为160种(包括未定种、变种及变型等),硅鞭藻为2种。最优势种为具槽帕拉藻和柱状小环藻,所占比例达整个研究区域的50%以上。调查区域硅藻丰度值从高到低依次为渤海海峡附近海域、渤海中部海域、莱州湾;而物种多样性指数值分布趋势与丰度正好相反,从高到低为莱州湾、渤海中部海域、渤海海峡附近海域。对研究区域表层沉积硅质藻类进行主成分分析,可将研究站点分为三个组合:组合Ⅰ渤海海峡附近海域,主要特征为高丰度值低物种多样性,优势种主要是具槽帕拉藻;组合Ⅱ渤海中部,丰度值和物种多样性均介于组合Ⅰ和组合Ⅲ之间,具槽帕拉藻、柱状小环藻、离心列海链藻是该组合最多的三种藻;组合Ⅲ莱州湾特征为低物种丰度高物种多样性,优势种主要为柱状小环藻。整个调查区域沉积物主要组成为粉砂,砂和粘土含量相对较少。不同组合沉积物粒径组成差异较小。沉积物粒径与物种的丰度和多样性指数进行相关性分析表明粒径不能显著影响丰度和多样性的分布。 水样中温盐、营养盐和叶绿素a测定结果表明:春季,调查海域水温为近岸高深水区低,低盐区为黄河口附近海域。营养盐浓度在空间分布上表现为黄河口附近海域较高,在垂直分布上表现为中、底层高于表层,显示出黄河水输入与沉积物营养盐再释放的影响。营养盐浓度与结构显示渤海海域存在明显的磷和硅限制,磷限制尤其严重。表层叶绿素a浓度的高值区出现在渤海湾湾口处,而中层与底层的叶绿素a浓度高值区出现在渤海中部。主成分分析结果表明,磷酸盐和温度是影响春季叶绿素a浓度的重要因素。秋季,调查海域水温为深水区高近岸低,盐度高值位于渤海海峡附近海域。可溶性无机氮高值区位于黄河口附近海域,而磷酸盐和硅酸盐高值区则位于辽东湾口处,可能原因为三种营养盐的主要来源有差异,营养盐的垂直差异较小。营养盐结构表明调查海域营养盐限制并不明显。叶绿素a浓度在三层水体中的高值均出现在渤海湾口北部和渤海中部偏东南处。主成分分析结果表明可溶性无机氮浓度与秋季叶绿素a浓度分布相关性较大。对比春季和秋季水样分析结果发现,春季水温分布与秋季相反,盐度分布类似,明显受黄河淡水和黄海外海水影响。秋季营养盐浓度整体高于春季,并且三层水体营养盐分布类似,而春季表、中、底层水体营养盐存在明显差异。春季调查海域存在明显磷和硅限制现象,但秋季无明显的营养盐限制作用。春季叶绿素a浓度整体高于秋季,并且中、底层高于表层,而秋季整体较低并无明显垂直差异。春季磷酸盐和温度是影响叶绿素a浓度的主要因素,而秋季则为可溶性无机氮。 沉积藻类空间分布与不同环境因子比较发现,沉积速率对沉积藻类的丰度具有明显影响,而营养盐浓度、叶绿素a浓度与沉积藻类丰度分布特征无明显的相关关系。对比沉积物中硅藻物种组成与上层水体中硅藻优势种组成发现,角毛藻、中肋骨条藻等这类硅藻并没有在沉积物中发现,而沉积物中的优势种如柱状小环藻、蜂腰双壁藻等没有在水体中被记载。前者原因为这类硅藻硅质化弱而无法完善的保存于沉积物中,而后者主要是一些底栖硅藻和小型硅藻。莱州湾靠近岸,受人类干扰较多,盐度梯度和营养盐水平差异大,可能是莱州湾物种多样性高于渤海中部和渤海海峡的主要原因。此外,莱州湾表层沉积藻类中也存在一些淡水种和半咸水种,此类物种的出现对应于黄河淡水输入对物种组成的影响。根据不同藻类相对丰度特殊的分布特征,具槽帕拉藻和星形柄链藻可定为渤海的近海指示种,柱状小环藻和小等次硅鞭藻可作为近岸指示种,这些指示种可以应用于渤海沉积藻类的古环境研究中。 |
其他摘要 | In this thesis, the Laizhou Bay and the central Bohai Sea were major studied areas. Diatoms composition and distribution of 63 surface sediment samples in the studied area were identified. Based on results of principal component analysis and composition of dominant speices, three groups were classified and 4 species were found to be the special speices to indicate environmental feature. Comparably, distribution of nutrients and chlorophyll a (Chl-a) of 32 water samples in the studied area in spring and autumn were also analyzed. Comparision between sediment diatoms composition, distribution and phytoplankton compositon, distribution of Chl-a and other environmental factors in the upper waters were carried. These results explained the differences between diatoms in surface sediment and that in upper waters and contribute some basic materials for the application of sediment diatoms in paleoenvironmental reconstruction. Totally, 160 taxa were discovered, which included 2 silicoflagellate and 133 species, 41 genera of diatoms. Paralia sulcata and Cyclotella stylorum were the most dominant species and their relative abundance exceeded 50% in all samples. Absolute abundance of samples around the Bohai Strait was highest, and that in the Laizhou Bay was lowest. But species diversity index distribution was diiferent from absolute abundance and the maximum index was in the Laizhou Bay. Principal component analysis was carried on the surface sediment diatoms composition, and the samples can be classified into three groups: Group Ⅰ was located in sea areas near the Bohai Strait, which had a high abundance and low species diversity index. The most dominant speices in Group Ⅰ was Paralia sulcata. Group Ⅱ was located in the central Bohai Sea and its abundance and species were between Group Ⅰ and Group Ⅲ. The most dominant species in Group Ⅱ were Paralia sulcata, Cyclotella stylorum, and Thalassiosira eccentrica. Group Ⅲ was located in the Laizhou Bay with lower abundance and higher species diversity index. There were many dominant species in Group Ⅲ and the most was Cyclotella stylorum. Compositon of sediment grain size in studied area was fit for preservation of fossils. There was little difference of sediment grain size in three groups. Correlation analysis between sediment grain size and abundance, species diversity index showed that sediment grain size had no significantly effect on distribution of abundance and species diversity index. Temperature, salinity, nutrients and Chl-a of water samples were measured. In spring, results showed that sea water temperature was high along nearshore areas but low in the central Bohai Sea. Salinity was low in the sea near the Yellow River. There was a high nutrients concentration in the Yellow River estuary and nutrients concentrations were higer in middle and bottom layer than that in surface layer. Phosphate limitation was also found according to nutrient structures. Concentrations of Chl-a were higher in the Bohai Bay mouth in surface layer but higher in the central Bohai Sea in middle and bottom layers. The results of principal components analysis indicated that phosphate and temperature were major factors controlling the spatial distribution of Chl-a concentrations in surface water layer, and phosphate was key factor in the middle and bottom water layers. In autumn, water temperature was low in nerashore areas but high in offshore. Salinity was high in the sea near the Bohai Strait. Dissolved inorganic nitrogen concentrations occurred to be high around the Yellow River, but phosphate and silicate concentrations were higher at the mouth of the Liaodong Bay. Nutrients structure showed that there was no obvious nutirents limitation. Chl-a concentrations were higher at the north Bohai Bay mouth and the southeast central Bohai Sea. The results of principal components analysis indicated that dissolved inorganic nitrogen was major factor controlling the spatial distribution of Chl-a concentrations. Comparison between Chl-a and other environmental factors concentrations in spring and autumn were carried out. Results showed that water temperature distribution was opposite. Salinity distribution was same but salinity gradient was higher in autumn. Nutrienrs concentrations were higher in autumn than that in spring, and phosphate limitation was weaker in autumn than that in spring. Chl-a concentrations was lower and there is no stratification phenomenon in autumn. The major factors controlling spatial distribution of Chl-a concentrations were also different as a result of principle components analysis. Relationship between abundance of sediment diatoms and different environmental factors of upper water were analyzed. It turned out that abundance of sediment diatoms had less direct relationship with concentrations of nutrients and chl-a, but had significant negative correlation with deposition rates. Due to mass fresh water input, much freshwater and brackish species emerged in studied area. Dominant species in sediment and upper waters were compared to detect their differences. We found that some species such as Chaetoceros spp., Skeletonema costatum et al. were hardly found in sediments but some like Cyclotella stylorum, Diploneis bombus were hardly recorded in upper waters. These were because species like Chaetoceros spp. could not be saved in sediments for their weak frustules and species like Cyclotella stylorum were mostly benthon. For these reasons, such special species needed careful consideration when the sediment diatoms were applied to indicate phytoplankton in upper waters. Based on relative abundance distribution of different species, four species were found to be indicator species in the studied area. Paralia sulcata and Podosira stelliger could be the offshore species in the Bohai Sea. Cyclotella stylorum and Dictyocha fibula could be the nearshore species. All these indicator species could be applied in paleoenvironment studies. |
文献类型 | 学位论文 |
条目标识符 | http://ir.yic.ac.cn/handle/133337/6808 |
专题 | 中国科学院烟台海岸带研究所知识产出_学位论文 |
推荐引用方式 GB/T 7714 | 刘丽雪. 渤海表层沉积硅质藻类的分布特征及其环境指示意义[D]. 北京. 中国科学院研究生院,2014. |
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