河口是连接陆地和海洋生态系统的重要交错区，由于人类在河流上、中游建造大坝、水渠等蓄水工程，使得河流入海泥沙通量大幅减少，对河口生态系统形成显著影响。本研究基于黄河调水调沙工程，于2013年4月、6月和7月（调水调沙发生）、9月在黄河口海域，以及2014年5月、9月在莱州湾海域，分别开展了6个航次的野外调查工作。收集并检测了温度、盐度、营养盐、叶绿素a以及浮游植物群落结构等参数，利用统计方法分析了浮游植物群落结构以及生物量与环境因子之间的相关关系，对比了调水调沙前后黄河口及其临近海域环境因子的变化，以及浮游植物群落的响应特征。研究结果不仅有助于阐明黄河调水调沙事件对邻近海域浮游植物群落结构的影响，而且可以为保护黄河口及莱州湾生态系统健康提供基础资料与理论依据。
  主要研究结果表明：黄河口海域环境因子的时空变化特征：调水调沙前（4月份），平均温度和盐度分别为8.01°C和26.2，高温低盐分布在黄河口北部海域；营养盐结构分析表明，不存在溶解性无机氮（DIN）限制，但存在溶解性无机磷（DIP）限制和溶解性硅酸盐（DSi）限制。调水调沙后（6、7、9月份），平均海水温度7月份最高（25.2°C），平均盐度值7月份最低（20.8），低盐区域主要出现在邻近河口近岸海域；营养盐结构分析表明，不存在DIN限制，但存在DIP限制，DSi限制只在6月份河口西北部的海域内出现。浮游植物群落结构的时空变化特征：调水调沙前，共鉴定出42种浮游植物，优势种主要是具槽帕拉藻；细胞总丰度为1.65×10⁵ cells/L，分布较为平均；浮游植物多样性指数（H′）平均值为 1.14，高值主要分布在黄河口西北方向海域；叶绿素a的平均浓度为2.98μg/L，高值主要分布在黄河口西南方向海域。调水调沙后，3个月分别鉴定出95、100、56种浮游植物，受盐度变化影响，6、7月份优势种中除硅藻类增加了绿藻类（衣藻和栅藻），9月份优势种主要是圆筛藻；细胞总丰度6月份最高（27.0×10⁵ cells/L），高值主要分布在河口东北方向海域；H′平均值最高出现在7月份（3.05），高值主要分布在河口正北海域；叶绿素a的平均浓度在9月份达到最高（15.5 μg/L），高值主要分布在黄河口西北以及东南方向海域。通过浮游植物群落结构与环境因子之间的相关性进行典范对应分析（CCA），发现调水调沙前，温度、DIN、DIP是影响浮游植物群落结构的主要因子；调水调沙后，盐度、DSi、DIP是影响浮游植物群落结构的主要因子。对比调水调沙前后环境因子与浮游植物群落的时空变化特征可知，实施调水调沙，使得调查海域盐度有明显的降低，硅限制得到有效缓解；浮游植物生物量和多样性指数都有所提升，其中淡水藻类由于盐度的降低而增多，削弱了硅藻的竞争优势，使硅藻在物种组成中所占比例约降低了30%，空间上淡水藻有向河口东南部莱州湾海域方向分布趋势。
  进而，通过对莱州湾区域的调查，进一步探究调水调沙前后，环境条件变化对整个海湾的影响。莱州湾海域环境因子的时空变化特征：调水调沙前（5月份），平均温度和盐度分别为14.8°C 和27.9，低盐区域分布在黄河口与小清河河口之间海域；营养盐结构分析表明，不存在DIN限制，仅1个站位存在DIP的相对限制，但 80%的站位存在DSi限制。调水调沙后（9月份），平均温度和盐度值分别为25.8 °C 和28.7，低盐区域分布在黄河口与小清河河口之间海域；营养盐结构分析表明，不存在 DIN 限制，86.7%的站位存在DIP的相对限制，仅有1个站位存在DSi限制。浮游植物群落结构的时空变化特征：调水调沙前，共鉴定出87种浮游植物，优势种主要是舟形藻；细胞总丰度为1.80 × 10⁵ cells/L，高值区分布在湾中底部海域；H′平均值为2.47，高值主要分布在湾口海域；叶绿素a的平均浓度为4.62 μg/L，高值主要分布在小清河河口海域。调水调沙后，共鉴定出112种浮游植物，优势种主要是硅藻类，种类较多但无优势度突出的优势种；细胞总丰度为3.40 × 10⁵ cells/L，高值区分布在湾边缘沿岸海域；H′平均值为3.28，高值主要分布在黄河口与小清河河口之间海域；叶绿素a的平均浓度为4.35 μg/L，高值主要分布在白浪河以及胶莱河河口海域。通过浮游植物群落结构与环境因子之间的相关性进行典范对应分析（CCA），发现调水调沙前，温度、DIN、DIP是影响浮游植物群落结构的主要因子；调水调沙后，DSi、DIP是影响浮游植物群落结构的主要因子。对比调水调沙前后环境因子与浮游植物群落的时空变化特征可知，实施调水调沙，未造成盐度的变化，DSi的补充使DSi限制得到缓解，浮游植物生物量和多样性指数有所提高。
  总体来看：调水调沙不仅影响黄河口海域，也影响到莱州湾海域。该事件发生后黄河水沙可影响黄河口的西北部到莱州湾湾底的海域，影响可以持续到9月份。

  Estuaries are the intermediate zone which are the connection of terrestrial and ocean ecosystem. With the construction of dams and reservoir in the up- and middle stream of the river, the amount of sediment that flow into ocean was decreased sharply which would bring about significant influence on the estuary ecosystem. The present investigations were performed in Yellow River estuary at April, June, July and September 2013, and in Laizhou Bay at May and September 2014 along with water and sediment regulation event (WSRE). The temperature, salinity, nutrients, chlorophyll a and the structure of phytoplankton community were analyzed and compared variations of environmental factors and phytoplankton community before and after WSRE. The results could provide the basic information for understanding the mechanisms of phytoplankton response and ecological impact of the event.
 The results showed that before WSRE (in April), the average values of temperature and salinity were 8.01 °C and 26.2, with higher temperature and lower salinity appeared the northern estuary. The analyzing of nutrient structure indicated that there was no dissloved inorganic nitrogen (DIN) limitation but occurred dissloved inorganic phosphorus (DIP) and dissloved silicate (DSi) limitation. After WSRE (June, July andSeptember), the highest average temperature (25.2 °C) and salinity (20.8) appeared in July. The lower values of salinity appeared inshore of the estuary. There was no DIN limitation but occurred DIP limitation, and DSi limitation only emerged in the northwest part of estuary in June. By analyzing the variations of phytoplankton community, 42 species of phytoplankton were identified and Paralia sulcata was emerged as dominant species before WSRE; the total cell abundance was 1.65 ×10⁵ cells/L and distributed evenly; the average of Shanno-Wiener index (H′) was 1.14 and higher value appeared in northwest of estuary; the average concentration of chlorophyll a was 2.98 μg/L and higher value appeared in southwest of estuary. After WSRE, 95, 100 and 56 species of phytoplankton were identified in June, July and September, respectively; the green algae were emerged as dominant species due to the low salinity at June and July while the dominant species was diatom at September. The highest total cells abundance was 27.0 × 10⁵ cells/L in June and the highest value distributed in north area of Yellow River estuary at June; the highest value of total cell abundance of July distributed in southeast area while the total cell abundance of September was lower than April and distributed evenly. The July with highest H′ and higher value emerged in the north area of the estuary whereas higher value of H′ of June and September distributed in the east, and east and north part of estuary. The highest value of chlorophyll a was 15.5 μg/L and appeared at September, and higher value existed at the northwest and southeast part of the estuary. The results of Canonical Correspondence Analysis between phytoplankton assemblages and environmental factors indicated that temperature, DIN, and DIP were the dominant factors which affect the structure of phytoplankton community before WSRE but salinity, DSi, and DIP were the factors after WSRE. Comparing the temporal variation of environmental factors and the structure of phytoplankton before WSRE with after WSRE, the salinity was obviously decreased after WSRE and DSi limitation was alleviated, and the abundance of phytoplankton was increased; among the phytoplankton, the abundance of freshwater species increased as the result of declination of salinity, then weaken the competitive advantage of diatom; thus the percentage of diatom in the composition of species decreased 30%.  
 The survey was carried out in Laizhou Bay in order to further explore the impact of WSRE. The results showed that before WSRE (in May), the average value of temperature and salinity were 14.8 °C and 27.9, with lower salinity appeared seawater which between estuaries of Yellow River and Xiaoqing River. The analyzing of nutrient structure indicated that there was no DIN limitation and only one site with DIP limitation, while up to 80% sites showed DSi limitation. After WSRE (in September), the average value of temperature and salinity were 25.8 °C and 28.7, with lower salinity appeared seawater the same with before WSRE. The analyzing of nutrient structure indicated that there was no DIN limitation and 86.7% of the sites had DIP limitation, but only one site had DSi limitation. By analyzing the variations of phytoplankton community, 86 species were identified and Navicula sp. was emerged as dominant species before WSRE; the total cell abundance was 1.80 ×10⁵ cells/L with high value distributed in middle and bottom of the lay; the average of H′ was 2.47 and higher value appeared in the mouth of lay; the average concentration of chlorophyll a was 4.62 μg/L and higher value appeared in Xiaoqing River estuary. After WSRE, 112 species were identified and the dominant species belong to diatoms while there was not higher dominance index; the total cell abundance was 3.40 × 10⁵ cells/L with high value distributed inshore; the average of H′ was 3.28 and higher value appeared in seawater which between estuaries of Yellow River and Xiaoqing River; the average concentration of chlorophyll a was 4.35 μg/L and higher value appeared in estuaries of Bailang River and Jiaolai River. The results of Canonical Correspondence Analysis between phytoplankton assemblages and environmental factors indicated that temperature, DIN, and DIP were the dominant factors which affect the structure of phytoplankton community before WSRE but DSi, and DIP were the factors after WSRE. Comparing the temporal variation of environmental factors and the structure of phytoplankton before WSRE with after WSRE, the salinity was not changed obviously and DSi limitation was alleviated which might be result in increasing the abundance and biomass of phytoplankton.
  In conclusion, WSRE could affect the Yellow River estuary and Laizhou Bay. The WSRE was likely affect the zone from the northwest of the Yellow River estuary to the bottom of Laizhou Bay in spatial, and the influence might last until September in temporal.