黄渤海典型近岸海域叶绿素a含量空间分布及其与环境因子的关系

Spatial Distribution of Chlorophyll a and Its Relationship with Environmental Factors in Four Typical Coastal Regions in the Bohai Sea and the Yellow Sea

关键词:  赤潮  叶绿素a  环境因子  空间分析  富营养化

Key words:  red tide  chlorophyll a  environmental factors  spatial analysis  eutrophication

摘要:

在黄渤海海域，春夏季赤潮多发，是海洋生态安全的潜在威胁。叶绿素a（Chl a）含量作为反映浮游植物生物量的关键指标，在该海域具有明显的时空变异。通过冷热点分析、相关性分析等方法，对比研究了2016年和2021年夏季黄渤海典型近岸海域（秦皇岛、天津、东港邻近海域及胶州湾海域）叶绿素a含量的分布状况及其相关环境因子，探索该海域富营养化特征，以期为赤潮研究提供科学依据。研究结果表明，夏季叶绿素a含量高值区分布在离岸较近海域，分布状况与显著相关环境因子的分布具有空间联系。黄渤海典型近岸海域存在富营养化现象，其中天津邻近海域富营养化最明显。通过两年度对比分析发现，渤海典型近岸海域叶绿素a含量在2021年略有降低，其分布特征与盐度和营养盐尤其是溶解无机氮变化具有相关性，可能与河流径流量的变化有关。黄海典型近岸海域叶绿素a含量则有所升高，东港邻近海域所处位置相对开放，叶绿素a含量与温度显著相关，与营养盐如磷酸盐和硅酸盐也具有相关性，而胶州湾海域叶绿素a含量变化与本研究分析的环境因子之间没有显著相关性。

Abstract:

The Bohai Sea and the Yellow Sea have experienced high frequency of red tides in spring and summer, which poses a potential threat to marine ecological security. As a key indicator of phytoplankton biomass, chlorophyll a concentration has exhibited distinct spatial and temporal variations in this area. In this study, the characteristics of chlorophyll a spatial distribution, as well as the eutrophication status in summer 2016 and 2021 were analyzed by high/low clustering and correlation analysis in four selected regions, i.e., the coastal waters of Qinhuangdao, Tianjin, Donggang and Jiaozhou Bay, supporting for the study of red tides. The results indicated that high concentration of chlorophyll a occurred mainly in the regions near to the coast, and the distribution pattern was consistent with the related environmental factors. Eutrophication was found in the typical coastal waters of the Yellow Sea and Bohai Sea, especially in the waters near Tianjin. It was found that the decrease of chlorophyll a concentration in the typical coastal regions of Bohai Sea was related with salinity and dissolved inorganic nitrogen, which may be affected by the change of river runoff. The concentration of chlorophyll a in the typical coastal regions of Yellow Sea increased in 2021 compared with 2016, and the variation of chlorophyll a concentration in Donggang which is adjacent to open sea was significantly related with temperature and nutrients like phosphate and silicate. In Jiaozhou Bay, however, there was no significant correlation between chlorophyll a concentration and the environmental factors analyzed in this study.