Abstract

Ulva prolifera blooms have occurred every summer in the South Yellow Sea since 2008. U. prolifera blooms appeared in the area near the Jiangsu shoal and then were driven to the Shandong Peninsula by the prevailing summer winds. The blooms covered a maximum area of more than 50000 km² and had an aggregate estimated biomass of 3.64 × 10⁵ tons. Large number of U. prolifera dissipation in the natural degradation and this cause a serious impact on the marine environment. We used MODIS, HJ-1A/B and GF-1 remote sensing image data to conduct large-scale monitoring of U. prolifera. Combined with sea surface monitoring station data from Haiyang city, Shandong province, we analyzed the impact of U. prolifera death on the coastal sea environment of Haiyang city from 2012 to 2016 using multiple regression analysis. It showed that chlorophyll-a concentration was related to sea surface temperature (SST), salinity, dissolved inorganic nitrogen (DIN) and phosphate (R² = 0.50, P < 0.001). Among these, DIN and phosphate were important factors affecting chlorophyll-a concentration. There was a significant positive correlation between chlorophyll-a concentration and DIN, but a significant negative correlation between chlorophyll-a concentration and phosphate. The nutrients released by the decomposition of U. prolifera enhanced the growth of planktonic microalgae, and increased the mean chlorophyll-a concentration from 1.398 μmol/L to 2.819 μmol/L during May to August in the study area. This increased the Level of eutrophication in the coastal area and contributed to blooms of secondary algae such as red tides.

摘要

自2008年以来，南黄海每年夏季都会发生石莼水华。江苏沙洲附近地区出现石莼水华，然后被盛行的夏季风吹到山东半岛。这些水华的最大面积超过50000 km ²，估计总生物量为3.64 × 10 ⁵吨。大量的U. prolifera在自然退化中消散，对海洋环境造成严重影响。我们利用MODIS、HJ-1A/B和GF-1遥感影像数据对U. prolifera进行了大规模监测。结合山东省海阳市海面监测站数据，分析了海阳市2012-2016年沿海海洋环境中的U. prolifera死亡情况采用多元回归分析。结果表明，叶绿素a浓度与海面温度（SST）、盐度、溶解无机氮（DIN）和磷酸盐（R ²  = 0.50，P < 0.001）有关。其中，DIN和磷酸盐是影响叶绿素a浓度的重要因素。叶绿素a浓度与DIN呈显着正相关，而叶绿素a浓度与磷酸盐呈显着负相关。U. prolifera分解释放的养分促进了浮游微藻的生长，使研究区5-8月的平均叶绿素-a浓度从1,398 μmol/L提高到2,819 μmol/L。这增加了沿海地区的富营养化程度，并导致赤潮等次生藻类大量繁殖。