夏季长江口邻近海域活体底栖有孔虫优势种群及分布特征研究

Study on Dominant Species and Distribution Characteristics of Living Benthic Foraminifera in the Adjacent Sea Area of Yangtze River Estuary in Summer Season

针对长江口及其邻近海域活体底栖有孔虫相关研究较为缺乏的问题,本研究对2016年7月长江口海域33个站位的表层沉积物进行了活体底栖有孔虫属种的鉴定和分析。发现研究海域活体底栖有孔虫共23属31种,丰度范围为0~21 ind./g,简单分异度范围为0~16种。优势种群为优美花朵虫(Florilus decorus)、杰克逊小九字虫(Nonionella jacksonensis)、亚易变筛九字虫(Cribrononion subincertum)、耳状脓泡虫(Cancris auriculus)、日本半泽虫(Hanzawaia nipponica)、条纹判草虫(Brizalina striatula)、亚洲沙壁虫(Arenoparella asiatica)、毕克卷转虫变种(Ammonia beccarii vars.)和压扁卷转虫(Ammonia compressiuscula)。活体有孔虫丰度较高的区域多集中在A3和A4断面所在海域,而在研究区域的东北部海域丰度整体较低。除长江口门以外,近岸海域具有“丰度高、属种少”的特征,而在A3和A4断面的远岸海域,则具有“丰度高、属种多”的特征。有孔虫的分布情况表明,A.beccarii vars.是研究区域内活体分布最广的种群,F.decorus是活体占比最高的种群,同时也是除A.beccarii vars.以外分布最广的种群。C.subincertum的丰度随离岸距离的增大而迅速减小,是典型的近岸优势种。

In view of the lack of studies on living benthic foraminifera in the Yangtze River Estuary and its adjacent sea area,in this study,living benthic foraminifera species were identified and analyzed from the surface sediments of 33 stations in the Yangtze River Estuary in July 2016.The results showed that there were 31 species,belonging to 23 genera of living benthic foraminiferas,with abundance ranged from 0 to 21 ind./g and the simple diversity ranged from 0 to 16 specis.Dominant species were Florilus decorus,Nonionella jacksonensis,Cribrononion subincertum,Cancris auriculus,Hanzawaia nipponica,Brizalina striatula,Arenoparella asiatica,Ammonia beccarii vars.and Ammonia compressiuscula.The abundance of living foraminifera was higher in the sea areas of A3 and A4 sections,while was lower in the northeast of the study sea area.The coastal area was characterized by"high abundance and less diversity"(except the Yangtze River mouth area),while the offshore area of A3 and A4 sections were characterized by"high abundance and more diversity".The distributions of living foraminiferas showed that Ammonia beccarii vars.was the most widely distributed species,Florilus decorus had the highest proportion and also was the second most widespread species after Ammonia beccarii vars.in study area.The abundance of Cribrononion subcincertum decreased rapidly from nearshore to offshore,indicating this foraminifera is a typical dominant species in nearshore.Results of this study will have significant help to understand the distribution patterns and varation factors of the benthic foraminifera in the Yangtze River estuary.