印度洋东经90°海岭区具有复杂而独特的地形特征, 为深入了解海岭区不同部位底栖生物生态特征、区域生物生产力及陆源输入影响, 对东北印度洋海岭区13个表层沉积物样品中大于150μm壳径的底栖有孔虫组合进行了定量分析。研究发现该区底栖有孔虫以150~250μm粒径为主, 相对丰度为60~84%, 大于250μm壳径粒级的底栖有孔虫相对丰度较低, 为16~40%。优势底栖有孔虫属种以表生种和中浅内生种为主。研究区底栖有孔虫以玻璃质壳为主, 胶结质壳次之, 瓷质壳含量最低。底栖有孔虫主要属种组成没有明显差异, 但其绝对丰度、三大类壳体组成和表/内生种的分布仍表现出一定的区域差异: 底栖有孔虫丰度在海岭北部两侧相对较高, 海岭上相对较低, 底栖有孔虫胶结壳的相对含量在研究区东北侧明显较其他区域要高, 在海岭中部区域胶结质底栖有孔虫含量随水深的增加而增加, 胶结质底栖有孔虫壳壁建造所选颗粒在东北部以碎屑矿物为主。综合分析认为, 东北印度洋海岭区底栖有孔虫主要受陆源物质输运、表层生产力分布和水深变化引起的溶解作用的影响。此外, 我们首次注意到在大于250μm的组分中, 所有站位表生种含量远大于内生种, 我们认为这是底栖有孔虫对高氧生态环境适应演化的结果。

The northeastern Indian Ocean Ridge area along the 90°E meridian exhibits complex and unique topographic features. To gain deeper insights into the benthic ecological characteristics, regional biological productivity, and terrigenous input influences across different parts of the ridge, a comprehensive identification and statistical analysis of benthic foraminifera (>150 μm) was conducted on 13 surface sediment samples from this region. The study revealed that benthic foraminifera in the 150-250 μm size fraction dominated the area with relative abundances of 60-84%, while the fraction larger than 250 μm exhibited lower relative abundances of 16-40%. The dominant benthic foraminiferal species were primarily epifaunal and shallow infaunal types. Among the three major benthic foraminiferal shell types, hyaline shells predominated, followed by agglutinated shells, with porcellaneous shells being least abundant. Although no significant differences in dominant species were observed among stations, distinct regional variations emerged in shell-type proportions and epifaunal or infaunal distributions: the abundance of benthic foraminifera is relatively high on both sides of the northern ridge and relatively low on the ridge; The relative content of agglutinated benthic foraminifera is significantly higher in the northeast side of the study area compared to other areas, and the content of agglutinated benthic foraminifera increases with increasing water depth in the central part of the Indian Ocean Ridge. The particles selected for the construction of the shell walls of agglutinated benthic foraminifera are mainly composed of detrital minerals in the northeast, while multi-species planktic foraminifera have been used to build their test in the central part of the Indian Ocean Ridge. Analysis suggests that benthic foraminifera in the northeast Indian Ocean ridge area are mainly influenced by the transport of terrestrial materials, surface productivity distribution, and dissolution caused by changes in water depth. In addition, we have noticed for the first time that the content of surface species is much higher than that of epifaunal species in the components larger than 250 μm. We believe this is the result of the adaptation and evolution of benthic foraminifera to high oxygen ecological environments.