热带东印度洋春季浮游植物群落结构空间特征分析

Spatial structure characteristics of phytoplankton communities in the tropical eastern Indian Ocean in spring

基于2013年3月至5月采集的热带东印度洋海域(10.0°S^4.0°N, 83.0°~97.5°E)浮游植物水样样品,分析了其种类组成、优势类群、细胞丰度等群落特征参数,综合比较了水平和垂向上浮游植物种类及丰度的差异性,初步探讨了其成因。结果表明:2013年春季热带东印度洋微型浮游植物共鉴定出306种,主要由硅藻、甲藻、金藻、蓝藻、裸藻和隐藻六大门类组成,其优势类群主要以粒径较小的隐藻、微型甲藻、菱形藻、环沟藻等为主。水平分布上,各水层浮游植物细胞丰度分布趋势相似,但斑块特征明显,其高值区位于88°E断面赤道以南次表层水域(30 m、75 m),局部区域细胞丰度值可达104 cells/L以上;与其毗邻的东南部、东部水域为低值区,并向赤道延伸。垂直剖面上,硅藻和甲藻广泛分布在各取样深度,但分布特征有明显的空间差异和规律,0 m、30 m大部分站位硅藻种类比例在0.2~0.3甚至更低,甲藻在0.7~0.8,随着水层加深(75 m、100 m、150 m、300 m),硅藻种类占比上升到0.5~0.6,甲藻降低到0.4~0.5,无论硅藻还是甲藻种类数75 m层最丰富。30 m和75 m水层细胞丰度明显高于其他水层。甲藻是热带东印度洋微型浮游植物种类和细胞丰度的重要贡献者,低生物量海域表现的更为明显,贡献率大于80%。该研究将极大丰富东印度洋浮游植物群落空间特征基础信息较匮乏的现状,为量化、评估该海域的生物资源提供数据支撑。

The phytoplankton water samples were collected in the multidisciplinary investigations in the tropical eastern Indian Ocean(10.0°S-4.0°N, 83.0°-97.5°E) during March to May, 2013. Phytoplankton community structure features were analyzed, including species composition, cell abundance, dominant species. In addition, the species composition and abundance of phytoplankton were compared comprehensively by horizontal and vertical investigation, and the probable causes were also discussed. A total of 306 species(including varieties and forms)were identified, which belonged to 6 phyla(Bacillariophyta, Pyrrophyta, Chrysophyta, Cyanophyta, Euglenophyta and Cryptophyta). The dominant groups were mainly Cryptomonadaceae, Nano-dinoflagellate, Nitzschina spp.(diatoms), Gyrodinium spp.(dinoflagellates), etc., which were smaller cells in size. Horizontally, the cell abundance was similar at different layers with patchy distribution characteristics. The high cell abundance(104 cells/L) was in subsurface water(30 m and 75 m) at south of the equator on 88°E section. However, adjacent to the high abundance area, a larger area of low abundance appeared in the eastern and southeastern parts of the survey area, which extended to the equator. Vertically, diatoms and dinoflagellates were widely distributed at different depths with obvious spatial pattern. At most stations of 0 m and 30 m layers, the proportion of diatoms was 0.2-0.3 or even lower,while that of dinoflagellates was 0.7-0.8;in deeper water layers(75 m, 100 m, 150 m, 300 m), the proportion of diatoms increased to 0.5-0.6, and that of dinoflagellates decreased to 0.4-0.5 inversely. The species richness of diatoms and dinoflagellates were relatively higher at 30 m and 75 m layers. Dinoflagellates were important contributors to the species composition and cell abundance of phytoplankton in the tropical eastern Indian Ocean, especially in low abundance area(80%). This study will greatly enrich the database of phytoplankton community characteristics in the tropical eastern Indian Ocean, and provide data support for quantifying and evaluating the biological resources in this area.