A study on environmental changes based upon cladoceran assemblages from the core sediments in Chen Co, southern Tibet
A study on environmental changes based upon cladoceran assemblages from the core sediments in Chen Co, southern Tibet
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DOI：
10.1360/982005-124
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发表时间：
2005-07
影响因子：
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通讯作者：
Liping Zhu;Junbo Wang;A. Brancelj
中科院分区：
文献类型：
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作者：
Liping Zhu;Junbo Wang;A. Brancelj
1998年，在藏南陈错湖进行了连续沉积物岩心（CC 2）钻探。对柱状样顶部117 cm剖面的枝藻化石进行了种类、数量、丰富度和生态特征分析，并据此划分出5个枝藻组合。CL 0是一个在117-105 cm深度范围内没有枝角类的组合。CL 1组合（深度在101-77厘米之间，约。1407-1533 AD），共有9种枝藻出现在岩芯中，在整个序列中表现出最大的丰富度。这一组合反映了在较温暖的条件下，有大量的外来冷水和有机碎屑输入沉积场地。湖水又宽又浅，适合大型水生植物生长。CL 2组合的枝藻种类和丰富度（深度在77-29厘米之间，约。1533-1831 AD）比CL 1表现出更多的降低。只有少量的球腹脂鲤适应范围较广。这表明该沉积环境恶劣，绝大多数枝藻已丧失了生存能力。与CL 1组合相比，CL 3组合（深度在29-10 cm之间，约. 1831-1941 AD）具有几乎相同的优势种，但较低的丰富度。特别是枝晶藻对有机碎屑的偏好也有所减少。这说明流域内地表植被状况虽然有所改善，但仍然很差。除2种浮游动物外，其余7种枝藻均为CL 4组合（水深10-0 cm，约1000 ~ 10000 m）。1941-1998 AD），广温种与窄温种相比，没有表现出竞争能力。这表明在浅水条件下，水温是稳定的，受气温的影响更大。CC 2孔枝角类组合所反映的环境特征得到平行CC 1孔介形虫组合、硅藻土-盐度转换功能、环境磁性和相关指标的证据的充分支持。青藏高原湖泊沉积物中的枝藻组合对沉积环境十分敏感，对研究环境变化具有重要意义。
A consecutive sediment core (CC2) was drilled in Chen Co (lake) of southern Tibet using a PISTON sampler in 1998 AD. Cladoceran remains including their species, amount richness and ecological features are analyzed for the top 117 cm sections of the core, upon which 5 cladoceran assemblages are distinguished. CL0 is an assemblage without any cladocera in the depth between 117–105 cm. CL1 assemblage (depths between 101–77 cm, ca. 1407–1533 AD) possesses total 9 cladoceran species that appear in the core, and performs the greatest richness in the whole sequence. This assemblage reflected that there was plenty of exotic cold water and organic debrises inputing to the sedimentary site under the warmer conditions. The lake was wide and shallow that satisfied the big hydrophyte living. Cladoceran species and richnesses of CL2 assemblage (depths between 77–29 cm, ca. 1533–1831 AD) perform much more decreasing than those of CL1. There was only less Chydorus sphaericus which was acclimatized to wide environmental ranges. This implied that the sedimentary environment is so execrable that most of cladoceran lost their living abilities. Compared with CL1 assemblage, CL3 assemblage (depths between 29–10 cm, ca. 1831–1941 AD) possesses nearly the same dominant species but lower richnesses. Especially, the cladoceran preferring organic debris also decrease in their amounts. This meant that the surface vegetation in the drainage basin was still poor though the environment turned to be better. Except the 2 Zooplankton species, the other 7 species of cladoceran in this core are found in CL4 assemblage (depths between 10-0 cm, ca. 1941–1998 AD), in which the eurythermal species had not performed their competition ability comparing with narrow-temperatures adapted species. It implied that water temperatures were stable and much more influenced by air temperatures under the shallow-water conditions. The environmental features reflected by cladocera assemblages of CC2 core are fully supported by the evidences from ostracoda assemblages, diatom-salinity transfunction, environmental magnetism and relative proxies of the parallel CC1 core. Cladoceran assemblages in the lake sediments of Tibetan Plateau are sensitive to sedimentary environment and very significant to the studies of environmental changes.