近百年洱海蓝藻群落演替过程重建及与人类活动的关系研究

Anthropogenic activities are the main driving forces for the lake eutrophication of China. Eutrophication causes succession of phytoplankton community and may induce algal bloom. Algal bloom occurred in many lakes in China has already posed threats on water resources and aquatic ecosystem. Toxic cyanobaterial bloom also occurred in Erhai lake, the second largest freshwater lake of Yunnan-Guizhou plateau, although the water quality of Erhai lake still remained at class II to III. The dominant bloom-forming cyanobateria showed succession from Aphanizomenon to Anabeana and to Microcystis presently during the last 30 years. The mechanism of the occurrence and succession of cyanobacterial bloom in mesotrophic lake is not well understood. Therefore in this project we plan to collect the sediment cores of Erhai lake, constructing the chronology by 210Pb/137Cs dating, to reconstruct the succession process over the last 100 years of cyanobaterial communities by sediment pigment analysis and qPCR/DGGE analysis, as well as the change of algal bloom scale in last 30 years by retrieval of Chl-a values from remote sensing data. The paleolimnological proxies for human activities will also be determined with the sediment cores, to reconstruct the anthropogenic disturbance process over the last 100 years with the supplement of local socio-economic data. The main driving factors will be identified by relationship analysis between the cyanbaterial community succession and the human activities. The influence of local climate change on the cyanobacterial community succession will be evaluated. The results of this project will be of benefit to the prevention of cyanobacterial bloom in Erhai lake as well as in other mesotrophic lakes.

人类活动是我国湖泊富营养化发展的主要驱动力，湖泊富营养化则引起浮游植物群落演替并可能导致水华现象。云贵高原第二大淡水湖洱海虽然水质为II-III类，但已发生有毒蓝藻水华，且近30年水华蓝藻优势种发生了从束丝藻-鱼腥藻-微囊藻的演替。目前这类富营养初期湖泊的蓝藻水华发生规律尚未明了。本项目将以洱海为对象，在210Pb/137Cs测年基础上，采用沉积物的蓝藻DNA分析检测新技术和藻类色素高分辨分析检测技术，结合卫星遥感历史数据，重建近百年洱海的蓝藻群落演替过程和蓝藻水华规模变化过程；以沉积物人类活动相关标志物分析，结合流域社会经济数据，重建近百年流域人类活动干扰过程；通过蓝藻演替和人为干扰之间的关系研究，解析蓝藻水华发生和演替的驱动因子。同时本研究还将结合流域气象变化历史数据，分析当地气候变化对蓝藻水华的影响强度。本研究结果将为洱海以及其他富营养初期湖泊的蓝藻水华防治提供基础理论依据。

人类活动是我国湖泊富营养化发展的主要驱动力，湖泊富营养化则引起浮游植物群落演替并可能导致水华现象。云贵高原第二大淡水湖洱海虽然水质为II-III类，但已发生有毒蓝藻水华，且近30年水华蓝藻优势种发生了从束丝藻-鱼腥藻-微囊藻的演替，其水华发生和演替的机制尚未阐明。本项目采集了洱海沉积物柱芯，提取了沉积物的古DNA，采用qPCR技术分析了三种水华蓝藻的变化过程，采用高通量测序技术分析了蓝藻群落演替过程，采用沉积物藻类色素分析检测技术分析了浮游植物群落演替过程，并结合卫星遥感历史数据，在210Pb/137Cs测年基础上，重建近百年洱海的蓝藻群落演替过程和蓝藻水华规模变化过程。研究结果显示近百年来蓝藻、绿藻、硅藻一直是洱海浮游植物优势类群，洱海浮游植物丰度在上世纪八十年代之前维持低水平且变化小，从八十年代后期开始急剧增加；1902-1967AD期间以束丝藻水华为主，1967-1996AD期间微囊藻属和长孢藻属均为优势水华蓝藻，1996AD之后则微囊藻水华占优势。洱海遥感结果表明，2002年前只有1996年曾经有着较大范围的水华暴发，但从2002年开始水华爆发的频度与面积都有了显著的增加。氮肥量、磷肥量、城镇化率、奶牛养殖数、旅游人口是浮游植物群落演替以及水华蓝藻物种更替的主要驱动因素，人类活动因素与气候变化分别独立解释了水华蓝藻组成变化的95%和4%，二者共同解释了47%。微囊藻属Microcystis与洱海流域氮磷输入显著正相关，长孢藻属与洱海水位变幅有极显著正相关性，而束丝藻属与氮肥量、磷肥量、降雨量显著正相关。