汉江中下游春季硅藻水华暴发的生态学机制

Since 1992, diatom bloom has occurred frequently in the middle down reaches of the Hanjiang River during the early spring.Many researches have been taken on the diatom bloom outbreak, especially on the relationship between the algal bloom and environmental factors such as hydrology,metorology, but few care about the effect of the input of algal seed source from the other system. It became highlight spot in the research of mechanism of water bloom outbreak in the view of seed sources input, especially in the river system. During the preliminary researches, our work team had found out that spring diatom bloom of the Hanjaing River outbreak have closely linked to the seed sources input from the branches of the Hanjiang River. Therefore,we propose that seed source input play a very important role in the mechanism outbreak of water bloom in river system. this project will focus on the middle down reaches of the Hanjiang River to research the mechanism of the water bloom outbreak. The researches work will be taken by the combination of the field investigation and laboratory experiment tests. With the researches of the water bloom species competition mechanism as the researches entry point, and take researches on the mechanism of diatom bloom outbreak in the area of seed sources input. and exporing the effect of the coupling mechanism of the seed sources input with the environmental factors. Then illustrates the mechanism of the spring diatom bloom outbreak in the Hanjiang River. The results of his research project will provide theoretical and technical guidance for the prevention and controlling of water bloom in the Hanjiang River. and develop new ideas and methods for the water bloom prevention and controlling water bloom in river system.

自1992年以来，汉江中下游多次暴发春季硅藻水华。已有的研究主要围绕水华暴发过程与水文等主要环境因子间的关系进行，对种源的输入途径及其在水华暴发过程中的作用缺乏关注和研究。申请人前期研究发现汉江中下游干流中暴发春季硅藻水华的年份常与上游的汇入支流中高密度藻华现象同步发生。据此推论汇入汉江的支流水体藻源的持续输入在汉江中下游干流水华的发生过程中可能起着重要作用。本项目拟以汉江中下游干支流为研究对象，采用野外调查和室内模拟实验相结合的方法，通过解析形成汉江春季水华的优势硅藻的生物学特征，结合对支流种源输入区及其下游干流水华发生过程的同步跟踪，探寻种源输入与关键环境因子耦合在汉江中下游干流水华暴发过程中的作用机制，进而阐明汉江中下游春季硅藻水华暴发机制。研究结果有望为汉江中下游水华的预防和控制提供理论依据和技术指导，拓展河流水华预防和控制的思路和方法。

随着经济社会的发展，环境污染特别是水环境污染问题日益严峻。由于大量的点源和非点源污染物的大量输入水体，水体的营养盐负荷逐年增加，水体富营养化程度和范围日益扩大，严重影响水生态环境的安全。加之近年来大规模的水利工程的建设，显著改变了水体的水文情势，将在一定程度上改变河流的物质循环和能量流动，进而对水生态环境产生一定的影响。.浮游植物作为水体的初级生产者，在生态系统的能量流动和物质循环过程起到十分重要的作用。然而由于水环境污染和由此而产生的富营养化的加剧，显著改变了水体中浮游藻类的结构和组成，个别藻类成为优势种而产生明显的水华问题，严重制约经济社会发展。不仅湖泊水华频发，近年来河流水库水华也时有发生，如长江三峡库区及主要入库支流水华，钱塘江水华、以及汉江中下游春季硅藻水华，给经济社会发展产生了一定的影响，特别是作为南水北调中线工程的水源地的汉江流域，冬春季水华问题日益严峻，迫切需要开展汉江春季硅藻水华暴发机理研究。.本研究拟从野外调查、室内模拟和水文分析的角度，深入开展汉江中下游春季硅藻水华问题的研究，主要包括以下三个方面内容：.1.汉江中下游浮游植物时空演替研究.通过为期4年多的现场调查采样，分析了汉江中下游浮游植物时空格局及演替特性，分析了春季影响汉江中下游干支流冠盘藻水华暴发的主要环境影响因素，并从种源输入的角度分析了汉江中下游春季硅藻水华暴发的原因。.2.汉江春季硅藻水华优势种——冠盘藻的生物学特性研究.以汉江春季硅藻水华优势种——冠盘藻为藻种进行室内培养，研究不同温度、光照条件、营养盐负荷、流速条件等对藻类繁殖的影响，运用叶绿素荧光技术分析不同培养条件下冠盘藻的生物活性，研究冠盘藻的生物学特性，从汉江水华硅藻优势种——冠盘藻的生物学特性方面揭示汉江水华暴发的机理。.3.汉江春季硅藻水华暴发的关键水文阈值研究.以汉江中下游的代表性水文站点的历史水文资料为基础，结合历年汉江中下游水华暴发情况，分析汉江中下游历次暴发硅藻水华的水文条件，通过水文排频的方法，研究分析汉江中下游春季硅藻水华暴发的关键水文阈值，从而提出控制汉江中下游春季硅藻水华的水文阈值。.研究结果为汉江中下游春季硅藻水华的预防和控制提供科学依据，特别对于南水北调中线工程调水后，汉江中下游水量明显减少的情况下，维护汉江中下游生态环境健康，防治或减缓水华暴发有着重要的参考价值。