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MECHANISMS AND EFFICIENCY OF ALGAL BLOOM REGULATION BY AERATION/CIRCULATION IN RESERVOIRS

水库通气/循环调节藻华的机制和效率

基本信息

批准号：
06650557
负责人：
ASAEDA Takashi
金额：
$ 1.28万
依托单位：
SAITAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

First, impacts of aeration/circulation on the algal bloom were analyzed from previous observations in actual reservoirs. Then, structures to reduce algal bloom were classified as follows.(1)The formation of the epilimnetic mixed layr thicker than the euphotic layr, causing the light limitatin for the algal growth first, then changing the predominant species from cyanobacteria to greens and diatoms.(2)The reduction of pH, causing the change in the dominant algae from cyanobacteria to edible greens and diatoms.(3)The lowering epilimnetic temperature, reducing the algal growth rate.(4)The hypolimnetic aeration.These mechanisms were confirmed and evaluated by a numerical model, which was comprised of a reservoir model based on DYRESM,double plume circulation model, nutrients model, and biological process, including 4 types of algae.First, several experimental results were simulated, indicating process of the algal biomass change during the operation. Then, successful and unsuccessful operational conditions were parameterized by making calculations in various boundary conditions.Next, the condition for the most effcient destratification was parameterized, which shows that the destratification would be completed with less than 10% of energy being used at present.Since the important structure is not only the reduction of algal biomass but also the transion from cyanobacteria predominacy to edible species, which eventually changes the entire ecological condition, thus this bottom-up effects will be the key point. Thus, the field investigation was made in several lakes and reservoirs to understand the food web mechanisms. Also, a simple food web model was developed including the higher predators, such as zooplankton and two kinds of fish.

首先，通过对实际水库的观测，分析了曝气/循环对藻华的影响。然后，对减少藻华的结构进行了分类。(1)泛光混合层的形成比泛光层更厚，首先对藻类生长造成光照限制，然后优势种由蓝藻变为绿藻和硅藻。(2) pH降低，导致优势藻类由蓝藻转变为可食用的绿色和硅藻。(3)海水温度降低，藻类生长速度减慢。(4)低氧通气。该数值模型包括基于DYRESM的储层模型、双羽流循环模型、营养物模型和4种藻类的生物过程，对这些机理进行了验证和评价。首先，模拟了几个实验结果，说明了运行过程中藻类生物量的变化过程。然后在不同的边界条件下进行计算，参数化成功和不成功的操作条件。其次，对最有效的脱层条件进行了参数化，结果表明，目前的脱层能耗不超过10%。由于重要的结构不仅是藻类生物量的减少，而且是蓝藻优势向可食用物种的转变，最终改变整个生态状况，因此这种自下而上的效应将是关键点。因此，我们对几个湖泊和水库进行了实地调查，以了解食物网的机制。此外，还建立了一个简单的食物网模型，包括浮游动物和两种鱼类等高级捕食者。