基于MODIS数据的2000～2013年洞庭湖水华暴发时空分布特征

Characteristics of Spatial and Temporal Distribution of Water Blooms Outbreak in Dongting Lake based on MODIS Data

洞庭湖蓝藻水华直接威胁着洞庭湖流域的生态安全和沿湖居民的生产、生活。利用2000~2013年期间长时间序列中分辨率成像光谱仪(moderate-resolution imaging spectroradiometer,MODIS)影像数据,通过计算水体的漂浮藻类指数(floating algae index,FAI),提取洞庭湖水华信息,系统分析洞庭湖水华暴发的时空分布特征。结果表明,过去14 a的洞庭湖水华面积相对稳定,虽然面积在减少,但无显著变化趋势;洞庭湖水华年内暴发呈典型的双峰特征,暴发时间主要集中在4~8月;洞庭湖水华主要发生在东洞庭湖的大小西湖地区,在其他地区尚未发现大面积水华;大小西湖水华暴发以小频率为主,但持续时间较长,尤其在2003年、2004年、2005年、2008年和2013年,基本常年都有水华现象存在。

Cyanobacteria bloom in Dongting Lake is not only a direct threat to ecological security in Dongting Lake basin but also threat to the production and life of residents along the lake. Time series from2000 to 2013 of MODIS image data were used to extract blooms information and characteristics of spatial-temporal distribution of water blooms outbreak in Dongting Lake were analyzed systematically by calculating the value of floating algae index. The results showed that during the past 14 years, the water blooms area was relatively stable in Dongting Lake, although there was a trend to decrease, but not significantly; water blooms outbreaks in every year presented the double hump and the outbreaks were mainly concentrated in from April to August; water blooms occurred mainly in Large-small West Lake in the east part of Dongting Lake and the other areas were not discovered. The water blooms in Large West Lake and Small West Lake broke out mainly in small frequency, except for in 2003, 2004, 2005, 2008 and 2013, in which blooms existed basically all year round.