| 摘要: |
| 本研究结合卫星遥感影像和机器学习的分类方法，监测到邛海在2022年2-3月发生了罕见的大面积藻类水华，初步从气温、风速、营养盐和水生植被分布等角度探究了此次藻类水华大范围暴发的可能原因。遥感监测显示，2022年2月18日，邛海开始出现水华，随后水华覆盖面积逐渐增大，到3月10日，水华达到最大面积13.67 km2（占总水面面积50.63%），此后面积逐渐降低，3月19日开始没有监测到明显的水华。基于模拟数据发现邛海在1985-2022年间，湖泊增温速率为0.14℃/十年，并且水温和水生植被的面积呈现明显负相关（R2 = 0.19, P < 0.05）。相比于2000年代，2010-2020年邛海氮磷营养盐浓度没有明显上升且波动幅度变小。但水生植被，尤其是沉水植被发生了大面积的退化，水生植被面积每十年约减少0.19km2，沉水植被每十年约减少0.10km2。分析表明，从宏观来看，在气候变化、水位上升的多重胁迫下，水生植被加剧退化，浮游植物更容易取得优势地位。2022年2-3月气温快速上升，风速较低且缺乏降雨等气象条件也有利于藻类水华的形成，水温持续性上升促进了水体分层，为浮游植物生长提供了有利条件。但邛海偶发性的大面积藻类水华形成的深层次原因还需进一步的探究。在未来气候变化情景下，对于邛海这类相对清洁的水体，藻类水华风险也将持续存在并值得高度关注。 |
| 关键词: 邛海 水华 沉水植被 |
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| Occasional algal blooms in Lake Qionghai, a mesotrophic lake: remote sensing extraction and the preliminary investigation of their causes |
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He Shiwen, Zhang Yunlin, Li Na, Luo Juhua
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Nanjing Institute of Geography Limnology,CAS
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| Abstract: |
| This study utilized a combination of satellite remote sensing imagery and machine learning classification methods to monitor a rare large-scale algal bloom event in Lake Qionghai during February to March 2022. Preliminary investigation into the possible causes of this widespread algal bloom event was conducted from the perspectives of temperature, wind speed, nutrient levels, and aquatic vegetation distribution. Remote sensing monitoring revealed that on February 18, 2022, algal blooms began to appear in Lake Qionghai, with the bloom area gradually increasing. By March 10, the bloom reached a maximum area of 13.67 km2 (accounting for 50.63% of the total water surface area), after which the area gradually decreased, and no significant algal blooms were observed since March 19.
Based on simulated data, it was found that Lake Qionghai experienced a warming rate of 0.14 °C per decade between 1985 and 2022. Furthermore, there was a significant negative correlation (R2 = 0.19, P < 0.05) between water temperature and the area of aquatic vegetation. In comparison to the 2000s, the nitrogen-phosphorus nutrient concentrations in Lake Qionghai did not show a significant increase and exhibited reduced fluctuations from 2010 to 2020. However, extensive degradation of aquatic vegetation, especially submerged vegetation, was observed, with the area of aquatic vegetation decreasing by approximately 0.19 km2 every decade and submerged vegetation decreasing by 0.10 km2 every decade.
Our analysis suggests that from a macro perspective， under the multiple stressors of climate change and rising water levels, the degradation of aquatic vegetation exacerbates, favoring the dominance of phytoplankton in Lake Qionghai’s ecosystem. The rapid increase in temperature, low wind speeds, and lack of rainfall during February to March 2022 also facilitated the formation of algal blooms in Lake Qionghai. The sustained increase in water temperature promotes stratification of the water column, which also provides favorable conditions for the growth of phytoplankton. However, the causes of the occasional widespread algal bloom formation in Lake Qionghai require further investigation.
Under future climate change scenarios, algal bloom risks will exist in relatively clean water areas like Lake Qionghai, warranting continued attention. |
| Key words: Qionghai algal bloom submerged vegetation |
