What is happening in Lake Chao Hu?

Lakes and other aquatic ecosystems can usually maintain a healthy ecosystem on their own, but sometimes the stress caused by anthropogenic factors presents a burden that cannot be easily carried by lakes or rivers.  Lake Chao Hu, a once pristine lake in the Anhui Province of China, experienced its first algal blooms in the 80’s.  During this time, algae populations increased rapidly, later leading to eutrophication within the lake, as a result of anthropogenic, or human caused, factors.  The algal blooms were a direct result of urban runoff, like fertilizer, and the “discharge of sewage without adequate treatment into the lake” (Wang, Zhang, and Liang 362).  Combined, these elements spewed large amounts of nutrients into the water.  
After those events, Lake Chao Hu underwent changes characteristic to eutrophication.  Eutrophication often starts because large amounts of nutrients, specifically nitrogen and phosphorous, create ideal conditions for algal blooms.  When algae increases rapidly in population, it uses a lot of oxygen for biological processes like digestion, respiration, and decay.  After a while, the algae uses up most of the dissolved oxygen in the freshwater lake.  Consequently, aquatic life suffers.  Fishes, no longer able to obtain enough oxygen to survive, die.  In addition, the algae continues to thrive and forms a layer on top of the lake, blocking out sunlight and making it difficult for low lying aquatic plants to reach the sunlight they need for photosynthesis.  Without food or oxygen, fish populations decline.  

This image details the process of natural eutrophication in lakes.  Lake Chao Hu underwent a similar process, except the sources of nitrogen and phosphorous were anthropogenic and not natural.  

This chain of events harms not only the aquatic life within the freshwater lake, but also the people who depend on it for clean drinking water, fishing, and tourism.  

Unfortunately, algal blooms intensify in Lake Chao Hu every year around summertime.  ChinaDaily reports that “Chaohu is frequently hit by blue algae outbreaks between June and September” (“Chaohu Lake faces imminent algae outbreak” 1).  This means that the government must seek a permanent solution to these problems, unless it wants Lake Chao Hu to experience algal blooms every summer, leading to economic and environmental stress within the region.

Works Cited

“Chaohu Lake faces imminent algae outbreak.” China Daily 7 Sep. 2009: 1-4. Web. 27 Nov. 2012.  

Zhang, Kai, Bo Liang, and Ji-Zhong Wang. “Tracing urban sewage pollution in Chaohu Lake (China) using linear alkylbenzenes (LABs) as a molecular marker.” Science of the Total Environment. Jan. 2012: 356-63. Science Direct. Web. 26 Nov. 2012.