The Economic Impact of Eutrophication

People living around Lake Chao Hu use the lake’s resources to provide an income.  Not only does the current ecological situation restrict fishermen from making a living, it also negatively affects tourism.  

Source: <http://www.chinadaily.com.cn/china/2009-07/09/content_8404343_3.htm>

Source: <http://english.anhuinews.com/system/2010/05/28/003017037.shtml>

Fishermen do not get large catches anymore because most of the fish are already dead.  Even if they are able to catch any fish, it is recommended that they do not consume it or sell it.  A study by Xie et al. reveals that “one hundred grams of fish muscle would contain...about 1.3-25 times the recommended tolerable daily intake of MC-LR by humans” (293).  MC-LR describes cyanotoxins, toxins which can “cause allergic or respiratory issues...or affect the nervous system in mammals, including humans” (USGS: Science for a Changing World).   It is suggested that people do not drink water or eat fish from the lake.  However, this puts residents of China’s Anhui Province in a complicated situation.  They need an income and they need food.  


In 2008, the government responded to people’s concerns by lowering the amount of industrial waste they discharged into the lake by 70% when compared to the amount of waste in 2005 (“Chao Hu Lake faces imminent algae outbreak”).  This is a good step, since urban sewage, one of the biggest contributors of excess nutrients into the lake, was causing eutrophication and making the water unsuitable for drinking. Also, China Daily reports that algae-eating fish were released into the lake.  If the fish can eat faster than the algae blooms and destroys their oxygen source, they can succeed in diminishing algae populations. However, this might be more of a temporary solution. Essentially, the lake will not fully recover or be able to maintain a healthy state unless it is protected against urban runoff.

While the government is taking steps to stop eutrophication, it needs to ensure that this does not occur again in the future.  Despite their current efforts, algal blooms affect the lake during the summer. It is necessary to protect the lake because it is the livelihood of many people. Therefore, long term solutions should also be considered. In addition to present efforts, the government should place stricter regulations on industry, find an eco-friendly alternative to fertilizers, and invest in infrastructure that can support the larger population sizes.  Furthermore, a set of quality standards similar to the Clean Water Act in the United States should be used to keep the lake in good condition. With enough planning, the cities around Lake Chao Hu will be able to use the lake's resources and enjoy a growing economy while ensuring that the lake is fishable, drinkable, and swimmable.

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.

Urbanization Affects Aesthetic Quality of Lake

Lake Chao Hu, valuable for its aesthetic quality, attracts tourists.
 Source: <http://www.absolutechinatours.com/china-travel/Five-Great-Lakes.html>  

Lake Chao Hu, the fifth largest lake in China attracts visitors who generate financial income for the local economy.  The video below, found on Youtube, demonstrates a family enjoying their visit to this beautiful aquatic ecosystem.  

Found: http://www.youtube.com/watch?v=wkx5VsulHkk

It is clear that in its pristine form, Lake Chao Hu can develop into a spot for ecotourism.  However, the effects of eutrophication must first be combated.  

Visible algal blooms reduce the lake's aesthetic quality and lower the prospects of tourism.
Source: <http://www.chinadaily.com.cn/china/2007-06/12/content_892212_2.htm>  

One might ask oneself how the lake became so polluted.  While many factors led to the lake's detriment, urbanization is perhaps the largest factor.  Larger numbers of people, now living in urban areas near the lake, place a larger demand on the ecosystem than they did  in previous years.  It is no surprise that "with the urbanization rate increasing from 17.4% in 1978 to 44.9% in 2008," inadequately treated sewage is disposed into the lake (Zhao v).  The city's infrastructure simply cannot support all the extra waste of a population larger than the one it was designed for.  In a study, Zhang, Liang, and Wang report that "urban sewage input from local urban regions [around Lake Chao Hu are] suspected of being the major source responsible for the pollution" (362).
The link below provides a map that shows population density within China.  In comparison to other regions, the south-east region, in which Lake Chao Hu is located, has a high population density, at about 250 people per sq. meter.

http://www.atozmapsdata2.com/downloads/Regional/Modern/R-ASIA-Pop.pdf

This map shows where Lake Chao Hu is located.

Liu et al. include this map in their study "Human-induced change in sedimentary trace metals and phosphorous in Chaohu Lake, China, over the past half-millennium."  Other interesting graphs that they present show levels of heavy metals and phosphorus in the Nanfei River mouth, which deposits water right into Lake Chao Hu.

This graph shows the accumulation rates of heavy metals and  phosphorus  found in core samples the research team took in 2007 from the Nanfei River. 

These graphs show the concentration of metals and phosphorus.  Furthermore, it demonstrates that the elements have high enrichment factors.

Liu et al. state that low enrichment factors, or EFs should be between 0.8 and 1.1 (1).  The graphs (b) and (d) show that Lead, Zinc, and Phosphorus exceed this range, and pose a problem.  These nutrients enrich the lake and cause eutrophication.  Since they are found in the river mouth, it suggests that urban areas further from Lake Chao Hu are also affecting it.  Perhaps the numbers are even higher within the lake itself.  Unlike the free-flowing river, the lake cannot move and therefore has a harder time in filtering out these pollutants.  All this adds up and aggravates the process of eutrophication.