Team:Peking/FieldInvestigations

Taihu Water Bloom

Over 80% fresh water lakes in China are under threatens of water blooms, including the five biggest ones. Algal blooms burst annually in these lakes, harming ecosystem and industries, affecting citizens’ ordinary lives. Fresh water is the fundamental basis of our life, but now it has to be suffering.

Besides China, many countries also regard water blooms as a serious concern as the result of its scale and hazard. For instance, Erie Lake in North America experienced an enormous water bloom in 2011. The area conquered by cyanobacteria once reached nearly 2000 square miles. Residents around were warning due to the high concentration of Microcystin from dead algae.

This summer, Peking iGEM Team went to NIGLAS (Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences) in Nanjing and Taihu Limnology Ecology Observatory in Wuxi (Fig. 1). We interviewed researchers and citizens, exploring the mechanism of algal bloom occurrence and existing anti-bloom treatments (discussed below). Further more, we got first-hand information of public opinion to water blooms.

Taihu Lake lies in the southeast area of China, adjacent Jiangsu Province and Zhejiang Province (Fig. 2&3). As the third biggest lakes in China, Taihu Lake covers 2427.8km², and has a 393.2 km long shore. Taihu Lake is big but shallow, with an average depth of 1.89m.

From 1987, water bloom began to become a serious concern in Taihu Lake due to gradual eutrophication. It bursts year after year in Taihu Lake, and there seems to be no end of it. Up to now, more than 80% of the water body has been heavily eutrophicated.

China government has done much to reverse the exacerbation of environment in Taihu basin area. Nevertheless, things seldom go under men's willing.

In 1991, the first phase of Taihu Decontamination Project was launched by government, hundreds of billions yuan was spent afterwards.

In 1998, government approved "Taihu environmental governance". The same year, regional governments of Jiangsu, Zhejiang, and Shanghai along with State Council launched "Focus on Taihu without tolerance" action in the end of 1998. Although officially announced the "basically accomplish governance objectives", but public doubt never ends.

In 2005, the second phase of Taihu Decontamination Project was started. It is calculated that only 1% water body was polluted in early 1980s, but more than 80% water body was polluted at that time.

In 2007, after the Water Crisis in Wuxi, Jiangsu Province government spent 2 billion yuan as a special fund on Taihu governance. From 2007 to 2011, 2.8 million tons of cyanobacteria were collected from Taihu Lake.

May 2008, a plan was raised by regional governments, aiming to improve Taihu water quality from class V to class IV before 2020, with an expecting cost of 111.5 billion yuan.

Statistic from decades shows the need of fresh water from Taihu basin is approximately 37 billion m³ per year, while Taihu can only supply 17.7 billion m³. The gap is obvious.

Wuxi water crisis is a typical case that water bloom affects citizens’ daily lives: June 2007, due to continuous south wind and high temperature, a huge amount of cyanobacteria accumulated around the north lakeshore of Meiliang Gulf, where near the intake of waterworks in Wuxi, causing lack of fresh water for 2 million citizens for a week.

In the end of May, temperature in Wuxi reached a historic level. Government reminded citizens doing heatstroke prevention via television and newspaper. However, the real emergency was ignored. 28th, May, many citizen claimed that water flowing from their taps smelly, and received the reply saying that there is nothing wrong with it. One day later, almost all citizens in Wuxi lost fresh water supply. Bottled water sold out within hours, even twice more expensive than usual (Fig.4). Many parents chose milk instead of water as their children’s drinking.

To our surprise, the government didn’t cut off water supply, neither nor warning citizen the potential danger.

A week after the cyanobacteria burst, monitoring data showed another burst in Meiliang gulf. Chlorophyll a concentration overreached 40µg /L, some areas over 170 µg /L. Eliminating water bloom in Taihu seems to be beyond control.

According statistics, water bloom occurs in Taihu Lake every summer since 1987. After 2000,aggravating of eutrophication and climate changing lead to that algal blooms gradually become a serious environment issue more than an eyesore.

Now, Taihu Lake, as well as many other fresh lakes all over the world, is still suffering from water bloom.

Development

Professor Kong Fanxiang in NIGLAS (Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences) and his fellows raised the four-phase development hypothesis on the process of the cyanobacteria bloom forming, and they pointed out the burst of cyanobacteria isn’t a sudden event but a result of long-term accumulation.

22ndJuly, Prof. Kong Fanxiang gave a report on algal bloom to Peking iGEM 2014.(Fig.5&6)

During the report, Prof. Kong introduced overview of lakes in China, lake eutrophication in China, interactions between cyanobacteria and lake eutrophication. The most important part is that the four-phase development hypothesis on the process of the cyanobacteria bloom-forming.

Presently there are more than 24800 lakes in China, 2800 within which span more than 1 km². Unfortunately, four-fifths of them are in eutrophication state, including almost all lakes in North China area and middle/lower reaches of Yangtze River.

Algal bloom is the result of a variation of vertical position of large volume of algal biomass that is gradually developed and accumulated for long time. According to the ecological theory and the in situ observation of the water bloom in Taihu Lake, Prof.Kong and his fellows raised the four-phase development hypothesis on the process of the cyanobacteria bloom-forming, which divided life span of cyanobacteria mainly by meteorological conditions: dormancy in winter, recruitment in spring, growth and float to the water surface in summer and sink to the sediment in autumn.

There is different factors influence the growth state of cyanobacteria ineach phase. In dormancy phase, low temperature and illumination limit the growing of algae resulting in dormancy. Though not fully understand the mechanism, factors can be determined as following: low temperature and illumination in dormancy phase; temperature and dissolve oxygen recruitment phase; nutrient growth and float phase; and temperature sink phase.

We could learn that water bloom is largely influenced by meteorological condition, especially temperature. Unfortunately, controlling temperature in Taihu scale is impossible for today’s technology. We must find other ways to regulate growth of cyanobacteria.^[1]

Existing treatments

People do have several methods to fight against water bloom, and they can be divided into physical, chemical, and biological roughly.

Physical methods:

The easiest method, also the most common one, is mechanical salvage.(Fig.7&8) This method hardly has side effects on environment. However, it is inefficient while money and labor wasting. Furthermore, toxins such as microcystin dissolved in water threaten workers’ health.

There are some other physical methods like ultraviolet (UV) radiation, ultrasonic cracking. But they all cost too much money.

Clay flocculation is another physics method controls harmful algal blooms. (Fig.9&10) There are several successful examples in Japan and Korea.

In a 1996 report^[2], workers in South Korea dispersed approximately 60,000 tons of dry yellow loess (a kaolinite-bearing sediment) by barges over 260 k㎡at a loading rate of 400 g/㎡. Removal rates of Cochlodinium polykrikoides were calculated at 90% to 99% up to 2 m depth, with virtually no reported mortality in the caged fish due to clay treatment.

A remarkable weakness of this method is that clay cannot kill cyanobacteria, which remains the possibility of refloating of them, especially for big but shallow lakes like Taihu Lake(average depth 1.89m) in China and Victoria Nyanza in Africa.

Chemical methods:

Tin- and chlorine- containing toxic compounds(biocides) could damage Microcystis.aeruginosacolonies. These toxic increased the influx of potassium and decrease the uptake of sodium, which is necessary to keep the metabolism of cyanobacteria, especially maintaining intracellular pH. But because of the potential harm to other organisms in lakes, chemical methods can only be taken in some special occasions, a small close fishpond for example.

Now, most chemical methods are used in waterworks treating water taken from natural resources to eliminate organisms and chemical compounds. Strong oxidation can kill almost all organisms in water, including cyanobacteria consequently, while degrading chemical compounds into small harmless molecules.

Another assay that was widely used is launching copper sulfate or other copper compounds^[3]. Copper can replace magnesium in Chlorophyll, blocking photosynthesis in cyanobacteria. However, copper can also harm other organisms’ metabolism while inhibiting water blooms. Therefore, these compounds are hardly used now.

Biological methods:

By introducing competitors (like emerged plants) or predators(like algicidal bacteria) seems to be a ideal method. However,

“The common shortcoming in most experiments on preventing microcystis growth is the lack of preliminary calculations and an analysis of the results of long-term monitoring of hydrobiological, hydrochemical, and hydrophysical characteristics of water. Mathematical modeling is seldom used, although it is important for predicting the results of action on microcystis growth. Complex ecological technologies that imply a combined use of inexpensive physicochemical and bio- chemical techniques that do not affect ecological norms have almost completely been ignored.” ^[4]

To avoid disadvantages of existing methods, we carefully designed a transgenic E.coli and did a lot of modeling analysis. Lysozyme was chosen as the weapon to eliminate algae, and to get an ideal effect we added two improvements: binding protein and gas vesicle. At the same time, cyanobacteria toxin Microcystin was degraded by a peptide enzyme. Last, suicide system of our project prevent biosafety. Peking’s project decontaminates cyanobacteria via molecular perspective, and synthetic biology assays were applied to quantitatively measure data. Considering what have been done in the summer, it is supposed to be a promising method against water bloom. The detailed introduction can be found on the project pages.

Public Opinion

Taihu Lake basin area, with a population of 49 million people, is one of the most developed, energetic areas in China. Urbanization rate of Taihu Lake basin area is over 70%, while which of China is less than 50%. GDP in this area was 2864.8 billion yuan in 2013.

Researchers are more disappointed about when facing the fact that hundreds of billion yuan has been spent but nothing was improved in Taihu Lake, even worsen.

In a 2007’s report, Liu Guangzhao, member of World Water Association, and Liu Zhili, professor involved in algae research in Nanjing University, shared the view that pollution in Taihu lake could be eliminated within 5 years. Honestly speaking, there is no obstacle technically while the main obstacle is from the management system.

This report listed 5 serious shortages in Taihu Lake governance.

Technically speaking, pollution in Taihu could be controlled within several years. However, management system inhibits the decontamination.

Only 1/10 of spent money is enough for the decontamination once the problems in management were solved.

The “863” plan was operated by the interest-related. They made decisions on which project is to be invested, who is to be the project leader, and how effective the projects are. Those projects that really work cannot get enough research funds.

Using salvage, instead of other advanced approaches, as the main method in cyanobacteria treatment.

Unprecedented is the concerns from states leaders, the enormous cost, and the ineffectiveness.

Taihu basin area accounts for only 0.4% of Chinese land area, but with 4% of the country's population, creating 13% of the GDP. This imbalance is bound to cause the contradiction between the river basin development and ecology protection. Management mechanism of chaos intensifies the grim situation of pollution in Taihu. 7 years pasts, what is the actual situation in Taihu?

Up to now, eutrophication in Taihu Lake has been eased. Water quality in 15 rivers inflowing into Taihu Lake is above class 4(which means industrially useable), comparing 9 rivers’ water quality is worse than class 5(which mean agriculturally useable) in 2007.

According Zhang Min, deputy director of the office of Taihu in Jiangsu Province, eutrophication in Taihu is a long-term outcome and cannot be changes in a relative short time. Marginal benefits reduced greatly in recent years, which leads to greater difficulties in improving Taihu Lake water quality. Notably, heavy industry is still a big proportion of industrial structure of Taihu Basin Area, and the total discharge of pollutants still exceeds the environmental capacity.

Conclusion

During the interview of researchers in NIGLAS and Taihu, we presented our project and received many suggestions.(Fig.13)

"Ranger amongst enemies" uses molecular assays to eliminate large-scale water bloom. Comparing traditional methods, our project provides a whole new view of dealing with water bloom. We endow our ranger E.coli weapons (lysozyme), improvement equipment (binding protein and gas vesicle), and a suicide system. Synthetic biology was used to engineer desired organisms.

Firstly, an integrated method that included near all aspects of harm from water blooms. Biosafety was specially considered.We chose an anti-microbe peptide without side effect on other organism, which keeps the selectivity of our project and avoid disadvantages of traditional chemical methods. Forwards, a suicide system prevents the leakage of modified genes, which is a must for any engineered organisms. Efficiency is another highlight of our method. It is estimated that water bloom would disappear within 3 days in a ten thousand square pond by our model and small scale experiments confirmed model’s reliability. Comparing physics or biological methods, "Ranger amongst enemies" is a shortcut

Researchers gave high praise to our project, commenting it can potentially replace methods today. The most noticeable point of our project is that it gives a new way of thinking on water bloom governance. After tens of years working, there is an urge request for some new ideas against water bloom. To some extent, "Ranger amongst enemies" is what we are looking for. Though immature, we believe our project opens another door leading to the balance between man and nature.

References

[1] Kong, F., Fao, G. (2005). Hypothesis on cyanobacteria bloom-forming mechanism in large shallow eutrophic lakes. Acta ecologica sinica/Shengtai Xuebao, 25(3), 589-595.

[2] Sengco, M. R., Anderson, D. M. (2003). Controlling harmful algal blooms through clay flocculation. The Journal of eukaryotic microbiology, 51(2), 169-172.

[3] Anderson, D. M. (2009). Approaches to monitoring, control and management of harmful algal blooms (HABs). Ocean coastal management, 52(7), 342-347.

[4] Kolmakov, V. I. (2005). [Methods for prevention of mass development of the cyanobacterium Microcystis aeruginosa Kutz emend. Elenk. in aquatic ecosystems]. Mikrobiologiia, 75(2), 149-153.