Team:Peking/FieldInvestigations

Taihu Algal Bloom

Over 80% of fresh water lakes in China are under threat of algal blooms, including the five largest ones. Algal blooms burst annually in these lakes, harming ecosystem and industries, affecting citizens’ normal lives. Fresh water is the fundamental needs of our life, but now it has been being in scarcity.

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

We encountered many problems during experiments, especially how to compare traditional methods against algal bloom with ours. As a result, 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 this summer (Fig. 1). We interviewed researchers and citizens, exploring the mechanism of algal bloom occurrence and existing anti-bloom treatments(discussed below). Furthermore, we got first-hand information of public opinion to algal blooms.

Taihu Lake lies in the southeast area of China, adjacent to Jiangsu Province and Zhejiang Province (Fig. 2). As the third biggest lake 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.

Since 1987, algal bloom has become a serious concern in Taihu Lake due to increasing 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 seriously 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 the "Taihu environmental governance" proposal. In the same year, regional governments of Jiangsu, Zhejiang, and Shanghai along with State Council launched "Focus on Taihu without tolerance" movement in the end of 1998. Although the officials announced the "basically accomplish governance objectives", 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.

In 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 was a typical case that algal bloom affects citizens’ daily lives: In June 2007, due to continuous south wind and high temperature, a huge amount of cyanobacteria accumulated around the north lakeshore of Meiliang Gulf, which was near the intake of waterworks in Wuxi, causing the 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 of doing heatstroke prevention via television and newspaper. However, the real emergency was ignored. In May 28^th, citizens claimed that water flowing from their taps is smelly, and then they received the reply saying that there is nothing wrong with it. One day later, almost all the citizens in Wuxi lost fresh water supply. Bottled water sold out within hours, even twice more expensive than usual (Fig. 3). Many parents chose milk instead of water as their children’s drink.

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. The concentration of Chlorophyll in water body overreached 40µg /L, and even over 170 µg /L in some areas. Eliminating algal bloom in Taihu seems to be beyond control.

According to statistics, algal bloom occurs in Taihu Lake every summer since 1987. After 2000, aggravating eutrophication and climate changes caused algal blooms to gradually become a serious environmental issue more than an eyesore.

By far, Taihu Lake, as well as many other fresh lakes all over the world, is still suffering from algal 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 formation, and they pointed out that the burst of cyanobacteria is not a sudden event but a result of long-term accumulation.

In July 22^nd, Prof. Kong Fanxiang gave a report on algal bloom to Peking iGEM 2014. (Fig.4&5)

In the reporting process, Prof. Kong introduced overview of lakes in China, lake eutrophication in China, interactions between cyanobacteria and lake eutrophication, and the most important part is the four-phase development hypothesis on the process of the cyanobacteria bloom formation.

At present, there are more than 24800 lakes in China, 2800 of 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 in 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 algal bloom in Taihu Lake, Prof. Kong and his fellows raised the four-phase development hypothesis on the process of the cyanobacteria bloom formation, 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 are different factors influencing the growth state of cyanobacteria in each phase. In dormancy phase, low temperature and illumination limit the growth of cyanobacteria. Though people do not fully understand the mechanism, influencing 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 algal bloom is largely influenced by meteorological condition, especially temperature. However, 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 algal bloom, which can be divided into physical, chemical, and biological methods roughly.

Physical Methods:

The easiest method, also the most common one, is mechanical salvage.(Fig. 6) This method hardly has side effects on environment. However, it is inefficient, labor-consuming and costly. Furthermore, toxins such as microcystin dissolved in water threaten the workers’ health.

There are some other physical methods like ultraviolet(UV) radiation, ultrasonic cracking, but they are also too costly.

Clay flocculation is another physics method controls harmful algal blooms. (Fig. 7&8) 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 km² at a loading rate of 400 g/m². Removal rates of Cochlodinium polykrikoides were calculated at 90% to 99% up to 2m depth, with virtually no reported mortality in the caged fish due to clay treatment.

A critical defect of this method is that clay cannot kill cyanobacteria, which remains the possibility of refloating of them, especially in 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) can damage Microcystis aeruginosa colonies. These toxins increase the influx of potassium and decrease the uptake of sodium, which disrupts the metabolism of cyanobacteria, especially the intracellular pH. But because of the potential harm to other organisms in lakes, chemical methods can only be taken in some special occasions, such as, in a small close fishpond.

At present, 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, and degrade chemical compounds into small harmless molecules meantime.(Fig. 9)

Another widely-used method is dumping copper sulfate or other copper compounds^[3] into water. Copper can replace magnesium in Chlorophy ll, blocking photosynthesis in cyanobacteria. However, copper can also disrupt other organisms’ metabolism while it is detrimental to algal blooms. Therefore, these compounds are hardly used now.

Biological Methods:

Introducing competitors(like emerged plants) (Fig. 10)or predators(like algicidal bacteria) seems to be an ideal method. However, the common shortcoming in most experiments on preventing cyanobacteria 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 cyanobacteria growth. Complex ecological technologies that imply a combined use of inexpensive physicochemical and biochemical techniques, which 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 cyanobacteria, and we introduced an cyanobacteria-binding protein and gas vesicle to improving the efficiency of killing. At the same time, one of the toxins produced by M. aeruginosa, microcystin, was degraded by a peptide enzyme. At last, suicide system of our project prevent biosafety problem. 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 algal bloom. The detailed introduction can be found on the project pages.

Public Opinions

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 most of China is less than 50%. GDP in this area was 2864.8 billion yuan in 2013.

Researchers are more disappointed about when to face the fact that hundreds of billion yuan has been spent but the environmental problems have not been improved in Taihu Lake.

In a 2007 report, Liu Guangzhao, a 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 obstructs 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 interest-related groups. 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 are 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.

Conclusions

During the interview with researchers in NIGLAS and Taihu, we presented our project and received many suggestions. (Fig. 11)

"Ranger amongst enemies" uses molecular assays to eliminate large-scale algal bloom. Comparing traditional methods, our project proposes a wholly new view of dealing with algal 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 covers almost all the harm of algal blooms is proposed and biosafety is specially considered. Hence, we choose a bactericidal enzyme without harm to other higher animals and plants, which keeps the selectivity of our project and averts the disadvantages of traditional chemical methods. In addition, a suicide system prevents the leakage of modified genes, which is a must for all engineered organisms. High efficiency is another highlight of our method. It is estimated that algal bloom will disappear within 3 days in a ten thousand square pond by modeling and small-scale experiments confirmed our model’s reliability. Comparing with traditional physical and biological methods, our "Ranger amongst enemies" is a shortcut of annihilating algal bloom.

Researchers gave high praise to our project, commenting it can potentially replace current methods. The most noticeable point of our project is that it gives a new way of thinking on algal bloom governance. After tens of years working, there is an urge request for some new ideas against algal bloom. To some extent, "Ranger amongst enemies" is what we are looking for. Though immature, we believe that 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.