Team:GenetiX Tec CCM/Description
About Xochimilco & Why is important for us
Xochimilco, meaning the fertile land of flowers, is one of the 16 delegaciones, or boroughs in Mexico City. Located 28 km south of the city and just about 5 km from our high school in the formerly independent city of Xochimilco, it is characterized by the fact that, although there have been changes: “they have not affected [Xochimilco’s] overall structure and functional integrity” (UNESCO.org, 1989) Meaning there is constant preservation of its pre hispanic origins, alongside the use of artificial islands known as chinampas. Furthermore, its most distinguishing feature are the canals, left from an extensive lake and canal system that connected many of the settlements in the area known as the Valley of Mexico. However, Xochimilco and its surrounding area face important threats related to their geological and social situations, with threats such as: “development pressures, changes to land use, abandonment and contamination” (UNESCO.org, 1989) .
Xochimilco is home to many endemic species of flora and fauna, with one of the most important being the critically endangered Ambystoma mexicanum, better known as the axolotl. With the purpose of saving the remaining canals, Xochimilco was declared a World Heritage Site in 1987. Nonetheless, the deterioration of the canals has been happening so fast, that UNESCO has threatened to take away the World Heritage Status from Xochimilco. Because of this, it is quite important to raise awareness of the meaning Xochimilco has to Mexico and the world as a whole, and strategies should be implemented to stop it from being destroyed.
What is the problem in Xochimilco?
Xochimilco is an important zone in México City´s economy. Around 396,852 people live here. People are in improper conditions of settlement. Approximately 14% of the houses are a single room or with ground floor. The zone also has a lack of a drainage system which gives an average amount of more than 30,000 faeces downloads per day are discharged directly into the canals. This brings an enormous increase of the pollution of water. The added nutrients on contaminated water causes water lily to atrophy the channels. Lily roots and attacks the endemic trees of the place: the ahuejote, used to create and settle chinampas. Covered lily channels prevent the path to the chinampas, which are abandoned as agricultural production premises; they urbanize and create more wastewater discharges. Those factors contribute to a reduction in the production of crops and animals of the small businesses of the area which are one of the most important activities in the zone considering that from 2.64% of the land is bestow for industry and 15.50% for agriculture. Even causes the proliferation of bacteria, protozoan cysts and viruses, among other pathogens that lead to health repercussion on the residents.
The main source of environmental impact in Lake Xochimilco is eutrophication: a process triggered by an excess of nutrients, such as phosphates and nitrates. Under these conditions, photosynthetic organisms (microalgae, algae, and vascular plants) develop ideally, thus incrementing their population. This spontaneous bloom increases phytoplankton, limits light penetration, and reduces dissolved inorganic carbon –raising pH levels. Furthermore, when the algal population eventually dies, microbial decomposition severely depletes dissolved oxygen levels. As a consequence, an anoxic zone is created, which lacks enough oxygen to support life. The last stage of this process is characterized by the prevalence of anaerobic microorganisms that produce malodorous gases (sulfur, methane, ammonia, etc.) that react with water to form acids.
In Xochimilco’s particular case, eutrophication is denominated as anthropogenic, because it is caused directly by human activities. Principally, the over-fertilizing circumstances are due to residual water discharges from houses and industries near the lake. Evidently, this breaks up the naturally built balance between “the nutrient production from organic matter decomposition and its assimilation by primary producers” (Chapa et Guerrero, 2010), in addition to introducing pathogenic and invasive microorganisms to the ecosystem. Since this actions are what have led to origination of the currently present anoxic conditions, it is important to cease them in order to reach its full recovery.
Xochimilco’s ecological problems are multidimensional. The generally poorly-managed control over regulations regarding sewage and garbage disposal in the lake and canals of Xochimilco are the principal source of many of these problems, such as the previously mentioned anthropogenic eutrophication. This in turn has put a wide range of endemic species in danger.
One of the consequences of the eutrophication in the lake is particularly present in the overpopulation of Nymphaea (water lilies), which is held responsible for draining a great amount of the available oxygen in the water. When researching for possible solutions involving genetically modified organisms, our team came across a wide range of possibilities, which had different levels of viability and potential implementation. After the brainstorming, it became clear that one of the biggest areas of opportunity to fight the canal’s problems was to reduce the amount of Nymphaea specimens within its waters, which left us with the question of how to do so without damaging the ecosystem as a whole.
Through research and analysing different ideas, We reached the conclusion that biosynthesizing pesticides to fight against the elevated number of Nymphaea in the canals was rather counterproductive, due to the fact that it would be extremely hard to predict and therefore control the way the pesticide would affect wildlife in general outside of the desired area of effect (reducing the population of water lilies living in the lake and canals). With this is mind, we decided to focus our efforts on reducing the number of available nutrients occasioning the overpopulation of Nymphaea, such as nitrates and nitrites, nitrogen based compounds that are recognized as one of the main factors in causing eutrophication. To do so, our aim is to create a bacteria capable of conducting a process called denitrification under specific conditions inside Xochimilco’s canals, and hence able to of regulating the levels of NO-3 and NO-2 in the water.