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Wednesday, March 22, 2023
GUATEMALA CITY, Nov 24 2009 (IPS) - A thick, chocolate-coloured scum floats on the normally clear blue waters of Lake Atitlán, in the southwestern Guatemalan province of Sololá, caused by agricultural fertilisers and untreated sewage from surrounding villages and farms.
Scientists identified the microorganism responsible as Lyngbya, a species of cyanobacteria (similar to blue-green algae) that has grown at a prodigious rate over the last few years, forming filamentous mats in the depths of the lake that end up floating to the surface.
It may also produce toxins with harmful effects on fish, crustaceans, aquatic plants and humans who come into contact with the polluted water.
“Cyanobacteria thrive on phosphorus and nitrogen, at the surface or in the depths of the lake, and in order to eradicate them both these elements must be prevented from entering the lake,” biologist Margaret Dix explained.
Cyanobacteria were first detected in the lake in 1976, although at very low levels. Now, however, they have grown into enormous surface mats, darkening its waters, because of the high levels of phosphorus and fertilisers in the lake, Dix told the Despacho Presidencial radio programme on the state broadcaster TGW.
A study carried out last year by the Institute of Agriculture, Natural Resources and the Environment (IARNA) at the Rafael Landívar University found that between 2002 and 2003, approximately 972 tonnes of nitrogen and 381 tonnes of phosphorus were added to the lake, which has no outlet.
While the present situation is regrettable because of the damage to the environment, it is not what most concerns the experts. “We also found contamination by Escherichia coli and other faecal bacteria, which trigger widespread diarrhoeal disease,” Pineda said.
This has dire consequences. In the lake basin area, the health system reported cases of diarrhoea in five percent of the population, totalling 9,322 cases in the period studied, according to the report.
In other words, sewage from at least 12 towns and villages surrounding the lake, and chemical fertilisers, have been feeding the growth of the cyanobacteria, to the point where this stunningly beautiful marvel of nature, which was a candidate in the “New 7 Wonders of Nature” contest, is on the verge of turning into a marsh.
Deputy Environment Minister Luis Zurita said a lake usually has an oxygen content of eight percent, whereas Atitlán has barely two percent, close to that of bogs or marshes which have an average level of one percent.
Juan Skinner, an environmentalist with the Lake Atitlán Environmental Protection Society (PRO-LAGO), told IPS that the problem is even more complex, because the lake’s ecology has been altered by the introduction of exotic fish, last done about 10 years ago.
Sea bass were introduced into the lake in 1968, and carp in the 1990s. They eat certain species that consume organisms which allow cyanobacteria to flourish, according to Skinner.
“Besides, the increase in nutrients (phosphorus and nitrogen) due to pollution has added to the ecological imbalance, producing the blooms of cyanobacteria,” he said.
One of the major concerns now is to determine whether the microorganism is toxic, since people living around the lake get their water supply from it.
Fortunately the first toxicity analysis of the cyanobacteria, carried out by the College of Agricultural and Environmental Sciences at the University of California, Davis (UC Davis), came back negative.
However, the local population is still being warned not to bathe in lake water, let alone drink it, while a second toxicity study is undertaken.
Meanwhile, the people of Sololá, most of whom are indigenous, bear the consequences of this environmental disaster. Joel Francisco Mendoza, the mayor of San Pedro La Laguna on the lakeshore, told IPS that one of their main problems now is their water supply, which they have traditionally taken from the lake.
Residents of San Pedro, and people from neighbouring municipalities, have had to find other water sources in order not to drink from the polluted lake.
But pollution is not a new experience for these villages.
Mendoza said San Pedro has no drainage system for waste water and sewage. “The way it works here is that every house has to make its own cesspit, and unfortunately there are many leaks, so that the material is inevitably discharged into the lake,” he said.
The cyanobacteria will also affect tourism, “because visitors hear of this news at once,” he said, while adding that whatever “is humanly possible” is being done. “We’re putting control measures in place and trying to clean up a bit,” he said.
Lake Atitlán, ringed by the San Pedro, Atitlán and Tolimán volcanoes, is one of the chief attractions in the country, and is visited by 20 percent of foreign tourists, according to the Guatemalan Institute of Tourism (INGUAT).
Faced with the environmental disaster in the lake, the government planned to take 32 urgent actions in six areas of work: agriculture, environmental hygiene, infrastructure, waste management, local people and tourism, and institutions, at a cost of nearly 40 million dollars, according to the Environment Ministry.
Germán Rodríguez, coordinator of the National Network of Environmental Training and Research (REDFIA), took the analysis to a deeper level and told IPS that one cannot talk about just one environmental crisis, or just one lake.
“It’s not just about an ecological crisis in terms of environmental loss and degradation, but about an economic, technological and cultural model that has plundered nature and that favours a mechanism of production and a lifestyle that are not sustainable,” he said.
In Rodríguez’s view, measures taken to save Lake Atitlán, as well as any other decision about the environment, will not be sufficient unless it is recognised that the current model of economic, technological and cultural development no longer makes sense.
The REDFIA expert said there is a need for a general law on water, as well as a law on land use that protects the environment, although hurdles like lack of awareness and favouritism towards vested interests have prevented their being enacted.
Meanwhile, pollution of this wonderful lake continues as it has for decades, in silence, only now giving a tangible reason for alarm.
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