NEWS

Greek lakes filling up with dangerous toxins

High concentrations of toxins hazardous to humans and animals have been found in Greek lakes, due to the presence of toxic blue-green algae (commonly known as pond scum) or cyanobacteria, and scientists are demanding the adoption of safety levels and systematic laboratory monitoring of aquatic ecosystems which are sources of drinking water. A team of biologists from the Aristotle University of Thessaloniki carried out research on 32 aquatic ecosystems (31 lakes and one river) during 1999-2000. In nine lakes, they found toxins above the limits set by the World Health Organization (WHO). The findings of the survey were presented for the first time at the seventh World Algology Conference in Thessaloniki in 2001. The scientific team studied the growth of blue-green algae, or cyanobacteria (plankton-like organisms), which results in the phenomenon of green, scummy water that may contain toxins. As Doctor of Biology Elisavet Vardaka notes in her doctoral thesis, exposure of mammals, fish and birds to these toxins has been linked to incidents of poisoning and deaths, while plants have also been affected. International studies make references to people being poisoned by cyanobacterial toxins in drinking water,. .. while recently there were fatalities in Brazil from the use of water containing cyanobacterial toxins. In addition, some cyanobacterial toxins are considered as carcinogenic, and data also exists on their accumulating in mussels, oysters and fish, which indicates that the toxins travel through the food chain. The presence of toxins in aquatic ecosystems used for drinking water and recreational sports is the subject of serious international study and is an area of concern for WHO, which has set maximum acceptable levels for concentrations in water. The competent authorities in Greece are not ignorant of the problem (a state-funded study has been carried out in the past) but the European Union has not adopted maximum levels nor set up a framework for dealing with the problem, so that it has not received full recognition despite its gravity. Assistant Professor of Biology at the University of Thessaloniki, Thomas Lanaras, told Kathimerini that there was no relevant legislation in Greece. In Europe, some countries have adopted regulations in accordance with the recommendations of WHO, others have not. The size of the problem is relative to the uses the water of a lake is put, thus lakes used for irrigation or those next to cities used for recreational purposes form the main focus of scientific surveys. In 1984, the EU conducted a survey to assess the extent and gravity of the problems caused by the presence of toxic cyanobacteria and their toxin emissions in aquatic ecosystems. The Greek authorities, however, have stated that Greece has not noted the presence of toxins, nor poisoning incidents. Scientists argue that this could be due either to a lack of data or to the absence of very serious cases (of poisoning or death) in animals and humans from cyanobacterial toxins. According to the Greek scientific team, cyanobacterial toxins were first observed in 1987 in the lakes of Vegoritida, Koroneia, Volvi and Kastoria. However, in Greece to date there have been no reports linking cyanobacterial toxins to poisoning or the deaths of animals or plants. The lack of data on or research into cyanobacteria in Greek aquatic ecosystems, coupled with the size of the problem in other European and non-European countries with similar environmental conditions to those of Greece, made the recent study by Thessaloniki University biologists absolutely necessary. The biological team found serious problems in lakes close to cities, such as Kastoria and Ioannina. Lakes in which high concentrations of toxins were found include Volvi, Doirani, Little Prespa, Vistonida, Amvrakia, Zazari and Koroneia. In the absence of constant laboratory monitoring and surveys, the extent of the problem in Greece cannot be precisely estimated – the possible effects on the food chain are still a matter for research all over the world. Thomas Lanaras said that our findings from our measurements is the first stage in our research, and in the second stage we would like to study the possible effects of these concentrations. Lake Kastoria A large part of the survey focused on Lake Kastoria, which had concentrations 3,000 times above the levels ordained by WHO for drinking water. The deputy mayor of Kastoria, Christos Toskos, said the findings of the study on blue-green algae in the lake have already been brought to the attention of the competent ministries of the environment, planning and public works and of agriculture. The municipality, as part of the lake’s clean-up, had already included the question of setting up a laboratory in connection to the third Community Support Framework, but Toskos added that the phenomenon of scummy water did not seem quite so widespread this year. Pond scum grows particularly fast in summer. Fluctuations in algae concentrations can occur on their own, said Assistant Professor Maria Moustaka-Gouni, but scientifically speaking, when an aquatic ecosystem has toxic cyanobacteria, it will increase if nothing is done to lower it. Cyanobacteria exist in all the world’s lakes. The problem arises when they increase in volume. The accumulation of nutrients (eg waste or fertilizers) in water (known as eutrophism), whether organic or inorganic, leads to rapid plant growth and an increase in plankton. Over the last 50 years, human activities (anthropogenic eutrophism) have resulted in the increase in nutrients in water. It is internationally recognized that when we have concentrations of blue-green algae of over 75 percent, they are toxic, said Moustaka-Gouni. The team’s scientists have not observed concentrations of cyanobacteria in lakes which supply urban areas with drinking water. But species of blue-green algae have been found in some, which require systematic monitoring, and measures will have to be taken if they increase above acceptable levels. Hydrological surveys have concluded that the ratio of surface to ground water use will change in the future due to the decrease in ground water reserves. This will entail systematic monitoring of water destined for consumption. Today, 90-94 percent of water for use is ground water and 6-10 percent is surface water from rivers, dams and lakes. Dealing with algae Israel is one of the countries which systematically monitors the phenomenon. In the last five years, based on the data of previous years and the cause of the problem, it has applied methods to deal with the algae in the lake of Nazareth, for example. Other countries have managed to restore aquatic ecosystems, first dealing with the sewage from urban centers through special treatment programs. But biologists note that the methods implemented in Scandinavian countries, say, would not necessarily be equally effective in Greek lakes. What are cyanobacteria? Cyanobacteria form in shallow, warm, slow-moving or still water. They are made up of cells. A mass of such cells together is called a bloom. Needing light, water and phosphorus in order to survive, the presence of phosphates in detergents and fertilizers nowadays is a huge boost to their development. The toxic effects of cyanobacteria have been known for over 100 years. Certain species of cyanobacteria naturally produce toxins (30 to 50 percent are harmless), very few of which have actually been isolated and categorized to date. Some of these toxins attack the liver (hepatotoxins), others (less common) attack the nervous system (neurotoxins), others are skin irritants. Even one species of toxic cyanobacteria in a bloom can pose dangers – and toxic algae may be hard to distinguish. Only laboratory analysis can tell if a body of water containing scum is safe or not. While many people have taken ill, there have been relatively few fatalities. Symptoms of cyanobacterial poisoning may include headaches, fever, diarrhea, abdominal pain, nausea and vomiting, as well as irritated eyes and skin. Animals, not as fussy as humans about the taste and smell of water, may be more likely to die from drinking contaminated water. Modern water-treatment methods are effective in combating the algae. But contaminated water cannot be used for washing, bathing, or cooking (boiling does not remove the toxins). And the best way of avoiding the problems associated with cyanobacteria is to prevent their formation through reducing the input of nutrients, such as phosphates, into the water supply.