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Uganda: Algae Choking Lake Victoria
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New Vision (Kampala)
OPINION
28 April 2008
Posted to the web 29 April 2008
Jan Cordonnier
Kampala
The increase in the population of Kampala has led to the expansion of the residential and mushrooming of the slum areas. A number of suburbs have sprung up, yet the coverage of piped water from National Water and Sewerage Corporation is limited, let alone being erratic in supply. In the recent past, the onset of heavy rains in and around the city has contributed to big quantity of runoff, yet the drainage systems in many parts of Kampala are not functioning properly.
According to The New Vision of March 8, a thick carpet of algae covered Lake Victoria causing a sickening stench in Luzira, Ggaba and Munyonyo and making the fishing zone unusable. The algae mass, which looks like a green paint on the lake's surface, is a result of increased pollution from human disposal and industrial waste. The main reason for the presence of algae can be due to too much nutrients like phosphates and nitrogen.
Recently, Chemiphar laboratory sampled lake water at Ggaba, on Lake Victoria, to establish what type of algae was predominant in the green carpet. From the preliminary results, Cyanobacteria like f.e. Anabaena were found in the water samples. These Anabaena can be very toxic for plants and animals, including humans, because of the toxin microcystin. The toxins from Cyanobacteria can be as harmful as the poison of a cobra snake (10-15 ìg/kg body weight).
Microcystins are cyclic nonribosomal peptides produced by Cyanobacteria which, because of their hepatotoxicity, may damage the liver. They can accumulate in the fish tissues, liver, intestines and gallbladder, which means that secondary contamination by eating toxic fish from an infected pond or lake is possible.
A bloom is a rapid and massive increase in the number of algae on the surface of lakes and ponds. Although the occurrence of blooms is a natural phenomenon and is part of the annual cycle of the development of algae, some algae bloom can be harmful. More specifically, bloom of Cyanobacteria may lead to the development of a toxic green and frothy mass floating on the water's surface, of a few centimetres thickness.
Why do harmful algae blooming develop? Although the correct mechanisms responsible for the emergence of harmful blooms is not known, it is widely assumed that combinations of environmental factors play an important role. These environmental factors are driving a high Cyanobacteria nutrient content (Nitrates and Phosphates), a low acidity (low CO2), a relatively high temperature, strong light, a stable water, and a long residential time.
This algae blooming can cause several problems. In an aesthetic view, the presence of green badly smelling foam ensures that the aesthetic aspects and recreational use of surface water is unpleasant.
Ecologically, although the clarity of the water is affected, the oxygen content is reduced and the growth of other organisms is limited, it has a major impact on biodiversity in the water. On a health base, men, livestock, waterfowl, pets are sensitive to toxins released during Cyanobacteria bloom.
Based on their impact, cyanotoxins are divided into three groups. Hepatotoxins work on the liver and can cause a slow death, up to 36 hours or even longer after drinking contaminated water.
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Animals can get jaundice (yellow discolour of the mucous membranes of the whites of the eyes) and an increased sensitivity to light.
Neurotoxins work on the respiratory and nervous system. These types of toxins can cause vibration of the muscles, convulsions, dizziness, paralysis, respiratory problems and death after 30 minutes . The animals are dying as a result of this type of toxins, which are usually found near the lake or pond. Dermatotoxins can lead to irritation of the skin and eyes and cause, as well allergic as hay fever reactions. Relatively few acute poisonings have been reported in humans. It is, therefore, extraordinary that people would consume contaminated water given the bad smell and unpleasant colour of the water.
The writer works with Chemiphar (U) Ltd
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