| Algal Blooms |
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Information AboutAlgal Blooms |
| CATEGORIES ABOUT ALGAL BLOOM | |
| algae | |
| biological oceanography | |
| aquatic ecology | |
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The excessive growth of algae may disrupt higher links of the local Food Web . Algae that die and sink to the bottom stimulate growth of decomposers, especially Bacteria . Decomposition can result in the depletion of Oxygen in the deeper water layers, and these conditions may result in fish kills or replacement with less valuable species more tolerant of higher phosphorus and lower oxygen levels. Deoxygenation also may cause chemical changes in the mud on the bottom, lowering the Redox value of the sediment, releasing chemicals and toxic gases. All these changes further accelerate the Eutrophication of the Aquatic Ecosystem . Algal blooms may also be of concern as some species of algae produce Neurotoxin s. At the high concentrations reached during blooms, these may cause death if affected water is ingested. Algal blooms are monitored using biomass measurements coupled with the examination of species present. A widely-used measure of algal and cyanobacterial biomass is the Chlorophyll concentration. Peak values of chlorophyll ''a'' for an Oligotrophic lake are about 1-10 µg/l, while in a Eutrophic lake they can reach 300 µg/l. In cases of hypereutrophy, such as Hartbeespoort Dam in South Africa , maxima of chlorophyll a can be as high as 3,000 µg/l (Zohary and Roberts, 1990; Bartram et al., 1999). RED TIDE See Also: Red tide The so-called red tide is an example of a naturally occurring estuarine or marine ''algal bloom''. Red tide is caused by species of Dinoflagellate s, often present in sufficient numbers (thousands or millions of cells per milliliter) to turn the water red or brown. BLACK WATER So-called black water is a dark discoloration of sea water, first described in the s. It dissipated within a few months by transport through the Florida Keys into the Florida Straits and by disruption by winds and wave action. WATER TREATMENT Algal blooms sometimes occur in drinking water supplies. In such cases, toxins from the bloom can survive standard water purifying treatments. Researchers at Florida International University in Miami are experimenting with using 640-kilohertz Ultrasound waves that create micropressure zones as hot as 3,700° C. This breaks some water molecules into reactive fragments that can kill algae (Song et al., 2005). SEE ALSO REFERENCES
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