**1. Introduction**

The enrichment of lakes and reservoirs with nutrients leads to an increase in the growth of algae, especially cyanobacteria, forming floating masses on the surface, causing a decrease in the concentration of dissolved oxygen and death in fish, and the death of livestock and other animals as a result of ingesting algae toxins. Filamentous cyanobacteria and green algae (Chlorophytes) cause clogging in filters of water treatment systems or problems in industrial systems when such water is used. The dinoflagellates are another group of phytoplankton that can secrete toxic substances. One of the by-products of algal blooms are high concentrations of organic carbon [1]. Increased phosphorous concentration and low P:N ratio are major factors for such a condition, and several studies indicate that toxins from cyanobacteria pose a health risk. According to the World Health Organization (WHO), the maximum acceptable concentration of the toxic substance (Microcystin-LR) in tank water that may be used for drinking is

(0.5–1.0 μg/cubic decimeter), as exposure to an increase of this substance causes liver cancer. Human exposure to this type of poison is possible because it is difficult to carry out a complete treatment of cyanobacterial toxins in drinking water plants. Cyanobacteria also cause the death of animals when they ingest these toxins and also lead to a lack of oxygen and the death of fish [2]. Algae are distributed worldwide in the sea, in freshwater and in wet situations on land. Most are microscopic algae, but some of them are so large, also some marine seaweeds that can exceed 50 m in length. The algae have chlorophyll and can make their own food through the steps of photosynthesis. Recently they are classified in the kingdom of protiste, which include a variety of unicellular and some basic multinuclear and multicellular eukaryotic organisms that have cells. Algal poisoning is an intense, often lethal condition caused by high concentrations of toxic blue-green algae (more commonly known as cyanobacteria—literally blue-green bacteria) in drinking water as well as in water used for recreation, agriculture and aquaculture. Severe illness of livestock and Fatalities, birds, pets, fish and wildlife from high growths of cyanobacteria water blooms occur almost in all of the countries in the world. Severe deadly poisonings have also been notarized in people. Poisoning usually comes during warm seasons when the water blossom are more acute and of longer duration. Almost poisonings come among animals drinking cyanobacteria infested freshwater, but aquatic animals, mostly mariculture fish and prawn, are also affected. The toxins of cyanobacteria comprise six special chemical classes collectively called cyanotoxins [3]. Toxic algae, micro-algal blooms, phytoplankton blooms, red tides, or harmful algae, are all terms for normally occurring phenomena. Around 300 species of micro algae are notify at times to form mass appearance, so called blooms. About one fourth of these species are recognized to produce toxins. The scientific society points out to these events with a generic term, 'Harmful Algal Bloom' (HAB), understanding that, because a wide range of organisms are implicated and some species have toxic impacts at low cell intensity, not all HABs are 'algal' and not all occur as 'blooms' [4]. Many of the organisms in charge for red tides are closely distributed and, in recent years, the organisms appear to be markedly spreading. Natural events such as hurricanes can spread over organisms, and it is doubtful that some organisms may be moved long distances in ship ballast waters. Another factor that may motivate algal proliferation in both freshwater and marine systems is augmentation nutrient loading. Certain algae occur more usually in some areas than others and it is useful to know which ones are problems in particular locations. Good sources of information about algal blooms are the State public health department or the State division of marine resources or marine fisheries [5].
