Certain algal produces toxins that, in large amounts, can be harmful to marine life and potentially to humans. Algae forming these dense layers are described as harmful algal blooms (HABs). Monitoring of harmful algal blooms is important for freshwater ecosystems to prevent the contamination of local drinking water sources as well as in coastal regions to avoid shellfish poisoning, and economic losses through impacts on local fisheries and tourism. Fish kills can result from the associated toxins or from the immense depletion of oxygen caused by the increased algal activity. General conditions that favour algal blooms are rising seawater temperatures and high nutrient loading from fertilizers. However, there are many different types of phytoplankton which tend to form a bloom in different areas.
Continue reading at http://www.un-spider.org/links-and-resources/data-sources/daotm-HABs
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