[20200708]IF10690_淡水有害藻华：概述.pdf

https:/crsreports.congress.gov Updated July 8, 2020Freshwater Harmful Algal Blooms: An OverviewScientific research indicates that in recent years, the frequency and geographic distribution of harmful algal blooms (HABs) have been increasing nationally and globally. They have been recorded in all 50 states. HABs can be detrimental to human health, pets, livestock, aquatic ecosystems, and the economy. What Are Harmful Algal Blooms? Algal communities are naturally occurring components of healthy aquatic ecosystems, such as lakes, rivers, and estuaries. However, under certain environmental conditionssuch as increased temperatures and nutrient concentrations (e.g., nitrogen and phosphorus)colonies of algae can grow excessively (or “bloom”) and produce toxins. These HABs sometimes produce discolorations in the water that can appear as scums, paint-like slicks, clotted mats, or foam. Even when visible signs of a bloom are absent, however, algal toxins may still be harmful. While many types of algae can cause HABs in bodies of freshwater, cyanobacteria typically cause the most frequent and severe blooms. Some species of cyanobacteria produce toxins, called cyanotoxins, which can cause hep