Harmful Algal Blooms in the Mediterranean Sea: Effects on Human Health

Abstract

Introduction Algae are unicellular microscopic plants that can be considered the foundation of life. An algal bloom develops in the marine or freshwater environment when excessive growth of these organisms takes place because of changes in that environment. A harmful algal bloom (HAB) is defined as a bloom that has deleterious effects on plants, animals or humans [1, 2]. Phytoplankton blooms, micro-algal blooms, toxic algae, red tides or harmful algae are all terms for these naturally occurring phenomena [3]. HABs can deplete the oxygen and block the sunlight that other organisms need to live, and some HABs release toxins that are dangerous to animals and humans. Marine algal toxins are responsible for an array of human illnesses associated with the consumption of contaminated seafood and exposure to aerosolized toxins. On a worldwide basis, marine algal toxins are responsible for more than 60,000 intoxication incidents per year, with an overall mortality rate of 1.5%. In addition to their effects on human health, algal toxins are responsible for extensive die-offs of fish and shellfish, and have been implicated in episodic mortalities of marine mammals, birds and other animals dependent on the marine food web. The impacts of algal toxins are generally observed as acute intoxications, whereas the health effects of chronic exposure to low levels of algal toxins are only poorly documented and an emerging issue [4, 5]. Algal toxins produced bydinoflagellates and diatoms also have an impact on humans. Filter-feeding shellfish, zooplankton and herbivorous fish ingest these algae and act as vectors to humans either directly (e.g. shellfish) or through further food web transfer of sequestered toxin to higher trophic levels. Consumption of seafood contaminated with algal toxins results in five seafood poisoning syndromes: paralytic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning, diarrhetic shellfish poisonReview