Dinoflagellate toxins block the transmission of signals in the nervous system, causing DSP, NSP and PSP. Memory loss, vomiting, diarrhoea and paralysis appear within a few hours after the infected shellfish are consumed. When unsuspecting humans eat toxin-contaminated seafood, they ingest these powerful algal neurotoxins, resulting in four main kinds of shellfish poisoning: amnesic shellfish poisoning (ASP), diarrheal shellfish poisoning (DSP), neurotoxic shellfish poisoning (NSP) and paralytic shellfish poisoning (PSP), aptly named after the symptoms they produce. Like carefully concocted poisons, these toxins are tasteless, odorless, heat resistant and rapidly absorbed by the body. On par with chemical warfare agents like ricin, used in assassination attempts during the Cold War, a few milligrams of the most powerful dinoflagellate toxin, saxitoxin, can kill an adult human. Some algal toxins kill fish directly while others accumulate in shellfish. Algal blooms may be dominated by species which produce potent neurotoxins that are harmful to humans and animals. Some dinoflagellates and diatoms have an even more lethal mode of operation. Hans Eikaas, head of environmental technology and chemistry at DHI Water & Environment Pte Ltd, ammonia irritates fish gills and the algae clog the gills, suffocating fish in the process. The depletion of oxygen and build-up of ammonia from decomposing algae can result in the sudden large-scale death of fish and other aquatic creatures. When the algae die, they are broken down by bacteria and fungi, a process which consumes oxygen and produces ammonia. At high cell concentrations, phytoplankton block and prevent sunlight from reaching other aquatic life. An algal bloom can stretch for several kilometers and there can be as many as 500,000 cells in a single milliliter of water. Warm and calm waters, surface runoff into oceans, high sunlight intensities as well as low salt concentrations are also conducive for algal growth. When conditions are favorable, dinoflagellates and diatoms multiply rapidly to form harmful algal blooms (HABS) that color the oceans red, giving rise to the term ‘red tides’-a misnomer because these algae also come in hues of green, yellow and brown, depending on the color of the pigments in the cells.Īn increase in dissolved nitrogen and phosphorus-essential nutrients for algal growth-can encourage phytoplankton to grow out of control. However, a dark side lies beneath their beauty. Like their dinoflagellate cousins, diatoms are encased in geometrically-intricate silica cell walls, called frustules, captivating scientists and artists alike. Many dinoflagellates also produce light on their own and put on breathtaking bioluminescent light shows, bursting into flashes of neon blue light when disturbed by sudden movements in the water. They are important primary producers in coastal water ecosystems, synthesizing organic compounds from carbon dioxide using sunlight.ĭinoflagellate cells are enclosed in an intricate covering consisting of armor-like plates known as theca. The perpetrators at the center of the plot are tiny phytoplankton no bigger than a few micrometers in size, known as dinoflagellates and diatoms.ĭinoflagellates and diatoms are among the most common phytoplankton in the ocean. All have indulged in the fresh catches of the day-cockles and mussels.Ī microscope is required for the investigation into these bizarre events. Three have died and over forty are critically ill. Meanwhile, in Malaysia, several people afflicted with food poisoning symptoms have been admitted to hospital. In coastal fish farms across Asia, farmers encounter the macabre sight of tons of dead fish floating belly up in their pens. On a beach in Singapore, thousands of dead fish of all shapes and sizes are strewn along the shoreline, along with other exotic marine creatures like cuttlefish, and even a sea snake. Beachgoers in Hong Kong setting out to enjoy the sun, sand and surf are instead greeted by a sea which has turned a sinister shade of red. AsianScientist (July 14, 2017) – They are scenes of mystery, death and destruction.
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