Poisonous Plants, Fungi, and Algae Algal Toxins

Algal Blooms and Harmful Algal Blooms

Kingdom Monera Cyanobacteria - blue green algae Used as a food source: Nostoc, Spirulina (since ancient times - today protein additive) Toxins produced by several species can cause problems during blooms

Kingdom Protista Six divisions of algae: Division Pyrrophyta - dinoflagellates Division Chrysophyta - diatoms Division Euglenophyta - euglenoids Division Chlorophyta - green algae Division Rhodophyta - red algae Division Phaeophyta - brown algae

Toxic Cyanobacteria Normally algal cells only release the toxins when the cells die or when they age and become leaky Poisoning typically occurs when animals ingest whole cells If water is treated to break up a bloom, it is possible for fatal levels of the toxin to be released 12 genera of cyanobacteria known to be toxin-producers. Two of the most toxic - Anabaena and Microcystis.

Types of toxins Two groups of deadly toxins in the cyanobacteria Neurotoxins - alkaloids - nervous systems Anatoxins - Very Fast Death Factor – 4 min – bind to acetylchone receptors and cause respiratory paralysis Saxitoxins – neurological dysfunction and paralysis – block sodium channels on neurons – (also in some dinoflagellates) Hepatotoxins - cyclopeptides - target the liver Microcystins – disrupt cytoskeleton in liver cause liver cells to collapse – blood pools in liver causing fatalities – may also be carcinogenic Other less deadly toxins – swimmers itch

Anabaena Anabaena - a genus of filamentous N2-fixing cyanobacteria Known for producing a suite of cyanotoxins which range from the neurotoxic anatoxins and saxitoxins to the hepatotoxic microcystins. Genus can be found throughout the world

Anabaena

Microcystis Microcystis spp. are single-celled, colonial, freshwater cyanobacteria World-wide distribution Microcystins (hepatotoxins) are main toxin type M. aeruginosa and M. viridis appear to be the most common microcystin-prodcuing species.

Microcystis

Dinoflagellates Unicellular algae covered with cellulose plates giving an armored appearance Important to the food chain in marine and fresh water Some marine species cause Red Tides Bloom conditions Color the water “red” Produce powerful toxins Pfiesteria newly recognized problem

Dinoflagellates

Dinoflagellates and Red Tides Several species of dinoflagellates, especially Gymnodinium breve, Alexandrium spp, produce powerful toxins that can cause massive fish kills As schools of fish swim through a bloom, the dinoflagellates may be disrupted or killed, releasing neurotoxins into the water The toxins damage the gills or suppress heart rate and result in asphyxiation - hundred or thousands of dead fish wash up on beaches

Other Problems In other instances, the toxins accumulate in various filter feeding shellfish When the shellfish are eaten the toxins can affect humans Cause various syndromes depending on the dinoflagellate and type of toxin

Dinoflagellate Poisonings Paralytic Shellfish Poisoning (PSP) – saxitoxin Diarrhetic Shellfish Poisoning (DSP) Neurotoxic Shellfish Poisoning (NSP) – usually only fish kills Ciguatera Fish Poisoning (CFP) – GI, neurological, and cardiovascular symptoms from eating contaminated fish (fish not affected) Pfiesteria piscicida – recently identified problem

Pfiesteria piscicida Pfiesteria piscicida implicated as the organism responsible for recent fish kills and fish disease Since the early 1990s toxins produced by Pfiesteria may have killed over one billion fish in North Carolina alone with other outbreaks along east coast Toxins not identified yet People exposed to toxins have developed skin and neurological problems

Pfiesteria Complex life cycle Appears to be around 24 different stages in the life cycle – with flagellated, amoeboid, and encysted stages Only 3 stages appear to form toxins