Toxic algal blooms in our waterbodies which causes, Slides of Marine Science and Biology

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Effects of Toxic Algal

Blooms

Presentation taken by

1. Muzammil Siddiqui – BFS-2020-01-

Introduction

• (^) An algal blooms is the rapid increase in the population of algae in various aquatic ecosystems. Blooms which produce toxins are called ‘Toxic Algal Blooms’. There are many species which are capable of producing biologically active secondary metabolites, which are highly harmful.
• (^) They are recognised by the discoloration in water due to the algae’s pigments. Blooms can last from a few days to a month.
• (^) Natural causes, such as river flood or upwelling in the seas, are responsible. But man-made activities are also causing it due to terrestrial run-off, eutrophication, sewage wastes, etc.
• (^) The toxins belong to various chemical classes; cyclic peptides, alkaloides, lipopolysaccharides, among others.
• (^) Various genera of dinoflagellates, cyanobacteria and diatoms form such blooms.

Toxins classes and their effects

1. Neurotoxins

• (^) They have been responsible for major poisoning. They cause acute effects in vertebrates.
• (^) They affect the nervous system of animals by impairing the CNS and/or PNS by loss of neuron, axon, glial cells.
• (^) Rapid paralysis of respiratory and peripheral skeletal system takes place consequently, which leads to death.
• (^) Anatoxin-a inhibits causes changes in post-synaptic receptor-ion channel complex, because of mimicing the neurotransmitter, Acetylcholine. It binds to its receptors, causing imbalance. Thus, it is a potent acetylcholine inhibitor.

2. Hepatotoxin

• (^) Nodularin and microcystin are common hepatotoxins from algae.
• (^) They damage hepatic cells. They injure key subcellular structures, such as mitochondria and plasma membrane.
• (^) Together with ROS, they act as oxidising species within hepatocyte to cause oxidative stress by creating imbalance between pro oxidants and anti oxidants.
• (^) They are taken up to the liver cells through active transport via bile acids by the multi-specific anion transporters. Thus, it causes bloodpools in liver and causes 100% weight gain for liver and causes massive liver haemorrhage.
• (^) They also bind irreversibly to macromolecules such as lipids and proteins. Thus they inactivate key enzymes.

4. Saxitoxins

• Saxitoxins are heterocyclic guanidine neurotoxins. Shellfish poisoning is due to them mainly.
• (^) Blooms releasing them have often resulted in mass deaths of fish and livestock, and has polluted water resources.
• (^) It blocks the passage of nerve impulse by blocking sodium ion entry into nerves.
• (^) The Paralytic Shellfish Poisoning(PSP) symptoms begin within 30 min of ingestion with tingling sensation of lips, tongue and throat which becomes total numbness soon. Vomiting and diarrhoea occurs.
• (^) In case of acute poisoning, numbness spreads to neck and extremities. So, muscular weakness and loss of motor coordination happens.

5. Cylindrospermopsins

• (^) They are cyanotoxins. They are polycyclic uracil derivatives having sulphate and guanidine groups. It is zwitter-ionic, thus it is water soluble.
• (^) It blocks glutathione, protein synthesis and cytochrome p450.
• (^) Glutathione is needed for immunity as it repairs tissue, protects from damage from free radicals. Cytochrome p450 is the enzyme for clearance of various compounds.
• (^) Thus, it is a potent protein synthesis inhibitor and causes oxidative stress due to cytochrome p450 reduction.
• (^) Cylindrospermopsis raciborskii presents a major problem for management globally.

7. Anatoxins

• Anatoxins are neurotoxic alkaloids made exclusively made by Anabena, Aphanizomenon and Planktothrix.
• (^) It is bi-cyclic secondary amine which mimics acetylcholine and binds to acetylcholine receptor at the axon terminal. Its binding is irreversible, so the sodium channel is locked open. It becomes over-stimulate, fatigued and eventually paralysed.
• (^) It results in lack of oxygen to the brain, subsequent convulsions and thereafter, death.
• (^) It also is cholinestrase inhibitor. Cholinestrase degrades acetylcholine so that overstimulation is prevented, but anatoxin presence facilitates overstimulation.

8. Contactdermatitins

• In some cases, a skin reaction may develop by touching fish or fish residue. Allergic reactions of varying severity have been reported from number of cases.
• (^) Cyanobacterial pigment, cyanophycin has been found responsible.
• (^) Skin irritation were frequent. Ocular and nasal irritation happened to swimmers exposed to Oscollatoriaceae.
• (^) Sensitive individuals may react severely. Tongue swelling, rapid heart rate can also happen.