Having just graduated from College, Sarah Jameson was working with Earthwatch In

Question

Having just graduated from College, Sarah Jameson was working with Earthwatch Institute to study the behavior and health status of the Tampa Bay/Sarasota Bay bottle nosed dolphin (Tursiops truncatus) population. She had done an internship with the group the prior summer, and was excited to go back. After arriving at the temporary housing in Sarasota and greeting all of her friends from last summer, she noticed that the mood was very grim. She was told that ZigZag had just washed up on the beach, dead. ZigZag was a loner male, freeze brand number 56, with a healed shark wound on the dorsal fin-ergo the nickname ZigZag. Last summer, he had been a healthy dolphin-was in top shape according to his physical exam-good weight, perfect blood counts, fecal showed no parasites. What happened?! The necropsy took place that very afternoon. After careful dissection of the already putrefying carcass, the blood work was normal. A little tricky to interpret given the partial decomposition, though. Body weight was very low. The blubber layer from the prior summer's data was 5.8 cm. The necropsy sample showed barely 2.1 cm of blubber. The lungs were filled with white frothy foam. Sputum cultures were sent out but the veterinarian had his diagnosis: pneumonia Sarah noticed that ZigZag wasn't the only dead animal washed ashore. Fish littered the beaches-their rotting carcasses giving a stinging scent to the otherwise refreshing ocean breeze. Dr. Wells, the lead PI in the study, grimly identified the causal agent: Red tide (a dinoflagellate algal bloom)

Explanation / Answer

Ans) Red tide dinoflagellates- Red tide is a name given to a phenomenon called harmful algae blooms (HABs ), which is caused by accumulation of fresh water algae or marine algae in the surface of water making the water to discolour, This basically happens in coastal areas. This Red tide is caused by accumulation of microscopic algae which mostly are Dinoflagellates.

Dinoflagellates are single celled microorganisms that are algae by nature. They have very attactive shapes which makes them different from other algae. They almost survive in oceans and coastal regions. Dino implies two flagellate implies flagella, hence dinoflagellates comprises of two flagella that helps it to move and to attach to water surface. Dinoflagellates feed on fishes and other protists. Some species of dinoflagellates are able to produce their own light by bioluminescence. During warm summer months in coastal regions ocean water, the marine dinoflagellates reproduce in a very great number causing water surface to appear as red or golden in colour, hence an algae bloom of red colour is then known as Red tide dinoflagellates. Amongst the very known species of dinoflagellates the red tide is caused by Karenia brevis.

Toxins released by dinoflagellates- During Red tide (harmful algae blooms ), the poisonous dinoflagellates produce neurotoxin that can cause severe illness and mortalities in fishes , shell fishes , sea birds and marine mammals. Humans in turn consuming fishes or shell fishes may also get susceptible to severe illness. There is diversity in toxins produced by dinoflagellates. The neurotoxins are named as brevetoxin , saxitoxin ( produced by Alexandrium species). Saxitoxin causes paralytic shellfish poisoning (PSP). Some dinoflagellates also produce reactive forms of oxygen as ( superoxide , hydrogen peroxide , hydroxyl radical), which are also responsible for toxic effects. Toxicity due to red tide dinoflagellates affects whole ecosystem as all organisms are dependent on each other.

Mechanism of action of toxins- The neurotoxins released by dinoflagellates are chemicals that affects nerve action by creating interference with movement of ions across cell membranes when taken in by fishes or other marine animals, therefore affecting muscle actions, Brevetoxin acts in a more different way , It gets AEROSOLIZED from the surface zone of water into the air, thereby causing respiratory irritation in humans.

Neurotoxins released by most dinoflagellates interacts with the receptor site of neurotransmitters or voltage sensitive ion channels. The voltage gated ion channels such as sodium , potassium , calcium in organisms including humans generates electrical signals which further controls muscle contraction , secretion of hormones , brain functioning. These neurotoxins targets the receptor sites and blocks it , therefore prevents ion conduction and flow and neural transmission resulting in varied health problems.

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