Red tide is caused by
(a)Noctiluca
(b)Plasmodium
(c)Dinoflagellates
(d)All of the above

Hint: Discoloration of water bodies into a reddish-brown appearance is called red tide, which is caused due to microorganisms like Gonyaulax and Gymnodinium that grow in large amounts covering the water surface. They reproduce through binary and multiple fission.

Complete answer:
In Red tide estuarine, marine, or fresh water algae accumulate rapidly in the water resulting in red color. They are caused in water bodies due to the presence of dinoflagellates, Uncontrollable growth and population explosions of dinoflagellates make the water turn reddish-brown, leading to the phenomenon of red tides.

Additional Information: Dinoflagellates are unicellular protists and are motile when a dinoflagellates population increases in huge numbers the phenomena is called red tide or algal blooms, these blooms become very massive when carried by the wind, water current, or storms. They are mostly Marine and photosynthetic organisms, the release of neurotoxin kills marine animals like fishes present in that area, these are poisonous and destructive for the living organisms.
Red tide can kill large numbers of fish and other sea life including dolphins and other marine animals. It is considered harmful due to the toxins released by the algae.

So, the correct answer is, ‘Algal bloom.’

Note: Noctiluca causes green tide in the water bodies. It shows bioluminescent because of which the name ‘sea sparkle’ and ‘burning of the sea' is referred to The toxins released by the dinoflagellate is consumed by the filter feeders and leads to poisoning like in case of shellfish poisoning if consumed by humans leads to paralytic poisoning.