Hint: An algal bloom also known as marine bloom or water bloom is a rapid increase within the population of algae in an aquatic system. Algal blooms generally occur in freshwater and sometimes in marine environments. Causative organisms of red tides are red dinoflagellates (Gonyaulax) that multiply rapidly. Due to their large numbers, the ocean appears red.
Complete Explanation: Algal bloom refers to rapid growth of microscopic unicellular algae. Algal blooms are the result of a nutrient, like nitrogen or phosphorus from fertilizer runoff, entering the aquatic system and causing excessive growth of algae. An algal bloom affects the entire ecosystem. Consequences range from the benign feeding of upper trophic levels, to more harmful effects like blocking sunlight from reaching other organisms, causing a depletion of oxygen levels within the water. Red tides are caused by red dinoflagellates (Gonyaulax). These organisms are single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are mostly marine, but they are also common in freshwater bodies. As they multiply rapidly, due to their large numbers, the ocean appears red in color. They both lead to water pollution.
Additional information: Red tide algae make potent natural toxins. It's unknown why these toxins are created, but some are often hazardous to larger organisms through the processes of biomagnification and bioaccumulation. Grazers like fish and krill are unaffected by the toxins, so as they eat the algae the toxins are concentrated and accumulate to a level that's poisonous to organisms that prey on them. Large fish kills and a number of other mammalian diseases and deaths are attributed to consumption of shellfish during seawater algal blooms.
Note: As more algae and plants grow, other organisms die. This dead organic matter becomes food for bacteria that decomposes it. With more food available, the bacteria increase in number and spend the dissolved oxygen within the water. When the dissolved oxygen decreases, many fish and aquatic insects die. This leads to a dead area. Algal blooms concern us, as some species of algae produce neurotoxins. At high concentrations, these toxins may have severe biological impacts on wildlife. Algal blooms composed of phytoplanktons known to naturally produce biotoxins are often called Harmful Algal Blooms, or HABs.
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BIOLOGY Class 11 NCERT EXERCISE 2.4 | Biological Classification | Class 11 Chapter 1 | Kanika Sharma