Without sunlight, photosynthesis stops, which means no oxygen is released into the water. This lack of oxygen can lead to a “dead zone,” or an area where aquatic plants and animals cannot survive. It creates dead zones: As algae blooms, it can deplete the water of its natural oxygen. A bloom does not have to produce toxins in order to be harmful to the environment. These so-called algal blooms can lead to a depletion of oxygen in the water, release of toxins and taste and odor problems. Blooms of cyanobacteria can become so thick that they block sunlight at the surface of the lake. You might also see a layer of algae in the form of a mat or foam floating on the surface. Algal blooms and oxygen depletion. In eutrophic lakes, algae are starved for light. PH Effects at Night. Blooms can block light to organisms lower in the water column, or even clog or harm fish gills. Therefore, it is important to control algae growth for a healthy ecosystem. As algae begins to form, it blocks sunlight from entering the bottom of ponds, lakes and rivers. When algae don’t have enough light they stop producing oxygen and in turn begin consuming oxygen. Since most fish, crabs, mollusks, and other aquatic animals depend on oxygen as much as land-based animals, the end result of eutrophication and algal blooms is the creation of an area where … Dead bacteria sinks and decays, using up more oxygen in the process. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic, multicellular organisms like seaweed and microscopic, unicellular organisms like … Outbreaks of algae have killed up to a million fish in the Murray Darling Basin over the last two weeks. Why algae are important Harmful algal blooms often make the water look like pea soup, or green or blue paint. The phenomena of "algae blooms", when the population of algae … But, when blue-green algae die, they decompose by a process that uses cellular respiration, which uses up oxygen. First, to clarify, blue-green algae are actually a type of bacteria, they are classed in the phylum “Cyanobacteria.” Cyanobacteria (that is, blue-green algae) obtain their energy from photosynthesis, which does create oxygen. When algae receive enough sunlight, they produce oxygen through photosynthesis and release it in the water. As more nutrients drain into the water, eutrophication repeats in a vicious algal bloom cycle and releases more nutrients in the water.. Without treatment, the algae will grow more every year, resulting in an unbalanced ecosystem. If advisory signs are not posted, and you see what looks like a HAB, please avoid contact with the water and report it to the Report-a-Bloom hotline at 801-536-4123 . At night, no photosynthesis takes place, so algae stops taking in carbon dioxide from water and goes into a respiratory stage 1.During this respiratory stage, algae consume oxygen that was produced during photosynthesis and release carbon dioxide into the water 1.This increased production of carbon dioxide decreases the pH levels in the water at night. 2. Oxygen depletion has two algal-bloom-related causes: respiration and decomposition. Moreover, when the large blooms of algae begin to die, bacterial decomposers further deplete the levels of oxygen. Not all algal blooms are harmful, some can actually be beneficial. If there is a bloom, the phytoplankton and other aquatic organisms (like fish) can consume more oxygen than is produced. It can also be harmful by causing anoxic conditions where oxygen is depleted from the water. It is not safe to drink: Some lakes supply drinking water for millions of people. Severe blooms can completely deplete oxygen and cause dramatic fish kills. 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