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Fishes in the Deep Ocean & the Effects of Dangerous Algae

A harmful algae bloom is a phenomenon that occurs mostly in coastal waters but sometimes occurs in the deep ocean. When this happens, colonies of algae produce harmful, even toxic effects that can kill fish and other marine wildlife. These blooms occur when an algae colony grows out of control and though it's rare for algae to cause harm to the environment, algae blooms can kill fish by either damaging or clogging their gills or by dissolving the oxygen in water.

  1. Background

    • There are two types of harmful algal species, according to the Center for Sponsored Coastal Ocean Research; Microalgae, which are microscopic, single-celled organisms, and macroalgae, which are seaweeds. Some harmful algae can produce toxins that are deadly to humans and many marine organisms, including fish, birds, manatees, sea lions, turtles and dolphins. Some algae do not harm humans, but can still cause illness or death in fish.

    Coastal Areas

    • According to the National Oceanic and Atmospheric Administration, harmful algae blooms, which are also known as a "red tide" because they cause the water surface to turn a reddish color, occur on the coast of nearly every U.S. state. Every summer, the Gulf Coast of Florida is home to a harmful algae bloom. Some of these blooms are not harmful. They can, in fact, be beneficial to the environment because the microscopic plants provide food for marine wildlife.

    Deep Ocean

    • Scientists discovered harmful algal blooms in the deep ocean waters of the Pacific Ocean for the first time in 2010. Louisiana State University Professor Sibel Bargu discovered that the algae Pseudo-nitzschia, which produces a neurotoxin called domoic acid, was found in the open ocean of the Pacific. In separate research, University of Hawaii microbial oceanographer Dave Karl, who has studied algae blooms in Hawaiian waters, told the Honolulu Star Advertiser that the presence of the microscopic algae in the deep ocean was a mystery because, unlike in coastal waters, there are few nutrients for the algae to utilize to grow and reproduce.

    Causes

    • Scientists as of 2011 have not yet verified the precise cause of harmful algae blooms, according to an issue brief by SeaWeb, a nonprofit organization which advocates for a healthy ocean. However, some scientists suspect that humans, through nutrient pollution, might be contributing to the growth of harmful algae blooms. Human-produced agriculture, sewage outfalls and mining create a "nutrient-rich environment" that allows certain species of phytoplankton to grow, according to SeaWeb. In addition, SeaWeb reports that some species of phytoplankton can be transported in ships' ballast water to parts of the world they did not inhabit before.

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