The Negative Effects of Eutrophication
By Abbie Estabrook and Dayton Hamele
Explanation of what causes an HAB or a Dead Zone
Red tides are caused by an extensive growth of algae in a body of water. This happens when cold water containing rich nutrients mixes with surface water. Red tides can be very dangerous if the toxins that the algae produce becomes concentrated in the bodies of organisms that eat the algae. When shellfish and other fish feed on the algae they store toxins in their cells. Freshwater eutrophication can also occur, this is when nutrients build up in a lake or pond and causes a massive growth of algae. Human activities such as farm and sewage runoff can cause this process to increase. When the algae forms at the top of the surface it prevents sunlight from getting to the plants and algae beneath the surface and they die. When bacteria tries to break down the decaying matter they use up all the oxygen. Fish begin to die from this also because of the lack of oxygen (NOAA).
What types of organisms are involved?
Harmful Algae blooms occur when colonies of Algae and plants living in the sea who grow too fast out of proportion and produce harsh toxins. The phytoplankton overproduce and grow rapidly due to increase of nutrients in the water because of farm run off. There are a wide variety of different species that are greatly affected by red tides. Fish are the most common because of how fast the deadly toxins can reach them. There gills stop functioning and violent twisting motions occur as a result. Large scale die offs have been observed with red tides since as earlier as 1844, according to Florida Fish and Wildlife Conservation and Commission, and have been an ongoing problem. Invertebrates such as shrimp, sponges, sea urchins, crabs, and shellfish have been exposed to toxins and low oxygen conditions from the blooms and have died. ( Florida Wildlife Conservation)
What are the ecological impacts, which species are affected and how is the environment affected?
Marine animals such as sea turtles, manatees, dolphins, and others have consumed or inhaled deadly toxins. Some examples of the results these toxins have on these organisms are swimming in circles, lack of coordination, and extensive muscle twitching. They consume contaminated prey like fish and crustaceans. " The largest dolphin die-off caused by a red tide resulted in more than 740 bottlenose dolphin strandings ( Florida Wildlife Conservation). " Birds are another common victim of red tides, they have trouble standing, weakness, difficulty flying, and seizures as a result. Manatees are endangered species whom consume breve toxins, created by red tides. Manatees diet that consists of seagrass blades contain these toxins. " More than 50% of the unusual marine mortality events are now associated with HAB's ( Harmful Algae)." Some harmful Algae toxins are released into the air, causing respiratory problems, for humans, pets, and livestock. It causes an unsafe environment and the red tides restrict humans and other organisms from retrieving safe seafood, and places to swim.
Geographic Locations Affected by Red Tides
For a population to expand quickly and sustain itself over time it requires the presence of algae in the water column as a major nutrient source, and wind or water current movement that condenses the algae population into an increasingly denser cluster. The dinoflagellate is a predominant red tide organism in The Gulf of Mexico, also occurring on the Atlantic side of the Florida coast. Blooms appear to originate 10 to 50 miles offshore along the continental shelf called “initiation zones.” From these primary locations, red tide is transported into nutrient-rich shallow waters where it continues to multiply to harmful levels. Although red tide events occur predominantly in these locations, red tide is a global phenomenon. Through the years, red tide events have become more frequent and widespread. They occur in several countries including Russia, Spain, Australia, Chile, Japan, and Brazil.
Seasonal Effects on red Tides
Dr. Richard Stumpf as well as many other scientists suggest that NOAA research models recorded a summertime wind shift in The Gulf of Mexico. This specific wind shift changes the direction of the Mississippi River plume from the Western Gulf of Mexico to the eastern Gulf heading toward the West coast of Florida. One of the best known harmful algal bloom occurs occurs nearly every summer along Florida’s Gulf coast. Both natural and man-made nutrients travel downstream in the Mississippi River plume stimulating a red tide bloom.
Economic Impacts of Red Tides
Fish Deaths Caused by Red Tide
(Scuba Diver Life)
Illness Caused by Red Tide
(Centers for Disease Control and Prevention)
Red Tides effects on the Coast
(World Resources Institute)
Reducing Excess Nutrients to Solve the Issue of Red Tides
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