"It's Really Blooming"
(The Gulf of Mexico) Quinn Rallis and Noah Desrosiers
What causes an Harmful Algal Bloom (HAB) or Deadzone?
In August 1972, an investigation in the Gulf found severe oxygen depletion off southeastern Louisiana at depths of 10 to 20 meters. Since then many studies have found large areas in the northwestern part of the Gulf of Mexico where dissolved oxygen (DO) levels drop from normal values of about 7 parts per million (ppm) to 2 ppm or less. Because DO levels below 2 ppm can kill many fish species, this region has been named the “Gulf of Mexico Dead Zone (NOAA. - Deadzone).
Fertilizer and factory waste include nutrients, such as nitrogen and phosphorus. These are essential for the growth of algae normally found in marine and freshwater ecosystems. But an excess of these nutrients can cause too many algae to bloom. Excess algae can block sunlight from going to the other plants and lead to oxygen depletion by dieing and decomposing (NOAA - Red Tide).
Fig. 1. A diagram of eutrophication (Eutrophication of Lake Erie)
What type(s) of organisms are involved?
K. brevis (Karenia brevis) is the major algae affecting the Gulf of Mexico and the surrounding land. This type of algae is responsible for the red tides that occur (NOAA - Gulf Factsheet).
Karenia brevis is a dinoflagellate. Growth rate is affected by salinity, temperature and nutrient levels in the water. The number of K. Brevis in the water is 106 cells/liter. K Brevis is extremely toxic and produces compounds called brevetoxins. These kill many animals and cause human illness from poisoning the animals. They also cause irritation through the air (SMS at Fort Pierce).
What are the ecological impacts, what species are affected and how is the environment effected?
These algae blooms produce toxins that can kill fish, mammals, and birds, and may cause human illness or even death in extreme cases. These algae eat up all of the oxygen in the water as they decompose. The algae bloom clogs the gills of fish and other sea animals, or smother corals and submerged plants. Others discolor water or form huge and disgusting lumps of algae on beaches, or contaminate drinking water (NOAA - Hazards).
Figure 2. Fish affected by HABs
(Tom Archer, 2011)
(NOAA - HAB)
Figure 3. Red Tide
( Kai Schumann, California Department of Public Health volunteer)
(NOAA - Hazards)
Figure 4. Algal Bloom
(Tom Archer, 2011)
(Nature World News)
What are the economic impacts?
Fishermen cannot find fish in the dead zone since the water levels are hypoxic. They are required to travel a farther distance to find fish. It costs more money to buy more gas to travel that farther distance. There’s a lesser chance of finding the amount of food they could have years ago. That means the food they find will be much more expensive. Fishermen who don’t have as much money can’t find the fish and will lose their jobs (Dartmouth).
What geographic locations are affected by these?
The Gulf of Mexico covers a surface area of 579,153 sq. miles and is measured 994 miles west to east, and 559 miles north to south (World Atlas). Water from the Caribbean sea enters the gulf and the water circulates really quickly. 20 major rivers end at the gulf. It’s essentially a very deep pit and 62 percent of the gulf is deep water (Gulfbase).
How to reduce excess nutrients and solve this issue?
In order for this problem to be reduced, it has to be tackled at the top, which is the agriculture industry. There must be limits as to how much waste is discharged. Farms and industries aren’t doing a good job of managing that. The application of fertilizers should be used literally as efficiently as possible. Better timing could reduce the amount of fertilizer in the runoff water. Farmers should also attempt to divert the runoff into surrounding grasslands and not into rivers that eventually lead into the Gulf. Scientists are saying that the amount of nitrogen in the water needs to be reduced by 40 percent (Dartmouth).
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