What is a “Dead zone” in the Ocean?
Well, it is exactly that. Technically, this condition is known as “hypoxia.” Remember that the prefix hypo- means low, so it means low oxygen (FYI: You can also suffer hypoxia in your blood). Dead zones are popping up all over the world, so this is a timely opportunity to find out what creates these dead zones.
Science is publishing a new report that the number and size of these oceanic dead zones are increasing. This may be because of more extensive surveying, but many of these dead zones are being attributed to agriculture and the use of fertilizers.
So, how do fertilizers kill organisms living in the ocean? Aren’t fertilizers used on land and not the sea? Also, how do fertilizers make our crops grow, but kill fish? What gives?
The red areas signify extremely low levels of dissolved oxygen in the water.
A notable dead zone of late is the Gulf of Mexico. I actually wrote something about it for Environmental Graffiti some time last year. The problem in the Gulf is that fertilizers being used in the Midwestern states like Iowa and Illinois are leaching into water sources or just running off the acres the nitrogen-rich fertilizers are originally applied and entering the Mississippi River system. Any little creek running by a corn farm in Iowa picks up the fertilizer run-off and then that creek meets up and joins a bigger creek, and then a small river, and so on until that fertilizer enters the Mississippi River. Then that nitrogen is headed for the Gulf of Mexico.
The nitrogen does not kill plants or animals in the Gulf. In fact, quite the opposite. The nitrogen and other nutrients involved in agricultural fertilizers cause what are known as “blooms.” Algae and other microscopic organisms thrive in this newly fertilized environment. They thrive and thrive so much that it is like a bloom, when everything comes into maturity at the same time. However, the downside of that is most organisms have an expiration date, if you will, and when a enormous number of anything dies at the same time, it means that an enormous number of things are going to decompose at the same time.
Guess what diatomic element is need for decomposition? Yep, O2. Good ol’ Oxygen.
The primary agents involved in decomposition are bacteria, and bacteria require oxygen. Thuse bacterial decomposition requires oxygen, and the problem is that when all that algae dies, their little corpses require a LOT of bacteria and that bacteria requires a LOT of oxygen. So much so that the too much oxygen is being depleted from the water at too fast a rate to balance the system. And voila, no oxygen, no life.
There are other dead zones that are not being attributed to fertilizers, but instead on perhaps natural fluctuations in ocean currents. The increase in hypoxia in the world’s waters may mean that ocean currents are becoming a little whacked out. Some scientists point to global warming as a cause for this disruption in normal ocean currents.
These dead zones are popping in some of the richest fishing waters around the globe, so obviously, this is a dangerous situation. The boom in ethanol and other bio-fuels is further heightening fears about the affects of fertilizers in our oceans.
And geez, it’s not like our fishing industries aren’t hurting enough…
dead zones, hypoxia, oceans, fertilizers, global warming, Science magazine, science, marine science, Gulf of Mexico, oxygen, nitrogen, bacteria, algae, blooms, ethanol, bio-fuels, fishing
