This article discussed the rising number of ‘dead zones.’ Dead zones are marine areas with so little oxygen that they barely support life, due to large amounts of bacteria. These zones have increased worldwide by a third since 1995, with now over 400 of the oxygen starved regions worldwide. These areas seriously stress marine ecosystems and deplete stocks of edibles such as fish and clams. It was reported that warming coastal waters and greater demand for corn will intensify the problem. Restricting the flow of nutrients into waterways is the first step in beginning to save these zones, but recovery may take years.
Dead zones begin when nutrients from fertilizer runoff, sewage discharge or natural upwellings in the water column feed the growth of phytoplankton, tiny free-floating organisms such as some algae. With these added nutrients in the water, the water becomes greener, as it would on land. When the phytoplankton dies, they sink in the water column and are eaten by bacteria. These bacteria consumer oxygen and soon there isn’t enough to go around. This causes fish and other animals to become uncomfortable and leave these zones, but if they can not physically escape the zone, the animals suffocate.
Oxygen from surface waters usually replenishes the oxygen-starved bottom. But when the water column becomes stratified, a typically seasonal occurrence where water is separated into distinct layers of temperature, that replenishment may not happen. When all of the oxygen is used up, a new group of bacteria bloom with breath that can make these oxygen-starved waters smell of sulfur.
Dead zones have now been reported in more than 400 systems and affect a combined area of more than 245,000 square kilometers, an area roughly the size of the United Kingdom. The flow of nutrients, be it sewage or fertilizer, must be managed if dead zones are to recover. The causes of dead zones, as stated by a scientist, “are co-mingled with how we use and abuse the land and do...