by Bj Anderson

Created on: January 01, 2009

Ocean dead zones are literally that, in being a marine Plutonian sector void of life with the seafloor littered in an oceanic macrocosm of skeletal remains garroted in a layer of matted, slimy bacteria. Sea life that are mobile enough and weren't rendered unconscious were able to scurry off into healthier environs. The ones that were sessile or slow to move weren't as fortunate and died off in the dead zone's strangle hold. The culprit is a lack of dissolved oxygen (DO), which supports sea life. The current cause of depletion is primarily manmade and is twofold.

Overall, median sea life requires at the very minimum a 30% DO level of molecular saturation and thrives at 80% or above. When DO is taken out of a watery region, it is said to be hypoxic at DO levels between 1-30%. Below 1% virtually void of any oxygenated water, it is anoxic, where even aerobic bacteria cannot exist, much less higher life forms. What's causing depletion of DO in the world's oceans are high nutrient runoffs and rising temperatures from global warming.

River runoff that eventually makes its way into ocean and sea waters are loaded with organic sewage and pollution, plus nitrogen based fertilizers in the form of nitrites and nitrates that cause eutrophication once dumped into the deltas. In eutrophic induced environments, the nutrient rich influx is ideal for rapid plant growth. Algal blooms proliferate in this setting overwhelming fauna that normally feed on checked alga and plant populations. Millions of tons of individual algae die and settle to the bottom where they rapidly rot, decomposed by aerobic bacteria that in turn multiply absorbing and depleting DO at accelerated rates. Industrial pollutants further aggravate the depletion by displacing DO as freed gas removing it from the waters.

Coastal areas such as bays and fiords already have low flow rates making them more prone to siltation and stagnation. A coastal inlet may have a normal 6-8 ppm of DO, enough to support acclimated fauna. But, when levels drop to 1-2 ppm, due to river runoff with its accumulated manmade baggage, it stresses wildlife, deforming internal and reproductive organs shortening life spans and reproduction. Any further drops below the critical 1ppm of course cannot support life period. It either dies off or flees the region. This has occurred many times in Louisiana's Mississippi Delta and Chesapeake Bay in Maryland.

We all have heard of the detrimental effects of global warming on ocean bodies. In addition to

• 1
• 2
• Next Page >>