Ecological Impacts
Marine Life:
Figure 22: State Library Gulf Of Mexico AKA 'The Dead Zone'.pdf)
This table shows the relationship between the dissolved oxygen level and the presence of organisms. If the oxygen level is below 0.5 mg/l, the environments it becomes unsustainable for any type of marine life. In other words, this table shows us the impact of dead zones on marine life, as it can lead to fish kills and death of aquatic organisms.
Science Codex summarises the impacts on marine life:
(http://www.sciencecodex.com/dramatic_expansion_of_dead_zones_in_the_oceans)
Extreme events of ocean oxygen depletion leading to anoxia are thought to be prime candidates for explaining some of the large extinction events in Earth history including the largest such event at the end of the Permian 250 million years ago.
Furthermore, as suboxic zones expand, essential nutrients are stripped from the ocean by the process of denitrification. This in turn would shift biological production in the lighted surface layers of the ocean toward plankton species that are able to fix free dissolved nitrogen. This would then lead to large, unpredictable changes in ocean ecosystem structure and productivity, on top of other large unpredictable changes to be expected from ocean acidification, the other great oceanic consequence of high atmospheric carbon dioxide concentrations from fossil fuel burning.
Not only is local sea life damaged, but the effects of the mutant local ecologies within the dead zones are spreading throughout the world. Certain less-tolerant fish and creatures are being killed, while those that are able to tolerate poisons, as well as those that feed on algae or resultant bacteria, multiply.
This unbalance has a destabilizing effect on other creatures that rely on the affected life for food. In addition, other life may run rampant—unchecked—when its natural predators are destroyed. This could potentially wreak havoc on global ecosystems since all life is interdependent. (http://realtruth.org/articles/070831-001-mdz.html)
This table shows the relationship between the dissolved oxygen level and the presence of organisms. If the oxygen level is below 0.5 mg/l, the environments it becomes unsustainable for any type of marine life. In other words, this table shows us the impact of dead zones on marine life, as it can lead to fish kills and death of aquatic organisms.
Science Codex summarises the impacts on marine life:
(http://www.sciencecodex.com/dramatic_expansion_of_dead_zones_in_the_oceans)
Extreme events of ocean oxygen depletion leading to anoxia are thought to be prime candidates for explaining some of the large extinction events in Earth history including the largest such event at the end of the Permian 250 million years ago.
Furthermore, as suboxic zones expand, essential nutrients are stripped from the ocean by the process of denitrification. This in turn would shift biological production in the lighted surface layers of the ocean toward plankton species that are able to fix free dissolved nitrogen. This would then lead to large, unpredictable changes in ocean ecosystem structure and productivity, on top of other large unpredictable changes to be expected from ocean acidification, the other great oceanic consequence of high atmospheric carbon dioxide concentrations from fossil fuel burning.
Not only is local sea life damaged, but the effects of the mutant local ecologies within the dead zones are spreading throughout the world. Certain less-tolerant fish and creatures are being killed, while those that are able to tolerate poisons, as well as those that feed on algae or resultant bacteria, multiply.
This unbalance has a destabilizing effect on other creatures that rely on the affected life for food. In addition, other life may run rampant—unchecked—when its natural predators are destroyed. This could potentially wreak havoc on global ecosystems since all life is interdependent. (http://realtruth.org/articles/070831-001-mdz.html)
Loss of Habitat and Biodiversity
Figure 23:
In this figure, the relationship between the oxygen concentration, biodiversity and biomass is shown in benthic zones.
As the oxygen concentration decreases, there is a increasing loss of biodiversity as well as a decline in numbers. When the oxygen level reaches less than 2mg/l in the darker sediment(poor oxygen), there is few to no benthic organisms.
Loss of biodiversity can also be caused through the oxygen concentration as it creates an unnatural selection for what organisms reside in certain areas. These areas will only be left with organisms who are capable or surviving and thus limit the types of species. Most dead zones become unsuited to live and cease to be habitats for the marine life.
In this figure, the relationship between the oxygen concentration, biodiversity and biomass is shown in benthic zones.
As the oxygen concentration decreases, there is a increasing loss of biodiversity as well as a decline in numbers. When the oxygen level reaches less than 2mg/l in the darker sediment(poor oxygen), there is few to no benthic organisms.
Loss of biodiversity can also be caused through the oxygen concentration as it creates an unnatural selection for what organisms reside in certain areas. These areas will only be left with organisms who are capable or surviving and thus limit the types of species. Most dead zones become unsuited to live and cease to be habitats for the marine life.
Economical and Social Impacts:
Fishing Industry
The Gulf of Mexico alone provides 1.7 billion pounds of fish and shellfish which is worth $26 billion to the fishing industry. Coincidentally, gulf of mexico is also hosts one of the biggest dead zones in the world, and hence we can see the detrimental impacts it has on coastal states, global food supply and fisheries.
For Louisiana fishermen, the dead zone amounts to about 235,000 tons or 470 million pounds of seafood lost every year, said Paul Greenberg, author of Four Fish: The Future of the Last Wild Food.
The National Oceanic and Atmospheric Administration, or NOAA, which funded the scientists' research, estimates that the dead zone costs U.S. seafood and tourism industries $82 million a year. The impact could be devastating to the Gulf's seafood industry, which accounts for more than 40 percent of the nation's seafood. Louisiana is second in seafood production only to Alaska. (http://www.nature.org/ourinitiatives/regions/northamerica/areas/gulfofmexico/explore/gulf-of-mexico-dead-zone.xml)
The Gulf produces roughly 40 percent of all the seafood in the lower 48 states. The National Oceanic and Atmospheric Administration has previously estimated that the dead zone costs the U.S. seafood and tourism industries $82 million a year. The record size of this year's dead zone could be even more costly. (http://www.huffingtonpost.com/mark-tercek/gulf-dead-zone-threatens-_b_916389.html)
For Louisiana fishermen, the dead zone amounts to about 235,000 tons or 470 million pounds of seafood lost every year, said Paul Greenberg, author of Four Fish: The Future of the Last Wild Food.
The National Oceanic and Atmospheric Administration, or NOAA, which funded the scientists' research, estimates that the dead zone costs U.S. seafood and tourism industries $82 million a year. The impact could be devastating to the Gulf's seafood industry, which accounts for more than 40 percent of the nation's seafood. Louisiana is second in seafood production only to Alaska. (http://www.nature.org/ourinitiatives/regions/northamerica/areas/gulfofmexico/explore/gulf-of-mexico-dead-zone.xml)
The Gulf produces roughly 40 percent of all the seafood in the lower 48 states. The National Oceanic and Atmospheric Administration has previously estimated that the dead zone costs the U.S. seafood and tourism industries $82 million a year. The record size of this year's dead zone could be even more costly. (http://www.huffingtonpost.com/mark-tercek/gulf-dead-zone-threatens-_b_916389.html)