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ShareDead zones are hypoxic (low-oxygen) areas in the world's oceans, the observed incidences of which have been increasing since oceanographers began noting them in the 1970s.
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The term could as well apply to the identical phenomenon in large lakes.
Aquatic and marine dead zones can be caused by the process of eutrophication, triggered by an excess of plant nutrients (nitrogen and phosphorus) from fertilizers, sewage, combustion emissions from vehicles, power generators, and factories.
In a cascade of effects, the nutrients trigger a bloom of phytoplankton at the bottom of the marine food chain, allowing zooplankton to proliferate.
As phytoplankton and zooplankton die and sink below the photic zone where photosynthesis can occur, a bloom of natural bacterial degradation exhausts the water's dissolved oxygen.
Low oxygen levels recorded along the Gulf Coast of North America have led to reproductive problems in fish involving decreased size of reproductive organs, low egg counts and lack of spawning.
For more information about the topic Dead zone (ecology), read the full article at Wikipedia.org, or see the following related articles:
Eutrophication — Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both. ... > read more
Algal bloom — An algal bloom or marine bloom or water bloom is a rapid increase in the population of algae in an aquatic system. Algal blooms may occur in ... > read more
Phytoplankton — Phytoplankton refers to the autotrophic component of the plankton that drifts in the water column. Most phytoplankton are too small to be ... > read more
Red tide — "Red Tide" is a common name for a phenomenon known as an algal bloom, an event in which estuarine, marine, or fresh water algae accumulate rapidly in ... > read more
Carbon cycle — The carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the Earth. ... > read more
Gulf of Mexico — The Gulf of Mexico is a major body of water bordered and nearly landlocked by North America. Because of the ever increasing amount of nitrogen and ... > read more
Sea water — Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of approximately 3.5%, or 35 parts per thousand. ... > read more
Trophic level — In ecology, the trophic level is the position that an organism occupies in a food chain - what it eats, and what eats it. Wildlife biologists look at ... > read more
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