Dead zone

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. In a study of the Gulf killifish by the Southeastern Louisiana University done in three bays along the Gulf Coast, fish living in bays where the oxygen levels in the water dropped to 1 to 2 parts per million (ppm) for 3 or more hours per day were found to have smaller reproductive organs. The male gonads were 34 to 50% as large as males of simil ...

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Dead zone, Dead zone - Causes of dead zones, Dead zone - Effects of dead zones, Dead zone - Locations of dead zones, Dead zone - Reversal of dead zones

Read more here: » Dead zone: Encyclopedia II - Dead zone - Effects of dead zones

An algal bloom is a relatively rapid increase in the population of (usually) phytoplankton algae in an aquatic system. Typically only one or a few species are involved and the bloom is recognized by discoloration of the water resulting from the high density of pigmented cells. Although there is no officially recognized threshold level, algae are unlikely to be considered to be blooming unless more than 10,000 cells per millilitre occur. Algal bloom concentrations may reach millions of cells per millilitre. C ...

Including:

• Algal bloom - Red tide
• Algal bloom - Black water
• Algal bloom - Water treatment

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The so-called red tide is an example of a naturally occurring estuarine or marine algal bloom. Red tide is caused by species of dinoflagellates, often present in sufficient numbers (thousands or millions of cells per milliliter) to turn the water red or brown. The species responsible for red tides on the gulf coast of Florida is a dinoflagellate called Karenia brevis (formerly Gymnodinium breve.) It produces brevetoxins which p ...

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Algal bloom, Algal bloom - Red tide, Algal bloom - Black water, Algal bloom - Water treatment

Read more here: » Algal bloom: Encyclopedia II - Algal bloom - Red tide

Oxygen depletion could be the result of a number of factors including natural ones, but is of most concern as a consequence of pollution and as a highly detrimental outcome of a process known as eutrophication. Where plant nutrients enter a river, lake, or ocean, phytoplankton blooms are encouraged. While phytoplankton, through photosynthesis, will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during the night. When phytoplankton cells die, they sink towards the bottom and are decomposed by ...

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Oxygen depletion, Oxygen depletion - Causes of hypoxia, Oxygen depletion - Solutions, Oxygen depletion - External link

Read more here: » Oxygen depletion: Encyclopedia II - Oxygen depletion - Causes of hypoxia

Oxygen depletion could be the result of a number of factors including natural ones, but is of most concern as a consequence of pollution and as a highly detrimental outcome of a process known as eutrophication. Where plant nutrients enter a river, lake, or ocean, phytoplankton blooms are encouraged. While phytoplankton, through photosynthesis, will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during the night. When phytoplankton cells die, they sink towards the bottom and are decomposed by ...

See also:

Oxygen depletion, Oxygen depletion - Causes of oxygen depletion, Oxygen depletion - Solutions, Oxygen depletion - External link

Read more here: » Oxygen depletion: Encyclopedia II - Oxygen depletion - Causes of oxygen depletion

To combat hypoxia, it is essential to reduce the amount of land-derived nutrients reaching rivers in runoff. Defensively this can be done by improving sewage treatment and by reducing the amount of fertilizers leaching into the rivers. Offensively this can be done by restoring natural environments along a river; marshes are particularly effective in reducing the amount of phosphorus and nitrogen (nutrients) in water. In a very short time the oxygen saturation can drop to zero when offshore blowing winds drive surface water out and ano ...

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Oxygen depletion, Oxygen depletion - Causes of oxygen depletion, Oxygen depletion - Solutions, Oxygen depletion - External link

Read more here: » Oxygen depletion: Encyclopedia II - Oxygen depletion - Solutions

To combat hypoxia, it is essential to reduce the amount of land-derived nutrients reaching rivers in runoff. Defensively this can be done by improving sewage treatment and by reducing the amount of fertilizers leaching into the rivers. Offensively this can be done by restoring natural environments along a river; marshes are particularly effective in reducing the amount of phosphorus and nitrogen (nutrients) in water. In a very short time the oxygen saturation can drop to zero when offshore blowing winds drive surface water out and ano ...

See also:

Oxygen depletion, Oxygen depletion - Causes of hypoxia, Oxygen depletion - Solutions, Oxygen depletion - External link

Read more here: » Oxygen depletion: Encyclopedia II - Oxygen depletion - Solutions

In the 1970s, marine dead zones were first noted in areas where intensive economic use stimulated "first-world" scientific scrutiny: in the U.S. East Coast's Chesapeake Bay, in Scandinavia's strait called the Kattegat, which is the mouth of the Baltic Sea and in other important Baltic Sea fishing grounds, in the Black Sea, (which may have been anoxic in its deepest levels for millennia, however) and in the northern Adriatic. Currently the most notorious dead zone is a 20,000 square kilometer region in the Gulf of Mexico, where the Mis ...

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Dead zone, Dead zone - Causes of dead zones, Dead zone - Effects of dead zones, Dead zone - Locations of dead zones, Dead zone - Reversal of dead zones

Read more here: » Dead zone: Encyclopedia II - Dead zone - Locations of dead zones

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 ...

See also:

Dead zone, Dead zone - Causes of dead zones, Dead zone - Effects of dead zones, Dead zone - Locations of dead zones, Dead zone - Reversal of dead zones

Read more here: » Dead zone: Encyclopedia II - Dead zone - Causes of dead zones