page_title: Hypoxia (environmental)
section_title: Solutions
hierarchical_section_title: Hypoxia (environmental) / Aquatic hypoxia / Solutions
caption_attribution_description: Français&#160;: Description: illustration de l'importance de la salinité dans certains phénomènes d’hypoxie, puis d’anoxie qui en freinant le mélange des couches d'eau exacerbe certains phénomènes de dystrophisation qui peuvent conduire au phénomène de "zone morte", généralement dans des milieux fermés et la nuit quand les plantes et le zooplancton, faute de soleil ne produisent plus assez d’oxygène pour les besoins des organismes animaux ou fongiques, ainsi des cellules végétales. Ici, il s’agit de mesures faites dans le Fjord Kiel (en Allemagne). English: An illustration of oxygen depletion in the Kiel fjord in September 1988. Based on a GIF (Image:Oxygendepletion2.gif) by Uwe Kils. The original image was on {{ifc}}, this is my attempt at cleaning it up. Data was extracted from the image using Perl. Mysid (talk) 11:52, 17 October 2005 (UTC)
context_page_description: Hypoxia refers to low oxygen conditions. Normally, 20.9% of the gas in the atmosphere is oxygen. The partial pressure of oxygen in the atmosphere is 20.9% of the total barometric pressure. In water, oxygen levels are much lower, approximately 7 ppm 0.0007% in good quality water, and fluctuate locally depending on the presence of photosynthetic organisms and relative distance to the surface.
context_section_description: To combat hypoxia, it is essential to reduce the amount of land-derived nutrients reaching rivers in runoff. This can be done by improving sewage treatment and by reducing the amount of fertilizers leaching into the rivers. Alternately, 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. Other natural habitat-based solutions include restoration of shellfish populations, such as oysters. Oyster reefs remove nitrogen from the water column and filter out suspended solids, subsequently reducing the likelihood or extent of harmful algal blooms or anoxic conditions. Foundational work toward the idea of improving marine water quality through shellfish cultivation was conducted by Odd Lindahl et al., using mussels in Sweden. More involved than single-species shellfish cultivation, integrated multi-trophic aquaculture mimics natural marine ecosystems, relying on polyculture to improve marine water quality.
  Technological solutions are also possible, such as that used in the redeveloped Salford Docks area of the Manchester Ship Canal in England, where years of runoff from sewers and roads had accumulated in the slow running waters. In 2001 a compressed air injection system was introduced, which raised the oxygen levels in the water by up to 300%. The resulting improvement in water quality led to an increase in the number of invertebrate species, such as freshwater shrimp, to more than 30. Spawning and growth rates of fish species such as roach and perch also increased to such an extent that they are now amongst the highest in England.
  In a very short time the oxygen saturation can drop to zero when offshore blowing winds drive surface water out and anoxic depth water rises up. At the same time a decline in temperature and a rise in salinity is observed (from the longterm ecological observatory in the seas at Kiel Fjord, Germany). New approaches of long-term monitoring of oxygen regime in the ocean observe online the behavior of fish and zooplankton, which changes drastically under reduced oxygen saturations (ecoSCOPE) and already at very low levels of water pollution.
caption: Graphs of oxygen and salinity levels at Kiel Fjord in 1998
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