Hypoxia

{
  "id": "MLC-T-ENV-013770",
  "term": "Hypoxia",
  "field": "Environment",
  "definition": "1. A condition where there isn't enough oxygen in the water. This forces fish to either swim away or die and can suffocate plants living in the water. Hypoxia occurs when there are too many nutrients in the water.\n\n2. Low oxygen content or tension; deficiency of oxygen in the inspired air\n\n3. A condition in which oxygen levels in water are very low.\n\n4. Low oxygen; and is primarily a problem for estuaries and coastal waters. Hypoxic waters have dissolved oxygen concentrations of less than 2-3 ppm. Hypoxia can be caused by a variety of factors, including excess nutrients, primarily nitrogen and phosphorus, and waterbody stratification due to saline or temperature gradients. These excess nutrients, eutrophication, promote algal growth. As dead algae decompose, oxygen is consumed in the process, resulting in low levels of oxygen in the water.” - Mississippi River Basin Watershed Nutrient Task Force, 2010\n\n5. Condition in which oxygen levels in water are very low. [Chesapeake Bay Glossary]\n\n6. Occurrence of low dissolved oxygen concentrations in water. Hypoxia is generally defined with respect to oxygen saturation; because saturation levels vary with temperature and salinity, the concentration that defines hypoxia may vary seasonally and geographically. In practice, scientists often use a threshold of 2 parts per million, the generally accepted minimum required for most marine life to survive and reproduce.\n\n7. Low Oxygen (oxygen depletion) levels in water can occur naturally for short periods, but when they are extreme or long-lasting, they can sicken and even kill fish and other aquatic life. Sewage wastewater, leaking septic tanks, farm and feedlot runoff, and stormwater runoff contain organic materials that decompose and use up oxygen in water. Higher water temperatures can lead to lower oxygen levels.\n\n8. The occurrence of low dissolved oxygen concentrations in water. Hypoxia is generally defined with respect to oxygen saturation; because saturation levels vary with temperature and salinity, the concentration that defines hypoxia may vary seasonally and geographically. In practice, scientists often use a threshold of 2 parts per million, the generally accepted minimum required for most marine life to survive and reproduce.",
  "subject": "Ecosystems",
  "references": [
    "Estuaries Glossary",
    "Chemical Emergency Preparedness and Prevention Glossary",
    "Chesapeake Bay Glossary; N-STEPS Online Glossary of Terms",
    "USGS Toxic Substances Hydrology Program Definitions",
    "NSTEPS Online Glossary of Terms",
    "Report on the Environment (ROE) Glossary",
    "How's My Waterway Glossary"
  ],
  "url": "https://mlchart.com/terminology/environment/hypoxia/"
}