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Case Studies (332)
Lake Pontchartrain, USA
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Summary
Hypoxia in Lake Pontchartrain was first documented in the 1970s. It was estimated to cover 250km2 (another estimate is 421km2). Hypoxia has caused reduced species diversity and a loss of large clams.
Type of regime shift
Ecosystem type
- Marine & coastal
- Freshwater lakes & rivers
Land uses
- Fisheries
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- Southern USA
Countries
- United States
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Key References
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Committee on Environment and Natural Resources. 2010. Scientific Assessment of Hypoxia in U.S. Coastal Waters. Interagency Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science and Technology. Washington, DC.
Citation
North San Francisco Bay Estuary, USA
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Summary
Hypoxia in the North San Francisco is episodic. Anoxia causing fish kills were documented for the first time in the2000s. Recent water treatment improvements have decreased organic loading and nutrient discharges into the bay.
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Fisheries
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- California
Countries
- United States
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Key References
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Committee on Environment and Natural Resources. 2010. Scientific Assessment of Hypoxia in U.S. Coastal Waters. Interagency Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science and Technology. Washington, DC.
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Luoma S, Cloern J. 1982. The impact of waste water discharge on biological communities in San Francisco Bay. Available online http://wwwrcamnl.wr.usgs.gov/tracel/references/pdf/SFBay-Use-Protection_p137.pdf (last accessed 8.12.2011)
Citation
Coyote Creek, USA
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Summary
Coyote Creek is a river emptying into San Francisco Bay. In 1979, a breakdown of a waste treatment plant caused a significant discharge of partly-treated waste into the South San Francisco Bay through Coyote Creek. The decomposition and nitrification of the sewage components depleted dissolved oxygen and caused hypoxia and anoxia. Fishermen reported absence of fish and pelagic invertebrates. Water quality improved rapidly after treatments and fish returned after the end of hypoxia. It is unclear exactly how much the sewage spill affected South San Francisco Bay fauna.
Type of regime shift
Ecosystem type
- Freshwater lakes & rivers
Land uses
- Fisheries
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- California
Countries
- United States
Locate with Google Map
Key References
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Cloern J, Oremland R. 1983. Chemistry and microbiology of a sewage spill in south San Francisco Bay. Estuaries 6, 399,406.
Citation
Tampa Bay, USA
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Summary
Tampa Bay has shown clear eutrophication since the late 1970s. Hypoxia and anoxia developed in some areas of Tampa Bay already in the 1970s. Human population in the area has grown significantly larger since the 1950s and therefore the inputs to the bay have increased. Improved nutrient management since the early 1980s has improved Tampa Bay water quality.
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Fisheries
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- Florida
Countries
- United States
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Key References
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Greening H, Janicki A. 2006. Toward Reversal of Eutrophic Conditions in a Subtropical Estuary: Water Quality and Seagrass Response to Nitrogen Loading Reductions in Tampa Bay, Florida, USA. Environmental Management 38, 163-178.
Citation
Looe Key, USA
Main Contributors:
Other Contributors:
Summary
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Conservation
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- Florida Keys
Countries
- United States
Locate with Google Map
Key References
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Lapointe B. 1992. Nutrient inputs form the watershed and coastal eutrophication in the Florida Keys. Estuaries 15, 465-476.
Citation
Connecticut River, USA
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Other Contributors:
Summary
Episodic hypoxic events occur in the 12km2 area in the tidal freshwater zone of Connecticut River.
Type of regime shift
Ecosystem type
- Freshwater lakes & rivers
Land uses
- Fisheries
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- East coast of North America
Countries
- United States
Locate with Google Map
Key References
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Diaz R, Rosenburg R. 2008. Spreading dead zones and consequences for marine ecosystems. Science 321, 926-929.
Citation
Charlotte Harbor, USA
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Summary
Charlotte Harbor is a natural estuary and one of the most productive wetlands in Florida. Hypoxia in Charlotte Harbor is episodic and usually occurs during the July to September rainy season. It is caused by stratification due to freshwater inflow and high temperatures. Wet season hypoxia is suggested to also be partly caused by increased anthropogenic nutirent loads within the harbor.
In 2003 Hurricane Charley hit the Charlotte Harbor and Peace River. Hurricane Charley was followed by hypoxia and nearly anoxia in Charlotte Harbor two weeks after the landfall. Three weeks after the Hurricane Charley, another hurricane named Frances caused further damage and heavy rain in Charlotte Harbor. Two weeks after Hurricane Frances, Hurricane Jeanne arrived. Temporal patterns of hypoxia varied and it took approximately three months for the Peace River oxygen content to recover back to pre-hurricane levels. There appear to be no previous observations for the combination of widespread hypoxia in both the Harbor and throughout the majority of the watershed of the Peace River.
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Fisheries
- Conservation
- Tourism
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- Southwest Florida
Countries
- United States
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Key References
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Tomasko DA, Anastasiou C, Kovach C. 2006. Dissolved oxygen dynamics in Charlotte Harbor and its contributing watershed, in response to Hurricanes Charley, Frances and Jeanne - Impacts and recovery. Estuaries and Coasts 293 932-938.
Citation
Alamitos Bay, USA
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Summary
Severe hypoxia, which has resulted in mass mortality of fish and invertebrates, has been observed within the California Current system. Occurring in an upwelling system, hypoxia in the California coast reflects conditions in the ocean systems that deliver oxygen-poor water onto continental shelves: Hypoxia may represent climatic variability (e.g. wind stress anomalies), shifts in ocean circulation and marine ecological change. As typical to the semi-enclosed seas and estuaries, anthropogenic nutrient loading has increased hypoxia in the Alamitos Bay.
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Urban
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- North America
Region
- Pacific coast of USA
Countries
- United States
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Key References
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Grantham B, Chan F, Nielsen K, Fox D, Barth J, Huyer A, Lubchenco J, Menge B. 2004. Upwelling-driven nearshore hypoxia signals ecosystem and oceanographic changes in the northeast Pacific. Nature 429, 749-754.
Citation
Pak Phanang, Thailand
Main Contributors:
Other Contributors:
Summary
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Fisheries
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- Asia
Region
- East coast of peninsular Thailand
Countries
- Thailand
Locate with Google Map
Key References
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Foulkes M, Rattanachongkiat S, Utoomprukporn W, Taiyaqupt M, Tantichodok P, Chongprasith P, Willward G. 2007. Water Chemistry and Arsenic Concentrations in Pak Panang Bay, Southern Thailand: Influences of the North East Monsoon. Journal of Coastal Research 23, 731–739.
Citation
Gullmarsfjord, Sweden
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Other Contributors:
Summary
Gullmarsfjord has a maximum depth of 118m with stagnant bottom water which is usually renewed with oxygen-rich deep water every spring. Hypoxia in Gullmarsfjord is episodic with a clear seasonal trend. Hypoxia evolves in autumnn and winter. It has caused mass mortality for instance in the winter of 1979-1980.
In 1997-1998 the hypoxic period was longer than ever before reported due to failed bottom water exchange in 1997. Since the water exchange didn't occur, the dissolved oxygen content continued to decrease. The fauna died at depths below 100m and was significantly reduced in depths between 80-100m. In 1998 the oxygen content slightly increased in January and a major bottom water renewal took place again in the spring.
Type of regime shift
Ecosystem type
- Marine & coastal
Land uses
- Conservation
Spatial scale of the case study
- Local/landscape (e.g. lake, catchment, community)
Continent or Ocean
- Europe
Region
- North Europe
Countries
- Sweden
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Key References
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Nilsson H, Rosenberg R. Succession in marine benthic habitats and fauna in response to oxygen deficiency: analysed by sediment profile-imaging and by grab samples. Marine Ecology Progress Series 197, 139-149.
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Rosenberg R, Agrenius S, Hellman B, Nilsson H, Norling K. 2002. Recovery of marine benthic habitats and fauna in a Swedish fjord following improved oxygen conditions. Marine Ecology Progress Series 234, 43-53.
