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| Titel: |
Sulfide irruptions and gypsum blooms in the Salton Sea as detected by satellite imagery, 1979-2006 |
| Auteur: |
Tiffany, Mary A. Ustin, Susan L. Hurlbert, Stuart H. |
| Verschenen in: |
Lake and reservoir management |
| Paginering: | Jaargang 23 (2007) nr. 5 pagina's 637-652 |
| Jaar: |
2007-12-01 |
| Inhoud: |
Bright pale-green surface waters, locally called “green tides,” are visible to the naked eye and satellite sensors in patches at the Salton Sea, usually between May and November. These were studied using satellite remote sensing and by direct sampling. Algal blooms are ruled out as a cause as phytoplankton abundance, and chlorophyll concentrations were lower within the patches than in surrounding areas. The presence of abundant microscopic gypsum (CaSO4·2H2O) crystals in surface waters suggests that scattering from this precipitating salt produces the intense signals. Biogeochemical factors include: the decomposition of organic matter, resultant anoxia and production of hydrogen sulfide by sulfate-reducing bacteria at depth, and oxidation back to sulfate and precipitation of gypsum during wind-induced overturn events. Sulfide concentrations following one such event in September 2005 ranged from 0.3 to 2.7 mg 1-1 at the surface and 1.2 to 25 mg 1-1 in bottom waters. Gypsum crystals occurred at densities up to 40,000 ml-1 in surface water on that date, most 20-30 μm in length with some as long as 190 μm. From 1998 to 2006, gypsum blooms appear to have increased in intensity and duration implying an increase in sulfide irruptions and anoxia in surface waters. As much as 97 percent of the lake was affected in early summer of 2003 and 75-80 percent in summers of 2005 and 2006. Events lasted for months at a time during these years. This intensification is likely due to the decline in abundance of a planktivorous fish, a hybrid tilapia, the California Mozambique mouthbrooder, leading to increased algal productivity, more severe anoxia and higher levels of dissolved hydrogen sulfide. Gypsum blooms seem to have occurred at least as far back as the 1970s, and are associated with frequent mass mortalities of fish, plankton and benthos. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 13 van 13 gevonden artikelen
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