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 老调重弹之 it's closer to heaven (Tahoe +Yosemite)（有照片有导游图） |
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多谢大家加星，并求教个问题, 送 1000归分 -- emperorfan - (1419 Byte) 2010-10-12 周二, 11:53 (544 reads) |
但求最好
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作者：但求最好 在 行行摄摄 发贴, 来自【海归网】 http://www.haiguinet.com
Great Salt Lake
Primary Producers (Algae and Photosynthetic Bacteria):
The primary producers in the lake are found in one of two habitats: planktonic (water column) or the benthic (bottom). The planktonic primary producers are referred to as phytoplankton and dominated by algae and a few bacterial species. Over the years of studies on the lake, roughly a dozen species of algae and a similar number of bacteria have been recorded. The lists compiled by some investigators is longer than that of others, however, few efforts have been carried out to culture the algae to determine if they are truly active or are simply tolerating the brine for a while after having been washed into the lake.
The planktonic algae are dominated by a variety of pennate diatoms in early spring and late autumn when they are apt to reach bloom proportions in numbers. In summer and occasionally in winter two species of Dunaliella (green algae) dominate. In the less saline south arm of the lake, Dunaliella viridis dominates, imparting a green cast to the water, whereas in the more saline north arm of the lake, Dunaliella salina dominates and this species produces beta-carotene in such large quantity that the water Qbecomes quite red in color. However, even the north arm is not saline enough for this species to reach maximum populations. This they do in the solar evaporation ponds of various companies that extract salts from the lake by concentrating brines. You may have noticed the brilliant red color of the solar evaporation ponds of GSL-Minerals & Chemicals as you fly over the lake in summer. Even the entire north arm develops a reddish color in summer due to this alga. Contributing somewhat to the red color of the north arm is the presence of Halobacterium, a bacterial species that accumulates a rhodopsin-type of pigment.
Two genera of blue-green algae or cyanobacteria are commonly found in the plankton. These are
Aphanothece and Coccochloris. These two genera along with the Dunaliella spp. along with the dozen or so bacterial species found in the south arm, provide the food for the grazing brine shrimp (Artemia franciscana). Diatoms, though valuable, are tougher for the brine shrimp to digest because of their thick silica cell walls.
Some of the bacteria found in the south arm belong to the following genera: Micrococcus, Bacillus, Achromobacter, Flavobacterium, Bacterioides, Serratia and Cellulomus.
The benthic habitat is dominated by blue-green algae (cyanobacteria) and some diatoms with the occasional green alga. These collectively cause the precipitation of calcium-carbonate (limestone) which accumulates as reefs on the bottom of the lake. These primary producers are especially active when the phytoplankton and brine shrimp numbers above decline and the resulting clear water allows light to penetrate to the bottom. The algal mats that develop are important as the food for two species of brine fly (genus Ephydra). These small insects spend their larval developmental stage grazing on this benthic community, later form pupae and emerge as adults in early summer. They form dense clouds that hover over the beaches and everything on the beach, including people. Many people are annoyed by the brine fly but they do not bite and are unique to brine environments. You may have noticed large wind-rows of pupae cases from these brine flies on the shore of the lake.
作者：但求最好 在 行行摄摄 发贴, 来自【海归网】 http://www.haiguinet.com
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