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Response of Thermal Algal-bacterial Mat to Grazing by Brine Flies

出版	Springer-Verlag, 1980
URL	http://books.google.com.hk/books?id=Vmf6zgEACAAJ&hl=&source=gbs_api

註釋Gelatinous mats of blue-green algae (cyanobacteria) and bacteria in alkaline thermal springs of Yellowstone National Park add biomass at the surface more rapidly than material is degraded in the anaerobic layers underneath. This inequality leads to flow diversion and exposure of mat surface. The microenvironmento f these cool exposed "islands" is drasticallya ltereda s adults and larvae of ephydrid fly species invade, feed on, and solubilize the mat. We studied the effect of this grazing by comparing hot and cool ungrazed controls with mat that was cooled and remained open to invasion by ephydrid flies. Mat community biomass changes (ash free dry weight-AFDW) and changes in bacterial numbers were determined. Mat biomass was essentially unchanged for 3 weeks in the controls. Numbers of bacteria remained unchanged in the cool ungrazed control but decreasedb y more than 90% in the hot-ungrazedc ontrol. Grazingb y ephydrid flies initially increased both mat biomass and numbers of unicellular heterotrophic bacteria. When grazed mat was reexposed to flowing hot water, biomass and bacterial numbers per mg AFDW declined immediately and significantly. The long-term effect of grazing on the mat is solubilization with downstream biomass export and subsequenti nitiationo f successionala lgal-bacteriaml at regrowth.O ur experimentalr esultss uggest an initial stimulationo f net photosynthesisb y grazing, possibly related to the promotion of bacterial activity resulting in the release of essential mineral nutrients and/or free CO2.