Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4397760 | Journal of Experimental Marine Biology and Ecology | 2007 | 8 Pages |
Abstract
Dilution experiments are used commonly to provide estimates of grazing pressure exerted on phytoplankton and bacterioplankton as well as estimate their growth rates. However, very little attention has been given to the dynamics of grazers, especially heterotrophic nanoflagellates (HNF), in such experiments. We found temporal changes in concentrations of ciliates and HNF in a dilution experiment using water from the oligotrophic N.W. Mediterranean Sea. Ciliates decreased markedly over 24Â h when held in seawater diluted with particle-free water (60% and 20% final conc whole seawater) while HNF increased in concentration in the same treatments. Using a time-course approach in a second experiment, we monitored changes in HNF and bacterioplankton concentrations in 20% whole seawater (80% particle-free seawater). Both HNF and heterotrophic bacteria displayed stable concentrations for the first 12Â h and then grew rapidly, especially HNF, from 12 to 24Â h. Examination of bacterial community composition using denaturing gel gradient electrophoresis (DGGE) showed a change in community composition over the 24Â h incubation period. Dilution can have differential effects on the distinct components of the marine microbial food web.
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Authors
Martin Agis, Angelica Granda, John R. Dolan,