Malits, A. A. Institut de Ciències del Mar (CSIC),
Arin, L. L. Institut de Ciències del Mar (CSIC),
Marrasé, C. C. Institut de Ciències del Mar (CSIC),
Peters, F. F. Institut de Ciències del Mar (CSIC),
Sala, M. M.M. Institut de Ciències del Mar (CSIC),

We have performed microcosms experiments with enclosed natural seawater populations from the oligotrophic coastal surface Westmediterranean waters to test whether different levels and duration of turbulence resulting in the same energy input can effect differently the microbial population. Without nutrient addition there was no significant difference between stagnant and turbulent treatments and chlorophyll concentration, bacterial DAPI counts, bacterial production and microbial respiration remained low throughout the experiment. In the experimental chambers spiked with inorganic nutrients the phytoplankton biomass and bacterial production increased in the turbulent treatments with no significant difference between intermittent turbulence (0,14cm2s-3 for two days) and continuous one (0,055cm2s-3 throughout the entire experimental period) and remained low under undisturbed conditions.Calculated bacterial growth efficiencies were higher in the turbulent treatments (62%) with respect to the stagnant one (47%). Labile DOC is continuously being released to the water by phytoplankton exudation and providing the substrate for bacterial growth. Under substrate limitation bacteria grow less efficiently because more substrate is respired to support cellular maintenance energy, while with sufficient substrate more energy is built into particulate carbon. Thus, planktonic bacteria can benefit from small-scale turbulence indirectly due to enhanced phytoplankton production.
Day: Tuesday, Feb. 2
Location: Sweeney Center
Code: SS02TU0054S