Ecophysiological and trophic implications of light-stimulated amino Acid utilization in marine picoplankton.

摘要: Abstract By using microautoradiography, light-stimulated utilization of dissolved amino acids for natural marine phytoplankton assemblages was demonstrated. The <2-μm-size (diameter) picoplankton, known to be a dominant fraction primary production, revealed widespread capability this process. Autofluorescent (chlorophyll a-containing) picoplankton and some larger from diverse oceanic locations, as well isolates the representative cyanobacterial Synechococcus spp. (WH7803, WH8101), showed incorporation at trace concentrations. Dark-mediated acid dominated by nonfluorescent bacterial populations. Among autofluorescent exceeded dark-mediated 5 75%; only partially blocked photosystem II inhibitor 3(3,4-dichloro-phenyl)-1,1-dimethy-lurea (2 × 10-5 M), suggesting photoheterotrophic mechanism. Parallel light versus dark incubations with glucose mannitol indicated lack these nonnitrogenous compounds. Since production is frequently nitrogen limited, light-mediated auxotrophic possibly other organic (DON) constituents may represent exploitation relatively large DON pool in face inorganic depletion. This process (i) increases efficiency retention base food webs (ii) part responsible high rates under conditions chronic limitation. Picoplanktonic recycling matter via has important ramifications respect trophic transfer “microbial loop.”