Epiphytic bacterial production on Zostera marina

This study tested if epiphytic bacteria on Zostera marina L. (eelgrass) could obtain sufficient organic carbon from leaf photosynthesis to support their production. When individual Z. marina leaves were placed with tips in dark chambers and bases in illuminated chambers and sodium 14C-bicarbonate was injected Into the illuminated chambers, radioactivity appeared in the dark chambers only by translocation through the leaves. The flux of organic carbon from Z. man'na to the bacteria was approximately 0.3 pgC h-' cm-' while the highest bacterial production, based on 3H-thymid~ne incorporation rates, was 0.4 pgC h-' cm-'. DOC excretion rates from Z. marina leaves were approximately 2 % of total carbon fixation. Bacterial abundance and 3H-thym~dine incorporat~on rates increased significantly from the bases to tips of the leaves. These data demonstrate that the epiphytic bacterial population is supported almost entirely by carbon obtained directly from 2. marina photosynthesis.