Limnology and Oceanography · 1994 · 483 citations · 0 references
Life SciencesMicrobiologyOceanographyMarine EcologyMarine MicrobiologyMicrobial EcologyMarine BacteriologyMicrobial BiogeochemistryMicrobial OceanographyMicrobial Plankton EcologyOcean EcologyPlankton DiversityBacterial Community EcologyMarine Bacterial EcologyMicrobial Community CompositionMicrobial Community DiversityMicrobial Plankton DiversityPlankton Community EcologyPlankton Community StructureProkaryotic Plankton
Microscopy-based assessments of oligotrophic ocean plankton may overestimate heterotrophic bacterial biomass. The study aims to demonstrate that the ratio of photosynthetic to heterotrophic bacterial biomass varies among oligotrophic ocean regions, refuting the idea that heterotrophic bacteria typically dominate. Prochlorococcus comprised 31 % of bacterial cells, contributed nearly half of the photosynthetic carbon, and overall photosynthetic biomass exceeded heterotrophic bacterial biomass (55 % vs 45 %) in the upper 200 m.
Assessments of plankton community structure in the oligotrophic oceans based solely on microscopy may overstate the importance of heterotrophic bacterial biomass. Using flow cytometry to distinguish heterotrophic bacteria from the photosynthetic procaryotes Prochlorococcus spp., we found that Prochlorococcus contributed 31% of total bacterial counts in the upper 100 m at station ALOHA (22°45′N, 158°W). In terms of carbon, procaryotic biomass was the largest component (≥ 80%) of the microbial community, but almost half of this was photosynthetic biomass contributed by Prochlorococcus . Overall, the total 200‐m integrated photosynthetic biomass exceeded heterotrophic bacterial biomass (55 vs. 45%). We suggest that the relative proportion of photosynthetic to heterotrophic bacterial biomass varies among oligotrophic regions of the ocean and that dominance by heterotrophic bacteria is not typical.