Marine Bacterial Abundance and Production Measured during the JGOFS Equatorial Pacific Process Study

During the fourth cruise (TT012), data were collected at 5 stations along 140 deg W longitude from 17 deg S latitude to the equator. Samples for measuring bacterial production and abundance were collected in the top 200m using the rosette CTD trace-metal-free water sampler. Bacterial production was measured by thymidine incorporation and leucine incorporation.

For thymidine incorporation, samples were amended with methyl-3H-thymidine and incubated at in situ water temperature for 1-3 hr. Incubation was terminated with formalin. The samples were then filtered through cellulose nitrate membranes of 0.22 micrometer pore size.

The filters were packed into scintillation vials and dissolved in ethyl acetate. The samples were then counted aboard ship on the scintillation counter. Leucine incorporation was estimated in parallel with the thymidine incorporation.

Samples were inoculated with 3H-leucine and unlabeled leucine and processed as above. Bacterial abundance was measured using a video image analysis system connected to a microscope. Length, width, perimeter and area of approximately 300 cells/sample were measured.

Biovolumes and biomass can be calculated from the image analyzer's estimates of perimeter and area, using certain algorithms. The data is public domain and can be retrieved on-line at "usjgofs.whoi.edu/jg/dir/jgofs/" [The information in this summary was derived from the JGOFS World Wide Web pages.]