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

The Equatorial Pacific Process Study (EQPAC) was conducted along 140 deg W
longitude during 1992.

Four cruises took place: February 3 - March 9, March 19 - April 15,
August 5 - September 18, and September 24 - October 21. A fifth benthic
cruise and sediment trap legs were added. During the first cruise
(TT007), 15 stations were occupied along 140 deg W longitude from
12 deg N latitude to 12 deg S latitude. During the second cruise
(TT008), data were collected at 8 stations along 140 deg W longitude
from 9 deg S latitude to 9 deg N latitude. During the third cruise
(TT011), data were collected at 15 stations along 140 deg W from 12 deg N
latitude to 12 deg S latitude. 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
"http://usjgofs.whoi.edu/jg/dir/jgofs/"

[The information in this summary was derived from the JGOFS
World Wide Web pages.]