1/17/95      Cruise Update from R/V THOMPSON

	We are steaming SW to our station at 10'N, 65'E. The THOMPSON
departed Muscat at 0800 1/8/95 and ran the JGOFS stations in a
clockwise direction beginning at 22'23N, 59'53E. Along this northern
transect, surface water temperatures have averaged around 25'C, the
depth of the mixed layer averaged around 75 m; and, a well developed
oxygen minimum exists from around 75 to 1200 m. Surface nitrate has
ranged from 1.7 to 3.7 uM; surface ammonium 0.18 to 0.58; and, surface
silicate 1.6 to 2.8 uM. The surface waters are well mixed, with little
variation in chemical and biological parameters above the pycnocline.
Fe concentrations were around 2 nM at the inshore stations and have
decreased to values around 1 nM in the central and eastern Arabian Sea
(Measures). Mixed layer total organic carbon concentrations (Peltzer,
Waterhouse) have varied between 70 and 80 uM, with the highest TOC
observed at 21'11N, 63'33E. Secondary TOC maxima have been observed at
several stations between 2  - 300 m. Mixed layer POC determined by
difference between TOC (unfiltered) and DOC (filtered) samples was
about 3 - 5 uM. Deepwater concentrations of TOC are on the order of 38
- 40 uM, or roughly mid-way between deepwater values from the North
Atlantic and Equatorial Pacific. Concentrations of total chlorophyll a
in the mixed layer did not vary systematically over the northern
transect, ranging from 400 to 800 ng/L; however, the composition of the
phytoplankton community changed gradually from diatom dominated to
flagellate/cyanobacteria dominated (Goericke, Thompson). Preliminary
estimates of primary production at our first station based on 14C
(Knudson, Lindley) was  2 - 4  gC/m2/day at the first few stations.
Net carbon production based on oxygen changes (Dickson, Orchardo) were
2.1 to 3.8 gC/m2/day along the northern transect.  Bacterial production
estimates have ranged from 1.3 to 0.5 gC/m2/day proceeding from off the
coast of Oman to the central Arabian Sea (Azam, Smith and Steward).
Zooplankton abundance appeared to be greater at the northern stations
off the Omani coast and has decreased as we traversed the Arabian Sea.
Lowest zooplankton abundances occur from 150 - 600 m in the oxygen
minimum zone, but with a daytime layer at 200 - 300 m (Wishner and
Gowing). Dilution experiments gave preliminary estimates of
phytoplankton growth of 0.75 d-1 and phytoplankton removal by protozoa
of 0.4 d-1 (Caron and Dennett).

	Larger biota observed have included dolphins, Indo-Pacific blue
marlins (2, 6' marlin swam right past the CTD rosette), masked
boobies, red-billed tropic birds, dolphin fish, big-eyed tuna and
squid. Today a cattle egret hitched a ride by sitting on an antenna.

	Captain Gomes and the crew of the THOMPSON have been great. The
ETs Grogan and Realander have put in long hours and exhibited great
patience in helping us trouble shoot equipment problems. Lou Codispoti
has assembled talented people on the Hydro-team whose performance
drawing and analyzing water samples would rival any Indy 500 pit crew.

	We are catching up on samples and sleep on this long steam. The
southern transect has a higher density of stations as well as 5 long
stations (40 h), which prove to be a bit hectic.

	We have had light winds, calm seas and sunny days throughout
the cruise.


mike roman is sci-01@thompson.ocean.washington.edu