From: Wecoma Chief Scientist
Subject: Wecoma report for 25-27 Jan '03

COAST R/V Wecoma report
25-27 January 2003

During Saturday to Monday, 25-27 January, we completed the following sampling:

-- a complete CH-line section with CTDs and vertical zooplankton nets at stations 1-10 and MOCNESS stations at CH-3,5(nighttime),7 and 5(daytime)
-- a SeaSoar/ADCP/HTI iron survey on a "ladder" between the 100 and 150-m isobaths from line C to line 1
-- a SeaSoar/ADCP/HTI/iron survey on the BigBox (lines 1-3) grid (3nd repeat)

Winds were blowing 25-30 knots from the south during the entire CH-line sampling. We were able to MOCNESS through the wind and waves. During the MOCNESS at CH-7, rain was falling in sheets. Thanks to the OSU MarTechs and SeaSoar flyers for their long, dedicated day helping with the biological sampling. Bill, you owe them. See Jessie Lamb and Jaime Gomez's report below for more about the biological sampling.

Near CH-3 during the station work, we pulled all our gear onboard and pulled close to Revelle as they sampled inshore at 2 knots. They put a package overboard with some chemistry gear for Dale Hubbard. Wecoma manuevered smartly alongside (Thanks Gary!) and we fished the package onboard. Dale Hubbard got the silicate system running on the underway 5-m flow-through line after installing the LED he received from the Revelle. So now he has a complete nutrient (nitrate+nitrite, phosphate, silicate) and pCO2 system working.

After completing station work at CH-4 we did a visual inspection of the MET buoy upon Murray Levine's request after they lost air temperature and relative humidity during the 23 January storm. There was no apparent damage to the met tower, but we did observe two yellow balls floating about 100 m from the met buoy. Murray confirmed that these are tethered to the anchor for use during its recovery and had evidently prematurely released.

Winds dropped down to 10 knots or less on late Sunday and Monday. We're really enjoying the ride! The Revelle pulled close to us off Lincoln City on Sunday afternoon. We kept station while we switched from MOCNESS back to SeaSoar operations. Revelle was doing a pump station at CH-1. It's suspicious that both vessels were close to shore during the Super Bowl :)

We towed SeaSoar/HTI/ironfish without incident on BigBox 3. While close inshore off Lincoln City (near CH-1) we passed through a strong surface color front around the 40-m isobath with an attendant drop in surface wave height. Our light attenuation meter showed a strong increase in particles in this relatively fresh water. Silicate increased from about 5 uM offshore to 20 uM in the fresh lens. Phospate and nitrate+nitrite stayed constant. Iron levels reported by Roseanne Schwartz and Linda Baker increased from below detection levels to 2 nM offshore to about 5 nM in the fresh water. All these signals are consistent with a freshwater source, most likely the Siletz River. The freshwater forms a buoyant lens inshore, inhibiting top to bottom mixingas observed over the mid shelf.

We are about to recover SeaSoar/HTI/ironfish and begin a series of deep CTD stations along the slope from south to north in an effort to pin down the 3D variability of the bottom downwelling front. We'll then do another tow on the SmallBox North grid on Tuesday.

Jack Barth
Chief Scientist, R/V Wecoma
2000, 27 Jan 2003

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Zooplankton Report from Jesse Lamb and Jaime Gomez

Zooplankton tows were performed on Saturday, 1/25, with one station (CH-5) repeated for day/night comparison. Tows were performed with 1/2-m vertical net, which captures the water column above 100m, and with a MOCNESS, which captures certain depth strata with its multiple nets.

All net tows went smoothly, with the exception of the CH-2 MOCNESS tow, which was attempted twice because of the nets failing to trip. Due to time constraints, we moved directly to CH-3, and the problem was corrected.

CH-3 and both of the CH-5 net tows yielded the same contents: very small amounts of smaller copepods. There was little variation in the amounts of animals caught in each net representing defined strata. Small samples were out of the MOCNESS zero nets, which collect animals from the entire water column, to see which species they contained. The species found in highest abundancewere Metridia sp., Paracalanus sp., and Calanus pacificus - all off-shelf, warm water species, which are consistent with dowelling. However, there were some Calanus marshallae and Pseudocalanus, which are 'on-shelf, cold water' species, usually associated with upwelling. There were also some younger stage euphausids (furcilia) found mixed in these nets, which is also unusual for this time of year.

The net tows at station CH-7 yielded a surprising catch of mostly euphausid adults and juveniles. This station is found right at the shelfbreak, an area noted for having abundant euphausid populations. These were mixed in with Calanus marshallae females. The occurrence of these animals at this time ofyear could suggest an early spring bloom a couple of weeks before last weeksdownwelling events.