From: Wecoma Chief Scientist
Subject: Wecoma report for 4-6 Feb '03

COAST R/V Wecoma report 4-6 February 2003

During Tuesday to Thursday, 4-6 Feb, we completed the following sampling:

-- CTD and zooplankton net sampling along the Cape Perpetua line on Heceta Bank (see Jesse Lamb and Jaime Gomez-Gutierrez's report below)
-- CTD stations along the inshore ends of lines 5 and 4 (the Newport Hydrographic Line) amongst heavy crab gear
-- a SeaSoar/ADCP/HTI/iron survey on the BigBox lines 1-4 grid (5th repeat)
-- a SeaSoar/ADCP/HTI/iron survey on the SmallBox North grid (8th repeat)

The winds continue to be upwelling favorable (southward) but with a significant westward component bringing chilly air off the land. The sun is shining bright and is most welcome.

The BigBox survey documented the switch of the system from downwelling to upwelling. The bottom layer has moved far up the shelf, with the bottom front reaching the 50-m isobath on the Cascade Head line. A classic southward upwelling jet has spun up with speeds in excess of 0.5 m/s (1 knot). At the same time the pool of local runoff rich in nutrients and iron previously held against the coast by the downwelling circulation has spread across the entire shelf. We speculate that this serves to "fertilize" the shelf in preparation for a spring bloom. We are starting to see phytoplankton levels increase after the few days of this pattern and lots of sun.

During our BigBox (lines 1-8) survey we documented the existence of a deep, anticyclonic (clockwise) eddy just offshore of Heceta Bank. It's center is at about 43.75N, 125.5W as seen in a 4-Feb SST image. Speeds in the eddy core are in excess of 0.4 m/s from 100-300 m. This eddy was apparent in satellite imagery from mid January before we sailed and appears to be a "lee" eddy from either Cape Blanco or Heceta Bank itself. We hope to sort this out from looking at satellite imagery when we return from the cruise. I believe this type of eddy has been observed offshore in the Newport Hydrographic Line sampling and the northward jet, topography interaction may explain its formation.

Unfortunately during our BigBox survey on 5 Feb, the HTI bioacoustics sled failed. When we recovered the HTI at the end of the survey the data cable was badly kinked from an encounter with fishing gear. This will be an expensive fix (many $K) since the acoustics system needs to be recalibrated once the cable is repaired/replaced.

We have just started a tow-yo CTD section along the Cascade Head line from the 70-m isobath and working offshore. This will allow us to contrast the character of the bottom layer during upwelling with that observed earlier during downwelling. On Friday we'll do our final BigBox lines 1-3 survey and on Saturday our final SmallBox North survey. We are scheduled to be dockside in Newport at 0800 on Sunday morning.

Jack Barth
Chief Scientist, R/V Wecoma
2200, 6 Feb 2003

----------------------------------------------------------------------- Zooplankton report. Jesse Lamb and Jaime Gomez-Gutierrez

The CP line (Line 6) was sampled during the evening of Monday, February 4, until around mid-day Tuesday, February 5. As noted before, the inshore sections of this transect were heavily laden with crab gear. This made it impossible to repeat the same inshore MOCNESS net tows of the previous COAST cruises, at stations CP-2 and CP-4. Therefore, our MOCNESS tows occured at stations CP-5,8(sampled twice for day/night comparison), and 11. Even though we lacked detailed sampling inshore, we still achieved sampling on the shelf (CP-5), on the shelf-break (CP-8), and off the shelf (CP-11). It should also be said that we did sample every CP station with the 1/2m vertical net (stations 1-12), giving us some inshore samples.

The copepod and euphausid species distribution of the MOCNESS tows pretty much mimiced the distribution of our sampling on line 2, with some noticed exceptions. CP-5 was comprised of mostly crab zoea (a post-naupliar stage of crab development). Apparently, there is good reason for the high density of crabing in the area. There were very few euphusid furcilia in this net, and the ones found were all the species Thysanoessa spinifera. The CP-8 night tow yielded both Thysanoessa spinifera and Euphausia pacifica species. Surprisingly, during the CP-8 day tow, we caught some Thysanoessa spinfera juveniles and adults, the abundance of which was noticed on the HTI profile during the tow. It is very rare that we catch any euphausids in numbers during the day time.

The copepod species composition for the CP-5 and 8 day/night tows was practically the same as the CH line sampling. This was comprised again of Metridia, Calanus tenuicornis, Calanus pacificus, Paracalanus, and some Scolecithricella minor. These are all warm water, off-shelf speices, consistent with downwelling. There were occurances of Calanus marshallae and Acartia longirimis as well, which are cold water, on shelf speices, consistent with upwelling. These were not found in great numbers.

CP-11 consisted with the classic off-shelf speicies composition: Euchaeta, Clausocalanus, Paracalanus, and Metridia speices. This tow was done at night, and included some numbers of the E. pacifica euphausid as well. It should be noted that E.pacifica was only found on the shelf break and off-shelf stations (CP-8 and 11).

Lastly, the abundances of animals in all of these tows was very low. This is consistent with downwelling conditions during this time of year.

Jamie and I would like to thank the folks who helped us deploy/recover, and wash nets: we really needed the help during our long stretch of sampling. We'd also like to thank the Marine Techs, especially Mark Willis, who had to re-arrange the SEASOAR block every time we went from vertical to MOCNESS sampling.