Wecoma report 1 June

Scientists aboard Wecoma conducted station sampling along the Cape Perpetua line (line 6) during 1 June. Winds during this period were 10-20 knots starting out to the SE, turning to the NW and finishing again to the SE. We made CTD casts from CP-12 to CP-1 collecting samples for iron profiles at CP-1,2,4,5,8,11 and for nutrient profiles at CP-2,4,8,11. MOCNESS tows were made at CP-2,4,5,8,11 (see the report by Bill Peterson below). TAPS (high-frequency bio-acoustics instrument) profiles were made immediately after each MOCNESS tow and while the HTI bio-acoustics package was running which should provide a nice data set for Malinda Sutor to analyze with respect to zooplankton. We confirmed the presence of all three southern line moorings, but did not see any of the guard buoys at the shelfbreak or mid-shelf moorings. It was night when we were near the inner shelf mooring so we could not look for the guard buoys there.

Bill Peterson's zooplankton report: "1-2 June 2001. The zooplankton were sampled with the MOCNESS along Line 6 (Cape Perpetua) at stations CP-11, CP-8, CP-5, CP-4 and CP-2. Water depths ranged from 700 m (CP-11, just off the shelf) to 50 m of water (CP-2, nearshore). All other stations were on the shelf. The deep water station contained large numbers of Neocalanus cristatus, a copepod that is typical of the deep-waters of the Gulf of Alaska. It was found chiefly between depths of 120-350m. The zooplankton in the upper layers at this station were chiefly small copepods, doliolids and euphasusiid eggs. An acoustics scattering layer was present between 75-120 m and MOCNESS sampling showed this layer to be composed of large Dungeness crab larvae. The first shelf station, CP-8 was near the shelf break. We had seen moderate sound scattering very near the bottom and made a point to sample the targets (believed to euphausiids). MOCNESS sampling confirmed large numbers of juvenile euphausiids, on the order of 50 per cubic meter, located in a layer from very near the bottom up to 20 m off the bottom The remainder of the water column was populated by copepods. Station CP-5 had very few euphausiids; small copepods were the main components of the zooplankton. This is an agreement with the acoustics which showed virtually no backscattering on the 120 and 200 kHz with most backscattering concentrated in the 420 kHz band. The inner shelf stations were situated in the region of slower alongshore flows. The plankton was dominated by phytoplankton and small copepods. Phytoplankton was present in extraordinarily high concentrations making the MOCNESS nets difficult to clean and samples difficult to process."

We are presently conducting half of a Bigbox SeaSoar/HTI/Fe survey, sampling lines 5,4,3,2,1 while Thompson completes profiling along lines 5, 4 and 3.