To investigate physical, chemical and biological processes on the eastern Bering Sea continental slope and shelf. Objectives are

1.Measure the currents (via ADCP) and water properties (via CTD) on a few transects across the Bering Slope Current and continental shelf and deduce the geostrophic circulation. (EDC)

2.Assess nutrient inputs and utilization by physical and biological processes in middle shelf, shelf break, and offshore SEBSCC study areas. An emphasis will be placed on nutrient samples (nitrate, nitrite, ammonium, phosphate and silicate) from hydrographic and productivity casts in transects and time series measurements at mooring sites. Additional nutrient samples will also be analyzed for experimental samples collected by other investigators. (TW)

3.Measure rates of total, "new" and regenerated phytoplankton production using 13-C and 15-N tracer techniques and "diagram analysis" of nitrate depletion to determine the proportion of total surface water column production that is "new" and available for export from the euphotic zone via settling to deeper waters and/or incorporation by growth into primary, secondary and tertiary consumers. (JG)

4.Measure nutrient, chlorophyll, and zooplankton concentrations for use as biophysical indices of the status and health of the southeastern Bering Sea ecosystem. The variables will be measured at the SEBSCC monitoring sites: shelf break, Outer Shelf Domain, Southeast Middle Shelf Domain, Northwest Middle Shelf Domain and Pribilof Islands. (JN)

5.Measure the composition of lipid and carbon and nitrogen stable isotopes in zooplankton, suspended particulate matter and surface sediment samples to indicate the source of sinking organic matter (being collected via automated sediment traps deployed earlier). This will provide information about the pelagic food web. (SH)

ITINERARY:(Include station positions and route waypoints. ATTACH PAGE SIZE CRUISE TRACK for submission with final cruise reports.)

06 May 1998 - Depart Dutch Harbor, AK
22 May 1998 - Arrive Dutch Harbor, AK

Table 1 shows a detailed itinerary. Figure 1 shows the proposed station locations.

Will radioactive methods be used? If so, list radiation use authorization number.

No radioactive materials will be used.

Hazardous materials will be necessary for the automated nutrient analyzer and possibly for phytoplankton samples. MSDS will be provided.

SAMPLING PLAN:

EDC:The ADCP, P-code GPS receiver, ship's gyrocompass and Ashtech 3DF will operate during the entire cruise. Data will be recorded via RDI's DAS and user exit UE4 and stored on compatible storage media. We will supply appropriate DAS configuration files.

CTD casts will be conducted to the shallower of 1500 m or 10 m above the bottom using the Sea-Bird 911 plus equipped with rosette, 10-L Niskin bottles, fluorometer, PAR sensor and transmissometer. A PMEL Zip drive will be added to the ship's CTD acquisition computer. CTD data will be moved to a PMEL PC for Sea-Bird SeaSoft processing then onto a PMEL Unix workstation for further processing, conversion to EPIC netcdf files and section plotting via a networked PMEL PostScript printer.

TW:Nutrient samples will be collected from all CTD/rosette water sample casts unless otherwise specified. Depending on the total water depth, 6-12 water samples will be needed to give good vertical resolution in the upper water column (0-30 m), pycnocline (25-40 m) and sub-pycnocline (50-1000 m) in order to assess physical renewal processes and biological uptake and regeneration. Plant pigment (Chlorophyll and HPLC) samples can be obtained from the same sampling depths as nutrients plus at the chlorophyll maximum as determined by the profiling fluorometer. Running seawater is required in the ship's laboratory for calibrations and near-surface chlorophyll fluorescence.

JG:At 2 productivity stations each day - one in early morning and one near noon - the depths at 7 light levels in the euphotic zone will be determined from the profiling PAR sensor or a secchi disk. Samples obtained from 5-L or 10-L Niskin bottles in each zone will be placed in clean polycarbonate bottles and spiked with 13-C and 15-N. Triplicate samples at each depth will be used so that we can determine total, "new" and regenerated production by measuring uptake of labeled carbon dioxide, nitrate, ammonium and urea. Samples will be incubated in a deck incubator and cooled with flowing seawater, with in situ light levels simulated using neutral density perforated wire screens. Incubations will last about 4 hours, after which samples will be filtered on glass fiber filters, rinsed with filtered sea water, and frozen at -20 C for storage and transport back to the University of Alaska mass spectrometer laboratory.

JN: Table 2 shows the sampling depths. At all monitoring stations a CTD/rosette cast is used to collect nutrients and chlorophyll samples. At mooring 2 (M2) the regular chloropyll water column samples will be taken plus triplicate samples at the depths of the bio-optical sensors (A-3, AC-9 and WetStar, Table 2). The CTD cast is followed by a net tow using two bongo frames (20-cm frame with 150 micron mesh nets and a 60-cm frame with 333 micron mesh nets) suspended from the same wire and separated by approx. 1 m. A SeaCat is attached above the 20 cm frame and a lead weight lies below the 60 cm frame. Flow meters are placed in the mouths of each net frame. The tow cable must be at 45 degrees during both deployment and recovery. Maximum depth for the Bongo tows is 5 m off bottom. One side of both frames are to be immediately preserved in formalin for quantitative analysis. The second side is available for other projects (Henrichs, UAF). At the shelf moorings (2, 3, & 4), three replicate vertical tows will be taken with a CalVET net (0 - 60 m). Whenever there is a question regarding the sampling protocol, the FOCI Field Manual should be consulted.

SH:At each of the X's around sites M2, M3 and M4 (15 stations total):