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RV Įrni Frišriksson

RV Įrni Frišriksson

Cruise objectives

About 5-6 days of the cruise will be spent on the northernmost box of MAR-ECO, sampling for the MAR-ECO project Z4: Trophic interactions of copepods, euphausiids, chaetognaths and fish across the Mid-Atlantic Ridge. The REDFISH/MAR-ECO cruise with RV Įrni Frišriksson, will be conducted in the Irminger Sea and adjacent areas from June 3 to July 4 2003.

Observations, sampling equipment and data analysis will be conducted in the MAR-ECO northernmost box: The target groups will be phytoplankton, copepods, euphausiids, chaetognaths and fish. Observations will include both intensive studies at five stations, among them one diel station, and the overall mapping of water mass characteristics, phytoplankton biomass and zooplankton abundance by towing an undulating vehicle (Nu-shuttle) between the stations of intensive studies.

A multidisciplinary team of physical oceanographers, biologists and engineers with expertise on taxonomy, biological and technical sampling methods, hydroacoustics etc. will participate in the cruise. The RV Įrni Frišriksson can accommodate a scientific crew of 15-20.

Temperature and salinity will be recorded with a CTD (Sea Bird Electronics SBE-911 plus). Samples for nutrient measurements will be collected from selected depths for later analysis ashore.

Sea water samples (1 l) for phytoplankton measurements (chlorophyll a and primary production) will be taken from depths of 0, 10, 20, 30, 50, 100, 150 and 200 m.

The zooplankton will be sampled with a Multinet sampler (0.25 m2 opening, 180 mm mesh size) that will be towed vertically from the bottom and to the surface. The Multinet will be deployed at least three times at each station thereby obtaining 13 depth stratified samples to the bottom (0-50-100-200-400-600-800-1000-1200-1400-1600-1800-2000-2200m).

Gelatinous zooplankton will be sorted out from all net samples and as far as possible, identified onboard. The samples will be analysed with respect to abundance, biomass, length and stage frequencies (copepods, euphausiids) and gut contents.

At each station life zooplankton will be collected with a WP2 net (0.25 m2 opening, 180 mm mesh size). The life samples will be used for measursing egg production and gut fluorescence.

A GLORIA-type midwater trawl with cod-end lined with fine mesh net will be used to sample pelagic fish, cephalopods and gelatinous zooplankton. The catch will be identified to species and subsamples taken for each species for length measurements. Further, stomach samples will be taken to identify food remains.

To monitor the distribution and abundance of pelagic fish and macroplankton, acoustic measurements with a Simrad EK500 echo sounder with three transducers (38, 120, 200 kHz) in a protruding keel.

Towed vehicles
In order to map the pelagic community in the surface layers (0-150 m) a towed body (Nu-Shuttle), equipped with depth, salinity, temperature sensors, a fluorometer, a light meter and an OPC (Optical Plankton Counter), will be deployed at the legs between stations.

Station work at the diel station
he vertical distribution and feeding activity (gut contents) of target groups will be monitored with nets and acoustics. The aim is to occupy the same station for 30 hours taking depth stratified samples every six hours with the Multinet and the GLORIA trawl.

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