Zooplankton abundance from Isaacs-Kidd Midwater Trawl (IKMT) hauls from RVIB Nathaniel B. Palmer NBP1801 in the Ross Sea, Jan.-Feb. 2018 (NCEI Accession 0277872)

Acquisition Description:
Sample collection : Net tows and mid-water trawls were conducted in the western Ross Sea, Antarctica on board the R/V Nathaniel B. Palmer in January-February 2018 (cruise number 18-01). Both the ring net (1 m diameter, 333 um mesh, non-filtering cod end) and the Issacs-Kidd Midwater Trawl (IKMT, 1.8 m frame, 500 um mesh, non-filtering cod end) were fitted with a calibrated General Oceanics flow meter. Contents of each tow were concentrated and preserved with buffered formaldehyde (4% final concentration) in 500 ml wide-mouth glass jars. Samples were sent back to the home laboratory (Rutgers University) for analysis.

Analyses : Contents of each tow (or a subsample if the density of zooplankton or fish was high) were sorted by taxa and, in some cases, developmental stage. Measurements for abundance were conducted using a dissecting microscope (Zeiss Discovery.V8).

Volume of water (cubic meter) that passed through the net/trawl during each tow was calculated using flowmeter rotor constant, flowmeter start and end values, and the area of net opening.

Abundance per cubic meter per tow/trawl was then calculated for each species and, in some cases, developmental stage, by dividing the number of individuals for each species/developmental stage by the volume of water.