Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Krill species raw counts and abundance per 1000 cubic meters are reported.

Three day trips were made aboard the R/V Thuwal to a location referred to as the Economic City Deep or ECDEEP: a ~700 m deep basin located north of KAUST at 22.5o N, 39.03o E).  A 1/4-m MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System; Wiebe et al., 1985) with 200 µm mesh nets was used to sample the zooplankton.

Field sampling: The MOCNESS was obliquely towed four times from the stern A-frame using 11.43 mm conducting cable to 600 m depth with a ship speed nominally of 2 kts (Fig. 2; Table 1). Two MOCNESS tows were taken during daytime, one each on 7 and 8 January 2014, and two night tows were taken on 12 January 2014. The first day tow (m-25-001) was equipped with 5 nets that sampled 600-400, 400-200, 200-100, and 100-0 m. The second day tow (m-25-002) and the two night tows (m-25-003, m-25-004) each had six nets that sampled 600-400, 400-200, 200-100, 100-50, and 50-0 m. The first tow was done without having GPS data input to the MOCNESS acquisition program, so positions from the bridge were obtained for the tow start and end, and at each opening of a net. GPS positions were logged for the other three tows. The MOCNESS system was equipped with the standard SeaBird temperature and conductivity probes. Volume of water filtered by each net was based on the net frame angle and flowmeter counts using equation 10b in Wiebe et al., 1985.

The samples from the first tow were all preserved in 95% alcohol suitable for genetic analysis. Those from the other three tows were first split in a Folsom splitter (McEwen et al., 1954) and then one half was preserved in alcohol and the other half preserved in formalin. In the KAUST Red Sea Center laboratory, the euphausiids in the alcohol fraction of each of the stratified oblique samples were sorted using a dissecting stereomicroscope, identified using the Baker et al. (1990) guide, and counted.

The column "tow" in this dataset can be joined with the tow numbers in the dataset  'MOC_CTD_RedSea' https://www.bco-dmo.org/dataset/630187.

The counts of each euphausiid species for each net were standardized to the number of individuals/1000m3 for each depth stratum using the volume filtered by each net. The cumulative percent abundance (Baker, 1970; Pennak, 1943) was calculated starting from the bottom of each tow (i.e., the bottom of the first depth stratum where a species occurred was assigned 0 percent and the top of the final depth stratum of occurrence was assigned 100%). Depth (m) values of 25%, 50%, and 75% occurrence were interpolated based on the cumulative curve.

BCO-DMO Processing:

- added conventional header with dataset name, PI name, version date
- renamed parameters to BCO-DMO standard
- replaced space with underscore
- replaced blank cells with nd
- added activity, ISO_DateTime_Local columns
- changed cast type from MOC1 to MOC.25

2016-04-22: to enable joining: krill_by_sp and krill_by_tow: Changed instrument (was called cast_type) from MOC.25 to MOC-25 and changed tow from m_25_00# to #.

2016-05-04: created a new dataset by joining 'MOCNESS tow metadata' and earlier version of 'Krill abundance by tow', then manually added hypertext links to the appropriate tow physical data from 'MOC_CTD_RedSea'.

version 3. 2022-05-26:
Hyperlinks within the data table were removed and the linked dataset was instead added structurally as a "Related Dataset" to this Krill dataset page.  The hyperlinks were the corresponding tow data rows in the main data table of  'MOC_CTD_RedSea' https://www.bco-dmo.org/dataset/630187 .
 

The krill population at station ECDEEP was characterized via MOCNESS sampling and CTD casts.