IKMT samples and underwater video recordings collected in the Drake Passage from R/V Laurence M. Gould (LMG1504, LMG1509, LMG1410) from 2014-2015

Website: https://www.bco-dmo.org/dataset/705556
Data Type: Cruise Results
Version: 1
Version Date: 2017-06-19

» Pilot Study: Addition of Biological Sampling to Drake Passage Transits of the "L.M. Gould" (DrakeBioGould)
Loeb, Valerie JeanMoss Landing Marine Laboratories (MLML)Principal Investigator, Contact
Santora, Jarrod AUniversity of California-Santa Cruz (UC Santa Cruz)Co-Principal Investigator
Ake, HannahWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

IKMT samples and underwater video recordings collected in the Drake Passage from R/V Laurence M. Gould (LMG1504, LMG1509, LMG1410) from 2014-2015


Spatial Extent: N:-54.0093 E:-54.7694 S:-65.1842 W:-67.162
Temporal Extent: 2014-10-29 - 2015-11-11

Dataset Description

IKMT samples and underwater video recordings collected during Drake Passage transits from LMG14-10, LMG15-04 and LMG15-09.

Acquisition Description

Net Sampling:

Open oblique net tows were made with a 1.8 m Isaacs-Kidd Midwater Trawl (IKMT), fitted with 505 um mesh and a protected cod end, fished from 0 to ~155m at ship speeds of ~2 kts.

During LMG14-10 and LMG15-04 an underwater video camera system was suspended from the IKMT spreader bar allowing video recordings of material being fished by the net at some stations (indicated in data log). 

Processing Description

Wet Weight Displacement Volume:  Wet weight displacement volume measurements (minus gelatinous organisms, including salps) were made for all freshly collected samples.  Additional wet weight displacement volume estimates were made for large and small sized zooplankton fractions, the separation of which is largely dependent on the ability to identify and adequately enumerate taxa.  Maximum lengths of the small fraction generally were ≤ 10 mm (e.g., copepods, shelled pteropods, ostracods, larval euphausiids and other crustaceans).  Due to their large length range chaetognaths were represented in both categories but are treated as part of the small fraction.  Large taxa (e.g., ~10-20 mm) include postlarval euphausiids, amphipods and polychaetes. Wet weight displacement volumes determined separately for “extra large” (e.g., >20 mm) postlarval myctophids and Antarctic krill (Euphausia superba) are included with the large taxa.  

Taxonomic Identification and Enumeration:  The taxonomic identification (to species level if possible, abundance estimates (numbers m-2 and numbers 1000 m-3) and length measurements of known sound scattering organisms were made for as many samples as possible while onboard.  This was generally possible for samples collected during southbound transits and opportunistically in the Antarctic Coastal Zone.  In order to provide data from the Antarctic Zone comparable to those from long-term data bases off the Antarctic Peninsula (e.g., Loeb et al., 2008, 2010; Loeb and Santora, 2013) all postlarval Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) were removed and enumerated from samples <2 L; for larger catches, abundance estimates were based on 1 to 2 L subsamples.  All postlarval krill in samples with <100 individuals were measured, sexed and staged according to Makarov & Denys (1981); in larger samples at least 100 krill were analyzed.  The 2 salp life stages were enumerated and internal body lengths of each (Foxton, 1966) were measured to the nearest mm. 

Because of time limitations during northbound transits, generally only the large size fractions could be processed onboard; as a consequence representative 4% buffered formalin preserved aliquots of the small size fraction were analyzed at Moss Landing Marine Labs (MLML) following each cruise.  Finer resolution identifications of abundant large taxa (e.g., similar euphausiid and pteropod species) in formalin-preserved samples were also made at MLML following completion of field efforts.  Due to a combination of funding, time and/or expertise constraints, species identifications of various abundant small zooplankton categories (e.g., euphausiid larvae and copepods) were limited.

BCO-DMO Data Processing Notes:

-reformatted column names to comply with BCO-DMO standards
-compiled each deployment into one table

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stationStation where samples were taken unitless
dateDate samples were taken; YYYY/MM/DD unitless
start_GMTStart time of net tow; HH:MM unitless
end_GMTEnd time of net tow; HH:MM unitless
lat_degLatitude; degrees (S) degrees minutes
lat_minLatitude; minutes degrees minutes
latLatitude in decimal degrees decimal degrees
lon_degLongitude; degrees (W) degrees minutes
lon_minLongitude; minutes degrees minutes
lonLongitude in decimal degrees decimal degrees
biogeographic_zoneCode for the biogeographic zone in which sampling took place: SAZ=Subantarctic Zone; PFZ=Polar Frontal Zone; AZ=Antarctic Zone; ACZ=Antarctic Coastal (Continental) Zone unitless
DIELIndicates day night or twiglight sample collection on net deployment 1 hour before and after local sunrise and sunset. unitless
volume_filteredVolume of water filtered through the net meters cubed
SSTSea surface temperature celsius
bottom_depthBottom depth at sampling location meters
wind_speedWind speed at time of sampling knots
wind_directionWind direction at time of sampling degrees
tow_depthThe depth at which the net tow took plac meters
underwater_videoIndicates whether videorecordings were made at each station and if so to what depths. unitless
notesNotes and observations unitless
ISO_DateTime_UTCDate/Time (UTC) ISO formatted unitless

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Dataset-specific Instrument Name
GoPro Hero3+ Black Edition
Generic Instrument Name
Dataset-specific Description
Used for underwater video recording
Generic Instrument Description
All types of photographic equipment including stills, video, film and digital systems.

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ARSV Laurence M. Gould
Start Date
End Date
RV L.M. Gould Drake Passage transects


ARSV Laurence M. Gould
Start Date
End Date
RV L.M. Gould Drake Passage transects


ARSV Laurence M. Gould
Start Date
End Date
RV L.M. Gould Drake Passage transects

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Project Information

Pilot Study: Addition of Biological Sampling to Drake Passage Transits of the "L.M. Gould" (DrakeBioGould)

Coverage: Drake Passage, South Shetland Islands

PI supplied abstract:

A 50+ year warming trend in the Southern Ocean has been most dramatic in Drake Passage and likely impacts ecosystem structure here. Acoustic Doppler Current Profiler (ADCP) records from multiple NSF “L.M. Gould” supply transits of Drake Passage from 1999 to present demonstrate spatial and temporal variability in acoustics backscattering. Acoustics backscattering strength in the upper water column corresponds to zooplankton and nekton biomass that supports predator populations. However, for much of Drake Passage the identity of taxa contributing to this acoustically detected biomass is not known. This project would introduce a biological component to “L.M. Gould” transits of Drake Passage with the goal of determining the identity of taxa responsible for the backscattering records obtained by ADCP and relating these to higher trophic levels (seabird/marine mammal). Net sampling during spring and fall transits will permit assessment of diel and seasonal changes in the abundance and taxonomic composition of zooplankton and top predators represented between Patagonia and the Antarctic Peninsula. Net samples and depth-referenced video records taken in conjunction with ADCP profiles will permit the identification of the dominant acoustic backscatters in the 3 biogeographic regions represented here, the Subantarctic, Polar Frontal, and Antarctic Zones. The validity of dominant backscattering taxa in the Antarctic Zone will be tested by comparing the ADCP records with abundant zooplankton data collected off the Antarctic Peninsula during January-March 1999-2009 as well with long-term top predator surveys. The broader impacts also included cruise blogs to Moss Landing Marine Laboratories and Monterey Academy of Oceanographic Science (Monterey High School, Monterey CA) plus involvement with MAOS  faculty and students providing first-hand data and insight into marine research in a near real-time format.  The faculty used this opportunity to engage students in “real” science while focusing on implementing instruction using the Next Generation Science Standards.

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Funding SourceAward
NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP)

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