copepod_MOC
PI: Sharon Smith
dataset: Copepod species and stages with abundances from MOCNESS net tows
project/cruise: Arabian Sea/TTN039 - training & calibration cruise
ship: R/V Thomas Thompson
Copepods identified, staged, and enumerated from TT039 (1994 cruise).
Relevant Reference:
Lane, P.V.Z., S.L. Smith, J. Zaragoza, I. Prusova and M. Roman. 1998. United States Join
Global Ocean Flux Study (U.S. JGOFS) Technical Report: Zooplankton biomass in the uppe
water column of the Arabian Sea in 1994 and 1995. RSMAS Technical Report 98007, Rosenstie
School of Marine and Atmospheric Science, University of Miami Press, 409pp.
PI Notes and Methodology
Double 1m2 MOCNESS net. The double MOCNESS is configured like two 1m2 MOCNESS systems
attached side-by-side and carries twenty nets (Wiebe et al., 1985). The MOCNESS is designed
to fish with a 1m2 net mouth area when towed at a 45o angle (Wiebe et al., 1976). A flow
meter mounted on the frame, just ahead of the net mouth, allowed calculation of the volume
of water sampled (Wiebe et al., 1976; 1985). The data-acquisition software used angle
information when calculating volume of water filtered. The double MOCNESS was fitted with
153um mesh nets and included, in addition to the standard conductivity (Sea-Bird SBE4) and
temperature (Sea-Bird SBE 3) sensors, a transmissometer (SeaTech, 25cm beam) and an oxygen
probe (Sea-Bird SBE 13). The double MOCNESS was towed behind the ship at a speed of 1.5 to
2 knots (2.8-3.7 km h-1) through the water. Winch speed generally ranged from 10 to 25m
min-1 during deployment and 5 to 15m min-1 during recovery. Target sampling depths for this
report were 300-250m, 250-200m, 200-150m, 150-100m, 100-75m, 75-50m, 50-25m and 25m to
surface.
The MOCNESS was deployed primarily at 48-hour time-series stations (six per cruise), at
locations determined prior to the cruises where regions of coastal upwelling, open ocean
upwelling, strong suboxic conditions, or in the case of the most southerly station (S15)
oligotrophic conditions were expected. Tows were done at approximately mid-day and
mid-night, one each, at the 48-hour stations. Tow times were selected to avoid sampling
during crepuscular periods when diel vertical migration would complicate observations of
vertical distributions.
The 1m2 MOCNESS samples collected during night were split using a flat-bottomed splitter.
One-half of each night sample was preserved in 4% buffered formaldehyde/seawater solution
for laboratory measurement of displacement volume (Smith et al., 1998; Lane and Smith,
1997) and taxonomic analysis. With the exception of the 25-50m sample, daytime collections
were not split and were all preserved in 4% buffered formaldehyde/seawater solution. The
25-50m sample was split and treated similarly to the night collections.
Laboratory analysis. The samples reported here were split one to four times, depending on
the amount of plankton present, in a Folsom splitter at the Rosenstiel School of Marine
and Atmospheric Science (RSMAS), University of Miami. Subsamples were concentrated to 20
to 100ml and were transported to Ukraine (Russia) for enumeration and identification at the
Institute for Biology of the Southern Seas (IBSS) in Sevastopol. Treatment of the samples
at IBSS depended on the amount of plankton present in each sample. When the sample
contained only a small amount of plankton, the entire split was analyzed for all species.
In most cases, however, organisms smaller than ~1.5mm were identified and counted in
smaller subsamples collected with a 1, 2 or 5ml Stempel pipette. Two replicate subsamples
were withdrawn and counted and the data were averaged for calculation of abundance;
generally 1-40 individuals per taxon were identified and sometimes more when a taxon was
particularly abundant. Organisms ranging in size from ~1-2mm were counted in another part
of the subsample collected with a 5ml Stempel pipette or by splitting the subsample into
two or four equal parts. The entire subsample originating at RSMAS was then analyzed for
abundance of organisms larger than 2mm, including copepods, euphausiids, amphipods, fish
larvae, ostracods and any rare, large organisms. A total of 300 to 500 organisms per entire
split were identified and counted. The identifications were performed with the aid of
Leningrad Optic-Mechanics Company (LOMO) binocular microscopes using various magnifications
depending on the sizes of the individuals being identified. Copepod species are listed in
alphabetical order. All copepod adult stages, copepodite stages and nauplii found in each
sample are listed. The taxonomic notations are: c1 = copepodite stage I of the species;
c2 = copepodite stage II of the species; c3 = copepodite stage III of the species;
c4 = copepodite stage IV of the species; c5 = copepodite stage V of the species;
c = undetermined copepodite stage of the species; m = adult males of the species;
f = adult females of the species. Total length is the average length in mm measured
microscopically for that taxon.
Parameters Descriptions Units
cruise_id cruise identification TT=RV/Thomas G.
Thompson
tow MOCNESS tow number
sta_std Arabian Sea standard station identifier
sta station number, from event log
event event number, from event log, can be
translated into date as follows
MMDDHHmm (year 94)
date date of sampling YYYYMMDD
net MOCNESS net number
time time, UTC hours/minutes (HHMM)
lat latitude of net tow (minus = south) decimal degrees
lon longitude of net tow (minus = west) decimal degrees
depth_start depth at start of tow meters
depth_end depth at end of tow meters
species taxonomic genus and species
stage developmental stage: f=female; m=male;
c1-c5=copepodite stages; n=naupliar stages
abundance abundance of copepod stage number copepods/meter^3
nd indicates no data