copepod_bongo
PI: Sharon Smith
dataset: Copepod species and stages with abundances from Bongo tows
project/cruise: Thomas Thompson cruise TTN054, Process Cruise 7, 1995
ship: R/V Thomas Thompson
Copepods identified, staged, and enumerated from TTN054, November/December 1995.
Relevant References:
Lane, P.V.Z., S.L. Smith, J. Zaragoza, I. Prusova and M. Roman. 1998. United States Joint
Global Ocean Flux Study (U.S. JGOFS) Technical Report: Zooplankton biomass in the upper
water column of the Arabian Sea in 1994 and 1995. RSMAS Technical Report 98007, Rosenstiel
School of Marine and Atmospheric Science, University of Miami Press, 409pp.
Bongo net. Bongo net collections covering the upper 200 meters were made at all intermediate
stations and at some hydrographic stations, but not at the 48-hour time-series stations.
Bongo net frames were 60cm diameter and were fitted with 153 and 335um mesh nets. Only the
153um mesh samples were analyzed. General Oceanics model 2030R flow meters were placed in
the net mouth openings for the determination of volume filtered. The nets were towed
obliquely from the side of the ship at approximately 1.5 to 2 knots (2.8-3.7 km h-1)
through the water. Winch speed was generally 30m min-1 during deployment and 20m min-1
during recovery. The net was allowed to settle for about 30 seconds while at maximum wire
out. The target depth for all Bongo tows was 200m, unless the sonic depth was less than
that, and the wire out was adjusted during each tow, depending on the wire angle, to attain
that depth. The maximum sampling depth of each tow was determined from a Wildlife Computers
Mk3e Time Depth Recorder (TDR) attached to the net frame. Elapsed sampling time versus
depth was plotted from TDR data for representative tows from cruises TTN050 (August 18, 1995
- September 15, 1995) and TTN054 (November 30, 1995 - December 29, 1995). These comparisons
showed that retrieval of the net was reasonably steady in both monsoon seasons so that all
depth intervals were sampled uniformly. In the worst weather (TTN050; SW Monsoon), the rate
of vertical ascent of the net was 11m min-1 (+/- 3; n=4), while in the better weather
(TTN054; NE Monsoon) ascent rate was 14m min-1 (+/-2; N=4).
The samples from the 153um Bongo net were split in a modified Folsom splitter, which split
the sample into four parts consisting of 50%, 20%, 20% and 10%. In general, 10% was used
for dry weight measurements (Lane and Smith, 1997;), 20% was preserved for collaborating
scientists, and 70% was preserved for displacement volume measurements and taxonomic
analysis.
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 of the copepods is the average length
in mm measured microscopically for that taxon.
Parameters Descriptions Units
cruise_id cruise identification TT=RV/Thomas G.
Thompson
sta station number, from event log
sta_std Arabian Sea standard station identifier
event event number, from event log, can be
translated into date as follows
MMDDHHmm (year 95)
year year YYYY
mon month 1 to 12
day day of month 1 to 31
time time, UTC hours/minutes (HHMM)
yrday_gmt Jan. 1 = yrday 0. GMT day and decimal
time, as 325.5 for the 326th day of
the year, or November 22 at 1200 hours
(noon).
ISODateTime_UTC date/time (UTC) ISO formatted
tow bongo tow number
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