This cruise was
sponsored by the National Oceanographic and Atmospheric Administration and the
National Science Foundation. This
report was prepared by all members of the Scientific Party on this cruise (see
Appendix A).
TABLE OF CONTENTS
Purpose of the
Cruise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . 3
Sampling
Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 3
Cruise Narrative
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . 7
Individual
Reports Hydrography . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Phytoplankton Chlorophyll, Nutrients
and Light Attenuation Studies . . . . . .
9 Zooplankton Results . . . . . . . .
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . 10 Ichthyoplankton Results. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 MOC-10 Ichthyoplankton Results . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Copepod Life History Studies . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Summary of
Operations and Samples Collected . . . . . . . . . . . . . . . . . . . . . . .
. . . . . 20
References . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 21
Appendix A. Personnel List . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Appendix B. Event Log . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Appendix C. Hydrographic Data . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . 35
PURPOSE OF THE CRUISE
The cruise
aboard ALBATROSS IV (ALB-9705) was the fifth in a series of six Broad Scale
surveys conducted monthly from January to June during 1997 to monitor the
changing biological and physical status in the Georges Bank ecosystem. These six cruises are the third year of
broad scale surveys conducted as part of the U.S. Globec Georges Bank
Program. The personnel who participated
in this cruise are listed in Appendix A.
The principle
objectives of the cruise were to:
(1) determine the distribution and
abundance of the ichthyoplankton and zooplankton community on the Bank and in
adjacent Gulf of Maine and slope waters.
Emphasis is on target fish (eggs, larval and juvenile cod and haddock)
and copepod species (all stages of Calanus finmarchicus and
Pseudocalanus sp.) and their
predators and prey.
(2) provide systematic collections of larval
and juvenile cod and haddock for age and growth estimates and feeding habits. (3) conduct a hydrographic survey of the
Bank . (4) conduct a survey of chlorophyll and
nutrient levels on the Bank
(5) map the Bank-wide velocity field using
an Acoustic Doppler Current Profiler.
(6) collect live animals for herring feeding
experiments at the University of Rhode Island.
(7) to recover a GLOBEC broad scale mooring
that had broken free.
SAMPLING OPERATIONS
The plan for the
GLOBEC Broad Scale surveys is to accomplish the objectives above by sampling at
a grid of 40 "standard station" locations which covers the entire
bank (Figure 1a). The Broad Scale
sampling protocol separates these 40 stations into two groups, full stations
and partial stations. At the 20 full
stations, a complete set of sampling operations is conducted. This involved a double-oblique bongo net
tow, a CTD cast with rossette collection of water samples, a 1-m2
MOCNESS (Multiple Opening
Closing Net Environmental Sampling System ,
MOC-1) tow, a plankton pump cast and a 10-m2 MOCNESS (MOC-10)
tow. At the partial stations only the
bongo tow, CTD cast and MOC-1 tow are done.
Additional bongo net tows were made between the standard stations to
increase the sampling density for cod and haddock larvae. Current measurements
also were collected continuously by a hull mounted 300 kHz Acoustic Doppler
Current Profiler (ADCP).
Bongo tows were
made with a 0.61-m frame fitted with paired 335 mm mesh nets. A 45 kg ball was attached beneath the bongo
frame to depress the sampler. Digital
flow meters were suspended in the mouth of each net to determine the volume of
water filtered. Tows were made according to standard MARMAP procedures, (i.e.,
oblique from surface to within five meters of bottom or to a maximum depth of
200 m while maintaining a constant wire angle throughout the tow). Wire payout
and retrieval rates were 50 m/min and 20 m/min respectively. These rates were reduced in shallow water
(<60 m) to obtain a minimum of a five minute tow or reduced due to adverse
weather and sea conditions. A Seabird
CTD was attached to the towing wire above the frame to monitor sampling depth
in real time mode and to measure and record temperature and salinity. Once back
on board, the 335 mm mesh nets were rinsed with seawater into a 335 mm mesh
sieve. The contents of one sieve were
preserved in 5% formalin and kept for ichthyoplankton species composition,
abundance and distribution. The other
sample was preserved in 95% ethanol and kept for age and growth analysis of
larval fish. The same preservation
procedure was followed as for the 1-m2 MOCNESS.
At stations
where the 1-m2 MOCNESS system either was not towed or could not be
used due to adverse weather conditions, a second bongo tow was made. This frame was fitted with both 335 mm
mesh and 200 mm mesh nets. Digital flow
meters were suspended in the mouth of each net to determine the volume of water
filtered. Tows were made according to
standard MARMAP procedures except maximum tow depth was 500 m. Wire payout and
retrieval rates were 50 m/min and 20 m/min respectively. The nets were each rinsed with seawater into
a corresponding mesh sieve. The 200 mm
mesh sample was retained for zooplankton species composition, abundance and
distribution, and preserved in 10% formalin.
The other sample (335 mm mesh) was kept for molecular population genetic
analysis of the copepod, Calanus
finmarchicus, and preserved in 95% ethanol. After 24 h of initial preservation, the alcohol was changed.
The 1-m2
MOCNESS sampler was loaded with ten nets. Nets 1-4 were fitted with 150 mm mesh
for the collection of older and larger copepodite and adult stages of the
zooplankton. Nets 0, and 5-9 were fitted with 335 mm mesh for zooplankton (nets
0 and 5) and ichthyoplankton (nets 6-9) collection. Tows were double oblique from the surface to within 5 m from the
bottom. The maximum tow depth for nets
0, 1 and 5 was 500 m, and for net 6 was 200 m( if net 5 was sampled deeper than
200 m, it was returned up to 200 m and closed). Winch rates for nets 0-5 were 15 m/min and for nets 6-9, 10
m/min. The depth strata sampled were 0-15 m, 15-40 m, 40-100 m, and >100 m.
The first (#0) and sixth (#5) nets were integrated hauls. For shallow stations,
with only 2 or 3 of the depth strata, not all nets were fished. The contents of
nets 0-4 were sieved through 150 mm mesh sieve, subsampled using a 2-L plankton
sample splitter if the final biomass volume was too large for one quart jar,
and then preserved in 10% formalin.
Samples from nets 5-9 were sieved through 330 mm mesh sieve and
preserved in 95% ethanol. After 24 h of initial preservation, the alcohol was
changed. The used ethanol was retained
for disposal or recycling ashore. At
priority 1 and 2 stations and at station 40, 90-ml subsamples from the bottom
and surface 150 mm mesh nets were removed and preserved in 10% formalin for Dr.
C. Miller (OSU). At priority 1 and 2
stations, 90-ml subsamples from nets 2, 3, and 4 were removed and preserved in
95% ethanol. These samples were
collected for Dr. A. Bucklin for population genetic studies to distinguish the Pseudocalanus species found on Georges
Bank. At stations deeper than 150 m where C. Miller
required subsamples for live analysis, the
1-m2 MOCNESS was hauled out after the first oblique. Samples from nets 0-4 were collected and the
MOCNESS was then immediately redeployed to complete the tow.
The 10-m2
MOCNESS was loaded with five 3.0 mm mesh nets.
Tows were oblique from surface to ~10 m from bottom or a maximum depth
of 500 m. The same depth strata were
sampled as with the 1-m2 MOCNESS.
The winch rate for retrieval varied between 5 and 20 m/min depending on
the depth stratum. The slow winch rates
were used in order to filter at least 4,000-5,000 m3 of water per
depth stratum sampled. A stepped
oblique tow profile during retrieval was used to achieve this, if needed. Catches were sieved through a 335 mm mesh,
and preserved in 10% formalin.
The Pacer
high-volume pump was used to collect nauplii and younger, smaller copepodite
stages of zooplankton. The intake hose was deployed off the port side by
connecting the suction end, fitted with a 1.7-L Niskin bottle cut in half
lengthwise, to the boom wire. The boom winch meter block was zeroed at the
surface and the wire out reading was used to determine the depth of the
cast. Two 45 kg weights were used to
depress the array. Three 30-m sections
of 7 cm diameter hose were connected to the pump, allowing the intake hose to
attain a maximum depth of approximately 75 m.
At shallow stations, the intake hose nozzle was lowered to 3-5 meters
off the bottom. Three integrated depth
samples were collected with 35 mm mesh nets, sieved through a 30 mm mesh sieve
and preserved in 10% formalin. Sampling
depths were from the maximum depth to 36 m, 36-11 m, and from 11 m to
surface. Before samples were collected,
water was diverted from the net and the hose was allowed to flush for 60
seconds. This assured that the
zooplankton from the desired strata was obtained. Once at the surface, the intake section was held just below the
surface for 60 s. This allowed the
water to pass completely through the hose.
Wire retrieval rate was approximately 4 m/min. This rate was used to obtain volumes of 500 L per 5 m depth
interval sampled.
To collect live
animals for the herring feeding experiments at URI paired bongo nets, using the
335 mm mesh size fitted with a cod end, were hauled vertically through the
water column. This haul was made at Station 38 after all other standard station
operations were completed. The net was attached to the winch wire together with
a 45 kg ball beneath the bongo frame to depress the sampler. The array was lowered to a maximum depth of
40 meters and retrieved at approximately 5 m/min for a total haul time of 10
minutes. The animals were gently poured
into two 50 gallon trash cans lined with plastic liners and filled with
seawater.
The primary
hydrographic data were collected using a Neil Brown Mark V CTD instrument
(MK5), which provides measurements of pressure, temperature, conductivity,
fluorescence and light transmission.
The MK5 records at a rate of 16 observations per second, and is equipped
with a rosette for collecting water samples at selected depths. In addition a Seabird Electronics Seacat
model 19 profiling instrument (SBE19 Profiler) was used on each bongo tow to
provide depth information during the tow.
Pressure, temperature, and salinity observations are recorded twice per
second by the Profiler.
The MK5 was
deployed with 10 bottles on the rosette and samples were collected for various
investigators. On each MK5 cast,
samples were to be collected for chlorophyll/nutrient analysis (see Individual
Report section below), for oxygen isotope analysis by R. Houghton (LDGO) and a
sample was taken at the bottom for calibrating the instrument's conductivity
data. At selected “full” standard
stations water samples were collected for micro-zooplankton analysis for S.
Gallager (WHOI). Surface samples for
phytoplankton species composition were collected for J. O'Reilly (NMFS) at the
"full" standard stations.
Equipment notes:
All systems
functioned well during the cruise with only minor occasional problems. The MOCNESS system initially repeatedly
reported a non-fatal error during data acquisition. This was traced to the problems with the navigation data coming
from the ship’s computer system. The
logging of navigation data by the MOCNESS program was deactivated and the error
did not re-occur.
On consecutive
station 11 (the bongo tow between standard stations 6 and 7) the electrical
termination on the boom wire needed to be redone. One of the wires had broken.
The wire was soldered and re-wrapped to be water proof.
On standard
station 16 the flow meter on the MOC-10 failed. The gearing had become stuck and the shaft did not turn. The meter from the MOC-1 was then used on
both the MOC-1 and MOC-10. The stuck
flow meter was adjusted and reinstalled for standard station 17. It again became stuck on standard station
20. A successful repair to the meter
was made by Chief Engineer John Hurder and the meter functioned properly from
standard station 27 to the end of the cruise.
On standard
station 20 a hydraulic line to the CTD winch leaked and hydraulic fluid spilled
into the water while the CTD instrument was in the water. The instrument was retrieved through the
slick of fluid, possibly contaminating the water bottles on the rosette. The CTD instrument and frame were washed
with detergent and rinsed. The sampling
bottles were repeatedly washed and soaked in detergent and rinsed. Four bottles were replaced with spares, and
these new bottles were used at the primary sampling depths. On two stations paired samples were taken in
both a clean spare bottle and a washed bottle to allow confirmation that no
residual effect remained.
On standard station 34 the termination on the
boom failed during the deployment of the MOC-1 system. The termination fitting slipped off the wire
and the MOC-1 frame was lost. The
termination being used was a mechanical termination, not the poured termination
that had characteristically been used with the MOCNESS system. [a post-cruise note: the MOC-1 was recovered on the next cruise
of ALBATROSS IV through a recover effort which used a flat net with a chain
sweep to trawl the area. After ten
hours of trawling the MOC-1 was recovered in quite good condition.]
CRUISE NARRATIVE
The cruise departed
Woods Hole at 2020 on Monday, May 19.
The watch schedule was set for the 0600-1400, 1400-1800, 1800-2200,
2200-0600 (‘8,4,4,8’). This was a break
from the traditional ‘6 and 6’ schedule used on ALBATROSS IV. The vessel arrived at the first station at
0600 on May 20. No significant problems
were encountered and the routine of sampling operations was quickly
established. Many in the scientific
party had been on 10 or more of the Broad Scale survey cruises, and efficient
team work occurred without direction.
The weather throughout the cruise was quite good, with winds rarely
above 20 kts. No time was lost due to
weather.
After standard
station 7 recent positions were received by e-mail for the GLOBEC broad scale
mooring which had broken free. The
mooring had drifted from near standard station 16 southwestward to be
approaching standard station 8. J.
Irish was contacted by satellite phone to provide the most recent positions in
order to plan a recovery. Within an
hour positions were received that were only a few hours old and indicated that
the mooring was less than 30 km from standard station 8. After completing standard station 8 sampling
operations were suspended and a search for the mooring begun. As the vessel steamed toward the expected
mooring location - determined by dead reckoning - the flashing light on the
mooring was observed at a distance of about 3 km. The mooring was recovered with no problems. The mooring consisted of the top float, an
ADCP unit, a bio-optical package and one pair of temperature/conductivity
sensors. The mooring line had parted
about two meters below the bio-optical package, which was about 10 m below the
surface float. Sampling operations were
then resumed at the bongo station between standard stations 8 and 9
(consecutive station 16).
A list of the
sampling operations and other events on the cruise is presented in Appendix B.
INDIVIDUAL REPORTS
Station numbers
referred to in the following reports are standard station numbers (figure 1a),
unless otherwise noted.
Hydrography
(Maureen Taylor
and David Mountain) The SBE19
Profiler and the MK5 data were post-processed at sea. The Profiler data were processed using the Seabird manufactured
software: DATCNV, ALIGNCTD, BINAVG, DERIVE, ASCIIOUT to produce 1 decibar
averaged ASCII files. The raw MK5 data
files were processed using the manufacturer's software CTDPOST in order to
identify bad data scans by "first differencing." The latter program flags any data where the
difference between sequential scans of each variable exceed some preset
limit. The "Smart Editor"
within CTDPOST was then used to interpolate over the flagged values. The cleaned raw data were converted into
pressure averaged,
pressure centered 1 decibar files using algorithms provided by R. Millard of
WHOI, which had been adapted for use with the MK5. Figure 1b shows
the locations of the MK5 casts made the
bank - wide survey, identified by the consecutive cast number. The surface and bottom temperature and
salinity distributions are shown in Figures 2 - 3. Surface and bottom anomalies
of temperature and salinity as well as a stratification index (sigma-t
difference from the surface to 30 meters) were calculated using the NMFS MARMAP
hydro-graphic data set as a reference.
The anomaly distributions are shown in figures 4-6. The distributions of surface and bottom
measured fluorescence are shown in figure 7. Profiles of each MK5 CTD cast with
a compressed listing of the preliminary data are found in Appendix C.
The volume
average temperature and salinity of the upper 30 meters were calculated for the
Bank as a whole and for the four sub-regions shown in Figure 8. These values are compared with
characteristic values that have been calculated from the MARMAP data set for
the same areas and calendar days. The
volume of Georges Bank water (salinity < 34 ) was also calculated and
compared against the expected values.
Similar to other Broad Scale surveys, all four regions were at least 0.3
fresher than the expected salinity values.
Scotian Shelf water was observed in varying degree at standard stations
8, 16, 17, 22, 24, 25, and 39. Scotian
Shelf water was not observed on the Bank during the May Broad Scale survey
ALB9605. The volume average temperature
anomaly for the northwest region was approximately 0.75_C warmer than the
temperature anomalies for the rest of the Bank.
Relatively warm
and fresh water was observed in the northwest region of the Bank. Salinity < 31.5 occurred in the upper 15
meters of the water column at standard station 38. The surface temperature and salinity distribution figures show a
horizontal gradient in the northwest region that extends toward the typically
homogenous center of the Bank. The
contoured distributions suggest the encroachment of water from the Gulf of
Maine extended further into the shallow central region of the Bank than has
characteristically been observed.
Seasonal
temperature and density stratification was established along the southern flank
of the Bank. For example, the
temperature and density difference from the surface to 25 meters at standard
station #9 was approximately 3.4_C and 0.75 sigma-t units respectively. Vertically well-mixed conditions existed at
this station during the previous Broad Scale survey in May.
A preliminary
comparison of the MK5 fluorescence data (in volts) with the total chlorophyll-a
(mg/m3) was made for the samples that were read at sea. The R2 for the data that had been
analyzed by cruise completion was approximately 0.78.
Phytoplankton Chlorophyll, Nutrients and Light Attenuation
Studies
(David W.
Townsend, Jiandong Xu and Robert Stessel)
Overview: The purpose of this GLOBEC project
is to investigate the idea that the growth and production of zooplankton and
fish on Georges Bank are limited by the amount of nutrients (especially
nitrogen) that is brought onto the Bank from the nutrient-rich, deeper waters
around the Bank’s edges (cf. Townsend and Pettigrew, 1997). Thus, we are collecting water samples on
four of the six broadscale cruises (February to May) to analyze for a suite of
nutrients and phytoplankton biomass.
The sampling period is chosen to bracket the winter-to-early summer
transition, during which time the winter nutrient levels become depleted over
much of the Bank. During this cruise,
water samples were collected for analyses of:
· dissolved
inorganic nutrients (NO3+NO2, NH4, SiO4,
PO4); · dissolved
organic nitrogen and phosphorus; · particulate
organic carbon, nitrogen and phosphorus, and · phytoplankton
chlorophyll a and phaeophytin
Methods: Water collections were made at
various depths at all of the regular hydrographic stations (Stations 1 - 40)
sampled during the May 1997 broad scale survey cruise aboard R/V Albatross, using the 1.7 liter
Niskin bottles mounted on the rosette sampler.
Additional near-surface water samples were collected at positions
between the regular stations (Stations numbered >40) using a Kimmerer Bottle
to sample a depth of approximately 2m.
In order to place the spring phytoplankton bloom into proper context, we
also measured the vertical attenuation of photosynthetically active radiation
(PAR).
Because of
weather conditions, only a single light cast was made, at CTD station 21. A
LiCor underwater spherical quantum sensor and deck-mounted cosine quantum
sensor were used to compare the underwater light field as a function of depth
corrected to coincident surface irradiance.
Data will be presented at a later date.
Samples for
dissolved inorganic nutrients and chlorophyll were collected at all regular
stations and at in-between stations (at 2 m).
Water samples for DIN were filtered through 0.45 mm Millipore cellulose
acetate membrane filters, and the samples were frozen in 20ml polyethylene
scintillation vials by first placing the vials in a seawater-ice bath for about
10 minutes. Samples will be analyzed on
shore following the cruise using a Technicon II AutoAnalyzer, and reported
later, as will all the various nutrient measurements. Water samples (50 mls) for dissolved organic nitrogen, and total
dissolved phosphorus were collected at 2 depths (2 and 20m) at each of the main
stations and frozen as described above.
These samples will be analyzed ashore using a modification of the method
of Valderrama (1981). Samples for
particulate organic carbon and nitrogen were collected by filtering 500 mls
from 2 depths (2 and 20m) at each of the main stations onto pre-combusted,
pre-ashed GF/F glass fiber filters, which were frozen for analysis ashore. The filters will be fumed with HCl to remove
inorganic carbon, and analyzed using a Control Equipment Model 240-XA CHN
analyzer (Parsons et al., 1984). Samples for particulate phosphorus were
collected as for PON (but 200 mls were filtered) and frozen at sea. Laboratory analyses will involve digesting
the sample in acidic persulfate and then analyzing for dissolved
orthophosphate.
Phytoplankton
chlorophyll a and phaeopigments were
measured on discrete water samples collected at all stations and determined
fluorometrically (Parsons et al.,
1984). The extracted chlorophyll
measurements involved collecting 100ml from bottle samples taken at depths
selected to correspond to “interesting” features revealed in the in situ fluorometer CTD cast. Samples were filtered onto GF/F filters,
extracted in 90% acetone in a freezer for at least 6 hours, and analyzed at sea
using a Turner Model 10 fluorometer.
Unusually high
values of both chlorophyll a and
phaeopigments were observed, and prompted a post-cruise recalibration of the
Turner Model 10 fluorometer (against pure chlorophyll a from Sigma Chemical). The
calibration confirmed the high values (see results presented in Table 1), which
we expect are likely the result of our not having pre-screened the water
samples (e.g., through a 200 mm mesh nitex screen) as is commonly done in order
to remove larger zooplankton. In
addition to removing the larger zooplankton, pre-screening also removes a
significant fraction of the chain-forming diatoms commonly encountered in
productive coastal waters, which we wanted to capture, thus we intentionally
did not pre-screen the samples prior to extracting in acetone.
Preliminary Results of Zooplankton Findings. (Maria Casas,
Alyce Jacquet, James Pierson and Amy Lapolla)
Zooplankton from
the 1-m2 MOCNESS samples from nets 0-4, and all pump samples will be
identified, staged, and enumerated at the University of Rhode Island, Graduate
School of Oceanography.
Preliminary
observations during this cruise showed that Calanus
finmarchicus was present in significant numbers at most stations on the
Bank. All stages were seen, but older ones were the most common. Adult females, however, were not very
abundant. Pseudocalanus spp. was
also prominent with a greater proportion of adult females. Temora
longicornis was extremely abundant, being present at almost all stations,
but more so on the crest and shallower areas. Centropages hamatus and Centropages typicus followed a similar
pattern as T. longicornis in both
abundance and distribution. Other
copepod species present in smaller numbers were Calanus hyperboreus, Metridia
lucens, Euchaeta spp., Aetideus armatus, Euchirella rostrata, and Pleuromamma
spp. Oithona spp. was not seen in as great abundance as they have been
seen in the past.
Hydroids (Clytia
spp.) were encountered in great numbers
at the shallower stations on the crest and along the southern flank. Phaeocystis occupied similar locations but
their abundance was not as great. Other dominant non-copepod species found in
moderate to high abundances during this cruise were chaetognaths, amphipods,
ctenophores, shelled pteropods, shrimps, euphausiids and cumaceans.
Following are
general observations on the plankton assemblage made at each of the stations
during this cruise using net 0 (surface to bottom - 335mm) on the 1-m2
MOCNESS and the Bongo hauls (mesh size 200mm) that were used to replace the
MOCNESS from station 30 onwards.
Station 1 Phaeocystis was very
abundant at this station with a moderate number of the shelled pteropod, Limacina, and the chaetognath, Sagitta
elegans. The most abundant copepod was Centropages
typicus. There was a moderate number of Calanus
finmarchicus (stages C4 and older), and moderate numbers of older stages of
Pseudocalanus spp. In addition, Temora longicornis was fairly abundant.
Station 2 These were very "clean"
samples, as almost no phytoplankton was present. The majority of the copepods
were C. finmarchicus and Pseudocalanus, mostly C4 and older.
Other copepods were Metridia lucens, T. longicornis and C. typicus. Lower numbers of Pteropods and Chaetognaths were also
seen.
Station 3 The abundance of C. finmarchicus gave these sample the
"strawberry daiquiri" look.
There was an absence of Centropages
spp., but a few Pseudocalanus and T. longicornis were seen. A few hyperid
amphipods and pteropods were also at this station.
Station 4 Hydroid City! And chaetognaths are
also very abundant. The copepod mix at this station are C. typicus and C. hamatus,
T. longicornis, and Pseudocalanus, in order of abundance.
Very few C. finmarchicus were
present, mostly C4 and C5.
Stations 5 and 6 Hydroids were absent from these
stations. A moderate number of shelled pteropods were present. The copepods
were mostly a mix of C. finmarchicus
( many C2 & C3), Pseudocalanus and T.
longicornis. Very few Centropages
were seen here.
Station 7 At this station there wasn't much in
the way of plankton in the water column. A few hyperid amphipods, chaetognaths,
and euphausiids were seen. A mix of Rhincalanus
spp., Aetideus armatus, T. longicornis, M. lucens, C. finmarchicus,
and Pseudocalanus were present, but
in very small numbers.
Station 8 Phaeocystis was moderately
abundant here, as were shelled pteropods. The majority of the copepods was made
up by T. longicornis, followed by Pseudocalanus (C3 and older), and very
few C. finmarchicus (C3 and older).
Station 9 Moderate numbers of Phaeocystis and chaetognaths were seen.
Lesser numbers of T. longicornis were present than in the previous
station. Moderate numbers of C.
finmarchicus (C3 and older) and C.
typicus were here.
Station 10 Many chaetognaths were present at
this station with a smaller number of barnacle cyprids. The
copepods were represented by large numbers of T. longicornis, C. typicus
and Pseudocalanus. A lesser number of C. finmarchicus was seen, mostly older
stages than C3.
Station 11 Fair number of hydroids and Phaeocystis, together with some
chaetognaths. The majority of the copepods was composed of C. typicus and C. hamatus,
T. longicornis and Pseudocalanus. Very few C. finmarchicus.
Station 12 Many hydroids present at with
station. Also a mix of cumaceans, shrimps and crab zoea. The bulk of the
copepod mix was similar to station 11.
Station 13 Hydroid City!!! Same copepod mix as
in station 12.
Station 14 Absence of hydroids at this station.
Instead Phaeocystis appears together
with some chaetognaths, shelled pteropods and mysids. The most abundant
copepods were Pseudocalanus and T.
longicornis. Some C. finmarchicus
were present, stages C2 and older.
Station 15 Again Phaeocystis was in abundance here, with more shelled pteropods than
in the previous station. Same copepod mix as in station 14, but more C. finmarchicus were seen, mostly older
stages.
Station 16 No phytoplankton in the
samples. The copepod mix was an
abundance of C. finmarchicus (C5's),
with moderate numbers of Euchaeta spp.,
M. lucens, Euchirella rostrata, and Pleuromamma
spp. Euphausiids and chaetognaths were also seen in moderate numbers.
Station 17 Almost all C. finmarchicus older stages, but some C1 and C2's. Mixed in with Calanus are some Pseudocalanus,
and a few T. longicornis. The rest of
the zooplankton is made up of hyperid amphipods, and chaetognaths.
Station 18 Phytoplankton is abundant again,
including Phaeocystis. Hydroids are
making their presence again. C.
finmarchicus is moderately abundant (all stages). There are also moderate
numbers of Pseudocalanus, T. longicornis and Centropages spp. Some mysids and chaetognaths were also seen.
Station 19 Hydroid city again. Fewer numbers of
C. finmarchicus that at station 18. The
rest are the usual Bank mix of copepods. Balance of the plankton are
polychaetes, crab zoea, mysids and chaetognaths.
Station 20 Coscinodiscus and hydroids
dominate the plankton. The rest of the plankton is a Georges Bank mix. A little
of everything.
Station 21 Coscinodiscus, shelled
pteropods and chaetognaths are here in moderate numbers. Mostly older stages of
C. finmarchicus and Pseudocalanus are in abundance, with a
few T. longicornis.
Station 22 Mostly C. finmarchicus at this station with many adult females (not seen
before on this cruise). Also a few M.
lucens, Pseudocalanus and T. longicornis were seen. Hyperid
amphipods were also abundant.
Station 23 The samples were full of copepod
molts! In between this mix there were a few C.
finmarchicus, and a mix of the usual copepods.
Station 24 Most abundant were C. finmarchicus and Pseudocalanus older stages, but not too many adults. Clean samples,
phytoplankton not a problem at this station.
Station 39 and
25 The same composition
as station 24, except quite a few C.
hyperboreus were present.
Station 26 Small (1-2cm) orange jellyfish very
abundant. The zooplankton component was made up of Pseudocalanus, C.
finmarchicus, M. lucens, T. longicornis, and Centropages spp. Phytoplankton was absent.
Station 27 and
28 Hydroids were
again abundant at this station, together with chaetognaths and a moderate
number of shrimps. The dominant copepod was Pseudocalanus
(older stages). C. finmarchicus were
few in number, stage C3 and older, few females. Also C. typicus and T. longicornis
were present in moderate numbers.
Station 29 Almost all C. finmarchicus, a mix of all stages, but older ones were most
prevalent. Mixed in the sample were also M.
lucens, Euchirella rostrata, and Pseudocalanus.
Station 30 Moderate number of hydroids, some Coscinodiscus, and chaetognaths. The
smaller components of the copepods were present at this station: C. typicus, T. longicornis, Pseudocalanus, and a few younger stages of C. finmarchicus.
Station 40 Similar to station 29.
Station 31 Many C. finmarchicus and Pseudocalanus
nauplii were seen at this station, together with Calanus C1's. the balance of the copepods were a mix of T. longicornis and C. hamatus. Some Coscinodiscus
was present in the samples.
Station 32 Coscinodiscus present at this
station. C. hamatus was very
abundant, as were Pseudocalanus and T.
longicornis. C. finmarchicus was
almost totally absent from the sample.
Station 33 A bank mix of copepods. Small
numbers of C. finmarchicus C1's were
seen as well as older stages. Pseudocalanus was more abundant. Many
nauplii of both species. Very few C.
typicus and T. longicornis were in the sample.
Station 34 C.
finmarchicus was the most abundant copepod (mostly C5's). Smaller numbers of Pseudocalanus were present. Some Coscinodiscus
were still seen in the samples.
Station 36 A this shallow station, many
polychaetes, bivalves, and some shelled pteropods were seen. Also smaller
number of hydroids, Coscinodiscus and
crab zoea were here. C. finmarchicus
was present in extremely small numbers. The balance of copepods were the
smaller sized Pseudocalanus,and Centropages spp.
Station 37 Similar to station 36, but more Coscinodiscus seen.
Station 38 Mostly C. finmarchicus present here
in great abundance. All stages from C1 to adult were seen, but the majority
were C5's.
Preliminary Summary of Ichthyoplankton Findings. (Antonie Chute,
J. Sibunka and Alyse Weiner)
Despite the impediment to visibility
caused by dense phytoplankton, observations of preserved ichthyoplankton
samples were steadfastly carried out for the duration of the cruise. As usual,
jarred samples from bongo nets A and B and 1m2 MOCNESS nets 6
through 9 were examined for the presence of fish eggs and larvae. Although far
from precise due to the aforementioned physical consistency of the catch, these
observations provide useful “quick and dirty” information regarding abundance and
distribution.
Herring (Clupea harengus)
and sand lance (Ammodytes sp.): These early-spawned larvae that dominated the catches
in the beginning the year have all but grown out of the range of our nets. Less
than 25 sand lance larvae were captured (on the eastern portion of the Bank,
average length 31mm), and no herring larvae were evident in the samples.
Cod (Gadus morhua):
Cod larvae were observed consistently but in low numbers (never more than 4 per
station) in samples from the north, northwest and central portions of the bank.
All but a few were between 12 and 26mm. Earlier this year, in March, the cod
larvae were located on the southern flank. In April, they were located
primarily on the western side. Following this pattern, the larvae seem to have
been carried clockwise toward the northeast this month. This same pattern of
clockwise motion of the main concentration of cod larvae was also evident in
1996.
Haddock (Melanogrammus
aeglefinus): Haddock larvae were captured on the southern, southwestern and
western areas of the Bank in numbers comparable to the cod larvae. All haddock
larvae observed were between 6 and 12mm in length. Since haddock are known to
spawn later than cod, these larvae may be “upstream” of cod in regard to both
position on the Bank and physical development, occupying the same size range
and distribution that the cod larvae did a month or two ago.
Yellowtail flounder/American plaice: (Limanda ferruginea/Hippoglossoides platessoides): Since the small
larvae of these two flatfish are difficult to tell apart without the aid of a
microscope, we combined them into one category. They were found in samples from
every area of the Bank except the Northeast Peak, and ranged from 6 to 13mm in
length. The largest catches (generally more than 5 larvae per station) occurred
on the central portion of the bank along the 60m isobath.
Cod/haddock/pollock eggs: In contrast to the high density
of gadid-sized eggs observed on the Northeast Peak earlier in the season,
diminished numbers of cod/haddock/pollock eggs were observed in samples from
all over the bank with no particular area of concentration evident. Only a few
eggs per jar were observed at most stations.