R/V OCEANUS Cruise OC300 Cruise Report

Cruise Report

R/V OCEANUS Cruise 300

to Georges Bank

16 - 28 March 1997

Acknowledgements

We gratefully acknowledge the very able assistance provided by the Officers, Crew, and Marine Technician of the R/V OCEANUS. In spite of frequently unfriendly winds and seas, they provided a very friendly and professional atmosphere throughout the cruise. This enabled the scientific party to successfully conduct the sampling operations and make the programed observations at essentially all of the intended stations.

This cruise was sponsored by the National Science Foundation and the National Oceanographic and Atmospheric Administration. This report was prepared by all members of the Scientific party on this cruise (see page 47) and edited by the Chief Scientist.

TABLE OF CONTENTS

Purpose of the Cruise. 4

Cruise Narrative 5

Individual Reports. 10

Hydrography 10

Sampling 10

Data: 10

Results: 11

Zooplankton and Ichthyoplankton studies based on Bongo and MOCNESS tows. 20

Objectives 20

Methods: 20

Preliminary Results of Zooplankton Findings. 22

Preliminary Summary of Ichthyoplankton Findings. 23

Sand lance (Ammodytes spp.): 23

Atlantic herring (Clupea harengus): 23

Cod-Pollock (Gadus morhua-Pollachius virens): 23

Fish eggs: 23

Miscellaneous Fish Larvae: 28

Copepod Life History Studies. 28

Can Calanus males reverse their sex? 28

Age-within-stage and diapause studies 28

Lipid analyses: total storage volume and component analyses 29

Collection for Genetic Studies. 29

Phytoplankton Chlorophyll, Nutrients and Light Attenuation Studies 30

Overview: 30

Methods: 30

Preliminary Results: 31

References: 32

Microzooplankton in the Diet of Newly Hatched Cod Larvae 38

Purpose: 38

General Procedure: 38

Post cruise processing: 39

High Frequency Acoustics. 40

System Description and Operation 40

Synopsis of Results 42

Drifter Deployments. 44

Shipboard ADCP (Acoustic Doppler Current Profiler) measurements. 44

General and constructive comments about the use of the vessel during this cruise. 45

Personnel List. 46

Scientific Party 46

R/V OCEANUS Officers and Crew 46

Appendix 1. Data Inventory. 47

Appendix 2. Summary of observations made on ichthyoplankton and zooplankton. 61

Appendix 3. CTD plots and compressed listing of the data. 64

Purpose of the Cruise.

The U.S. GLOBEC Georges Bank Program is now into its third full field season. This year follows a major effort in 1995 to study the processes of physical stratification on the Bank and the response of the biota to stratification, followed in 1996 with lower sampling effort to continue the time series of observations on the Bank. This year, is the second major effort which is focused on studying the sources for water and organisms transported onto the Bank, the processes of their retention on the Bank, and the mechanisms by which water and organism are transported off the Bank. The 1997 field program includes broad-scale cruises to map the distribution of physical and biological properties of the Bank. This cruise aboard the R/V OCEANUS is the third broad-scale cruise in a series of six cruises spaced at monthly intervals. Our effort was mainly devoted toward developing a Bank-wide context for the process work being conducted in alternate years (1995, 1997, and 1999) and the modelers who will be using both the broad-scale and process data in their model computations. Our specific objectives were:

(1) To conduct a broad-scale survey of U.S. GLOBEC Georges Bank Program of target fish (larval and juvenile cod and haddock) and copepod species (Calanus finmarchicus, and Pseudocalanus spp.), and their predators and prey to determine their distribution and abundance.

(2) To conduct a hydrographic survey of the Bank.

(3) To collect nutrient, chlorophyll, and light profile data to characterize the potential for primary production.

(4) To map the Bank wide velocity field using an Acoustic Doppler Current Profiler (ADCP).

(5) To collect individuals of C. finmarchicus, Pseudocalanus spp., and the euphausiid, Meganyctiphanes norvegica, for population genetics studies.

(6) To conduct lipid biochemical and morphological studies of C. finmarchicus.

(7) To characterize seasonal changes in the potential prey field for newly hatched cod larvae.

(8) To conduct acoustic mapping of the plankton along the tracklines between stations using a high frequency echo sounder deployed in a towed body.

(9) To deploy drifting buoys to make Lagrangian measurements of the currents.

The cruise track was determined by the position of the now 40 "standard" stations and 39 " Intermediate Bongo" stations (located half-way between the Standard Stations) that form the basis for all of the broad-scale cruises. The entire Bank, including parts that are in Canadian waters, was surveyed (Figure 1). On this cruise, sampling occurred at all but two of the 79 stations.

The work was a combination of station and underway activities. The along track work consisted of high frequency acoustic measurements of the volume backscatter of plankton and nekton throughout the water column and surface measurements of temperature and fluorescence. The ship's ADCP unit was used to make continuous measurements of the water current profile under the ship, in order to construct the current field over the whole Bank. Meteorological data, navigation data, and sea surface temperature and salinity were logged by the ship's computer system.

A priority was assigned to each of the 40 standard stations which determined which equipment was deployed during the station's activities. At high priority "full" stations, a Bongo Net equipped with a SeaBird CTD was towed obliquely to near the bottom. A CTD-fluorometer profile to the bottom was made and rosette bottles collected water samples for salinity calibration, chlorophyll, nutrients, phytoplankton species counts, and O₁₆/O₁₈ water analysis. A large volume zooplankton pumping system was used to profile the water column. A 1-m² Multiple Opening/Closing Net and Environmental Sensing Systems (MOCNESS) was towed obliquely between the surface to the bottom cycling twice to first make vertically stratified collections for zooplankton (150 µm) and then to make collections of fish larvae (335 µm). Weather permitting, a 10-m² MOCNESS was towed obliquely to make vertically stratified collections of the larger predators on the target species. Also, a Reeve net, that is designed to capture plankton very gently so as to keep them intact for identification while still alive, was vertically towed at the high priority stations or when a 10-m MOCNESS could not be deployed. At lower priority stations, a Bongo tow, CTD profile, and 1-m² MOCNESS tow were made. At the Intermediate stations, a Bongo net and SeaBird CTD system were towed obliquely to the bottom and back. At some of these stations, the SeaBird CTD/Niskin bottle cast was made for calibration purposes. A summary of the sampling events that took place during the cruise is in Appendix 1.

Cruise Narrative

In this narrative, reference made to station numbers refers to "Standard station Number" as opposed to consecutive station number, except where explicitly stated otherwise (See Figure 1).

We left Woods Hole about 1300 PM on the 16^th of March, 1997 under a bright sun, few clouds, and a blustery cold wind. Water on the deck of the R/V OCEANUS turned to ice in places and the bright orange exposure work suits were needed to stay warm while working on the deck. Our approach to Georges Bank was via the Vineyard Sound and to the south of Martha's Vineyard and Nantucket Islands because of the stormy weather and seas and the possibility that the ship might touch bottom in shoal areas in the shipping channel at the East end of Nantucket Sound. We did not steam hard down the Vineyard Sound towards Gay Head, however, but instead jogged fairly slowly while going through a safety talk, and then a fire and boat drill. After the drills, we had a short science meeting to introduce newcomers and to talk about what was going to happen on the cruise. Then it was about a 12 hour period of steaming to get to the first station.

The 17^th was a hard day to start the first days work on, because the seas were rough and the weather windy and cold. We reached Station 1 and immediately started work at 0400. The over-the-side gear had the typical startup problems and required effort between the first couple of tows to fix. For the 1-m system, the flow meter needed rebuilding to work properly. For the 10-m MOCNESS, there were problems with the net angle indicator, and the temperature and conductivity sensors. All were fixed and work proceeded at a reasonable pace in spite of the relatively minor, but time consuming problems. Only the 10-m MOCNESS could not be deployed because of the rough seas. The only instrument that was not ready to be deployed was the towed v-fin with the acoustic instrumentation known as the "Greene Bomber". It required additional preparation time. During the first days work in the Great South Channel and on the Bank, work was completed at Station 1-3 and intermediate Bongo Stations 41-43. This included releasing a single shallow (10 m) drifter at Stations 1 and 2.

It was still windy and the seas still rough during the first part of the 18^th. Although the forecast called for more high winds and snow, we had improving weather conditions and towards evening seas became reasonable. The work at the stations, however, proceeded without much difficulty, except that for much of the day, it was still not possible to deploy the 10-m MOCNESS. Instead, a 1-m Reeve ring net was deployed in its place to catch fragile gelatinous zooplankton. In the middle of the day, the Greene Bomber was deployed for a short period, but had to be returned to the deck because the acoustic equipment failed to operate properly as a result of a small amount of seawater leaking into the transducer housing. We were able to complete work at Stations 4 - 7 plus intermediates 44-46. During the evening of the 18^th, the 1-m MOCNESS on tow 7 snagged a fisherman's mooring line and surface float and dragged it during the final leg of tow 7. Fortunately, the net system was brought to the surface quickly and the line released without damage to the MOCNESS or the mooring, as far as we could tell. The last part of the tow was re-done, hence the two MOCNESS tows reported for Station 7. Sea conditions had improved enough so that the first 10-m MOCNESS was done at this station.

Weather and working conditions improved dramatically on the 19^th. Skies remained cloudy all day, but there was essentially no wind and flat seas. The work at the stations continued to go well with few glitches. The Greene Bomber, however, continued to sit on the sidelines because of electronic problems. The excellent working conditions resulted in our being able to complete work at five Standard Stations (8-12) and four intermediate stations (47-51).

On the 20^th, we were extremely fortunate to have had a second day in a row where weather and working conditions were again exceedingly good. There was again no wind and flat seas, but this time with lots of sun. The work continued as planned. Hard work and a little luck resulted in getting the acoustical instrumentations electronics problems solved and the Greene Bomber was able to be deployed at the end of Station 12 shortly after midnight. This was another good day for accomplishing the station work and we completed work at Stations 13-15 and got a good start on Station 16, a deep station in the Slope Water south of the Bank. Also done were intermediates 52- 55. The 1-m MOCNESS, which was originally built in 1975 and used extensively in the past 22 years, did not always release the nets reliably on this cruise. Thus, at Station 16, it was necessary to do a second short MOCNESS tow to sample the appropriate depth intervals.

On the 21^st , the day began with broken clouds intermingled with patches of blue sky. The wind had come up over night and was blowing a steady 20 kts out of the northwest. The seas had begun to build with a lot of white caps and breaking wave crests, in strong contrast to the previous couple of days. Weather and working conditions were not quite as good, but they were not yet something to complain about. The work continued as planned, albeit the pace was a bit slower. We were able to complete work at Stations 16-18 and at intermediate Bongo Stations 56-58.

Georges Bank's famous weather returned on 22 March, and the wonderful weather moved east. During the day, working conditions went from tolerable to marginal and then on Saturday night, we stopped work for about 8 hours while waiting for the gale that was upon us to move through and have better working conditions return. In spite of the weather, we were able to complete work at Stations 19-22 and intermediates 59-62.

During Sunday the 23^rd, the work centered on the Northeast Peak and the western side of the Northeast Channel. The work at Station 23 had been resumed following the weather break and only the 10-m MOCNESS was dropped because the seas were still too rough. The wind, however, had dropped to between 10 and 15 kts and the working conditions were not too bad. In the morning, the skies were quite cloudy and like the previous night there were off and on snow flurries streaming over a moderate sea surface with occasional white caps. By mid-afternoon, the clouds gave way to partial sunshine, although the air had a raw cold bit to it. On Sunday night there was a full moon and an eclipse which many of us saw through a partly cloudy sky during the first half of the night. Work was completed at Stations 23, 24, and 39 and intermediate stations 63-65, before steaming across the channel to Station 25.

Monday, the 24^th, was windy and cold (but sunny) and the seas were not conducive for our work. All of the scheduled work at Station 25 was completed, except that it was too rough to do the 10-m MOCNESS. There were a few tense moments when during the 1-m MOCNESS tow, the vessel and the net system came a bit too close to the Canadian current meter mooring which was at this location. In addition, a part of this tow had to be repeated because of a problem getting all the nets to open and close at the proper depths. At the end of the station, a shallow and a deep pair of drifters were released. Before steaming onto the next station, at mid-morning there was a fire and safety and then a boat drill. Just underway from Station 25, we took a wave over the starboard side of the vessel that crunched down on the 1-m MOCNESS. It caused some damage to the 3/4 " SS rods that the net bars slide down and broke one of the loops welded onto a net bar. Fortunately, the damage was repairable, but the system had to be taken completely apart and then re-assembled after the repairs which the Chief Engineer, Richard Morris, was kind enough to do. We completed work at Stations 25-27 and intermediates 66-68. However, work at Stations 26 and 27 consisted only of a couple of Bongo tows and there were no along-track bio-acoustic measurements made by the Greene Bomber; it was too rough to risk the other gear.

The weather improved sufficiently by the early morning hours of Tuesday, 25 March, to allow all of the planned work at Station 28 to be completed. We then steamed out to Station 29 in Georges Basin where the seas became calm enough to allow all of the work to be done at this High Priority Station. Following the release of a single shallow drifter, the Greene Bomber was deployed for the transit to Station 30 and then recovered before the start of this station work. During Tuesday, we kept a close watch on the weather forecasts because there were warnings for a storm to begin Tuesday evening with winds of 40 to 50 knots and lasting into Wednesday and perhaps Thursday. In anticipation of another longer cessation in work, we decided to drop Station 40 so that we might have a chance to pick up the rest of the stations that needed to be sampled by the end of the cruise. Work at the station progressed on schedule, but preparations were also underway to move all the gear that was in harms way and to batten it down so that it could handle the heavy seas and the decks awash. After the pump work was finished, the pump filtering system was moved to a safer location on the fantail and tied securely down. Similarly, after the 10-m MOCNESS was completed, it also was setup for a future deployment and then securely tied down. Two additional steel bars were added to bolt the Greene Bomber to the deck. On route to Station 31, we dropped the intermediate station between Stations 30 and 31, so that we could complete the work at 31 before the storm hit with all its fury. Around mid-night, work at Station 31 was finished and there was more effort to tie everything down or to move it into the wet lab where it would be safe (Bongo Frames and nets, hoses for washing down the nets, the pump). We then steamed out to the deep water of Georges Basin where we waited for the storm to pass. On the steam to deeper waters, we passed by Station 40 where a shallow and deep drifter were deployed. During Tuesday, we completed work at Stations 28-31 and intermediate stations 69 and 70.

Most of Wednesday morning (26 March) and early afternoon was spent slowly jogging in heavy seas, first downwind and then upwind in Georges Basin (42 19.7 N; 67 19.3 W) waiting for the storm front to come through and for better weather to arrive. Indeed, the seas were formidable, aided and abetted by a stiff wind blowing in the 30 to 40 kt range out of the southwest. On the bridge around 0900, the immense size of some of the waves was impressed upon us as the bow of the ship dove to the bottom of a trough and we, on the bridge, were looking out horizontally at the wave crest. At least one set of waves had peak heights in the 20 to 25 foot range and perhaps higher. Heavy rain squalls periodically moved through the area knocking off the sharp edges of the waves and wavelets, and smoothing for the moment the roughness of the sea surface. Shearwaters and gulls arced across the sky, cruising up upon us and gliding past as if we were standing still, which in fact we almost were. By mid-afternoon, the wind had dropped significantly, and we began to steam slowly back towards the region of the Bank in which we planned to work next.

The early diminishment of the wind and seas enabled us to resume work at Station 40 where we did all of the intended work except for the 10-m MOCNESS. It was remarkable how quickly the seas subsided after the wind diminished. The wind speed while working on station was about 20 kts and the sea while quite choppy only occasionally sported a large wave. At the end of the station, the Greene Bomber was once again in the water off the stern. The ride was not particularly smooth and the acoustic record was not very good.

The intermediate station came about 2200 on the 26th and the Bongo was done without difficulty. The problem came a few minutes after we started steaming. The 1-m MOCNESS was once again damaged by a wave that came over the starboard rail as we steamed into a rough sea to get to the next station. This time, we were able to straighten the rods enough to make the system workable by rotating them and bending them a bit by hand. It took a bit of time, but certainly much less than that needed to disassemble and re-assemble the system. Then the 1-m MOCNESS was moved over onto the deck close to the main lab where it was tied down more out of the way of waves coming over the rail. The repair time set us back an hour or so in getting to Station 32.

The work at Station 32 which started in the wee hours of 27 March, only consisted of a CTD and a pair of Bongos because of the problems with the 1-m MOCNESS and the roughness of the seas. The wind and seas made it a very slow steam to Station 33 and work at this station moved forward at a snails pace. The rough seas and the motion of the vessel, also made the acoustic records of marginal quality.

The work was completed and we moved onto Station 34 in the early afternoon of the 26^th with the winds at 20-25 kts and seas rough, but workable. By 1700 with the 10-m MOCNESS back on board, we were ready to deploy the Greene Bomber. We were in the process of putting the fish in the water at the end of Station 34 and everything went smoothly until, with the fish nearly at its towing depth, the power/signal cable caught on a cleat and the cable broke. There was nothing to do, but bring the fish back up on the deck, take it apart and splice the cable back together. At 2022, the Greene Bomber had been successfully deployed and was gathering data again, but within an hour, the system suffered another electronic failure which ended the acoustic data acquisition for the cruise.

The seas continued to diminish as the winds died down and just before midnight we arrived at High Priority Station 36 with good working conditions prevailing.

Station 36 was finished in the early morning hours of the 28^th and the work had already begun at Station 37 before the sun rose on a beautiful sunny and calm day. By mid-morning, the work at Station 37 was completed as was the short steam to the final Station (38), a High Priority Station at the southern end of Wilkinson Basin. The beautiful weather lasted the entire day and made the last stations work very pleasant. Since this was a deep station, the work took the rest of the morning and a part of the afternoon. There was a glitch with the 1-m MOCNESS tow and a part of it had to be redone after the 10-m MOCNESS was finished. Station activities ended a little before 1400 and we got underway immediately after that.

The afternoon was spent breaking gear down and cleaning the parts up. The nuts and bolts of the 1-m MOCNESS were cleaned and greased (with lanolin), and the nets washed. The pump was taken apart, as was the Greene Bomber. A myriad of things had to be done before the ship tied to the dock in the early evening and all of the scientific personnel worked like beavers to get the job done.

Because of the calm seas, we came in by way of Nantucket Sound. As we steamed down the Sound, the Island of Nantucket appeared a gray thin strip of land to our south jutting just above the flat waters of the sound. The sun was low in the sky and a few clouds were on the horizon. The wonderful weather of the day was moving east and less pleasant weather was in the offing. But for that period, it was the kind of an end to a cruise that makes the effort so worthwhile. Lines were thrown to dock about 2010 on 28 March and thus ended a quite successful broad-scale survey of Georges Bank.

Individual Reports.

Hydrography

(David Mountain and Maureen Taylor)

Sampling

The primary hydrographic data presented here 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.

Bongo hauls were made at each of the stations occupied. 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 following is a list of the CTD data collected with each of the sampling systems used on the cruise:

Instrument # Casts

MK5 38

MK5 calibration 38

SBE19/Bongo 80

SBE19 calibration 9

The MK5 was deployed with 10 bottles on the rosette and samples were collected for various investigators. At primary #1 and #2 stations, 400 mls were immediately siphoned out of two Niskins (bottom and mid-depth) for observations of micro-zooplankton swimming behavior (S. Gallager and L. Lougee, WHOI). Samples were collected for oxygen isotope analysis at selected depths for R. Houghton (LDGO) and a sample was taken at the bottom for calibrating the instrument's conductivity data. Chlorophyll and nutrient samples were collected at various depths by D. Townsend and J. Xu. Surface samples for phytoplankton species composition were collected and preserved for J. O'Reilly (NMFS) at full (priority 1 and 2) stations only.

Parameter # samples taken

Oxygen isotope 145

Micro-zooplankton 63

Species composition 18

Data:

The SBE19 Profiler and the MK5 data were post-processed at sea. The Profiler data were processed using the Seabird manufactured software: DATCNV, FILTER, ALIGNCTD, BINAVG, DERIVE, ASCIIOUT to produce one 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 one decibar files using algorithms provided by R. Millard of WHOI, which had been adapted for use with the MK5.

Both CTD systems worked well during the cruise. Due to weather, the MK5 system was not deployed on two stations (standard stations 26 and 27) and the SBE19 data from the Bongo tow at those stations were substituted as the primary hydrographic data (shown as cast numbers 153 and 156, respectively, in Figure 3b).

Results:

A total of 77 consecutive and 40 standard station locations were occupied during the bank-wide survey (Figure 3). The surface and bottom temperature and salinity distributions are shown in Figures 4 - 5. 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 hydrographic data set as a reference. The anomaly distributions are shown in Figures 6 - 8. The distribution of fluorescence (expressed in volts) at the surface and bottom are shown in Figure 9.

The volume average temperature and salinity of the upper 30 meters were calculated for the four sub-regions shown in Figure 10. 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 PSU) was also calculated and compared against the expected values. Profiles of each MK5 CTD cast with a compressed listing of the data are shown in Appendix 3.

The salinity over nearly the entire Bank was 0.7 - 1 PSU fresher than the MARMAP reference (especially along the southern flank and Northeast peak area due to an influx of Scotian Shelf water. The lowest salinities and temperatures were observed along the southeast edge of the Bank at Standard Stations 17, 22, 24, 39 and across the Northeast Channel to Station 25). Surface temperature and salinity at Station 25 were 1.49C and 31.32 PSU respectively. These values suggest a westward flow of Scotian Shelf water across Northeast Channel and along the southern edge of the Bank. The negative anomalies of temperature and salinity along the northeast and southeast fringe of the Bank are most likely a result of this intrusion of relatively cold and fresh Scotian Shelf water.

The water columns on the Bank (< 80 m water depth) were well mixed, except on the eastern part of the bank, where the intrusion of Scotian Shelf water in the near surface layer (0-25 m) resulted in stratification (0.1-1.1 sigma-t units).

The fluorescence values (volts) were generally low, compared to values observed later in the season in earlier years. The highest fluorescence values during this cruise were in the shallow, central portion of the Bank and at Station 25 (Figure 8). The latter values are believed associated with density structure caused by a surface layer of low salinity Scotian Shelf Water.

Zooplankton and Ichthyoplankton studies based on Bongo and MOCNESS tows.

(John Sibunka, Maria Casas, Peter Garrahan, James Gibson, Pilar Heredia, and Alyse Weiner)

Objectives:

(1) Principle objectives of the ichthyoplankton group in the broad-scale part of the U.S. GLOBEC Georges Bank Program were to study the composition of the larval fish community on Georges Bank, to define larval fish distribution across the Bank and within the water column, to determine those factors which influence their vertical distribution, and to determine bank-wide versus "Patch-Study" mortality and growth rates. Emphasis in this study is on cod and haddock larvae along with their predators and prey. This study also includes larval distribution and abundance, and age and growth determination. These objectives were implemented through use of Bongo net and MOCNESS to make the animal collections.

(2) The primary objective of the zooplankton group was completion of a bank-wide survey of Georges Bank to determine the distribution, abundance, and stage composition of the target species Calanus finmarchicus and Pseudocalanus spp. A second objective was to identify, quantify, and describe the occurrence of abundant non-target species in order to provide a description of the environment occupied by the target species. These objectives were implemented by using the 1-m² MOCNESS, a vertically discrete, multiple opening and closing net system for sampling the copepodite stages of the zooplankton, and a submersible pump for sampling the naupliar stages.

In addition to these objectives, the zooplankton group was responsible for the following:

(a) To collect fifth naupliar stage Calanus finmarchicus for RNA/DNA ratio analysis to be completed by Melissa Wagner at the University of Rhode Island.

(b) To take subsamples from the 1-m² MOCNESS hauls for population genetic studies of Pseudocalanus spp. to be completed by Dr. A. Bucklin at the University of New Hampshire.

Methods:

Bongo tows were made with a 0.61-m frame fitted with paired 335 µm 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 ~40 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. A Seabird CTD was attached to the towing wire above the Bongo to monitor sampling depth in real time mode and to measure and record temperature and salinity. Once back on board, the 335 µm mesh nets were each rinsed with seawater into a 330 µm mesh sieve. The contents of one sieve was preserved in 4% formalin and kept for ichthyoplankton species composition, abundance and distribution. The other sample was kept for age and growth analysis of any larval fish collected and preserved in 95% ethanol. 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 µm mesh and 200 µm 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 ~40 m/min and 20 m/min respectively. Upon completion of the tow, the nets were each rinsed with seawater into a corresponding mesh sieve. The sample from the 200 µm mesh net was retained for zooplankton species composition, abundance and distribution, and preserved in 10% formalin. The other sample from the 335 µm mesh net was kept for molecular population genetic analysis of the copepod, C. finmarchicus, 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.

The 1-m² MOCNESS sampler was loaded with ten nets. Nets 1-4 were fitted with 150 µm mesh for the collection of older and larger copepodite and adult stages of the zooplankton. Nets 0, and 5-9 were fitted with 335 µm 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 µm mesh sieve, subsampled using a 2-L plankton sample splitter if the final volume was too large, then preserved in 10% formalin. Samples from nets 5-9 were sieved through 330 µm 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 selected stations, 90-ml subsamples from the bottom and surface 150 µm mesh nets were removed and preserved separately in 10% formalin for Dr. C. Miller. 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 between Pseudocalanus species found on Georges Bank.

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 15 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 µm 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 starboard side hydro boom by connecting the suction end, fitted with a 1.7-L Niskin bottle cut in half lengthwise, to the winch 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. A 70 kg weight was 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 85 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 µm mesh nets, sieved through a 30 µm 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 going into the net and 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 4-5 m/min. This rate was used to obtain volumes of 500 L per 5 m depth interval sampled.

To collect Calanus finmarchicus nauplii for the RNA/DNA analysis, a vertical haul was completed by using a 1-meter diameter ring net fitted with 100 µm mesh and a standard MOCNESS cod end (taped with duct tape so only a few holes were open). These hauls were made at Standard stations 12, 20, 29, and 38. The net was attached to the winch wire together with a 70-kg weight. This array was lowered to a maximum depth of 75 meters and retrieved at approximately 4-5 m/min. The animals caught in the cod end were gently poured into a 5-gallon plastic bucket. A few liters from this bucket were placed in several beakers and kept on ice. The contents were then sieved through 100 µm mesh and rinsed into another beaker using MS-222 solution to anesthetize the animals. Naupliar stage 5 C. finmarchicus were sorted and removed from small volumes in petri dishes. Twenty-five animals were collected from each station, placed into cryotubes, and then frozen in liquid nitrogen. These samples will be analyzed for RNA/DNA content at the University of Rhode Island by Melissa Wagner.

A 1-meter Reeve net, fitted with a 335 µm mesh net was used to sample for large lobate ctenophores (i.e. Bolinopsis and Mnemiopsis). Tows consisted of a vertical cast off the starboard side hydro boom from surface to 15 m off the bottom or to a maximum depth of 200 m. Wire pay out and retrieval rates were ~20 m/min and 5 m/min respectively. A 70 kg weight was used to depress the sampler. At the completion of the cast, the contents from the cod-end bucket were sieved through a 300 µm mesh sieve. Large jelly fish were counted and measured (oral and aboral length) to the nearest millimeter with a metric ruler. The entire catch was preserved in 5 % buffered formalin.

Preliminary Results of Zooplankton Findings.

( Maria Casas, Peter Garrahan, James Gibson, and Pilar Heredia)

Observations of the 1-m² MOCNESS samples from nets 0-4, and all pump samples will be staged and enumerated at the University of Rhode Island Graduate School of Oceanography GLOBEC Counting Laboratory.

Zooplankton observations of the 1-m² MOCNESS tows from net 0 are summarized in Appendix 2. In general, there was the typical Bank mix of copepods with Calanus finmarchicus and Pseudocalanus spp. being the most abundant. Also present were Centropages typicus and C. hamatus, Metridia lucens, Oithona spp., Euchaeta spp., and Temora longicornis in lesser quantities..

The spring phytoplankton bloom on the Georges Bank is underway. The most common species were the diatoms Coscinodiscus and Rhizosolenia, with Phaeocystis. These were mostly concentrated on the Bank crest and the shallower stations on the southern flank. The hydroid, Clytia, was evident in many of the shallower stations on the crest and around the edges of the Bank in moderate quantities. The dinoflagellate, Ceratium was also present in some stations on the North East Peak.

Samples Collected by the Zooplankton and Ichthyoplankton Groups:

Gear Tows Number of Samples

1. Bongo nets, 0.61-m 80 tows

335 µm mesh 77 preserved, 5% formalin

335 µm mesh 80 preserved, EtOH

200 µm mesh 3 preserved, 10% formalin

2. MOCNESS, 1-m² 41 tows

150 µm mesh 152 preserved, 10% formalin

335 µm mesh 151 preserved, 10% formalin

335 µm mesh 142 preserved, EtOH

3. MOCNESS, 10-m² 13 tows 67 preserved, 10% formalin

3.0-mm mesh

4. Pump 18 profiles 52 preserved, 10% formalin

30 µm mesh

5. Reeve net 13 tows 13 preserved, 4% formalin

335 µm mesh

Preliminary Summary of Ichthyoplankton Findings.

(J. Sibunka and A. Weiner)

Samples collected for ichthyoplankton analysis at the 40 GLOBEC broad-scale Standard Stations from both the Bongo and 1-m² MOCNESS (nets 6-9) and from the, additional Bongo stations were examined on shipboard for the presence of fish eggs and larvae. This was done in an attempt to determine their occurrence on the Bank and obtain a gross estimate of distribution, abundance and size range. The following discussion on ichthyoplankton catches is based on these findings.

Sand lance (Ammodytes spp.):

Sand lance larvae (maximum size range 10-38 mm; mean size range 15-20 mm) dominated the catches in both abundance and occurrence of larval fish collected this cruise (Figure11). Their distribution ranged virtually across the entire survey area of Georges Bank except that few to no larvae were collected in the south-east to the North East Peak portion of the Bank and those stations in the Gulf of Maine The largest catches of sand lance larvae occurred in the western portion of Georges Bank. There did not appear to be a regional concentration of either small or large larvae in any area of the Bank. Compared to the results from the March 1996 broad-scale cruise (refer R/V OCEANUS No. 275 cruise report) the larvae collected on this survey were similar in size, but their distribution on the Bank were more extensive. During the survey in March 1996, sand lance larvae were more restricted in their distribution and were concentrated across the central and southern portion of the Bank.

Atlantic herring (Clupea harengus):

Atlantic herring larvae (size range 35-48 mm) were caught at only a few stations across the central and northern portion of Georges Bank (Figure 12). Catch abundance for the cruise was small with an estimated total number of 61 larvae from both the Bongo and 1-m² MOCNESS samplers combined. These results are similar to the findings reported in the March 1996 broad-scale survey (refer R/V OCEANUS No. 275 cruise report), but in contrast to the results reported from the March 1995 broad-scale survey (refer R/V ENDEAVOR No. 263 cruise report) in which Atlantic herring larvae dominated the catches in both abundance and occurrence across the Bank. The size range of the larvae collected on all three March cruises were virtually the same.

Cod-Pollock (Gadus morhua-Pollachius virens):

Larval cod/pollock (microscopic observation is required for separation and positive identification between the two species) were collected in small numbers (estimated total of nine larvae) at stations located in the western portion of Georges Bank and at Standard Stations 8 and 18 (Figure 13). The size range of these larvae was between 8-20 mm. The area of occurrence for cod/pollack larvae collected on this cruise agrees with results of the March 1995 and 1996 broad-scale surveys (refer R/V ENDEAVOR No. 263 and R/V OCEANUS No. 275 cruise reports) and also with the historical NEFSC MARMAP data for the month of March on Georges Bank.

Fish eggs:

Cod/pollock/haddock eggs observed in the plankton samples collected during this cruise were distributed from the south central to east central portion of Georges Bank. The largest catches were made from the south-east portion to the Northeast Peak area of the Bank, with the largest catch (estimated 1,000 eggs) at Standard station 20 (Figure 14). The distribution and abundance of large gadoid eggs are similar to the results reported for the March 1996 broad-scale survey (refer R/V OCEANUS No. 275 cruise report) and the distribution of eggs on Georges Bank during this survey is in agreement and resembles the historical MARMAP data results for the month of March.

Miscellaneous Fish Larvae:

The following fish larvae were also identified in the ichthyoplankton samples collected during this broad-scale survey.

1. Sculpin Myoxocephalus sp.

2. Paralepididae

3. Lantern fish (juv. & adult) Myctophidae

4. Cusk Brosme brosme

Copepod Life History Studies.

(Jennifer Crain and Charles B. Miller, Oregon State University)

During this cruise, we continued to gather samples for our ongoing examinations of life history patterns of Calanus finmarchicus on Georges Bank. Our projects fall into four major categories: (1) continued analysis of the frequency and environmental correlates of the apparent plasticity in sex determination of Calanus. There is evidence of a sex switch occurring at maturation in a significant portion of the genetic males in the population. We are teasing the problem apart from several angles, including correlation with fecundity data being gathered by Jeff Runge and proposed use of molecular methods to determine the genetic sex of individuals, (2) continued examination of jaw morphology as a diapause signature in fifth copepodites, and correlation with lipid storage and gonad development, and as an indicator of age-within-stage of all copepodite stages. The age-within-stage of individual C5's will be compared with RNA/DNA ratios, determined by Melissa Wagner at URI. (3) analysis of fat storage by fifth copepodites, using images captured at sea and Charlie's new algorithm for calculating oil sac volumes in conjunction with gas chromatography for component analyses, and (4) a substantial contribution to the GLOBEC modelling effort using "individual vector models", being developed by Charlie Miller during his six month sabbatical in Nice, France.

Can Calanus males reverse their sex?

We have found definite seasonal trends in the proportions of quadritheks (possibly genetic males which have developed as females) in our Georges Bank samples from 1994, 1995 and 1996. We will continue to monitor this trend using formalin preserved sub-samples from selected 150 micron 1-m MOCNESS nets on this and subsequent broad-scale cruises. On this cruise, we collected sub-samples (90/600 ml) at standard stations 3, 4, 7, 9, 12, 13, 16, 17, 18, 20, 23, 25, 39, 29, 30, 40, 34, 36 and 38. This was a good month for sampling adults. Most of the adult Calanus found were females, although there are still a number of males present.

We hope that we will be able to determine the underlying genetic sex of individual Calanus and correlate the quadrithek antennal morphology with genetic maleness. We are attacking this problem by analysis of DNA fragment lengths, which are expected to be different in X and Y chromosomes, and searching for highly multiple repeat sequences characteristic of sex chromosomes. For these analyses, we are cryopreserving adult male and female Calanus. On this cruise, adults were sorted from our sub-samples and frozen live in liquid nitrogen from stations 3, 7, 14, 16, 22, 23, 29, 30, 40, 33, 34 and 38. Ethanol preserved sub-samples from 1-m MOCNESS net 5 (90/400 ml) taken at Standard Stations 3, 4, 7, 9, 12, 13, 16, 18, 19, 20, 23, 25, 39, 29, 30, 40, 34, 36 and 38 will also be used for biochemical analyses.

Age-within-stage and diapause studies

We have been analyzing jaw facies of fifth copepodites to determine the fractions of their stocks that are A) entering the copepodite resting stage typical of this species, and B) preparing for immediate maturation. Copepodites of the A group retain the postmolt facies, a large hemocoele extension into the mandibular gnathobase, which looks like a bubble. Copepodites of the B group quickly lose this 'bubble'. We are dissecting and examining the jaws of individuals from the formalin preserved subsamples listed above for this analysis.

Jaw staging is also an indicator of an individual's age-within-stage. As the animal progresses through each stage, the jaw facies pass through recognizable as postmolt, late postmolt, intermolt and tooth formation phases. Preliminary analyses of jaw phases of individual second through fifth copepodites from 1995 Broad-scale subsamples have yielded some interesting results with respect to the population dynamics of Calanus on Georges Bank. The formalin preserved subsamples listed above will be used for continuation of this effort.

Samples of healthy C5's from Stations 16, 22, 23, 30, 33 and 34 were cryopreserved for RNA/DNA analysis at URI by Melissa Wagner. Jaws will be dissected from the individual specimens upon thawing to correlate jaw facies with metabolic activity.

Lipid analyses: total storage volume and component analyses

We are studying the large store of oily wax which C. finmarchicus secretes into a tubular sac in the prosome of the fifth copepodite stage, prior to either maturation or rest. Actually all copepodite stages have such sacs and accumulate some oil. The main question under study in 1997 is the areal and seasonal variation in quantities of oil in C5. Oil is quantified by an integration of oil sac projected area in video pictures and approximate conversion to oil volume, using image analysis and an algorithm recently worked out by Charlie Miller for calculating an accurate volume estimate from the area. On OC298, there were very few C5's present in our subsamples, but sets of digital images were captured at standard stations 3, 7, 16, 18, 20, 23, 29 and 30. Fifth copepodites are recorded in groups of five, then cryopreserved for gas chromatographic analysis of the relative amounts of triacylglycerides and wax ester.

Collection for Genetic Studies.

(Neile Mottola)

Our current understanding of winter variations in zooplankton production on the Bank is limited. Further, the sources of populations of target species C. finmarchus and Pseudocalanus spp. which increase on the Bank during late winter and spring, are poorly defined. Individuals are believed to come onto the Bank from the Gulf of Maine, Gulf of St. Lawrence, Scotian Shelf, and possibly the Slope Water. However, it is has not been possible to discern morphological differences between individuals originating from separate areas off the Bank. Consequently, population genetic studies of Calanus, Pseudocalanus, and several other species, including the euphausiid Meganyctiphanes norvegica, are being conducted at the University of New Hampshire. The work above is tied directly to other efforts to identify water sources and losses for the Bank, as well as circulation and exchange processes across the Bank boundaries. Our understanding of pteropods on the Bank is also somewhat limited. There are two subarctic species that are known to occur in and around Georges Bank: Limacina retroversa (dominant species) and Limacina helicina. These species occur in both hemispheres which indicates a bipolar distribution. Bipolarity can be explained by climatic warming during the recent geological past which has caused the present-day separation of a once continuous distribution along the boundary currents of the Atlantic and Pacific oceans (Be' and Gilmer, "Oceanic Micropaleontology", Vol. 1, Ch. 6, pg. 756). Thus, are these still the same species? Genetic studies of these species, taken from samples from the California current and Georges Bank, will help to identify viable genes that will distinguish the different possible species. Research for this project is also being conducted at the University of New Hampshire. On this cruise samples were collected at every station for genetic studies with net # 5 on the 1-m² MOCNESS except in the occurrence of bad weather when a Bongo tow with a 335 µm mesh was substituted. At selected stations, 90 ml sub-samples from the bottom and surface 1-m² MOCNESS with 150 µm mesh nets were taken. All samples were preserved in 95 % ethyl alcohol which was changed during the first 24 hour period after collection.

Phytoplankton Chlorophyll, Nutrients and Light Attenuation Studies

(David W. Townsend and Jiandong Xu, University of Maine)

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 broad-scale cruises (February to May) to analyze for a suite of nutrients and phytoplankton biomass. The sampling period was 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 March 1997 broad-scale survey cruise aboard R/V OCEANUS, 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 2 m. In order to place the spring phytoplankton bloom into proper context, we also made measurements of the vertical attenuation of photosynthetically active radiation (PAR).

Light casts were made at three stations during this cruise, including two stations "on the Bank" (Stations 10 and 15; Figure 16) and one station off the Bank in Georges Basin (Station 29). Measurements were made at or about noon (preferably between 1100 and 1300 hours); these three stations represented the only instances when we were "on station" at noon, and when the sea state allowed a light cast. 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 are presented in Tables 1-3.

Samples for dissolved inorganic nutrients and chlorophyll were collected at all Stations, 1 - 40, and at in-between stations (at 2 m). Water samples for DIN were filtered through 0.45 µm Millipore cellulose acetate membrane filters, and the samples were frozen in 20 ml 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 ml) for dissolved organic nitrogen, and total dissolved phosphorus were collected at 2 depths (2 and 20 m) at each of the main stations and frozen as described above. These samples will be

Phytoplankton chlorophyll a and phaeopigments were measured on discrete water samples collected at all stations (see Table 4) and determined fluorometrically (Parsons et al., 1984). The extracted chlorophyll measurements involved collecting 100 ml 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. A preliminary summary of surface chlorophyll a concentrations at all stations is presented in Figure 17.

Preliminary Results:

The only data immediately available following the cruise (i.e., on the steam into port) are the CTD data (D. Mountain) and the light and chlorophyll data collected here. Nevertheless, there were a number of interesting chlorophyll concentration patterns that revealed themselves. First of all, the spring phytoplankton bloom was underway at several of the shallower on-Bank stations (<60m depth), where concentrations exceeded 5 µgL^-1 (Figure 17). There were also relatively high concentrations in conjunction with a mass of cold, fresh, and buoyant Scotian Shelf Water (SSW), which had been advected across the Northeast Channel. The SSW was evident

References:

Parsons, T.R., Y. Maita and C.M. Lalli. 1984. A Manual of Chemical and Biological Methods for Seawater Analysis. Pergamon, Oxford. 173 pp.

Townsend, D.W., L.M. Cammen, P.M. Holligan, D.E. Campbell and N.R. Pettigrew. 1994. Implications of Variability in the Timing of Spring Phytoplankton Blooms. Deep-Sea Res. 41: 747-765.

Townsend, D.W. and N.R. Pettigrew. 1997. Nutrient limitation of secondary production on Georges Bank. J. Plankton Res. 19(2): 221-235.

Valderrama, J.C. 1981. The simultaneous analysis of total nitrogen and total phosphorus in natural waters. Marine Chemistry 10: 109-122.

Tables 1-3. Vertical profiles of photosynthetically active radiation (PAR) attenuation, with computed values of the percent surface light, and the diffuse attenuation coefficient.

Station 29, 25 March 1997

The Importance of Microzooplankton in the Diet of Newly Hatched Cod Larvae: Broad-scale Studies of Prey Abundance

Cruise OC300

(Scott Gallager, Philip Alatalo, and Ladd Lougee)

The objective of this study was to characterize seasonal changes in the potential prey field for newly hatched cod larvae with respect to prey motility patterns and the prey size spectrum.

Prey Size, Abundance and Motility Experiments:

Purpose:

To observe, record and analyze motility patterns and size spectrum of available prey from three locations in the water column- near bottom, pycnocline, and upper well-mixed area at all broad-scale stations from January through June.

General Procedure:

Water samples were collected from the near bottom, and pycnocline areas of the water column using Go-Flo bottles on the Mark-5 CTD. Surface samples also were collected from the surface with a bucket over the side. Go-Flo bottle samples were collected by gently siphoning from the top of the bottle instead of the normal port so that microplankton were not disrupted. Two-hundred ml tissue culture flasks were filled after being dipped in soapy water and air dried to prevent fogging. To further prevent fogging, as well as maintain a constant low temperature, the flasks were transferred to an incubator at 5° C immediately after filling.

Each flask, in turn, was placed in a holder across from a B/W high-resolution Pulnix camera fitted with a 50 mm macro-lens and directly in front of a fiber optic ring illuminator fitted with a far-red filter. This apparatus was suspended within the incubator by bungee cord to reduce vibration produced by the ship. Recordings were made using a Panasonic AG1980 video recorder with SVHS formatted cassettes, a Panasonic TR-124MA Video Monitor, and a timing device for a period of 15 minutes for each sample. The flask was then replaced with the next sample and recordings continue. The field of view was set to ~10 mm.

The following samples were taken:

Station Sample

1 0 and 20 meter

3 0, 60, and 82 meter

4 0, 20, and 51 meter

5 0, 20, and 57 meter

7 0, 60, 140, and 257 meter

8 0, 40, and 81 meter

9 0, 40, and 70 meter

10 0, 20, and 46 meter

13 0, 20, and 51 meter

15 0, 40, and 71 meter

16 0, 60, 100, 140, and 301 meter

18 0, 40, and 77 meter

19 0, 20, and 54 meter

20 0, 40, and 70 meter

22 0, 40, and 103 meter

23 0, 30, 43, and 75 meter

39 0, 60, 120, and 216 meter

25 0, 40, 100, and 215 meter

28 0, 30, and 59 meter

29 0, 20, 44, 80, and 286 meter

30 0, 20, and 46 meter

40 0, 75, 100, and 185 meter

32 0, 30, and 35 meter

33 0, 20, and 50 meter

34 0, 49, 99, and 206 meter

36 0, 20, and 45 meter

37 0, 20, and 60 meter

38 0, 40, 100, and 145 meter

Each priority 1 station was preserved in 10% Lugols. All other priority station samples were discarded.

Post cruise processing:

Motility patterns will be analyzed with the Motion Analysis EV system. The final output will be particle size distribution and a motility spectra associated with each particle. This will be compared with species composition in the microzooplankton samples preserved in Lugols.

High Frequency Acoustics.

(Peter Wiebe and Erhan Mutlu)

The bioacoustical endeavor on this cruise was a continuation of efforts to make high resolution volume backscattering measurements of plankton and nekton throughout the Georges Bank region. The goal is to acquire acoustical data that can be used to provide estimates of the spatial distribution of biomass of acoustical targets which span the size range of the target species (cod, haddock, Calanus, and Pseudocalanus) and their predators. The spatial acoustical map can also provide a link between the physical oceanographic conditions on the Bank and the biological distributions of the species as determined from the net collections at the stations distributed throughout the Georges Bank region. Work on this cruise was intended to obtain continuous acoustic sampling along all the shipboard survey tracklines covering the entire Georges Bank region. However, electronic problems with the instrument and poor sea conditions conspired to limited the number of along track transects that we were able to obtain (Figure 18; Table 5)

System Description and Operation:

The acoustic and environmental sensor packages were mounted in an ENDECO towed 5-foot V-fin fish nicknamed the "Greene Bomber". The tow-body has dimensions of 1.5 m length x 1.5 m width x 0.9 m height, and, on this cruise, weighed approximately 100 kg in air. For this cruise, the interior of the tow-body carried a single BioSonics, Inc. digital 120 kHz transducers and a transmit pressure case. The transducer was operated in a down-looking mode. In addition, an environmental sensing system (ESS) was mounted inside the V-fin with temperature, conductivity, sensors mounted in the rear underneath the tail of the fish on a SS round and flat stock mounting bracket and fluorescence sensor was placed in front of the fiberglass housing on a stainless steel round-stock framework. Initially, this was one of the newer 16-bit systems which had been modified for use in a towed instrument body. As described in more detail below, this system was replaced mid-way through the cruise with an older 12-bit system, because the 16 bit system failed electronically.

The Greene Bomber was deployed off the starboard side of the stern of R/V OCEANUS. A TSE winch (loaned by the WHOI rigging shop) was equipped for launching, recovering, and towing the v-fin with a hundred+ meters of 1 1/8" Nylon line (breaking strength of approximately 40,000 lbs). A thimble was made into the end of the cable and attached to the towing bail of Greene Bomber. Also attached to the towed body was a separate cable for power and data telemetry and a safety line (1" [2.5 cm] diameter braided nylon line - breaking strength ~15,000 lbs). The tow line and the other two lines were wrapped together at about 0.5 m intervals with electrical tape reinforced with heavy duty tie-wraps starting at the towing bail and extending about 2 meters. The tow line was led through a wide-cheeked block hanging shackled to a pad-eye on the outer margin (starboard side) of the A-frame, and the power/telemetry cable and safety line were led through a second block shackled to the nearest in-board pad-eye. The safety line and power cable were secured to cleats bolted to the deck. The TSE winch was located on the starboard side of the main deck about 30' (9.14 m) forward of the stern. The preferred towing speed was ~8 knot.

The procedure for launching was to have the A-frame positioned with the block directly over the towing point on the towed body. Tension was taken up on the tow line, and then the A-frame was moved out-board, lifting and moving the fish out beyond the stern. A line through the nose-guard was used to steady the fish. The winch operator then lowered the line to get the towed body down into the water. The steadying line was released once the fish was in the water. Recovery was essentially the reverse. A single length of cable was used to tow the Greene Bomber which put the towed body about 4-5 m below the surface.

The power/telemetry cable was led into a 20' Van specifically designed for acoustics data acquisition which was located on the aft portion of the 01 deck. Individual conductors were hooked to either a bank of three power supplies or to two data acquisition 80486 computers (one for the acoustics data and the other for the environmental sensor data). Two programs, developed at WHOI, were used to acquire, process, store, and display the data. Some post-processing was done at sea on a Pentium computer.

To view the operation of the Greene Bomber remotely from the van, two video cameras were mounted on the 0-1 level looking down at the main deck. One camera (#1) had a fixed location which was set at the beginning of the cruise facing aft so that the field of view included the towing lines and the area of the deck where the Greene Bomber was located when not in the water. The second camera (#2) had pan/tilt and zoom capabilities and could be used to view most of the over-the-side operations going on along the starboard rail and the stern. Each camera had its own monitor and the output from camera #2 was fed into a Panasonic SVHS tape recorder which was used to document launch and recovery of the various oceanographic instruments used during the cruise. This system worked very nicely.

At the onset of the cruise, we had some significant problems with the underwater electronic packages in the towed body.

ESS Woes: Before we ever got the Greene Bomber into the water, a deck test revealed that neither the temperature or salinity sensors were working. We determined that the problem was that the sensor cables had bad connecting plugs. In fact all of them turned out to be faulty and had to be replaced. A good portion of the morning was spent splicing cables.

Acoustic Transducer Woes: The first deployment of the fish on the 18^th resulted in a flooded transducer bottle and no data were collected. It wasn't apparent where the water came in. The electronics boards were removed from the housing and washed them with alcohol, but it was not until we permanently disconnected the wide beam pair of boards and used only the narrow beam circuitry that we were able to get the system running again. The entire episode of cleaning and testing the various components took a couple of days, but we were finally able to make it operational. The fish was successfully deployed and began data acquisition on 20 March.

More ESS Woes: After 36 hours of operation, a second electronic failure occurred, this time in the ESS electronics unit, again because a small amount of water leaked into the 16-Bit ESS housing. After discovering that there was water in the underwater unit, we immediately set about drying off all the parts and rinsing them with alcohol. Although we did get the unit working, we decided to put the backup 12-bit system into the Greene Bomber because we suspected the water had entered through one or more of the bulk-head connectors and this problem could not be fixed at sea. It took about 7 hours to re-configure this backup system including more cable splicing to enable the sensors to be plugged into the 12-bit underwater housing. We were finally able to deploy the system again and continue data acquisition about 2030 hrs on the 21^st of March.

Synopsis of Results: Acoustical data were obtained on the deployments of Greene Bomber along five sections of cruise track, between stations 12-17, stations 22-25, stations 29-30, stations 40-34, and in the vicinity of station 35 (Figures 1, 18; Table 5). The total distance traveled along the trackline where acoustical data were collected was 437 km (234 nm). This is about a third of the 1300 to 1500 km of trackline that is usual for a complete sampling of the Bank and substantially less than weather would have permitted had the gear functioned properly.

A preliminary look at the acoustical records as the data were being collected revealed a typical pattern of a well-mixed pattern from the top of the Bank to the shelf/Slope Water front. There was very little horizontal layering, i.e., the vertical gradients were small. Beyond the front, a stratified structure was evident and there was strong vertical variation and horizontal layering. As we have seen on earlier cruises, internal wave structures were observerd in the stratified areas. No strong solitons were encountered as has typically occurred on previous cruises to the Bank.

Table 5. Acoustic Data Summary and concomitant observations. Note that acoustic data files are written in one hour blocks on a continuous basis while the software toggle switch "record data" is on. Thus, there are as many hourly data files as there are hours between the "time in" and the "time out".

Drifter Deployments.

As part of the physical oceanographic studies of the current structure and circulation on Georges Bank being conducted by R. Beardsley and R. Limeburner, GLOBEC Drifter Buoys are deployed at strategic locations periodically throughout the year to track the Lagrangian flow from the point of deployment. This drifter is constructed with a holey sock drogue (a Dacron cylinder 90 cm diameter by 3 m tall with 5 circular hoop stays) at the bottom connected by either a 10 m or a 40 m cable to a small float (18 cm diameter) which in turn is connected by about 2.6 m of cable to a larger spherical surface float (about 32 cm diameter). The surface float contains a sea surface temperature sensor, a GPS receiver, and an ARGOS satellite transmitter. Temperature, time, and position data are transmitted periodically to shore through the ARGOS telemetry system. On this cruise, nine drifters were deployed, a single ten meter (shallow) drifter at stations 1, 2, and 29 and two drifters, (10 m and 40 m (deep)) at Stations 25, 40, 34, and 38.

Shipboard ADCP (Acoustic Doppler Current Profiler) measurements.

The flow field over Georges Bank is driven by a complex set of forces. A primary factor is the strong semi-diurnal tides which dominate the high frequency variability (< 1 cpd) of the currents. Tidal rectification gives rise to a persistent sub-inertial clockwise circulation over the Bank. This circulation process can be substantially modified by the frequent storms common to the area, changes in the stratification of the Bank, and interactions with currents generated by offshore circulation features (i.e. Warm-Core Rings).

The Acoustic Doppler Current Profiler (ADCP) is one of the instruments being used to study the circulation processes on the Bank by J. Candela and C. Flagg. Water current measurements were obtained using two RDI ADCPs operating at 150 kHz and 300 kHz. The 150 kHz was not used when the Greene Bomber was being towed because this system interfered with the operation of bio-acoustic 120 kHz echosounder. The 300 kHz system was operated continuously during the entire cruise. The transducers were mounted on the hull of the ship (5 m below the surface). The instrument was programmed to measure the current profile under the ship with a vertical resolution of 2 m, from 10 m depth to about 10 m from the bottom or up to a depth of about 120 m, whichever was shallower at a given location. The ADCP measures currents with respect to the ship. To obtain the water current with respect to the ocean bottom, the ship's motion needs to be removed from the current observations. The ship's motion will be removed using the bottom track (BT) velocity measured by the ADCP. Depending upon sea conditions, the ADCP can perform this operation in water depths shallower than 200 to 230 m. When the BT is lost, accurate navigation is used to remove the ship's velocity from the current.

The ADCP data collected on this cruise will be post-processed at Woods Hole Oceanographic Institution by Candela and Flagg.

General and constructive comments about the use of the vessel during this cruise.

The vessel was found to be well equipped, maintained and laid out for working on deck and in the labs. The stern A-frame used for deploying the 10-m² MOCNESS system worked well for setting and retrieving the MOCNESS sampler. The officers and crew of R/V OCEANUS were very helpful, friendly and worked well with the scientific party. The Marine Tech assisted in solving the problems that arose and at times in the repair of scientific gear. It was a great help to have her aboard. Also, the scientific party greatly appreciated the culinary efforts of the galley staff.

The following specific comments are intended to help improve future operations on the vessel.

1. The starboard boom was used for deploying the 1-m² MOCNESS and Bongo plankton samplers for oblique tows and the CTD and plankton pump hose for a vertical cast on station. Its maximum rate (horizontal) of movement is too slow. At times (i.e. adverse weather conditions), it is important for safety reasons to move gear in and out at a "quicker" rate. Therefore, a wider range of boom speed is desirable for future cruises of this type. This comment was made in the report for the March 1996 cruise (Oceanus 275) and it is still true.

2. A digital depth recorder is still needed to provide depth readings as part of the along track logging data set. In addition to real-time readouts around the ship, the U.S. GLOBEC Program needs access to such data to help build a better data base from which digitally based bathymetery charts of Georges Bank can be created.

3. In the Sleeping Van, the locker cabinet doors must now be opened in pairs and when the ship is rolling the doors often swing and bang uncontrollably. Some way needs to be found to enable each of the doors to be opened separately while the other remains locked.

Personnel List.

Scientific Party

Name Title Organization

1. Peter H. Wiebe Chief Scientist WHOI, Woods Hole, MA

2. Laurence Lougee Technician WHOI, Woods Hole, MA

3. Erhan Mutlu Postdoctoral Investigator WHOI, Woods Hole, MA

4. David Mountain Scientist NMFS/NEFSC, Woods Hole

5. John Sibunka Fisheries Biologist NMFS/NEFSC, Sandy Hook

6. Maureen Taylor Technician NMFS/NEFSC, Woods Hole

7. Alyse L. Weiner Biol. Sci. Technician NMFS/NEFSC, Sandy Hook

8. Maria C. Casas Research Associate URI/GSO, Narragansett, RI.

9. Peter R. Garrahan Research Associate URI/GSO, Narragansett, RI.

10. James W. Gibson Biol. Sci. Technician URI/GSO, Narragansett, RI.

11. Pilar Heredia Biol. Sci. Technician URI/GSO, Narragansett, RI.

12. David Townsend Scientist U. Maine, Orono, MN

13. Jiandong Xu Student U. Maine, Orono, MN

14. Jennifer A. Crain Biol. Sci. Technician OSU, Corvallis, OR.

15. Neile Mottola Student UNH, Durham, NH

16. Jennifer Frese Student Bowdoin College, New Brunswick, MN

17. Nancy Bazilchuk Journalist MIT, Cambridge, MA

19. Laura G. Stein Technician WHOI, Woods Hole, MA

R/V OCEANUS Officers and Crew

15. Lawrence Bearse Master

16. Courtenay Barber III Ch. Mate

17. Emily McClure 2nd Mate

18. Jeffrey M. Stolp Boatswain

19. Christopher M. Griner AB

20. Sean Burke OS

21. Horace M. Madieros OS

22. Richard F. Morris Ch. Engineer

23. J. Kevin Kay Jr. Engineer

24. Jennifer Siros Jr. Engineer

25. Mitchel Barros Steward

26. Jovinol J. Fernandes, Jr. M/A

Appendix 1. Data Inventory.