Thanks to Capt. Courtenay Barber III and the crew of R/V Oceanus for a trouble-free and pleasant April 1999 running of the GLOBEC Georges Bank BroadScale Survey. Everything was professionally run in every respect.
This report was prepared by Charles Miller, David Mountain, John Sibunka, Rebecca Jones, David Townsend, Gretchen Stoltz and Steve Brownell
OC341 was sponsored by the National Science Foundation and the National Oceanic and Atmospheric Administration.
Table of Contents
Trackline of Oc341
Personnel on Oc341
Hydrographic Report - D. Mountain and C. Bascunan
Zooplankton and Ichthyoplankton Studies (Methods, Sample numbers) - J. Sibunka and others
Preliminary Summary of Zooplankton Findings - J. Pierson
A Different Zooplankton View - C. B. Miller
Preliminary Summary of Ichthyoplankton Findings - R. Jones and J. Sibunka
Preliminary Summary of 10m2 MOCNESS Results - S. Brownell
10m2 MOCNESS Species Lists - G. Stoltz
Phytoplankton Chlorophyll, Nutrients and Light Attenuation
Studies - D. W. Townsend
Appendix 1: Hydrographic Profiles
Appendix 2: R/V OCEANUS Cruise OC341 - Event Log
Oc341 was devoted to the 28th BroadScale survey of the GLOBEC Northwest Atlantic Program. We sampled over and around Georges Bank, which bounds the south side of the Gulf of Maine. BroadScale surveys are intended to delineate patterns in the distribution of cod and haddock larvae and in their food organisms, principally copepods. Plankton samples are gathered with a pump (50 m mesh) and both 70 cm bongo and 1-m2 MOCNESS nets. Micronekton are sampled with 10-m2 MOCNESS nets. Biological sampling is accompanied by CTD profiles and chlorophyll and nutrient data are gathered at every station. A study was carried out on gonad development in fifth copepodites of Calanus finmarchicus, and videographs were collected of both copepod gonadal types and of a variety of plankton. ADCP data were collected throughout the expedition, and we launched five Lagrangian drifters for satellite tracking.
On the cruise track (p. 2) we sampled at all of the 41 standard stations and all of the intermediate bongo haul stations on the BroadScale survey grid. Dr. Wiebe did not participate in this cruise, so there was no along track acoustic surveying. The only planned observation not made was one 10-m2 MOCNESS haul at an early station because we found we had no installed calibration file for its depth sensor. That was rectified in time for the second scheduled haul.
We departed Woods Hole at 10:00 on 16 April,1999, as scheduled. Our route to Station 1 was SW around Martha's Vineyard, then direct to Station 1. We commenced work at 22:00 the same date, and continued through the stations in order and on schedule. The chief scientist chose to lie to during about eight hours at the location of Station 40. This was during daylight hours on 24 April. Winds were 25-30 knots and it was decided to protect the worn gear from damage in the rising seas. Winds dropped by evening and we returned to work.
During that storm break, we were in an area being worked by a fishing boat named "Sea Farmer". They called to say they had drift nets near the bottom throughout the vicinity of Station 40 and requested we move our sampling site 6 nautical miles away. We chose a new station that far to the southwest along the same contour as Station 40. The rest of the survey was completed without incident. At Station 38 we made live collections with the 1-m MOCNESS for Dr. Gallager, failing to find many Limacina retroversa, the species he hoped we could collect. There were a few of very small size (200 m) which were returned to shore in barrels. We did not add any extra scientific activities and returned to Woods Hole a day ahead of schedule the morning of 27 April.
Courtenay Barber III Master
Anthony Diego Mello Chief Mate
Emily Sheasley 2nd Mate
Horace Madeiros Boatswain
Michael James Diefenbach OS
James R. Ryder AB
Peter J. Liarikos AB
Richard Morris Chief Engineer
Jeffery Vigeant Jr. Engineer
Alberto Collasius, Jr. Jr. Engineer
Torii Corbett Steward
Jesse Lee Brown Mess attendant
Charles B. Miller Chief Scientist - Oregon State University
Christina Bascunan NMFS/NOAA, Woods Hole
Stephen Brownell NMFS/NOAA, Narragansett
Ryan Campbell GSO/URI, Narragansett
Joshua Fredrickson GSO/URI, Narragansett
Rebecca Jones NMFS/NOAA, Narragansett
Jesse Lamb GSO/URI, Narragansett
David Mountain NMFS/NOAA, Narragansett
Keith Mountain Volunteer
James Pierson GSO/URI, Narragansett
Melanie Sorenson Oregon State University
David Townsend University of Maine, Orono
Gretchen Stoltz San Francisco State University
John Sibunka NMFS/NOAA, Sandy Hook
Brian Kaminer Marine technician, WHOI
The primary hydrographic data presented here were collected with a Seabird 911+ CTD (SBE911+) system, which provides measurements of pressure, temperature, conductivity, and fluorescence at a rate of 24 observations per second. The fluorescence values are reported in volts - correcting a factor of 2 problem identified in the March survey cruise report (EN320). The CTD is equipped with a rosette (Seabird 32 carousel) for collecting water samples at selected depths. Profiles with the SBE911+ were obtained at each standard station that was occupied. Bongo hauls were made at all of the stations occupied. A Seabird model 19 profiling CTD (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
SBE911+ calibration 40
SBE19/ Bongo 82
SBE19/ calibration 9
The SBE911+ was deployed with 10 bottles on the rosette and samples were collected for various investigators. Samples were collected for oxygen isotope analysis at selected depths (R. Houghton, LEDO) and a sample was taken at the bottom for calibrating the instrument's conductivity data (D. Mountain, NMFS). Samples for chlorophyll and nutrient analysis were taken from multiple depths at each of the standard stations (see the section in this report by D. Townsend, Univ. of Maine).
Preliminary processing of the SBE Profiler and 911 data was completed at sea using the Seabird manufactured software routines to produce 1 decibar averaged ASCII files.
The location of the standard stations and the intermediate bongo stations where SBE profiler data were collected are shown in figure 1 [TIF version]. The location and cast number of the SBE911+ profiles are shown in figure 2 [TIF version]. Using SBE911+ data, the surface and bottom temperature and salinity distributions are shown in figures 3 [TIF version] and 4 [TIF version]. Temperature and salinity anomalies (using the MARMAP reference) are shown in figures 5 [TIF version] and 6 [TIF version]. Stratification over the upper 30 meters of the water column and the stratification anomalies relative to the MARMAP hydrographic data reference are shown in figure 7 [TIF version]. The distributions of fluorescence are shown in figure 8 [TIF version].
The volume average temperature and salinity of the upper 30 meters were calculated for the four sub-regions shown in figure 9. 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 MARMAP values. The SBE911+ profiles for each standard station, along with a compressed listing of the preliminary data, are provided in Appendix B.
The surface salinity distribution (figure 4 [TIF version]) indicates the intrusion of low salinity water from the Scotian Shelf onto the eastern and southern parts of Georges Bank. The Scotian Shelf influence appears to extend westward to about 68 W, considerably farther west than observed on the March survey. The salinity of the intrusion - with values < 31.75 PSU - also was substantially lower than was observed in March. The surface temperature distribution indicates that this water was also somewhat colder than that over the rest of the Bank (< 6 c), as would be expected. The Scotian Shelf water is not evident in the bottom parameter distributions (figure 3 [TIF version] and figure 4 [TIF version]).
The anomaly distributions (figure 5 [TIF version] and figure 6 [TIF version]), as well as the values in figure 9, show that the Bank was fresher and warmer than the MARMAP reference - as were the conditions in February and March. The -0.4 PSU salinity anomaly in the NW portion of the Bank (figure 9) is similar to that observed in March and supports the suggestion made in the March cruise report that the very low salinity conditions reported in the previous years may be abating.
Stratification (figure 7 [TIF version]) on the Bank was limited to where Scotian Shelf water - with its low surface layer surface salinity - was intruding on the eastern and southern parts of the Bank. The surface fluorescence values (figure 8a [TIF version]) indicate low (< 0.3) values in the Scotian Shelf water intrusion and relatively higher values (> 0.4), apparently intruding from the Gulf of Maine, along the northern flank and northwest corner of the Bank. Higher values (> 0.5) were observed at the bottom in the shallow central part of the bank (figure 8b [TIF version]). The Bank-wide average fluorescence value in the 0-30m layer was 0.4 volts, about twice that observed in March and comparable to that observed in April of 1997 and 1998, but significantly lower than the values observed in April 1995 and 1996.
(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 1-m2 MOCNESS to make the zooplankton and ichthyoplankton collections. A 10-m2 MOCNESS was used to collect larger pelagic invertebrates and juvenile fish.
(2) The primary objective of the zooplankton group was to complete 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 for sampling copepods and larger zooplankton. A bongo-Jelnet cast was made to collect gelatinous predators and a deck-mounted diaphragm pump with deployed suction hose was used to sample copepod naupliar stages.
In addition to these objectives, the zooplankton group was responsible for obtaining
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.
Bongo tows were made with a 0.61-m frame fitted with paired 335 m 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 profiler 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 m mesh nets were rinsed with seawater into a 330 m 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.
The 1-m2 MOCNESS sampler was loaded with ten nets. Nets 1-4 were fitted with 150 m mesh for the collection of older and larger copepodite and adult stages of the zooplankton. Nets 0, and 5-9 were fitted with 335 m 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, downward tows. 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 m 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 m 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, 100-ml subsamples were taken from nets 1-4 (150 m mesh) and preserved in 10% formalin for Dr. C. Miller (OSU). At priority 1 and 2 stations, 100-ml subsamples from nets 1-4 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.
The 10-m2 MOCNESS was loaded with five 3.0 mm mesh nets. Tows were oblique from surface to ~10 m above 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 330 m mesh, and preserved in 10% formalin.
A gasoline powered diaphragm 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 affixing a release shackle to the end of the hose and clipping it to the weight used to depress the array. Snap clips attached to the hose at 10 m intervals were clipped to the winch wire as the hose was deployed. A book clamp was positioned on the winch wire just above the end termination to keep the hose from falling down on the termination as the wire was raised during retrieval. Clipping the hose to the winch wire assured that the hose was no more than 5 m from the wire and kept it from getting fouled on the ship. This arrangement also allowed the hose to move vertically along the winch wire as it was retrieved. The 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 or four 30 m sections of 7 cm diameter hose were connected to the pump, allowing the intake hose to attain a maximum depth of approximately 100 m. At shallow stations (<100 m), the intake nozzle was lowered to 3-5 meters off the bottom. The discharge end of the hose was diverted to a surge dampener before it entered the collection net. This caused the flow to be laminar as it passed the flow meter, allowing a more accurate measurement of flow rate. Once the hose had been deployed to the desired depth it was raised at a constant rate and samples collected. Wire retrieval rate was approximately 4 m/min which provided volumes of about 200 L per 5 m depth interval. Sampling depths were from the maximum depth to 75 m, 75-40 m, 40-15 m, and 15 m to the surface. The hose was allowed to flush for a predetermined interval before collection began, before each net change, and once the hose had reached the surface. Flushing time was calculated based on the flow rate of the pump and depending on the length of hose used at each station. The three integrated depth samples were collected with 30 m mesh nets, sieved through a 30 m mesh sieve and preserved in 10% formalin.
To collect pteropods for live experiments, we used the 150 m mesh nets on the 1-m2 MOCNESS. The animals caught in the cod end buckets were allowed to settle for several minutes. The top portion of the zooplankton was decanted off and discarded. The settled part of the collection, mostly the pteropod Limacina retroversa were released into 30-gallon containers previously filled with seawater using the diaphragm pump system. These samples were returned to Woods Hole to be studied by Dr. Scott Gallager.
Samples Collected by the Zooplankton and Ichthyoplankton Groups:
|Gear||Tows||Number of Samples|
|1.||Bongo nets, 0.61-m||82 tows||85 preserved, 5% formalin|
|335-µm mesh||87 preserved, EtOH|
|2.||MOCNESS, 1-m2||41 tows|
|150-µm mesh(Nets 1-4)||124 preserved, 10% formalin|
|335-µm mesh(Net 0)||39 preserved, 10% formalin|
|335-µm mesh(Nets 5-9)||170 preserved, EtOH|
|3.||MOCNESS, 10-m2||22 tows|
|3.0-mm mesh||110 preserved, 10% formalin|
|35-µm mesh||63 preserved, 10% formalin|
|1000-µm mesh||10 preserved, 10% formalin|
Preliminary observations were made from the samples collected using the 1-m2 MOCNESS after preservation. Calanus finmarchicus appears to be distributed throughout most of the regions of the bank. But this seems to be a Metridia lucens year. It appears to be more abundant at most stations where it was observed than C. finmarchicus. All along the deep stations along the northern portion of the bank at stations 34 and 38, and 40, the water column was almost exclusively M. lucens.
The diatoms, Coscinodiscus and Rhizosolenia were in full bloom at many of the stations inside the 100 m isobath. The ctenophore, Pleurobrachia spp. was also very abundant at many of the stations sampled. And, the pteropod, Limacina spp., was not as numerous as in previous broadscale cruises this year.
I must have been on another cruise from Pierson, Campbell and Lamb, given their observations above. I must say, I never saw any of them look through their microscope. Metridia lucens was indeed present, but it did not exceed Calanus finmarchicus in abundance in respect to either numbers or biomass. Calanus constituted the bulk of the plankton at all stations except directly up on the bank inside the 50 m isobath. At stations on the south flank deeper than 80 m the samples were quite rich, a drained liter or more of "strawberry daiquiri", principally C. finmarchicus. At stations along the northern slope and in the Gulf (29, 40, 38) we caught more Calanus than at any time in 1998. From several depths at several stations we had to split and discard during preservation. That did not happen at all in 1998 and is reminiscent of the larger
stocks sampled in 1995 and 1996. Most of the specimens on the south flank were C4 and C5, with a few adults of both sexes. Most C5 in the southern gulf were in very early stages of gonad development. Thus, the stock looks to be completing "G1", the first spring generation.
In regard to Metridia being abundant, there was in fact markedly less luminescent squirting in the nets from Metridia than I have seen in many other years. The Pierson et al. view is correct regarding Pleurobrachia; they were abundant everywhere and we caught substantial volumes in some levels with the MOC-10. Limacina retroversa were present at a few stations, but never reached the dominance they exhibited during the January cruise. The observation of abundant diatoms is correct; they were often a problem for the preservers. Both Coscinodiscus and Rhizosolenia were abundant at these scattered "bloom" sites, but there was a complex mixture of smaller species in among them as well.
Inside the 50-m isobath, we caught different things at different stations. On the southwest corner at least one station had copious Clytia sp., the hydroid seen in many spring and summer cruises in the shallow center. It was present but not abundant to the northeast. Centropages hamatus was present across the shoal portion, much more abundant to the northeast. Near bottom samples from several shallow stations contained Sagitta elegans juveniles almost exclusively. Pseudocalanus spp. were present everywhere, but abundant nowhere in the entire system.
Jennifer Crain and I are trying to figure out the meaning of two different types of gonad rudiments that we see in fifth copepodites of Calanus. These are a small, blackjack-shaped cell mass with the thin end forward found in a swirl of open membranes, provisionally called "rudiment-in-a-bag", and a longer string of cells forming a small saddle over the oil sac, provisionally termed "low and flat". We suspect these are an early difference between testes and ovaries during development, but we don't know which type becomes which sex. We are experimenting with that on 1999 BroadScale cruises by rearing sorted groups using filter- concentrated seawater as food. About 50 specimens were reared to late C5 on OC341.
Figure 10, microvideographs taken with Dave Townsend's equipment show the distinction
Figure 10. Calanus finmarchicus, C5. Left, specimen with "low and flat" facies for rudimentary gonad. Right, specimen with "rudiment-in-a-bag" facies. Both rudiments are marked with small arrows.
Results from this experiment must be reported elsewhere.
During the cruise, shipboard samples from all the 5% formalin preserved Bongo Net B nets were examined while in the jar for the species present and the quantities of fish larvae and eggs were estimated. These quick observations were done in attempt to obtain a qualitative estimate of ichthyoplankton abundance, distribution and size ranges on Georges Bank.
Cod (Gadus morhua) larvae
Cod larvae were concentrated in the central portion of the bank at standard stations 11-14, with standard station 10 having the highest number at approximately 100. All larvae were 3-8 mm with the exception of a few post-flexion larvae (~40 mm) observed at stations 60, 20 and 38. Low numbers of larger larvae were also observed along the northern edge around standard stations 31-38 (10-20 mm). It is interesting to note that larval distribution was the same as the previous March with the only difference being the greater numbers found during this 1999. The 1995 (see cruise report EN265) cruise is the most similar to the easterly distribution observed during this cruise. It's possible that spawning was later this year and in 1995.
Haddock (Melanogrammus aeglefinus) larvae
Haddock were mostly observed along the southern flank in between the 60 and 100-meter isobaths. The highest number was approximately 100 (3-8 mm) at station 51, which is well to the east of the distribution observed 1996-1998 (see cruise reports EN282, OC302 and OC322). One post-flexion larva was observed at standard station 28 (~30 mm). In 1995, EN265, the distribution was also well to the east but abundance was lower. A minor concentration of larvae was also observed along the Great South Channel (standard stations 1-41). These Great South channel fish were the highest in number (20) at station 43 (3 - 8 mm).
Cod/Haddock or Witch flounder eggs
The eggs of cod, haddock and witch flounder are difficult to differentiate without the aid of magnification. Eggs were observed at most of the stations on the bank in low numbers. Egg distributions from the last 4 years generally have shown concentrations at the northeast peak. However, in this month there were so few eggs that no patches were readily discernable.
Miscellaneous larvae (in order of abundance):
redfish (Sebastes marinus)
sand lance (Ammodytes ammodytes)
sculpin (Myoxocephalus sp.)
yellowtail flounder (Limanda ferruginea)
American plaice (Hippoglossoides plattesoides)
Atlantic herring (Clupea harengus)
sea snail (Liparis sp.)
rock gunnell (Pholis gunnellus)
The samples collected from the 10-m2 MOCNESS were examined on shipboard for a qualitative estimate of abundance, distribution, and size range of both the invertebrate and the fish community at selective stations. The following observations are based on examination of the samples after preservation.
Station 7 Haul 2
Ctenophores, naked pteropods, squid, salps, hyperiid amphipods, gnathostroma
Station 7 Haul 3
Euphausiids, ctenophores, naked pteropods, isopods, cod.
Station 9 Haul 4
Ctenophores, decopod shrimp, isopods, naked pteropods, myctophid, sculpin, haddock, cod, herring.
Station 12 Haul 5
Ctenophores, naked pteropods, hyperiid amphipods, sculpin, herring, haddock.
Station 13 Haul 6
Isopods, ctenophores, polychaetes, naked pteropods, sculpin, wolf fish.
Station 16 Haul 7
Euphausiids, ctenophores, hyperiid amphipods, squid, lobster larvae, naked pteropods, myctophids, gnathostroma, viper fish.
Station 17 Haul 8
Ctenophores, isopods, naked pteropods, euphausiids, hyperiid amphipods, myctophids, gnathostroma, eel.
Station 18 Haul 9
Ctenophores, euphausiids, hyperiid amphipods, shrimp, isopods, polychaetes, chaetognaths, sculpin eel, cod.
Station 20 haul 10
Ctenophores, naked pteropods, sculpin, cod.
Station 23 Haul 11
Ctenophores, isopods, shrimp, naked pteropods, hyperiid amphipods, euphausiids, polychaetes, cheatonaths, herring, cod.
Station 25 Haul 12
Ctenophores, cheatonaths, salp houses, jellyfish, pyrosomes, cod.
Station 39 Haul 13
Ctenophores, polychaetes, shrimp, jellyfish, herring.
Station 27 Haul 14
Ctenophores, hyperiid amphipods, cod.
Station 29 Haul 15
Euphausiids, naked pteropods, ctenophores, hyperiid amphipods, shrimp, herring, cod.
Station 30 Haul 16
Ctenophores, hyperiid amphipods, herring.
Station 40 Haul 17
Euphausiids, ctenophores, naked pteropods, hyperiid amphipods, cod.
Station 32 Haul 18
Station 34 Haul 19
Euphausiids, naked pteropods. ocean pout, herring, cod, haddock.
Station 34 Haul 20
Euphausiids, ctenophores, naked pteropods, herring, cod.
Station 36 Haul 21
Euphausiids, naked pteropods, shrimp, herring, cod.
Station 38 Haul 22
Euphausiids, ctenophores, naked pteropods, cod.
Editor's note: no text was provided with this listing. It is Ms Stoltz's species list developed from 10-m MOCNESS hauls.
|Phronima sp./salp houses|
|Phronima sp./salp houses|
|Phronima sp./salp houses|
|Phronima sp./salp houses|
|Phronima sp./salp houses|
|Phronima sp./salp houses|
Water samples were collected during the April 1999 R/V Oceanus Broad Scale survey cruise to Georges Bank for the analysis of:
Only the chlorophyll data are reported here; other data can be found on our web site:
Collections were made at various depths at all of the regular hydrographic stations sampled during the April 1999 broad scale survey cruise aboard R/V Oceanus using the 1.7 liter Niskin bottles mounted on the rosette sampler. Additional surface water samples were collected at positions between most, but not all, of the regular stations (Stations numbers >41) using water collected from the ship's flowing seawater system (sample depth ca. 2m).
Samples for dissolved inorganic nutrients and chlorophyll were analyzed at all stations at which water was collected. Water samples for DIN were filtered through 0.45 m Millipore cellulose acetate membrane filters, and the samples frozen immediately 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 immediately following the cruise using a Technicon II 4-Channel AutoAnalyzer.
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 (Stations 1-41) 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, and filters 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 will be 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 (see Table 1) and determined fluorometrically (Parsons et al., 1984). The extracted chlorophyll measurments involved collecting 100ml from all bottle samples taken at depths shallower than 60m, filtering through GF/F filters, and extracting the chlorophyll in 90% acetone in a freezer. The samples were analyzed at sea using a Turner Model 10 fluorometer. These data will be used in regressions against measurements of in situ fluorescence as part of the regular CTD casts.
Parsons, T.R., Y. Maita and C.M. Lalli. 1984. A Manual of Chemical and Biological Methods for Seawater Analysis. Pergamon, Oxford. 173 pp.
Valderrama, J.C. 1981. The simultaneous analysis of total nitrogen and total phosphorus in natural waters. Marine Chemistry 10: 109-122.
Figure 13. Station locations for April 1999 R/V Oceanus broadscale cruise.
Figure 14. Surface chlorophyll a (extracted) for April 1999 R/V Oceanus Cruise.
Table 1. Chlorophyll data for April 1999 R/V Oceanus
GLOBEC Georges Bank Broad Scale Survey Cruise.
Table 1. Chlorophyll data for April 1999 R/V Oceanus GLOBEC Georges Bank Broad Scale Survey Cruise.
|Station||Date||Time of CTD (L)||DecLat||DecLon||Depth||(ug/L)||(ug/L)|
Hydrographic Appendix - Standardized results from all CTD casts on OC341
Cruise OC341 Event Log