R/V ALBATROSS IV
AL9612
Cruise Report

Table of Contents:

Cruise Narrative

Figure 1. Cruise Track

Individual Reports

Zooplankton

Preliminary Zooplankton Results

Carbon Production

Optics/Primary Production

Table 2. Sampling operations and samples collected

Appendix A. Personnel List

Appendix B. Event Log

Appendix C. Hydrographic Data

Acknowledgements

We appreciate and acknowledge the efforts and professionalism of the officers and crew of the ALBATROSS IV. Their assistance and cooperation made the success of this cruise possible.

This report was prepared by Jim Gibson, with inputs from all Principal Investigators. The contributions of Pilar Heredia, who maintained the event log during the cruise and Maureen Taylor, who prepared the hydrographic data, were greatly appreciated.

The US-GLOBEC Georges Bank research project is sponsored by the National Science Foundation and the National Oceanic and Atmospheric Administration. All data in this report are to be considered preliminary.

Individual Reports

Zooplankton Abundance, Physiological Condition, and Growth Rates

( J. Gibson, P. Heredia, A. Jacquet, D. Schreiber)

Objectives

(1) To collect zooplankton samples at pre-selected priority 1 Broadscale standard stations during the long interim between Broadscale survey seasons.

(2) To determine the size (length, carbon, nitrogen) and condition (condition factor, RNA/DNA ratio) of Calanus finmarchicus at selected sites on the Bank.

Methods

Zooplankton tows were made with the 1-m² MOCNESS equipped with five 150 _m mesh nets and cod ends. Tows were single oblique from the surface to a maximum depth of 10 m. off the bottom or 500 m. The depth stratum sampled were: 0-bottom; bottom-100m; 100-40m; 40-15m; and 15m-0. The net #0 was used as the down net, and nets #1, 2, 3 and 4 for the up-cast.. Winch rates were 15-20m/min. to control volumes filtered and maintain a frame angle near 45 degrees. Once back on board, the nets were gently rinsed with seawater into corresponding 5 gal. buckets and transported into the wet lab. Samples with a large biomass were split prior to preservation, using a 2-L plankton splitter. Samples were then preserved in 10% formalin.

At stations 38 (night), 29 (day) and WB, the bottom and surface nets (#1 and #4) were not immediately preserved. 50 Calanus finmarchicus stage 5 copepodites were sorted from the bottom net only, using dissecting microscopes. Calanus abundance's in the surface net were to low to collect enough animals. The animals were recorded using a video system for length measurements, and were either placed in a tin boat and dried over desiccant for carbon analysis or put into cryotubes and frozen in liquid nitrogen for RNA/DNA determinations.

Prior to every MOC-1 tow, a vertical cast with a Seabird Electronics Seacat model 19 profiling instrument (SBE19 Profiler) was done to measure temperature and salinity, with depth. The Seabird CTD was clamped to the boom wire and a 45-kilogram (kg) ball was attached to depress the sampler.

Productivity

Organic and Inorganic Carbon Production in the Gulf of Maine.

(L. Graziano, D, Drapeau, S, Dunford, B, Vallincourt)

Two main types of measurements were made: productivity/calcification rates of phytoplankton, and optical backscattering.

1. Productivity: Calcification and organic production rates were measured in profiles at 12 stations, and in 8 additional surface samples. One bottle per depth was incubated with ¹⁴C-HCO₃ for 24 hours, at simulated in situ temperature and light quantity and quality. Surface samples were taken from the ships seawater system while underway. For profiles 6 depths were used, and an additional bottle was incubated in the dark. Water was collected from Niskin bottles after determining appropriate depths, based on percentage light. A Biospherical PNF (Profiling natural fluorescence) meter was lowered at daytime stations to collect light, depth temperature, and fluorescence data. A Secchi disk was also used to measure to 1% light depth. Water was collected from depths at 90%, 50%, 20%, 10%, 5%, and 1% of surface irradiance. Depths were estimated at night-time stations.

100 mL water/bottle was spiked with 50 _Ci 14C. Subsamples were immediately taken for total ¹⁴C (100 _L) and for time-zero radioactivity in particulates (2 x 50 mL, filtered). After incubation for 24 hours 2 x 50 mL from each bottle was filtered to collect particulate material. Each filter represented organic and inorganic carbon production over 24 hours. Filters were processed on board to separate organic and inorganic carbon into two different vials. Radioactivity in each vial was measured on a scintillation counter at Bigelow. Total number of bottles incubated: 92. Total number of vials: 472.

For each bottle incubated, samples were collected for particulate calcite (100 mL filtered) and cell and Coccolith counts (60 mL preserved in buffered formalin). A total of 81 calcite samples and 76 preserved sampled were collected.

2. Underway backscattering measurements: A flow-through system continuously measured fluorescence, temperature, salinity, pH, and optical backscattering before and after dissolution of calcite, at all times while the ship was underway. Backscattering was also measured on discrete samples at six depths at each station.

Optics/Primary Production

Complete Optical Datasets Throughout the Gulf of Maine

(Dave Phinney, J Hopkins, Doug Phinney, J Brown)

Our cruise activities aboard the Albatross IV were performed in support of a NOAA grant entitled 'Development and Validation of Regional Time-Varying Coastal Marine Algorithms: Gulf of Maine - A Case Study'. This grant is primarily devoted to the development and validation of regional ocean color remote sensing algorithms for the Japanese Ocean Color and Temperature Scanner (OCTS) launched in September, 1996, and the forthcoming NASA Sea Wide Field-of-view Sensor (SeaWiFS). Ocean color algorithms are the mathematical equations which derive ecological and oceanographic parameters such as phytoplankton chlorophyll or ocean transparency from the spectral water leaving radiance (light) measured by the satellite sensor from space. In order to build such algorithms, precise measurements of the optical properties of ocean waters, the concentrations of optically active substances found in these waters and the quantity of spectral light exiting the ocean must be made in a variety of oceanographic regimes. Of particular importance to this project is the goal of building regionally specific algorithms for the Gulf of Maine, hence, the opportunity to collect measurements in the highly variable region around Georges Bank in November was deemed valuable. This work is conducted in cooperation with Dr. W.M. Balch at Bigelow Laboratory, Dr. J. Zaitzeff at NOAA/NESDIS and Dr. J. Brock at NOAA Coastal Services Center in Charleston, SC.

Objectives

The objective of this work is to collect complete optical datasets in diverse water mass types throughout the Gulf of Maine in support of ocean color algorithm develop-ment. This includes measurements of 1) the inherent optical properties of absorption and scattering, 2) concentrations and distributions of optically active substances such as chlorophyll, colored dissolved organic matter (CDOM), total suspended solids, phyto-plankton identification/enumeration, and cell size spectra, 3) optical reflectance spectra at the sea surface and 4) calibrated spectral water leaving radiance. Dr. Balch's group also collects total and calcite specific backscattering data as well as particulate calcite and particulate organic carbon concentrations. All of these optical measurements are made within the context of traditional physical oceanographic measurements of salinity, temperature and density. We participated in twelve stations during the cruise, one on top of the bank, one in Wilkinson Basin and ten around the periphery of Georges Bank.

Instrumentation and Methods

A profiling package was used to continuously measure the physical and optical properties of the water column as a function of depth to 75m. The package consisted of a SeaBird SeaCAT 19 CTD, WetLABS miniature in situ fluorometer configured for chloro-phyll fluorescence, and a WetLABS AC9 nine channel spectral absorption/attenuation. meter. The package was deployed at a nominal rate of 20 meters/min. The SeaCAT 19 measures temperature, conductivity and pressure at 2Hz as well as logging companion data from up to two external sensors. The CTD operates in autonomous mode logging the data internally as well as powering a sample pump and external sensors. The external sensor was a WetLABS miniature chlorophyll fluorometer used to measure the distribution of phytoplankton biomass as a function of depth. All the data were downloaded to a laptop computer after the cast, with salinity and density calculated by standard subroutines as Practical Salinity Units (PSU) and sigma-t, respectively. The fluorometer was calibrated by discrete determinations of chlorophyll from Niskin bottle samples. The WetLABS AC9 measured the inherent optical properties of absorption (a) and attenuation (c) at nine wavelengths which closely match the satellite sensor bands: 412, 440, 488, 510, 560, 630, 650, 676 and 715nm. Attenuation is the sum of absorption and scattering (b), such that by measuring a and c, b may be obtained by difference. The meter uses two enclosed cuvettes to measure optical properties of pumped sample water over a 25cm path length: 1) the attenuation side is similar to a beam transmissometer utilizing a blackened cuvette and a well defined beam of light to measure the total loss of light from the beam over the path length and 2) the absorption side uses the 'shiny tube' approach and a diffuse light source which accounts for all internal reflections in a diffuse light field where absorption dominates scattering. Data were transmitted via hard wire in real-time and collected to a laptop computer and converted to standard coefficient units of m-1. These total absorption and attenuation coefficients reflect the influence of all optically active materials present in the water column.

Discrete water samples were collected at six depths throughout the water column using 5L Niskin bottles hung on the hydrographic wire immediately following the optics cast. Salinity samples for calibration of the CTD were collected from surface and deep bottles only. Sample volumes were collected for particulate and CDOM absorption, and chlorophyll determinations on-board, with additional volumes collected for total suspended solids, phytoplankton enumeration/identification and cell size spectra to be analyzed after the cruise. Total absorption can be further partitioned as the sum of the absorption due to water (which is a constant) plus optically active particulate matter plus dissolved colored organic matter (CDOM). We measured particulate and CDOM spectral absorption independently using a Baush and Lomb dual beam spectrophotometer between 350 and 750nm (1.6nm resolution), which also served as a check on the performance of the profiling instrument. Particulates from 100-1000ml were harvested on pre-weighed Whatman GFF glass fiber filters and placed upright in the dual beam spec with a blank wetted filter as a reference. Spectral absorption was scanned and stored in a computer as log base 10 measurements of optical density. Absorption coefficients (m-1) were calculated by converting optical density at each wavelength to natural log, multiplying by a beta factor which corrects for the increased path length due to scattering within the glass fiber filter and dividing by a factor relating the volume of sample filtered to the geometric path length. CDOM absorption was measured on 0.2 micron filtered seawater placed in 10cm cuvettes in the spectrophotometer. Similarly filtered Nanopure water was used in the reference cuvette. Optical density values as a function of wavelength were converted to natural log and multiplied by 10 to arrive at units of m-1. Chlorophyll a and phaeo-pigment concentrations were measured fluorometrically: replicate 100ml samples were filtered through Millipore HA 0.45micron filters and cold extracted for 24 hours prior to analysis. The Turner Model 111 fluorometer was calibrated using chlorophyll a from spinach (Sigma Chemical Co.).

Samples for total suspended solids were stored by placing the unfolded particulate absorption filters into plastic Petri slides (Millipore Corp.) in the freezer. At the lab, filters were dried and reweighed to determine total suspended solids concentration in mg/L. Samples for phytoplankton analyses were collected at selected depths (3 per station) and stored in two ways: 1) small raw sample volumes (3ml) under liquid nitrogen to preserve fluorescence for analysis by flow cytometry and 2) 100ml volumes with the addition of Lugol's iodine for microscopic analyses of settled samples. Flow cytometric analysis will be performed using a Becton-Dickinson FACScan cytometer which measures light scatter and fluorescence simultaneously from individual particles at rates to 1000 per second. Total particle counts are gated on chlorophyll fluorescence in order to obtain counts of phytoplankton, by knowing the volume of sample analyzed, concentrations per ml can be calculated. A size distribution curve is generated from the light scatter measurements for both total and chlorophyll containing groups. However, this data is ataxonomic, and cell populations must be identified by microscopic examination and counted by flow cytometry. Cell identification of larger cells will be performed on settled samples using a Zeiss inverted microscope, smaller cell sizes will be identified to the lowest taxon possible using a Zeiss Axiomat microscope. M. Keller of Bigelow Laboratory is responsible for the phytoplankton identification and enumeration work, flow cytometry will be performed in cooperation with the Jane J. MacIsaac Flow Cytometry Facility at Bigelow.

Spectral reflectance and water leaving radiance at the sea surface were measured in seven bands matched to the satellite sensors by a Satlantic TSRB II tethered surface reflectance buoy. The buoy was deployed for 15 minutes at each daytime station and measured downwelling incident surface irradiance above the sea surface and upwelling radiance just below the surface at 406, 412, 443, 490, 510, 555 and 670nm six times per second. Upwelling radiance in engineering units of mW nm-1 s-1 sr-1 were calculated from raw detector counts compared to a calibration file. Surface spectral reflectance was calculated by correcting the downwelling irradiance for immersion effects (reflection as a function of solar angle and refraction at the air/water interface) and propagating each waveband through the water to the depth of the upwelling sensor (0.7m). Reflectance was calculated as the ratio of upwelling to downwelling light at each wavelength.

Samples Collected

Stations 12

CTD/fluorometer casts 12

Wet salinities 24

AC-9 casts 12

TSRB II deployments 4

Chlorophylls 136

Particulate absorptions 68

CDOM absorptions 68

Total suspended solids 68

Phytoplankton ident/enum. 36

Preliminary Results

We were only able to reach the bottom of the seasonal thermocline at deep water (>150m) stations north of the bank and in Wilkinson Basin (stations 38 day and night, 34, 29 day, FB1, FB2 and WB1) with our 75m casts. Various mixed layer depths were found with evidence of the onset of autumnal erosion of the surface warmed layer. Shallow (<100m) stations south of the bank (3 and 9) displayed stepped physical structure indicative of convective cooling. Shallow stations at the eastern end and on top of Georges Bank (18, 20 and GB) were vertically homogeneous due to tidal mixing. TSRB buoy casts were obtained in each of these provinces. Water column optical properties were strongly dependent on particle distributions, the distribution of CDOM was nearly constant at low levels representative of oceanic conditions with little influence from freshwater sources. Particulate absorption curves were dominated by phytoplankton with little effects of suspended sediments, even on top of the bank. Chlorophyll concentrations varied by a factor of 10-12, with 60m samples at deep stations on the order of 0.5mg/m3 and sub-surface chlorophyll maximum samples >6.0mg/m3. Average surface concentrations were 3-4mg/m3. We are pleased with the variety of water masses sampled and the excellent assistance of the officers and crew of the R/V Albatross IV and Chief Scientist Jim Gibson.

CRUISE NARRATIVE

The cruise aboard ALBATROSS IV (ALB-9612) departed Woods Hole at 1600 on Monday, November 4, 1996. It was determined that there would not be a watch schedule for the scientific party. On station operations would begin with the AC-9, Niskin bottle cast, PNF light meter, Secchi disk, TSRB light buoy, followed by the CTD and MOCNESS. The light meters were only deployed when we arrived on station during the day light hours. The vessel arrived on station 38 at 0016 on Nov. 5. After the first few stations, an efficient routine of sampling operations was established for the duration of the cruise. Excellent weather conditions, minimal technical problems and help from the crew of the ALBATROSS IV throughout the entire cruise, allowed the scientific party to complete the survey ahead of schedule.

The MOC-1 stations occupied were Broadscale standard stations 38, 3, 9, 18, 20, 29, and 34 . Stations 29 and 38 were sampled twice for a night/day comparison. In order to obtain a night and day sample at Sta. 29, stations GB, FB1, and FB3 were added to allow a 12 hr interval between sampling. Station GB was selected inside the 60 m isobath to obtain productivity measurements on the Crest of Georges Bank. Stations FB1 and FB3 were selected to provide spatial information on zooplankton species composition and abundance in Franklin Basin. The second arrival at Station 38 occurred at 1220 on Nov. 7 which was ideal for the day-time sample.

At the completion of the station at Murray Basin (MB), sampling operations were terminated and the vessel steamed to Woods Hole, arriving at 0810 on Friday, Nov. 8.

Preliminary zooplankton results

In all stations observed, Centropages hamatus and typicus. were the dominant copepods. Centropages spp were found in all depth strata sampled, concentrations were greatest at the surface. Pseudocalanus spp. appeared in low abundance at stations 3, 9, 18 and 20. Calanus finmarchicus was abundant at station 34, 38 (Great South Channel), 29, Wilkinson Basin, and Murray Basin (Gulf of Maine).

Table 1:

This table shows our observations on the day/night samples collected at standard stations 38 and 29.

Net 1 = collected samples from bottom to 100m.

Net 4 = collected samples from the 15m to surface.

At Standard Stations 29, 34, 38, and WB, animals near the bottom were mostly C. finmarchicus C5's and C6 adult females. Within these concentrations, the C5 stage comprised 90% of the biomass. These animals had very large oil sacs, which indicates that they are in, or beginning diapause. Very few C. finmarchicus were found in the surface samples. Diurnal and nocturnal (or Vertical) migration of zooplankton was observed at stations 38 and 29 (see Table 1). Large predatory zooplankton (Shrimps, Euphausids, Amphipods, Ctenophores, Salps, and Siphonophores) were found in the depth strata from bottom to 100m, in the samples collected during the day. While in the samples collected at night, these predators were found in the top 15m. On the bank, Chaetognaths and Amphipods were the dominant predators. At Franklin Basin, Salps and other gelatinous plankton comprised most of the biomass. More accurate enumerations will be completed in the lab.

Table 2: Sampling operations and samples collected during cruise AL96-12

APPENDIX A

Scientific Party

Name Title Organization

James Gibson Chief Scientist URI/GSO, Narragansett, RI

Pilar Heredia Scientist URI/GSO, Narragansett, RI

Alyce Jacquet Scientist URI/GSO, Narragansett, RI

Dorothee Shreiber Scientist URI/GSO, Narragansett, RI

Lisa Graziano Scientist Bigelow Lab Oce. Sci. ME

David Drapeau Scientist Bigelow Lab Oce. Sci. ME

Suzanne Dunford Scientist Bigelow Lab Oce. Sci. ME

Bob Vallincourt Scientist Bigelow Lab Oce. Sci. ME

David Phinney Scientist Bigelow Lab Oce. Sci. ME

Jim Hopkins Scientist Bigelow Lab Oce. Sci. ME

Douglas Phinney Scientist Bigelow Lab Oce. Sci. ME

Jeff Brown Scientist Bigelow Lab Oce. Sci. ME

ALBATROSS IV NOAA Officers and Crew

Derek Sutton CO

Jason Maddox XO

Joel Michalski NAV

Kevin Cruse CME

John Hurder 1AE

Charles Hersey 2AE

Orlando Thompson EU

Royce Folks GVA

Kenny Rondeau CB

Willy Amaro SF

Tony Romao SF

Anthime Brunette F

Tony Alvernaz LF

Doug Roberts GVA

Richard Whitehead CS

Ernest Foster GVA

O.C. Hill GVA

Henry Jenkins RET

Neal Lynch NAV

APPENDIX B

Key to Instruments Used:

SG Shotgun surface sample

AC-9 9 channel spectral absorption/attenuation meter

Nskn-bottles Water collection with Niskin bottles

SeabirdCTD SBE Seabird profiler

MOC1 1 m² MOCNESS

PNF Biospherical Profiler for natural fluorescence

TSRB Tethered surface reflectance buoy

Secchi Secchi disk

The event log for AL96-12.

APPENDIX C

Hydrographic data from the SBE Seabird CTD cast prior to each MOC 1 tow.