Expected Datasets from the HLY-04-03 Process Cruise
1. Hydrographic Measurements Team: Lou Codispoti lead (on board); Jim Swift, lead PI
Other team members: Kristin Sanborn, Robert Palomares, Dan Schuller, Erik Quiroz
During this SBI process cruise we completed 60 stations and 184 CTD casts. The data have been edited and posted on the JOSS web site, and we have had time to plot data from our sections in Bering Strait and Barrow Canyon and the East Barrow line. Our observations include continuous vertical profiles of temperature, salinity, dissolved oxygen, fluorometric “chlorophyll”, light transmission, Haardt fluorescence (an index of terrestrial organic matter), and photosynthetically available radiation (PAR). Discrete water samples collected from our 30 liter rosette bottles have been analyzed for salinity, dissolved oxygen, ammonium, nitrate, nitrite, urea, phosphate, silicate, chlorophyll and phaeophytin concentrations, and members of the hydrographic team performed nutrient analyses for several of the experiments that were conducted.
The USCGC Healy has two independent Acoustic Doppler Current Profilers (ADCP) mounted in the hull of the ship: an Ocean Surveyor 75 kHz phased-array system (OS75) and a Broadband 153 kHz discrete-array system (BB153). Both systems were up and running, but the BB153 system was still being vetted to ascertain its data collection reliability. The OS75 is functioning in both broadband and narrowband mode. Both systems integrate acoustic data with the ship’s gyro, the aft P-code Trimble Centurion GPS and the Ashtech attitude GPS data. All data were collected onto local computers and then transferred to the networks archiving computer (snap1) and to a Mac PowerBook G4 for both systems.
Changes in comparison to the HLY04-02 spring cruise occurred in the form that the data was transferred automatically to the snap1 server with the program VVScheduler once a day instead of manually. The OS75 was also operated in dual-ping mode most of the cruise instead of just single-ping mode.
3. Chlorophyll: Lead PI, Dean Stockwell
Chlorophyll samples have been collected from 56 service casts and 28 productivity casts covering the 60 stations occupied. Six to ten depths per cast have been sampled and processed. In addition, samples have been processed from 1 bio-optical station and 14 samples have been analyzed for underway analysis (Sharon Smith) and 3 samples for Karl Kaiser.
4. Primary Production, Bio-optics, and Remote Sensing of Ocean Color:
David Ruble onboard lead; Victoria Hill and Xiaoju Pan: on-board team members
5. Carbon and nitrogen cycling group: Megan Roadman, Kyle Farmer (on-board team)
Dennis Hansell and Nick Bates, PIs
Type of samples: DIC, Total Alkalinity, DOC, POC/PON, Total Dissolved Nitrogen (TDN)
The samples collected include dissolved inorganic carbon (DIC), alkalinity (Alk) (as a water mass tracer), particulate organic carbon and nitrogen (POM), and dissolved organic carbon and nitrogen (DOM). We have sampled at every station, at various depths as shown in the table below. These samples are part of the complete suite of the carbon and nitrogen pools and are an essential contribution to the project as they relate to biogeochemical cycling, transport, and fluxes of carbon and nitrogen. The samples will be brought back to the lab for post-cruise analysis.
Dave Kadko, PI
During this cruise we collected 114 large volume (200L) water samples from the upper water column. Each sample has been filtered through manganese-coated fibers (which absorbs the radium), and analyzed for initial Radium-224 concentrations.
Transects sampled include: Bering Strait (2 surface samples), Harold Valley (2 samples from 2 shallow stations), Alaska Coastal Water (1 surface sample), Barrow Canyon (27 samples from 8 locations), East Barrow (30 samples from 8 locations), East Hanna Shoal (28 samples from 8 locations), and West Hanna Shoal (24 samples from 7 locations).
Also, twenty-two XCTDs were deployed between the 1000m and 3000m process stations on the EB line (12 XCTDs) and the EHS line (10 XCTDs). The XCTDs are used to improve the hydrographic data spacing and potentially help identify features (e.g. eddies and jets) not fully resolved by the major process stations that may be responsible for rapid transport of shelf water to the deep basin.
Dave Kirchman, PI
The microbiology group concluded the second half of the SBI Summer 2004 cruise having accomplished all research objectives. The main experimental work addressed the bacterial growth efficiency, which is an important factor in estimating the total bacterial carbon demand. Twelve bacterial growth efficiency experiments were completed over the course of the cruise and the average bacterial growth efficiency of 19%.
Roger Harvey, PI
We collected particulate organic carbon in vertical profiles throughout the water column along shelf to basin transects at 27 locations to examine community structure, quantify marine and terrestrial carbon sources, and evaluate particulate transport pathways. Additionally, we have collected sediments and POM from the Colville River, a major source of terrigenous material to this area of the Arctic Ocean. Box coring was attempted in the basin off the East Barrow and Barrow Canyon and East Hannah Shoal transect lines, and in shallow waters along the East Hannah Shoal line. Due to a variety of mechanical problems, cores in deep water were unsuccessful, although box coring in shallow water was completed without failure. Using the multi-corer, courtesy of John Christensen, we collected sediment cores from the deepest stations on the East and West Hannah Shoal transects. These cores complement our 2002 collection of sediments and are essential in evaluating both the sequestration of carbon in the Arctic Basin and variations in carbon sources over long time scales. We also obtained four large-volume particle samples from depths of 1000-1500m at stations 030, 037, 051, and 052 with the use of in-situ pumps from the Moran group, with help from Pat Kelly and Elly Speicher.
Ron Benner, PI
We have been able to coordinate much of our sampling with that of the bacterial production group and have collected O18 samples along with all DOM samples. In addition to these samples we collected samples from several experiments designed to follow the changes in these markers during the degradation of natural DOM.
In addition to these samples, we collected samples of dissolved and particulate matter during a sampling trip to the Colville River. These river samples will provide valuable information on the composition of terrestrially-derived material entering Alaska coastal waters.
The one disapointment is that our flash fluorometer which provides a measure of the chromophoric component of DOM stopped working early in the cruise.
1) Microzooplankton Grazing Experiments (dilution assays)
We completed 11 dilution assays during the summer 2004 cruise
2) Microzooplankton biomass and analysis of phytoplankton community composition: Samples were collected at the 6 depths of the primary production assays for 25 of the primary production casts during the summer cruise. Three types of samples were collected: for flow cytometric analysis of phytoplankton and heterotrophic bacteria, for epifluorescence microscopy, and for inverted microscopy (Lugol fixed samples).
3) Mesozooplankton grazing experiments: We have sampled the Time 0 and Time Final bottles for the 11 mesozooplankton grazing assays carried out during on the cruise. These samples will be analysed for change in protist abundance and biomass to evaluate the grazing rate of microzooplankton on heterotrophic protists.
11. Exchange of Plankton and Particles between the Shelf and Basin: Carin Ashjian (PI) and Philip Alatalo, on-board team members; Scott Gallager (PI) and Mark Benfield (PI)
The purpose of this project is to document shelf-basin exchange of plankton and particles. The project is composed of two components: shipboard estimates of plankton and particle abundance from a Video Plankton Recorder during the two process cruises and long-term observations of particle/plankton abundance from moored acoustic Doppler current profilers. Only the first component is conducted on the present cruise.
12. Mesozooplankton Process Studies: Carin Ashjian, and Bob Campbell (On-board PIs), Philip Alatalo
The purpose of this project is to determine the grazing rates of the dominant copepod species/life stages on phytoplankton and microzooplankton food at locations both on the shelf and in the basin. The ultimate goal is to couple these measurements with estimates of total abundance and food availability to describe the role of mesozooplankton in processing carbon (both primary production and microzooplankton) in the two regions. The relative condition of the plankton populations in the two regions also is assessed through measures of carbon and nitrogen content (CN), RNA/DNA (an indicator of metabolic activity), and, for actively reproducing species, egg production rates (EPR).
A total of 11 grazing and 23 egg production experiments for the dominant species at each location have been carried out (see table below for experimental and sample inventories).
13. Zooplankton Distribution and Abundance: Sharon Smith (On-board PI)
Other Team Members, Peter Lane, Alex Osuna and Leopoldo Llinás
Quantify abundances and depth-stratified distributions of pelagic zooplankton over the shelf, slope and basin of the Chukchi and Beaufort seas
Quantify distribution of copepod nauplii at the surface in the study area using molecular techniques
Quantify egg production by dominant copepods in the study area
Table of Data Collected.
Vertical Bongo Tows: 5
MultiNet® Tows: 32
Surface Map Samples: 691
14. Carbon and nitrogen isotope dynamics: Susan Schonberg and Craig Aumack (On-board team)
Ken Dunton, PI
Carbon and nitrogen isotope signatures can provide information about the trophic links between pelagic and benthic components of the shelf and slope.
Our objective is to collect biological material from four trophic levels on the Arctic shelf and ocean basin to determine the natural abundance of d13C and d15N.
The dried samples will be taken back and analyzed using a mass spectrometer at The University of Texas Marine Science Institute upon return from the expedition.
15. Water/sediment tracers, sediment metabolism and benthic community structure; Jackie Grebmeier and Lee Cooper (on-board PIs) Other team members: Arianne Balsom. Catherine Lalande, Rebecca Pirtle-Levy
Sixty stations were occupied during HLY-04-03 for various data collections within our component, both water and sediment samples (Table 1). Water from all depths on the hydrographic CTD casts were collected for O-18 measurements, in addition to collections from other selected casts, particularly those made for biomarkers. These mass spectrometric analyses will be accomplished following the cruise in Tennessee. A sub-sample of water from the surface and chlorophyll max was collected by Dean Stockwell (service cast) and Victoria Hill (productivity cast) and preserved in Lugol’s solution for phytoplankton identification by Dr. Mickle Flint of the Shirshov Institute of Oceanology in Russia as part of our core project. Bottom water was collected from the service CTD for sediment respiration experiments.
Sediments were collected at 27 of these stations using both a 0.1m2 van Veen grab (all27 stations) and a 0.0133 m2 HAPS benthic corer (22 of the benthic stations). Four van Veen grabs were used up to a 500 m depth interval to collect replicate quantitative samples for benthic population studies. Sediment was sieved through 1 mm screens and retained animals preserved in 10% buffered formalin for analysis on land. A separate study by M.S. student Rebecca Pirtle-Levy is investigating the 0.5 mm fraction from these cores. Cores used from respiration experiments were sieved through a 1mm mesh with a 0.5mm mesh screen inserted to catch the smaller size fraction of animals. These samples will be analyzed at the University of Tennessee to determine the extent of biases associated with use of the 1 mm versus 0.5 mm screens.
Sediment collections from both the van Veen and multiple-HAPS corer are being analyzed for chlorophyll pigment content (both fluorometric and HPLC), total organic carbon and nitrogen content, grain size, and various radioisotopes, particularly Be-7, which is being used a tracer for transport of sea ice rafted materials to the sea floor. Surface sediments were collected in whirl pack bags and frozen. Large volume surface sediments were also collected in Marinelli beakers for gamma counting. In addition to sediments collected for our component, we provided sediment to Brad Moran for Th-232 and Pb-210 measurements.
Two additional HAPS cores were collected at each station for sediment metabolism experiment. Overlying water was replaced with bottom water and flux rates determined for oxygen, carbon dioxide and nutrients over a 12-24 hr period at in situ bottom water temperatures (-1.6 to 1 deg.C). In addition, dissolved organic carbon (DOC) flux measurements were made in these cores in collaboration with Ron Benner. Once the experiment is completed, cores were sieved to retain the benthic organisms, which were preserved as outlined above.
Finally, we deployed on an opportunistic basis floating sediment traps for studies of particle export. Unlike in the spring, when it was relatively easy to deploy the traps from ice floe anchors, we had to deploy the traps directly into the ocean and this has proven to be more risky, as we anticipated. The traps were successfully deployed at six stations during the cruise, but one set of traps was lost during a third attempted deployment, probably as a result of ice knocking over the radio locator beacon mounted on a pole attached to the system. Adequate spare equipment was brought onboard for us to continue sampling as opportunities become available. Samples for POC/PON, chlorophyll a, phytoplankton, zooplankton fecal pellets, 234Th, 7Be and d13C were taken at the depths of 30, 40, 50, 60 and 100m. These measurements will give an estimation of the vertical export fluxes of organic matter and will be compared with the fluxes measured by the 234Th pumping (University of Rhode Island).
A fecal pellet production experiment was undertaken for every station where sediment traps were deployed. The estimation of the production rate at each station and the amount of fecal pellets caught in the sediment traps will allow the estimation of the percentage of fecal pellets sinking in the water column.
16. Benthic Denitrification: Allan Devol and John Christensen (On-board PI) Melanie Lettau, team member
Using an Ocean Instrument’s multiple corer, sediment cores were collected at 17 sites ranging in water depths from 50 to 3700 m. The sediments captured in these cores have been between 20 and 50 cm in depth with clear overlying water, indicating minimal disturbance of the sediments during coring. Cores have been incubated for 1 to 5 days (depending on the magnitude of the fluxes) in incubation chambers sealed from the atmosphere. Samples are withdrawn periodically from the water overlying each core for measurement of the key gases, nutrients and metabolites. We are using a gas chromatograph coupled to quadrapole mass spectrometer to determine the ratio of nitrogen gas to argon and the ratio of oxygen gas to argon. The flux samples showed consistent changes in these ratios with increasing incubation time, so that we will be able to calculate sedimentary oxygen consumption and denitrification. Fluxes of total CO2 out of the sediments were measurable at all sites that were attempted. Thus total carbon oxidation rates from these cores will be evaluated. Silicate fluxes out of the sediments were measured on board and the other dissolved nutrients will be measured when samples are returned to Bigelow Laboratory.
17. Particle-reactive radionuclides: Pat Kelly, Elly Speicher, and Stephen Schmidt, onboard investigators
1) Quantify the flux of particulate organic carbon (POC) from the surface water to the deep waters of the Chuckchi Sea using 234Th as a tracer of particle export.
2) Determine POC/234Th ratio values for multiple size fractions of particles, and different types of particles at specific depths
3) Compare 234Th-tracer derived POC fluxes w/ sediment trap derived fluxes of POC.
4) Compare 234Th export from surface water with 234Th accumulation in sediments.
5) Improve 234Th sample resolution from HLY-02-0X using newly developed small volume technique.